Process Simulation And Analysis Of Sour Water Stripping Based On Side Line Heat Pump Distillation

Sour water stripping is a key technic of wastewater treatment in petrochemical industry,which contains H₂S,NH₃,H₂O and little hydrocarbon.However,the traditional sour water stripping exists problems such as ammonium salt crystallization,impure water,high energy consumption,and lack of economic analysis and process control.Based on the traditional process,the side line heat pump distillation was developed,and the analyses of energy consumption,economy and process control were carried out.The main contents are as follows:First,the ELECNRTL model was used to simulate the typical sour water stripping process,and the simulated values were consistent with actual values.Based on the model,bottleneck analysis was carried out on problems of ammonium salt crystallization and impure water in the process.After parameter optimization and process improvement,the mass fraction of NH₃ and H₂O in acid gas decreased to 0.42%and 1.4%respectively,and the mass fraction of NH₃ in side gas reached to 32.36%.The concentrations of H₂S and NH₃ in purified water reduced to 5.78mg/L and 99.79 mg/L respectively,which would solve the problems of ammonium salt crystallization and impure water.Second,the side line heat pump distillation was developed to reduce energy consumption.Aiming at minimum annual total cost,considering the heat exchange driving force of 15 ^oC,the optimized compression ratio was 1.5,and the steam outlet temperature was 130 ^oC.The results showed that the thermodynamic efficiency of the heat pump process was increased by 46.51%,and the annual total cost was reduced by 22.74%comparing without heat pump distillation.After three stage condensation and optimization of the crude ammonia,the ammonia content in refined ammonia was 97.65%.Third,the dynamic model of the heat pump process was established,two control structures were adopted respectively,and the controller parameters were adjusted.Adding Q_R/F feedforward control based on S/R cascade control structure,the results showed that the improved control structure would reduce the deviation of H₂S concentration in purified water,the overshoot of H₂O content in acid gas and the setting time of sensitive plate temperature,which made heat pump have stronger anti-interference ability.This paper could provide reference for the thermal integration and process control of the sour water stripping.