维生素C酯生产废水中DMAC的回收技术

Recovery technology of DMAC in wastewater from vitamin C ester production

研究从维生素C脂肪酸酯生产废水中回收酯化反应溶剂DMAC的工艺技术,该废水中DMAC的含量约30%。在实验装置上分别模拟了精馏法和萃取法这2条回收技术路线。精馏法使用高径比为18∶1的不锈钢填料塔,内装比表面积为500 m2/m3、有效高度为1.6 m的规整填料,以1 000 g/h气相进料,确定最佳回流比为1∶1.5时,回收1 000 kg废水中DMAC的能耗为3 950 100 kJ。萃取法确定以与维生素C酯产品萃取相同的甲基异丙基酮为萃取剂,萃取比为2∶1、pH为7时,经6级逆流萃取,再经甲苯共沸脱水,回收1 000 kg废水中DMAC的能耗为916 248.4 kJ。2条技术路线都能回收可重复使用的酯化反应溶剂DMAC,回收率在96%以上,其中萃取法回收的能耗更低,回收成本小于精馏法,更具有工业化价值。

This study focuses on the technology for recovering DMAC in wastewater from production of fatty acid ester of vitamin C,which contains about 30%of DMAC.The rectification method and the extraction method are simulated on different experimental devices respectively.As for the rectification method,a stainless steel packed tower with a heightdiameter ratio of 18∶1 is employed,which is filled with structured packing with surface area of 500 m2/m3 and an effective height of 1.6 m.Wastewater boiled to gas is fed at a speed of 1 000 g·h-1 and the optimum reflux ratio determined is 1∶1.5.As for the extraction method,methylisopropylketone is chosen as the extractant to extracting DMAC,which is also used to extract fatty acid ester of vitamin C.The optimal extraction ratio is 2∶1 and the best pH value is 7.After six-stage countercurrent extraction to wastewater,extractant is distilled and trace water is removed with toluene azeotropy.The energy consumption in recovering DMAC in 1 000 kg of wastewater is 916 248.4 kJ for the extraction method and 3 950 100 kJ for the rectification method.By each method,DMAC,as a reused esterification solvent,can be recovered with a recovery rate of more than 96%.However,the extraction method consumes lower energy and exhibits a lower recovery cost than the rectification method.Therefore,the extraction method is more industrially valuable.