Study On The Characteristic Of Lignite Gasification With Carbon Dioxide And The Evolution Of Char Structural

Coal is one of the most abundant fossil energy in reserves in the world at present. Thelignite resources make up about40%of the total coal reserves. With the excessive use offossil fuels and the concerns over environmental protection, the resource utilization oflignite has attracted increasing worldwide interest. Lignite are the main coal resourcesavailable in China. The research and development of pyrolysis and gasificationtechnologies which can convert lignite resources to high-quality energy contribute toestablish sustainable energy system, promote the development of social economy. In recentyears, it has been found that char gasification with carbon dioxide can get highconcentration of carbon monoxide. Therefore, using carbon dioxide to gasify char hasimportant practical significance.The process of coal gasification is very complex, including the pyrolysis andgasification. Pyrolysis is the fundamental transformation of coal gasification, whosereactivity depends largely on the process of pyrolysis. Therefore, the pyrolysischaracteristics of typical Chinese lignite were firstly studied using thermogravimetric andderivative thermogravimetric (TG/DTG) analysis. The effect of heating rate evaluated inthe range of5-15oC/min providing significant parameters for the performance of the eachstage in the pyrolysis process. Thus, the three-dimensional anti-Jander model was used tosimulate the pyrolysis behaviors of the materials studied. Model parameters of pyrolysiswere given.The pyrolysis of lignite was studied using a bench scale fixed bed reactor coupled with aGasboard-3100gas analyzer. The original lignite samples and chars were characterized byultimate analysis, BET, SEM. The result showed that the atomic ratio of H/C and O/Cdecreased with increasing temperature, suggesting that the chars became progressivelymore aromatic and carbonaceous with increasing temperature. The change of BET specificsurface area during pyrolysis was similar for different lignite. The structural evolution oflignite during pyrolysis was studied and the release properties and formation mechanisms ofgases produced during lignite pyrolysis were investigated, which give a further understanding of lignite pyrolysis process.Finally, the carbon dioxide gasification of lignite chars was studied in a bench scalefixed bed reactor which is based on the depth understanding of the pyrolysis process. Somerepresentative lignite chars were chosen to carry out the experiment of the carbon dioxidegasification. The release properties of gas products were analyzed on-line. The effect of theheating rate and the final temperature were also analyzed. The result showed that,accompany with the increasing of pyrolysis temperature, the yield of CO is improvedobviously and the total release of slow pyrolysis char is higher than rapid pyrolysis char. theaverage release of all the pyrolysis char is proportional to the gasification temperature.