Effect of reactions in small eddies on biomass gasification with eddy dissipation concept – Sub-grid scale reaction model

• Published in: Bioresource technology Vol. 211; pp. 93 - 100
• Main Authors: Chen, Juhui, Yin, Weijie, Wang, Shuai, Meng, Cheng, Li, Jiuru, Qin, Bai, Yu, Guangbin
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2016
• Subjects: Biomass gasification; Bioreactors; Bubbling fluidized bed; Catalysis; EDC-SGS reaction model; Fermentation; Gases - metabolism; Large-eddy simulation; Models, Theoretical; SGS reaction rates; Temperature; SGS reaction rates; Biomass gasification; EDC-SGS reaction model; Bubbling fluidized bed; Large-eddy simulation
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2016.02.139

The figure shows the comparison of outlet gas composition molar fractions with experimental data. The maximum, minimum and averaged values of experimental data summarized from 18 kinds of wood are given. It can be seen that the simulation results are within an acceptable range of experimental results. The simulation results without EDC-SGS reaction model are also given in the figure. The CO and H2 molar fractions with EDC-SGS reaction model are lower than that without EDC-SGS reaction model. Because the EDC-SGS reaction model considers the effect of sub-grid scale eddy on CO and H2 oxidation process, the total reaction rate is increased. Accordingly, the CO2 molar fraction with the EDC-SGS reaction model is higher than that without the EDC-SGS reaction model. The N2 molar fraction with the EDC-SGS reaction model is higher than that without the EDC-SGS reaction model. The total reactions rates of gas oxidation are increased, which makes the gas volume in the furnace decreased. Owing to an invariant N2 amount, the molar fraction of N2 is relatively increased. [Display omitted] •The EDC-SGS reaction model is proposed for biomass gasification in BFB.•The simulations with present model are in better agreement with experimental data.•The SGS reaction rates with concentration and temperature are analyzed.•The SGS homogeneous reaction rates account for 15% of total.•The heterogeneous reaction rates with present model are improved 10–15%. Large-eddy simulation (LES) approach is used for gas turbulence, and eddy dissipation concept (EDC)-sub-grid scale (SGS) reaction model is employed for reactions in small eddies. The simulated gas molar fractions are in better agreement with experimental data with EDC-SGS reaction model. The effect of reactions in small eddies on biomass gasification is emphatically analyzed with EDC-SGS reaction model. The distributions of the SGS reaction rates which represent the reactions in small eddies with particles concentration and temperature are analyzed. The distributions of SGS reaction rates have the similar trend with those of total reactions rates and the values account for about 15% of the total reactions rates. The heterogeneous reaction rates with EDC-SGS reaction model are also improved during the biomass gasification process in bubbling fluidized bed.