Oxygen Gasification of Municipal Solid Waste in a Fixed-bed Gasifier

Four waste materials, paper, wood, textile and kitchen garbage, in municipal solid waste were gasified separately with oxygen in a fixed bed reactor. The yields of products char, tar and gas, the composition of gas components H2, CO, CO2 and CH4, and the lower heating value (LHV) were examined at temperatures between 700 and 900 °C and equivalence ratio (ER) between 0.14 and 0.32. Characteristics of gas evolution during gasification were investigated. Results show that a higher temperature improves the formation of H2 and CO while lowers the yield of CO2 and CH4. The LHV of syngas increases with temperature and varies in the range of 6–10 MJ·m− 3, reaching the maximum at 800 °C or above. As ER increases, both combustible gas component and LHV of syngas decrease while the yield of CO2 rises linearly. The appropriate ER for obtaining high quality gas is in the range of 0.18–0.23. Temperature and ER have significant effects on the product distribution. Higher temperature and ER are favorable for higher gas yield and lower yield of char and tar in the gasification of textile and kitchen garbage. At 800 °C, the gas evolution may be divided into two regions. In the first region, the flow rate of gas increases and then decreases rapidly, while in the second region the flow rate decreases monotonically to lower level.

The evolution of gas flow rate at 800 °C can be divided into two regions. The initial region is characterized by a high flow rate of gas components and a subsequent steep decrease, while the second region is a period of a monotonically decreasing gas flow rate. The flow rate change in the first region could be attributed to the evolution of volatile matter from the MSW. In the second region, the char gasification and reforming reactions may play a primary role. The two regions are not completely independent since the cracking and char gasification reactions also occur in the initial devolatilization.Figure optionsDownload as PowerPoint slide