Korean Journal of Chemical Engineering (v.26, #2)

As the standard size of silicon wafers grows and performance specifications of integrated circuits become more demanding, a better control system to improve the processing time, uniformity and repeatability in rapid thermal processing (RTP) is needed. Identification and control are complicated because of nonlinearity, drift and the time-varying nature of the wafer dynamics. Various physical models for RTP are available. For control system design they can be approximated by diagonal nonlinear first order dynamics with multivariable static gains. However, these model structures of RTP have not been exploited for identification and control. Here, an identification method that iteratively updates the multivariable static gains is proposed. It simplifies the identification procedure and improves the accuracy of the identified model, especially the static gains, whose accurate identification is very important for better control.
Keywords: Temperature Control; Rapid Thermal Processing; Single Wafer; Iterative Identification; Nonlinear Model Identification

A comparison on predictive models of gas explosions by Dal Jae Park; Young Soon Lee (313-323).
A comparison on existing models of gas explosion predictions has been done. The advantages and drawbacks, and the possibilities and limitations of the different empirical, phenomenological, and computational fluid dynamics assessment models of gas explosions were discussed. Particular attention was paid to CFD models.
Keywords: Gas Explosions; Empirical Models; Phenomenological Model; CFD Models

The comparison study on the operating condition of gasification power plant with various feedstocks by Hyun-Min Shim; Su-Yong Jung; Hong Yue Wang; Hyung-Taek Kim (324-331).
Gasification technology, which converts fossil fuels into either combustible gas or synthesis gas (syngas) for subsequent utilization, offers the potential of both clean power and chemicals. Especially, IGCC is recognized as next power generation technology which can replace conventional coal power plants in the near future. It produces not only power but also chemical energy sources such as H2, DME and other chemicals with simultaneous reduction of CO2. This study is focused on the determination of operating conditions for a 300 MW scale IGCC plant with various feedstocks through ASPEN plus simulator. The input materials of gasification are chosen as 4 representative cases of pulverized dry coal (Illinois#6), coal water slurry, bunker-C and naphtha. The gasifier model reflects on the reactivity among the components of syngas in the gasification process through the comparison of syngas composition from a real gasifier. For evaluating the performance of a gasification plant from developed models, simulation results were compared with a real commercial plant through approximation of relative error between real operating data and simulation results. The results were then checked for operating characteristics of each unit process such as gasification, ash removal, acid gas (CO2, H2S) removal and power islands. To evaluate the performance of the developed model, evaluated parameters are chosen as cold gas efficiency and carbon conversion for the gasifier, power output and efficiency of combined cycle. According to simulation results, pulverized dry coal which has 40.93% of plant net efficiency has relatively superiority over the other cases such as 33.45% of coal water slurry, 35.43% of bunker-C and 30.81% of naphtha for generating power in the range of equivalent 300 MW.
Keywords: Gasification; Feedstock; Process Simulation; ASPEN Plus

The spatiotemporal instability on mixed convection in porous media by Tae Joon Chung; Min Chan Kim; Chang Kyun Choi (332-338).
The absolute and convective instability on mixed convection in porous media is examined, and the phase transition from the oscillatory wave motion to the stationary vortex one is observed. Based on linear and weakly nonlinear analyses, the critical conditions to mark the onset of traveling transverse rolls are analytically obtained for small Péclet numbers. The flow change from transverse wave to longitudinal vortex is reproduced by numerical simulation. These criteria made good agreement with the available experiment data.
Keywords: Absolute Instability; Convective Instability; Porous Media

Evaluation of jet performance in drop-on-demand (DOD) inkjet printing by Byoung Wook Jo; Ayoung Lee; Kyung Hyun Ahn; Seung Jong Lee (339-348).
Inkjet printing has been widely used in many applications and has been studied for many years. However, there are not many systematic researches on the mechanism of jet formation, nor is there any reliable platform that enables us to evaluate jet performance. In this study, an approach to practically evaluate the jet stability of the dropon-demand (DOD) inkjet printing has been proposed, based on which the transient behavior of the DOD drop formation has been studied experimentally for Newtonian liquids with a range of different viscosities (1.0–11 cp) but of a comparable surface tension. For more viscous liquids, the rate of the jet retraction after a pinch-off from the nozzle was found to increase as the thread motion became more sharp and conical as a result of the shape effect. The break-up time of the jet also increased because the rate of capillary wave propagation was lower for more viscous liquids. The jet stability graph, which can be drawn in terms of jet retraction and break-up time, was employed to characterize the jetting stability, and the degree of satellite drop generation was quantitatively evaluated by two critical jet speeds. The effect of an electric pulse imposed on a piezoelectric plate inside the printhead was also studied. The single-peak electric pulse was used in this experiment for simple analysis, and the jet speed variation was measured under different operating conditions. Both the optimal dwell time and the maximum stable jetting frequency were affected by viscosity and they were explained in terms of the propagation theory.
Keywords: Drop-on-demand; Inkjet Printing; Drop; Viscosity; Jetting Stability; Jetting Window

To predict the surface tension of binary liquid systems, an empirical model is proposed using the partial least squares (PLS) based on the multivariate statistical analysis method. Required parameters for the PLS method to predict the surface tension of binary systems are composed of the thermophysical properties of only pure substances such as critical temperature, critical pressure, critical volume, molar volume, viscosity and vapor pressure for input data block (X) and the reported experimental surface tension data for output data block (Y). The data set for the experimental surface tension of binary liquid systems is divided into the training set for regression and the test set for predicting. An average relative error (%) results of regression and prediction indicate that the PLS method can be a useful tool for predicting the surface tension of liquid binary systems.
Keywords: Surface Tension; Partial Least Squares; PLS; Multivariate Statistical Analysis; Binary System

Onset of Soret convection in a nanoparticles-suspension heated from above by Min Chan Kim; Lae Hyun Kim; Do-Young Yoon (354-358).
The onset of Soret-driven convection in a nanoparticles suspension heated from above is analyzed theoretically based on linear theory and relative instability concept. A new set of stability equations are derived and solved by using the dominant mode method. The dimensionless critical time τ c to mark the onset of instability is presented here as a function of the Rayleigh number, the Lewis number and the separation ratio. Available experimental data indicate that for large Rayleigh number convective motion is detected starting from a certain time τ≈3 τ c . This means that the growth period of initiated instabilities is needed for convective motion to be detected experimentally. It seems evident that during τ c τ ≤ 3 τ c convective motion is relatively very weak and the primary diffusive transfer is dominant.
Keywords: Soret Convection; Nanoparticles Suspension; Dominant Mode Method

CFD modeling of shell-and-tube heat exchanger header for uniform distribution among tubes by Myoung Il Kim; Yoong Lee; Byung Woo Kim; Dong Hyun Lee; Won Seob Song (359-363).
Several different designs for a header type were numerically studied to achieve uniform distribution of gas phase flow in the header of a shell-and-tube heat exchanger. The different geometries included the position and shape of the inlet nozzle, number of outlet tubes, and length. In numerical calculations, the k-epsilon realizable turbulent model was employed. Standard deviation was used to evaluate the uniformity of the velocity distribution among the whole outlets of the header. As a result, flow patterns in the header could be visualized by using post-processing of numerical results. The uniformity of flow distribution increased with header length, whereas it decreased with gas flow rate. Furthermore, the optimum position and shape of the inlet nozzle could be proposed for a uniform distribution of a 1.3 m-length header, the very same used for the heat exchange of the commercially viable allyl chloride process.
Keywords: CFD; Shell-and-tube Heat Exchanger; Header; Distribution

Optimization of process variables for a biosorption of nickel(II) using response surface method by Shreela Murugesan; Sheeja Rajiv; Murugesan Thanapalan (364-370).
The biosorption of nickel(II) was studied by using crab shell particles of diameter (d p =0.012 mm) under different initial concentrations of nickel(II) in solution (0.01–5.0 g/l), temperature (20–40 °C), pH (2–6.5), and biosorbent dosages (0.5–10 g/l). The maximum removal of nickel(II) occurred at pH 6.5 and temperature 40 °C for a biosorbent dosage of 6 g/l. The results were modeled by response surface methodology (RSM), which determines the maximum biosorption of nickel(II) as a function of the above four independent variables, and the optimum values for the efficient biosorption of nickel(II) were obtained. The RSM studies were carried out using Box-Behnken design and the analysis of variance confirms the adequacy of the quadratic model with coefficient of correlation R2 to be 0.9999. The quadratic model fitted the data well with Prob>F to be <0.0001, indicating the applicability of the present proposed model.
Keywords: Biosorption; Biosorbent; Box-Behnken Design; Crab Shell; Nickel(II); RSM Modeling

To improve the ortho- or para-xylene selectivity via the isomerization of meta-xylene, the acid sites located on the external surface of zeolite Y crystals were neutralized by using the intrinsic mechanochemical method, which resulted in reduced coke formation. Zeolite Y crystals were mixed in an agate mortar with alkaline earth metal oxides supported on micro spherical non-porous silica. The catalytic performances into o- or p-xylene from the m-xylene isomerization reaction were enhanced, especially with either the CaO- or MgO-neutralized catalyst, as verified by adsorption of bipyridine, which could not access the pore channel due to its bulky molecular size. These consistent changes in the reaction performance could be ascribed to the decrease in the number of acid sites on the external surfaces.
Keywords: Mechanochemical Neutralization Method; Alkaline Earth Metal Oxides; m-Xylene Isomerization; Coke Formation; Adsorption of Bi-pyridine

Selective catalytic oxidation of H2S using nonhydrolytic vanadia-titania xerogels by Dal-Rae Cho; Sang-Yun Kim; Dae-Won Park; Pierre Hubert Mutin (377-381).
A series of vanadia-titania (V-Ti) xerogel catalysts were prepared by nonhydrolytic sol-gel method. These catalysts showed much higher surface area and total pore volumes than the conventional V2O5-TiO2 xerogel. Two species of surface vanadium in the xerogel catalysts were identified by Raman measurements: monomeric vanadyl and polymeric vanadates. The selective oxidation of hydrogen sulfide in the presence of excess water and ammonia was studied over these catalysts. Xerogel catalysts from the nonhydrolytic method showed very high conversion of H2S without harmful emission of SO2. The conversion of H2S increased with increasing vanadia loading up to 10V-Ti; however, it decreased at higher vanadia loading (12V-Ti and 18V-Ti) probably due to the formation of crystalline V2O5.
Keywords: Hydrogen Sulfide; Selective Oxidation; Nonhydrolytic; Sol-gel Method; Vanadia-titania Xerogel; Ammoniumthiosulfate

Direct preparation of dichloropropanol from glycerol and hydrochloric acid gas in a solvent-free batch reactor: Effect of experimental conditions by Sun Ho Song; Sang Hee Lee; Dong Ryul Park; Heesoo Kim; Sung Yul Woo; Won Seob Song; Myong Suk Kwon; In Kyu Song (382-386).
Solvent-free direct preparation of dichloropropanol (DCP) from glycerol and hydrochloric acid gas was carried out in a batch reactor with a variation of reaction conditions (agitation speed, reaction time, reaction temperature, and reaction pressure), amount of H3PW12O40 catalyst, and amount of water absorbent (silica gel blue). The reaction was conducted at high agitation speed in order to avoid mass transfer limitation between glycerol and hydrochloric acid gas. In the direct preparation of DCP from glycerol and hydrochloric acid gas, DCP formation was increased with increasing reaction time, reaction temperature, and reaction pressure. Chlorination of glycerol occurred via the following consecutive reaction steps: glycerol→monochloropropanediol (MCPD)→dichloropropanol (DCP)→trichloropropane (TCP). Reaction rate decreased in the order of first-step reaction>second-step reaction>third-step reaction. The presence of H3PW12O40 catalyst and water absorbent (silica gel blue) enhanced the formation of DCP. DCP formation was increased with increasing the amount of H3PW12O40 catalyst and water absorbent (silica gel blue). Strong Brönsted acid site of H3PW12O40 catalyst and water removal from the reaction system favorably served in improving DCP formation.
Keywords: Dichloropropanol; Glycerol; Hydrochloric Acid Gas; Heteropolyacid Catalyst; Water Absorbent

Decomposition of acetic acid by advanced oxidation processes by Ju Young Park; In Hwa Lee (387-391).
Decomposition of acetic acid, known as a non-degradable organic compound, was conducted for several advanced oxidation processes such as TiO2-UV-H2O2, Fe2+-H2O2-UV, UV-H2O2 and TiO2-UV system. Acetic acid was efficiency decomposed within 120 minutes of UV radiation under the initial concentration of 500 ppm. The initial chemical oxygen demands (COD cr ) tended to increase as H2O2 was added in most reactions. However, the initial COD cr was not increased as H2O2 was consumed for the oxidation of iron salt in the photo-Fenton oxidation process. COD cr and concentration of acetic acid rapidly decreased as the mole ratio of hydrogen peroxide increased owing to rapid decomposition of the reactant at the beginning of reaction. All reactions show first order pseudo reaction rate. The COD cr removal rate and the decomposition efficiency of acetic acid were fastest in the UV-H2O2 process.
Keywords: Advanced Oxidation Processes; Photocatalysis Reaction; Photo-Fenton Oxidation; Acetic Acid

Enhanced photocatalytic oxidation properties in Pt-TiO2 thin films by grounding by Wooseok Nam; Jong Hyeok Park; Gui Young Han (392-397).
The rates of formaldehyde and toluene photocatalytic oxidation with different initial concentrations over a Pt-TiO2 film were analyzed at both the grounded and non-grounded states. The photocatalytic oxidation rates at the grounded states were faster than in the non-grounded states under similar reaction conditions. The enhanced photocatalytic oxidation rates in the grounded state were attributed to the effective splitting of the electron-hole pairs as a result of the scavenging of photoexcited electrons through the ITO (indium tin oxide) glass to earth. The pseudo first order model showed good agreement with the experimentally obtained heterogeneous photocatalytic oxidation rates of formaldehyde and toluene.
Keywords: Pt-TiO2 ; Sputtering; Scavenging; Toluene; Formaldehyde

Decomposition of 2-chlorophenol by supercritical water oxidation with zirconium corrosion by Jae-Hyuk Lee; Sang-Ha Son; Tran Tan Viet; Chang-Ha Lee (398-402).
The 2-chlorophenol (2-CP) was oxidized in a continuous anti-corrosive supercritical water system. The variation of decomposition efficiency by the corrosion of zirconium 702 was also studied at the variation of feed concentration and reaction time. According to AES depth profile, the oxygen penetration depth to zirconium was not proportional to the exposure time. It might stem from the formation of zirconium oxide layer on the surface delaying the corrosion. However, the increase in feed concentration accelerated the corrosion of zirconium. The corrosion of zirconium at low feed concentration led to the improvement of decomposition efficiency due to the catalytic effect of formed zirconium oxides, while that at high feed concentration deteriorated the decomposition efficiency owing to large consumption of oxidant in corrosion.
Keywords: Supercritical Water Oxidation; Halogenated Compounds; Corrosion; Zirconium

We manufactured PVA-derived hydrogels wth some crosslinkers by using a foam generation technique. Amino acids gels showed remarkably higher swelling ratios, probably because of the highly crosslinked network along with hydrogen bonds. Boric acid and starch would catalyze dehydration while structuring to result in much lower water content and accordingly high gel content, leading to less elastic, hard gels. Bulky materials such as ascorbic acid or starch produced, in general, large pores, and also nicotinamide, highly hydrophobic, was likely to enlarge its pore size, thus leading to reduced swelling. Hydrophilic (or hydrophobic), functional groups which are involved in the reaction or physical linkage, and bulkiness of crosslinkers were found to be more critical to the crosslinking structure and its density than molecular weights that seemed to be closely related to pore sizes. The average sizes of pores were 20 μm for methionine, 10–15 μm for citric acid, 50–70 μm for L-ascorbic acid, 30–40 μm for nicotinamide, and 70–80 μm for starch. Also, amino acid and glucose gels were more elastic than the others. The elasticity of a gel was reasonably correlated with its water content or swelling ratio. On the other hand, L-ascorbic acid among glucose, methionine, citric acid and vitamins, imparted not only the most favorable physical properties and the greatest cell density but also the highest PAH degradation on its derivative gels. The higher biomass ensured the higher degradation rate. The maximum cell density was 0.267 mg/g-hydrogel and degradation rates and efficiencies ranged 0.013–0.007 mM/mg/day and 92-48%, respectively.
Keywords: PVA; Hydrogel; CGA Technique; Cell Adherence; Additive; Amino Acid; Organic Acid; Lipid; Saccharide; Microbial Immobilization

Ralstonia eutropha was cultivated in a continuous stirred fermenter with various C/N ratios (20, 30, and 40), dilution rates, and organic salt substrates (sodium propionate or sodium valerate) to explore the microbial growth and the poly(3HB-co-3HV) accumulation. When sodium propionate was used as the secondary carbon source, the HB/HV molar ratio at various C/N ratios and dilution rates did not change appreciably (approximately 90: 10). The highest poly(3HB-co-3HV) content in biomass (41.8%) and poly(3HB-co-3HV) productivity (0.100 g/(L·h)) occurred under the condition with a C/N ratio of 20 and dilution rate of 0.06 h−1. When sodium valerate was used as the secondary carbon source, the productivity of poly(3HB-co-3HV) increased with increasing dilution rate for the C/N ratio of 30 and 40. The average HB/HV molar ratio ranged from 48: 52 to 78: 32. The feeding of sodium valerate promoted the accumulation of HV better than feeding sodium propionate did. This study shows that a potential strategy of manipulating by both C/N ratio and dilution rate could be used to control the HV unit fraction in poly(3HB-co-3HV) in a continuous cultivation.
Keywords: Poly(3HB-co-3HV); Continuous Cultivation; Dilution Rate; Ralstonia eutropha ; C/N Ratio; Propionate; Valerate

Nanoassembly of CdTe nanowires and Au nanoparticles: pH dependence and reversibility of photoluminescence by Jaebeom Lee; Hongxia Chen; Kwangnak Koh; Chulhun L. Chang; Cheol-Min Kim; Soo-Hyung Kim (417-421).
Radial organized nanohybrids that are composed of Au nanoparticles (NPs) surrounding CdTe nanowires (NWs) via bioconjugation of streptavidin (SA) and D-biotin (B) were prepared to compare with the non-conjugated NWs. Two respective NW-containing hybrids with/without Au bioconjugation presented the same pH dependence except for photoluminescence (PL) reversibility. It would be explained that the chemical modification of NW surface can be retarded due to the geometric hindrance of acidic fluids in nanoscale regime and the loosely encapsulated Au NPs on NWs assisted to induce the luminescence recovery from collective resonance of excitons and plasmons in nanohybrids.
Keywords: Nanowires; Nanoparticles Bioconjugates; Luminescence Enhancement; Collective Effects; pH Dependence

Optimization of citric acid production by Aspergillus niger NRRL 567 grown in a column bioreactor by Suzelle Barrington; Jun Seok Kim; Li Wang; Jin-Woo Kim (422-427).
Citric acid production using Aspergillus niger NRRL 567 grown on peat moss has been optimized in a column bioreactor using a statistically based method. A 23 full factorial design with eight fermentation conditions was applied to evaluate significance on citric acid production and their interactions between variables, where the three independent variables evaluated were aeration rate, bed depth and temperature. Aeration rate and fermentation temperature were identified to be significant variables. Citric acid production markedly increases with aeration rate and fermentation temperature; however, the bed depth of solid substrate showed an insignificant effect on citric acid production. The optimum fermentation condition for citric acid production in a column bioreactor consisted of aeration rate of 0.84 vvm, bed depth of 22 cm and fermentation temperature of 32 °C. Under a given condition, a maximum citric acid production of 120.6 g/l was predicted and matched well with the experimental value of 123.9 g/kg.
Keywords: Aspergillus niger ; Citric Acid; Solid Substrate Fermentation; Optimization; Peat Moss

Fermentation process development for hyaluronic acid production by Streptococcus zooepidemicus ATCC 39920 by Shu-Jen Chen; Jia-Ling Chen; Wei-Chih Huang; Hsin-Liang Chen (428-432).
The development of a fermentation strategy for hyaluronic acid (HA) production by Streptococcus zooepidemicus ATCC 39920 has been explored. The specific HA productivity (Y P/X ) was affected by the medium carbon-tonitrogen (C/N) ratio rather than the specific growth rate of cells. Accordingly, HA fermentation should be performed in a balanced medium with an optimum C/N ratio of 2: 1 in a batch culture. To improve the performance of the batch culture, the operation conditions for the fill-and-draw culture were investigated. It was found that the timing of medium exchange is critical for successfully performing fill-and-draw operations. Since streptococcal cells at the stationary phase might lose the capacity of HA synthesis, the displacement of the medium in a fill-and-draw culture should be started at the late exponential growth phase.
Keywords: Streptococcus zooepidemicus ; Hyaluronic Acid; Carbon-to-Nitrogen Ratio; Specific Growth Rate; Fed-batch; Fill-and-draw Culture

Many natural phenolic compounds found in plants are well known for their antibiotic and antioxidant activities. It has been hypothesized that these activities of natural phenols could be used for developing permanent anti-biofouling coatings. In this study, two phenolic components, anacardic acid and cardanol, were extracted from cashew nut shell liquid, and tested for their antibiotic and anti-biofouling activities against Pseudomonas fluorescens. Both compounds killed all the cells within 18 hours (anacardic acid) and 30 hours (cardanol) after the addition to the culture media at a concentration of 800 μg/ml. To form a stable permanent coating of these compounds, first they were polymerized by enzymatic polymerization, and the polymers were cross-linked on a glass slide. P. fluorescens were cultured on the coated and uncoated glasses for two weeks, and the images of the cells grown on the surfaces were taken by SEM. The coated surfaces clearly demonstrated anti-biofouling activities, showing not only fewer numbers of cells but also less exopolymer than the uncoated surfaces. Based on these results, a phenolic compound with a similar structure of anacardic acid was synthesized by using propylene diamine and fluorocarboxylic acid with cardanol. The synthesized phenolic compound was polymerized and cross-linked on a glass slide to test the anti-biofouling activity. The SEM images of the cells on the coated surface showed considerable decreases in the number of adhered cells and the amount of exopolymers even more than the anacardic acid and cardanol coatings. It is thought that the natural phenolic compounds with active functional groups can be used for anti-biofouling agents.
Keywords: Biofilm; Natural Phenolic Compounds; Anti-biofouling Coatings; Anacardic Acid; Cardanol

Enhancing the sporulation of Streptomyces kasugaensis by culture optimization by Won-Bok Chae; Young-Bum Kim; Sung-Won Choi; Hyang-Bok Lee; Eun-Ki Kim (438-443).
To be an effective microbial biocide, Streptomyces kasugaensis should be converted into spore during cultivation process for successful long-term storage. By statistical design methods, culture conditions including medium components and operating parameters were optimized and more than 100 times increase in spore yield was achieved. Addition of spent culture fluid (100 ppm), EDTA (30 ppm), mycophenolic acid (32 ppm) with combination of pH up-shock (5.5 to 8.5) increased total viable cell and spore conversion rate, resulting in 1.6×107 (spore/mL) in 5 days of culture in a fermenter. This result provides a practical method for obtaining high spore number for commercial production of Streptomyces kasugaensis as a microbial pesticide.
Keywords: Biocontrol Agent; Sporulation; Statistical Experimental Design; Streptomyces kasugaensis

The effects of culturing conditions on phenylalanine ammonia lyase production by a recombinant E. coli strain were investigated by using a controlled fed-batch fermentation system. In a 5 L fermentor, the optimal composition of the batch medium was 2% glucose, 1% yeast extract, 0.7% K2HPO4, 0.8% KH2PO4, 0.5% (NH4)2SO4, 0.1% MgSO4·7H2O. The optimal feed glucose solution was 50%. Glucose concentration and pH of the culture broth were maintained at about 2.0 g/L and 7.0 during the fed-batch phase, respectively. Following 24-h cultivation, 0.2 mmol/L isopropyl-β-D-thiogalactopyranoside (IPTG) was added and temperature was shifted from 37°C to 42°C to induce pal gene expression. Under optimal conditions, a high productivity of 300 U/g could be achieved after 48 h culture, and a cell density of OD600 about 82 was obtained at 52 h culture at 500 r/m stirrer speed and 1 vvm, respectively.
Keywords: Activity; Culturing Conditions; Fed-batch; Phenylalanine Ammonia Lyase; Recombinant Escherichia coli

Fractional precipitation is a simple, efficient method for pre-purifying paclitaxel from plant cell cultures of Taxus chinensis. The pH, a key process variable in fractional precipitation, was optimized in terms of the yield and purity of paclitaxel with a fixed methanol concentration in water (61.5%, v/v), paclitaxel content in the crude extract (0.5%, w/v), and storage time (14 hr). The maximum yield (∼99%) and purity (∼84.4%) of paclitaxel were obtained at pH 8.0 with potassium phosphate buffer. The precipitate from fractional precipitation was an amorphous state paclitaxel by analysis of XRD and SEM. Also, the particle size distribution of dried precipitate was a range of approximately 119–411 μm. The use of fractional precipitation in the pre-purification process allowed for rapid and efficient separation of paclitaxel from interfering compounds, and dramatically increased the yield and purity of the crude paclitaxel for subsequent purification steps.
Keywords: Paclitaxel; Fractional Precipitation; pH; Optimization; Pre-purification

Molecularly imprinted polymeric microbeads (MIPMs) were prepared by using a magnetic impeller by the modified suspension polymerization method with D-phenylalanine (Phe) as the water-soluble template without derivatization, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker, toluene as the porogen, polyvinyl alcohol as the stabilizer, and sodium dodecyl sulfate as the surfactant. The mean diameter of MIPMs decreased from 12.45 μm to 8.86 μm by using a simple magnetic impeller instead of a conventional simple straight-blade turbine impeller during suspension polymerization. The adsorption selectivity of MIPMs prepared with a magnetic impeller was much improved as compared to the adsorption selectivity of MIPMs prepared with a conventional simple straight-blade turbine impeller. The adsorption selectivity of MIPMs changed from reversed adsorption (less than 1) to positive (higher than 1) as the washing time increased after suspension polymerization.
Keywords: Molecularly Imprinted Polymeric Microbead; Phenylalanine; Modified Suspension Polymerization; Enantioselective Separation; Molecular Recognition; Impeller

Lead, copper, and cadmium were adsorbed onto aged calcium alginate beads containing cell-suspension from the waste of beer fermentation broth. Beads prepared by adding 0.6% (w/v) sodium alginate into the cell suspension from the waste of beer fermentation broth and making the cell suspension drop into the 1% (w/v) calcium alginate solution were stored in the 1% (w/v) calcium chloride solution for 1 year. The specific metal uptake of the aged cell-suspension immobilized bead was 312 mg Pb2+, 158 mg Cu2+, and 112 mg Cd2+/g bead dry weight at pH 7.5 of the metal solution, respectively. The relation between the specific metal uptake by the aged cell-suspension immobilized beads and the equilibrium metal concentration was nonlinearly regressed and well described by the Freundlich isotherm. The specific cadmium uptake capacity of aged cell-suspension immobilized beads was between the specific cadmium uptake capacities of commercial beads Duolite GT-73 and Amberite IRA-400 and higher than those of the fresh Saccharomyces cerevisiae ATCC 834 and Saccharomyces cerevisiae ATCC 24858 immobilized beads.
Keywords: Biosorption of Heavy Metals; S. cerevisiae ; Cell Immobilized Bead; Cell Suspension; Waste of Beer Fermentation Broth

Soybean hull functionalized by phosphoric acid for sorption of copper from aqueous solution by Renmin Gong; Lingling Liu; Min Feng; Jiajing Zhao; Xingyan Liu; Shoujun Ni (462-467).
One kind of potentially biodegradable cationic sorbent, which bears hydroxyl groups of phosphoric acid as its functional groups, with high sorption capacity of copper was prepared by thermochemically esterifying phosphoric acid (PA) onto soybean hull. Sorption of Cu(II) from aqueous solution onto modified soybean hull (MSH) was investigated in a batch system. The sorption experiments were performed under various conditions such as different initial pH, copper concentration, MSH dosage, and contact time. The maximum copper sorption was obtained when initial solution pH≥3.5. The isothermal data of copper sorption fitted the Langmuir model and the sorption process could be described by the pseudo-first-order kinetic model. The maximum sorption capacity (Q m ) of MSH for Cu(II) was 31.55 mg/g. For 100 mg/l of Cu(II) solution, a sorption ratio above 91% could be achieved by 5.0 g/l of MSH. The equilibrium of Cu(II) sorption was reached within 50 min. The foreign cation and chelator in Cu(II) solution caused decline of Cu(II) sorption.
Keywords: Sorption; Copper; Esterification; Phosphoric Acid; Soybean Hull

The objective of this work is to present the optimization of SMB operating conditions under the fixed performance of high purity (over 99%), which takes mass transfer effect into account. The parameters for the numerical calculation were used by our previous work [1,2] of binary separation of aqueous mixture of glucose and fructose. The equilibrium isotherm was linear and the mass transfer was described by LDF approximation. The single parameter of Stanton number was used for the mass transfer effect. The result of our work was compared with that of the triangle theory [3]. For the sake of this procedure, an analytical solution for a TMB mode was suggested and compared with the simulated result of SMB mode. The advantage of the TMB model with the mass transfer effect was the rapid determination of the flow conditions of each zone for the required purity of extract and raffinate.
Keywords: SMB (Simulated Moving Bed); TMB (True Moving Bed); Triangle Theory; Mass Transfer Effects; Stanton Number; Numerical Simulation

Numerical and experimental investigation on a new modified valve in a valve tray column by Asghar Alizadehdakhel; Masoud Rahimi; Ammar Abdulaziz Alsairafi (475-484).
This paper reports experimental and computational fluid dynamics (CFD) modeling studies on the performance of three modified valves operating in a valve tray column. The original and modified valves including vnotched, warped and double-valve are tested experimentally. The experimental rig was a Perspex column having a single valve equipped with a fluctuating plate to measure the quality of gas distribution by using laser sensors. Two-stage nested designs were employed to show the repeatability and consistency of the measurements. In the CFD modeling, the volume of fluid (VOF) method was used to model the gas-liquid two-phase flow inside the column. A good agreement was observed between experimental data and the CFD predictions. The results showed that the double-valve layout provides a better gas distribution, smaller bubbles with greater interface area and lower pressure drop in comparison with the original and the two other modified valves.
Keywords: Valve Tray; CFD; Hydrodynamics; Multiphase Flow; Bubble

Synthesis and structural properties of lithium titanium oxide powder as-synthesized by two step calcination process by Soo Ho Kim; Hoon Park; Seung Hyun Jee; Ho Sang Ahn; Dong-Joo Kim; Ji Won Choi; Seok Jin Yoon; Young Soo Yoon (485-488).
A two-step calcination synthesis, considering the potential for mass production, of lithium titanium oxide powder was carried out to fabricate a single Li4Ti5O12 phase, which is useful for anode electrode material of Li-based rechargeable battery as well as an electrode for supercapacitor. The final composition is controlled by adding more TiO2 powder into powder gained at one calcination process during the two calcination process. We investigated the influence of excess TiO2 on the structural characteristics of lithium titanium oxide synthesized by the two-step calcination method. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) measurements showed that the as-synthesized powder had a spinel crystal structure as well as A composition of 4: 5: 12. In addition, a high resolution transmission electron microscopy (HRTEM) analysis revealed that the fabricated powder exhibited a single crystalline phase formation. These results indicated that the powder synthesized in the one-step calcination process showed coexistence crystalline phases, which are the Li4Ti5O12 and Li2.39Ti3.4O8 phase. However, in the two-step calcination process, the powder synthesized showed the single crystalline Li4Ti5O12 phase. A very uniform grain size of the as-synthesized powder was shown in a field emission scanning electron microscopy (FESEM). These results suggested that the two-step calcination process can be used for synthesis of single crystalline Li4Ti5O12 powder with uniform grain shape and provide motivation to pursue mass production of lithium titanium based oxide powder for bulk type batteries.
Keywords: Lithium Titanium Oxide; Two Step Calcination Process; Oxygen Content; Rechargeable Battery; High Resolution Transmission Electron Microscopy

The applicability of the Multi-wavelength Near-infrared sensor to analyze coal properties such as proximate analysis (moisture, ash, volatile matter, fixed carbon), ultimate analysis (carbon, hydrogen, nitrogen, oxygen, sulfur) and heating value is discussed. The most useful wavelengths (1,680, 1,942, 2,100, 2,180, 2,300 nm) for determining coal properties concentration were chosen by analyzing the NIR spectrum according to coal properties. Absorbances at the characteristic wavelength obtained from 128 mixed coal samples, which are using at a conventional thermal power plant, were correlated to the coal properties by using multiple regression analysis. The accuracy of coal analysis was examined by calculating the RMSEC (%), RMSEP (%), comparing the error with ASTM/ISO tolerance and performing paired Student’s T-test. The result of on-line coal analysis for all moisture, volatile matter, fixed carbon, carbon, hydrogen and heating value is not different from that of ASTM/ISO traditional methods at 90% confidence level. The technology appears suitable for the determination of several coal prorperties. If calibrated periodically, this on-line analysis of coal properties is helpful to efficiently operate a coal fired power plant.
Keywords: NIR; Absorbance; Coal Properties; Real-time Analysis

Effect of laser beam focusing point on AFM measurements by Younghun Kim; Young In Yang; Inhee Choi; Jongheop Yi (496-499).
The optical beam deflection method, which is used in AFM to obtain surface images, may distort the resulting image. The flexible and long cantilever is easily overdamped by the laser radiation pressure, resulting in steady deflection of the cantilever (<1 nm). This deflective force distorts the image and influences the force-distance (F-D) curve. The present study investigated the effect of laser radiation pressure on image distortion. As a proof-of-concept test, two grating samples (with step heights of 150 and 18 nm for TGX01 and TGZ01, respectively) were examined with an NSC36 series cantilever in air and water media.
Keywords: Atomic Force Microscopy; Image Distortion; Laser Beam; Radiation Pressure

The thermal behavior of Illitic-kaolinitic clay for manufacturing of low porosity ceramic Raschig rings was characterized during the sintering process. The samples were shaped by extrusion method and fired at different temperatures from 1,100 to 1,300 °C. The main physical-chemical transformations were studied by evaluating changes in shrinkage, water absorption, porosity, mechanical strength, microstructure and mineralogical compositions. The optimum sintering condition was found to obtain maximum mechanical strength. Chemical resistance of ceramic Raschig rings also was determined according standard method. It was shown that the better chemical resistance could be attributed to the different mineralogical compositions, in particular with presence of mullite phase.
Keywords: Kaolin; Compressive Strength; Raschig Ring; Sintering; Porosity

To determine the effect of volatile matter on combustion reactivity, the pyrolysis and combustion behavior of a set of four (R, C, M and K coals) coals and their chars has been investigated in a TGA (SDT Q600). The maximum reaction temperatures and maximum reaction rates of the coals and their chars with different heating rates (5–20 °C/min) were analyzed and compared as well as their weight loss rates. The volatile matter had influence on decreasing the maximum reactivity temperature of low and medium rank coals (R, C and M coals), which have relatively high volatiles (9.5–43.0%), but for high rank coal (K coal) the maximum reactivity temperature was affected by reaction surface area rather than by its volatiles (3.9%). When the maximum reaction rates of a set of four coals were compared with those of their chars, the slopes of the maximum reaction rates for the medium rank coals (C and M coals) changed largely rather than those for the high and low rank coals (R and K coals) with increasing heating rates. This means that the fluidity of C and M coals was larger than that of their chars during combustion reaction. Consequently, for C and M coals, the activation energies are lower (24.5–28.1 kcal/mol) than their chars (29.3–35.9 kcal/mol), while the activation energies of R and K coals are higher (25.0-29.4 kcal/mol) than those of their chars (24.1–28.9 kcal/mol).
Keywords: Combustion of Coal and Char; Reactivity; Volatiles; TGA; Activation Energy

Geldart group A particles were fluidized in a 10 cm i.d.×1.8 m high Plexiglas-made bed with ambient air to determine the hydrodynamic properties in a gas-solid fluidized bed. The effects of static bed heights, position of pressure measuring points, differential and absolute pressure fluctuations on the hydrodynamic behavior of a Geldart group A particles in a gas-solid fluidized bed were investigated. The particles used in this study were 80 micrometer FCC powders and 60 micrometer glass beads. The variance of pressure fluctuations was used to find the minimum bubbling velocity. The obtained minimum bubbling velocity was compared with the other methods available in the literature. This method was found to be much easier and had better data reproducibility than the classical visual method or sedimentation method. The variance of pressure fluctuations increased due to the increase of superficial gas velocity and static bed height. The obtained minimum bubbling velocity and pressure fluctuations were found to depend on the measuring position along the axial direction. The effect of measuring position was discussed. Cross-correlation of two pressure signals was used to find the delay time, then the bubble rising velocity.
Keywords: Group A Particles; Minimum Bubbling Velocity; Bubble Rising Velocity; Pressure Fluctuations

Synthesis and characterization of poly(ether sulfone) grafted poly(styrene sulfonic acid) for proton conducting membranes by Yoon Taik Goh; Rajkumar Patel; Se Jun Im; Jong Hak Kim; Byoung Ryul Min (518-522).
Two-step synthesis of proton-conducting poly(ether sulfone) (PES) graft copolymer electrolyte membrane is proposed. Fridel Craft alkylation reaction was used to introduce chloromethyl pendant group onto the PES polymer backbone. Later on, atom transfer radical polymerization (ATRP) was applied to synthesize a series of poly(ether sulfone) grafted poly(styrene sulfonic acid) (PES-g-PSSA). Successful chloromethyl substitution and grafting of the pendant group was characterized by the 1H-NMR and elemental analysis. Electrochemical properties such as ion exchange capacity (IEC), water uptake and proton conductivity increased with increasing PSSA contents. Thermal gravimetric analysis (TGA) showed the thermal stability of membranes up to 270 °C. Proton conductivity for maximum amount of grafting was 0.00297 S/cm.
Keywords: Polymer Electrolyte Membrane; Proton Conductivity; Atom Transfer Radical Polymerization; Fuel Cell

Syngas combustion characteristics of oxygen carrier particles have been investigated. Experiments were performed on four oxygen carrier particles in a fluidized bed reactor. All four oxygen carrier particles showed high gas conversion, high CO2 selectivity, and low CO concentration in the reducer and very low NOx (NO, NO2, N2O) emissions in the oxidizer. Moreover, all particles showed good regeneration ability during successive reduction-oxidation cyclic tests up to the 10 th cycle. The results indicate that inherent CO2 separation, NOx-free combustion, and long-term operation without reactivity decay of oxygen carrier particles are possible in a syngas fueled chemical-looping combustion system with NiO/bentonite, NiO/NiAl2O4, Co x O y /CoAl2O4, and OCN-650 particles. However, Co x O y /CoAl2O4 represented slight decay of oxidation reactivity with the number of cycles increased and the oxidation rate slower than other particles.
Keywords: Chemical-looping; Oxygen Carrier; Carbon Dioxide; Nitrogen Oxides; Syngas

Gasification of rice husk in a cyclone gasifier by Shaozeng Sun; Yijun Zhao; Fengming Su; Feng Ling (528-533).
The experimental results of air gasification of rice husk in the cyclone gasifier were presented at the fuel rate of 20.1 kg/h. With the equivalence ratios varied in the range of 0.21–0.32, the heating value of the producer gas decreases from 6.98 MJ/Nm3 to 3.11 MJ/Nm3 and the cold gas efficiency decreases from 64% to 31%. However, the tar content in the prouder gas decreases with the increase of the equivalence ratio. The rice husk and ash were examined under a scanning electron microscope (SEM) and energy dispersive X-ray (EDX) elemental analysis. The outer surface of the fuel particle which is of scale structure does not change basically during the gasification. The pyrolyzed gas is mainly released from the inner surface of the fuel particle.
Keywords: Biomass; Gasification; Equivalence Ratio; Cyclone; SEM

A hierarchical gain scheduling (HGS) approach is proposed to model the nonlinear dynamics of NO x emissions of a utility boiler. At the lower level of HGS, a nonlinear static model is used to schedule the static parameters of local linear dynamic models (LDMs), such as static gains and static operating conditions. According to upper level scheduling variables, a multi-model method is used to calculate the predictive output based on lower-level LDMs. Both static and dynamic experiments are carried out at a 360 MW pulverized coal-fired boiler. Based on these data, a nonlinear static model using artificial neural network (ANN) and a series of linear dynamic models are obtained. Then, the performance of the HGS model is compared to the common multi-model in predicting NO x emissions, and experimental results indicate that the proposed HGS model is much better than the multi-model in predicting NO x emissions in the dynamic process.
Keywords: Utility Boiler; Gain Scheduling; NO x Emissions; Nonlinear Dynamic Model

Multi-method mercury specification from lignite-fired power plants by Ping Lu; Jiang Wu; Wei-ping Pan (542-547).
Mercury concentration and speciation partitioning, including total mercury, elemental mercury and oxidized mercury from a lignite-fired power plant under different operating conditions, was studied by Ontario hydro method (OHM), two kinds of continuous mercury monitors (semi-continuous emission monitor (SCEM) and continuous mercury monitor (CMM)), and the sorbent trap method. The effects of boiler load, fuel blending ratio, electrostatic precipitator, flue gas desulphurization, flue gas bypassing the FGD ratio, and mercury measuring methods on mercury emission were analyzed. The results indicated that mercury data from OHM, SCEM and CMM presented a good consistency throughout the entire testing period within ±20% acceptable range; however, the results from Appendix K provided bigger discrepancies than the results of OHM and SCEM due to the interferences of higher selenium content in the flue gas. The particulate-bound mercury removal efficiencies of ESP were determined to be 16–35%. The percentages of elemental mercury emitted from two lignite-fired power plants were in the higher ranges of 43.9–74.2%.
Keywords: Mercury Emission; Lignite-fired PC Boiler; Hg Measuring Method; Field Testing

Pyrolysis of wood species based on the compositional analysis by Qian Liu; Shurong Wang; Kaige Wang; Zhongyang Luo; Kefa Cen (548-553).
Based on the Van Soest method, the components in Chinese fir and fast-growing poplar were quantified, and the fiber present was separated into three fractions: neutral detergent fiber, acid detergent fiber and strong acid detergent fiber. Microstructure of the fibers was investigated by a Fourier transform infrared spectrometry. Cellulose and hemicellulose both represent the characteristics of polysaccharides, while lignin has dissimilar structure. Pyrolysis of fir, poplar and the detergent fibers was carried out on a thermogravimetric analyzer coupled with FTIR spectrometry. After the removal of extractives and soluble minerals, pyrolysis of NDF shows the characteristics of the three main components. Hydrocarbons, aldehydes, ketones, acids, alcohols and others are generated due to the primary pyrolysis of hemicellulose and cellulose in single stages. Phenols and alcohols are the dominant volatiles released from pyrolysis of lignin in two successive stages, respectively.
Keywords: Wood; Pyrolysis; TG; FTIR; Component

Kinetic analysis of NO-Char reaction by Shaozeng Sun; Juwei Zhang; Xidong Hu; Penghua Qiu; Juan Qian; Yukun Qin (554-559).
Two Chinese coals were used to prepare chars in a flat flame flow reactor which can simulate the temperature and gas composition of a real pulverized coal combustion environment. Acid treatment on the YB and SH chars was applied to obtain demineralized chars. Kinetic characterization of NO-char reaction was performed by isothermal thermogravimetry in the temperature range of 973–1,573 K. Presence of catalytic metal matter can increase the reactivity of chars with NO, which indicates that the catalytic effects of inherent mineral matter play a significant role in the NO-char reaction. The discrete random pore model was applied to describe the NO-char reactions and obtain the intrinsic kinetics. The model can predict the data for all the chars at various temperatures well, but underestimate the reaction rates at high carbon conversions for the raw YB and SH chars, which can be attributed to the accumulation of metal catalyst on char surface.
Keywords: Char; NO; Reducing Condition; Kinetics; Pore Model

Behavior of mercury release during thermal decomposition of coals by Shaoqing Guo; Jianli Yang; Zhenyu Liu; Yong Xiao (560-563).
The mercury release behavior during thermal decomposition of three Chinese coals with different types was studied under nitrogen, carbon dioxide and air at temperatures of 800, 900, 1,000 and 1,100 °C. The thermal treatment experiments were carried out in a quartz tube reactor. Results showed that the release ratio of total mercury during thermal decomposition of coals increases with the increasing temperature. The order of the amount of mercury released under the three atmospheres is nitrogencarbon dioxide>air for all three coals. The release behavior of the total mercury under air is independent of the coal type. Under the other two atmospheres the release behavior is distinguished by the coal type.
Keywords: Mercury Release; Coal; Thermal Decomposition

The objective of this paper is to investigate COD removal efficiency of the coking-plant wastewater by applying the moving-bed biofilm sequencing batch reactor (MBBSBR). The operation is simple and 30% WD-F10-4 BioM™ were packed as carrier materials. It was found that the coking-plant wastewater could be effectively treated with 92.9% of COD removal efficiency at a low organic loading rate (OLR) of 0.449 kgCOD·m−3·d−1 The removal efficiency decreased gradually down to 70.9% when OLR increased to 2.628 kgCOD·m−3·d−1. The system has strong tolerance to organic shock loading in this experiment. The COD removal results in the blank experiments of biofilm and sludge showed that the attached biofilm has higher activity than suspended sludge and contributes about 60% to the COD removal.
Keywords: COD Removal; Coking-plant Wastewater; Moving-bed Biofilm; Shock Loading; Microorganism Activity

The local resistance characteristics of high concentration coal-water slurry (CWS) flowing through three types of local fittings, namely the gradual contractions, sudden contractions and 90° horizontal elbows, were investigated at a transportation test facility. Results show that the local resistance loss of gradual contractions decreases as the contraction angle increases. When pipe diameter ratio varies little, local resistance loss of sudden contractions changes insignificantly. There is an optimal value of bend diameter ratio, at which the local resistance loss of horizontal elbows is the least. As Reynolds number increases, the resistance coefficients of all the three fittings first reduce and then stabilize, while the three pipes have different ratio of equivalent length to pipe diameter L e /D behaviors, that is, L e /D of the gradual contractions decreases gradually and then keeps stable; that of the sudden contractions diminishes at first and then increases, and that of the horizontal elbows increases linearly.
Keywords: Coal-water Blurry; Resistance Characteristics; Gradual Contraction; Sudden Contraction; Elbow

Effects of carbon on the sulfidation and hydrodesulfurization of CoMo hydrating catalysts by Hui Ge; Xuekuan Li; Zhangfeng Qin; Feixue Liang; Jianguo Wang (576-581).
The effects of carbon addition on CoMo catalyst performance for sulfidation and hydrodesulfurization (HDS) were investigated. The carbon-containing catalyst was prepared by impregnation of γ-Al2O3 support with NH3 aqueous solution containing Co(NO3)2·6H2O, (NH4)6Mo7O24·4H2O and ethylenediamine. The results indicated that the incorporation of proper carbon on CoMo catalyst can improve its HDS performance. The carbon species on the catalyst were characterized by temperature-programmed oxidation and reduction, temperature-programmed desorption of ammonia and ultraviolet-visible diffuse reflectance spectra. Two forms of carbon species were differentiated: one is spread over the catalyst surface, similar to coke formed from reaction; the other interacts with active phase as an intermediate support. The carbon species acting as intermediate support may decrease the interaction of active metals with support, which enhances the sulfidation and HDS activities of CoMo catalyst.
Keywords: Hydrodesulfurization; Sulfidation; Carbon Addition; Hydrotreating Catalyst; Ethylenediamine

Desulfurization using ZnO nanostructure prepared by matrix assisted method by Tae Jin Lee; In Hak Cho; No-Kuk Park (582-586).
A ZnO nanostructure having a high surface area was developed for use as a desulfurization sorbent. The ZnO nanostructure was prepared by using zinc acetate and activated carbon by the matrix-assisted method. Activated carbon was the matrix in the matrix-assisted method and zinc acetate was the precursor. The desulfurization tests of the ZnO nanostructure were carried out in a packed bed desulfurization system in the temperature range of 300–500 °C. The ZnO nanostructures before and after the sulfidation process were characterized by BET, XRD and SEM. The formulated ZnO nanostructure consisted of ZnO nanoparticles with a size of 10–20 nm and its surface area was very high. Therefore, the sulfur capture efficiency of the ZnO nanostructure was 3 times higher than that of commercial ZnO. However, a reduction of some of the ZnO occurred because of the reducibility of the coal-derived gas, and the surface area of the ZnO nanostructure was slightly reduced due to the sintering of ZnO. It was also confirmed that the silica and alumina containing activated carbon used as the matrix prevent the thermal sintering of ZnO in the sulfidation process at high temperature.
Keywords: ZnO Nanostructure; Ultra Cleanup Coal Gas; Matrix-assisted Method; Activated Carbon

Multiple effects of operating variables on the bubble properties in three-phase slurry bubble columns by Ik Sang Shin; Sung Mo Son; Uk Yeong Kim; Yong Kang; Sang Done Kim; Heon Jung (587-591).
Flow properties of gas phase reactants such as size, rising velocity and frequency were investigated in simulated three-phase slurry bubble column reactors. Effects of gas velocity, reactor pressure, liquid viscosity, solid content in the slurry phase and column diameter on the flow properties of a gas reactant were determined. The multiple effects of operating variables on the bubble properties were well visualized by means of contour maps. The effects of operating variables on the flow properties of bubbles changed with changing column diameter of the reactor. The size, rising velocity and frequency of reactant gas bubbles were well correlated in terms of operating variables including column diameter of the reactor.
Keywords: Bubble Properties; Slurry Bubble Column Reactor; Pressure; Viscous; Column Diameter

Reactivity of a CaSO4-oxygen carrier in chemical-looping combustion of methane in a fixed bed reactor by Qilei Song; Rui Xiao; Zhongyi Deng; Laihong Shen; Mingyao Zhang (592-602).
Chemical-looping combustion (CLC) is a promising technology for the combustion of gas or solid fuel with efficient use of energy and inherent separation of CO2. A reactivity study of CaSO4 oxygen carrier in CLC of methane was conducted in a laboratory scale fixed bed reactor. The oxygen carrier particles were exposed in six cycles of alternating reduction methane and oxidation air. A majority of CH4 reacted with CaSO4 to form CO2 and H2O. The oxidation was incomplete, possibly due to the CaSO4 product layer. The reactivity of CaSO4 oxygen carrier increased for the initial cycles but slightly decreased after four cycles. The product gas yields of CO2, CH4, and CO with cycles were analyzed. Carbon deposition during the reduction period was confirmed with the combustible gas (CO+H2) in the product gas and slight CO2 formed during the early stage of oxidation. The mechanism of carbon deposition and effect was also discussed. SO2 release behavior during reduction and oxidation was investigated, and the possible formation mechanism and mitigation method was discussed. The oxygen carrier conversion after the reduction decreased gradually in the cyclic test while it could not restore its oxygen capacity after the oxidation. The mass-based reaction rates during the reduction and oxidation also demonstrated the variation of reactivity of CaSO4 oxygen carrier. XRD analysis illustrated the phase change of CaSO4 oxygen carrier. CaS was the main reduction product, while a slight amount of CaO also formed in the cyclic test. ESEM analysis demonstrated the surface change of particles during the cyclic test. The reacted particles tested in the fixed bed reactor were not uniform in porosity. EDS analysis demonstrated the transfer of oxygen from CaSO4 to fuel gas while leaving CaS as the dominant reduced product. The results show that CaSO4 oxygen carrier may be an interesting candidate for oxygen carrier in CLC.
Keywords: Chemical-looping Combustion; CaSO4 Oxygen Carrier; Reactivity Study; Methane; Fixed Bed