Study On Co-gasification Characteristics Of Wheat Straw And Mengdong Lignite

With the rapid consumption of fossil resources and the ecological environment worsening, biomass energy, as clean and renewable resources, attract the world’s attention. Co-gasification of biomass and coal contribute to reduce carbon emissions and the environmental pollution, realize the clean energy conversion of biomass and make full use of low grade coal.Wheat straw and Mengdong lignite were selected for the study, co-pyrolysis property of samples, gasification characteristics of cokes with CO2 have been researchedthrough thermo-gravimetric analyzer,and dynamics analysis were carried out. The cokes were obtained from mixtures of lignite and wheat straw pyrolysised in muffle furnace.The cokes’ gasification characteristics of steam gasification、CO2 gasification and air/steam gasification at 900-1050℃ have been researched through tube furnace。The results are shown as follows:The thermogravimetric experiments showed that: The reaction activity of wheat straw is higher than lignite, the thermal decomposition almost finished at 410℃, while the lignite appeared weight loss obviously at 300℃. There is almost no synergistic effect in co-pyrolysis process. with heating rate increasing, the corresponding temperature rose,but the final conversion changed hardly.Thermogravimetric experiments of coke with CO2 showed that: The reaetion exponent and the mean specific gasification rate of mixing coke increased with the blend ratio of wheat straw increasing.Compared with homogeneous reaction model and parabola model, the unreacted-core shrinking model was suitable for the gasification of cokes, whilewhen the gasification temperature was 900℃, The homogeneous reaction model was suitable for the gasification of lignite coke, when the gasification temperature was 1000℃, the parabola model was suitable for the gasification of coke made by the lignite mixed straw in mass ratio of 20%. The nonisothermal gasification of coke showed that, apparent activation energy increased with the promotion of gasification temperature. And there is a kinetic compensation effect between apparent activation energy and pre-exponential factor.Ativation energy increased with higher mixing ratio of wheat straw at same gasification temperature zone.Gasification of coke with H2 O showed that: With the gasification temperature rising from 900℃ to 1050℃, the carbon conversion, the gas calorific value, the syngas content and the CO content increased, while the H2 content decreased. With the wheat straw mixing proportion increasing, the carbon conversion rose, but the gas compositions of gasification and gas calorific value changed hardly.Gasification of coke with CO2 showed that: With the gasification temperature rising from 900℃ to 1050℃, the content of CO rose. The gasification of cokes from lignite mixed with wheat straw showed that: A higher mixing ratio of wheat straw contributed to higher CO content.Gasification of coke with air/steam showed that: The volume ratio of the air and steam was 1:2 in the gasification agent.With the gasification temperature rising from 900℃ to 1050℃, the CO content, the H2 content and the gas calorific value rose for the lignite coke gasification. When the gasification temperature was 900℃, with the mixing ratio of wheat straw increasing from 0% to 60%, the H2 and CO content rose 10%, H2/CO changed from increase to decrease, and the gas calorific value rose.