Study On Process Simulation For Quench System In Ethylene Plant Based On Secondary Processing Oil

Quench system is the first step of ethylene plant, often constraining ethylene production and shortening the time of stable operation of ethylene plant. So quench system is usually the bottleneck of ethylene plant and an important part when rebuilding ethylene plant. By means of the process simulation software PRO/II, the quench system of Qilu ethylene plant is simulated in this paper.The components of pyrolysis gas have great influence on the results of simulation, they are highly complex and the local data is unreachable. In this paper, the feed composition is obtained by"backing out"method. The feed of quench system is sum of treated pyrolysis gas, gasoline, diesel and fuel oil which are also the products of quench system. And it contains petroleum fractions which are difficult to characterizing. The database of petroleum in PRO/II is based on crude oil, while the petroleum fractions in the quench system come from the cracked naphtha. So the properties of petroleum fractions in the quench system are difficult to be calculated by using the database of petroleum in PRO/II.Concerning the reasons above, two new methods for calculating the properties of petroleum fractions are proposed in this paper, which are the real components method and the mixing components method. The procedures of the real components method are as follows: First, the True Boiling Point (TBP) curve of petroleum fraction is cut. Second, the real components are selected according to the boiling point and density. The procedures of the mixing components method are as follows: First, the True Boiling Point (TBP) curve of petroleum fraction is cut. Second, the real components are selected according to the boiling point and density. Third, the composition of PNA is calculated by using Riazi correlation.As pyrolysis gas is mainly composed of light hydrocarbons and water, considerably accurate results can be obtained by using SRK and BK10 thermodynamic equations. Based on the simulation of quench system, several important parameters are studied in this paper. They are the heat exchanged ratio of quench oil, the heat exchanged of quench oil, the gasoline reflux quantity and the side draw rate of diesel. Some conclusions for directing the industrial process are acquired by these analysis.