Search Results (145)

This paper discusses the use of additional ultrasonic fuel treatment technology to reduce sulfur oxide emissions from marine diesel exhaust gases. The research was conducted on a Bulk Carrier vessel with a deadweight of 64,710 tons with the main engine YMD MAN BW 6S50ME-C9.7 and three auxiliary diesel generators CMP-MAN 5L23/30H. The exhaust gases from all engines were treated for sulfur impurities using a scrubber system. It was stated that the combined use of the exhaust gas scrubber system and ultrasonic fuel treatment technology (compared to scrubber-only exhaust gas cleaning) results in a reduction in carbon dioxide CO₂ and sulfur dioxide SO₂ emissions, along with their ratio SO₂/CO₂. The additional ultrasonic fuel treatment technology has had the most significant effect on sulfur-containing components, leading to a substantial decrease in SO₂ emissions from exhaust gases. For various operating conditions of ship diesel engines, a reduction in CO₂ emissions of 2.9–7.5% and a reduction in SO₂ emissions of 9.3–33.1% were established. This achieved a reduction of 6.3 to 23.7% in the SO₂/CO₂ ratio, a critical parameter for evaluating the performance of the scrubber system in exhaust gas cleaning, as mandated by the provisions of Annex VI of MARPOL. The requirements of the international conventions MARPOL and SOLAS were adhered to during the experiments. Full article

The maritime sector is undergoing rapid transformation, driven by increasingly stringent international regulations targeting air pollution. While newly built vessels integrate advanced technologies for compliance, the global fleet averages 21.8 years of age and must meet emission requirements through retrofitting or operational changes. This study evaluates, at environmental and economic levels, two key sulphur abatement strategies for a 1998-built cruise vessel nearing the end of its service life: (i) the installation of open-loop scrubbers with fuel enhancement devices, and (ii) a switch to marine diesel oil as main fuel. The analysis was based on real operational data from a cruise vessel. For the environmental assessment, a Tier III hybrid emissions model was used. The results show that scrubbers reduce SO_x emissions by approximately 97% but increase fuel consumption by 3.6%, raising both CO₂ and NO_x emissions, while particulate matter decreases by only 6.7%. In contrast, switching to MDO achieves over 99% SO_x reduction, an 89% drop in particulate matter, and a nearly 5% reduction in CO₂ emissions. At an economic level, it was found that, despite a CAPEX of nearly USD 1.9 million, scrubber installation provides an average annual net saving exceeding USD 8.2 million. From the deterministic and probabilistic analyses performed, including Monte Carlo simulations under various fuel price correlation scenarios, scrubber installation consistently shows high profitability, with NPVs surpassing USD 70 million and payback periods under four months. Full article

We surveyed the air quality conditions in 18 homes with gas stoves for PM_2.5, CO₂, NO₂ and CO using calibrated low-cost sensors. In each home, participants were asked to cook as usual, but to record their cooking activities and mitigation efforts (windows, ventilation fans, etc.). All homes showed enhanced pollutants during, and immediately after, times of cooking or stove use. For each home, we quantified the minutes per day and minutes per minute of cooking over known health thresholds for each pollutant. On average, homes exhibited 38 min per day over one or more of these thresholds, with PM_2.5 and NO₂ being the pollutants of greatest concern. Six homes had much higher occurrences over the health thresholds, averaging 73 min per day. We found an average of 1.0 min over one or more of the health thresholds per minute of cooking when no mitigation was used, whereas when mitigation was used (filtration or vent fan), this value was reduced by 34%. We further investigated several mitigation methods including natural diffusion, a commercial HEPA filter unit, a commercial O₃ scrubber and a ventilation fan. We found that the HEPA unit was highly effective for PM_2.5 but had no impact on any of the gaseous pollutants. The O₃ scrubber was moderately effective for NO₂ but had little impact on the other pollutants. The ventilation fan was highly effective for all pollutants and reduced the average pollutant lifetime significantly. Under controlled test conditions, the pollutant lifetime (or time to reach 37% of the original concentration), was reduced from an average of 45 min (with no ventilation) to 7 min. While no commercial filter showed efficacy for both PM_2.5 and NO₂, the fact that each could be removed individually suggests that a combined filter for both pollutants could be developed, which would significantly reduce health impacts in homes with gas stoves. Full article

Air pollution threatens human health and ecosystems, underscoring the need for effective pollutant control technologies. This study aims to optimize the performance of a wet scrubber for air pollution control in removing contaminants from exhaust gases. We analyzed the airflow dynamics within a wet scrubber equipped with louvered vents shaped with the NACA 0012 and NACA 4412 airfoil series at four different angles. By analyzing the impact of the geometric configurations on the pollutant removal efficiency, the most effective vent design for enhancing the scrubber’s performance was identified. The components were modeled in Onshape CAD software, and prototypes were fabricated using 3D printing. Computational fluid dynamics (CFD) simulations were conducted using COMSOL Multiphysics 5.6 to analyze and optimize the aerodynamic behavior and the pressure distribution across the various vent configurations. The results offer information on how to improve scrubbers’ efficiency by optimizing the vent angles and how to develop effective air pollution control solutions. Full article

Palm oil mill effluent (POME), a byproduct of palm oil processing, has substantial resource recovery potential. Its rich biodegradable content supports methane (CH₄) production via anaerobic digestion, enabling renewable energy generation. Additionally, the significant water content of POME can be reclaimed for use in boiler feed, irrigation, and drinking water. However, selecting appropriate technologies to recover valuable resources from POME is challenging, particularly for the purification and upgrading of biogas. Membrane technologies offer an effective approach for transforming POME treatment from an energy-intensive process into a resource recovery system, supporting the decarbonization of palm oil production and advancing global sustainability objectives. This technique is cost-effective and ecofriendly for biogas purification and water reclamation. For biogas purification and upgrading, membrane systems offer the lowest capital and operational costs at 5.654 USD/m³, compared to other technologies, such as 6.249 USD/m³ for water scrubbers and 6.999 USD/m³ for chemical absorbers. This review primarily explores the potential of membranes for gas purification from POME and examines their integration with other processes to develop advanced systems, such as ultrasonicated membrane anaerobic systems and membrane anaerobic systems, to enhance biogas production. In addition, water reclamation from POME is discussed, with ultrafiltration membranes emerging as the most promising candidates. Proton exchange membranes, such as Nafion, are used extensively in microbial fuel cells to improve electricity generation, and this is also summarized. Finally, challenges and future perspectives are highlighted, emphasizing the broader potential of membrane technology in POME wastewater resource recovery. Full article

Rhenium metal is extensively utilized in the aerospace industry for the manufacturing of various superalloys due to its unique properties, and plays an indispensable role in the field of high technology. Rhenium resources are primarily associated with copper, molybdenum, and other metal ores. Ammonium perrhenate is predominantly derived from copper and molybdenum ore roasting flue gas scrubbers containing various impurities in the rhenium-containing contaminated acid. The complex composition of the contaminated acid renders the enrichment and purification of ammonium perrhenate more challenging, necessitating further research and development of the technology. This paper reviews the research progress in ammonium perrhenate enrichment and purification technology, encompassing chemical precipitation, adsorption, extraction, ion exchange, extraction chromatography, and recrystallization. It analyses the advantages and limitations of various methods, with the aim of providing a reference for future developments in ammonium perrhenate enrichment and purification technology. Furthermore, the paper presents a prospective view on the development of ammonium perrhenate enrichment and purification technology, focusing on the objective of obtaining more selective purification materials and more efficient purification techniques for ammonium perrhenate. Full article

Accurate performance estimation of the entrained-flow pulverized coal gasification unit is essential for production scheduling and process optimization, but these are often hindered by inaccurate or insufficient measurements in the industrial system. This paper proposes a data reconciliation-based method to address this challenge. The thermodynamic equilibrium model is employed as constraints of the gasification and quench processes, and the Particle Swarm Optimization (PSO) algorithm is applied for parameter estimation. Measured data under stable and variable operating conditions are reconciled, detecting and eliminating a 12% error in syngas flow rate at the scrubber outlet, thereby improving gasification performance accuracy. Two characteristic models concerning carbon conversion rate and the flow rate of reacted quench water are derived from the reconciled results. By combining these models with thermodynamic equilibrium models, the modified R² of offline predicted syngas flow rate exceeds 0.92, and those of syngas compositions reach 0.72–0.85. Additionally, an Artificial Neural Network (ANN) model, trained on reconciled and predicted data, is proposed for real-time performance estimation. The ANN model calculates performance metrics within 10 s and achieves R² values above 0.95 for most parameters. This method can be integrated into control systems and serves as a valuable tool for gasification process monitoring and optimization. Full article

The Wet Flue Gas Desulfurization (WFGD) process has always been an important part in the low-carbon/green power realization process of traditional power plants. Adding a turbulator to the spray scrubber can improve the desulfurization efficiency, whereas it also increases the flow resistance. In this study, a small experiment device based on a spray scrubber with a turbulator in a power plant was built on a 1:10 scale to address the problem. The influence of the flue gas flow rate and the liquid–gas ratio on the flow resistance was investigated. A mathematical model was established for the two-phase flow and the SO₂ liquid phase absorption reaction, and numerical simulations were achieved by the Fluent code. The resistance characteristics and the liquid droplet residence time were studied in detail. By fitting the experimental data, the relationship between the resistance coefficient, the Reynolds number, and the liquid–gas ratio in the tower was determined as the following: f = 0.0288 Re^0.359(L/G)^0.754. The desulfurization efficiency was calculated by adopting a user-defined function (UDF) code in a computational fluid dynamics (CFD) model, and the effects of the flue gas flow rate, temperature, and the liquid–gas ratio were analyzed. The results show that the effect of the rod-shaped turbulator on the flow resistance is much less than the effect of the liquid spray. The residence time of droplets around the turbulator is doubled. The pressure loss in the scrubber increases with the liquid–gas ratio (associated with the number of spray layer) and the flue gas flow rate. The turbulator can improve the uniformity of the flue gas velocity to some extent and increase the utilization rate of the spraying liquid, thereby increasing the desulfurization efficiency by 2.49%. Considering the operation cost, the reasonable value range of the liquid–gas ratio is 20~30. This work presents a good demonstration of combining the experiment and numerical simulations on a laboratory scale for large systems and associated components research, which is helpful for the engineering design and optimization of modern green power systems. Full article

Conventional ethanol production has limitations, including substrate and product inhibitions, which increase both energy requirements for ethanol recovery and vinasse generation. Extractive fermentation, which removes ethanol as it is produced within the fermentation vat, offers an effective alternative to reducing the inhibitory effects in conventional processes. However, an efficient method for recovering the extracted ethanol is also crucial. Thus, this study investigated an alternative ethanol production process using extractive ethanol fermentation integrated with ethanol recovery by absorption in both open and closed systems, specifically, comparing scenarios with and without CO₂ recirculation produced during fermentation. The recovery system used two absorbers connected in series using monoethylene glycol (MEG) as an absorbent. Under extractive fermentation conditions without CO₂ recirculation, the conversion of 300.0 g L⁻¹ of substrate resulted in a total ethanol concentration of 135.2 g L⁻¹, which is 68% higher than that achieved in conventional fermentation (80.4 g L⁻¹). The absorption recovery efficiency reached 91.6%. In the closed system, with CO₂ recirculation produced by fermentation, 280.0 g L⁻¹ of substrate was consumed, achieving ethanol production of 126.0 g L⁻¹, with an absorption recovery percentage of 98.3%, similar to that of industrial facilities that use a gas scrubber tower. Additionally, the overall process efficiency was close to that of conventional fermentation (0.448 g_ethanol g_substrate⁻¹). These results highlight the potential of this alternative process to reduce vinasse volume and energy consumption for ethanol recovery, lowering total costs and making it a viable option for integrated distilleries that combines ethanol production with other related processing operations. Full article

Spray scrubbers are widely used in gas purification applications and allow fulfillment of the demands of air quality norms introduced all over the world. They effectively remove harmful gases like sulfur dioxide (SO₂), nitrogen oxides (NO_x), and particulate matter from industrial emissions, reducing their impact on air quality. Moreover, by capturing greenhouse gases such as carbon dioxide (CO₂) in certain applications, spray scrubbers contribute to efforts to reduce climate change. Optimization of scrubber internal elements leads to reduced energy usage and lowered water mass flow while maintaining high pollutant removal efficiency. This makes them cost-effective in the long term. The demister is an additional device which is often used in scrubbing systems, and its main task is to prevent the water droplets from escaping through the upper part of the scrubbing chamber. In this article, the pollution (MgO particles) is introduced to the system upstream the scrubber inlet, the working fluid is air under atmospheric pressure, and water droplets are generated by a single nozzle placed inside the scrubber. Before the experimental part, a preliminary numerical analysis of gas velocity inside scrubber is performed and expectations of particle behavior are indicated. Then, the authors present the spray scrubber laboratory stand designed by them and carry out experimental research on it. Each element of the test stand is described in the article including the self-designed fluidizer, which effectively mixes MgO powder with air. The authors investigate the effect of their innovative construction of demister on separation efficiency and compare the results to the case without demister. The impact of water mass flow rate generated by the nozzle and gas inlet velocity on separation efficiency is presented for several investigated cases. The results show that demisters significantly improve the separation efficiency at lower water mass flow rates and successfully prevent water droplets from reaching the scrubber outlet. The measured separation efficiency was in the range of 80% for lower water mass flow rates up to 97% for the highest water flows. Full article

The increasing burden on shipowners and shipping companies due to environmental regulations imposed by the International Maritime Organization (IMO) has led to the adoption of various compliance strategies, including the use of low-sulfur fuel, installation of scrubbers, and the use of liquefied natural gas (LNG) as an alternative fuel. LNG is particularly prevalent in dual-fuel propulsion ships, with the IMO Type C tank being the most commonly used storage facility. The structure of the IMO Type C tank comprises a pressure vessel and supporting saddles, which can be integrated or separate systems. Despite being manufactured within specified tolerances, welding-induced deformation of the tank and saddle is inevitable since the saddle is welded directly onto the hull. In integrated tank–saddle systems, this deformation can lead to cracks in the epoxy resin, which has lower strength and stiffness, as well as burn damage to the resin and wooden blocks from welding heat. In separate tank–saddle systems, installation difficulties can arise due to interference between the fuel tank system and adjacent structures, such as insulation or the fuel preparation room (FPR), resulting from saddle deformation caused by welding. This study analyzes the sensitivity of all weld lines involved in saddle installation using the direct inherent strain (DIS) method. Based on this analysis, the initial welding deformations are evaluated in relation to the welding direction and sequence. Finally, an optimized method for saddle installation is proposed to minimize deformation. Full article

Pyrolysis is gaining recognition as a sustainable solution for biosolid management, though scaling it commercially presents challenges. To address this, RMIT developed a novel integrated pyrolysis and gasification technology called PYROCO™, which was successfully tested in pilot-scale trials. This study introduces PYROCO™ and its application to produce biochar, highlighting the biochar properties of the results of the initial trials. In addition, an energy analysis using semi-empirical Aspen Plus modelling, paired with a preliminary techno-economic assessment, was carried out to evaluate the feasibility of this technology. The results show that the PYROCO™ pilot plant produced biochar with a ~30 wt% yield, featuring beneficial agronomic properties such as high organic carbon (210–220 g/kg) and nutrient contents (total P: 36–42 g/kg and total N: 16–18 g/kg). The system also effectively removed contaminants such as PFASs, PAHs, pharmaceuticals, and microplastics from the biochar and scrubber water and stack gas emissions. An energy analysis and Aspen Plus modelling showed that a commercial-scale PYROCO™ plant could operate energy self-sufficiently with biosolids containing >30% solids and with a minimum calorific value of 11 MJ/kg. The process generates excess energy for drying biosolids and for electricity generation. Profitability is sensitive to biochar price; prices rise from AUD 300 to AUD 1000 per tonne, the NPV improves from AUD 0.24 million to AUD 4.31 million, and the payback period shortens from 26 to 12 years. The low NPV and high payback period reflect the use of a relatively high discount rate of 8%, chosen to be on the conservative side given the novel nature of the technology. Full article

For decades, studies have been conducted on the efficiency of gas purification processes with wet scrubbers, including the Venturi scrubbers, and this is the most commonly addressed issue in the field literature. The Venturi scrubber consists of a Venturi nozzle and a cyclone. The article addresses the empirical and analytical studies on the annular–mist flow regime that exists in the throat of the Venturi nozzle with a square cross-section. The uniform distribution of droplets over the cross-section area of the Venturi’s throat strongly correlates with the efficiency of the gas cleaning process using Venturi scrubbers. Due to the above, studies on the physics of the phenomena that affect the quantity of small droplets present in the core of the flow are highly justified. The influence of body forces and diffusive mechanisms impacting the number of droplets in the core flow were investigated to tackle the problem in question. Consequently, the fractions of droplets susceptible to turbulent or inertial–turbulent diffusion mechanisms can now be predicted using the outcomes of the research carried out. The droplets were divided into three fractions that differed by their sizes as follows: airborne droplets I confirm thar italic can be removed in all cases. $(d_d\le$ 10 µm), medium-sized droplets $(d_d\le$ 20 µm), and largest droplets $(d_d$ = (50–150) µm). The estimation of diffusion coefficients $\left({\epsilon }_{d,M},{\epsilon }_{d,ref}\right)$ and stopping distances $\left(s_M,s_{ref}\right)$ of all fractions of droplets was carried out with the inclusion $\left({\epsilon }_{d,M},s_M\right)$ and exclusion $\left({\epsilon }_{d,ref},s_{ref}\right)$ of the Magnus lift force $\left(M\right)$ in equations of both the droplet’s stopping distance and its diffusion coefficient. The outcomes revealed that the inclusion of the M force translates significantly to the growth in values of ${\epsilon }_{d,M},s_M$ compared to ${\epsilon }_{d,ref},s_{ref}$. Hence, it was concluded that the M force impacts the increase in the speed of the diffusion of the droplets with $d_d\ge$ 16.45 µm, which is favorable. Hence, the inertial–turbulent diffusion of larger droplets and the turbulent diffusion of medium ones seem to be supported by the M force. The local velocity gradient, which varied within the region of the flow’s hydraulic stabilization also impacted the mass content of droplets with diameter $d_d\le$ 10 µm in the core of the flow. As the flow development progressed, the number of droplets measured at n = 5 Hz varied nonlinearly up to the point where the boundary layer thickness reached the channel radius. The quantity of small droplets in the main flow was significantly influenced by turbulence intensity $\left(Tu\right)$. The desired high number of small droplets in the core of the flow (mist flow) was estimated empirically, and it was achieved when gas flows at high speed and has a mean value of Tu. The former benefits the efficiency of gas purification. Investigations on the effects of body forces of inertia of the continuous phase on the separation of droplets with diameters of a few microns and sub-microns from the flow were performed by employing two channel elbows, namely $e_4$ and $e_1$. The curved channels were subsequently mounted at the end of the straight channel ($SC{h}_2$). The curvature angle ($\alpha$) of the $e_4$ and $e_1$ equaled 90 °C and 30 °C, respectively. The number of droplets existing in the mist flow was higher in value, as desired, when the $e_4$ was used, unlike $e_1$. Two-dimensional flow fields of the mist have been obtained using the Particle Imaging Velocimetry (PIV) technique and analyzed further. Topas LAP 332 Aerosol Spectrometer was used for the determination of droplet ($d_d\le$ 40 µm) size distribution (DSD) and particle concentrations, while the Droplet Size Analyzer D Kamika Instruments (DSA) was exploited to ascertain DSD of droplets with diameter $d_d>40$ µm. Full article

In Republic of Korea, plasma scrubbers are a common technology employed in the semiconductor and display industries. However, there are numerous other types of scrubbers in use. The Intergovernmental Panel on Climate Change (IPCC) does not provide destruction and removal efficiencies (DREs) specific to individual scrubbers, only DREs specific to greenhouse gases, which makes it challenging to consider the specific effects of different types of scrubbers. The semiconductor and display industries in Korea represent a significant market share and are experiencing a steady increase in emissions, underscoring the need for research on GHG-reducing DREs to effectively manage these emissions. In this study, data on Tier 3 DREs developed based on measurements from companies subject to GHG management were collected. The findings indicated that C₃F₈ gas exhibited a comparable performance to the 2019 IPCC G/L (guideline) for plasma and combustion wet scrubbers, although it surpassed the 2006 IPCC G/L value. The catalytic scrubbers exhibited values that were comparable to the 2006 IPCC G/L, but lower than the 2019 IPCC G/L. The uncertainties were minimal for c-C₄F₈ gases, both in the absence of consideration of the scrubber type and when each scrubber type was taken into account. In contrast, the uncertainties associated with CF₄ gases were relatively high, depending on the scrubber type. Although there are differences between the greenhouse gases in question, failing to take the type of scrubber into account could result in under- or overestimates of certain emissions. Therefore, it would be beneficial to develop coefficients that take this into account, particularly where information on scrubbers by gas type is available. Full article

This work used piperazine (PZ) as a base solvent, blended individually with five amines, which were monoethanolamine (MEA), secondary amines (DIPAs), tertiary amines (TEAs), stereo amines (AMPs), and diethylenetriamine (DETA), to prepare mixed solvents at the desired concentrations as the test solvents. A continuous bubble-column scrubber with one stage (1 s) was first used for the test. Six parameters were selected, including the type of mixed solvent (A), the ratio of mixed solvents (B), the solvent feed rate (C), the gas flow rate (D), the concentration of the mixed solvents (E), and the liquid temperature (F), each one having five levels. Using the Taguchi experimental design, only 25 runs were required. The outcome data, such as the absorption efficiency (E_F), the absorption rate (R_A), the overall mass-transfer coefficient (K_Ga), and the absorption factor (φ), could be determined under steady-state conditions. The optimal mixed solvents were found to be A1 (PZ + MEA) and A2 (PZ + DIPA). The parameter importance and optimal conditions for E_F, R_A, K_Ga, and ϕ were determined separately; the verification of all optimal conditions was successful. This analysis found that the importance of the parameters was D > C > A > E > B > F, and the gas flow rate (D) was the most important factor. Subsequently, multiple-stage scrubbers were used to capture CO₂. Comparing 1 s and 3 s (three-stage scrubber), E_F, R_A, K_Ga, and φ increased by 33%, 29%, 22%, and 38%, respectively. The desorption tests for the four optimal scrubbed solutions, including multiple stages, showed that the heat of regeneration for the three scrubbers was 3.57–8.93 GJ/t, in the temperature range of 110–130 °C, while A2 was the best solvent. Finally, the heat regeneration mechanism was also discussed in this work. Full article