己内酰胺PAN值的影响因素及控制方法探讨

Influencial factors and control methods of caprolactam PAN value

以100 kt/a己内酰胺装置为例,分析了己内酰胺生产过程中重排滴定值偏高、己内酰胺产品高锰酸钾吸收值(PAN值)不稳定的原因,并提出改进措施。结果表明:优化己内酰胺贝克曼液相重排效果的关键在于动态管控环己酮肟和重排混合液两股混合流体的流速比,确保物料在加氢混合器混合均匀;当环己酮肟进料流量大于12 t/h时,保持重排混合液/环己酮肟流速比在2.89~3.34,当环己酮肟进料流量小于10 t/h或者环己酮肟管线压力发生变化时,调节循环泵的电流,改变重排混合液循环量的大小,控制重排混液/环己酮肟流速比在3.70以内,循环泵电流低于34 A,可确保重排滴定值稳定在1.00左右,减轻后续工序除杂的压力;加氢精制效果与加氢催化剂浓度密切相关,采用高强度和高目数过滤器滤布,可提高催化剂过滤器的拦截性能,延长滤布的更换周期,减少催化剂消耗;采取持续优化重排混合效果、强化加氢过滤作用等措施后,己内酰胺PAN值优级品率提高至99.5%。

Taking a 100 kt/a caprolactam plant as an example,the reasons for the relatively high rearrangement titration value and unstable potassium permanganate absorption value(PAN value)of caprolactam products were explored and analyzed in the caprolactam production process.And the improvement measures were put forward.The results showed that the key to optimize the effect of caprolactam Beckmann liquid-phase rearrangement was to dynamically control the flow rate ratio of cyclohexanone oxime and rearrangement mixture to ensure that the materials were evenly mixed in the hydrogenation mixer;the rearranged titration value stable at about 1.00 can be ensured so as to reduce the pressure of impurity removal in subsequent processes by keeping the flow rate ratio of rearranged mixture/cyclohexanone oxime at 2.89-3.34 when the feed flow rate of cyclohexanone oxime was higher than 12 t/h and by adjusting the current of the circulating pump,changing the circulation amount of the rearranged mixture and controlling the flow rate ratio of rearranged mixture/cyclohexanone oxime below 3.70 and the current of the circulating pump less than 34 A when the feed flow rate of cyclohexanone oxime was less than 10 t/h or the pressure of cyclohexanone oxime pipeline changed;the hydrofining effect was closely related to the concentration of hydrogenation catalyst,and the use of high-strength and high-mesh filter cloth can improve the interception performance of catalyst filter,prolong the replacement cycle of filter cloth and reduce catalyst consumption;and the high-grade rate of caprolactam PAN value was increased to 99.5%after continuously optimizing the rearrangement mixing effect and strengthening the hydrogenation filtration.