焦化脱硫废盐在水-乙醇体系下溶析提纯

PURIFICATION OF COKING DESULFURIZATION WASTE SALT UNDER A WATER-ETHANOL SYSTEM

基于硫氰酸钠(NaSCN)和硫代硫酸钠(Na_(2)S_(2)O_(3))在水-乙醇体系下的溶解度,通过脱色与水-乙醇体系分溶分离法对焦化厂2类脱硫混盐进行分盐提纯,得到纯度为94%~96%的NaSCN产品及纯度为95%~98%的Na_(2)S_(2)O_(3)产品,其中第一类废盐(白色,改良ADA脱硫法)中NaSCN和Na_(2)S_(2)O_(3)的回收率分别为90.8%和68.3%,第二类废盐(绿色,PDS脱硫法)中NaSCN和Na_(2)S_(2)O_(3)的回收率分别为91.3%和81.8%。通过XRD、TG-DSC以及FT-IR等表征手段分析发现,经过水-乙醇体系分溶分离法提纯分离后的产品接近市售的纯NaSCN和Na_(2)S_(2)O_(3)的品质。因此,水-乙醇体系可以代替无水乙醇、甲醇等纯溶剂对废盐进行分离提纯,且操作过程相对安全;此外,与分步结晶工艺相比,该工艺具有产品纯度高、耗能少等优点。因此,脱色与水-乙醇体系分溶分离法对焦化脱硫废盐的资源化利用具有一定的理论和实践参考价值。

Based on the analysis of solubility of sodium thiocyanate(NaSCN) and sodium thiosulfate(Na_(2)S_(2)O_(3)) under a water-ethanol system,two types of desulfurization mixed salts in the coking plant were chosen for further purification and separation through decolorization and water-ethanol system separation method.NaSCN products with a purity of 94% to 96%,and Na_(2)S_(2)O_(3) products with a purity of 95% to 98% were obtained respectively.Among them,the recoveries of NaSCN and Na_(2)S_(2)O_(3) in the first type of waste salt(white,improved ADA desulfurization method) were 90.8% and 68.3%,respectively,and the recoveries of them in the other waste salt(green,PDS desulfurization method) were 91.3% and 81.8%,respectively.Besides,desulphurization waste salt and products were detected and analyzed by XRD,TG-DSC and FT-IR,which showed that the quality of the products by the water-ethanol system separation method was similar to that of commercially available NaSCN and Na_(2)S_(2)O_(3).Hence,instead of absolute ethyl alcohol,carbinol and other pure solvents,the water-ethanol system made the operational process relatively safer.In addition,compared with the step crystallization process,the method had the advantages of high purity of products,less energy consumption.Therefore,the water-ethanol system separation method had certain theoretical value and practical significance for the resource utilization of coking desulfurization waste salt.