Research Of Deep Cut Technology And Optimization Of Heat Exchanger Network For 10 Million Ton/Year Distillation Unit Of Dushanzi Petrochemical Company

Since 2009,the PetroChina Dushanzi Petrochemical Company has adopted the Shell's patented technology for the vacuum system of its 10-million-ton distillation unit,with the outlet temperature of vacuum furnace being designed as 436?.However the specification for outlet temperature has never been achieved,the main reason is that there is no subsequent vacuum waxy oil hydrogenation device and the oil property changed.Deep vacuum distillation is an urgent issue for PetroChina Dushanzi Petrochemical Company.However,the energy consumption of the distillation unit will increase due to deep vacuum distillation,so it is necessary to optimize the heat exchange network to save energy.This paper mainly studies deep vacuum distillation operation of the vacuum tower and the optimization of the heat exchange network for the 10 million-tons per year distillation unit of the PetroChina Dushanzi Petrochemical Company.Through simulation,we can find that when the outlet temperature of vacuum furnace increases,the amount of cut oil of the first,the second and the third side line product of vacuum distillation tower all increases,and the increase extent of them are different,whereas the amount of cut oil product of the fourth side line of vacuum tower decreases.When the pressure on the top of the vacuum distillation tower increases,the amount of cut oil product of the first side line decreases,whereas the amount of cut oil product of the second and the third line both increases,and the increase amplitude the third line product is greater than that of the second line product.The amount of product which is withdrawn from the vacuum tower for circulation to the vacuum furnace decreases,but the vacuum residuum increases significantly.For optimization of heat exchange network,five optimization schemes were proposed,which can be divided into three strategies:(1)to adopt the high flowrate and small temperature difference strategy with circulation at the middle section of vacuum distillation tower;(2)to adjust the proportion of each side line product;(3)to adjust the position of the heat exchangers.After implementation of optimization,the final temperature of the initial distillation tower bottom oil before entering the atmospheric furnace were increased by nearly 2? after heat exchange.In combination with the actual production operation data,the vacuum deep distillation and optimization of heat exchange network by using process simulation software can improve the overall economic benefit of the Dushanzi oil refinery and the PetroChina Dushanzi Petrochemical Company.