Study On Rectisol Process Simulation And Thermodynamic Optimization

Rectisol is an effective gas refining process, and in the rectisol process cold methanol is used as the solvent to remove the acid gases, such as H2S, CO2. The rectisol process high purification degree and good selectivity may be gained in low temperature and high-pressured conditions. And these acid gases are released from the methanol solution through steam stripping means and the next process may be started. This process is a very important link in the coal chemical processing industry.The development on the synthetic ammonia, methanol chemical industries are very fast in our country and their device scales are unceasingly increasing for the time being. The raw gas purification technology with high efficiency and low consumption is deemed to be particularly important. Rectisol is such kind of very fine purification technology. However, the relevant units in our country have not fully grasped the technique. The ASPEN PLUS was used to simulate rectisol process in this study. The relevant parts were improved according to the exergy analysis method. The following problems were solved and the corresponding results were obtained in this study.1). The engineering significance of the rectisol was elaborated. The domestic and foreign present situations, the process principle, the processes, duties and characteristics of the rectisol were introduced, and the exergy analysis method was described simply.2). The simulation tool in this study, Aspen Plus, was introduced briefly; and then the RadFrac model used in the simulation process and the application of the flow simulation software were described for the following simulation work. Moreover, the theoretical bases to study rectisol process were introduced. The development of simulation technique and MESH equation were presented. The heat and mass transfer theory in rectisol process were stated.3). Based on the comparison of simulation results, the thermodynamics models were chosen in view of characteristics of the process module. NRTL model was used to the finishing absorption column. SR-POLAR model was used to the major absorption column. SR-POLAR model was used to the primitive absorption column. SR-POLAR model was used to the desulphurization column. SR-POLAR model was used to the CO2 regeneration column. Wilson and NRTL models were used to the H2S concentrating column. NRTL model was used to the methanol regeneration column. NRTL model was used to methanol/water separation column. As for the flash vaporization vessel, the flow splitter and the heater, their models were selected according to the approximation principle. And the whole process calculation results were very ideal. The calculation results may be provided for raising relevant planes and selecting more suitable thermodynamic models in the future and reducing the workload in the relevant studies.4). The energy utilization analysis to the rectisol processes in the five columns was carried out based on the simulation calculation about the rectisol and by utilizing the exergy analysis method, so as to obtain the energy utilization weak links in the technological processes; moreover, the optimizations have been implemented to the above weak links; namely, the preheating measure shall be taken to the related flowing streams in the methanol regeneration column and the methanol/water separation column so that the various resources in the internal system may be used adequately and reasonably and the energy input into the system may be reduced greatly. Therefore, the total energy loss may be reduced correspondingly and the more economic effectiveness may be achieved.