Abstract:

To promote the resource utilization of coal gasification slag and reduce the environmental pollution caused by heavy metals, this study took the gasification coarse slag from a coal chemical enterprise in Inner Mongolia as the research object. The microstructural characteristics, chemical element composition, heavy metal speciation, and risk assessment code (RAC) before and after washing were analyzed in detail. Under simulated acid rain (pH=4.5) and groundwater (pH=7.0) conditions, the leaching behavior of heavy metals in static and dynamic leaching processes was investigated to evaluate the potential environmental impact of using coarse slag as a filling material. The results showed that coal gasification coarse slag mainly consisted of amorphous aluminosilicates, with small amounts of quartz and calcite. After washing, the slag structure became loose, flocculent residual carbon was removed, and the adhesiveness and cohesion of the slag improved. The chemical composition of the washed slag remained dominated by SiO₂ and Al₂O₃, while the contents of CaO, K₂O, TiO₂ decreased, indicating that the washing process was effective in removing heavy metals. Heavy metals such as Cu, Pb, and Cr in the washed slag mainly existed in stable residual forms, with low proportions of exchangeable and carbonate-bound forms, suggesting low risks of desorption and release under acidic conditions. RAC analysis showed that the RAC values of Cu and Cr in the washed slag ranged from 1 to 10, indicating low risk, while the RAC value of Pb decreased to 30—50, indicating high risk. Static leaching experiments showed that under simulated acid rain conditions, the leaching concentrations of Cu, Pb, and Cr from the washed slag reached 590.4μg/L, 67μg/L, and 76.24μg/L, respectively. Dynamic leaching experiments under the same conditions showed that the leaching concentrations of heavy metals reached 298.6μg/L, 74.7μg/L, and 48.96μg/L, respectively. The leaching concentrations of heavy metals in both experiments were lower than the Class Ⅳ groundwater standards, indicating low environmental risks. It is suggested that the washed slag is suitable for use as a filling material in goaf grouting applications.

Key words: coal gasification coarse slag, heavy metals, static leaching, dynamic leaching, separated layer grouting, environment, leaching, sustainability

摘要：

为推进煤气化渣的资源化利用并减少其中重金属对环境造成的污染，以内蒙古某煤化工企业的煤气化粗渣为研究对象，深入分析了其淋洗前后的微观结构特征、化学元素组成、重金属形态组成和风险评价指数（RAC）；在模拟酸雨（pH=4.5）和地下水（pH=7.0）环境下，探究了煤气化粗渣中重金属的在静态浸淋和动态淋滤中的浸出行为，评估其作为充填材料可能对环境造成的影响。结果表明：煤气化粗渣主要由非晶态的硅铝酸盐构成，少部分是石英、方解石等。经过淋洗处理后，煤气化粗渣结构趋于松散，絮状残炭被去除，增强了粗渣的黏附性和结合力。淋洗后的粗渣化学成分仍保持以SiO₂和Al₂O₃为主，CaO、K₂O、TiO₂等金属氧化物含量下降，说明淋洗方法对于重金属的去除具有一定效果。淋洗后粗渣中的重金属Cu、Pb和Cr多呈现稳定残渣态，不易受环境影响释放，可交换态和碳酸盐结合态占比较小，说明在酸性条件下解吸、释放的风险较小。RAC分析说明，淋洗后粗渣中的Cu和Cr的RAC在1~10之间，属于低风险；Pb的RAC下降，在30~50之间，属于高风险。静态浸淋实验证明，在模拟酸雨的条件下，淋洗后的煤气化粗渣中的Cu、Pb和Cr的浸出浓度相对较高，最高分别达到了590.4μg/L、67μg/L和76.24μg/L；动态淋滤实验证明，在模拟酸雨的条件下，粗渣中的重金属浸出浓度同样相对较高，最高分别达到了298.6μg/L、74.7μg/L和48.96μg/L。两种浸出模拟实验中的淋洗后粗渣重金属浸出浓度均低于地下水Ⅳ类标准，表明其环境风险较低，适合作为离层注浆材料使用。

关键词: 煤气化渣, 重金属, 静态浸淋, 动态淋滤, 离层注浆, 环境, 浸取, 可持续性