In situ desulfurization during combustion of high-sulfur coals added with sulfur capture sorbents

Two Chinese coals, added with two types of sulfur capture sorbents, were combusted. in a drop tube furnace to investigate effect of reaction temperature on sulfur removal during coal combustion. Limestone was used as sorbent and mixed with coal physically for sulfur removal. In addition, another sorbent, calcium acetate, synthesized from natural limestone, was also used for in situ removal of sulfur; it was impregnated into raw coals before combustion. The first series of experiments were carried out in the furnace having downside temperature of 1173 K (the upper side of furnace was at 1573 K). The results proved that calcium acetate captured more sulfur than limestone. In order to understand the effect of reaction temperature on in situ sulfur removal of sorbents, the second series of experiments were carried out at the uniform furnace temperature ranged from 1373 to 1673 K. Moreover, the sulfur removal capability of ashes, taken from combustion of coal with sorbents in drop tube furnace, was studied at 1173 K using thermogravity. The calcium distribution in ashes was analyzed using a novel calcium-based compounds CCSEM category. The results indicated that at certain temperature, higher sulfur removal efficiency was obtained for calcium acetate than that for natural limestone, which is mainly due to the fine dispersion of calcium in impregnated coal so that a good contact was obtained between calcium and sulfur-containing coal particles; increasing the temperature lowered the sulfur removal capabilities of sorbents since the sorbents were captured by inherent aluminosilicate; the sulfur content in raw coal affects the utilization of sorbents significantly in coal combustion. In addition, ashes, rich in calcium, can adsorb SO2 at 1173 K; the sulfur removal efficiency of fly ash is at least the same as that of natural limestone. (C) 2002 Elsevier Science Ltd. All rights reserved.