Korean Journal of Chemical Engineering (v.28, #9)
Zinc oxide nanostructures and their applications by Yoon-Bong Hahn (1797-1813).
Zinc oxide (ZnO) has been known as the next most important material for the fabrication of efficient nanodevices and nanosystems because of its versatile properties such as semiconducting, piezoelectric, and pyroelectric multiple properties. In this review, the state-of-the-art technologies related to the synthesis and characterization, the selective growth of ZnO nanostructures, and their applications for nanodevices are discussed. A special concern is focused on the controlled selective growth of ZnO nanostructures on wanted areas of substrates, which is crucial factor for devices applications. The device applications of ZnO nanostructures include field effect transistors (FETs), field-emission devices, piezoelectric nanogenerators, biosensors, p-n heterjunction diodes such as light-emitting diodes and photovoltaic cells, and so on.
Keywords: Zinc Oxide; Nanostructures; Growth Methods; Device Applications
Wavelet texture analysis in process industries by J. Jay Liu; Chonghun Han (1814-1823).
Wavelet texture analysis has been applied to solve many problems in process industries as well as in other industries. In solving problems from process industries however, its potentials have never been explored to the full extent yet. This is not only because techniques used in wavelet texture analysis are still unfamiliar to researchers and practitioners in process industries, but also because characteristics of the scenes displayed by the images in process industries are difficult to analyze: products and processes in process industries mostly have stochastic outside appearance. The purpose of this article is to give an overview of state-of-the-art methods in wavelet texture analysis through an illustrative example from process industries.
Keywords: Image Texture Analysis; Process Industries; Stochastic Appearance; Wavelet Texture Analysis
Free convective heat and mass transfer in a doubly stratified non-Darcy micropolar fluid by Darbashayanam Srinivasacharya; Chetteti RamReddy (1824-1832).
The flow, heat and mass transfer characteristics of the free convection on a vertical plate with uniform and constant heat and mass fluxes in a doubly stratified micropolar fluid saturated non-Darcy porous medium are studied. The nonlinear governing equations and their associated boundary conditions are initially cast into dimensionless forms by pseudo-similarity variables. The resulting system of equations is then solved numerically using the Keller-box method. The numerical results are compared and found to be in good agreement with previously published results as special cases of the present investigation. The effects of the micropolar, Darcy, non-Darcy and stratification parameters on the dimensionless velocity, microrotation, wall temperature, wall concentration, local skin-friction coefficient and wall couple stress coefficient are presented graphically.
Keywords: Free Convection; Non-Darcy Porous Medium; Micropolar Fluid; Double Stratification
Hydrogen production by decomposition of ethane-containing methane over carbon black catalysts by Mi So Kim; Sang Yup Lee; Jung Hun Kwak; Gui Young Han; Ki June Yoon (1833-1838).
Mixtures of methane and small amounts of ethane were decomposed in the presence of carbon black (CB) catalysts at 1,073–1,223 K for hydrogen production. Although most of the added ethane was first decomposed to ethylene and hydrogen predominantly by non-catalytic reaction, subsequent decomposition of ethylene was effectively facilitated by the CB catalysts. Because some methane was produced from ethane, the net methane conversion decreased as the added ethane increased. The rate of hydrogen production from methane was decreased by the added ethane. A reason for this is that adsorption of methane on the active sites is inhibited by more easily adsorbing ethylene. In spite of this, the hydrogen yield increased with an increase of the added ethane because the contribution of ethane and ethylene decomposition to the hydrogen production was dominant over methane decomposition. A higher hydrogen yield was obtained in the presence of a higher-surface-area CB catalyst.
Keywords: Carbon Black Catalyst; Decomposition; Ethane; Hydrogen Production; Methane
Porcine amniotic fluid as possible antiwrinkle cosmetic agent by Tagon Kim; Sung Kim; WhanYul Kang; Hyun Baek; Hye Young Jeon; Bo Young Kim; Chun Gyu Kim; Donguk Kim (1839-1843).
Porcine amniotic fluid was investigated for use as a functional cosmetic ingredient. From safety tests by MTT (5-diphenyltetrazolium bromide) assay, cell viability was above 90% for 50–1,000 μg/mL concentration and porcine amniotic fluid was safe for cosmetic ingredient. From stability tests, cream containing 1% porcine amniotic fluid maintained constant physical properties for color, pH and viscosity during 28 days, and porcine amniotic fluid was stable for a cosmetic agent. Efficacy tests were done for antiwrinkle (elastase inhibition and collagenase synthesis inhibition), whitening (tyrosinase inhibition and DOPA (3,4-Dihydroxy-L-phenyl-alanine) oxidation inhibition) and antioxidation. At 500 μg/mL concentration, elastase inhibition of porcine placenta amniotic fluid was 33%, whereas that of adenosine as reference was 14%. However, porcine amniotic fluid showed relatively insignificant effect on collagenase synthesis inhibition, whitening and antioxidation activity. From this study, porcine amniotic fluid showed potential for a future antiwrinkle cosmetic agent.
Keywords: Porcine Amniotic Fluid; Antiwrinkle; Whitening; Safety; Stability
Optimization of physical parameters of solid oxide fuel cell electrode using electrochemical model by Dong Hyun Jo; Jeong Hwan Chun; Ki Tae Park; Ji Won Hwang; Jeong Yong Lee; Hyun Wook Jung; Sung Hyun Kim (1844-1850).
To enhance the performance of anode-supported solid oxide fuel cell (SOFC), an electrochemical model has been developed in this study. The Butler-Volmer equation, Ohm’s law and dusty-gas model are incorporated to predict the activation, ohmic and concentration overpotentials, respectively. The optimal cell microstructure and operating parameters for the best current-voltage (J-V) characteristics have been sought from the information of the exchange current density and gas diffusion coefficients. As the cell temperature rises, the activation and ohmic overpotentials decrease, whereas the concentration overpotential increases due to the considerable reduction of gas density at the elevated temperature despite the increased diffusion coefficient. Also, increasing the hydrogen molar fraction and operating pressure can further augment the maximum cell output. Since there exists an optimum electrode pore size and porosity for maximum cell power density, the graded electrode has newly been designed to effectively reduce both the activation and concentration overpotentials. The results exhibit 70% improved cell performance than the case with a non-graded electrode. This electrochemical model will be useful to simply understand overpotential features and devise the strategy for optimal cell design in SOFC systems.
Keywords: SOFC; Simulation; Ohmic; Activation; Concentration; Overpotential; Graded Electrode; Performance of Fuel Cell
Effects of operating factors in the coal gasification reaction by Hai-Kyung Seo; Seik Park; Joogwon Lee; Miyung Kim; Seok-Woo Chung; Jae-Hwa Chung; Kitae Kim (1851-1858).
The effects of operating factors on a gasification system were reviewed by comparing a computational simulation and real operation results. Notable operation conditions include a conveying gas/coal ratio of 0.44, an oxygen/coal ratio of 0.715, a reaction temperature of 1,000 °C, and reaction pressure of 5bar in the case of Adaro coal; based on this, the cold gas efficiency was estimated as 82.19%. At the point of the reaction temperature effect, because the cold gas efficiencies are more than 80% when the reaction temperatures are higher than 900 °C, the gasifier inner temperature must remain over 900 °C. At high reaction temperature such as 1,400 °C, the reaction pressure shows little effect on the cold gas efficiency. The addition of steam into the gasifier causes an endothermic reaction, and then lowers the gasifier outlet temperature. This is regarded as a positive effect that can reduce the capacity of the syngas cooler located immediately after the gasifier. The most significant factor influencing the cold gas efficiency and the gasifier outlet temperature is the O2/coal ratio. As the O2/coal ratio is lower, the cold gas efficiency is improved, as long as the gasifier inner temperature remains over 1,000 °C. With respect to the calorific value (based on the lower heating value, LHV) of produced gas per unit volume, as the N2/coal ratio is increased, the calorific value per syngas unit volume is lowered. Decreasing the amount of nitrogen for transporting coal is thus a useful route to obtain higher calorific syngas. This phenomenon was also confirmed by the operation results.
Keywords: IGCC; Gasifier; O2/Coal Ratio; N2/Coal Ratio; Steam/Coal Ratio; Cold Gas Efficiency; Calories of Syngas Per Unit Volume
Renewable hydrogen production by steam reforming of glycerol over Ni/CeO2 catalyst prepared by precipitation deposition method by Kamal K. Pant; Ruchin Jain; Sapna Jain (1859-1866).
Catalytic steam reforming of glycerol for renewable hydrogen generation has been investigated over Ni/CeO2 catalyst prepared by precipitation-deposition method. The fresh and used catalysts were characterized by surface area and pore size analysis, X-ray diffraction patterns and scanning electron micrographs. Reforming experiments were carried out in a fixed bed tubular reactor at different temperatures (400–700 °C), glycerol concentrations (5–15 wt%) and contact times. (W/F Ao =2−80 g-cat·h/mol of glycerol). The investigation revealed that the Ni/CeO2 catalyst prepared by the above method is effective to produce high yield of hydrogen up to 5.6 (moles of H2/moles of glycerol fed). The formation of methane and carbon monoxide was greatly reduced over this catalyst. Significantly low amount of coke deposition was observed on the CeO2 supported catalyst. From the kinetic analysis, the activation energy for the steam reforming of glycerol was found to be 36.5 kJ/mol.
Keywords: Steam Reforming; Glycerol; Catalyst; Ni/CeO2 ; Renewable Hydrogen
The pyrolysis of waste mandarin residue using thermogravimetric analysis and a batch reactor by Jeong Wook Kim; See-Hoon Lee; Seong-Soo Kim; Sung Hoon Park; Jong-Ki Jeon; Young-Kwon Park (1867-1872).
A study on the pyrolysis of waste mandarin residue, with the aim of producing bio-oil, is reported. To elucidate the thermodynamics and temperature-dependency of the pyrolysis reaction of waste mandarin residue, the activation energy was obtained by thermogravimetric analysis. Mass loss occurred within the temperature range 200–750 °C, and the average activation energy was calculated to be 205.5 kJ/mol. Pyrolysis experiments were performed using a batch reactor, under different conditions, by varying the carrier gas flow rate and temperature. When the carrier gas flow rate was increased from 15 to 30 and finally to 50ml/min, the oil yield slightly increased. Experiments performed within the temperature range 400–800 °C showed the highest oil yield (38.16 wt%) at 500 °C. The moisture content in the bio-oil increased from 35 to 45% as the temperature increased from 400 to 800 °C, which also resulted in reduction of the oxygenates content and increase in the phenolics and aromatics content, indicating that temperature is an important operating parameter influencing the yield and composition of bio-oil.
Keywords: Waste Mandarin Residue; Pyrolysis; TGA; Bio-oil
Optimum empty bed retention time for toluene degradation in a biofilter packed with ceramic beads by Donghyuk Jung; Jieun Lee; Byung-Woo Kim (1873-1875).
Toluene is a toxic air pollutant and a common constituent emitted from industrial processes including chemical manufacturing operations, painting, and petroleum refining. We previously developed a new biofilter system the degradation of acetone and MEK. In this study, we evaluate the optimum EBRT to achieve an effective elimination capacity (EC) with smaller filter bed volume. In addition, we optimized the operation conditions for toluene degradation using the same biofilter system.
Keywords: Biofilter; Toluene; Empty Bed Retention Time
Characteristics of sludge hydrolysis by ultrasound and thermal pretreatment at low temperature by Dong-Jin Kim; Yoosik Youn (1876-1881).
Ultrasonic treatment and thermal treatment at low temperature were employed together to analyze and compare the effect of temperature on ultrasonic sludge hydrolysis. Waste activated sludge was more susceptible to ultrasound than anaerobic sludge and primary sludge. In ultrasonic treatment of waste activated sludge for 1 hour, ΔSCOD/(−ΔVSS) ratio decreased from 2.40 to 0.44, indicating that high COD components were solubilized faster than the low COD components. Ultrasonic treatment increased the temperature significantly and the heat effect on sludge hydrolysis was not negligible. Primary sludge was more susceptible to heat than waste activated sludge. A sequential treatment of heat and ultrasound of primary sludge showed that hydrolysis efficiency was more affected by the ultrasonic power than the temperature and the time duration. In case of waste activated sludge, the overall hydrolysis efficiency increased with the temperature up to 50°C, and it remained almost constant at higher temperature. From the results the contribution of shear force by cavitation bubbles decreased at higher temperature. The effects of shear and heat in ultrasonic sludge treatment need to be analyzed separately for the optimum sludge pretreatment.
Keywords: Pretreatment; Sludge Hydrolysis; Solubilization; Thermal Treatment; Ultrasonic Treatment
A study on removal efficiency of phenol and humic acid using spherical activated carbon doped by TiO2 by Hye-Ju Jung; Ji-Sook Hong; Jeong-Kwon Suh (1882-1888).
This study aimed to find a way to remove organic pollutants, phenol and humic acid in aqueous solutions using TiO2 spherical activated carbon (Ti-SPAC). The Ti-SPAC was manufactured by resin ion-exchange and a heating process. This method was very effective not only in creating TiO2 on the surface of the supports evenly, but also in making activated carbon that has highly-developed micro pores. To estimate whether Ti-SPAC has the proper features as a photocatalyst and adsorbent, it was examined in detail by X-ray patterns, SEM image, EDXS, BET, EPMA. The results proved that Ti-SPAC is a very useful material for treating wastewater by photocatalysis and absorption.
Keywords: Ti-SPAC; Photocatalyst; Activated Carbon; Humic Acid; Phenol
Statistical assessment of starch removal from starchy wastewater using membrane technology by Javad Sargolzaei; Amin Hedayati Moghaddam; Jalal Shayegan (1889-1896).
The present work deals with application of 25-2 fractional factorial design (FFD) to evaluate the operating parameters on starch separation from synthetic starchy wastewater using a hydrophilic polyethersulfone membrane with 0.65 μm pore size in a plate and frame handmade membrane module. The analysis of variance (ANOVA) combined with F-test was also used to recognize non-significant terms. The performance of the filtration process was evaluated by calculating the COD removal percentage (rejection factor) and permeate flux. In this experiment, five input parameters were surveyed, including trans membrane pressure (TMP), flow and temperature of feed, pH and concentration of wastewater. In this experiment, real wastewater was not used but synthetic starchy wastewater was prepared using starch. Two models were obtained from experimental data, capable of predicting COD removal percentage and permeate flux in different conditions. The predicted values obtained from the regression models were close to the actual ones. For the reduction of fouling, cleaning in place (CIP) method was used.
Keywords: Starch; Removal; Membrane; COD; Permeate
Extractive bioconversion of xylan for production of xylobiose and xylotriose using a PEG6000/sodium citrate aqueous two-phase system by Xin Li; Zhina Lian; Bo Dong; Yong Xu; Qiang Yong; Shiyuan Yu (1897-1901).
Aqueous two-phase system (ATPS) was applied for extraction bioconversion of xylan by xylanase from Trichoderma viride. Phase diagrams for poly (ethylene glycol) (PEG) and sodium citrate were determined at room temperature. The ATPS composed of 12.99% (w/w) PEG6000 and 12.09% (w/w) sodium citrate was favorable for partition of xylanase and used for extraction bioconversion of xylan. Batch hydrolysis demonstrated that higher concentrations of xylobiose and xylotriose were obtained in the PEG6000/sodium citrate ATPS compared to those in the aqueous system. These results present the potential feasibility of production of xylo-oligosaccharides by extraction bioconversion in ATPS.
Keywords: Extractive Bioconversion; Xylanase; Xylobiose; Xylotriose; Aqueous Two-phase System
Effects of bmim[PF6] treatments with different concentrations on microbial activity of Saccharomyces cerevisiae by Xian-Liang Song; Sheng-Ying Ye; Ru Xie; Ling Yin; Xun Shi; Shu-Can Luo (1902-1907).
To study the role of ionic liquid as a solvent in whole cell biocatalyst, it is necessary to probe the effects of ionic liquid treatments on microbial activity. In this paper, Saccharomyces cerevisiae was selected as a test bacterium to study the effects of bmim[PF6] ionic liquid in different concentration on yeast activity through determining the growth curve, sugar degradation curve, microbial activity, colonial morphology and cell morphology. The results revealed that the growth of yeast is inhibited strongly in low concentration ionic liquid, while the lethal effect is feeble in high concentration ionic liquid. This result was totally different from that of supercritical CO2 treatment or high concentration benzene methanol treatment which would lead most yeast to death.
Keywords: Biocatalysis; Ionic Liquid; Yeast; Microbial Activity
Kinetics of glycerol effect on biodiesel production for optimal feeding of methanol by Wan Pyo Hong; Jae Yeon Park; Kyoungseon Min; Myung Joo Ko; Kyungmoon Park; Young Je Yoo (1908-1912).
The enzymatic production of biodiesel has been considered as an eco-friendly process. Candida antarctica lipase B (CalB) has been studied for its application for biodiesel production because of its high activity and stability. Enzyme deactivation caused by alcohol and effect of glycerol has to be resolved for the industrial application of this process. In traditional kinetic studies of biodiesel production, the effects of alcohol and oil were only considered in the kinetic equation, while the effect by glycerol was neglected. A new kinetic model incorporating glycerol effect is proposed in this paper. The proposed kinetic equation is applied by predicting the supplying rate of methanol in a fed-batch addition of methanol. The conversion rate was improved from 59.7% to 94.6% in a fed-batch by considering glycerol effect.
Keywords: Biodiesel; Enzyme; Kinetic Model; Oil; Glycerol; Lipase
Nanoparticle popsicle: Transdermal delivery of nanoparticles using polymeric microneedle array by Sun Ho Lee; Hyun Ho Lee; Shin Sik Choi (1913-1917).
A number of nanoparticles are currently applied for medical or medicinal research fields through conjugating with drugs or bio-molecules such as DNA, RNA, and peptides. There are three distinct ways to deliver nanoparticles into animal and human bodies: injection, feeding, and transdermal administration. We fabricated a polymeric microneedle array carrying nanoparticles on the end-tip of needles for an efficient delivery of functional nanoparticles through the skin. The polymeric microneedles with a length ranging from 600 to 1,000 μm were casted out using laser-printed PDMS (polydimethylsiloxane) molds where the 50 nm silica or polystyrene nanoparticles had been filled by centrifugation. When the microneedle array was applied to the porcine cadaver skin, nanoparticles were quickly and stably dispersed in the hypodermis. Microneedle array conjugated with nanoparticles has a potential for an alternative method to deliver cosmetic or pharmaceutical materials into human skin locally without professional procedures.
Keywords: Nanoparticle; Microneedle Array; Polymeric Needle; Drug Delivery
Establishment of a solvent map for formation of crystalline and amorphous paclitaxel by solvent evaporation process by Jae-Won Yoon; Jin-Hyun Kim (1918-1923).
This study intended to establish a solvent map for formation of crystalline and amorphous paclitaxel by a solvent evaporation process. Crystalline paclitaxel was produced by evaporation with polar solvents (acetone, acetonitrile, ethanol, isobutyl alcohol, methanol, methyl ethyl ketone, and n-butyl alcohol) having a polarity index above 4.00. On the other hand, amorphous paclitaxel was produced by evaporation with non-polar solvents (methylene chloride, n-butyl chloride, and toluene) having a polarity index of about 4.00 or lower. The formation of paclitaxel was very closely associated with the polarity index of the organic solvent used in the solvent evaporation process. In the case of crystalline paclitaxel, the higher the polarity index and the lower the viscosity of the organic solvent (n-butyl alcohol, methyl ethyl ketone, and acetonitrile), the higher the degree of crystallinity. In the case of amorphous paclitaxel, the shape and size of particles varied according to the solvent (methylene chloride, n-butyl chloride, and toluene) used in the solvent evaporation process.
Keywords: Paclitaxel; Formation Control; Solvent Evaporation Process; Solvent Map; Polarity Index
Measurement of thermal property of polystyrene using dual quartz crystal resonators by Young Han Kim (1924-1926).
A new device using dual quartz crystal resonators is proposed to determine the thermal property and morphological change of polystyrene. The resonators are installed in a small aluminum cell directly heated and air cooled according to the programmed temperature variation. The resonant frequencies of the dual resonators-one for reference and the other for sample-are measured and analyzed for the morphological change while their temperature varies. The temperatures of the changes are compared with the DSC thermogram and previously reported studies, and it is found that the measurements are comparable to those of the DSC. The proposed device is simple and easy to construct, and a portable system is available with some modification.
Keywords: Thermal Property Measurement; Quartz Crystal Resonator; Dual Resonator; Morphology Monitoring
Effects of sodium dodecyl benzenesulfonic acid (SDBS) on the morphology and the crystal phase of CaCO3 by Dae Ju Hwang; Kye Hong Cho; Moon Kwan Choi; Young Hwan Yu; Seung Kwan Lee; Ji Whwan Ahn; Gwang Il Lim; Choon Han; Jong Dae Lee (1927-1935).
The effects of anionic surfactant on the morphology and crystallization of calcium carbonate precipitated from CaCl2 and Na2CO3 were investigated. Although reaction temperature did not have an effect on the morphology of calcium carbonate, it did have an effect on the cluster size. The cluster size became bigger with high reaction temperature. With the addition of sodium dodecyl benzenesulfonic acid (SDBS), the morphology of precipitated calcium carbonate changed from cubic to porous spheres with over 98% of the crystal phase transformed from calcite to vaterite. The analysis of precipitates formed by the reaction of CaCl2 solution (from limestone (CaO 50% content)) and Na2CO3 found that the morphology of precipitated calcium carbonate changed from cubic to spherical, and the crystal phase changed from calcite to over 94% vaterite with the addition of sodium dodecyl benzenesulfonic acid. These vaterite structures were solid spheres rather than hollow ones.
Keywords: Calcium Carbonate; Anionic Surfactants; Calcite; Vaterite; Drug Delivery System
Highly improved adsorption selectivity of L-phenylalanine imprinted polymeric submicron/nanoscale beads prepared by modified suspension polymerization by Nasrullah Shah; Jung Hwan Ha; Mazhar Ul-Islam; Joong Kon Park (1936-1944).
Molecularly imprinted polymer (MIP) submicron/nanoscale beads selective for L-Phenylalanine (L-Phe) and D-Phe as well as non-imprinted beads were prepared by modified suspension polymerization involving agitation of the reaction mixture at high rotation speed under safe radical conditions. The effects of pH, template and concentration of racemate solution on the performance of the phenylalanine (Phe) imprinted polymeric submicron/nanoscale beads were studied. L-Phe-imprinted submicron/nanoscale beads prepared for the first time by modified suspension polymerization showed enhanced adsorption capacity and selectivity over those of D-Phe imprinted and non-imprinted beads. Maximum adsorption capacity, 0.35 mg/g, and selectivity, 1.62, of L-Phe imprinted submicron/nanoscale beads were higher than the adsorption capacities, 0.30 and 0.19mg/g, and selectivities, 1.59 and 1.02, of D-Phe imprinted and nonimprinted submicron/nanoscale beads, respectively. FE-SEM analyses revealed that L- and D-Phe imprinted beads were larger (100 nm–1.5 μm) than non-imprinted nanobeads (100–800 nm). 13C CP-MAS NMR spectroscopy helped in correlating the bead sizes and the extent of reaction during polymerization. Similarly, FT-IR study was used for evaluation of structural characteristics of the prepared Phe-imprinted and non-imprinted beads. The preparation of Phe-imprinted submicron/nanoscale beads with improved adsorption and separation properties and the study of effect of template on the size and performance of the prepared beads are suitable from both economical and research point of view in MIP field.
Keywords: Molecularly Imprinted Submicron/Nanoscale Beads; Modified Suspension Polymerization; FE-SEM; FT-IR; 13C CP-MAS NMR
Formation of MPEG-PLLA block copolymer microparticles using compressed carbon dioxide by In-Il Jung; Seungjoo Haam; Giobin Lim; Jong-Hoon Ryu (1945-1951).
Methoxy poly(ethylene glycol)-b-poly(L-lactide) (MPEG-PLLA) diblock copolymer was synthesized via ring-opening polymerization, and MPEG-PLLA microparticles were then prepared using an aerosol solvent extraction system (ASES) technique with compressed carbon dioxide as antisolvent. The MPEG-PLLA microparticles were prepared at temperatures ranging from 25 °C to 55 °C and at pressures from 85 bar to 150 bar. The concentration of MPEG-PLLA copolymer, solution flow rate, and CO2 flow rate were adjusted to be 0.5–3.0% (w/v), 0.3–1.0 mL/min, and 19 g/min, respectively. Relatively small spherical microparticles were prepared in the subcritical region at 25 °C, while agglomerated particles were obtained at temperatures above the critical point. The mean particle sizes of the MPEGPLLA microparticles prepared by the ASES varied from 9.53 μm to 46.9 μm depending upon the operating conditions.
Keywords: ASES; MPEG-PLLA; Compressed Carbon Dioxide; Microparticles
Sulfur fate during bituminous coal combustion in an oxy-fired circulating fluidized bed combustor by Lunbo Duan; Wu Zhou; Haixin Li; Xiaoping Chen; Changsui Zhao (1952-1955).
To clarify the sulfur transformation behavior during oxy-fired circulating fluidized bed (CFB) combustion, experiments on SO2 emission characteristics were carried out in a 50 kWth CFB combustor. Results show that SO2 emission is quite dependent on the bed temperature in different atmospheres without limestone injection. With Ca/S=2.5, SO2 emission in 21%O2/79%CO2 atmosphere is smaller than that in air atmosphere, but SO2 emission decreases with the increase of O2 concentration. The calcium forms in the ash prove the combination of calcination/carbonation and direct sulfation mechanism of limestone under oxy-combustion conditions. And the desulfurization efficiency of limestone (as deducting the self-retention efficiency from the total sulfur removal efficiency) increases from 40% to 52% as the O2 concentration increases from 21% to 40%.
Keywords: Oxy-fuel Combustion; CFB; SO2 Emission; Desulfurization Efficiency
Experimental and model investigation on the mass balance of a dry circulating fluidized bed for flue gas desulfurization system by Yuan Li; Changfu You (1956-1963).
A moderate temperature dry circulating fluidized bed flue gas desulfurization (CFB-FGD) process was developed using rapidly hydrated sorbent. This technique has the advantages of low cost, no water consumption, and a valuable dry product CaSO4. To keep the system operation stable, a mass balance model, based on cell model considering flow state, particle abrasion, particle residence time, particle segregation and desulfurization processes, was built to predict the system state and optimize the operating condition. Experimental studies were conducted on a pilot-scale CFB-FGD system with rapidly hydrated sorbent made from CFB circulating ash and lime (circulating ash sorbent) or coal fly ash and lime (coal fly ash sorbent). Calculated results were compared with experimental results and the relative error was less than 10%. The results indicated that feed sorbent mass, feed sorbent size, superficial gas velocity, particle abrasion coefficient and cyclone efficiency had significant influence on the mass balance of CFB system. The circulating ash sorbent was better than the coal fly ash sorbent, for providing higher desulfurization efficiency and being better for the CFB-FGD system to achieve mass balance.
Keywords: CFB-FGD; Rapidly Hydrated Sorbent; Mass Balance