氨法脱硫中杂质对硫酸铵结晶的影响

Effects of Impurities on Ammonium Sulfate Crystallization inAmmonia Desulfurization

选取某电厂氨法脱硫工艺母液罐中结晶结果不相同的硫酸铵母液为研究对象,对其进行减压蒸发结晶和抽滤得到晶体、固相杂质和液相杂质,并结合矿相分析、表面微观形貌和元素分布分析及离子分析等表征手段,深入剖析了影响某电厂氨法脱硫工艺中硫酸铵结晶的原因。结果表明:在由原料氨水或烟气中携带飞灰所含铝铁矿物引入溶液体系的液相杂质中,以Al^3+和Fe^3+对硫酸铵结晶的影响最大,随着杂质离子的质量浓度增大,硫酸铵的晶型由规则棱柱状向梭状或者片状转变,甚至使硫酸铵无法结晶;在含钙飞灰的固相杂质中,钙的影响最为明显,由炉内电石渣脱硫后形成的未反应氢氧化钙或氧化钙与原料氨水中的铵根存在对硫酸根的竞争作用,其竞争关系的强弱或占比会直接影响硫酸铵结晶的晶型质量,甚至会导致硫酸铵无法结晶。

The ammonium sulfate mother liquor with different crystallization yields in the mother liquor produced by conducting the ammonia desulphurization in a power plant was prepared and investigated.Then,the crystal,solid phase impurity and liquid phase impurity were obtained through the vacuum evaporation crystallization and the filtration of the ammonium sulfate mother liquor.On this basis,combined with the mineral phase analysis,surface micromorphology,element distribution analysis and ion analysis,the driving mechanisms for the crystallization of the ammonium sulfate during the ammonia desulphurization process were analyzed.The results show that the Al 3+and Fe 3+have the largest influence on the crystallization of the ammonium sulfate.With the increasing impurity with respect to the ion mass concentration of the impurity,the crystal form of the ammonium sulfate will change from regular prismatic to fusiform or flake until the ammonium sulfate can not be crystallized.Among the solid impurities in the fly ash containing calcium,the effect of the calcium is most obvious.The unreacted calcium hydroxide or calcium oxide formed by the desulphurization of the calcium carbide slag in the furnace can compete with the ammonium root in the raw ammonia water,and the relatively competitiveness will affect the crystal quality of the ammonium sulfate crystallization,and even lead to the non-crystallization of the ammonium sulfate.