Search Results (18)

The drying process of microcrystalline cellulose and adipic acid particles in a cylindrical fluidized bed was investigated using the Gaussian spectral technique to monitor fluid–dynamic regime transitions associated with surface moisture loss. Pressure fluctuation signals were recorded and analyzed to assess hydrodynamic behavior. Excess moisture significantly alters the bubbling characteristics of the bed, leading to instability in the fluidization regime. The results demonstrated that the Gaussian spectral technique effectively captured these hydrodynamic changes, particularly at the critical moisture content threshold, when compared with the drying rate curves of the materials. For microcrystalline cellulose and adipic acid particles, it is reasonable to conclude that a mean central frequency above 5.75–6.0 Hz and a standard deviation exceeding 3.7–3.8 Hz correspond to a bubbling regime, indicating that the critical drying point has been reached. This approach provides a non-intrusive and sensitive method for identifying transitions in the drying process, offering a valuable tool for real-time monitoring and control. The ability to track fluidization regime changes with high precision reinforces the potential of this technique for optimizing drying operations in the pharmaceutical, food, and chemical industries. Full article

The continuous generation of agricultural, industrial, and urban waste necessitates effective waste management strategies. One promising approach is incorporating these residues as fillers in polymer composites. This study investigated the influence of coal processing-derived fillers, specifically microspheres and fluidized-bed combustion fly ash, on the structure and properties of composite rigid polyurethane foam. Polyurethane foams were produced through manual mixing and casting, with composite foams containing a combination of 5% microspheres and 5–15% fly ash by weight. The analysis of the samples investigated their structural, thermal, and mechanical properties. The samples consistently displayed predominantly pentagonal, regularly shaped cells. Infrared spectroscopy revealed no observable chemical bonding between the matrix and filler materials. Mechanical analysis was performed to evaluate the materials’ characteristics, revealing significant variations in compressive strength and Young’s modulus values. The results indicate that the addition of fillers did not impact the cellular and chemical composition of the polyurethane matrix. Furthermore, the composite material specimens were subjected to accelerated aging in a laboratory dryer and outdoor exposure in order to assess their thermal stability. This analysis revealed notable alterations in both the cellular composition and mechanical properties of the composite foam materials. Full article

This study explores the existing literature on specific energy consumption (SEC) use for paddy drying and consolidates all relevant data for comparisons across technologies. Energy consumption data for a range of drying technologies are consolidated from published literature and normalized to enable comparison. A large proportion of the source data are generated from operational performance in industrial or laboratory settings, while the remainder is derived from computer simulations. The SEC of paddy drying is driven primarily by technology type; however, operational factors (such as the system size, temperature, and airflow) and external factors (such as the local climate and paddy moisture content) also heavily influence system energy use. The results of our analysis show that the industrial drying technologies explored in this study have an average SEC of 5.57 ± 2.21 MJ/kg, significantly lower than the 20.87 ± 14.97 MJ/kg observed in a laboratory setting, which can potentially be attributed to differences in processing capacity. Multi-stage drying typically has higher energy efficiency when tempering stages are incorporated. The self-circulating design of some drying systems may provide additional opportunities for heat exchange, leading to efficient drying performance without the need for a separate tempering stage. Beyond traditional methods, we have observed a notable shift towards solar-assisted and infrared drying technologies in laboratory settings, reflecting an increasing interest in sustainable and efficient drying solutions. In summary, this review consolidates SEC data for rice drying technologies, analyzes the energy intensity and performance of each drying technology, and identifies data gaps that might be addressed in future research. Full article

In the last decade, twin-screw wet granulation became an essential technology for continuous pharmaceutical tablet production. Consequently, interest in (semi-)continuous fluidized bed drying systems as a subsequent processing unit has grown. In parallel, it has become pivotal to fully understand and control manufacturing processes in line with in the quality-by-design paradigm. Formulation-generic prediction models would enormously facilitate digitally enhanced process development and require dedicated experimental data collection and process knowledge. To obtain this knowledge, three experimental campaigns were performed in this work. Firstly, an investigation into the effect of dryer process settings on drying behavior is presented. Secondly, the effect of active pharmaceutical ingredient properties on drying was assessed by producing granules of similar particle size and porosity and evaluating their drying and breakage behavior. Finally, additional experiments with varying active pharmaceutical ingredients and drug load were conducted to increase the genericity of the data set. This knowledge can be used in mathematical process modelling. Full article

The aim of this work is to evaluate thermal behaviors and develop a soft sensor for online prediction of LOD (loss-on-drying) in the segmented fluidized bed dryer (Seg-FBD) in the ConsiGma25 line, which is regarded as the intermediate critical quality attribute for the final drug product. Preheating and drying experiments are performed and heat transfers and conductions among the Seg-FBD are evaluated based on the temperature measurements from sensors and an infrared thermal camera. A temperature distribution in dryer cells and high heat conductions in walls are found. Considerable heat transfers between the neighboring dryer cells are determined, which equal approximately 7% of the energy provided from the heated air. The cell-to-cell heat transfers are implemented into the heat transfer and drying models of the Seg-FBD. The models are calibrated successively in gPROMS Formulated Products (gFP) and the temperature and LOD errors are less than 2 °C and 0.5 wt.%, respectively. Subsequently, a soft sensor is established by combining data sources, a real-time data communication method, and the developed drying model, and it shows the capability of predicting real-time LOD, where the error of end-point LOD is within 0.5 wt.%. The work provides detailed steps and applicable tools for developing a soft sensor, and the online deployment of the soft sensor could support continuous production in the Seg-FBD by enabling visualization of process status and determination of process end point. Full article

Pre-treatments at relatively high temperatures (range 160 °C–220 °C) are currently used to transform lignocellulosics into biofuels and chemicals. In this step, several molecules with an inhibitory effect in the subsequent fermentation processes are generated. These inhibitors include low-molecular-weight molecules and lignin fragments that can be removed by water washing. However, this procedure also removes valuable soluble carbohydrates which are then difficult to recover from the diluted stream. In this work, a new method to detoxify steam-exploded substrates is reported. The procedure is based on the evaporation of low-weight acids and aldehydes, which leaves all the sugars in the solid matrix, while the cellulose hornification (an irreversible modification of the cellulose fibres that depresses the saccharification yield) is prevented by adding steam to the hot fluidizing flow stream. Two systems were tested: a 0.1 kg/batch oscillating fluidized bed and a continuous fluidized bed dryer operating downstream of a steam explosion plant with a treatment capacity of 150 kg/h. The detoxified substrates were subjected to enzymatic hydrolysis and fermentation to obtain bioethanol, with a yield that was 14% higher than that obtained from substrates detoxified with conventional methods of drying or washing. Full article

Investigations were undertaken to study the drying kinetics of pretreated and unblanched leaves of Moringa oleifera dried in a fluidized bed dryer (FBD) using nine established thin layer drying mathematical models. The statistical software tool Statistica was utilized to carry out regression analysis, and the model constants were evaluated using nonlinear regression. In nonlinear regression, the R² and reduced χ² were employed to evaluate the goodness of fit of several mathematical models to the data generated experimentally. The model with the highest R² and the lowest reduced χ² and root mean square error (RMSE) values was adjudged as best fit to the drying curves. The drying kinetics of drumstick leaves was best explained by the Midilli–Kucuk model, followed by the Logarithmic model. The R², reduced χ², and RMSE values of the Midilli–Kucuk model under fluidized bed drying varied from 0.9982–0.9997, 0.00003–0.00029, and 0.0059–0.0166 in pretreated and 0.9945–0.9961, 0.00019–0.00054 and 0.0136–0.227 in unblanched Moringa leaves dried at 50–70 °C, respectively. The diffusivity (D_eff) values ranged between 2.96 × 10⁻⁹–3.59 × 10⁻⁹ m² s⁻¹ and 2.92 × 10⁻⁹–3.04 × 10⁻⁹ m² s⁻¹, and activation energy varied from 13.67–14.07 (KJ/mol) and 13.85–14.11 (KJ/mol) for pretreated and unblanched dried leaves at 50–70 °C drying temperatures, respectively. Full article

Drying in fluidized beds is an important step in the production of powdered materials. Especially in the food and pharmaceutical industry, fluidized bed dryers are often vibrated to improve the drying process. In the current work, a continuous fluidized bed drying model is implemented in the novel, open-source flowsheet simulation framework Dyssol. The new model accounts for the hydrodynamic characteristics of all Geldart groups as well as the impact of mechanical vibration on the drying process. Distributed particle properties are considered by the model. Comprehensive validation of the model was conducted for a wide range of process parameters, different materials, dryer geometries and dimensions as well as the impact of vibration. Particle properties are predicted accurately and represent the broad experimental data well. A sensitivity analysis of the model confirmed grid independence and the validity of underlying model assumptions. Full article

This paper presents the results of research describing the thermokinetics of brown coal’s (lignite) drying process in a fountain-bubble fluidized bed dryer. The drying medium was atmospheric air of a variable temperature in subsequent tests, which ranged from 27 to 70 °C. This paper presents the results of many experimental studies for two different types of brown coal: xylite, from the Bełchatów mine, and earth, from the Turów mine. The two types of brown coal are used to assess different sized coal particles and different air drying temperatures. The functions parameterizing the moisture content of dried coal at different air drying temperatures at any given time are also presented. Full article

A high loading production in the manufacturing process of wheat germ (WG) drying is important for reducing the production costs. From a cost perspective, the drying performance become more effective in a batch process when the loading increases. The objective of this investigation was to evaluate the drying performance of WG with different loadings, from 2 to 9 kg, at 120 °C in a fluidized bed dryer. The moisture content, according to the American Association of Cereal Chemists (AACC) method, and the water activity using a thermal hygrometer were measured. The absolute humidity, diffusivity of moisture, and thermal efficiency were analyzed using a mathematical model. An analysis of the dehydration flux demonstrated a linear relationship between dehydration time and WG loading using a fluidized bed dryer. The kinetics of WG drying were observed with a simple exponential model used to match the experimental observation, indicating that the drying rate constant decreases with an increase in WG loading. A linear relationship was obtained between the WG loading and heating time (heating time = −0.212 + 0.577 × WG loading). On this basis, a process optimization was developed for industrial operation, and for predicting the drying performance of WG for industrial-scale production. Full article

Pumpkin seeds are a major agricultural waste from the fresh-cut produce industry. The objective of this study was to investigate the drying behavior of untreated, whole pumpkin seeds in a fluidized bed dryer at 50–80 °C (2.87 m/s), with a view to producing a high-quality pumpkin powder from dried seeds. Seeds were dried at 50–80 °C to an average equilibrium moisture value of 0.035 to 0.006 g H₂O/g DM (3.4 to 0.6% wb). Drying occurred in the falling rate period only and drying rate constants ranged from 0.0226 to 0.0900 1/min with corresponding diffusivity values for the first falling-rate period ranging from 4.68 to 18.63 × 10⁻¹⁰ m²/s. The activation energy (E_a)—for the first falling rate period was determined to be 43.9 kJ/mol. Of the nineteen thin layer models tested, the Alibas model could be successfully used as a general model to predict the Moisture Ratio (MR) data for all temperatures investigated. After drying, seeds were blended to produce powders, which were found to be high in fat, crude protein and fiber. Full article

In view of growing interest and investment in continuous manufacturing, the development and utilization of mathematical model(s) of the manufacturing line is of prime importance. These models are essential for understanding the complex interplay between process-wide critical process parameters (CPPs) and critical quality attributes (CQAs) beyond the individual process operations. In this work, a flowsheet model that is an approximate representation of the ConsiGma ${}^{\mathrm{TM}}$ -25 line for continuous tablet manufacturing, including wet granulation, is developed. The manufacturing line involves various unit operations, i.e., feeders, blenders, a twin-screw wet granulator, a fluidized bed dryer, a mill, and a tablet press. The unit operations are simulated using various modeling approaches such as data-driven models, semi-empirical models, population balance models, and mechanistic models. Intermediate feeders, blenders, and transfer lines between the units are also simulated. The continuous process is simulated using the flowsheet model thus developed and case studies are provided to demonstrate its application for dynamic simulation. Finally, the flowsheet model is used to systematically identify critical process parameters (CPPs) that affect process responses of interest using global sensitivity analysis methods. Liquid feed rate to the granulator, and air temperature and drying time in the dryer are identified as CPPs affecting the tablet properties. Full article

An experimental study was carried out for lignites of different places of origin, i.e., Poland, Greece, Romania and Australia, using a toroidal bed dryer. The effect of the temperature on the drying efficiency, including the loss of moisture content over time under fixed drying conditions was the subject of the investigation. The main goal was to confirm the possibility of the use of a toroidal bed as a base for a drying system that could utilize low quality heat from sources such as flue gases from a boiler and determine the optimum parameters for such a system. The conducted study has conclusively proven the feasibility of the use of low temperature heat sources for drying lignite in a toroidal bed. A moisture content of 20% could be achieved for most of the tested lignites, using the toroidal bed, with reasonably short residence times (approx. 30 min) and an air temperature as low as 60 °C. Moreover, the change of the particle size distribution, to some degree, affected the final moisture content due to the entrainment of wet, fine particles. The study also determined that the in-bed attrition of the particles is partially responsible for the generation of fines. Full article

The development of an effective drying performance of the fluidized bed dryer (FBD) is crucial to reduce drying costs. The objective of this study was to investigate the drying performance of wheat germ (WG) with different time-temperature combinations in the FBD. The WG was dried at different set temperatures of 80, 100 and 120 °C. The moisture content (MC) and water activity (WA) of WG were measured. A mathematical model was proposed to develop an optimal drying condition. The changes in the MC of WG during drying in the FBD could be divided into the decreased period, the dynamic equilibrium period and the increased period. The product temperature of 45 °C and WA of 0.3 of WG drying could be attained by different time-temperature combinations. The mathematical model, which was developed in conjunction with different time-temperature combinations, could predict the dehydration time and the condensation time of WG for optimization the drying conditions. The WG dehydration at the heating stage and the WG condensation at the cooling stage could also be evaluated by the dehydration flux and the condensation flux, respectively. The optimal drying performance of WG exists in a compromise between promoting dehydration and reducing condensation. Information obtained from the analysis of dehydration flux and condensation flux with experimental data and simulation gave the guidelines for performing an effective drying of WG in the FBD. Full article

The large amount of sago waste produced by sago processing industries can cause serious environmental problems. When dried, these residues usually have a high starch content (around 58%) and have many potential applications. In this study, the drying of sago waste using a fluidized bed dryer (FBD), which offers more advantages than other drying methods, is analyzed via computational fluid dynamics (CFD) modeling. A two-dimensional (2D) FBD model is also developed and a mesh independency test is conducted immediately afterwards. A fine mesh is selected for the CFD model and a simulation is conducted using ANSYS Fluent 17.1 software (Ansys Inc., version 17.1, Canonsburg, PA, USA). The governing and discretized algebraic equations are solved by applying the phase-coupled semi-implicit method for pressure-linked equations. Both the Eulerian–Eulerian multiphase model approach and the turbulence model are applied in the simulation due to the turbulent flow in the dryer. A velocity of 1.30 m/s and temperature of 50 °C are selected as boundary conditions based on the optimum parameter values from previous experiments. The final moisture content that we aim to achieve is 10% or a moisture ratio of 0.25 in sago waste for the purpose of animal feed, so as to prevent bacterial growth and for packaging purposes based on common industrial practice. Both the drying rate and fluidization profile are examined at air velocities of 0.6, 1.0, 1.3, 1.8, and 2.2 m/s. Based on the results, the velocity range of 1.0 m/s to 2.2 m/s is deemed suitable for the fluidization and drying of sago waste with a particle size of 2000 μm for a drying simulation of 1 h. The drying rate is further examined at air temperatures of 50 °C, 60 °C, 70 °C, and 80 °C, whereas the fluidization profile is examined at particle sizes of 200, 500, 1000, and 2000 μm. The results reveal excellent fluidization at a particle size range of 500 μm to 2000 μm and a velocity of 1.3 m/s. Full article