Release of sulfur and chlorine gas species during coal combustion and pyrolysis in an entrained flow reactor

Abstract

The release of four sulfur and chlorine species (SO2, H2S, COS and HCl) from a US-American high sulfur high volatile bituminous coal under pyrolysis and combustion conditions was experimentally investigated in an entrained flow reactor. The reactor design and measuring techniques are presented. Under pyrolysis conditions, the reactor was operated at four wall temperatures (900, 1000, 1100 and 1300°C). With each reactor temperature increment, the release of sulfur from the coal was increased. Approximately 11% of total coal sulfur volatilized at 1300°C. Under combustion conditions, the same temperature influence already observed during the pyrolysis experiments applied for sulfur release. Under fuel rich conditions, SO2, H2S and COS were detected, with hydrogen sulfide being the major contributor. Under exactly stoichiometric and fuel lean conditions, almost all sulfur in the product gas occurred as sulfur dioxide. While at 1000°C, only 63–78% of coal sulfur was found in the gas phase, all sulfur was released when the reactor temperature was changed to 1300°C. During pyrolysis, hydrogen chloride concentration reached its final value at 1100°C. This temperature was sufficient to transform all volatile chlorine, which amounts to 15% of total coal chlorine, to the gas phase. While up to 50% of coal chlorine was released as hydrogen chloride during fuel rich combustion, no HCl was detected under stoichiometric conditions and with excess air.