Abstract: The main component of calcium carbide slag (CCS) is calcium hydroxide [Ca(OH)2], which can replace limestone ore for wet flue gas desulfurization, but the desulfurization byproducts of calcium sulfite particles are small because of the strong alkalinity of CCS, which may affect the oxidation of calcium sulfite and the crystallization of calcium sulfate (CaSO4). The effects of different process conditions on particle size, oxidation rate, water content, and microcosmic appearance in the process of calcium sulfate oxidation and gypsum crystallization were systematically investigated, and the optimal process condition (calcium sulfate content of 5 g/L, aeration rate of 400 mL/min, initial pH value of 5.5, reaction temperature of 40℃, and reaction time of 4 h) was obtained. The byproduct of desulfurization gypsum (mainly calcium sulfate dihydrate) with large particle size, low water content, high purity, and uniform appearance was obtained under the optimal condition, which is conducive to the subsequent resource utilization of desulfurization gypsum. The leaching sequence of each element in the CCS under the actual operating pH conditions of the CCS slurry (acidic conditions) is Na>Ca>Mg>Si>Fe>Al. The effects of impurities of Na, Mg, Si, Fe, and Al in the CCS on the oxidation process of calcium sulfate and the crystallization of calcium sulfate were investigated under the above optimal reaction condition. The results indicated that Mg, Si, and Fe in the CCS had a significant promotion effect on the oxidation rate of calcium sulfate, while Al and Na in the CCS inhibited the oxidation of calcium sulfate. At the same time, the addition of Si impurity had almost no effect on the crystallization of calcium sulfate, the addition of the impurities of Mg, Fe, and Na had less effect on the crystallization of calcium sulfate, and the addition of Al impurity had a significant adverse effect on the crystallization of calcium sulfate. In this study, the CCS-based calcium sulfate was used as the raw material, and the study of calcium sulfate oxidation and gypsum crystallization was carried out, providing theoretical guidance for the forced oxidation process in the actual industrial desulfurization.

Key words: calcium carbide slag, wet desulfurization, calcium sulfite, oxidation, impurity

摘要： 电石渣主要成分为氢氧化钙，可以代替石灰石进行湿法烟气脱硫，但是电石渣的碱性较强，脱硫产物亚硫酸钙颗粒细小，可能会影响其氧化结晶过程。系统考察了不同工艺条件对亚硫酸钙氧化及硫酸钙结晶过程中粒径、氧化速度、含水率及微观形貌的影响规律，并得到优化的工艺条件：亚硫酸钙浓度为5 g/L，曝气量为400 mL/min，初始pH为5.5，反应温度为40℃，反应时间为4 h；在最优条件下得到了粒度大、含水率低、纯度高和形貌均匀的脱硫石膏(主要为二水硫酸钙)产品，有利于其后续的资源化利用。电石渣在酸性条件下各元素浸出的先后顺序为Na>Ca>Mg>Si>Fe>Al；在上述最佳反应条件下考察了Na, Mg, Si, Fe, Al等杂质对亚硫酸钙的氧化过程及硫酸钙结晶的影响，结果表明，Mg, Si, Fe对亚硫酸钙氧化速率有明显促进作用，而Al, Na抑制亚硫酸钙氧化；同时添加杂质Si对硫酸钙结晶几乎无影响，添加杂质Mg, Fe, Na对硫酸钙结晶影响较小，而添加杂质Al对硫酸钙结晶有明显不利影响。本研究以电石渣基亚硫酸钙为原料，开展了亚硫酸钙氧化与二水硫酸钙结晶研究，为工业实际电石渣脱硫的强制氧化过程提供理论指导。

关键词: 电石渣, 湿法脱硫, 亚硫酸钙, 氧化, 杂质