神木煤灰自身固硫的微观特性分析

当管式炉温由800 ℃升高到1 200 ℃时，神木煤灰的自身固硫率由63.5%降低到6.4%。晶相组成、孔隙结构和表面形态分析表明，800 ℃煤灰自身固硫渣样中CaSO4的质量分数高达18%，CaCO3和CaO的质量分数高达22.4%。渣样表面呈蓬松的棉絮状结构，颗粒内部有许多均匀密布的细小孔隙。1 200 ℃渣样中的CaSO4已全部分解，并且不存在任何CaCO3或CaO晶相，渣样表面由许多结构密实、表面光滑的块状颗粒组成，带有明显的烧结胀大和高温熔融的痕迹。1 200 ℃渣样的比表面积、孔容积和平均孔径等比800 ℃时急剧减小。

Microstructures of self-desulfurization residue of Shenmu coal ash in combustion

The sulfur-retention properties and microstructures of Shenmu coal ash are studied. It is found that the self-desulfurization efficiency of Shenmu coal with an initial molar ratio Ca/S of 1.45 dramatically decreases from 63.5% to 6.4%, when the furnace temperature increases from 800 ℃ to 1 200 ℃. The reason is that the active calcium (CaCO3 and CaO) content is 22.4% to give a sulfation product CaSO4 content of 18% in the combustion residue at 800 ℃. It is composed of many small particles with fine pores (specific surface area of 4.6 m2·g－1 and mean pore diameter of 14.2 nm), which form a loose cotton-like structure and provide large surface area for sulfation reaction. But none of the phases of CaCO3, CaO and CaSO4 is found in the coal ash at 1 200 ℃. It is composed of many large nonporous particles with smooth surfaces (specific surface area of 2 m2·g－1 and mean pore diameter of 5.5 nm), due to the high levels of sintering swell and melting.