基于精馏分离特性的优化工艺设计

OPTIMIZATION OF PROCESS DESIGN BASED ON DISTILLATION SEPARATION CHARACTERISTICS

对于烃类混合物,挥发性越强沸点越低,沸点越高越不易挥发,因此在精馏塔(仅指普通精馏塔,不包含萃取精馏等特殊精馏塔)内,随着温度由塔顶至塔釜逐渐升高,易挥发组分富集于塔顶,难挥发组分富集于塔釜,而进料中各组分在每块塔板上的浓度,也随各组分沸点的不同按一定规律分布,即总体上低沸点组分自塔顶到塔釜浓度逐渐降低,高沸点组分自塔顶到塔釜浓度逐渐升高。这是精馏塔内物质分布的重要特性。对于有多股进料的普通精馏塔,应根据各股进料组成的轻、重,按照轻进料靠近塔顶、重进料靠近塔釜的原则设计进料板位置;反之,则能耗将增加。侧线采出可达到提浓特定组成的效果。文章所述的烯烃催化裂解装置,由于C4烷烃异构体和C4烯烃异构体的沸点有交叉,且总体上烯烃沸点较高,因此在脱丁烷塔侧线采出循环物料,可有效提高循环物料中反应有效组成物(沸点较高的烯烃)的流量。

For hydrocarbon mixture, the higher the volatility,the lower the boiling point.Therefore,as the temperature in distillation column(only common rectification tower excluding special rectification tower such as extractivedistillation tower)gradually increases from the top to the bottom,volatile components accumulate at the top and nonvolatile components accumulate in the bottom,and the concentration of feedstock components in each tray distributes by a certain rule according to different boiling points.In general,the concentration of low boiling point components gradually decreases from the top to the bottom,while the concentration of high boiling point components gradually increases from the top to the bottom.This is an important characteristic of the material distribution in distillation tower.For common distillation tower with multifeedstock,the feedstock which has more low boiling point components should enter the tower near the top.and the feedstock which has more high boiling point components should ebnter the tower near the bottom.Otherwise,the energy consumption will increase.Specific composition can be concentrated by side-draw. For the olefin catalytic cracking unit in this article,since there is an overlap in the boiling points of C4 alkane isomers and C4 alkene isomers and the boiling points of olefins are generally higher,using the side stream as circulating material can improve the flowrate of effective composition in the circulating material for the cracking reaction.