Process simulation of staging pyrolysis and steam gasification for pine sawdust

A two-stage biomass pyrolysis and gasification scheme for pine sawdust are proposed. The process makes use of the gas produced by biomass pyrolysis and gasification. Part of product gas combusts in a burner outside of the gasifier and then produces the flue gas and heat required for pyrolysis and steam gasification. Aspen Plus software is used to simulate the process of staging pyrolysis and steam gasification for pine sawdust. By taking heat recovery, utilization and recycling of the product gas into consideration, the influence of temperature and the amount of steam on yield, carbon conversion rate, and lower heating value of the product gas are investigated. The results show that heat self-support is realized by combustion of 15–21% of the total product gas. As the gasification temperature increases, so do the content of H₂ and CO in the product gas, and the carbon conversion rate also increases. The lower heating value of the product gas reaches a minimum at 700 °C. With the increase of the steam amount, the yield of H₂ and CO increases, which lead to the increase of carbon conversion rate and the decrease of the lower heating value of product gas. The yield of CO decreases as the amount of steam increases. Meanwhile, the carbon conversion rate is almost 100% at 900–1000 °C, w(H₂O)/w(B) > 0.24. The lower heating value of product gas decreases with the rise of the steam amount.