炉排垃圾焚烧飞灰二级逆流水洗特性

Two-stage countercurrent water-washing characteristics of municipal solid waste incineration fly ash from grate furnace

以炉排垃圾焚烧炉飞灰为研究对象,分析水洗液固比和时间对飞灰中氯盐溶出的影响,对二级逆流水洗工艺展开研究.通过模拟飞灰的二级逆流水洗工艺,建立水洗所产生废液中的氯质量浓度、残渣中氯质量分数的理论计算模型.结果表明,当水洗液固比为6 mL/g、水洗时间约为20 min时,氯盐溶出质量达到稳定;飞灰经一级、二级水洗后的质量损失分别约为32%、37%;在相同液固比下,与一级水洗相比,二级逆流水洗可以提升飞灰的脱氯效果,当水洗液固比为2～6 mL/g时,提升率可达15.40%～61.15%;模型所得的理论计算值与实验实测值相关性好、均方根误差小. 2种水洗工艺产生的水洗废液中COD、氨氮质量浓度和pH值均高于《污水排入城镇下水道水质标准》的规定,在被排入城市污水系统之前须经过进一步处理.

The effects of washing liquid-solid ratio and time on dissolution of chlorine salt in municipal solid waste incineration (MSWI) fly ash, sampled from a grate furnace were analyzed. The research about two-stage countercurrent water-washing process was carried out. The theoretical calculation models of chlorine mass concentration in washing solution as well as chlorine mass fraction in washed residue were built under the simulation of two-stage countercurrent water-washing process. Results showed that chlorine dissolved quantity became stable when the liquid-solid ratio was 6 mL/g and the time was about 20 min. The mass loss of fly ash after primary and secondary washing was about 32% and 37%, respectively. Two-stage countercurrent water-washing can obviously promote the removal of chlorine from fly ash at the same liquid-solid ratio, compared with primary water-washing. The removal of chlorine from fly ash increased by 15.40% to 61.15% when the liquid-solid ratio was 2 to 6 mL/g. The calculated values obtained from the theoretical models had good correlation with the measured values and the root-mean-square-error was small. The pollutants in the washing solution generated from the two washing processes, such as COD, mass concentration of NH3-N, and pH value exceeded the discharge standard in wastewater quality standards for discharge to municipal sewers, thus the washing solution need further purification before being discharged into the urban sewage system.