Showing papers in "Journal of Chemical Engineering of Japan in 2003"

An overview of CO2 mitigation options for global warming -Emphasizing CO2 sequestration options

Abstract: CO2 mitigation options have been overviewed from an engineering point of view. There have been proposed a number of mitigation options, which can be divided into three categories; 1. reduction of energy intensity; 2. reduction of carbon intensity; 3. carbon sequestration. In this review paper, various mitigation options are reviewed focusing on the carbon sequestration options.A reduction in energy intensity is essentially an energy saving. A reduction in carbon intensity could be achieved by switching to energy resources with lower carbon contents. Based on the 2001 IPCC report, the mitigation potential related to energy intensity is estimated at 1, 900–2, 600 Mt-C/year in 2010, and 3, 600–5, 050 Mt-C/year in 2020, including other greenhouse gas equivalents. There are additional benefits in implementing these options; they are economically beneficial, and have no associated harmful effects. The carbon sequestration options can be divided into two categories; the enhancement of the natural sinking rates of CO2, and a direct discharge of anthropogenic CO2. The relevant sequestration options in the first category include terrestrial sequestration by vegetation, ocean sequestration by fertilization, and an enhancement of the rock weathering process. In the direct discharge options, the CO2 produced from large point sources, such as thermal power stations, would be captured and separated, then transported and injected either into the ocean or underground. Although the sequestration options are less beneficial in terms of cost per unit CO2 reduction compared to other options, technical developments in sequestration options are necessary for the following reasons; 1. A huge potential capacity for carbon sequestration, 2. carbon sequestration enables a continuous use of fossil fuels, which is unavoidable at the moment, before switching to renewable energy sources. Each sequestration option has advantages and disadvantages in terms of capacity, cost, the time scale of the sequestration, the stability of sequestered CO2, and additional environmental impacts, which depend on the location, time, and amount of sequestration. Thus, reliable evaluations of the mitigation efficiency are essential for each sequestration option upon implementation.

Effects of process parameters of the IS process on total thermal efficiency to produce hydrogen from water

Abstract: Thermal efficiency of the IS (sulfur-iodine) thermochemical hydrogen production cycle process was investigated. The heat and mass balance of the process were calculated with various operating conditions, and the effects of these conditions on the thermal efficiency were evaluated. The flowsheet of the H2SO4 decomposition designed by Knoche et al. (1984) was used. An electro-electrodialysis (EED) cell for the concentration of HI and a hydrogen permselective membrane reactor for decomposition of HI were applied to the process. Sensitivities of four operating conditions (the HI conversion ratio at the HI decomposition reactor, the reflux ratio at the HI distillation column, the pressure in the HI distillation column, and the concentration of HI after the EED cell) were investigated. The concentration of HI had the most significant effect on thermal efficiency. The difference of the efficiency was 13.3%. Other conditions had little effects within 2% of the efficiency. Effects of nonideality of the process (electric energy loss in the EED cell, loss at heat exchangers and loss of the waste heat recovery as electric energy) were evaluated. The difference of the efficiencies by the loss in the EED cell was 11.4%. The efficiency decreased by 5.7% by the loss at heat exchangers. The loss of the waste heat recovery lowered the efficiency by 6.3%. The result shows that the development of the EED cell, heat exchangers and electric recovery is effective in improving thermal efficiency. The operating conditions such as the HI concentration after the EED cell should be optimized to obtain the maximum thermal efficiency after the developments of the apparatuses. Change of the state of nonideality needs the optimization of the concentration. The thermal efficiency of the total process was 56.8% with ideal operating conditions of the EED cell, heat exchangers and high performance waste heat recovery.

Thermal Stress Analysis of PCM Encapsulation for Heat Recovery of High Temperature Waste Heat

Abstract: For efficient heat recovery of high temperatur e waste heat in the form of latent heat, the stable utilization technology of encapsulated phase change material, PCM, without leak was studied. In the experiments, lead pellets wer e selected as a PCM, then encapsulated by a nickel film based on an electr oplating method, and next wer e tested by cyclic heating for practical use. At the same time, thermal str ess model was developed, validated by the measur ed data and implemented to study the ef fect of the film thickness on the strength of capsules. The results of the cyclic test showed that the obtained PCM has enough strength by increasing the film thickness or decreasing PCM diameter. The developed stress model also well predicted the relationship between the film thickness and PCM diameter for estimating the required thickness of the Ni layer. The developed methodology will be useful for designing the encapsulation of any PCMs.

Adsorption Kinetics of Arsenic Removal from Groundwater by Iron-Modified Zeolite

Abstract: This work involves the treatment of model groundwater containing arsenic with the use of chemically modified zeolite. A finite volume stirred tank reactor was used to study the effects of the variables; sorbent grain fraction and sorbent dose, on arsenic reaction kinetics. The results are modelled using the pseudo-second order and second-order reversible rate equations. Equilibrium arsenic uptake and residual sum of squares evaluated from the two models are compared. From them, the arsenic sorption onto the active sites is consistent with a pseudo-second order mechanism. The initial sorption rate which drives the uptake rate was found to be in the same order of magnitude for all the grain fractions but decreased with an increase in the sorbent dose. Furthermore, based on the pseudo-second order mechanism, Thiele moduli were determined and their values suggested that intraparticle diffusion may play a significant role in arsenic uptake.

Design of a Complete Ethyl Acetate Reactive Distillation System

Abstract: In this paper, design of a complete reactive distillation (RD) system has been developed. The reactive distillation system in the study is the production of ethyl acetate (EtAc) via esterification of acetic acid (HAc) with ethanol (EtOH) using sulphuric acid as homogeneous catalyst. A suitable NRTL model parameter set for calculating of liquid activity coefficients has been established with excellent prediction of the compositions and temperatures for the four azeotropes in this system. In the VLE calculations, vapor association of acetic acid due to dimerization has also been considered. A reactive distillation column with an overhead decanter can be designed to achieve over 93 wt% of ethyl acetate composition at organic phase top product stream while the bottom product stream is designed to be rich in acetic acid so that it can be recycled and mixed with fresh acid make-up stream to serve as acid feed to the reactive distillation column. Since the purity of the optimum top organic product is still not good enough for the ethyl acetate product specification in industry, an additional column is designed to purify the ethyl acetate product of the reactive distillation column to over 99.5 wt%. The top draw of the second column will be recycled back to the decanter. In summary, the overall optimum design of this ethyl acetate reactive distillation system includes two columns (including the reactive distillation column and the second column), one decanter, and two recycle streams. The optimum operating condition of the overall system will also be studied to minimize the total operating cost of the overall system while meeting product specifications.

Sorption Kinetics of Arsenic onto Iron-Conditioned Zeolite

Abstract: Iron-conditioned zeolite was prepared and used in arsenic removal from groundwater at pH 7.8 ± 0.2 and temperature 293 ± 1 K. The effects of initial arsenic concentration and intermittent agitation were investigated in a batch reaction vessel. Kinetics analysis showed that the adsorption reaction between arsenic and the binding surfaces (probably hydrous ferric oxide) can be approximated by a pseudo-second order rate equation and that chemical reaction is the essential rate-controlling step. The rate constant, the equilibrium sorption capacity and the initial arsenic sorption rate were calculated. The initial arsenic uptake and equilibrium uptake increased with an increase in initial concentration. The intermittent agitation was superior in arsenic uptake, compared to continuous agitation. The external and intra-particle diffusion resistances to mass transfer slightly varied with an increase in initial arsenic concentration.

Mass Cultivation of Anaerobic Ammonium-Oxidizing Sludge Using a Novel Nonwoven Biomass Carrier

Abstract: Biological conversions of nitrogenous compounds closely resembling the chemistry of the anammox reaction were developed and maintained for approximately two years in fixed-bed, continuous-flow unit processes. Using a novel nonwoven matrix for biomass attachment, the anaerobic, autotrophic biofilm cultures were robust enough to survive occasional operational anomalies and to rebound quickly from temporary setbacks. Using a 2.7-l reactor with a hydraulic retention time of 7.5 hours, influent ammonium (NH 4 +) and nitrite (NO 2 -) concentrations of approximately 250 mg N/l, each, were successfully treated with a total nitrogen (T-N) removal efficiency of 60%. T-N and NH 4 + volumetric removal rates of 40 and 20 mg N/l.h, respectively, were maintained for a one-year period of operation, which are in a suitable range for industrial applications. Using the nonwoven material of the 2.7-l reactor as a seed for a larger 14-l reactor, a fast transition to a stable, relatively high T-N mass removal rate of approximately 300 mg/h (NH 4 -N removal, 150 mg/h) was possible. These results suggest that attached-growth processes such as employed here, with a nonwoven matrix, could serve well not only as a means of nitrogen abatement but also for mass cultivation of the slowly growing anaerobic ammonium-oxidizing cultures for use in development of new reactors.

Preparation of Alumite Support and Preliminary Activity Investigation for NO Removal in SCR-HC over Alumite Catalyst

Abstract: A novel metallic monolith support was prepared by anodization, HWT (hot water treatment) and calcination. A commercial aluminum plate was anodized to form porous alumina films in the outer surfaces of the aluminum plate. In contrast to the anhydrous and amorphous alumina formed after anodization, the alumina in the anodized film with HWT was boehmite. The calcination after HWT made the boehmite film lose its hydrate water and rearrange into γ-alumina. The HWT and calcination significantly enhanced the surface area of the support due to the formation of numerous micropores (radius The activities of Cu-Mn-CeOx/Al2O3/Al and Pt/Al2O3/Al alumite catalysts for the SCR-HC of NO by propene were investigated under oxygen-rich conditions. At low temperatures, Pt/Al2O3/Al exhibited a higher activity for NOx removal than Cu-Mn-CeOx/Al2O3/Al. However, a higher temperature (>623 K) made the activity of Pt/Al2O3/Al inferior to that of Cu-Mn-CeOx/Al2O3/Al. In comparison with Pt/Al2O3/Al, Cu-Mn-CeOx/Al2O3/Al had a lower N2O selectivity throughout the whole temperature range. The addition of SO2 inhibited the activity of Pt/Al2O3/Al, and this activity decay was reversible. On the other hand, a dramatic promotional effect of SO2 on reducing NOx was observed over Cu-Mn-CeOx/Al2O3/Al, but this influence of SO2 on the activity was irreversible.

Removal of Nitrate Anion by Carbonaceous Materials Prepared from Bamboo and Coconut Shell

Abstract: The adsorption behavior of nitrate anion was investigated from aqueous solution using activated carbon (AC) prepared from coconut shells and charcoal (CB) prepared from bamboo The adsorption of nitrate anions on these adsorbents exhibited maximum values in the region of equilibrium pH 2–4, and was explained by the adsorption of the Langmuir type The adsorption capacity and the adsorption equilibrium constant for AC were 266 × 10–1 mmol·g–1 and 272 dm3·mmol–1, respectively, and those for CB were 104 × 10–1 mmol·g–1 and 353 dm3·mmol–1, respectively, at 303 K The order of the adsorption capacity was the same as the order of their specific surface areas This suggests that the specific surface area is one of the factors that determine the adsorption ability for nitrate anions The theoretical curves calculated using these values were in good agreement with the experimental data From the obtained thermodynamic parameters, it was found that the adsorption of nitrate anions on AC and CB contributes to the hydrophobic interaction

A Simplified Reaction Model for Production of Oil, Amino Acids, and Organic Acids from Fish Meat by Hydrolysis under Sub-Critical and Supercritical Conditions

Abstract: Oil, proteins, organic acids and amino acids were produced from fish meat by sub-critical water hydrolysis. A reaction model for kinetics of sub-critical water hydrolysis was proposed to explain the generation of major products such as oil, cystine, alanine, glycine, and pyroglutamic acid in sub-critical water hydrolysis of fish meat. Since the reaction kinetics in sub-critical water hydrolysis of fish waste is complicated, a simplified model was developed. It shows relatively good agreement with the experimental results for a wide range of reaction temperatures.

Leaching Kinetics of Magnesite in Citric Acid Solutions

Abstract: The solubility of magnesite ore in citric acid, an environmentally friend and natural reagent, was investigated. The effects of reaction temperature, particle size and acid concentration were examined. The leaching rate increased with decreasing particle size and with increasing temperature. The dissolution in terms of acid concentration increased initially and then fell with increasing concentration. By testing shrinking core models for fluid-solid systems, it was observed that the dissolution of magnesite was controlled by chemical reaction. The following semi-empirical model was developed: 1 – (1 – x)1/3 = 6.4 × 107(D)–017(C)0.11e–61.35/RTt, where D is the particle size, C the acid concentration, T the reaction temperature and t the reaction time. The activation energy of the process was 61.35 kJ·mol–1.

Conversion of tar in hot coke oven gas by pyrolysis and steam reforming

Abstract: Possibility to convert the tar vapor in the hot coke oven gas (COG) to a synthesis gas was investigated. Tar condensed from an actual COG as well as model compounds such as benzene, naphthalene, and pyrene were used as the reactants. Experiments of the pyrolysis and catalytic steam reforming of the tar in a helium, a steam, and a simulated COG atmospheres were carried out. More than 80% of tar could be decomposed in several seconds by pyrolysis at temperature ≥1000°CThe coke yield reached 80% and the main gas products were methane and hydrogen. Coke deposition was reduced in the presence of steam by steam gasification of the coke. When the tar was pyrolyzed in the simulated COG, coke deposition from methane in addition to the deposition from the tar was observed at high temperature. The reverse shift reaction forming carbon monoxide and steam also occurred during the tar pyrolysis in the simulated COG. The coke formation was not reduced greatly even in the presence of the reforming catalysts.

Hydrogen Production from Rice Winery Wastewater by Using a Continuously-Stirred Reactor

Abstract: The continuous production of hydrogen from rice winery wastewater in a continuously stirred tank reactor (CSTR) was investigated. The conversion efficiency of carbohydrate increased with the hydraulic retention time (HRT), but slightly decreased with the increase of the substrate concentration. The conversion of carbohydrate followed the Monod kinetics with a maximum rate of 1.34 g/(g-VSS·d) and a half-rate constant of 0.32 g/L. The overall production rates of volatile fatty acids (VFAs) and ethanol decreased with HRT, but increased with the substrate concentrations. The key acidogenic products were acetate, propionate, butyrate, and ethanol. Biogas produced under all test conditions was composed of hydrogen (37–52%) and carbon dioxide (46–60%). The specific hydrogen production rate increased with substrate concentration, but with the decrease of HRT. The hydrogen yield was in the range of 1.02–1.37 mol/mol-hexose. This CSTR has potential for the use in the hydrogen production from rice winery wastewater.

On-line Batch Process Monitoring Using Different Unfolding Method and Independent Component Analysis

Abstract: In many industries, the effective monitoring and control of batch processes is crucial to the production of high-quality materials. Several techniques using multivariate statistical analysis have been developed for monitoring and fault detection of batch processes. Multiway principal component analysis (MPCA) has shown a powerful monitoring performance in many industrial batch processes. However, it has shortcomings that all batch lengths should be equalized and future values of batches should be estimated for on-line monitoring. In order to overcome these drawbacks and obtain better monitoring performance, we propose a new statistical method for on-line batch process monitoring that uses different unfolding method and independent component analysis (ICA). If the measured data set contains non-Gaussian latent variables, the ICA solution can extract the original source signal to a much greater extent than the PCA solution since ICA involves higher-order statistics and is not based on the assumption that the latent variables follow a multivariate Gaussian distribution. The proposed monitoring method was applied to fault detection and identification in the simulation benchmark of the fed-batch penicillin production, which is characterized by some fault sources with non-Gaussian characteristics. The simulation results clearly show the power and advantages of the proposed method in comparison to MPCA.

Separation on Aromatics and Non-aromatics by Extractive Distillation with NMP

Abstract: Vapor-liquid-equilibrium (VLE) at normal pressure for the system formed by n-heptane, benzene and N-methyl-pyrrolidone (NMP) are investigated. The results show that NMP is a good extractive solvent that reverses the volatility of the binary system of n-heptane + benzene. A UNIFAC model is selected and proved that the group interaction parameters are reliable. A modified extractive distillation (MED) process, in which a little of water is added to lower the boiling point of reboilers in aromatics recovery column, is proposed on the basis of the original extractive distillation (OED) process. The process simulation shows that the proposed process raises the yield ratio of benzene from 94.2% to 98.2%. Since the modification is not complicated, the MED process have a lasting value in industry.

Fabrication of Protein Microarrays for Immunoassay Using the Electrospray Deposition (ESD) Method

Abstract: In recent years new methods for active protein film fabrication have been rapidly developing. One of these methods is the electrospray deposition (ESD) method. This method allows the spontaneous deposition of many identical dots and has a remarkable spatial resolution as well as the ability to overcome limitations like low rates of deposition, low efficiency of substance transfer, and cross-contamination. In this study, an antibody-based protein array for high-throughput immunoassay was fabricated with the ESD method using a quartz mask with holes made by an abrasive jet technique. An antibody solution was electrosprayed onto an ITO glass and then deposited antibodies were cross-linked with a vapor of glutaraldehyde. The diameter of the spots was approximately 150 μm. The arrays were then incubated with corresponding target antigenic molecules and washed. The captured antigens were collectively detected by fluorescence and chemiluminescence. These signals were quantitatively visualized with a high-resolution charge-coupled device (CCD) detector. Sensitive (~1 ng/ml) and simultaneous detection of various antigens could be performed by enzyme linked immunosorbent assay or fluorescence immunoassay using this system.

A Reexamination of Mean Force Potentials for the Methane Pair and the Constituent Ion Pairs of NaCl in Water

Abstract: The potentials of mean force (PMFs) for the solute pairs in ambient water were reported by lots of computer simulation studies, where different simulation methods and various models were used. It turned out that the resultant PMFs are quite sensitive to both the methods and the models employed. In the present study, we selected with great care a set of molecular dynamics methods and models and then carried out the computer simulations to obtain the more reliable PMFs for methane-methane, Na + -Cl - , Na + -Na + , and Cl - -Cl - pairs in water. We will thoroughly compare the results with those of other researchers to validate the set of simulation methods and models for PMF calculation.

Restructuring and Afforestation of Hardpan Area to Sequester Carbon

Abstract: Afforestation is one of the most promising measures to mitigate global climate change because the expected carbon stock is estimated at as much as tens of tons per hectare or more. However, possible large-scale afforestation areas are limited to unused or ineffectively-used arid type lands. In the present study, a hardpan layer in Western Australia in an arid zone with no remarkable vegetation, a land type which is often found in the arid zones of the world, was blasted to produce holes and cracks for water penetration and root development. This study shows that hardpan blasting drastically accelerated root development and tree growth one or two years after planting. The blasting was done with additional CO2 emission of only one fortieth of the CO2 expected to be absorbed by trees after maturity.

Prediction of Agglomerate Size for Fine Particles in a Vibro-fluidized Bed

Abstract: A model for estimating the agglomerate size of Geldart group C powder in a vibro-fluidized bed was proposed. The agglomerate size was estimated by using the experimental value of the lower limit of gas velocity for channel breakage, ucha, and the void fraction, echa, at ucha. The force balance between cohesive force (van der Waals force) and separation force (gravity, vibration and shear force by a gas flow) was considered. The vibrational force was considered to act on the agglomerates to increase the effect of gravitational force. The calculated agglomerate size decreased with increasing vibration strength.The value of ucha decreased with increasing vibration strength for all tested group C powders in this study. The effects of particle properties such as particle diameter, density and material on ucha were discussed. It was found that a higher value of ucha was obtained when the cohesive force was large in the cohesive-separation force balance. This indicates the particle properties affect the cohesive–separation force balance.

High Tar Reduction with porous-particles for Low Temperature Biomass Gasification : Effects of Porous Particles on Tar and Gas Yields during Sawdust Pyrolysis

Abstract: Production of tar constitutes one of the most pressing challenges in the development of low-temperature biomass gasification. As one solution to this problem, we suggest utilizing the capacitance effect of porous particles for tar-free gasification. In the present work, in order to clarify the fundamental characteristics of the capacitance effect for biomass gasification, tar yields in sawdust pyrolysis with and without porous particles were measured at 873 K and 1073 K in a lab-scale fixed bed reactor.Employment of porous particles substantially reduced the tar yield from biomass pyrolysis. Within the range studied, the tar yield without porous particles is nearly equal to the yield of carbon deposition on porous particles at 873 K. This finding indicates that porous particles can capture and hold all tar. That is, tar produced from pyrolysis is instantaneously absorbed on the surfaces of porous particles, and the residence time of tar in a gasification furnace is prolonged and then tar is pyrolyzed, carbonized and fixed on porous particles, so high tar reduction is achieved. The results of gas yield measurement show that employment of porous particles increases hydrogen yields by three times or more. There are two reasons why hydrogen yield increased. One is that the catalytic effect promotes dehydrocyclization of lower molecular weight organic gases. Another is promotion of cyclized (poly-)condensation of aromatic compounds held on porous particles. Therefore, use of porous particles is also beneficial for improving gas properties.

Statistical Process Monitoring with Multivariate Exponentially Weighted Moving Average and Independent Component Analysis

Abstract: The ever increasing number of variables measured in chemical and biological plants has led to increased emphasis on monitoring performance and fault detection in process system engineering. However, conventional T2 and squared prediction error (SPE) charts based on principal component analysis (PCA) and partial least squares (PLS) are ill-suited to detecting small disturbances resulting from process faults because these monitoring techniques only use information from the most recent samples. In this paper, a new statistical process monitoring algorithm is proposed for detecting process changes resulting from small shifts in process variables. This new algorithm is based on the multivariate exponentially weighted moving average (MEWMA) monitoring concept combined with independent component analysis (ICA) and kernel density estimation. ICA is a recently developed statistical technique for revealing hidden, statistically independent factors that underlie sets of measurements. In this research, three monitoring charts (I2, Ie2 and SPE) obtained using a combination of ICA and MEWMA are developed to better monitor processes undergoing small mean shifts with autocorrelation, where the control limits for these statistics are obtained by kernel density estimation. The proposed monitoring method is applied to fault detection in both a simple multivariate process and the simulation benchmark of the biological wastewater treatment process (WWTP). For a small shift in these processes, the simulation results illustrated the monitoring power of MEWMA-ICA and ICA-MEWMA versus various existing methods (conventional PCA, ICA, MEWMA-PCA and PCA-MEWMA monitoring).

Thermogravimetric Evaluation for Pyrolysis Kinetics of Styrene-Butadiene Rubber

Abstract: The pyrolysis kinetics of styrene-butadiene rubber (SBR) was studied by the kinetic model which accounts for the thermal degradation of polymer at any time. The kinetic analysis was performed by a conventional nonisothermal thermogravimetric (TG) technique at several heating rates between 10 and 50 K/min in a nitrogen atmosphere. To verify the effectiveness of the kinetic analysis method used in this work, the kinetic analysis results were compared with those of various analytical methods. The TG data were also compared with values calculated by using the kinetic parameters obtained from this work. It was found that the kinetic analysis method used in this work gave the reliable kinetic parameters of SBR pyrolysis.

Continuous production of organic acids from palm oil mill effluent with sludge recycle by the freezing-thawing method

Abstract: The performance of the anaerobic treatment of palm oil mill effluent for organic acids production at a short retention time of less than 5 days was assessed by incorporating a sludge recycle system with no pH control except by adding calcium carbonate. The system could be operated successfully for a 3.5-day retention time at pH 5. The sludge solids in the treated effluent were separated by a freezing-thawing technique and it was partly recycled back to the reactor. The thawed clarified POME solution contained a low SS of 2,200–3,500 mg/L. The organic acids production with a concentration of 10–14 g/L was essentially similar to the treatment for a 5-day retention time without a sludge recycle. Hence by incorporating a sludge recycle system with the freezing-thawing method, the retention time for the treatment could be reduced without affecting the organic acids generation.

Effect of Perforated Plate on Concentration of Poly(vinyl Alcohol) by Foam Fractionation with External Reflux

Abstract: Foam fractionation of poly(vinyl alcohol) with external foamate reflux was carried out with a perforated plate foam column. The insertion of perforated plates significantly decreased the liquid distributed in the foam. Consequently, the enrichment factor in the perforated plate column was twice as much as that in the normal foam column. The maximum enrichment factor of about 25 and separation factor of about 160 were obtained at an aeration rate of 300 cm3/min and initial PVA concentration of 1000 g/m3. The insertion of perforated plates was concluded to be effective for enrichment of surface active material through foam fractionation with external foamate reflux.

Tar Capture Effect of Porous Particles for Biomass Fuel under Pyrolysis Conditions

Abstract: In the low temperature gasification of wood biomass, fluidized beds may exhibit defluidization problems caused by tar. These problems may be avoided by using porous particles as a bed material to capture the tar. Using wood chips, we studied the tar capture behavior of various porous particles and the influence of fluidization on the tar capture performance under pyrolysis conditions. The results of thermobalance experiments showed that γ-alumina, sepiolite and activated clay had high tar capture performance. The tar capture depended on the specific pore surface area and pore volume of the particles, with particles having higher pore surface and volume showing greater tar capture. Furthermore, micropores in the particles were used for capture of the tar, and this promoted carbonization. The results of a small fluidized bed experiment showed that porous particles were able to capture the tar even under fluidized bed conditions, and that defluidization did not occur at a low weight ratio of the wood chip to the bed material.

Compound heat transfer enhancement by a combination of a helically ribbed tube with twisted tape inserts

Abstract: An experimental investigation on compound heat transfer enhancement by a combination of a helically ribbed tube with twisted tape inserts was performed. The measurement of heat transfer coefficient as well as the pressure drop was performed in order to evaluate the performance of enhanced tubes using the equal pumping power evaluation method. The heat transfer coefficient was obtained by means of Wilson’s method for the Reynolds number ranging from 300 to 30,000. The combination of smoothed tube and twisted tape having a clearance NDC = 0.07 accomplished the highest performance in the laminar region. On the other hand, the combination of helically ribbed tube and twisted tape having a clearance NDC = 0.02 gave the highest performance in the turbulent region. The reasons for these results are discussed well in terms of the compound effect and clearance effect.

Study on a Regenerative Fuel Reformer for a Zero-Emission Vehicle System

Abstract: A zero-emission fuel cell vehicle system using a thermally regenerative fuel reformer, which had a performance of carbon dioxide fixation from a reformed gas, was proposed. A packed-bed regenerative reforming reactor containing a reforming catalyst and calcium oxide was examined for methane steam reforming under atmospheric pressure. It was demonstrated that carbon dioxide was well fixed by chemical absorption of calcium oxide in a preliminary experiment. The methane reforming, carbon monoxide shifting and calcium oxide carbonation proceeded simultaneously in the regenerative reactor. The carbonation of calcium oxide fixed the carbon dioxide generated through the reforming, and the hydrogen purity of effluent gas was raised beyond the equilibrium amount of a conventional fuel reformer. The vehicle system was expected to improve the efficient utilization of surplus thermal energy and surplus electricity by utilizing them for the regeneration of the reformer.

Characteristics of Phosphate Ion Adsorption-Desorption onto Aluminum Oxide Hydroxide for Preventing Eutrophication

Abstract: Human and industrial activities have recently lead to problems in regard to the eutrofication of isolated bodies of water due to influx of phosphate ions from industrial and domestic wastewater. Various methods have been developed for the removal of phosphate ions. And in particular, adsorption allows efficient and inexpensive recovery of phosphate ions in which the adsorbant and adsorbate are regenerable. In this study, investigations were carried out regarding the production of aluminum oxide hydroxide and granular aluminum oxide hydroxide, the adsorption and desorption capacities of these substances with respect to phosphate ion, and desorption efficiency and phosphate ion recovery levels obtained using sodium hydroxide and sodium carbonate. Adsorption and desorption were repeated 50 times in order to evaluate the effectiveness of aluminum oxide hydroxide, and it was determined that the adsorption performance of aluminum oxide hydroxide and granular aluminum oxide hydroxide with respect to phosphate ions is highly relative to aluminum oxide. The quantity of phosphate ions adsorbed was seen to decrease with repeated use of aluminum oxide hydroxide. The adsorption mechanism for phosphate ions onto aluminum oxide is conjectured as involving the presence of active hydroxyl groups contributing to ion exchange at the surface of the aluminum oxide hydroxide, ion exchange with phosphate ions, and the chemical bonding of hydroxyl groups with phosphate ions. It was thus clarified that aluminum oxide hydroxide is suitable for use as an adsorbant for the recovery of phosphate ions. Moreover, the investigations suggested that this material would be useful for preserving phosphate ion resources by recovering phosphate, a cause of eutrophication, as a value-added sodium phosphate product.

Modeling of Cross-Flow Microfiltration of Fine Particle/Macromolecule Binary Suspension

Abstract: The cross-flow microfiltration of fine particle/macromolecule binary suspension is analyzed and modeled in this study. The filtration rate, the cake thickness and the rejection of macromolecules can be estimated from the operating variables by modeling the cake formation, the concentration polarization and the penetration of macromolecules through the filter cake. Based on the force balance model, the thickness of the filter cake formed by fine particles can be related to the operating conditions. The formed cake plays the major roles on the filtration resistances and on the rejection of macromolecules. A reversible concentration polarization layer is constructed with the macromolecules near the cake surface. The concentration profile in this layer can be calculated using the mass transfer equation once the mass transfer coefficient is obtained from the analogy analysis. The standard capture equation for depth filtration is adopted to simulate the retention and the penetration of macromolecules in the filter cake. Experiments are carried out using the binary suspensions prepared by polymethyl methacrylate (PMMA) particles and the Dextran macromolecules. The filtration rates, the rejection of Dextran and the cake properties under various operating conditions are measured and discussed. The predicted values using the proposed models agree fairly well with the experimental data under various operating conditions.

Preparation Characteristics of Lipid Microspheres Using Microchannel Emulsification and Solvent Evaporation Methods

Abstract: Using a novel microchannel (MC) emulsification method, we are able to form microspheres (MS) with narrow size distributions. MC emulsification and subsequent solvent evaporation were performed to prepare micron-scale lipid MS with relatively narrow size distributions. The experimental systems with hexane as the dispersed-phase solvent stably formed oil-in-water (O/W)-MS with average diameters of 10–11 μm and coefficients of variation below 8% from the uniformly sized channels. The sodium dodecyl sulfate- and pentaglycerol monolaurate-containing systems performed the successful MC emulsification. Lipid MS with average diameters of 1–3 μm and coefficients of variation of about 20% were obtained through successive solvent evaporation of the formed monodisperse O/W-MS composed of 0.1–1.0 vol% tripalmitin in hexane. The diameters of the resultant lipid MS corresponded well to their estimated diameters, regardless of the tripalmitin concentration.