Characteristics of the Blockage from Air Nozzle Guide Duct in Circulating the Fluidized-Bed Coal Gasifier and Its Formation Mechanism

In this paper, the blockages in the air nozzle duct were divided into two types of wall layer blockages (WLB) and central layer blockages (CLB), and the composition, microstructure and formation mechanism of the blockages were analysed. The analysis revealed that the WLB had a high content of Fe, Cr and Ni, and was mainly mesoporous with a semi-open pore structure closed at one end. The CLB contained more organic matter and inorganic minerals, the strongest absorption peaks of organic matter were mainly Self-associated OH, while the absorption peaks of inorganic minerals were mainly asymmetric Si-O-Si functional groups. It was assumed that the blockage was mainly caused by the difference in resistance at the outlet of the air nozzle, resulting in a flow dead zone at the bottom of the gasifier, which caused the ash to overcome the resistance and leak into the air nozzle.