Packed-bed System Research Articles

04/01195 The blodesulphurization of a semianthracite coal in a packed-bed system: Cara, J. et al. Fuel, 2003, 82 (15–17), 2065–2068

04/01195 The blodesulphurization of a semianthracite coal in a packed-bed system: Cara, J. et al. Fuel, 2003, 82 (15–17), 2065–2068

Continuous Production of Pectinase by Immobilized Yeast Cells on Spent Grains

A yeast strain secreting endopolygalacturonase was used in this work to study the possibility of continuous production of this enzyme. It is a feasible and interesting alternative to fungal batch production essentially due to the specificity of the type of pectinase excreted by Kluyveromyces marxianus CCT 3172, to the lower broth viscosity and to the easier downstream operations. In order to increase the reactors’ productivity, a cellulosic carrier obtained from barley spent grains was tested as an immobilization support. Two types of reactors were studied for pectinase production using glucose as a carbon and energy source — a continuous stirred tank reactor (CSTR) and a packed bed reactor (PBR) with recycled flow. The highest value for pectinase volumetric productivity (PV=0.98 U ml−1 h−1) was achieved in the PBR for D=0.40 h−1, a glucose concentration on the inlet of Sin=20 g l−1, and a biomass load in the support of Xi=0.225 g g−1. The results demonstrate the attractiveness of the packed bed system for pectinase production.

Importance of frictional forces on the formation of cavity in a packed bed under cross flow of gas

The effect of frictional properties on cavity formation was studied. Until now, most of the researchers have proposed various correlations to predict the cavity size neglecting the effect of stresses on cavity formation. In the present study, the effect of stresses has been considered along with pressure and bed weight terms. These three forces are expressed in mathematical form and solved analytically for one-dimensional case using a force balance approach. Based on the force balance, the cavity size is predicted. Results have been compared with the experimental and published data of two-dimensional model. An excellent agreement is found. The effect of void fraction, angle of friction, velocity, etc. on the cavity size has been studied. The proposed theory is applicable to any packed bed systems. Internal angle of friction between the particles and void fraction in the bed plays an important role in the prediction of cavity size.

The biodesulphurization of a semianthracite coal in a packed-bed system ☆

The purpose of this study was to improve the desulphurization yield of a high sulphur-content semianthracite from northern Spain adapted to the process conditions of a packed-bed reactor, for which three 5-kg packed columns of coal were set up with the pH stabilized at 1.5. The process was begun by inoculating the first column with a culture obtained from micro-organisms native to the coal itself, mainly Thiobacillus ferrooxidans and Leptospirillum ferrooxidans, grown in a stirred reactor. The percolate of this column was then used to seed the second column, the percolate of which was then inoculated into the last one. The purpose was to obtain from the last column a better adapted and more active biomass which would give a better desulphurization yield for coal. Results show an increased yield from the first column to the last over the first 20 days of treatment, but the total desulphurization in the third column was less than expected, owing to a high precipitation of jarosite.

Sulfur dioxide adsorption isotherms and breakthrough analysis on molecular sieve 5A zeolite

In this study sulfur dioxide adsorption and rate were investigated on molecular sieve 5A zeolite in a packed bed system at 473 K. The experimental adsorption isotherms were compared with Langmuir, Freundlich, and Dubinin-Radushkevitch-Kaganer (DRK) adsorption isotherm models. The simple Langmuir and the Freundlich models provided a better description of sulfur dioxide sorption on molecular sieve 5A zeolite, so that a selective surface adsorption mechanism for adsorption of sulfur dioxide on molecular sieve 5A zeolite can be suggested. The breakthrough behavior for sulfur dioxide adsorption on molecular sieve 5A was also investigated in this study. The experimental breakthrough curves were compared with deactivation models proposed by Orbey et al., and the recent models of Suyadal et al. and Yas¸yerli et al. The deactivation models were found to give good agreement with the experimental results.

N-methacryloly-(L)-histidinemethylester carrying a pseudospecific affinity sorbent for immunoglobulin-G isolation from human plasma in a column system

N-methacryloly-(L)-histidinemethylester (MAH) as a pseudospecific ligand was synthesized by using methacryloyl chloride and histidine. Spherical beads with an average size of 63-75 μm were obtained by suspension polymerization of ethylene glycol dimethacrylate (EGDMA), 2-hydroxyethyl methacrylate (HEMA) and MAH conducted in an aqueous dispersion medium. The specific surface area of the beads was found to be 18.3 m2/g. Poly(EGDMA-HEMA-MAH) beads were used in the separation of immunoglobulin-G (HIgG) from aqueous solutions and/or human plasma in a packed-bed column system. HIgG adsorption capacity of the beads decreased with an increase in the flow-rate of plasma. The maximum HIgG adsorption on the poly(EGDMA-HEMA-MAH) sorbents was observed at pH 7.4. HIgG adsorption onto the poly(EGDMA-HEMA) sorbents was negligible. Higher adsorption values (up to 135 mg/g) were obtained when the poly(EGDMA-HEMA-MAH) sorbents were used from aqueous solutions. HIgG adsorption increased with decreasing temperature and the maximum adsorption achieved at 4°C. MAH incorporation significantly affected HIgG adsorption capacity (135 mg/g). Higher amounts of HIgG were adsorbed from human plasma (up to 165 mg/g). Adsorption capacities of other blood proteins were obtained as 8.7 mg/g for fibrinogen and 14.6 mg/g for albumin. The total protein adsorption was determined as 191 mg/g. The pseudospecific affinity beads allowed one-step separation of HIgG from human plasma. HIgG molecules could be repeatedly adsorbed and desorbed with these sorbents without noticeable loss in their HIgG adsorption capacity.

Investigation of Channel Formation Due to Random Packing in a Burning Waste Bed

Obtaining energy from sustainable sources such as waste and biomass has required a significant extension of combustion technology. Many of the advanced technologies are based on thermal treatment in gas-solid packed-bed systems such as gasifiers, incinerators and biomass furnaces. In this paper channel formation in a packed bed of fuel solids as a result of the random packing process has been investigated. Channelling causes a severely uneven distribution of the primary airflow through a packed fuel bed and results in poor combustion performance of the furnace. By assuming Furnas packing, a general relationship is derived between the bed porosity and the particle size distribution and the proposed methodology is tested against limited experimental data. A probability density function (PDF) of truncated Gaussian type is assumed for the random size distribution at local areas within the bed and the local bed porosity is calculated accordingly. Then by solving the fluid flow equations through the porous bed, flow rate profiles are obtained at the top surface of the bed. Two particulate systems were investigated as a function of change in bed height and pressure drop through the grate. Depending on bed height and pressure drop through the grate, maximum local flow rate at the top surface of the bed can be 1.5 ∼ 2 times higher than the minimum flow rate for the particulate system with a narrower size range (2.5 mm–18 mm) while the ratio of the maximum to minimum flow rate can reach as high as 8 ∼ 32 for the particulate system with a wider size range (0.677 mm–20 mm). Visualization of the velocity profile inside the bed reveals that flow passages are slightly curved in some areas but straight in others. The largest channel observed presents a ‘perfect’ straight passage of airflow running from the very bottom of the bed to the very top of the bed. Channelling inside a burning bed of solid waste in a large-scale travelling grate incinerator plant was also investigated using a unique in-house prototype instrument. The result shows that the combustion processes within the bed were dominated largely by the circles of formation and subsequent collapse of channels.

Fibronectin purification from human plasma in a packed-bed column system with gelatin immobilized PHEMA microspheres

Bioaffinity chromatography has a unique and powerful role that is used as a purification tool in the production of therapeutic plasma protein derivatives. In this study, a bioaffinity-ligand, i.e. gelatin, was covalently immobilized with PHEMA microspheres (150-200 μm in diameter). The affinity sorbent carrying 7.5 mg gelatin g-1 polymer was then used to separate fibronectin from human plasma in a packed-bed column system. Fibronectin separation from human plasma on unmodified PHEMA microspheres was 0.45 mg g-1, while much higher adsorption values, up to 21.8 mg g-1, were obtained with gelatin-immobilized microspheres. The fibronectin adsorption capacity of the microspheres decreased with an increase in the recirculation rate of plasma. Fibronectin adsorption increased with decreasing temperature, and the maximum adsorption achieved at 4°C (26.3 mg fibronectin g-1). Up to 94.7% of the adsorbed fibronectin was desorbed by using 2 M urea in the presence of 1 M sodium chloride as elution agent. The adsorption-desorption cycle was repeated ten times using the same affinity column. There was no remarkable reduction in the adsorption capacity of the gelatin-immobilized PHEMA microspheres.

The Efficacy of Nafamostat Mesilate on the Performance of a Hybrid-artificial Liver using a Polyurethane foam/porcine Hepatocyte Spheroid Culture System in Human Plasma

Nafamostat mesilate (FUT) is a protease inhibitor of complement activation. The present study investigates whether FUT protects porcine hepatocytes from being injured by human plasma in a multi-capillary polyurethane foam packed-bed culture system (MC-PUF) such as the hybrid-artificial liver (PUF-HAL). Human plasmas with 1 mM of added ammonia were perfused using a small-scale PUF-HAL with porcine hepatocytes. FUT was continuously infused (10 microg/ml, 50 microg/ml). The ammonia detoxification was maintained in human plasma for 24 hours and for 48 hours with FUT which suppressed the rapid increase of asparaginic acid aminotransferase (AST) and alanine aminotransferase (ALT). After 60 hours of perfusion, hepatocyte spheroids completely collapsed in the human plasma, but a small amount of hepatocyte spheroid was maintained by FUT. The effect of FUT was slightly greater at 50 microg/ml than at 10 microg/ml. Our results suggest that FUT has protective effects against porcine hepatocytes in human plasma, and our PUF-HAL using porcine hepatocytes can function in human plasma for about 48 hours with FUT.

Effects of culture parameters on the production of retroviral vectors by a human packaging cell line.

The use of retroviral vectors for human gene therapy requires the production of large quantities of high titer vector stocks. Maintaining high titers during the prolonged culture of packaging cells will require that critical parameters be controlled. The aim of this study was to determine which culture parameters critically affect the production/decay of retroviral vectors produced by the human packaging cell line FLYRD18/LNC-hB7. The stability of retroviral vectors released by this cell line was found to be temperature dependent (half-life of 6.9, 11.0, and 64.3 h when incubated at 37, 32, and 0 degrees C, respectively). Titers increased up to 10-fold when the packaging cells were cultured at 32 degrees C, compared to 37 degrees C, despite a decrease in cell yield (cell-specific titers were 20-fold higher). Virus titers were also over 10-fold higher when the packaging cells were cultured in a reduced serum concentration (1%) compared to 5%. Retrovirus production at a range of pH levels revealed a significant decrease in virus titer at pH levels below 6.8 and above 7.2, optimum titers being achieved in cultures at pH 7.2. Dissolved oxygen levels in the range 20-80% did not significantly affect titers under the conditions tested. Finally, a packed bed system containing the packaging cells immobilized on porous microcarriers was shown to sustain the production of active retroviral vectors for over 1 month, in relatively large volumes.

Biodegradation of gasoline and BTEX in a microaerophilic biobarrier.

Continuous bioremediation of gasoline-contaminated water in a packed-bed biobarrier system under oxygen-limited conditions is discussed. This study was part of an extensive effort to develop an alternative technology for the in situ bioremediation of hydrocarbons where there is a limited supply of oxygen. Protruded stainless steel pieces and granulated peat moss were used as packing material to support microbial growth in two biobarriers. The inoculum was an enrichment culture of an indigenous microbial population from a soil sample. The biobarriers' inlet gasoline concentrations and the linear liquid velocities were similar to those commonly found at in situ conditions. Gasoline removal efficiencies ranged from 94% to 99.9% in the stainless steel-packed biobarrier, and from 86.6% to 99.6% in the peat moss-packed biobarrier. Effluent gasoline concentrations below 0.03 mg/l were obtained at gasoline loading rates less than 27.5 mg/l.d in the stainless steel-packed biobarrier. The remaining fraction of gasoline in the effluent consisted mainly of three aliphatic compounds and not the aromatic compounds. Both biobarrier packings supported near complete removal of the most soluble aromatic hydrocarbons of gasoline (BTEX) under all the conditions examined. The consumption of sulfate and the presence of sulfate-reducing microorganisms suggested the presence of anaerobic metabolism during the degradation of gasoline. Up to 92% gasoline was removed during the first 3 cm of the biobarriers' length.

Adsorption of toluene on activated carbon in a packed bed

A simulation of the performance of an activated carbon packed-bed system for adsorption of toluene from air is performed. For a non-switched operation the time-varying exit toluene concentration of a 30 mm-depth bed is measured. The simulation result is compared with the measured data. The computer analysis is based on a modified solid-side resistance model which was originally proposed by Pesaran and Mills. The effects of cycle operating time, regeneration temperature and Ntu on the adsorption performance are investigated. The maximum removal and the corresponding optimum cycle time are obtained. The influence of the number of grid points on the accuracy of the numerical scheme is discussed. The effects of tortuosity factor and transfer coefficients on the adsorption are investigated.

Efficient Design of Desalination System Using Photovoltaic and Packed Bed Systems

This work presents a new way to realize continuous operation of a solar desalination system to produce fresh water using solar energy for a dual purpose. Here, solar energy is used directly as heat energy through solar radiation incident on an inverse V-shape still cover during sunlight hours. At the same time, the solar energy can be converted through a photovoltaic (PV) array into electric energy, which is stored in the battery system during sunlight hours. To realize the continuity of still operation daily and overnight, the batteries are discharged during the night at a suitable rate to feed an electric heater. The electric heater is designed to generate the required heat for desalination during the night. The heat is equivalent to that which can be absorbed during the day and that gives the temperature difference to gain evaporation and fresh water (productivity). This modified still is provided with a packed bed layer installed in the bottom of the basin to assist the system during the day and at night, i.e., this modified still will be more efficient. The quantity of heat energy during the night is adjusted to give a saline water temperature in the range that occurs in the actual solar still during sunlight hours. The performance of all components of the present still are discussed. The use of PV and packed bed systems means higher efficiency than the passive still, as the modified still produces large quantities of fresh water in August for a saline water depth of 0.01 m by using glass wool insulation 0.05 m thick and glass spheres as a packed bed with 0.0213 m bed length.

Preliminary assessment of particle flow code as a tool to assess ore pass safety

This paper reports the detailed description and validation of a fully automated, computer controlled analytical method to spatially probe the gas composition and thermal characteristics in packed bed systems. This method has been designed to limit the invasiveness of the probe, a characteristic assessed using CFD. The thermocouple is aligned with the sampling holes to enable simultaneous recording of the gas composition and temperature profiles. This analysis technique has been validated by studying CO oxidation over a 1% Pt/Al2O3 catalyst. The resultant profiles have been compared with a micro-kinetic model, to further assess the strength of the technique.

Thermal Analysis of Energy Storage in Packed Beds of Multilayer Storing Medium

Thermal analysis of energy storage in layers of various materials used as a packed bed storage system is presented. It is more economical to minimize insulation costs, to store more energy from the same input conditions, to lengthen the time of charging that the energy could be kept stored with acceptable losses, and to obtain higher storage capacity. These are the focus of this work. A cylindrical bed is formed from-three layers of different materials, equal in length, as heat-absorbing media. The bed is charged with flowing hot air in the axial direction, the hot air representing the heat source. A transient one-dimensional model is used to describe the thermal behavior of the system. The partial differential equations that govern the flow and heat transfer for both the air and the solid, constituting the bed and their boundary conditions, are driven. The numerical solution of two partial differential equations is obtained using the finite difference method through a computer program especially constructed for this purpose. The temperature field for the air and the solid are obtained, and the energy stored inside the bed is computed. A wide range of layers of storage media of different materials with different thermal properties is selected. Comparison is made between the present system and packed bed systems using one storing medium. The results show that the bed packed with different layers has higher storage capacity and there is step stratification of the temperature between the material layers. Also, the bed that includes metal material (such as steel) has a maximum storage capacity, and less considerable temperature than other beds, so such a bed can realize the claimed function.

Utilizing the macroporous packed bed for insect cell/baculovirus expression

Due to their high porosity and biocompatibility, polyurethane foam (PUF) and cellulose foam were adopted for insect cell immobilization and baculovirus expression. Spodoptera frugiperda (SF-21) cells were grown within the macroporous matrix and then infected by Autographa californica nuclear polyhedrosis virus (AcNPV) which was encoded with human interleukin-5 (hIL-5) gene. An appropriate initial cell loading density and medium circulation velocity determined from the previous study were applied in this actual cell cultivation experiments to obtain a uniform initial and final axial cell distribution. The growth of insect cells and the expression of baculovirus were successful in the macroporous packed bed systems used. The final average cell density in cellulose foam achieved was 5.2×107 cells/cm3 and 4.3×107 cells/cm3 in PUF. Under the conditions of sufficient nutrition and oxygen supplement, the average productivity of hIL-5 in cellulose foam packed bed bioreactor reached 7.2×107 unit/l-day. With 50% fresh medium replacement after viral infection, the average productivity of hIL-5 in PUF packed bed reached 8.4×107 unit/l-day, about two fold than that without any fresh medium replacement at infection.

Adsorption behavior of multicomponent protein mixtures containing alpha 1-proteinase inhibitor with the anion exchanger, 2-(diethylamino)ethyl-Spherodex.

The equilibrium binding behavior of alpha 1-proteinase inhibitor (alpha 1-PI) in the presence of human serum albumin (HSA) has been determined in packed bed systems with the anion exchanger, 2-(diethylamino)ethyl (DEAE)-Spherodex. Experimental data derived for the individual proteins were compared with the corresponding data obtained from batch adsorption studies as well as studies in which mixtures of these two proteins were loaded at different concentration ratios onto columns of the same anion exchange adsorbent. The results confirm that alpha 1-PI has a greater affinity for the anion exchanger, although competitive adsorption was observed as the inlet concentration of HSA was increased. Under these conditions, decreased binding capacities and lower dynamic adsorption rates were observed for alpha 1-PI with the DEAE-Spherodex anion exchange adsorbent. The results are discussed in terms of the influence which various contaminants that occur in multicomponent mixtures of proteins from human plasma can have on the equilibrium binding characteristics of a target protein with weak or strong ion exchange adsorbents under conditions approaching concentration overload in preparative chromatographic systems. These investigations have also addressed, as the first part of an iterative approach for the simulation of the adsorption behavior of multicomponent mixtures of human plasma proteins with ion exchange and affinity chromatographic adsorbents, the ability of noncompetitive and competitive Langmuirean models to simulate the adsorption of alpha 1-PI in the presence of different concentrations of HSA to DEAE-Spherodex.

97/01043 Coal gasifier and its operation method

Batches of wheat infested with all stages of Rhyzopertha dominica were heated in a 300 mm dia spouted bed fitted with a draft-tube to control grain and air flow paths. This apparatus combines features of pneumatic and packed bed systems. For a 16 kg batch of wheat spouted with 0.07 kg s−1 of air the time to achieve 99.9% mortality (LT99.9) decreased from 13.6 to 2.6 min as inlet air temperature was increased from 80 to 180°C. LT99.9 increased with increase in bed mass and decrease in air flow rate, and was sensitive to the type and axial position of the draft-tube. Bed temperatures corresponding to LT99.9 were in the range of 60–66°C depending on operating conditions. Some mechanical kill was also detected. Thermal contact efficiencies varied from 45 to 80% and were sensitive to operating and design parameters. The practical considerations for the scale-up of spouted bed disinfestors are discussed.

Cu(II) Binding by E. Radiata Biomaterial

Experimental studies showed that a common brown marine algae (Ecklonia radiata) can be used for the development of an efficient biosorbent material for Cu2+ removal from waste water. At pH 5.0, the uptake capacity of E. radiata for copper is 1.11 mmol g−1. The adsorption of copper increases as pH increases and reaches a plateau at pH 5. The copper uptake process was rapid, with 90% of the adsorption completed within 15 minutes. Presence of light metal ions in solution did not affect copper adsorption significantly. The presence of 5 mM of EDTA in solution completely inhibited the metal uptake while the effect of acetate, nitrate and chloride on metal uptake was marginal even at 20 mM concentrations of these ions. The dominant mechanism of copper biosorption is ion exchange involving Ca2+ and Mg2+ counter ions present in the algal cells. The feasibility of removing copper using the biosorbent in a packed bed system was also examined.

Performance of anaerobic packed-bed system with different media characteristics

The effects of media specific surface area, porosity, and pore size on the performance of upflow anaerobic packed-bed reactors (APBRs) were examined in the laboratory. The results showed that, the APBR containing media of the lowest surface area but the largest pore size and porosity, demonstrated the highest chemical oxygen demand (COD) removal efficiencies of 90% and 73% at loading rates of 8 and 16 g COD/L.day, respectively. An increase of over 40% in specific area in an APBR had not improved the removal efficiency, instead it produced 16% lower in COD removal efficiency at loading rate of 16 g COD/L.d. A study on the effects of effluent recycle indicates that the APBR having the largest pore size and porosity benefited from the recirculation. The reactor exhibited an increase in overall COD removal efficiency of 8% and a substantial decrease in effluent COD concentration of 30%. The results suggest that media pore size and porosity play a more significant role than media specific surface area in the performance of upflow APBRs.