Hysys Process Simulation Of Catalytic Cracking Unit

In this paper,the process simulation object is a petrochemical company's catalytic cracking unit in western China.This device consists of reaction regeneration system,fractionation system,absorption stability system and other auxiliary system,with the processing capacity of 500,000 tons / year.The catalyst is molecular sieve catalyst.First,through the software “Hysys”,the process of this device is built to simulate the actual operation.And then according to the actual operation parameters of the device and analog parameters,the discussion on the optimization issues is done.This simulation aims at some of the problems encountered in the actual operation in reality.There are the problems:(1)The output of petrol can't meet the real needs.(2)The composition of gasoline and diesel has overlap.(3)The production of liquefied petroleum gas can not meet the expected demands.(4)The molar proportion of C3,C4 in LPG is low.(5)The molar proportion of propylene in the dry gas is large.Therefore,the project is mainly aimed at the above five kinds of problems,and have adjusted the operational parameters to solve the above problems.In the simulation,these issues of parameters can be adjusted,including,the condensing temperature of condensation tank of main fractionation tower,the extraction proportion of petrol,the proportion of absorption of diesel,the heat at end of the absorption tower,the heat in the upper of the absorption tower,the temperature of the top desorption tower,the feed temperature of stable tower,the feed temperature of absorption gasoline,the reflux ratio of the stable tower,the reboiler temperature of the stable tower.Through adjusting these parameters,followings can be explored,such as how to maximize the production of petrol,how to minimize the overlap of petrol and diesel,how to maximize and minimize the liquefied gas production,how to maximize the molar proportion of C3,C4 in LPG,how to minimize the molar proportion of propylene in dry gas.Through the parameter adjustment and the final data analysis,the operational optimization program can be obtained:(1)The scheme of maximizing the production of petrol: Decreasing the reboiler temperature of stable tower.Increasing the condensing temperature at the top of the main fractionator and increasing the reflux ratio of the stable tower can also increase the yield of gasoline,but the amount of increase is relatively small.(2)The scheme for reducing the degree of overlap of petrol and diesel: Raising the condensing temperature of the condensing tank of the main fractionator.Reducing the absorption proportion of diesel oil.(3)The scheme for maximizing the yield of Liquefied gas: The condensing temperature of the condensing tank of the main fractionator is set to 48 ?.Raising the extraction proportion of petrol.Raising the temperature of the returning feed at the end of the absorption tower.Increasing the feed temperature of stable tower.(4)The scheme for minimizing the yield of Liquefied gas: Reducing the reboiler temperature of stable tower.(5)The scheme for maximizing the molar proportion of C3,C4 in LPG: Raising the condensing temperature of the condensing tank of the main fractionator.The temperature at the top of the desorption tower is set to 42 ?.Reducing the feed temperature of stable tower.Increasing the reflux ratio.Reducing the reboiler temperature of stable tower.(6)The scheme for minimizing the molar proportion of propylene in dry gas: Reducing the extraction proportion of petrol.Removing large amount of heat at the end of the absorption tower.The temperature at the top of the desorption tower is set to 49 ?.Reducing the reboiler ratio of the stable tower.In the actual operation,we can select one or more parameters of these optimization programs to adjust the unit after comprehensive measurement and consideration according the situation of industrial reality.