糠醛精制装置工艺优化降低抽出油溶剂含量

Optimization of furfural refining unit process to reduce solvent content in extract oil

糠醛精制装置受糠醛结焦温度所限,抽出油回收系统经三效蒸发后,汽提塔底温度难以进一步提高。在加工高芳烃原料时,因溶剂对芳烃溶解性好,产品抽出油溶剂含量高。采用抽出液二次加热的方法可以提高抽出油汽提塔底温度,对降低抽出油溶剂含量效果较好。通过模拟计算得出安装抽出液二次加热器的最优位置,推荐设置在三效蒸发塔与闪蒸塔之间,相比无二次加热可以降低抽出油溶剂含量约83.1%。计算得出汽提塔最优汽提蒸汽用量为塔底抽出油量的5%,汽提塔顶温度和汽提塔底抽出油溶剂含量近似成反比关系,但汽提塔顶温度的提高需要注意塔顶气中携带油的影响。小负荷运行或者设计加工量较小的装置,通过设置抽出油循环流程,可提高汽提塔底温度,有利于降低汽提塔底溶剂含量。通过设置抽出油二次加热、抽出油循环流程,优化汽提塔操作压力、塔顶温度、汽提蒸汽量等,实际运行可以将抽出油溶剂质量分数控制在小于150μg/g,降低了装置溶剂消耗。

Due to the limitation by the coking temperature of furfural,the bottom temperature of the stripping tower of the furfural refining unit is difficult to further increase after the extract oil recovery system undergoes three-effect evaporation.When processing high aromatic hydrocarbon feedstocks,due to the high content of aromatics and good solubility of solvents and aromatics,the extract oil of the product has a high solvent content.The method of secondary heating the extract liquid can increase the bottom temperature of the extract oil stripping tower,and has a good effect on reducing the solvent content of the extract oil.Through simulation calculation,it was found that the optimal location for the extract liquid secondary heater is between the three-effect evaporation tower and the flash tower,which can reduce the solvent content of the extract oil by 83.1%compared to no secondary heating.The optimal amount of steam used in the stripping tower is 5%of the oil extract from the bottom of the tower.The temperature at the top of the stripping tower is approximately inversely proportional to the solvent content of the extract oil at the bottom of the stripping tower,and the attention should be paid to the influence of oil carried in the overhead gas.For units with low load operation or designed processing capacity,setting up an extract oil circulation process can increase the bottom temperature of the stripper,which is beneficial for reducing the solvent content at the bottom of the stripper.By setting the secondary heating and circulation process of the extract oil,optimizing the operating pressure,top temperature,and steam volume of the stripping tower,the solvent content of the extract oil can be controlled to be less than 150μg/g,reducing the solvent consumption of the unit.