Synergy effect in co-gasification of lignite and char of pine sawdust

Abstract

Pine sawdust was torrefied at 200, 300, and 400 ℃ in a muffle furnace, and used with Shengli lignite for co-gasification. Fourier transform infrared (FTIR) spectroscopy indicated that the pine sawdust torrefied at 200 and 300 ℃ contained the functional groups C―O―, ―CH3, and ―OH, while the pine sawdust torrefied at 400 ℃ was similar to lignite, containing the functional groups ―C=C―, ―C=O, and ―OH. That is, when the torrefaction temperature of the pine sawdust increased, the single bonds in functional groups were converted to double bonds. After torrefaction, individual gasification and co-gasification of the lignite and pine sawdust chars were studied and compared in a thermogravimetric analyzer and fixed-bed reactor. It was found that both experimental results were consistent. The gas yield of pine sawdust char by individual gasification was higher when the pretreatment temperature was increased. Co-gasification of pine sawdust torrefied 200 and 400 ℃ with lignite had a positive effect on the product gas yield, carbon conversion, and synergetic efficiency, and the synergetic effects for sawdust torrefied at 200 ℃ were less than those for sawdust torrefied at 400 ℃. In contrast, pine sawdust torrefied at 300 ℃ had some inhibitory effects for co-gasification with lignite. Considering both the thermogravimetric analysis and fixed bed experiments, it is concluded that the synergetic effects can be attributed to the alkali metal and the hydrogen atomin the pine sawdust chars occurring at the pyrolysis stage.