Experimental Study On Medium-Low Temperature Pyrolysis Of Low Rank Bituminous Coal And Characterization Of Pyrolysis-Derived Products

Integrated utilization by medium-low temperature pyrolysis is one of efficient and economic ways of low rank bituminous coal (LRC) conversion and utilization. Jixian coal and Dongrong coal, typical LRCs in China, were characterized and evaluated with aids of modern analysis instruments, and then they were pyrolyzed at medium-low temperature using thermogravimetry, electric tube furnace and muffle furnace, respectively. The effects of pyrolysis parameters on products’distribution, composition and properties were studied, and the new indices which could be used to quantitatively and accurately evaluate low-rank bituminous coal’s pyrolysis reactivity and char’s gasification reactivity were proposed. In accordance with the requirements for feedstocks of pyrolysis products’utilization, the composition and properties of products and pyrolysis parameters were related.The results show that because of its high contents of volatility, vitrinite, exinite and oxygen functional groups, and low contents of cohesiveness, ash and sulfur, Jixian coal and Dongrong coal are suitable for medium-low temperature pyrolysis. The pyrolysis temperature is the most influential factor among pyrolysis process parameters. The yield and composition of products almost do not change with the variation of heating rate. When the pyrolysis time is more than90min, there is little change in the yield and composition of products. The grindability and forecasting slurry ability of Jixian and Dongrong semicokes pyrolyzed at450℃are best. The gasification reactivity, combustion reactivity and resistivity of semicokes decrease with pyrolysis temperature increasing. The light fractions in tars derived from Jixian coal pyrolysis at450℃and Dongrong coal pyrolysis at400℃is highest, the heavy fractions in tars derived from coal pyrolysis at500℃is highest, and the content of low-rank phenol in tars derived from Jixian coal pyrolysis at450℃and Dongrong coal pyrolysis at400℃is highest. The caloric value of gas increases with pyrolysis temperature increasing. The Pyrolysis Characteristic Index P and Gasification Reactivity Index HG can be used to evaluate low-rank bituminous coal’s pyrolysis reactivity and char’s gasification reactivity quantitatively and accurately. The pyrolysis parameters suitable for products’utilization are optimized based on the relationship between property and pyrolysis parameter.