The Study On Co-Gasification Process Characteristics Of Lignite With Biomass In The CO₂ Atmosphere

With the rapid development of Chinese economy, in the next few decades, coal is still in the significant status in China’s energy supply. In China’s coal reserves, lignite reserve accounts for 5.74%. The research of pyrolysis and gasification technologies which can convert lignite resources to high-quality energy contribute to promote the development of social economy. Biomass energy has been the hot issue of resource study because it is renewable and clean. Gasification is one of the most effective methods for the usage of lignite and biomass energy. Co-gasification of lignite and biomass under CO2 atmosphere shares the advantage of both gasification, and avoids the disadvantages of them. In co-gasification, in the meantime, the efficiency of gasification was improved and the tar cracking was promoted and the greenhouse gas of CO2 are reduced.Therefore, strengthening research the technology of co-gasification biomass and lignite in the atmosphere of carbon dioxide, has a certain practical significance.In this subject, pine sawdust and lignite were taken as represent of biomass and coal respectively. Several methods were used to research the co-gasification characteristics. The major contents and consequences were summarized as follows:Firstly, the gasification experiments of pine sawdust, lignite and the mixture samples, were carried out by thermogravimetric analysis technology under CO2 atmosphere. The influences of blending ratio and heating rate to the co-gasification process characteristics were emphatically investigated. The results showed, as the blending ratio of pine sawdust was increasing,the reactivity of samples could be enhanced and the eventual quality of the mixed samples could be decline. The max weight-loss rate and the peak temperature with max weight-loss rate of co-gasification pine sawdust and lignite moved to the direction of high-temperature side, and the range of temperature scale corresponding to weight-loss scale were all shown the positive trend underlying the gasification, and that a subsequent the reaction time was favorable to reduce along with the increasing of heating rate.Secondly, the atmospheric carbon dioxide gasification of lignite with pine sawdust was studied using a bench scale tube furnace reactor. The influences of blending ratio and gasification temperature to the co-gasification process characteristics were emphatically researched. In tube furnace gasification experiments showed that, with the respect of the increase of pine sawdust blending rate, the volume concentration of CO rose from 24.46% to 42.35%, CO2 decreased from 49.03% to 45.71%, H2 decreased from 4.87% to 4.14%, and CH4 rose from 0.32% to 0.68%. Accompany with the increasing of gasification temperature, the gas composition and heating value on the flammable gas of syngas was improved. At the same time, when the gasification temperature was around 950℃, the blending ratio of pine sawdust was 50%, the high co-gasification efficiency and heating values could be obtained.Thirdly, the co-gasification process of lignite with pine sawdust was simulated by PRO/II. The influences of blending ratio and gasification pressure to gas components were emphatically studied. The simulation results indicated that the volume concentration of H2 and CO was reciprocal to the gasification pressure, while the volume concentration of CO2 and CH4 was proportional to the gasification pressure. Accompany the blending rate of pine sawdust rose from 0% to 100%, it was found that the simulating values were well agreed with the experimental results on the gas compositions.