腈纶生产中硫酸钠结晶工艺的调控

Control of sodium sulfate crystallization process during polyacrylonitrile fiber production

根据结晶原理及工业结晶的控制要求,分析了硫氰酸钠(NaSCN)二步法腈纶生产中硫酸钠(Na_2SO_4)结晶工序的失控原因,并提出了调控措施。结果表明:生产中结晶工序沉降槽底部晶浆过量去除破坏了Na_2SO_4的结晶平衡,导致Na_2SO_4不能有效去除;添加固体无水Na_2SO_4,培养晶种,保持沉降槽底部Na_2SO_4质量分数为10%～20%,可维持Na_2SO_4的结晶平衡。

The factors causing the failure of sodium sulfate（Na2SO4） crystallization process were analyzed during two-step polyacrylonitrile fiber production from sodium thiocyanate（NaSCN） according to the crystallization principle and the industrial crystallization control requirement.And the control approaches were proposed.The results showed that the excessive removal of crystal slurry at the bottom of the settling tank during the crystallization process damaged the crystallization equilibrium,causing the failure of Na2SO4 removal.The crystallization equilibrium of Na2SO4 can be maintained by adding solid anhydrous sodium sulfate, culturing crystal seeds,keeping 10%-20%Na2SO4 by mass fraction at the bottom of settling tank.