Improvement And Optimization Of Acid Gas Removal Process With Coupled Self-Heat Recovery

The integrated coal gasification combined cycle can achieve clean utilization of coal and near-zero emissions.The acid gas removal process can remove most of the H2S and a small amount of CO2 from the syngas,which is an important part of the syngas purification.The large heat consumption of the reboiler in the chemical absorption method based on MDEA solution has kept the cost of syngas desulfurization at a high level,and how to reduce the heat consumption of this process has been a hot topic of research.The self-heat recovery technology has been widely used in various distillation processes,and all of them have achieved good energy-saving effect.Therefore,this paper investigates the energy saving potential of self-heat recovery technology for acid gas removal process from two aspects:process improvement and parameter optimization,and the main research progress and results of this paper are as follows:In terms of process improvement,firstly,this paper uses the Hysys software platform to build the models of acid gas removal,combustion turbine and waste heat boiler,and proposes two retrofit processes of self-heat recovery technology,Case1 can recover 50.56%of the heat of the desorption tower distillate,the heat pump COP is 5.81 higher than the electric penalty coefficient of 4.70 for lowpressure pumping,and the operating cost decreases from 0.0703 $/kgH2S to 0.0665$/kgH2S,with an annual operating cost saving of 181,315 $;Case2 can recover 93.08%of the heat of the distillate,but the heat pump COP is only 3.16,and the cold gain generated by the process is not enough to compensate for the loss of additional electricity consumption,and the operating cost increases to 0.0747$/kgH2S.After the self-heat recovery transformation,only the distillate cooling process showed a positive gain in the exergy loss,the Case1 process greatly reduced the average heat transfer temperature difference of the distillate cooling process,which reduced the exergy loss of the whole unit from 8015.55 kW to 7788.89 kW,a decrease of 6.77%;Case2 distillate cooling process there is a large amount of gas throttling process makes the process of the reduction of the gas loss is not obvious,the whole unit of the exergy loss increased to 8444.84 kW.In summary,the process modification in the form of Case1 has achieved better energy saving potential.In terms of subsequent parameter optimization of Case1,firstly,we analyzed the effects of two parameters,namely,suction tower pressure and heat pump heat exchanger inlet pressure,on the energy consumption and exergy loss of each component of Case1,and summarized the influence law of the two parameters on the self-heat recovery capacity.Subsequently,the objective functions with the optimization objectives of operating cost and exergy loss were established respectively,and the genetic algorithm in Matlab was implemented to call the key parameters of Hysys through the interface file,and the two operating parameters were optimized.Finally,the corresponding parameter variables in the optimal case of the two objective functions are derived.When the desorption tower pressure and heat pump heat exchanger inlet pressure are 165 kPa and 30 kPa,respectively,the operating cost is optimal at 0.0655 $/kgH2S,which is 1.54%lower than Case1 of the initial parameter,and when the two parameters are 174 kPa and 32 kPa,respectively,the exergy loss is optimal at 7398.59 MW,a decrease of 6.77%compared with Case1 of the initial parameters,achieving further optimization of the transformation process from the level of operating parameters.