Increasing Bed Height Research Articles

Engineering Optimization of Producing High-Purity Dichlorosilane in a Fixed-Bed Reactor by Trichlorosilane Decomposition.

High-purity dichlorosilane (DCS) is an important raw material for thin film deposition in the semiconductor industry, such as epitaxial silicon, which is mainly produced by trichlorosilane (TCS) catalytic decomposition in a fixed-bed reactor. The productivity of DCS is strongly dependent on the controlling of the TCS decomposition reaction process, associated with the cost in practical application. In this study, we have performed computational fluid dynamics (CFD) simulation on the TCS decomposition reaction kinetics in a cylindrical fixed-bed reactor, in which the effects of catalyst bed height, feed temperature, and feed flow rate are stressed to predict the conversion rate of TCS and the generation rate of DCS. This indicates that the increase of bed height helps the reaction to proceed adequately, but too large a bed height does not improve the DCS generation rate. Meanwhile, the feed temperature and reactor temperature have important effects on the DCS generation rate. However, it is found that changing the feed flow rate and L/D ratio cannot effectively improve the DCS generation rate while the bed volume remains constant. Furthermore, we have designed a fixed-bed reactor to verify the simulation results, which are in good agreement with each other. These results are of significance for the practical industrial production of high-purity DCS in a fixed-bed reactor.

Citric acid functionalized chitosan hydrogel beads for enhanced Cr(VI) removal: Experimental assessment and COMSOL modelling of adsorption in a fixed-bed system

Chitosan hydrogel beads (CHB) and cross-linked CHB functionalized with tricarboxylic citric acid (CA-GLA-CHB) were synthesized and used for the removal of Cr(VI) from aqueous solutions in batch and dynamic adsorption systems. Applicability of COMSOL Multiphysics software as a tool for predictive modelling of column dynamics using a minimum set of experimental parameters was tested and compared with experimental results. Batch experiments demonstrated that CA-GLA-CHB showed almost 20% higher adsorption capacity and wider operational pH range compared to non-functionalized CHB. In a dynamic system, CA-GLA-CHB was used as column packing material and the column dynamics was investigated at different conditions. The breakthrough and exhaustion time of the column increased with an increase in bed height and a decrease in feed flow rate and initial Cr(VI) concentration. Computational modeling by COMSOL software with implemented Advection-Dispersion-Reaction (ADR) equation was used to simulate breakthrough curves for the applied dynamic system in order to validate the possibility of its application for process design in the scaled-up fixed-bed column systems for wastewater treatment. The simulated breakthrough curves of Cr(VI) adsorption matched well with the experimental, thus proving that COMSOL Multiphysics software can be used for scaling-up fixed-bed column systems packed with low-cost and effective CA-GLA-CHB bioadsorbent.

Morphological properties of two-dimensional and three-dimensional bedforms in open channel flow: A flume experiments study

Bedforms are formed by sediment particles under the action of flow, which in turn affect flow and sediment movement. However, the fundamental mechanisms behind the formation and development of bedforms under varying flow conditions, the interconnection between sediment particle movement and bed morphology development, as well as the influence of bedforms on flow and sediment transport, are still not well understood. In the current study, the moveable bed load transport flume experiments under different flow conditions were done, and the development processes of two-dimensional and three-dimensional dunes formed under different flow intensities were simulated. The detailed structure of the bedforms was measured by laser scanning technology, the characteristics of the bedforms were analyzed in detail, and the relations between the formation of the bedforms and the movement of sediment particles are discussed. The results found that the correlation coefficients of the longitudinal profile curve can serve as a quick reference for distinguishing two-dimensional and three-dimensional dunes. When the crestline ratio is used as the criterion for two-dimensional and three-dimensional dunes, the relative amplitude of the dune crestline and the included angle with the flow direction should also be comprehensively considered. The lee side angles of dunes calculated using the triangle generalization method and local section tangent method are compared and show that the values obtained by the former method are only about half of that of the latter. It is also found that the lee side angles of dunes are related to the dune height. The superimposed dunes generally exist in the downstream area of the stoss side of the dunes. The local bed slopes on the stoss side of the dunes show reverse slopes. The superimposed dunes improve the local bed height and further increase the reverse slope degree of the stoss side. A streamwise ridge is an important form located in the upstream area of the dunes stoss side, and they are symmetrically distributed on both sides. Multiple streamwise ridges divide the stoss side of the dunes into relatively independent movement areas, restricting the movement of sediment particles to specific regions. According to the distribution characteristics of bed morphologies, the effects of dunes on sediment particle movement and flow energy consumption are analyzed.

Adsorptive removal of a nitrate ion from the aqueous solution of sodium nitrate by application of double fixed-bed column

This study focuses on the removal of nitrate ions from aqueous solutions using rice husk activated carbon (RHAC). The RHAC was subjected to characterization via Fourier transform infrared (FTIR), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and X-ray florescence (XRF) to ascertain its functional groups, surface morphology, and oxide/elemental composition, respectively. Batch experiments were conducted to assess the impact of nitrate concentration, bed height, and number of packing layers on removal efficiency. FTIR spectra revealed favorable sorption-related functional groups within RHAC, while SEM analysis indicated the presence of effective sorption sites on its surface. EDS analysis of the rice husk adsorbent before adsorption (RHBS) demonstrated a significant composition of Si (42.20%), O (35.30%), and Ca (12.33%). The batch study unveiled a concentration-dependent decrease in nitrate removal efficiency, alongside the enhanced performance with increased bed height and number of packing layers. Kinetic data fitting favored the Yoon–Nelson and Adams–Bohart models. Overall, RHAC exhibited efficient nitrate ion removal, with column performance notably improved by utilizing multiple packing layers. These results will enhance our understanding of the mechanisms involved in removing nitrate ions and highlight the potential effectiveness of RHAC, especially when utilized with multiple packing arrangements in column setups.

Influence of packing height on the pyrolysis products of Jimsar (China) oil shale

AbstractThe effect of particle packing height (10, 30, 50, 70 mm) on the yield and composition of oil shale pyrolysis products is investigated. The results show that the oil yield could decrease 1.0% and the noncondensable gases yield could increase 0.5% as the oil shale packing height increased from 10 to 70 mm. The main hydrocarbon gases are C1–C6 gases, and the increase of packing bed height could decrease the relative content ratio of alkanes to alkenes in hydrocarbon gases. The primary components of the derived oil are aliphatic compounds, aromatic compounds, and compounds containing heteroatoms in the carbon atoms range of C6–C28. And the hydrogen type of shale oil is mainly composed of methylene groups (about 70%) with longer alkyl chains, and CH3 in aromatics, cycloalkanes, and alkanes. The chemical composition and hydrogen type have certain regularity changes with the changing of packing height, attributing to the effect of temperature gradients between surface and center of packing bed, and the diffusing time of products through the packing bed.

Fixed Bed Column Adsorption System for the Removal of 2,4-Dichlorophenoxyacetic Acid Herbicide from an Aqueous Solution

The intensive use of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide has resulted in the presence of its residues in the environment, which leads to contamination of surface and groundwater. In this study, a fixed-bed column experiment was conducted for the removal of 2,4-D from an aqueous solution using termite mound soil (TMS). Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), atomic absorption spectrometry (AAS), and Brunauer–Emmett–Teller (BET) techniques were used to characterize the adsorbent. The effect of significant variables, such as the initial 2,4-D concentration (50 mg/L and 75 mg/L), flow rate (2.5 ml/min and 5 ml/min), solution pH (2, 4, and 6), and bed height (3, 6, and 9 cm), on the breakthrough characteristics of the adsorption system was assessed. In addition, the Thomas and Yoon–Nelson models were applied to predict the breakthrough curves and to determine the characteristic parameters of the column that are useful for process design. The findings showed that at a lower pH (2), a lower flow rate (2.5 ml/min), a lower 2,4-D concentration (50 mg/L), a higher bed depth (9 cm), and 840 min breakthrough time, a higher removal percentage (80.2%) of 2,4-D was achieved. The experimental data were in good agreement with the Thomas and Yoon–Nelson models. For the Yoon–Nelson model, the rate constant increased with an increase in the flow rate, initial ion concentration, and bed height. The time required for a 50% breakthrough decreased with an increase in the flow rate, bed height, and initial ion concentration. For the Thomas model, the rate constant increased with an increase in the flow rate but decreased with an increase in bed height and initial concentration. Overall, the study showed that termite mound soil in a fixed-bed column adsorption system presents an excellent potential for removing 2,4-D from aqueous solutions.

Bulking agent in dry anaerobic digestion as a key factor for the enhancement of biogas production

Dry anaerobic digestion (dry-AD) is an attractive process for solid wastes such as agri-food waste. However, some limitations mainly associated to lack of effective mixing, can hinder the methane production capacity of the systems. Bulking agent (BA) has been proposed as a solution to the compaction issues in systems without mechanical agitation, such as leaching bed reactors. However, effects of BA are still not clear, and, thus, the factors to consider for its dose has not been optimized yet. This work studies the effect of BA in dry-AD. Two substrates with different characteristics were proposed as models, bean peel as a lignocellulosic substrate and a mixture of food waste as a readily biodegradable substrate. Inert plastic rings were used as BA at different BA:S ratios. Assessed BA:S ratio did not affect the performance of methane production for the lignocellulosic waste, but it did significantly affect to the easily biodegradable substrate, showing up to a 28% of methane production increase. This result could be due to the presence of lignocellulosic compounds in the bean peel, behaving like a natural BA. In assays with an increased bed height, the compaction of the system was more severe, resulting in the rapid acidification of the processes. At these conditions, the positive effect of BA addition was more marked, allowing methane production and no acidification of the system. Thus, the addition of BA is a suitable strategy for improving methane production or stability in dry-AD systems without requiring the stirring of the systems.

Power-efficient mass transfer of a novel pulsating multi-packed bed liquid - liquid extractor

This paper presents the development and performance evaluation of a new pulsating packed bed contactor designed for optimized diffusion-controlled liquid-liquid operations. Targeting applications like aromatics separation in petroleum, phenol removal from wastewater, and heat-sensitive material extraction (e.g., antibiotics), the contactor offers substantial advantages over traditional mechanical systems – notably, lower power consumption for equivalent production rates. Using the widely studied extraction of acetic acid from toluene-acetic acid by water as a model system, this work comprehensively investigates the factors impacting mass transfer within the pulsating contactor. Key variables explored include physical properties of the feed solution, oscillation frequency and amplitude, initial concentration of solute, flow rates, bed height, packing diameter, and bed spacing. Results reveal a significant enhancement in mass transfer with increasing frequency, amplitude, initial concentration, continuous phase flow rate, and dispersed phase flow rate. Interestingly, while increasing bed height initially improves mass transfer up to a specific point, further height increase exhibits a diminishing return. Packing sphere diameter shows minimal impact, while bed spacing has a negligible effect. A novel dimensionless equation effectively correlates the pulsating multi-packed bed data for broader applicability. To assess economic viability, the study also measures the mechanical power consumption under various operating conditions. Finally, diverse potential applications across pharmaceuticals, chemicals, biochemicals, petroleum, and nuclear fuel reprocessing are highlighted, showcasing the broad utility of this innovative mass transfer technology.

Estimating the percentage effects of Bemacid red dye adsorption dynamic parameters using a full factorial design approach

Abstract In this study, we investigate the removal of Bemacid red dye using brewery waste in a packed bed column. We examined the effects of bed height, inlet flow, and inlet dye concentration on the column dynamics of adsorption. To assess the favorable column dynamics, we analyzed the breakthrough curves (BTCs). We also used the Clark, Thomas, Bed Depth Service Time (BDST), and Adams-Bohart models to determine the kinetic constants of the adsorption column from the obtained results of the dynamic studies curve of the BTCs. Analysis of the BTC studies revealed that both the BTCs time and worn-out time values increased with an increase in bed height and inlet Bemacid red dye dosage but decreased with an increase in the inlet flow rate. The results further showed that Thomas’ model was the most suitable for describing the entire BTCs (R2 > 0.93). Using a full factorial design to estimate the percentage effects of cited dynamic parameters, we found that these parameters accounted for 98% of the adsorption capacity. This methodology for estimation provides crucial information on the effects of parameters and the extent to which the adsorption capacity depends on the studied parameters.

Bone Char Adsorption of COD and Colour from Tannery Wastewater: Breakthrough Curve Analysis and Fixed Bed Dynamic Modelling

This study delves into the simultaneous adsorption of chemical oxygen demand (COD) and colour from tannery wastewater using bone char through a fixed bed column. The bone char, which was derived from cattle skulls, was characterised using the Fourier transform infrared spectroscopy, Braeuer–Emmett–Teller surface area analysis, and the scanning electron microscope/energy-dispersive X-ray spectroscopy. The effects of different process conditions, specifically, packed bed height (5, 10, and 15 cm) and flow rate (2, 5, and 8 mL/min), on the adsorption efficiency of the fixed bed column were assessed through breakthrough curve analysis. The results revealed that the efficiency of the column bed enhanced with increasing bed height and declined with increasing wastewater flow rate. The optimal operating conditions for COD and colour removal onto the bone char occurred at 15 cm bed height and 2 mL/min flow rate. The adsorption capacities at these conditions were 227.4 mg/g and 53.03 Pt-Co/g for COD and colour, respectively. The kinetics associated with the fixed bed adsorption of COD and colour onto bone char were elucidated through the fitting of the Thomas, Adams–Bohart, and Yoon–Nelson models to the experimental data. Among the three models, the Yoon–Nelson model gave the best prediction of the experimental data. Maximum adsorption efficiencies of 80.65% and 84% were attained for COD and colour removal, respectively, proving that bone char is a promising and ecologically friendly alternative adsorbent for the treatment of tannery wastewater.

Assessment of dynamic characteristics of fluidized beds via numerical simulations

Euler–Lagrange simulations coupled with the multiphase particle-in-cell (MP-PIC) approach for considering inter-particulate collisions have been performed to simulate a non-reacting fluidized bed at laboratory-scale. The objective of this work is to assess dynamic properties of the fluidized bed in terms of the specific kinetic energy of the bed material kS in J/kg and the bubble frequency fB in Hz, which represent suitable measures for the efficiency of the multiphase momentum exchange and the characteristic timescale of the fluidized bed system. The simulations have reproduced the bubbling fluidization regime observed in the experiments, and the calculated pressure drop Δp in Pa has shown a reasonably good agreement with measured data. While varying the bed inventory mS in kg and the superficial gas velocity uG in m/s, kS increases with uG due to the increased momentum of the gas flow, which leads to a reinforced gas-to-solid momentum transfer. In contrast, fB decreases with mS, which is attributed to the increased bed height hB in m at larger mS. An increased gas temperature TG from 20 to 500 °C has led to an increase in kS by approximately 50%, whereas Δp, hB, and fB are not sensitive to TG. This is due to the increased gas viscosity with TG, which results in an increased drag force exerted by the gas on the solid phase. While up-scaling the reactor to increase the bed inventory, bubble formation is enhanced significantly. This has led to an increased fB, whereas kS, hB, and Δp remain almost unchanged during the scale-up process. The results reveal that the general parameters such as hB and Δp are not sufficient for assessing the hydrodynamic behavior of a fluidized bed while varying the operating temperatures and up-scaling the reactor dimension. In these cases, the dynamic properties kS and fB can be used as more suitable parameters for characterizing the hydrodynamics of fluidized beds.

Continuous Adsorption of Acid Wood Dyes onto an Activated Carbon Prepared from Pine Sawdust

In this paper, an activated carbon obtained from Pinus radiata sawdust is applied to remove blue, red, and black wood dyes from aqueous solutions in a fixed-bed column. The flow rate (7.7–30.8 mL min−1), initial dye concentration (25–500 mg L−1), and bed height (2–4 cm) highly influence the breakthrough-curves’ features. The results indicate that the adsorption capacity increased by decreasing the flow rate and increasing the initial dye concentration, except for the black dye, and increasing bed height, except for the red dye. In addition, the breakthrough time changed by modifying the studied variables. The curves became steeper as the flow rate increased and as the bed height decreased. Also, by increasing the inlet dye concentration, the breakthrough time decreased significantly, and sharper breakthrough curves were obtained. The activated carbon with a surface area of 2826 m2 g−1 led to high values of the adsorption capacity between 150 and 1300 mg g−1. The Yoon–Nelson and Thomas models were the ones that best described the adsorption data. The activated carbon saturated with black dye could be used in three successive cycles after regeneration with H2O2.

Research Investigates and Simulation Behavior of the Failure Characteristics of Red Mud–Loess Type Permeable Reactive Barriers PRB in Fixed‐Bed Column Experiments

Controlling and remediating water and soil pollution while efficiently utilizing solid waste is essential for comprehensive environmental protection and sustainable development, particularly in establishing green, low‐carbon economic systems in China. We evaluate the impact of initial concentration, flow rate, and bed height on breakthrough performance and adsorption capacity using the Tessier method under dynamic water flow conditions. Additionally, we analyze micromorphological changes in the red mud–loess mixture before and after breakthrough by acid mine drainage containing Pb and Cd in mining areas, employing soil column experiments and numerical simulations with COMSOL Multiphysics. Our findings suggest that reducing initial concentration and flow rate while increasing bed height leads to higher breakthrough time, saturation time, and adsorption capacity for Pb and Cd in the red mud–loess mixture (7 : 3). Furthermore, the red mud–loess blend (7 : 3) demonstrates sustained and efficient acid‐buffering capability in the presence of acid mine drainage containing Pb and Cd. Notably, under specific conditions (initial Pb content at 100 mg/L, a height of 7 cm, and flow rate set at 1 mL/min), the adsorption capacity of red mud–loess (7 : 3) reaches 17.30 mg/g. The prescribed minimum length for PRBs is 11.40 cm. Under specified conditions (Cd concentrations at 100 mg/L, a height of 5 cm, and a flow rate of 1 mL/min), the material exhibits a notable adsorption capacity of 29.91 mg/g, with a theoretical minimum length for PRBs at 8.95 cm. Increasing bed heights successfully remove Pb and Cd ions through chemical precipitation. The BDST model accurately describes the breakthrough curves of Pb and Cd and develops a correlation formula for the breakthrough time of red mud–loess PRB medium. As the saturation of Pb increases from 0.05 to 0.85, the maximum volume adsorption capacity of Pb increases from 1.78 to 2.98 mg/L, while for Cd, it increases from 4.15 to 7.87 mg/L. Elevating the bed height first triggers chemical precipitation, hence improving Pb and Cd removal. Consequently, the longevity of red mud–loess PRB in acidic mine effluent containing Pb and Cd surpasses predicted theoretical outcomes. These observations reveal correlations between the breakthrough length for red mud–loess permeable reactive barriers and the bed height. Furthermore, the distribution of Pb speciation within the red mud–loess mixture (7 : 3) is primarily governed by the presence of iron–manganese oxide, while the composition of Cd speciation is chiefly influenced by the carbonate form and iron–manganese oxide. After treating acidic mine wastewater with Pb and Cd, the red mud–loess mixed material (7 : 3) undergoes surface changes, shifting from smooth to rough due to H+ corrosion. Pores between particles enlarge, yet heavy metal ions, adsorbates, and precipitates reoccupy and cover the surface, transforming the particle morphology from dense lamellar to clustered spherical. Our innovative approach to combining waste materials for environmental remediation presents a cost‐effective and impactful solution for heavy metal pollution.

Dynamic characteristics of pollutant emissions from CFB boilers during periodic fire banking and start-up

It is difficult to control pollutant emissions during fire banking and start-up in CFB boilers, which poses threats to power plant operation, safety and environmental protection. A 350 MW supercritical CFB boiler was taken as the research object. Using the CPFD method and Barracuda software, a full-loop combustion and pollutant emission model was constructed to simulate periodic fire banking and start-up, and the gassolid flow characteristics and pollutant emission characteristics were analysed. The results showed that the bed material at the bottom of the furnace exhibits obvious stratification after being stationary, and this stratification has an impact on the generation, distribution and emission of NOx and SO2 in the furnace. Eighty-five percent of the bottom bed material is lower layer, and the NOx and SO2 concentrations are negatively correlated with the volume fraction of particles. The average NOx and SO2 concentrations in the lower layer are 120.05 mg/m3 and 1155.50 mg/m3, respectively. During the hot start-up process, the NOx concentration decreases with increasing bed height. The residence time of the desulfurization reaction is prolonged, the desulfurization efficiency is improved, and the SO2 concentration is reduced. These results provide a theoretical basis and a certain reference value for the periodic fire banking and start-up of supercritical CFB boilers.

Spent tea waste extract as a green modifying agent of chitosan for aspirin adsorption: Fixed-bed column, modeling and toxicity studies

Aspirin is a prevalent over-the-counter medicine that has been categorized as an emerging contaminant due to its danger to both living things and the environment. This work presents chitosan modified with spent tea waste extract (STWE) via the wet impregnation method as an adsorbent for the enhanced removal of aspirin in a fixed-bed column. The adsorbent (named chitosan-STWE) was successfully synthesized and exhibited a low crystallinity structure, good stability against thermal and acidic conditions, as depicted by HNMR, XRD, TGA, and the dissolution rate of the adsorbent. The adsorption column study reveals that increasing bed height (up to 6 cm) increases the percentage of aspirin removal (up to 40.8 %). Increasing aspirin concentration enhances the amount of aspirin that comes into contact with the chitosan-STWE adsorbent, thereby increasing the adsorption capacity. On the other hand, higher flow rates result in shorter contact times between the adsorbent and adsorbates, which lowers the quantity of aspirin adsorbed. The experimental data are in accordance with the values generated by the Thomas and Yoon-Nelson models, with the maximum adsorption capacity of 61.7 mg/g. The chitosan-STWE adsorbent was determined to be non-toxic, thus safe to be used in wastewater treatment applications.

Adsorption of Acid Yellow 23 Dye on Organobentonite/Alginate Hydrogel Beads in a Fixed-Bed Column

This research evaluates the use of organoclay/alginate hydrogels in removing Acid Yellow 23 in a fixed-bed column and contributes to the application of these composites in the context of the adsorption of anionic dyes that are present in wastewater. An organobentonite (OBent) was synthesized and encapsulated in an alginate matrix, using Ca2+ ions as a crosslinking agent. Experiments in fixed-bed columns showed that breakthrough and exhaustion times were longer with increasing bed height, which decreased with increases in flow rate and initial dye concentration. The Thomas, Yoon–Nelson, and Adams–Bohart models were well fitted to the experimental data for the breakthrough curves with high Adj. R2 correlation coefficients and low values of χ2. The theoretical adsorption capacity of the organobentonite/alginate hydrogel calculated from the Thomas model was 0.50 ± 0.01 mg/g (equivalent to 30.97 mg/g OBent), and this was obtained by using a 15 cm (10.10 g) bed height, 1 mL/min flow rate, and a 45 mg/L input dye concentration. The bed was regenerated with a 0.5 M NaOH solution, and the reuse of the saturated column bed was studied for two adsorption–desorption cycles. The results obtained in this study suggest the potential use of an organoclay/alginate hydrogel for the adsorption of pollutants in continuous systems.

Perchlorate captured by activated carbon derived from dates seed through adsorption technique

<p>In the present research packed bed column with activated carbon which is derived from the natural available dates seed used for exclusion of perchlorate from aqueous sample. The effect of several variables on adsorption performance has been studied, including inlet ion concentration, flow rate, bed height, and temperature.The adsorbent was prepared in two different temperature 400℃ and 800℃ and the depth of column was 5cm and 8cm. The findings showed that the activated column at 400℃ in the depth of 5cm was saturated at 320 min and for 8cm column it is saturated at 300 min. Likewise for 800℃ columns in the depth of 5cm the treatment efficiency attained at 220 min and for 8cm column it was 180 min. It is showed that the optimal flow rate and bed height increase adsorption effectiveness. Gas chromatography (GC) was used to determine the perchlorate concentration in liquid sample after treatment process. The Thomas and Thomson mathematical models were utilized to determine the column's adsorption efficacy, with the maximum R2value of 0.985 for 800°C in an 8 cm column with a removal efficiency of 98.1%. The surface morphology was examined with SEM, FTIR and XRD which proves that the pore changes in the morphology of the adsorbent created homogeneous to heterogeneous formation structure. This comprehensive study shown that activated carbon generated from dates seed is a successful adsorbent for the removal of perchlorate at optimal temperature and bed depth</p>

Fixed bed mycofilter column optimization and performance evaluation through the removal of a food coloring agent from an aqueous solution

Mycofiltration via continuous fixed bed adsorption, helped to assess the effect of flow rate, pH, column bed height and myceliation on the sorption capacity of a mycofilter. The mycofilter (thatching straw and Pleurotus ostreatus) was cultured and loaded into polypropylene columns (2.5 × 12 cm) to bed heights of 2 and 4 cm. A food color solution was passed through at different pH (2 and 7.5) and flow rates (0.25 ml/min and 2 ml/min). The filtrate was collected and measured at time intervals. Under constant flow rate and solution pH, the 4 cm bed adsorbed 8 times the inlet amount of food color compared to 1.6 times only for the 2 cm bed. More food color was adsorbed with the higher flow rate (10 times the inlet concentration). Adsorption was only observed in the solution with pH = 2. The control filter (without mycelia) adsorbed 3-fold less than the mycofilter. The experimental data best fitted into the Thomas model (compared to the Yoon-Nelson model) which showed that an increase in bed height caused an increase in adsorption capacity (qTH), and that an increase in flow rate resulted in an increase in Thomas rate constant (KTH). FTIR analyses of the mycofilter revealed amide, hydroxyl, and chitin groups possibly involved in adsorption processes. Our fixed bed mycofilter optimally removed food color from aqueous solutions, in high bed height and flow rate, and low pH conditions.

CFD-DEM investigation of the gas-solid flow characteristics in a fluidized bed dryer

Wet granules drying in a fluidized bed is a complex process and the process involves heat and mass transfer between gas and solid phases as well as the moisture changes in the granules. CFD-DEM model was employed to investigate the wet granule flow characteristics, the heat and mass transfer process in a fluidized bed drying process. The proposed model considered the liquid bridge force varying with granule moisture content and was validated by experimental data. Due to the computational capability restriction, pseudo 2D model simulations were first employed for the whole drying process and then 3D model simulations were performed at certain moisture contents to investigate the flow dynamics in more detail. The effects of granule number and the changing liquid bridge force on the drying process were further analyzed. Granule agglomeration was generated in the drying process at high moisture content due to the liquid bridge force, which affects the fluctuations of pressure and bed height. Moreover, the heat and mass exchange between the gas and solid phases mainly occurred in the interface of bubble phase and granule phase. With the increase of bed height, the granule volume fraction decreased and the transfer coefficients between these two phases decreased.

Variation of heat load due to in-vessel debris bed in IVR condition

We performed experiments investigating the heat load imposed on the inner reactor vessel wall in the in-vessel retention of core melt condition, varying the debris bed height and configuration. Mass transfer method was adopted to achieve high RaʹH of order ∼1015 with compact test rigs. We tested three types of the debris configurations: cone, flat and skew debris beds. The results showed that Nusselt numbers decreased in both the uppermost and the curved surfaces with the increasing bed height. Due to the friction increased by the debris bed, the natural convective flow in the oxide pool was weakened, which intensified the impairment of the heat transfer. As the rising plume at the center was disturbed by the porous structure of the debris bed, the local average heat transfer of the uppermost surface was weakened at the center. The heat transfer was dramatically decreased at the curved surface where the debris bed was covered.