The Investigation of the Coal Ignition Temperature in Oxygen-Enriched Atmosphere by TGA

Abstract

The oxygen-enriched Circulating fluidized bed (CFB) combustion technology is a new method to reduce CO2 emissions. The coal ignition temperature, Ti, in an oxygen-enriched CFB boiler is an important parameter for designing the startup burner and for choosing the operating strategy during the startup process. Comparing with the complicated operation in real oxygen-enriched CFB boiler or in a laboratory scale fluidized bed (FBR), thermo gravimetric analyzer is a more simple and convenient method to determine the Ti, because the TGA results would be related in some way with the field results. Thermo gravimetric analyses of seven different types of coal were operated in air and oxygen-enriched atmosphere (O2 40%, CO2 as balance gas), with three different heating rate (10, 20, and 30 K/min). It was found that the Ti, determined by the DTGA, decreased with the O2 concentration increasing. The coal with the higher volatile content had a lower ignition temperature. The influence of the heating rate on the Ti was relatively significant. With 40% O2, the coal ignition temperatures firstly increased and then decreased with the increasing heating rate. Compared with the tests results obtained in a laboratory scale FB, the results obtained by these two methods have the same tendencies, and there must be a way to make the TGA results relative to the real coal ignition temperatures in the oxygen-enriched CFB boilers.