Simulation Using Revised PSRK Thermodynamics Equation And Optimization Of Heat Exchanger Networks Of Rectisol

The Rectisol process can be operated under an environment of-62.6 to 137.9 ? and 0.23 to 3.24 MPa.Therefore,the thermodynamic equation that describes this process is strictly limited due to the wide span of temperature and pressure allowance.The H2S/CO2 Tower,specially speaking,allows a temperature to be between-16.4 and-52.4 ? and pressure to be around 3 MPa,whose process cannot be described by the default thermodynamic equation from Aspen Plus.Thus,an accurate simulation of Rectisol process is very crucial for engineering design and production guidance.In this article,Aspen Plus is utilized to simulate the Rectisol process in a real factory,which PENG-ROB,PK-ASPEN,PSRK thermodynamic equation was used in the simulation.By comparing the result of simulating the first four units of Rectisol process,PSRK equation is proved to be the one that is most similar to the factory's scenario.Then a revised PSRK equation is used to simulate the first four units of Rectisol process,and the result precisely matches the data from the factory.The relative error of key component molar flow in the key stream is as follow: relative error of CO2 in the purge gas is reduced from 64890.97% to 277.74%;relative error of CO2 in the flash steam is reduced from 14.15% to 2.92%;relative error of H2 in the flash steam is reduced from-17.20% to-3.98%;relative error of CO2 in the CO2 gas is reduced from-10.94% to 0.18%;relative error of H2 S in the H2S-rich gas is reduced from-21.00% to-2.27%.The methanol regeneration tower process is simulated with all three thermodynamic equations,and the PENG-ROB equation is proved to be the best equation that matches factory's scenario.There are many multiple loops in the Rectisol process,which make the convergence of simulation more difficultly.In the article,seven tearing streams and two convergence modules are designated and the convergence order is set.As a consequence,the Rectical process is successfully converged.The convergent process is accelerated after modifing the co-efficiency in the converge algorithm,and the convergence rate increases by 16.5 times.In the key stream,according to the simulation result,the maximum absolute error of the temperature of CO2 stripping gas is-1.49%,which could be considered as consistent with the factory data.In the purified gas,the maximum absolute error comes from the CO2 component,which is 303.23%.However,the molar ratio of CO2 in the purified gas is at ppm level,which has no effect on the purity requirement of purified gas.The article also evaluates the heat exchange network of Rectisol process from the factory.A heat transfer across the pinch and a heat load loop is observed in the heat exchange network.By increasing the heat load of the heat exchanger,the heat transfer across the pinch can be eliminated,and a heat exchanger can be saved,while saving 613.4 kW.By combining the heat exchanger,the heat load circuit can be eliminated,and the cost from purchasing and maintaining devices will be diminished with one less heat exchanger.