青岛炼化常减压装置顶循热量利用的流程模拟

青岛炼化常减压装置因受实际工艺操作条件限制,致使常顶循换热器的取热能力下降,常顶循设计取热负荷为20.18MW,而实际运行中的取热负荷只有10.8MW,约50%的热量没有得到有效利用。本文试图利用流程模拟软件来核算和论证是否可以将常顶循多余热量用作全厂轻烃的C4、C5分离,从而达到常顶循热量充分利用的目的。利用流程模拟的DSTWD模型,建立轻烃分馏塔的简捷设计模型,通过质量平衡、热平衡和相平衡原理,求出在要求的分离精度和产品质量条件下,精馏塔所需的塔板数和热负荷;利用流程模拟的Heat Exchangers模型,建立精馏塔重沸器和进料换热器的模型,核算顶循可利用的热量以及重沸器与进料加热器的取热分布。模拟结果表明:利用常顶循的剩余热量作为热源,完全可以将轻烃中的C4、C5组分进行有效分离。常顶循采取先作塔底重沸器热源、再作进料加热器热源的取热方式比较合理。计算结果同时也表明:就原油和轻烃两种介质的取热温位而言,常顶循分流成并列两股,一股作轻烃分馏塔热源,另一股继续作原油加热热源的取热方式可以使常顶循的热量利用最充分。常顶循作分馏塔热源的分支流量最佳为350t/h左右。

Process Simulation for Utilization of Top Circulating Oil Heat in Atmospheric and Vacuum Unit of SINOPEC Qingdao Refining Corporation

Due to process condition limitations,the atmospheric distillation column top circulating oil heat exchanger of Sinopec Qingdao Refining Company′s atmospheric and vacuum distillation unit suffered a declined heat recovery capacity.The designed heat recovery capacity of the heat exchanger is 10.18MW,while the actual heat recovery capacity during operation is only 10.8MW,meaning that about 50% of the heat has not been effectively utilized.With the use of process simulation software,this article tries to validate whether the residual heat from the atmospheric distillation column top circulating oil heat exchanger can be used in the separation of light hydrocarbons C4 and C5 on a plant-wide scale so as to take full use of such heat.The DSTWD model for process simulation is used in the construction of a simple model for the design of a light hydrocarbon separator.Based on the principles of mass balance,heat balance and phase equilibrium,the number of stages and heat load required by the rectifying column are calculated while the separation precision and product quality are met.With the use of a Heat Exchangers model for process simulation,models of the reboiler and feedstock exchanger of the rectifying column are established to calculate the amount of heat available from the top circulating oil heat exchanger for utilization as well as the distribution of heat for removal by the reboiler and the feedstock heater.Simulation results show that using the residual heat from the atmospheric distillation column top circulating oil heat exchanger as the heat source can effectively separate C4 and C5 components from other light hydrocarbons.The ideal heat usage process is to use the heat from the top circulating oil heat exchanger first as the heat source for the reboiler at the bottom of the column and then to use it as the heat source for the feedstock heater.The calculation results also show that for the temperature levels of the heat removed for crude oil and light hydrocarbons,the heat from the atmospheric distillation column top circulating oil heat exchanger can be divided into two parallel streams.One stream is used as the heat source for the light hydrocarbon fractionating column and the other continues to be used as the heat source for heating crude oil.This is the most efficient way of utilizing the heat from the top circulating oil heat exchanger.The optimum branch flow of the atmospheric distillation column top circulating oil heat exchanger as the heat source for the fractionating column is about 350t/h.