Numerical simulation of perovskite dense membrane reactors for methane partial oxidation to syngas

03 Gaseous fuels (derived gaseous fuels) 02fOO358 Molecular and temperature aspects in catalytic partial oxidation of methane Basini, L. er al. J. Caral, 2000, 190, (2), 284-295. Heterogeneous stoichiometric oxidation and catalytic partial oxidation (CPO) of methane are studied at the surfaces of MgO, (I-AlzOs, and CeOz containing small Rh clusters. Stoichiometric reactions are linked to a repeating loop that has produced the CPO of methane at temperatures lower than 773 K with selectivity close to 100%. These reactions occur through the formation and the thermal decomposition of hydridocarbonyl Rh clusters. Molecular aspects of stoichiometric reactions are compared with those produced under stationary conditions with flows of premixed CH4 and Oz at very short residence time. Comparisons show that collisions between hydridocarbonyl clusters and gaseous Oz produce COz and HzO. IR thermography maps collected during short residence time CPO and gaseous temperature measurements are also reported. They show the existence of non-local thermal equild. between the solid and gaseous phases. 02/00359 Numerical model for pressurized fluidized bed coal gasifier Zhou, S., Jin, B. Meifan Zhuanhua, 2000, 23, (2), 59-66. (In Chinese) A numerical model was developed for a pressurized fluidized bed coal gasifier to determine the effects of operating parameters, coal properties, and design parameters on coal gasification. According to the results, bed pressure, and the air/coal and stream/coal mass ratios have effects. An experiment was performed in pilot equipment to verify the model. 02/00380 Numerical simulation of entrained flow coal gasifiers. Part I: modelling of coal gasification in an entrained flow gasifier Chen, C. el al. Chem. Eng. Sci., 2000, 55, (18), 3861-3874. A comprehensive three-dimensional simulation model was developed for entrained flow coal gasifiers. In the model, the numerical methods and the submodels conventionally used for the pulverized coal combustion modelling were used. An extended coal gas mixture fraction model with the Multi Solids Progress Variables (MSPV) method was applied to simulate the gasification reaction and reactant mixing process. Four mixture fractions were employed to separately track the variable coal off-gas from the coal devolatilization, char-Oz, char-COz, and char-Hz0 reactions. The influence of turbulence on the gas properties was taken into account by the pdf model with a clipped Gaussian distribution function. A series of numerical simulations were performed for a 200 t/d two-stage air blown entrained flow gasifier recently developed for the IGCC process. The predicted gas temperature profile and the exit gas composition were in general agreement with the measurements. Model simulations illustrating the importance of accounting for varying coal off-gas and the effects of turbulence/reaction affecting the prediction capability were also presented. 02/00381 Numerical simulation of entrained flow coal gasifiers. Part II: effects of operating conditions on gasifier performance Chen, C. et al. Chem. Eng. Sci., 2000, 55, (18), 3875-3883. The comprehensive entrained flow coal gasification model developed in Part I was used for parametric studies to provide a better understanding of two-stage air blown entrained flow gasifiers. A series of numerical tests was performed for the 200 t/d pilot-scale gasifier under various operating conditions (heterogeneous reaction rate, coal type, particle size, and air/coal partitioning to the two stages). The coal conversion, product gas composition, calorific value and gas temperature profiles throughout the gasifier were simulated. The results show that coal devolatilization and char oxidation were responsible for most of the carbon conversion (up to 80%) in the two-stage air blown entrained flow gasifier. The predicted carbon conversion was independent of devolatilization rate, sensitive to the chemical kinetics of heterogeneous reactions on the char surface, and less sensitive to a change in coal particle diameter. It was found that the air ratio had a significant effect on gasifier performance with strong coal type dependence. The effect of air/coal partitioning to the two stages, and the feed rate of recycle char was limited. 02/00382 Numerical simulation of perovskite dense membrane reactors for methane partial oxidation to syngas Chao, Y. ef al. J. Nat. Gas Chum, 2000, 9, (2), 119-131. An isothermal theoretical model for tubular perovskite dense membrane reactors has been developed for the simulation of methane partial oxidation to synthesis gas. The reaction kinetic rate expressions fitted to the literature experimental data for Ni/AlzOs catalysts are used for simulation. Three dense membranes of Lae.zBaO.sFer,.sCoa.zOs_ 6, Lao.2 Sra.sFeasCoa.zOs.~ and SrFeCoa.sO, with different oxygen permeation rates are applied to membrane reactors. The effects of membrane thickness, reactor size, reaction temperature, air flow rate and methane flow rate on CHI conversion, CO selectivity and HdCO

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Fuel and Energy Abstracts

January 2002

molar ratio have been discussed. A comparison between simulated results and the experimental data reported by Balachandran er al. has also been made. The simulation results suggest that the supported tubular membrane reactors are suitable for the perovskite materials of lower O2 permeability. 02lOO383 Partial oxidation of methane and ethane to synthesis gas over a LiLaNiO/y-A1203 catalyst Liu, S. et al. Appl. Card., A, 2000, 198, (1,2), 261-266. Partial oxidation of methane and ethane to synthesis gas over a LiLaNiO/r-AlzOs catalyst was investigated with a flow reactor, AAS, XPS, and XRD. Excellent reaction performance for CH4-CHzHe-Oz to synthesis gas over the LiLaNiOly-AlzOs is achieved at 1073 K, obtaining CO selectivity of 90-95% and CH4 conversion of ~97%. with a wide range of C2H6 content in the feed and of space velocity. Meanwhile, 100, 200 and 500 h life tests of the LiLaNiOly-AlzOs for natural gas-O* to synthesis gas were also performed. The results indicate that the LiLaNiOly-A1203 catalyst not only possesses excellent reaction performance (CHI conversion =95%, CO selectivity -98%), good carbon deposition resistance, but also has a relatively stable element component and a stable crystal phase structure during a 500 h life test experiment under conditions of 1123 K, natural gas/O* ratio of 1.90 and space velocity of 2.7~10’ L/ (kg h). 02lOO384 Partial oxidation of methane to syngas in a membrane reactor Jin, W. er al. Tianranqi Huagong, 2000, 25, (I), l-3, 11. (In Chinese) The partial oxidation of methane to synthesis gas was performed on a tubular Lao.sSra.4Coa.zFea.sO~.~ membrane reactor packed with a Nil?AlzOs catalyst. The effects of operation parameters (methane concentration in the feed and temperature) on the syngas reaction were investigated. The experimental results indicate that in the range of 825-885”C, the Ch4 conversion was larger than 96% with the CO selectivity > 97% at low methane concentration (~6%) in the fed and the mol ratio n (Hz)/n (CO)-2 in the product gas. 02lOO385 Partial oxidation of methane to syngas in a mixedconducting oxygen permeable membrane reactor Dong, H. er al. Chin. Sci. Bull., 2000, 45, (3), 224-226. Mixed-conducting oxygen permeable membranes represent a class of novel ceramic membranes, which exhibit mixed oxygen ionic and electronic conductivities. At high temperatures, oxygen can permeate through the membrane from the high to low oxygen pressure side under an oxygen concentration gradient. Theoretically, the permselectivity of oxygen is 100%. Recently, a novel mixed-conducting membrane-Baa.sSra.sCoa.sFea.zOs.~ has been developed, which shows extremely high oxygen permeability and promising stability. Furthermore, the reactor made with such membranes was successfully applied to the partial oxidation of methane to syngas reaction using air as the oxygen source, which realized the coupling of the separation of oxygen from air and the partial oxidation of membrane reaction in one process. At 850°C methane conversion >88%, CO selectivity ~97% and oxygen permeation rate of about 7.8 mW (cm* min) were obtained. 02lOO388 Partial oxidation of methane to syngas in fluidized bed reactor Ji, Y. et al. Cuihun Xuehao, 2000, 21, (2), 97-98. The partial oxidation of CHI with 02 to synthesis gas in a static fluidized-bed reactor was examined in the presence of 8 wt.% Ni/AlzOs catalysts. In comparison with a fixed bed reactor, in which CHd-02 feedstocks could ignite (light off) automatically at 530”, only after the catalyst was reduced in Hz or CH4 at 700” did the reaction take place in the fluidized bed reactor. The bed temperature gradient was