Simultaneous Removal of SOx and Halogens under Combustion of Coal Water Mixture Added Fine Limestone

本文主要研究了石灰石在煤粉燃烧过程中脱除SOx和卤素的能力。讨论了煤中矿物与石灰石之间的反应对SO_2捕集的影响。研究中使用的三种中国煤(YZHS煤(硫含量=5.7wt%)、DT煤(S=1.7wt%)、VZLS煤(S=0.6wt%)具有明显的矿物组成和粒度分布。对煤和石灰石(硫钙摩尔比为1：3)混合燃料进行了燃烧试验。通过对飞灰的CCSEM分析，评价了添加的石灰石与硫磺和矿物的反应。YZHS煤的高岭石含量低于DT煤和YZLS煤，但矿物粒度较大。石灰岩的脱S和脱氯能力强烈地依赖于煤的类型。浸渍煤的燃烧具有较高的脱硫效率，这部分是由于脱硫剂与煤基质之间的紧密接触，部分添加的钙附着在煤表面，很容易吸附硫，钙与固有矿物的反应受到较大程度的抑制。此外，还研究了醋酸钙在煤中的浸渍，使醋酸钙在煤粒表面分散良好。醋酸钙的高分解速度降低了其在炉内的烧结度。这两个因素都是DT燃烧具有较高的脱硫效率的原因。在上端1200℃，下端900℃的脱硫剂中，以醋酸钙为脱硫剂的脱硫率可达80%以上，而石灰石的脱硫率仅为55%。醋酸钙的硫酸盐化速率越大，灰渣中形成的石膏和石膏/铝硅酸盐越多。

This report mainly focuses on SOx and halogen removal ability of limestone in the pulverized coal combustion. Effects of reactions between internal minerals in the coal with limestone on SO_2 capture are discussed. Three Chinese coals (YZHS coal (Sulfur content=5.7wt%), DT coal (S=1.7wt%), VZLS coal (S=0.6wt%)) used in this study have significant mineralogical composition and particle size distribution of minerals. The combustion experiment was conducted about the fuels that mixed coal and limestone (sulfur to calcium molar ratio is 1 to 3). The reactions of the added limestone with sulfur and minerals were evaluated by CCSEM analysis of fly ashes. YZHS coal has lower kaolinite content and bigger sized minerals than that of DT and YZLS coals. De-S and De-Cl ability of limestone depends strongly on the coal type. The higher desulfurization efficiency was achieved in combustion of impregnated coals, which is in part due to the intimate contact between sorbent and coal matrix, portion of added calcium adhered to coal surface, as a result, could adsorb sulfur readily, the reaction of calcium and inherent minerals was inhibited to larger extent. In addition, impregnation of calcium acetate into coal was developed, which made calcium acetate disperse well on the surface of coal particles. The high decomposition rate of calcium acetate decreased its sintering degree in the furnace. Both factors contributed to the higher desulfurization efficiency in DT combustion. In DTF having upside of 1200℃ and downside of 900℃, using calcium acetate as sorbent obtained the desulfurization efficiency more than 80%, compared to only 55% was obtained using limestone. The greater sulfation rate of calcium acetate led to much gypsum and gypsum/aluminosilicate formed in the ash.