Processes

13 pages, 2505 KiB

Open AccessEditor’s ChoiceArticle

Smart Determination of Gold Content in PCBs of Waste Mobile Phones by Coupling of XRF and AAS Techniques

by Nicolò Maria Ippolito, Gianmaria Belardi, Valentina Innocenzi, Franco Medici, Loris Pietrelli and Luigi Piga

Processes 2021, 9(9), 1618; https://doi.org/10.3390/pr9091618 - 8 Sep 2021

Cited by 2 | Viewed by 2532

Abstract

Quantitative determination of most economic valuable metals in waste is the first fundamental operation of evaluating the feasibility of recycling processes. Field-portable X-ray fluorescence spectrometers (FPXRFs) represent a more practical, efficient, and economic tool in determining the elemental composition of samples with respect [...] Read more.

Quantitative determination of most economic valuable metals in waste is the first fundamental operation of evaluating the feasibility of recycling processes. Field-portable X-ray fluorescence spectrometers (FPXRFs) represent a more practical, efficient, and economic tool in determining the elemental composition of samples with respect to conventional analytical techniques, such as atomic absorption spectrometry (AAS) and inductively coupled plasma emission spectrometry (ICP). In this paper, quick and smart determination of gold content in printed circuit boards (PCBs) of waste mobile phones was studied. The aim of the research was to combine the practicality of FPXRFs with the reliability of quantitative spectrometry analysis and evaluate the error between the two techniques. Several samples (33) of PCBs were ground to a size below 0.5 mm, and then, the powders were analyzed by FPXRFs at different acquisition times with five replications for each sample. The same analyzed samples then underwent chemical attack to determine the quantitative gold content by AAS. The obtained results were associated with FPXRFs response with the purpose of realizing a calibration curve (100–1000 mg/kg Au). The curve was validated for accuracy and precision by other PCBs waste samples; the control samples were added as standards to obtain a more reliable calibration curve. The curve was evaluated with RPD classification, regression linear, and Bolt–Altman analysis. Full article

(This article belongs to the Section Environmental and Green Processes)

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24 pages, 4946 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Evaluation of a Combined MHE-NMPC Approach to Handle Plant-Model Mismatch in a Rotary Tablet Press

by Yan-Shu Huang, M. Ziyan Sheriff, Sunidhi Bachawala, Marcial Gonzalez, Zoltan K. Nagy and Gintaras V. Reklaitis

Processes 2021, 9(9), 1612; https://doi.org/10.3390/pr9091612 - 8 Sep 2021

Cited by 14 | Viewed by 2727

Abstract

The transition from batch to continuous processes in the pharmaceutical industry has been driven by the potential improvement in process controllability, product quality homogeneity, and reduction of material inventory. A quality-by-control (QbC) approach has been implemented in a variety of pharmaceutical product manufacturing [...] Read more.

The transition from batch to continuous processes in the pharmaceutical industry has been driven by the potential improvement in process controllability, product quality homogeneity, and reduction of material inventory. A quality-by-control (QbC) approach has been implemented in a variety of pharmaceutical product manufacturing modalities to increase product quality through a three-level hierarchical control structure. In the implementation of the QbC approach it is common practice to simplify control algorithms by utilizing linearized models with constant model parameters. Nonlinear model predictive control (NMPC) can effectively deliver control functionality for highly sensitive variations and nonlinear multiple-input-multiple-output (MIMO) systems, which is essential for the highly regulated pharmaceutical manufacturing industry. This work focuses on developing and implementing NMPC in continuous manufacturing of solid dosage forms. To mitigate control degradation caused by plant-model mismatch, careful monitoring and continuous improvement strategies are studied. When moving horizon estimation (MHE) is integrated with NMPC, historical data in the past time window together with real-time data from the sensor network enable state estimation and accurate tracking of the highly sensitive model parameters. The adaptive model used in the NMPC strategy can compensate for process uncertainties, further reducing plant-model mismatch effects. The nonlinear mechanistic model used in both MHE and NMPC can predict the essential but complex powder properties and provide physical interpretation of abnormal events. The adaptive NMPC implementation and its real-time control performance analysis and practical applicability are demonstrated through a series of illustrative examples that highlight the effectiveness of the proposed approach for different scenarios of plant-model mismatch, while also incorporating glidant effects. Full article

(This article belongs to the Special Issue Expanding the Horizons of Manufacturing: Towards Wide Integration, Smart Systems and Tools)

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22 pages, 3564 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Advanced Process Analytical Technology in Combination with Process Modeling for Endpoint and Model Parameter Determination in Lyophilization Process Design and Optimization

by Alex Juckers, Petra Knerr, Frank Harms and Jochen Strube

Processes 2021, 9(9), 1600; https://doi.org/10.3390/pr9091600 - 7 Sep 2021

Cited by 11 | Viewed by 3399

Abstract

Lyophilization is widely used in the preservation of thermolabile products. The main shortcoming is the long processing time. Lyophilization processes are mostly based on a recipe that is not changed, but, with the Quality by Design (QbD) approach and use of Process Analytical [...] Read more.

Lyophilization is widely used in the preservation of thermolabile products. The main shortcoming is the long processing time. Lyophilization processes are mostly based on a recipe that is not changed, but, with the Quality by Design (QbD) approach and use of Process Analytical Technology (PAT), the process duration can be optimized for maximum productivity while ensuring product safety. In this work, an advanced PAT approach is used for the endpoint determination of primary drying. Manometric temperature measurement (MTM) and comparative pressure measurement are used to determine the endpoint of the batch while a modeling approach is outlined that is able to calculate the endpoint of every vial in the batch. This approach can be used for process development, control and optimization. Full article

(This article belongs to the Special Issue Towards Autonomous Operation of Biologics and Botanicals)

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12 pages, 2153 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Comparison of Two Extraction Procedures, SPE and DLLME, for Determining Plasticizer Residues in Hot Drinks at Vending Machines

by Ivan Notardonato, Sergio Passarella, Alessia Iannone, Cristina Di Fiore, Mario Vincenzo Russo, Carmela Protano, Matteo Vitali and Pasquale Avino

Processes 2021, 9(9), 1588; https://doi.org/10.3390/pr9091588 - 5 Sep 2021

Cited by 8 | Viewed by 2778

Abstract

This paper would like to compare two extraction procedures for analyzing phthalates (PAEs) in hot drinks collected at vending machines, usually coffee and tea. The two analytical procedures are based on Solid Phase Extraction (SPE) using C18 cartridge and on dispersive liquid-liquid microextraction [...] Read more.

This paper would like to compare two extraction procedures for analyzing phthalates (PAEs) in hot drinks collected at vending machines, usually coffee and tea. The two analytical procedures are based on Solid Phase Extraction (SPE) using C18 cartridge and on dispersive liquid-liquid microextraction (DLLME) assisted by ultrasound and vortex for improving the dispersion mechanically, with each followed by a routinary analytical method such as GC-FID. Seven phthalates (DMP, DEP, DiBP, DBP, DEHP, DOP, DDP) have been analyzed and determined. All the analytical parameters (i.e., recovery, limit of detection, limit of quantification, enrichment factors, repeatability, reproducibility) have been investigated and discussed, as has the matrix effect. The entire procedure has been applied to hot drink matrices, e.g., coffee, decaffeinated coffee, barley coffee, ginseng coffee and tea. Full article

(This article belongs to the Special Issue Applications of Chromatographic Separation Techniques in Food and Chemistry)

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11 pages, 979 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Overview of the Benefits and Challenges Associated with Pelletizing Biochar

by Ali Mohammadi

Processes 2021, 9(9), 1591; https://doi.org/10.3390/pr9091591 - 5 Sep 2021

Cited by 17 | Viewed by 6164

Abstract

Biochar can be derived from a wide variety of organic materials including agricultural wastes and residues, animal wastes, municipal solid wastes, pulp and paper mill wastes, and sewage sludge. Its productivity relies on feedstock type and thermochemical conditions of production. Biochar has many [...] Read more.

Biochar can be derived from a wide variety of organic materials including agricultural wastes and residues, animal wastes, municipal solid wastes, pulp and paper mill wastes, and sewage sludge. Its productivity relies on feedstock type and thermochemical conditions of production. Biochar has many application advantages in several fields and has been widely studied in recent years. However, most of these studies are mainly on the powder form of biochar, while its pelleted form is sparsely reported. Even with the reported studies on biochar pellets, there is still lack of knowledge and awareness of the effects of different feedstock on the densification behavior of biochar. The mechanisms of biochar densification, which appear to be sensitive to the conditions predominating during its thermochemical production, are affected by the material from which the biochar is derived. This partly accounts for why biochar pellets have not been widely adopted in various application fields. Therefore, this paper presents an overview of the benefits associated with the use of biochar pellets and discusses the challenges encountered when pelleting biochars that are derived from different feedstock under various carbonization conditions. Research priority areas needed to overcome the challenges are also identified and discussed. The purpose is to contribute to better understanding on biochar pelletization behavior, and to offer insights useful to comprehend some basic principles that may occur in the pelleting process and to ease further and more thorough investigations. Full article

(This article belongs to the Section Environmental and Green Processes)

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15 pages, 1483 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Counter-Current Suspension Extraction Process of Lignocellulose in Biorefineries to Reach Low Water Consumption, High Extraction Yields, and Extract Concentrations

by Marc Conrad and Irina Smirnova

Processes 2021, 9(9), 1585; https://doi.org/10.3390/pr9091585 - 4 Sep 2021

Cited by 2 | Viewed by 2833

Abstract

The processing of large quantities of water in biorefining processes can lead to immense costs for heating, evaporation, and wastewater disposal. These costs may prohibit the exploitation of alternative products, e.g., xylooligosaccharides from straw, which are regarded as too costly. A new counter-current [...] Read more.

The processing of large quantities of water in biorefining processes can lead to immense costs for heating, evaporation, and wastewater disposal. These costs may prohibit the exploitation of alternative products, e.g., xylooligosaccharides from straw, which are regarded as too costly. A new counter-current extractions method is proposed that aims at low solvent (water) consumption, as well as high yields and extract concentrations. This process was evaluated with suspension extraction experiments with steam pretreated wheat straw and the process window analysis based on a mass balance for a washing and a leaching scenario. The latter was conducted with two other suspension extraction processes as a comparison. The equilibration time was found to be well below 10 min. While the suspension extraction with and without recycling need to be designed to achieve a high yield or a high concentration and low solvent consumption, the proposed extraction method can reach all three simultaneously. Thus, this new process is evaluated as a potential method to spare water and downstream costs and allow new processing pathways in second-generation biorefineries. Full article

(This article belongs to the Special Issue Recent Advances in Biorefining Processes)

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16 pages, 3446 KiB

Open AccessEditor’s ChoiceArticle

Conjugated Mass Transfer of CO₂ Absorption through Concentric Circular Gas–Liquid Membrane Contactors

by Chii-Dong Ho, Hsuan Chang, Yih-Hang Chen, Jun-Wei Lim and Jing-Wei Liou

Processes 2021, 9(9), 1580; https://doi.org/10.3390/pr9091580 - 3 Sep 2021

Cited by 2 | Viewed by 1693

Abstract

A new design of gas absorption that winds the permeable membrane onto an inner concentric tube to conduct a concentric circular gas–liquid membrane module has been studied theoretically in the fully developed region. An analytical formulation, referred to as conjugated Graetz problems, is [...] Read more.

A new design of gas absorption that winds the permeable membrane onto an inner concentric tube to conduct a concentric circular gas–liquid membrane module has been studied theoretically in the fully developed region. An analytical formulation, referred to as conjugated Graetz problems, is developed to predict the concentration distribution and Sherwood numbers for the absorbent fluid flowing in the shell side and CO₂/N₂ gas mixture flowing in the tube side under various designs and operating parameters. The analytical solutions to the CO₂ absorption efficiency were developed by using a two-dimensional mathematical modeling, and the resultant conjugated partial differential equations were solved analytically using the method of separation variables and eigen-function expansion in terms of power series. The predictions of CO₂ absorption rate by using Monoethanolamide (MEA) solution in concentric circular membrane contactors under both concurrent- and countercurrent-flow operations are developed theoretically and confirmed with the experimental results. Consistency in both a good qualitative and quantitative sense is achieved between the theoretical predictions and experimental results. The advantage of the present mathematical treatment provides a concise expression for the chemical absorption of CO₂ by MEA solution to calculate the absorption rate, absorption efficiency, and average Sherwood number. The concentration profiles with the mass-transfer Graetz number, inlet CO₂ concentration, and both gas feed and absorbent flow rates are also emphasized. Both theoretical predictions and experimental results show that the device performance of the countercurrent-flow operation is better than that of the concurrent-flow device operation. The availability of such simplified expressions of the absorption rate and averaged Sherwood as developed directly from the analytical solutions is the value of the present study. Full article

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21 pages, 15858 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Formation Control of Swarming Vessels Using a Virtual Matrix Approach and ISOT Guidance Algorithm

by Su-Rim Kim, Hyun-Jae Jo, Jung-Hyeon Kim and Jong-Yong Park

Processes 2021, 9(9), 1581; https://doi.org/10.3390/pr9091581 - 3 Sep 2021

Cited by 3 | Viewed by 2238

Abstract

The formation control for the effective operation of multiple vessels is discussed. First, a virtual matrix approach is proposed to improve the formation robustness and transform performance during swarm operations, which is created based on the virtual leader vessel location, and agents composing [...] Read more.

The formation control for the effective operation of multiple vessels is discussed. First, a virtual matrix approach is proposed to improve the formation robustness and transform performance during swarm operations, which is created based on the virtual leader vessel location, and agents composing the formation follow cells in the matrix to maintain formation. This approach is affected by the virtual leader vessel location. The virtual leader vessel location is defined by two cases: matrix center and geometric center; furthermore, robustness and efficiency comparison simulations are performed. The simulation results show that in most formations, the geometric center is better in terms of efficiency and robustness. Second, the isosceles triangle guidance algorithm is proposed to improve the “go-back behavior” of certain agents during excessive maneuvering. Through a waypoint-following simulation, the algorithm is confirmed to be superior to the line-of-sight guidance algorithm. The swarm simulation on the virtual map verifies the performance of the proposed formation control and guidance algorithm. Full article

(This article belongs to the Special Issue Theoretical and Numerical Marine Hydrodynamics)

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18 pages, 886 KiB

Open AccessFeature PaperEditor’s ChoiceReview

How to Tackle Underdeterminacy in Metabolic Flux Analysis? A Tutorial and Critical Review

by Philippe Bogaerts and Alain Vande Wouwer

Processes 2021, 9(9), 1577; https://doi.org/10.3390/pr9091577 - 2 Sep 2021

Cited by 3 | Viewed by 2913

Abstract

Metabolic flux analysis is often (not to say almost always) faced with system underdeterminacy. Indeed, the linear algebraic system formed by the steady-state mass balance equations around the intracellular metabolites and the equality constraints related to the measurements of extracellular fluxes do not [...] Read more.

Metabolic flux analysis is often (not to say almost always) faced with system underdeterminacy. Indeed, the linear algebraic system formed by the steady-state mass balance equations around the intracellular metabolites and the equality constraints related to the measurements of extracellular fluxes do not define a unique solution for the distribution of intracellular fluxes, but instead a set of solutions belonging to a convex polytope. Various methods have been proposed to tackle this underdeterminacy, including flux pathway analysis, flux balance analysis, flux variability analysis and sampling. These approaches are reviewed in this article and a toy example supports the discussion with illustrative numerical results. Full article

(This article belongs to the Special Issue Mathematical Modeling and Control of Bioprocesses)

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67 pages, 6075 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Computational Fluid Dynamics Modelling of Liquid–Solid Slurry Flows in Pipelines: State-of-the-Art and Future Perspectives

by Gianandrea Vittorio Messa, Qi Yang, Oluwaseun Ezekiel Adedeji, Zdeněk Chára, Carlos Antonio Ribeiro Duarte, Václav Matoušek, Maria Graça Rasteiro, R. Sean Sanders, Rui C. Silva and Francisco José de Souza

Processes 2021, 9(9), 1566; https://doi.org/10.3390/pr9091566 - 1 Sep 2021

Cited by 38 | Viewed by 10076

Abstract

Slurry pipe transport has directed the efforts of researchers for decades, not only for the practical impact of this problem, but also for the challenges in understanding and modelling the complex phenomena involved. The increase in computer power and the diffusion of multipurpose [...] Read more.

Slurry pipe transport has directed the efforts of researchers for decades, not only for the practical impact of this problem, but also for the challenges in understanding and modelling the complex phenomena involved. The increase in computer power and the diffusion of multipurpose codes based on Computational Fluid Dynamics (CFD) have opened up the opportunity to gather information on slurry pipe flows at the local level, in contrast with the traditional approaches of simplified theoretical modelling which are mainly based on a macroscopic description of the flow. This review paper discusses the potential of CFD for simulating slurry pipe flows. A comprehensive description of the modelling methods will be presented, followed by an overview of significant publications on the topic. However, the main focus will be the assessment of the potential and the challenges of the CFD approach, underlying the essential interplay between CFD simulations and experiments, discussing the main sources of uncertainty of CFD models, and evaluating existing models based on their interpretative or predictive capacity. This work aims at providing a solid ground for students, academics, and professional engineers dealing with slurry pipe transport, but it will also provide a methodological approach that goes beyond the specific application. Full article

(This article belongs to the Section Process Control and Monitoring)

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15 pages, 1611 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Gas to Liquids Techno-Economics of Associated Natural Gas, Bio Gas, and Landfill Gas

by Federico Galli, Jun-Jie Lai, Jacopo De Tommaso, Gianluca Pauletto and Gregory S. Patience

Processes 2021, 9(9), 1568; https://doi.org/10.3390/pr9091568 - 1 Sep 2021

Cited by 13 | Viewed by 4138

Abstract

Methane is the second highest contributor to the greenhouse effect. Its global warming potential is 37 times that of CO₂. Flaring-associated natural gas from remote oil reservoirs is currently the only economical alternative. Gas-to-liquid (GtL) technologies first convert natural gas into [...] Read more.

Methane is the second highest contributor to the greenhouse effect. Its global warming potential is 37 times that of CO₂. Flaring-associated natural gas from remote oil reservoirs is currently the only economical alternative. Gas-to-liquid (GtL) technologies first convert natural gas into syngas, then it into liquids such as methanol, Fischer–Tropsch fuels or dimethyl ether. However, studies on the influence of feedstock composition are sparse, which also poses technical design challenges. Here, we examine the techno-economic analysis of a micro-refinery unit (MRU) that partially oxidizes methane-rich feedstocks and polymerizes the syngas formed via Fischer–Tropsch reaction. We consider three methane-containing waste gases: natural gas, biogas, and landfill gas. The FT fuel selling price is critical for the economy of the unit. A Monte Carlo simulation assesses the influence of the composition on the final product quantity as well as on the capital and operative expenses. The Aspen Plus simulation and Python calculate the net present value and payback time of the MRU for different price scenarios. The CO₂ content in biogas and landfill gas limit the CO/H₂ ratio to 1.3 and 0.9, respectively, which increases the olefins content of the final product. Compressors are the main source of capital cost while the labor cost represents 20–25% of the variable cost. An analysis of the impact of the plant dimension demonstrated that the higher number represents a favorable business model for this unit. A minimal production of 7,300,000 kg y

^{- 1}

is required for MRU to have a positive net present value after 10 years when natural gas is the feedstock. Full article

(This article belongs to the Special Issue Innovation in Chemical Plant Design)

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15 pages, 1509 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Modeling of Continuous PHA Production by a Hybrid Approach Based on First Principles and Machine Learning

by Martin F. Luna, Andrea M. Ochsner, Véronique Amstutz, Damian von Blarer, Michael Sokolov, Paolo Arosio and Manfred Zinn

Processes 2021, 9(9), 1560; https://doi.org/10.3390/pr9091560 - 1 Sep 2021

Cited by 17 | Viewed by 3992

Abstract

Polyhydroxyalkanoates (PHA) are renewable alternatives to traditional oil-derived polymers. PHA can be produced by different microorganisms in continuous culture under specific media composition, which makes the production process both promising and challenging. In order to achieve large productivities while maintaining high yield and [...] Read more.

Polyhydroxyalkanoates (PHA) are renewable alternatives to traditional oil-derived polymers. PHA can be produced by different microorganisms in continuous culture under specific media composition, which makes the production process both promising and challenging. In order to achieve large productivities while maintaining high yield and efficiency, the continuous culture needs to be operated in the so-called dual nutrient limitation condition, where both the nitrogen and carbon sources are kept at very low concentrations. Mathematical models can greatly assist both design and operation of the bioprocess, but are challenged by the complexity of the system, in particular by the dual nutrient-limited growth phenomenon, where the cells undergo a metabolic shift that abruptly changes their behavior. Traditional, non-structured mechanistic models based on Monod uptake kinetics can be used to describe the bioreactor operation under specific process conditions. However, in the absence of a model description of the metabolic phenomena inside the cell, the extrapolation to a broader operation domain (e.g., different feeding concentrations and dilution rates) may present mismatches between the predictions and the actual process outcomes. Such detailed models may require almost perfect knowledge of the cell metabolism and omic-level measurements, hampering their development. On the other hand, purely data-driven models that learn correlations from experimental data do not require any prior knowledge of the process and are therefore unbiased and flexible. However, many more data are required for their development and their extrapolation ability is limited to conditions that are similar to the ones used for training. An attractive alternative is the combination of the extrapolation power of first principles knowledge with the flexibility of machine learning methods. This approach results in a hybrid model for the growth and uptake rates that can be used to predict the dynamic operation of the bioreactor. Here we develop a hybrid model to describe the continuous production of PHA by Pseudomonas putida GPo1 culture. After training, the model with experimental data gained under different dilution rates and medium compositions, we demonstrate how the model can describe the process in a wide range of operating conditions, including both single and dual nutrient-limited growth. Full article

(This article belongs to the Special Issue Advanced Modeling of Biomanufacturing Processes)

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31 pages, 4843 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Estimating the Methane Potential of Energy Crops: An Overview on Types of Data Sources and Their Limitations

by Yue Zhang, Sigrid Kusch-Brandt, Andrew M. Salter and Sonia Heaven

Processes 2021, 9(9), 1565; https://doi.org/10.3390/pr9091565 - 1 Sep 2021

Cited by 12 | Viewed by 5546

Abstract

As the anaerobic digestion of energy crops and crop residues becomes more widely applied for bioenergy production, planners and operators of biogas plants, and farmers who consider growing such crops, have a need for information on potential biogas and methane yields. A rich [...] Read more.

As the anaerobic digestion of energy crops and crop residues becomes more widely applied for bioenergy production, planners and operators of biogas plants, and farmers who consider growing such crops, have a need for information on potential biogas and methane yields. A rich body of literature reports methane yields for a variety of such materials. These data have been obtained with different testing methods. This work elaborates an overview on the types of data source available and the methods that are commonly applied to determine the methane yield of an agricultural biomass, with a focus on European crops. Limitations regarding the transferability and generalisation of data are explored, and crop methane values presented across the literature are compared. Large variations were found for reported values, which can only partially be explained by the methods applied. Most notably, the intra-crop variation of methane yield (reported values for a single crop type) was higher than the inter-crop variation (variation between different crops). The pronounced differences in reported methane yields indicate that relying on results from individual assays of candidate materials is a high-risk approach for planning biogas operations, and the ranges of values such as those presented here are essential to provide a robust basis for estimation. Full article

(This article belongs to the Special Issue New Frontiers in Anaerobic Digestion (AD) Processes)

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15 pages, 5510 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Towards the Circular Economy of Rare Earth Elements: Lanthanum Leaching from Spent FCC Catalyst by Acids

by Corradino Sposato, Enrico Catizzone, Alessandro Blasi, Marilena Forte, Assunta Romanelli, Massimo Morgana, Giacobbe Braccio, Girolamo Giordano and Massimo Migliori

Processes 2021, 9(8), 1369; https://doi.org/10.3390/pr9081369 - 5 Aug 2021

Cited by 8 | Viewed by 3995

Abstract

Rare earth elements (REEs) are strategic materials widely used in different applications from Information and Communication Technologies (ICT) to catalysis, which are expected to grow more in the future. In order to reduce the impact of market price and reduce the environmental effect [...] Read more.

Rare earth elements (REEs) are strategic materials widely used in different applications from Information and Communication Technologies (ICT) to catalysis, which are expected to grow more in the future. In order to reduce the impact of market price and reduce the environmental effect from soil extraction, recovery/purification strategies should be exploited. This paper presents a combined acid-leaching/oxalate precipitation process to recover lanthanum from spent FCC catalyst using nitric acid. Preferred to hydrochloric and sulphuric acid (preliminary assessed), HNO₃ showed a good capability to completely leach lanthanum. The combination with an oxalate precipitation step allowed demonstrating that a highly pure (>98% w/w) lanthanum solid can be recovered, with a neglectable amount of poisoning metals (Ni, V) contained into the spent catalyst. This could open a reliable industrial perspective to recover and purify REE in the view of a sustainable recycling strategy. Full article

(This article belongs to the Special Issue Treatment and Utilization of Waste Materials)

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15 pages, 2880 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Exploring Electrochemically Mediated ATRP of Styrene

by Francesco De Bon, Gian Marco Carlan, Enrico Tognella and Abdirisak Ahmed Isse

Processes 2021, 9(8), 1327; https://doi.org/10.3390/pr9081327 - 30 Jul 2021

Cited by 5 | Viewed by 2454

Abstract

Electrochemically mediated atom transfer radical polymerization (eATRP) of styrene was studied in detail by using CuBr₂/TPMA (TPMA = tris(2-pyridylmethyl)amine) as a catalyst. Redox properties of various Cu(II) species were investigated in CH₃CN, dimethylformamide (DMF), and dimethyl sulfoxide [...] Read more.

Electrochemically mediated atom transfer radical polymerization (eATRP) of styrene was studied in detail by using CuBr₂/TPMA (TPMA = tris(2-pyridylmethyl)amine) as a catalyst. Redox properties of various Cu(II) species were investigated in CH₃CN, dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) both in the absence and presence of 50% (v/v) styrene. This investigation together with preliminary eATRP experiments at 80 °C indicated DMF as the best solvent. The effects of catalyst, monomer, and initiator concentrations were also examined. The livingness of the polymerization was studied by chain extension and electrochemical temporal control of polymerization. Full article

(This article belongs to the Special Issue Engineering Reversible Deactivation Radical Polymerization in the Second Century of Macromolecular Science)

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16 pages, 2239 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

IP Analytics and Machine Learning Applied to Create Process Visualization Graphs for Chemical Utility Patents

by Amy J. C. Trappey, Charles V. Trappey, Chih-Ping Liang and Hsin-Jung Lin

Processes 2021, 9(8), 1342; https://doi.org/10.3390/pr9081342 - 30 Jul 2021

Cited by 4 | Viewed by 3586

Abstract

Researchers must read and understand a large volume of technical papers, including patent documents, to fully grasp the state-of-the-art technological progress in a given domain. Chemical research is particularly challenging with the fast growth of newly registered utility patents (also known as intellectual [...] Read more.

Researchers must read and understand a large volume of technical papers, including patent documents, to fully grasp the state-of-the-art technological progress in a given domain. Chemical research is particularly challenging with the fast growth of newly registered utility patents (also known as intellectual property or IP) that provide detailed descriptions of the processes used to create a new chemical or a new process to manufacture a known chemical. The researcher must be able to understand the latest patents and literature in order to develop new chemicals and processes that do not infringe on existing claims and processes. This research uses text mining, integrated machine learning, and knowledge visualization techniques to effectively and accurately support the extraction and graphical presentation of chemical processes disclosed in patent documents. The computer framework trains a machine learning model called ALBERT for automatic paragraph text classification. ALBERT separates chemical and non-chemical descriptive paragraphs from a patent for effective chemical term extraction. The ChemDataExtractor is used to classify chemical terms, such as inputs, units, and reactions from the chemical paragraphs. A computer-supported graph-based knowledge representation interface is developed to plot the extracted chemical terms and their chemical process links as a network of nodes with connecting arcs. The computer-supported chemical knowledge visualization approach helps researchers to quickly understand the innovative and unique chemical or processes of any chemical patent of interest. Full article

(This article belongs to the Special Issue Recent Advances in Machine Learning and Applications)

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13 pages, 5876 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effect of

N b^{5 +}

and

I n^{3 +}

Ions on Moisture Sensitivity of Electrospun Titanium/Tungsten Oxide Nanostructures: Microstructural Characterization and Electrical Response

by Georgenes M. G. Silva, Victor N. S. Leão, Michel F. G. Pereira, Pedro M. Faia and Evando S. Araújo

Processes 2021, 9(8), 1336; https://doi.org/10.3390/pr9081336 - 30 Jul 2021

Cited by 2 | Viewed by 2098

Abstract

In this work,

N b^{5 +}

and

I n^{3 +}

ions were used as dopants in titanium/tungsten oxide nanostructures that are produced by the electrospinning and sintering process, for relative humidity (RH) detection. The microstructural properties were investigated [...] Read more.

In this work,

N b^{5 +}

and

I n^{3 +}

ions were used as dopants in titanium/tungsten oxide nanostructures that are produced by the electrospinning and sintering process, for relative humidity (RH) detection. The microstructural properties were investigated by SEM, EDS, XRD, Raman and FTIR techniques. The electrical response characterization of the samples was performed by electrical impedance spectroscopy in the range of 400 Hz to 40 MHz, at 20 °C. The sensors sensitivity to moisture was evaluated in terms of the impedance variations to RH (10–100%). The combined analysis of the microstructural characterization results confirmed the surface interaction between the oxides and the ions incorporation in

T i

crystal lattice. All the studied sensors showed a conduction transition from p- to n-type at around 30–40% RH: besides, they also displayed better sensitivity to moisture than those obtained in a previous work using titanium/tungsten combination using a different fabricationn route. The impedance modulus variation up to 1.1 and 1.3 orders of magnitude for the 4 wt % niobium and indium doped samples, respectively. The results are directly associated with the microstructure and alternative preparation process. Full article

(This article belongs to the Special Issue Design Processes via Manipulation of Nanoparticles and Their Suitability for Gas Sensors)

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17 pages, 9241 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Impact of Ballast Fouling on the Mechanical Properties of Railway Ballast: Insights from Discrete Element Analysis

by Luyu Wang, Mohamed Meguid and Hani S. Mitri

Processes 2021, 9(8), 1331; https://doi.org/10.3390/pr9081331 - 30 Jul 2021

Cited by 7 | Viewed by 2794

Abstract

Ballast fouling is a major factor that contributes to the reduction of shear strength of railway ballast, which can further affect the stability of railway supporting structure. The major sources of ballast fouling include infiltration of foreign fines into the ballast material and [...] Read more.

Ballast fouling is a major factor that contributes to the reduction of shear strength of railway ballast, which can further affect the stability of railway supporting structure. The major sources of ballast fouling include infiltration of foreign fines into the ballast material and ballast degradation induced by train movement on the supported tracks. In this paper, a discrete element model is developed and used to simulate the shear stress–strain response of fouled ballast assembly subjected to direct shear loading. A simplified computational approach is then proposed to model the induced ballast fouling and capture the mechanical response of the ballast at various levels of contamination. The approach is based on the assumption that fine particles comprising the fouling material will not only change the interparticle friction angle, but also the contact stiffness between the ballast particles. Therefore, both the interparticle friction coefficient and effective modulus are adjusted based on a fouled ballast model that is validated using experimental results. The effect of ballast degradation is also investigated by gradually changing the particle size distribution of the ballast assembly in the discrete element model to account for the increased range of particle sizes. Using the developed model, the effect of ballast degradation on the shear strength is then evaluated. Conclusions are made to highlight the suitability of these approximate approaches in efficiently modeling ballast assemblies under shear loading conditions. Full article

(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)

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14 pages, 2837 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Microbial Fuel Cell as a Bioelectrochemical Sensor of Nitrite Ions

by Arnas Klevinskas, Kristina Kantminienė, Nerita Žmuidzinavičienė, Ilona Jonuškienė and Egidijus Griškonis

Processes 2021, 9(8), 1330; https://doi.org/10.3390/pr9081330 - 30 Jul 2021

Cited by 7 | Viewed by 2505

Abstract

The deteriorating environmental quality requires a rapid in situ real-time monitoring of toxic compounds in environment including water and wastewater. One of the most toxic nitrogen-containing ions is nitrite ion, therefore, it is particularly important to ensure that nitrite ions are completely absent [...] Read more.

The deteriorating environmental quality requires a rapid in situ real-time monitoring of toxic compounds in environment including water and wastewater. One of the most toxic nitrogen-containing ions is nitrite ion, therefore, it is particularly important to ensure that nitrite ions are completely absent in surface and ground waters as well as in wastewater or, at least, their concentration does not exceed permissible levels. However, no selective ion electrode, which would enable continuous measurement of nitrite ion concentration in wastewater by bioelectrochemical sensor, is available. Microbial fuel cell (MFC)-based biosensor offers a sustainable low-cost alternative to the monitoring by periodic sampling for laboratory testing. It has been determined, that at low (0.01–0.1 mg·L⁻¹) and moderate (1.0–10 mg·L⁻¹) concentration of nitrite ions in anolyte-model wastewater, the voltage drop in MFC linearly depends on the logarithm of nitrite ion concentration of proving the potential of the application of MFC-based biosensor for the quantitative monitoring of nitrite ion concentration in wastewater and other surface water. Higher concentrations (100–1000 mg·L⁻¹) of nitrite ions in anolyte-model wastewater could not be accurately quantified due to a significant drop in MFC voltage. In this case MFC can potentially serve as a bioelectrochemical early warning device for extremely high nitrite pollution. Full article

(This article belongs to the Special Issue Advanced Applications, Processes, and Materials in Microbial Electrochemical Technologies)

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22 pages, 6987 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Microfluidic Network Simulations Enable On-Demand Prediction of Control Parameters for Operating Lab-on-a-Chip-Devices

by Julia Sophie Böke, Daniel Kraus and Thomas Henkel

Processes 2021, 9(8), 1320; https://doi.org/10.3390/pr9081320 - 29 Jul 2021

Cited by 3 | Viewed by 4137

Abstract

Reliable operation of lab-on-a-chip systems depends on user-friendly, precise, and predictable fluid management tailored to particular sub-tasks of the microfluidic process protocol and their required sample fluids. Pressure-driven flow control, where the sample fluids are delivered to the chip from pressurized feed vessels, [...] Read more.

Reliable operation of lab-on-a-chip systems depends on user-friendly, precise, and predictable fluid management tailored to particular sub-tasks of the microfluidic process protocol and their required sample fluids. Pressure-driven flow control, where the sample fluids are delivered to the chip from pressurized feed vessels, simplifies the fluid management even for multiple fluids. The achieved flow rates depend on the pressure settings, fluid properties, and pressure-throughput characteristics of the complete microfluidic system composed of the chip and the interconnecting tubing. The prediction of the required pressure settings for achieving given flow rates simplifies the control tasks and enables opportunities for automation. In our work, we utilize a fast-running, Kirchhoff-based microfluidic network simulation that solves the complete microfluidic system for in-line prediction of the required pressure settings within less than 200 ms. The appropriateness of and benefits from this approach are demonstrated as exemplary for creating multi-component laminar co-flow and the creation of droplets with variable composition. Image-based methods were combined with chemometric approaches for the readout and correlation of the created multi-component flow patterns with the predictions obtained from the solver. Full article

(This article belongs to the Special Issue Microfluidics in Chemical Engineering)

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38 pages, 2821 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Bibliometric Survey on Polyisobutylene Manufacture

by Jessica B. Alves, Mateus K. Vasconcelos, Lys H. R. Mangia, Maxmiliano Tatagiba, Juliana Fidalgo, Daniela Campos, Pedro L. Invernici, Marcio V. Rebouças, Marcio Henrique S. Andrade and José Carlos Pinto

Processes 2021, 9(8), 1315; https://doi.org/10.3390/pr9081315 - 29 Jul 2021

Cited by 10 | Viewed by 4899

Abstract

Polyisobutylenes (PIB) constitute a versatile family of polymer materials that have been used mainly as fuel and lubricant additives. Particularly, the current commercial demand for highly reactive polyisobutylene (HR-PIB) products motivates the development of new processes and procedures to produce PIBs with high [...] Read more.

Polyisobutylenes (PIB) constitute a versatile family of polymer materials that have been used mainly as fuel and lubricant additives. Particularly, the current commercial demand for highly reactive polyisobutylene (HR-PIB) products motivates the development of new processes and procedures to produce PIBs with high polymer yields, narrow molar mass distributions and high vinyl contents. For this reason, a bibliometric survey is presented here to map and discuss important technical aspects and technological trends in the field of solution cationic polymerization of isobutylenes. It is shown that investigations in this field are concentrated mainly on developed countries and that industrial initiatives indicate high commercial interest and significant investments in the field. It is also shown that use of catalyst systems based on AlCl₃ and ether cocatalysts can be very beneficial for PIB and HR-PIB manufacture. Finally, it is shown that investigations search for cheaper and environmentally friendly catalysts and solvents that can be employed at moderate temperatures, particularly for the production of HR-PIB. Full article

(This article belongs to the Special Issue Feature Review Papers in Advanced Process Systems Engineering)

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28 pages, 2622 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effects of Dynamic Pricing on the Design and Operation of Distributed Energy Resource Networks

by Tim Sidnell, Bogdan Dorneanu, Evgenia Mechleri, Vassilios S. Vassiliadis and Harvey Arellano-Garcia

Processes 2021, 9(8), 1306; https://doi.org/10.3390/pr9081306 - 28 Jul 2021

Cited by 3 | Viewed by 2140

Abstract

This paper presents a framework for the use of variable pricing to control electricity imported/exported to/from both fixed and unfixed residential distributed energy resource (DER) network designs. The framework shows that networks utilizing much of their own energy, and importing little from the [...] Read more.

This paper presents a framework for the use of variable pricing to control electricity imported/exported to/from both fixed and unfixed residential distributed energy resource (DER) network designs. The framework shows that networks utilizing much of their own energy, and importing little from the national grid, are barely affected by dynamic import pricing, but are encouraged to sell more by dynamic export pricing. An increase in CO₂ emissions per kWh of energy produced is observed for dynamic import and export, against a baseline configuration utilizing constant pricing. This is due to feed-in tariffs (FITs) that encourage CHP generation over lower-carbon technologies. Furthermore, batteries are shown to be expensive in systems receiving income from FITs and grid exports, but for the cases when they sell to/buy from the grid using dynamic pricing, their use in the networks becomes more economical. Full article

(This article belongs to the Special Issue Bioinspired Computation for Sustainable Energy Systems)

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13 pages, 858 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Evaluation of the PGPR Capacity of Four Bacterial Strains and Their Mixtures, Tested on Lupinus albus var. Dorado Seedlings, for the Bioremediation of Mercury-Polluted Soils

by Daniel González, Carlota Blanco, Agustín Probanza, Pedro A. Jiménez and Marina Robas

Processes 2021, 9(8), 1293; https://doi.org/10.3390/pr9081293 - 26 Jul 2021

Cited by 10 | Viewed by 2812

Abstract

Soil contamination by mercury, which is one of the most toxic heavy metals due to its bioaccumulative capacity, poses a risk to the environment as well as health. The Almadén mining district in Ciudad Real, Spain is one of the most heavily-polluted sites [...] Read more.

Soil contamination by mercury, which is one of the most toxic heavy metals due to its bioaccumulative capacity, poses a risk to the environment as well as health. The Almadén mining district in Ciudad Real, Spain is one of the most heavily-polluted sites in the world, making the soils unusable. Bioremediation, and more specifically phyto-rhizoremediation, based on the synergistic interaction established between plant and Plant Growth Promoting Rhizobacteria (PGPR), improves the plant’s ability to grow, mobilize, accumulate, and extract contaminants from the soil. The objective of this study is to evaluate the plant growth-promoting ability of four PGPR strains (and mixtures), isolated from the bulk soil and rhizosphere of naturally grown plants in the Almadén mining district, when they are inoculated in emerged seeds of Lupinus albus, var. Dorado in the presence of high concentrations of mercury. After 20 days of incubation and subsequent harvesting of the seedlings, biometric measurements were carried out at the root and aerial levels. The results obtained show that the seeds treatment with PGPR strains improves plants biometry in the presence of mercury. Specifically, strain B2 (Pseudomonas baetica) and B1 (Pseudomonas moraviensis) were those that contributed the most to plant growth, both individually and as part of mixtures (CS5 and CS3). Thus, these are postulated to be good candidates for further in situ phyto-rhizoremediation tests of mercury-contaminated soils. Full article

(This article belongs to the Special Issue Innovative Treatments for the Improvement of Bioremediation Processes)

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15 pages, 2526 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Fluctuation and Re-Establishment of Aerobic Granules Properties during the Long-Term Operation Period with Low-Strength and Low C/N Ratio Wastewater

by Lijuan Cha, Yong-Qiang Liu, Wenyan Duan, Christain E. W. Sternberg, Qiangjun Yuan and Fangyuan Chen

Processes 2021, 9(8), 1290; https://doi.org/10.3390/pr9081290 - 26 Jul 2021

Cited by 5 | Viewed by 2318

Abstract

Long-term structure stability of aerobic granules is critical to maintaining stable wastewater treatment performance. In this study, granulation and long-term stability of sludge-treating synthetic wastewater with a low chemical oxygen demand to nitrogen (COD/N) ratio of 4:1 and COD concentration of 400 mg/L [...] Read more.

Long-term structure stability of aerobic granules is critical to maintaining stable wastewater treatment performance. In this study, granulation and long-term stability of sludge-treating synthetic wastewater with a low chemical oxygen demand to nitrogen (COD/N) ratio of 4:1 and COD concentration of 400 mg/L in anoxic-oxic conditions were investigated for over 300 days. Inoculated suspended sludge gradually transformed into granules-dominant sludge on day 80. Due to the improved sludge volume index after 30 min settling (SVI₃₀), mixed liquor suspended solids (MLSS) reached 5.2 g/L on day 140. Without any external intervention or disturbance, aerobic granules started to disintegrate from day 140, causing the increase in SVI and the decrease in biomass concentration until day 210, with the average sludge size reduced to 243 µm. From day 210, granular sludge started to be re-established by re-granulation, and the average granule size increased to 500 µm on day 302. During these disintegration and re-granulation periods, there was no obvious difference in terms of COD removal and nitrification, but microbial species were found more diverse after the re-granulation, with Thauera and Sphingomonas dominant. Although there was no external intervention, the food to microorganisms ratio (F/M) varied significantly due to the changes in biomass concentration caused by strong selective pressure and the change of sludge-settling ability in the reactor. F/M ratios should be controlled between 0.3 and 1.0 gCOD/gSS·d to maintain the stable structure of granules to minimize the fluctuation of sludge properties under the conditions used in this study. Although aerobic granular sludge is able to re-establish itself after disintegration, controlling F/M ratios in a certain range would benefit long-term stability. The findings in this study are significant to deepen the understanding of granule stability with low-strength and low COD ratio wastewater and, thus, provide guidance for maintaining the long-term stability of granules. Full article

(This article belongs to the Section Environmental and Green Processes)

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17 pages, 1715 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

An Imperfect Production–Inventory Model with Mixed Materials Containing Scrap Returns Based on a Circular Economy

by Rung-Hung Su, Ming-Wei Weng, Chih-Te Yang and Hsin-Ting Li

Processes 2021, 9(8), 1275; https://doi.org/10.3390/pr9081275 - 24 Jul 2021

Cited by 8 | Viewed by 2622

Abstract

The implementation of scrap recovery activities has been shown to improve the financial performance of many firms, and this kind of circular economy (CE) is particularly evident in industries with green manufacturing (GM). In this paper, we consider an imperfect multiple-stage production system [...] Read more.

The implementation of scrap recovery activities has been shown to improve the financial performance of many firms, and this kind of circular economy (CE) is particularly evident in industries with green manufacturing (GM). In this paper, we consider an imperfect multiple-stage production system that manufactures paired products made from mixed materials containing scrap returns, in which the scrap returns are converted from defective products. The feed rates of scrap returns for two products are different, and the product with the higher feed rate is placed in the second order of the process to avoid unlimited accumulation of scrap returns. The proposed problem is formulated as a joint economic order quantity (EOQ) and economic production quantity (EPQ) model aimed at cost minimization. The decision variables of the proposed model include the production run time of two products, order quantity of new material, and the extent of investment in converted equipment. We also prove that the optimal solution exists uniquely and provide an algorithm for the computation of the optimal solution. Finally, a numerical example involving the pulp and paper manufacturing industry is provided to illustrate the solution process, and the results of its sensitivity analysis are also presented to show some managerial implications. Full article

(This article belongs to the Collection Tools, Approaches and Modeling in Sustainable Supply Chain Management)

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14 pages, 3718 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Influence of Freezing Parameters on the Formation of Internal Porous Structure and Its Impact on Freeze-Drying Kinetics

by Patrick Levin, Vincent Meunier, Ulrich Kessler and Stefan Heinrich

Processes 2021, 9(8), 1273; https://doi.org/10.3390/pr9081273 - 23 Jul 2021

Cited by 8 | Viewed by 3012

Abstract

The main objective of this study was firstly to investigate the influence of freezing process parameters on the formation of the internal structure of frozen coffee granules. It was investigated how these frozen internal structures affect the drying kinetics during freeze-drying. A design [...] Read more.

The main objective of this study was firstly to investigate the influence of freezing process parameters on the formation of the internal structure of frozen coffee granules. It was investigated how these frozen internal structures affect the drying kinetics during freeze-drying. A design of experiment study was carried out using the response surface method to quantify the influence of the freezing step that occurs in a scraped surface heat exchanger (SSHE). Therefore, the coffee extract at a concentration of 30% w/w is entering the SSHE as a liquid and gets partially crystallized up to a weight-based ice content of 0.364. During this step, the influence of factors like cooling temperature, scraper rotation speed and temperature cycles on ice crystal structure was investigated. In a second freezing step, the influence of freezing rates during hardening of the product by air-blast freezing is investigated, where the freezing rate is significantly affected by the cake thickness. The produced frozen granules were freeze-dried in single layer experiments. During drying the influence of internal structure on the drying kinetics was investigated. Results show that all factors have a significant impact on structure parameters for 30% w/w coffee solutions. A lower degree of supercooling during freezing in an SSHE, a higher number of temperature cycles (2 to 8 times) and lower freezing rates during hardening (2 °C/min to 10 °C/min) were leading to increased crystal size. This increase accelerates the primary drying rate and decreases the total drying time. A higher number of temperature cycles leads to a significant increase of crystal size and therefore larger pore size at the end of the primary drying. Furthermore, in combination with temperature cycles in the SSHE, it was found that high freezing rates during air blast freezing generally lead to a second nucleation step of ice crystals. Full article

(This article belongs to the Special Issue Modern Freeze Drying Design for More Efficient Processes)

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27 pages, 2158 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Capture of Acidic Gases from Flue Gas by Deep Eutectic Solvents

by Yan Wang, Shuhang Ren, Yucui Hou and Weize Wu

Processes 2021, 9(8), 1268; https://doi.org/10.3390/pr9081268 - 22 Jul 2021

Cited by 21 | Viewed by 3260

Abstract

Up to now, many kinds of deep eutectic solvents (DESs) were investigated for the capture of acidic gases from flue gases. In this review, non-functionalized and functionalized DESs, including binary and ternary DESs, for SO₂, CO₂ and NO capture, are [...] Read more.

Up to now, many kinds of deep eutectic solvents (DESs) were investigated for the capture of acidic gases from flue gases. In this review, non-functionalized and functionalized DESs, including binary and ternary DESs, for SO₂, CO₂ and NO capture, are summarized based on the mechanism of absorption, physical interaction or chemical reaction. New strategies for improving the absorption capacity are introduced in this review. For example, a third component can be introduced to form a ternary DES to suppress the increase in viscosity and improve the CO₂ absorption capacity. DESs, synthesized with halogen salt hydrogen bond acceptors (HBAs) and functionalized hydrogen bond donors (HBDs), can be used for the absorption of SO₂ and NO with high absorption capacities and low viscosities after absorption, due to physicochemical interaction between gases and DESs. Emphasis is given to introducing the absorption capacities of acidic gases in these DESs, the mechanism of the absorption, and the ways to enhance the absorption capacity. Full article

(This article belongs to the Special Issue Advances in Deep Eutectic Solvents: New Green Solvents)

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11 pages, 1581 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Influence of Process Design on the Preparation of Solid Lipid Nanoparticles by an Ultrasonic-Nanoemulsification Method

by Agata Pucek-Kaczmarek

Processes 2021, 9(8), 1265; https://doi.org/10.3390/pr9081265 - 22 Jul 2021

Cited by 12 | Viewed by 3200

Abstract

In recent years, lipid-based nanosystems have emerged as a promising class of nanocarriers for encapsulating many active agents. Solid lipid nanoparticles (SLNs) provide good stability (colloidal as well as physical) and high biocompatibility. Appropriate design of the carrier structure through a selection of [...] Read more.

In recent years, lipid-based nanosystems have emerged as a promising class of nanocarriers for encapsulating many active agents. Solid lipid nanoparticles (SLNs) provide good stability (colloidal as well as physical) and high biocompatibility. Appropriate design of the carrier structure through a selection of components and preparation methods allows us to obtain formulations with desired physicochemical parameters and biological properties. The present contribution has been carried out to investigate SLNs containing biocompatible phosphatidylcholine mixed with non-ionic surfactant Tween 60 as stabilizing agents. The internal lipid phase consisted of glyceryl monostearate was confirmed as safe for drug delivery by the Food and Drug Administration. The SLNs were fabricated by ultrasonic-nanoemulsification method. The preparation process was optimized in regard to variable parameters such as ultrasonication time and used amplitude and number of cycles. The sizes of the studied nanoparticles along with the size distribution were determined by dynamic light scattering (DLS), while shape and morphology were determined by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The colloidal stability was measured by a turbidimetric method. The physical state of SLNs was characterized using differential scanning calorimetry (DSC). The obtained results indicate that the proposed SLNs may provide great potential for design and preparation of novel delivery nanosystems with a variety of possible applications. Full article

(This article belongs to the Special Issue Nanoemulsion Processes Design and Applications)

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11 pages, 2519 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Aluminum-Free Steelmaking: Desulfurization and Nonmetallic Inclusion Evolution of Si-Killed Steel in Contact with CaO-SiO₂-CaF₂-MgO Slag

by Stephano P. T. Piva and Petrus Christiaan Pistorius

Processes 2021, 9(8), 1258; https://doi.org/10.3390/pr9081258 - 21 Jul 2021

Cited by 3 | Viewed by 3902

Abstract

In some applications, deep desulfurization and deoxidation of steels without the use of aluminum are required, using Si as a deoxidant instead, with double-saturated slags in the CaO-SiO₂-CaF₂-MgO system. This work studied the desulfurization and nonmetallic inclusion evolution for [...] Read more.

In some applications, deep desulfurization and deoxidation of steels without the use of aluminum are required, using Si as a deoxidant instead, with double-saturated slags in the CaO-SiO₂-CaF₂-MgO system. This work studied the desulfurization and nonmetallic inclusion evolution for the system using an induction furnace and compared the results with FactSage kinetic simulations. Steel samples were taken from the steel melt and analyzed with ICP-MS and combustion analysis for chemistry, and SEM/EDS for nonmetallic inclusion quantity, size, and composition. The results indicate that the steel was deeply desulfurized, with a final sulfur partition coefficient of 580; MgO was reduced from the slag, yielding dissolved [Mg] that transformed liquid Mn–silicate inclusions into forsterite and MgO. Intentional reoxidation of the melt with oxidized electrolytic iron demonstrated a significant concentration of dissolved [Mg] in the steel, by the formation of additional forsterite and MgO upon reoxidation. Full article

(This article belongs to the Section Process Control and Monitoring)

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19 pages, 1536 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Advanced Kinetic Modeling of Bio-co-polymer Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Production Using Fructose and Propionate as Carbon Sources

by Stefanie Duvigneau, Robert Dürr, Jessica Behrens and Achim Kienle

Processes 2021, 9(8), 1260; https://doi.org/10.3390/pr9081260 - 21 Jul 2021

Cited by 11 | Viewed by 2831

Abstract

Biopolymers are a promising alternative to petroleum-based plastic raw materials. They are bio-based, non-toxic and degradable under environmental conditions. In addition to the homopolymer poly(3-hydroxybutyrate) (PHB), there are a number of co-polymers that have a broad range of applications and are easier to [...] Read more.

Biopolymers are a promising alternative to petroleum-based plastic raw materials. They are bio-based, non-toxic and degradable under environmental conditions. In addition to the homopolymer poly(3-hydroxybutyrate) (PHB), there are a number of co-polymers that have a broad range of applications and are easier to process in comparison to PHB. The most prominent representative from this group of bio-copolymers is poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). In this article, we show a new kinetic model that describes the PHBV production from fructose and propionic acid in Cupriavidus necator (C. necator). The developed model is used to analyze the effects of process parameter variations such as the CO

_{2}

amount in the exhaust gas and the feed rate. The presented model is a valuable tool to improve the microbial PHBV production process. Due to the coupling of CO

_{2}

online measurements in the exhaust gas to the biomass production, the model has the potential to predict the composition and the current yield of PHBV in the ongoing process. Full article

(This article belongs to the Special Issue Mathematical Modeling and Control of Bioprocesses)

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16 pages, 1467 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Prediction of Sugar Content in Port Wine Vintage Grapes Using Machine Learning and Hyperspectral Imaging

by Véronique Gomes, Marco S. Reis, Francisco Rovira-Más, Ana Mendes-Ferreira and Pedro Melo-Pinto

Processes 2021, 9(7), 1241; https://doi.org/10.3390/pr9071241 - 19 Jul 2021

Cited by 17 | Viewed by 3241

Abstract

The high quality of Port wine is the result of a sequence of winemaking operations, such as harvesting, maceration, fermentation, extraction and aging. These stages require proper monitoring and control, in order to consistently achieve the desired wine properties. The present work focuses [...] Read more.

The high quality of Port wine is the result of a sequence of winemaking operations, such as harvesting, maceration, fermentation, extraction and aging. These stages require proper monitoring and control, in order to consistently achieve the desired wine properties. The present work focuses on the harvesting stage, where the sugar content of grapes plays a key role as one of the critical maturity parameters. Our approach makes use of hyperspectral imaging technology to rapidly extract information from wine grape berries; the collected spectra are fed to machine learning algorithms that produce estimates of the sugar level. A consistent predictive capability is important for establishing the harvest date, as well as to select the best grapes to produce specific high-quality wines. We compared four different machine learning methods (including deep learning), assessing their generalization capacity for different vintages and varieties not included in the training process. Ridge regression, partial least squares, neural networks and convolutional neural networks were the methods considered to conduct this comparison. The results show that the estimated models can successfully predict the sugar content from hyperspectral data, with the convolutional neural network outperforming the other methods. Full article

(This article belongs to the Special Issue Emerging Trends in the Wine Ageing Process)

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14 pages, 8598 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Studies of the Anti-Diabetic Mechanism of Pueraria lobata Based on Metabolomics and Network Pharmacology

by Shu Zhang, Qi Ge, Liang Chen and Keping Chen

Processes 2021, 9(7), 1245; https://doi.org/10.3390/pr9071245 - 19 Jul 2021

Cited by 9 | Viewed by 3210

Abstract

Diabetes mellitus (DM), as a chronic disease caused by insulin deficiency or using obstacles, is gradually becoming a principal worldwide health problem. Pueraria lobata is one of the traditional Chinese medicinal and edible plants, playing roles in improving the cardiovascular system, lowering blood [...] Read more.

Diabetes mellitus (DM), as a chronic disease caused by insulin deficiency or using obstacles, is gradually becoming a principal worldwide health problem. Pueraria lobata is one of the traditional Chinese medicinal and edible plants, playing roles in improving the cardiovascular system, lowering blood sugar, anti-inflammation, anti-oxidation, and so on. Studies on the hypoglycemic effects of Pueraria lobata were also frequently reported. To determine the active ingredients and related targets of Pueraria lobata for DM, 256 metabolites were identified by LC/MS non targeted metabonomics, and 19 active ingredients interacting with 51 DM-related targets were screened. The results showed that puerarin, quercetin, genistein, daidzein, and other active ingredients in Pueraria lobata could participate in the AGE-RAGE signaling pathway, insulin resistance, HIF-1 signaling pathway, FoxO signaling pathway, and MAPK signaling pathway by acting on VEGFA, INS, INSR, IL-6, TNF and AKT1, and may regulate type 2 diabetes, inflammation, atherosis and diabetes complications, such as diabetic retinopathy, diabetic nephropathy, and diabetic cardiomyopathy. Full article

(This article belongs to the Special Issue Network Pharmacology Modelling for Drug Discovery)

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21 pages, 23731 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Bi-Functional Catalyst/Sorbent for a H₂-Rich Gas from Biomass Gasification

by Francesca Micheli, Enrica Mattucci, Claire Courson and Katia Gallucci

Processes 2021, 9(7), 1249; https://doi.org/10.3390/pr9071249 - 19 Jul 2021

Cited by 5 | Viewed by 2457

Abstract

The aim of this work is to identify the effect of the CaO phase as a CO₂ sorbent and mayenite (Ca₁₂Al₁₄O₃₃) as a stabilizing phase in a bi-functional material for CO₂ capture in biomass syngas [...] Read more.

The aim of this work is to identify the effect of the CaO phase as a CO₂ sorbent and mayenite (Ca₁₂Al₁₄O₃₃) as a stabilizing phase in a bi-functional material for CO₂ capture in biomass syngas conditioning and cleaning at high temperature. The effect of different CaO weight contents is studied (0, 56, 85, 100 wt%) in sorbents synthesized by the wet mixing method. These high temperature solid sorbents are upgraded to bi-functional compounds by the addition of 3 or 6 wt% of nickel chosen as the metal active phase. N₂ adsorption, X-ray diffraction, scanning electronic microscopy, temperature-programmed reduction analyses and CO₂ sorption study were performed to characterize structural, textural, reducibility and sorption properties of bi-functional materials. Finally, sorption-enhanced reforming of toluene (chosen as tar model), of methane then of methane and toluene with bi-functional compounds were performed to study the best material to improve H₂ content in a syngas, provided by steam biomass gasification. If the catalytic activity on the sorption enhanced reforming of methane exhibits a fast fall-down after 10–15 min of experimental test, the reforming of toluene reaches a constant conversion of 99.9% by using bi-functional materials. Full article

(This article belongs to the Special Issue Methane Reforming Processes)

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13 pages, 2504 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Ultra-Fast Electrochemical Sensor for Point-of-Care COVID-19 Diagnosis Using Non-Invasive Saliva Sampling

by Ashwin Ramanujam, Sharilyn Almodovar and Gerardine G. Botte

Processes 2021, 9(7), 1236; https://doi.org/10.3390/pr9071236 - 17 Jul 2021

Cited by 23 | Viewed by 4689

Abstract

Point-of-care diagnostic devices that are rapid and reliable remain as an unmet need highlighted by the coronavirus disease (COVID-19) pandemic crisis. The second/third wave of virus spread in various parts of the world combined with new evidence of re-infections and inadequate healthcare facilities [...] Read more.

Point-of-care diagnostic devices that are rapid and reliable remain as an unmet need highlighted by the coronavirus disease (COVID-19) pandemic crisis. The second/third wave of virus spread in various parts of the world combined with new evidence of re-infections and inadequate healthcare facilities demand increased testing rate to diagnose COVID-19 at its core. Although traditional molecular diagnostic tests have served this purpose, there have been shortage of reagents and other supplies at pandemic frontlines. This calls for novel alternate diagnostic processes with potential for obtaining emergency use authorization and that can be deployed in the field at the earliest opportunity. Here, we show an ultra-fast SARS-CoV-2 detection sensor for detecting coronavirus proteins in saliva within 100 milliseconds. Electrochemical oxidation of nickel hydroxide has been controlled using cyclic voltammetry and chronoamperometry techniques for successful detection of SARS-CoV-2. Test results have proven the capability of sensors to quantitatively detect the concentration of virus in blinded analyses. The detection occurs by a process similar to that of SARS-CoV-2 binding onto host cells. The sensor also shows prospects in distinguishing SARS-CoV-2 from other viruses such as HIV. More importantly, the sensor matches the detection limit of the gold standard test for diagnosing early infection. The use of saliva as a non-invasive sampling technique combined with the portability of the instrument has broadened the potential of this sensor. Full article

(This article belongs to the Special Issue Advanced Applications, Processes, and Materials in Microbial Electrochemical Technologies)

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12 pages, 2832 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Interactive Effects in Two-Droplets Combustion of RP-3 Kerosene under Sub-Atmospheric Pressure

by Hongtao Zhang, Zhihua Wang, Yong He, Jie Huang and Kefa Cen

Processes 2021, 9(7), 1229; https://doi.org/10.3390/pr9071229 - 16 Jul 2021

Cited by 8 | Viewed by 2366

Abstract

To improve our understanding of the interactive effects in combustion of binary multicomponent fuel droplets at sub-atmospheric pressure, combustion experiments were conducted on two fibre-supported RP-3 kerosene droplets at pressures from 0.2 to 1.0 bar. The burning life of the interactive droplets was [...] Read more.

To improve our understanding of the interactive effects in combustion of binary multicomponent fuel droplets at sub-atmospheric pressure, combustion experiments were conducted on two fibre-supported RP-3 kerosene droplets at pressures from 0.2 to 1.0 bar. The burning life of the interactive droplets was recorded by a high-speed camera and a mirrorless camera. The results showed that the flame propagation time from burning droplet to unburned droplet was proportional to the normalised spacing distance between droplets and the ambient pressure. Meanwhile, the maximum normalised spacing distance from which the left droplet can be ignited has been investigated under different ambient pressure. The burning rate was evaluated and found to have the same trend as the single droplet combustion, which decreased with the reduction in the pressure. For every experiment, the interactive coefficient was less than one owing to the oxygen competition, except for the experiment at L/D₀ = 2.5 and P = 1.0 bar. During the interactive combustion, puffing and microexplosion were found to have a significant impact on secondary atomization, ignition and extinction. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

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19 pages, 13452 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Numerical Study of Electrostatic Desalting Process Based on Droplet Collision Time

by Marco A. Ramirez-Argaez, Diego Abreú-López, Jesús Gracia-Fadrique and Abhishek Dutta

Processes 2021, 9(7), 1226; https://doi.org/10.3390/pr9071226 - 15 Jul 2021

Cited by 5 | Viewed by 3331

Abstract

The desalting process of an electrostatic desalting unit was studied using the collision time of two droplets in a water-in-oil (W/O) emulsion based on force balance. Initially, the model was solved numerically to perform a process analysis and to indicate the effect of [...] Read more.

The desalting process of an electrostatic desalting unit was studied using the collision time of two droplets in a water-in-oil (W/O) emulsion based on force balance. Initially, the model was solved numerically to perform a process analysis and to indicate the effect of the main process parameters, such as electric field strength, water content, temperature (through oil viscosity) and droplet size on the collision time or frequency of collision between a pair of droplets. In decreasing order of importance on the reduction of collision time and consequently on the efficiency of desalting separation, the following variables can be classified such as moisture content, electrostatic field strength, oil viscosity and droplet size. After this analysis, a computational fluid dynamics (CFD) model of a biphasic water–oil flow was developed in steady state using a Eulerian multiphase framework, in which collision frequency and probability of coalescence of droplets were assumed. This study provides some insights into the heterogeneity of a desalination plant which highlights aspects of design performance. This study further emphasizes the importance of two variables as moisture content and intensity of electrostatic field for dehydrated desalination by comparing the simulation with the electrostatic field against the same simulation without its presence. The overall objective of this study is therefore to show the necessity of including complex phenomena such as the frequency of collisions and coalescence in a CFD model for better understanding and optimization of the desalting process from both process safety and improvement. Full article

(This article belongs to the Special Issue Process Design and Sustainable Development)

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29 pages, 12765 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Influence of Interfacial Force Models and Population Balance Models on the k_La Value in Stirred Bioreactors

by Stefan Seidel and Dieter Eibl

Processes 2021, 9(7), 1185; https://doi.org/10.3390/pr9071185 - 7 Jul 2021

Cited by 10 | Viewed by 3833

Abstract

Optimal oxygen supply is vitally important for the cultivation of aerobically growing cells, as it has a direct influence on cell growth and product formation. A process engineering parameter directly related to oxygen supply is the volumetric oxygen mass transfer coefficient [...] Read more.

Optimal oxygen supply is vitally important for the cultivation of aerobically growing cells, as it has a direct influence on cell growth and product formation. A process engineering parameter directly related to oxygen supply is the volumetric oxygen mass transfer coefficient

k_{L} a

. It is the influences on

k_{L} a

and computing time of different interfacial force and population balance models in stirred bioreactors that have been evaluated in this study. For this investigation, the OpenFOAM 7 open-source toolbox was utilized. Firstly, the Euler–Euler model with a constant bubble diameter was applied to a 2

L

scale bioreactor to statistically examine the influence of different interfacial models on the

k_{L} a

value. It was shown that the

k_{L}

model and the constant bubble diameter have the greatest influence on the calculated

k_{L} a

value. To eliminate the problem of a constant bubble diameter and to take effects such as bubble breakup and coalescence into account, the Euler–Euler model was coupled with population balance models (PBM). For this purpose, four coalescence and five bubble breakup models were examined. Ultimately, it was established that, for all of the models tested, coupling computational fluid dynamics (CFD) with PBM resulted in better agreement with the experimental data than using the Euler–Euler model. However, it should be noted that the higher accuracy of the PBM coupled models requires twice the computation time. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics: Modelling of Industrial Dispersed Systems)

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29 pages, 4073 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A Real-Time Optimization Strategy for Small-Scale Facilities and Implementation in a Gas Processing Unit

by Pedro A. Delou, Leonardo D. Ribeiro, Carlos R. Paiva, Jacques Niederberger, Marcos Vinícius C. Gomes and Argimiro R. Secchi

Processes 2021, 9(7), 1179; https://doi.org/10.3390/pr9071179 - 7 Jul 2021

Cited by 4 | Viewed by 3151

Abstract

The rise of new digital technologies and their applications in several areas pushes the process industry to update its methodologies with more intensive use of mathematical models—commonly denoted as digital twins—and artificial intelligence (AI) approaches to continuously enhance operational efficiency. In this context, [...] Read more.

The rise of new digital technologies and their applications in several areas pushes the process industry to update its methodologies with more intensive use of mathematical models—commonly denoted as digital twins—and artificial intelligence (AI) approaches to continuously enhance operational efficiency. In this context, Real-time Optimization (RTO) is a strategy that is able to maximize an economic function while respecting the existing constraints, which enables keeping the operation at its optimum point even though the plant is subjected to nonlinear behavior and frequent disturbances. However, the investment related to the project of commercial RTOs may make its application infeasible for small-scale facilities. In this work, an in-house, small-scale RTO is presented and its successful application in a real industrial case—a Natural Gas Processing Unit—is shown. Besides that, a new method for enhancing the efficiency of using sequential-modular simulator inside an optimization framework and a new method to account for the economic return of optimization-based tools are proposed and described. The application of RTO in the industrial case showed an enhancement in the stability of the main variables and an increase in profit of 0.64% when compared to the operation of the regulatory control layer alone. Full article

(This article belongs to the Special Issue Modelling, Monitoring, Control and Optimization for Complex Industrial Processes)

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17 pages, 4875 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Storing Energy from External Power Supplies Using Phase Change Materials and Various Pipe Configurations

by Daniel Aprile, Samer Al-Banna, Arraventhan Maheswaran, Joshua Paquette and Mohamad Ziad Saghir

Processes 2021, 9(7), 1160; https://doi.org/10.3390/pr9071160 - 3 Jul 2021

Cited by 2 | Viewed by 2266

Abstract

Phase change materials are commonly used for energy storage. Heat transfer enhancement and heat storage are the two main goals in this paper. A cylindrical pipe covered with phase change material is investigated numerically. Ideally, a high temperature liquid flows through the pipe, [...] Read more.

Phase change materials are commonly used for energy storage. Heat transfer enhancement and heat storage are the two main goals in this paper. A cylindrical pipe covered with phase change material is investigated numerically. Ideally, a high temperature liquid flows through the pipe, resulting in heat transferred to the phase change material. To enhance the heat transfer, various configurations involving the addition of a twisted tape inside of the pipe and the use of helical shape pipes were investigated. A straight pipe with no twisted tape insert was also analyzed and used as a benchmark case. All the configurations had constant properties such as material selection, overall size, pipe diameter and inlet Reynold’s number, so the performance could be compared under similar conditions. All initial configurations were simulated and the heat transfer rate, Nusselt number, friction factor and performance evaluation criterion (PEC) of the designs were determined. It was found that the heat transfer rate and Nusselt number of all the various designs yielded higher results than the reference straight pipe configuration. Additionally, due to the added complexity in the flow caused by the insert, the friction factor of all the configurations was also higher. The helical pipe configuration was the only configuration that had a PEC higher than that of the reference straight pipe. This is because the negative impacts caused by the friction factor outweighed the gains in Nusselt number for the twisted tape designs. It was also hypothesized that lowering the inner diameter of the helical pipe would increase the PEC. Further simulations with modified inner diameters were done to test the hypothesis. The simulations confirmed the hypothesis, as the pipes with inner diameters 0.75 and 0.5 cm led to a 50% and 150% increase in the PEC respectively, when compared to an inner diameter of 1 cm. It was also determined that smaller inner diameters led to lower outlet temperatures meaning a higher percentage of the thermal energy from the fluid was transferred to the phase change material. Full article

(This article belongs to the Special Issue Design, Simulation and Applications of Phase Change Materials in Thermal Energy Storage Systems)

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15 pages, 2990 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Extraction of Added-Value Triterpenoids from Acacia dealbata Leaves Using Supercritical Fluid Extraction

by Vítor H. Rodrigues, Marcelo M. R. de Melo, Inês Portugal and Carlos M. Silva

Processes 2021, 9(7), 1159; https://doi.org/10.3390/pr9071159 - 3 Jul 2021

Cited by 9 | Viewed by 3262

Abstract

Forestry biomass is a by-product which commonly ends up being burnt for energy generation, despite comprising valuable bioactive compounds with valorisation potential. Leaves of Acacia dealbata were extracted for the first time by supercritical fluid extraction (SFE) using different conditions of pressure, temperature [...] Read more.

Forestry biomass is a by-product which commonly ends up being burnt for energy generation, despite comprising valuable bioactive compounds with valorisation potential. Leaves of Acacia dealbata were extracted for the first time by supercritical fluid extraction (SFE) using different conditions of pressure, temperature and cosolvents. Total extraction yield, individual triterpenoids extraction yields and concentrations were assessed and contrasted with Soxhlet extractions using solvents of distinct polarity. The extracts were characterized by gas chromatography coupled to mass spectrometry (GC-MS) and target triterpenoids were quantified. The total extraction yields ranged from 1.76 to 11.58 wt.% and the major compounds identified were fatty acids, polyols, and, from the triterpenoids family, lupenone, α-amyrin and β-amyrin. SFE was selective to lupenone, with higher individual yields (2139–3512

{mg kg}_{leaves}^{- 1}

) and concentrations (10.1–12.4 wt.%) in comparison to Soxhlet extractions, which in turn obtained higher yields and concentrations of the remaining triterpenoids. Full article

(This article belongs to the Special Issue Extraction, Utilization and Conversion of Woody Biomass)

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12 pages, 743 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Efficacy of Different Waste and By-Products from Forest and Food Industries in the Removal/Retention of the Antibiotic Cefuroxime

by Raquel Cela-Dablanca, Carolina Nebot, Lucia Rodríguez López, David Fernández-Calviño, Manuel Arias-Estévez, Avelino Núñez-Delgado, María J. Fernández-Sanjurjo and Esperanza Álvarez-Rodríguez

Processes 2021, 9(7), 1151; https://doi.org/10.3390/pr9071151 - 1 Jul 2021

Cited by 14 | Viewed by 2512

Abstract

Environmental pollution due to antibiotics is a serious problem. In this work, the adsorption and desorption of the antibiotic cefuroxime (CFX) were studied in four by-products/residues from the forestry and food industries. For this, batch-type experiments were carried out, adding increasing concentrations of [...] Read more.

Environmental pollution due to antibiotics is a serious problem. In this work, the adsorption and desorption of the antibiotic cefuroxime (CFX) were studied in four by-products/residues from the forestry and food industries. For this, batch-type experiments were carried out, adding increasing concentrations of CFX (from 0 to 50 µmol L⁻¹) to 0.5 g of adsorbent. The materials with a pH higher than 9 (mussel shell and wood ash) were those that presented the highest adsorption percentages, from 71.2% (23.1 µmol kg⁻¹) to 98.6% (928.0 µmol kg⁻¹). For the rest of the adsorbents, the adsorption was also around 100% when the lowest concentrations of CFX were added, but the percentage dropped sharply when the highest dose of the antibiotic was incorporated. Adsorption data fitted well to the Langmuir and Freundlich models, with R² greater than 0.9. Regarding desorption, the materials that presented the lowest values when the highest concentration of CFX was added were wood ash (0%) and mussel shell (2.1%), while pine bark and eucalyptus leaves presented the highest desorption (26.6% and 28.6%, respectively). Therefore, wood ash and mussel shell could be considered adsorbents with a high potential to be used in problems of environmental contamination by CFX. Full article

(This article belongs to the Topic New Research on Detection and Removal of Emerging Pollutants)

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15 pages, 3224 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Residual Life Prediction for Induction Furnace by Sequential Encoder with s-Convolutional LSTM

by Yulim Choi, Hyeonho Kwun, Dohee Kim, Eunju Lee and Hyerim Bae

Processes 2021, 9(7), 1121; https://doi.org/10.3390/pr9071121 - 28 Jun 2021

Cited by 7 | Viewed by 3283

Abstract

Induction furnaces are widely used for melting scrapped steel in small foundries and their use has recently become more frequent. The maintenance of induction furnaces is usually based on empirical decisions of the operator and an explosion can occur through operator error. To [...] Read more.

Induction furnaces are widely used for melting scrapped steel in small foundries and their use has recently become more frequent. The maintenance of induction furnaces is usually based on empirical decisions of the operator and an explosion can occur through operator error. To prevent an explosion, previous studies have utilized statistical models but have been unable to generalize the problem and have achieved a low accuracy. Herein, we propose a data-driven method for induction furnaces by proposing a novel 2D matrix called a sequential feature matrix(s-encoder) and multi-channel convolutional long short-term memory (s-ConLSTM). First, the sensor data and operation data are converted into sequential feature matrices. Then, N-sequential feature matrices are imported into the convolutional LSTM model to predict the residual life of the induction furnace wall. Based on our experimental results, our method outperforms general neural network models and enhances the safe use of induction furnaces. Full article

(This article belongs to the Special Issue Application of Big Data Analysis and Advanced Analytics in Sustainable Production Process)

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24 pages, 2366 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Improvements of Micro-CHP SOFC System Operation by Efficient Dynamic Simulation Methods

by Laura Nousch, Mathias Hartmann and Alexander Michaelis

Processes 2021, 9(7), 1113; https://doi.org/10.3390/pr9071113 - 26 Jun 2021

Cited by 2 | Viewed by 3022

Abstract

Solid Oxide Fuel Cell (SOFC) technology is of high interest for stationary decentralized generation of electricity and heat in combined heat and power systems (CHP) for the residential sector. Application scenarios for SOFC systems in an electricity-regulated mode play an important role, especially [...] Read more.

Solid Oxide Fuel Cell (SOFC) technology is of high interest for stationary decentralized generation of electricity and heat in combined heat and power systems (CHP) for the residential sector. Application scenarios for SOFC systems in an electricity-regulated mode play an important role, especially in places where an electrical grid connection is not available or rather unstable. The advantages of SOFC systems are the high fuel flexibility and the high efficiencies also under partial load operation compared to other decentralized power generation technologies. Due to the long, energy-consuming system heat-up and the limited partial load capability, SOFC systems do not reach the performance of conventional power generation technologies. Furthermore, stack thermal cycling is associated with power degradation and should be minimized. In this paper, the improvement of these drawbacks are investigated for hotbox-based SOFC systems in the 1 kW_el-class for residential applications. Since experimental investigations of the high-temperature systems are limited, modeling tools are established, enabling the visualization of internal system characteristics and providing the opportunity to simulate system operation in critical regions. To achieve this, a methodology for dynamic SOFC system modeling in a process engineering manner is developed based on the modeling language Modelica. A suitable approach is particularly important for modeling and simulation of the strong thermal interaction between the hot system components within the hotbox. The parametrized and validated models are used for the investigation of different dynamic effects, such as the system heat-up and the operation in low partial load points. A second reduced thermal system model aims for annual simulations of the SOFC system together with a battery to investigate the number of thermal cycles and the advantage of a hot standby operation. As a result, it is found that an adequate control of the power input at the start-up device and the cathode air flow has a high improvement potential to increase the stack heating rate and accelerate the heat-up in an energy-saving way. The hotbox-internal thermal management is identified as a crucial issue to reach low partial load points. To avoid the risk of stack cooling, lower heat losses and/or additional heat sources are of importance. Furthermore, the robustness of the tail gas oxidizer is found to be crucial for a higher load flexibility during partial load and the end of life stack operation. The annual simulation results indicate that operating the battery hybrid system with a hot standby mode requires much lower battery capacity for a high grid independence and a complete avoidance of system shutdown and associated power degradation. Full article

(This article belongs to the Special Issue Hydrogen Energy Systems: Optimization Models, Control and Simulation)

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22 pages, 8658 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Design and Optimization of a Curved-Crease-Folding Process Applied to a Light Metallic Structure

by Doina Raducanu, Vasile Danut Cojocaru, Vlad Andrei Raducanu, Anna Nocivin, Nicolae Serban, Ion Cinca, Elisabeta Mirela Cojocaru, Laurentiu Moldovan, Corneliu Trisca-Rusu and Irina Varvara Balkan

Processes 2021, 9(7), 1110; https://doi.org/10.3390/pr9071110 - 25 Jun 2021

Cited by 2 | Viewed by 3379

Abstract

Presently, the realization of complex, unconventional designs using efficient modalities is possible due to an increasing interest in interdisciplinary approaches: materials science, mathematics, IT, architecture, etc. Computerized techniques, among which the algorithmic/generative design is the most advanced one, that are associated with the [...] Read more.

Presently, the realization of complex, unconventional designs using efficient modalities is possible due to an increasing interest in interdisciplinary approaches: materials science, mathematics, IT, architecture, etc. Computerized techniques, among which the algorithmic/generative design is the most advanced one, that are associated with the individualized production methods are used for finding solutions for modern spatial forms with an unconventional spatial geometric shape, which are generically called “free-forms”. This work presents the design, realization and testing of a thin-walled metallic structure proposed as a light structural unit. An integrated research approach was proposed that utilized an algorithmic/digital design applied to the curved-crease-folding method with the study (at different length scales) of the metallic material behaviour after folding. An original method was proposed for the digital design and simulations. The specific mechanical behaviour of the metallic material in the elastic–plastic regime was used in this case to improve the structural performances; mechanical and structural tests were realized to analyse the behaviour of the entire structure. The results are useful for enhancing the accuracy of the digital design, the structural simulation programs and the fabrication methods. Full article

(This article belongs to the Special Issue Design and Optimization in Process Engineering)

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18 pages, 9859 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Electrothermal Desiccant Regeneration Technique for Air Dehumidification

by Chih-Hao Chen, Yu-Hao Kang, Jing-Hung Lu, Ming-Lang Hung, Jyi-Ching Perng and Jiun-Jen Chen

Processes 2021, 9(7), 1082; https://doi.org/10.3390/pr9071082 - 22 Jun 2021

Cited by 3 | Viewed by 4747

Abstract

Adsorption dehumidification and drying equipment is essential general equipment for domestic and industrial use. The most commonly used type in industry is the compressed air adsorption dryer. The analysis results show that the heat loss of the traditional heat air regeneration system of [...] Read more.

Adsorption dehumidification and drying equipment is essential general equipment for domestic and industrial use. The most commonly used type in industry is the compressed air adsorption dryer. The analysis results show that the heat loss of the traditional heat air regeneration system of the compressor dryer is 39.4%, and the exhaust waste heat is 32.4%. The actual use of heat energy for desiccant regeneration is only 28.2%. Therefore, this study uses an innovative electrothermal adsorbent unit (ETAU) to regenerate the desiccant. By directly heating the adsorbent, heat loss can be effectively improved. On the other hand, the composite arrangement of zeolite and activated alumina is used. The inlet compressed air is firstly treated by the activated alumina, which has a high adsorption capacity in the high relative humidity condition, then a zeolite is used as a second part to make the dew point reach –40 °C. In the regeneration step, the airflow direction is reversed, whereby the zeolite is regenerated by the ETAU, and the waste heat of the exhaust air is used to regenerate the activated alumina, which reduces the temperature of the exhaust air. Compared with the traditional heat air compressed air system, the two technologies can save about 27% energy in total. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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14 pages, 1893 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Efficacy and Safety of Modified Huang-Lian-Jie-Du Decoction Cream on Cancer Patients with Skin Side Effects Caused by EGFR Inhibition

by Ming-Yang Lee, Mei-Yi Lin, Yu-Ju Chang, Yu-Ting Tseng, I-An Huang, Wan-Ting Huang and Yi-Wen Liu

Processes 2021, 9(7), 1081; https://doi.org/10.3390/pr9071081 - 22 Jun 2021

Cited by 2 | Viewed by 2702

Abstract

(1) Background: The epidermal growth factor inhibitors (EGFRIs)/tyrosine kinase inhibitors (TKIs) are effective for cancer target therapy, but acneiform rashes or so-called inflammatory papulopustular exanthemas are common (50% to 90%). The conventional therapy for EGFRIs/TKIs-induced skin toxicity is steroids and antibacterial drugs, but [...] Read more.

(1) Background: The epidermal growth factor inhibitors (EGFRIs)/tyrosine kinase inhibitors (TKIs) are effective for cancer target therapy, but acneiform rashes or so-called inflammatory papulopustular exanthemas are common (50% to 90%). The conventional therapy for EGFRIs/TKIs-induced skin toxicity is steroids and antibacterial drugs, but it is still ineffective for some patients, and EGFRIs/TKIs dose reduction/interruption may be needed. In this study, a modified Chinese herbal medicine, Huang-Lian-Jie-Du decoction cream with Yin-Cold (YC) medicine characteristic, was investigated for the effect on patients suffering EGFRIs/TKIs-induced skin toxicity. (2) Methods: The modified Huang-Lian-Jie-Du (mHLJD) decoction cream was made from 10 herbal medicines, including 4 major medicines (Huanglian, Huangqin, Huangbo, and Zhizi) in traditional HLJD decoction. Patients with EGFRIs/TKIs-induced skin toxicity were enrolled. Patients were excluded if they also used other cream for skin toxicity. Skin conditions were monitored by follow up every 2 weeks. The patients’ characteristics, the skin toxicities, treatment response, and adverse events were recorded and analyzed until skin problems resolved or the study ended. (3) Results: The mHLJD decoction cream and its sub-packages were stored at 4 °C before use. Thirty-four patients who had grade 1–3 skin toxicities after receiving EGFRIs/TKIs were enrolled. Seven patients withdrew or were excluded. Finally, data from 27 patients were analyzed. The mean grade of rash acneiform was significantly decreased from 2.19 (ranged 1 to 3) to 0.88 (ranged 0 to 2) after mHLJD decoction cream treatment for 4 weeks and to 0.55 (ranged 0 to 2) after mHLJD decoction cream treatment for 8 weeks. Additionally, the mean grade of dry skin was also significantly decreased from 1.57 (ranged 1 to 2) to 0.71 (ranged 0 to 1) after mHLJD decoction cream treatment for 4 weeks. The changes of skin toxicity were significant, with no obvious adverse events. (4) Conclusions: In summary, the mHLJD decoction cream provides benefits for alleviation of EGFRIs/TKIs-induced skin rash acneiform and dry skin. Additionally, no obvious side effects were found in patients using mHLJD decoction cream. Full article

(This article belongs to the Section Pharmaceutical Processes)

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32 pages, 40011 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Successful Pass Schedule Design in Open-Die Forging Using Double Deep Q-Learning

by Niklas Reinisch, Fridtjof Rudolph, Stefan Günther, David Bailly and Gerhard Hirt

Processes 2021, 9(7), 1084; https://doi.org/10.3390/pr9071084 - 22 Jun 2021

Cited by 9 | Viewed by 4084

Abstract

In order to not only produce an open-die forged part with the desired final geometry but to also maintain economic production, precise process planning is necessary. However, due to the incremental forming of the billet, often with several hundred strokes, the process design [...] Read more.

In order to not only produce an open-die forged part with the desired final geometry but to also maintain economic production, precise process planning is necessary. However, due to the incremental forming of the billet, often with several hundred strokes, the process design is arbitrarily complicated and, even today, often only based on experience or simple mathematical models describing the geometry development. Hence, in this paper, fast process models were merged with a double deep Q-learning algorithm to enable a pass schedule design including multi-objective optimization. The presented implementation of a double deep Q-learning algorithm was successfully trained on an industrial-scale forging process and converged stably against high reward values. The generated pass schedules reliably produced the desired final ingot geometry, utilized the available press force well without exceeding plant limits, and, at the same time, minimized the number of passes. Finally, a forging experiment was performed at the institute of metal forming to validate the generated results. Overall, a proof of concept for the pass schedule design in open-die forging via double deep Q-learning was achieved which opens various starting points for future work. Full article

(This article belongs to the Special Issue Modelling, Monitoring, Control and Optimization for Complex Industrial Processes)

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22 pages, 3208 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Modelling and Multi-Objective Optimization of the Sulphur Dioxide Oxidation Process

by Mohammad Reza Zaker, Clémence Fauteux-Lefebvre and Jules Thibault

Processes 2021, 9(6), 1072; https://doi.org/10.3390/pr9061072 - 20 Jun 2021

Cited by 3 | Viewed by 9886

Abstract

Sulphuric acid (H₂SO₄) is one of the most produced chemicals in the world. The critical step of the sulphuric acid production is the oxidation of sulphur dioxide (SO₂) to sulphur trioxide (SO₃) which takes place [...] Read more.

Sulphuric acid (H₂SO₄) is one of the most produced chemicals in the world. The critical step of the sulphuric acid production is the oxidation of sulphur dioxide (SO₂) to sulphur trioxide (SO₃) which takes place in a multi catalytic bed reactor. In this study, a representative kinetic rate equation was rigorously selected to develop a mathematical model to perform the multi-objective optimization (MOO) of the reactor. The objectives of the MOO were the SO₂ conversion, SO₃ productivity, and catalyst weight, whereas the decisions variables were the inlet temperature and the length of each catalytic bed. MOO studies were performed for various design scenarios involving a variable number of catalytic beds and different reactor configurations. The MOO process was mainly comprised of two steps: (1) the determination of Pareto domain via the determination a large number of non-dominated solutions, and (2) the ranking of the Pareto-optimal solutions based on preferences of a decision maker. Results show that a reactor comprised of four catalytic beds with an intermediate absorption column provides higher SO₂ conversion, marginally superior to four catalytic beds without an intermediate SO₃ absorption column. Both scenarios are close to the ideal optimum, where the reactor temperature would be adjusted to always be at the maximum reaction rate. Results clearly highlight the compromise existing between conversion, productivity and catalyst weight. Full article

(This article belongs to the Special Issue Modelling and Optimization of Chemical Reactors)

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14 pages, 690 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Olive Oil Dregs as a Novel Source of Natural Antioxidants: Extraction Optimization towards a Sustainable Process

by Giuseppe Squillaci, Alice Marchetti, Orsolina Petillo, Michela Bosetti, Francesco La Cara, Gianfranco Peluso and Alessandra Morana

Processes 2021, 9(6), 1064; https://doi.org/10.3390/pr9061064 - 18 Jun 2021

Cited by 3 | Viewed by 2346

Abstract

Olive oil dregs (OOD), which are an underutilized by-product from oil mills, were used for the extraction of antioxidant compounds. The residues from three oil mills located in Campania (Southern Italy) were extracted with acidified methanol, and hydroxytyrosol (HT) was the main phenolic [...] Read more.

Olive oil dregs (OOD), which are an underutilized by-product from oil mills, were used for the extraction of antioxidant compounds. The residues from three oil mills located in Campania (Southern Italy) were extracted with acidified methanol, and hydroxytyrosol (HT) was the main phenolic compound detected. Total phenolic content (TPC) and HT amount were measured. EVO Campania oil mill provided the residue with the highest TPC and HT quantities: 6.801 ± 0.159 mg Gallic Acid Equivalents (GAE)/g OOD and 519.865 ± 9.082 μg/g OOD, respectively. Eco-friendly extractions at different temperatures and times were performed on EVO Campania OOD, obtaining 9.122 ± 0.104 mg GAE/g OOD and 541.330 ± 64.087 μg/g OOD for TPC and HT, respectively, at 121 °C for 60 min. Radical Scavenging Activity (RSA), Superoxide Scavenging Activity (SSA), and Ferric Reducing Antioxidant Power (FRAP) were measured in OOD aqueous extracts. Extract prepared at 37 °C for 60 min showed the greatest RSA and SSA values (44.12 ± 1.82 and 75.72 ± 1.78, respectively), whereas extract prepared at 121 °C for 60 min exhibited the highest FRAP value (129.10 ± 10.49 μg Ascorbic Acid Equivalents (AAE)/mg). OOD extracts were able to protect sunflower oil from oxidation for 4 weeks at 65 °C. The overall results suggest that this novel residue can be usefully valorized by providing HT-rich extracts to use as antioxidant agents. Full article

(This article belongs to the Special Issue Extraction Optimization Processes of Antioxidants)

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27 pages, 88783 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Pool Boiling Performance of Water and Self-Rewetting Fluids on Hybrid Functionalized Aluminum Surfaces

by Matic Može, Viktor Vajc, Matevž Zupančič, Radek Šulc and Iztok Golobič

Processes 2021, 9(6), 1058; https://doi.org/10.3390/pr9061058 - 17 Jun 2021

Cited by 18 | Viewed by 3690

Abstract

The boiling performance of functionalized hybrid aluminum surfaces was experimentally investigated for water and self-rewetting mixtures of water and 1-butanol. Firstly, microstructured surfaces were produced via chemical etching in hydrochloric acid and the effect of the etching time on the surface morphology was [...] Read more.

The boiling performance of functionalized hybrid aluminum surfaces was experimentally investigated for water and self-rewetting mixtures of water and 1-butanol. Firstly, microstructured surfaces were produced via chemical etching in hydrochloric acid and the effect of the etching time on the surface morphology was evaluated. An etching time of 5 min was found to result in pitting corrosion and produced weakly hydrophilic microstructured surfaces with many microcavities. Observed cavity-mouth diameters between 3.6 and 32 μm are optimal for efficient nucleation and provided a superior boiling performance. Longer etching times of 10 and 15 min resulted in uniform corrosion and produced superhydrophilic surfaces with a micropeak structure, which lacked microcavities for efficient nucleation. In the second stage, hybrid surfaces combining lower surface energy and a modified surface microstructure were created by hydrophobization of etched aluminum surfaces using a silane agent. Hydrophobized surfaces were found to improve boiling heat transfer and their boiling curves exhibited a significantly lower superheat. Significant heat transfer enhancement was observed for hybrid microcavity surfaces with a low surface energy. These surfaces provided an early transition into nucleate boiling and promoted bubble nucleation. For a hydrophobized microcavity surface, heat transfer coefficients of up to 305 kW m⁻² K⁻¹ were recorded and an enhancement of 488% relative to the untreated reference surface was observed. The boiling of self-rewetting fluids on functionalized surfaces was also investigated, but a synergistic effect of developed surfaces and a self-rewetting working fluid was not observed. An improved critical heat flux was only obtained for the untreated surface, while a lower critical heat flux and lower heat transfer coefficients were measured on functionalized surfaces, whose properties were already tailored to promote nucleate boiling. Full article

(This article belongs to the Special Issue Two-Phase Flow Heat Transfer: Design, Simulation and Optimization)

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