Molten iron oxysulfide as a superior sulfur sorbent. Technical progress report, June 1--August 31, 1992

Abstract

Slagging combustors with injected lime or limestone are being considered as replacements for conventional coal burners. They have advantages in that they can be staged to reduce NO{sub x} and SO{sub x} emissions. Iron oxide, as an alternative to lime or limestone may be effective not only as a desulfurizing agent, but under the right conditions of oxygen potential and after combination with sulfur, the reaction products of coal gases with iron oxide can act as a flux to produce a fluid phase. The thermodynamic conditions for optimum removal of sulfur from the first stage of a coal combustor are being determined by experiment and by use of existing data. Analysis of the phase equilibria indicates that optimum conditions for deployment of the reducing stage of a multi-stage burner operating with iron injection are close to the boundary of the liquid iron oxysulfide phase with iron-saturation. In this quarter, three sets of experiments are being conducted: Equilibration at 1400{degree}C between gas atmospheres containing oxygen and sulfur at controlled chemical potentials over oxysulfide melts to determine activity/composition relationships for the ternary isotherm in the Fe-O-S system, Kinetics of reactions on milligram-scale between magnetite in a thermogravimetric device in simulated coal/gas atmospheres which are optimum for desulfurization, and Studies on a 3 million btu per hour burner located at a local utility plant (Northern States Power, High-Bridge Plant in Saint Paul, MN) in which magnetite is injected into simulated coal gas atmospheres (produced by combustion of acetylene [C{sub 2}H{sub 2}]) under reducing conditions.