Distributions of Gaseous Products from the Flash Pyrolysis of Coal and Biomass in Coal Topping Process

The flash pyrolysis experiments of coal, biomass and their mixture under the simulative conditions of coal topping process were carried out. The effects of pyrolysis temperature and samples on the yield of products, compositions of gas and net calorific value of gas were studied. The results showed that pyrolysis of the mixture of lignite and biomass obeyed the pyrolysis law of single substance, but the additive amount of biomass affected the yield of pyrolysis products. When the mass ratio of biomass to lignite was less than 1:1, the yield of gas increased from below 50% to above 60%, however, while the addictive amount of biomass increased to over 50%, the yield of gas decreased 5%. For the gaseous compositions of pyrolysis of lignite, biomass and their mixture, there were similar changing rules, CO2 was the main component, followed by CO, H2 and hydrocarbon gases. Among hydrocarbon gases, the content of CH4 and C3H6 was higher than that of C2H4, C2H6 and C3H8, and that of C4H8 the least. In addition, the content of CH4 in the gas from the mixture pyrolysis was 20% higher than that from lignite pyrolysis. Pyrolysis temperature had a significant effect on net calorific value of gas, which was increased at high temperature. Under the condition of 500-800 ℃of pyrolysis temperature and mass ratio of biomass to lignite at 1:2, the net calorific value of gas increased from 11.38 to 16.10 MJ/m3. Therefore, high yield and calorific value of gas could be obtained for flash pyrolysis of the mixture of lignite and biomass in coal topping process.