分步结晶法分离砷碱的工艺研究

The Process Research for Separation of Arensic-alkali Residue by Fractional Crystallization

在开展炼锑砷碱渣综合回收利用关键技术研究中,针对砷、碱难以分离的技术难题,研究在高温条件下,利用砷酸钠和碳酸钠在溶解度上的差异,采用分步结晶的方法,优先结晶分离出碳酸钠,实现砷酸钠和碳酸钠高效分离,并探讨了结晶碱通过饱和碳酸钠溶浸继续深度分离砷碱的工艺,分离获得的砷酸钠复合盐能达到市场上用作玻璃澄清剂需要的砷酸钠复合盐要求。

When carrying out comprehensive recycling studies of arsenic-antimony residue,separating alkali from antimony is a difficult technical problem.In this study,taking advantage of arsenic acid sodium and sodium carbonate in the differences of solubility,fractional crystallization method under high temperature was introduced to achieve efficient separation of arsenic acid sodium and sodium carbonate,with sodium carbonate preferential separated.The crystalized alkali was further separated by leaching with saturated sodium carbonate.Finally the pilot plant experiments were carried out.The study found that the solubility of sodium carbonate and sodium arsenate close below 40℃,and the difference in solubility with increasing temperature was gradually increased.The optimum conditions in fractional crystallization were obtained： high temperature range of 80 ∽ 90 ℃; fractionally crystallized three times; liquor was concentrated successively to a concentration of 1.36 ∽ 1.40,1.42 ∽ 1.45,1.50 ∽ 1.55,then 60 ∽ 80 percents of total alkali was separated.For the liquor after high-temperature fractionally crystallized,subcooling crystallization was conducted to get sodium arsenate.The optimum conditions for leaching crystalline alkali were： temperature 80 ℃,liquid-solid ratio 2∶ 1,leaching time 10 minutes,saturated sodium carbonate solution recycling three times.After leaching,arsenic in the alkali was stable less than 0.6%,and alkali was greater than 75%,achieving efficient separation of arsenic and alkali,which reduced the amount of arsenic in antimony smelting process.By using hightemperature fractional crystallization-leaching technology,efficient separation of arsenic and alkali could be achieved in commercial test,with arsenic in alkali lower 80% than existing technology,which could be returned to antimony smelting system.In addition,sodium arsenate generated by this method can be used for glass clarifying agent,which could reach the market standard.At the same time,for reason of the high temperature crystallization process,the heat energy could be made full use to reduce energy consumption.