Simulation And Optimization Of CO₂ Capture Process Of Blast Furnace Gas By Alcohol Amine Method

China has become the country with the largest CO₂emission in the world,and the iron and steel industry is a resource energy and CO₂emission intensive industry.In order to achieve the goal of carbon peak by 2030 and carbon neutralization by 2060,carry out carbon capture on blast furnace gas,the main source of CO₂emissions in the iron and steel industry,will not only help green metallurgy,but also improve the calorific value of blast furnace gas.In this paper,by optimizing the process parameters of the CO₂capture system of the blast furnace gas and using the waste heat of the blast furnace,a carbon capture system with blast furnace characteristics is proposed,so as to reduce the regeneration energy consumption of the carbon capture system and promote the innovation of the CO₂capture process of the blast furnace gas.The specific research contents are as follows:Firstly,the process flow of CO₂capture of blast furnace gas is built by using Aspen Plus software,which is composed of absorption tower,desorption tower,heat exchanger and pump.And through the comparison of relevant experimental data,the accuracy of the process model is verified.On this basis,the CO₂absorption/desorption performance of three common alcohol amine absorbents（MEA,MDEA,DEA）for blast furnace gas was analyzed.The results showed that the absorption performance of each alcohol amine solution was MEA>DEA>MDEA,and the capture rate of MEA was higher than 80%under the same flux,while the capture rate of CO₂by MDEA and DEA was lower than 30%;the desorption performance is DEA>MDEA>MEA,under different heat load of reboiler,the desorption rate of DEA solution is close to 100%,that of MDEA solution is more than 75%,and that of MEA solution is less than 70%;according to the regeneration energy consumption of CO₂desorption per unit mass,the comprehensive evaluation of absorption and desorption performance shows that the performance of each amine solution is in the order of MEA>MDEA>DEA,under the same heat load of reboiler,the CO₂desorption capacity of MEA is 88.5kg/h,MDEA is 35.4kg/h and DEA is 33.6kg/h.Compared with MDEA and DEA,MEA is more suitable for CO₂capture of blast furnace gas.Secondly,the effects of operating parameters of absorption tower and desorption tower on the regeneration energy consumption,absorbent flow rate,cooling water consumption and other main performance indicators of BFG CO₂capture system were studied.The results show that the regeneration energy consumption is greatly affected by lean liquid load,rich liquid temperature,desorber operating pressure and rich liquid feed position,while lean liquid temperature and blast fuurrnnaaccee gas temperature have little effect;the abbssoorrbbeenntt fllooww rate is greatly affected by lean liquid load and lean liquid temperature;the consumption of cooling water is mainly affected by the temperature of lean liquid,the load of lean liquid,the temperature of rich liquid and the operating pressure of desorption tower,while the blast furnace gas temperature and rich liquid feeding position have little influence.Considering the influence of various parameters on the performance index of the CO₂capture system of the blast furnace gas,the optimal operating conditions of the absorber are obtained as follows:the inlet lean liquid load of the absorber is 0.3mol CO₂/mol MEA,the lean liquid temperature is 40℃,and the blast furnace gas temperature is 50℃;the optimal operating conditions of the desorber are as follows:the inlet rich liquid temperature of the desorber is 115℃,the operating pressure of the desorber is 2.2atm,and the second stage equivalent plate feed of the rich liquid feed position of the desorber.Then,based on the investigation of waste heat resources of blast furnace slag flushing water in a steel plant,a carbon capture system of heat pump technology based on waste heat utilization of blast furnace slag flushing water is proposed.The condenser of the heat pump system is used to provide the required heat energy for the desorption process of the CO₂capture system of the blast furnace gas.Under the parameters of the heat pump evaporation temperature Tc=45℃and the condensation temperature Te=130℃,the system energy consumption is reduced by 77.4%compared with the traditional carbon capture process,which significantly reduces the regeneration energy consumption of the carbon capture system.Finally,using response surface method and GA-BP neural network method to influence the main process parameters of blast furnace gas CO₂capture system:lean liquid temperature,lean liquid load,poor liquid heat exchange,temperature difference,operation pressure of desorption tower,process parameters optimization.According to the analysis of response surface method,there is a certain interaction between the process parameters.The interaction of lean liquid load and heat transfer temperature difference between rich and poor liquid,heat transfer temperature difference between rich and poor liquid and operating pressure of desorption tower has a significant impact on the regeneration energy consumption.The combination of process parameters with the lowest regeneration energy consumption of carbon capture system is lean liquid temperature 40℃,lean liquid load 0.27mol CO₂/mol MEA,rich and poor liquid heat exchange temperature difference 5℃,desorption tower operating pressure 2.1atm,and regeneration energy consumption 3.12GJ/tCO₂.