Catalytic reforming of volatiles in pyrolysis by using biomass carbon particle loading Ca and Fe and improving biogas yield

Abstract: In order to improve the catalytic function of biochar on the pyrolysis volatiles of corn straw, biochar-Fe and biochar-Ca catalyst particles pyrolyzed from corn straw particles with Fe2O3 and CaO additives. Then the catalytic reforming ability of the different catalysts (no catalyst, biochar, biochar-Fe and biochar-Ca) were tested and discussed. The results showed that the liquid yield of corn straw particles reached the lowest value of 35.06% and the highest gas yield of 36.95% at the temperature of 800 ℃ without catalyst; The liquid products of corn straw particles mainly consisted of organic compounds such as acids, aldehydes, alcohols, phenols, ethers and lipids; The components of pyrolysis gas mainly include CH4, CnHm, CO, CO2 and H2. It was obvious that the biochar catalyst particles influenced the pyrolysis volatile matter of corn straw particles. Compared with the treatment without catalyst, the liquid yield of treatment with biochar catalyst particles decreased, the lowest was 21.49%; the gas yield increased, and the highest value was 50.72%. Biochar-Fe catalyst particles play an important role in the high temperature condition and especially at 800 ℃, the liquid phase yield reached the lowest value of 20.24% and the gas yield was 51.44%. By adding biochar-Fe, the volume fraction of H2 in the gas product increased, and the volume fraction of H2 in the gas product was 28.39% at 800℃, which was higher than that in the pyrolysis gas of corn straw without using catalyst under the same conditions at 12.52 percent point. Moreover, biochar-Fe catalyst particles contributed to stop the formation of macromolecule organic matter in pyrolysis oil; Fe can be used as a good additive to produce hydrogen-rich gas at high temperature. A good catalytic reforming effect on the liquid phase substances in the volatile matter of corn straw pyrolysis at various temperatures was obtained at treatment with biochar-Ca catalyst particles. The liquid yield and gas yield reached the optimum values of 20.01% and 51.96% at 800 ℃ with biochar-Ca catalyst particles, so the biochar-Ca catalyst could promote the formation of CH4 gas with high calorific value in pyrolysis gas, which could reach 12.69% under the optimum experimental conditions, and reduced the volume fraction of CO2, the lowest value of CO2 was 30.25%. CaO could be used as a good acceptor of CO2 to produce high calorific value fuel gas. By using the method of variance analysis, it was found that the P value of different kinds of catalyst was 4.9×10-6, which indicated that different kinds of catalysts had a very significant effect on the pyrolysis oil of corn straw particles. According to the analysis of liquid phase yield and gas yield, the order of activity of biochar-based catalysts for the catalytic reforming of corn straw pyrolysis volatiles was biochar-Ca > biochar-Fe > biochar > no catalyst.