Process Improvement And Simulation Optimization Of Ethylene Quench System

Quench system plays the role of connecting cracking and compression unit,and its complex feed composition and operating mal-conditions directly affect the energy consumption and smooth running of ethylene plant.In quench system,gasoline fractionator is a special tower which has the function of rectification and heat transfer,separation of gasoline,diesel oil,fuel oil,and recycle use of energy.It is also the focus of capacity-expansion and revamp of ethylene plant.Dushanzi Petrochemical Company under PetroChina Co.Ltd.has raised the production load of the ethylene plant several times and increased the proportion of light feedstock,which lead to high energy consumption,process parameters unreasonable and quench oil viscosity unstable.Aimed to the above problems,using the simulation software of Aspen Hysys and the design data of the ethylene plant of the Dushanzi Petrochemical Company,and P-R(Peng-Robinson)equation as the thermodynamic equation,quench system steady state model was established based on simplified technological process.The true composition was used to present the distillates of cracking gas,to backstep the feedstock composition of quench system for simulation calculation.The feasibility of the model and the simplified process was validated through comparion of the simulation results with the design data.Fuel oil stripper is an important equipment of quench system to control quench oil viscosity and fuel oil quality.Through investigation of the cause of problem after increase of the production load of the ethylene plant,this paper will present a new energy-saving and visbreaking technique process at the premise of fuel oil stripper unchanged and optimize the operating conditions of fuel oil stripper.The influence of key technological parameters of gasoline fractionator on energy recovery,product quality and quench oil viscosity in quench system was investigated for light cracking feedstock.Simulation results showed that the new energy-saving and visbreaking technique can significantly reduce the viscosity of quench oil,and increase the energy recovery.The simulation result of the main technological parameters of gasoline fractionator can provide guidance for capacity-expansion and revamp of ethylene plant,energy conservation of quench system and optimization operation of gasoline fractionator.