Influence of Pressure on High-Temperature Coal Pyrolysis Property and Coke Particle Formation at Entrained Flow Coal Gasifier Conditions

Abstract

The coal pyrolysis behavior, that is the initial reaction in the coal gasifier, is investigated to clarify phenomena in the gasifier of IGCC. Since pressurized entrained flow gasifiers are adopted for the almost all IGCC processes for large-scale power generation and these gasifiers are operated at a pressurized reducing atmosphere and high temperature, the influence of the pyrolysis temperature and pressure on the composi-tion and properties of the pyrolysis product was examined. As a result of rapid pyrolysis tests for three types of bituminous or semi-bituminous coal using a pressurized drop tube furnace facility (PDTF) in nitro-gen gas flow at high temperatures of over 1000 degrees Celsius and at high pressures of under 2.1MPa, the yield of the volatilized gas components decreased when pyrolysis pressure increased. The product char of pyrolysis tests was formed many more than fixed carbon in coal, and contained a large amount of fine particulates of carbon like coke or soot. For some coal types, the CO₂ gasification reactivity of the fine particulates was so lower than that of the char particles originated from fixed carbon that it could be said that the clarification of the formation mechanism of coke is important. The amount of the coke particulates existing outside char particles at pressurized pyrolysis tests was less than that of the coke particulates at 0.15 MPa because of deceleration of volatilization at primary pyrolysis reactions. Furthermore, it was con-firmed that the coke particulates were also formed at the conditions where gasifying agent existed like the inside of gasifiers.