Process Simulation Of Ionic Liquids Used In CO₂ Capture Technology Research

In all of the coal-fired power plant flue gas CO₂ capture technologies, alconol-amine method is currently one of the most widely used and most mature technologies in industry. But for alconol-amine method, there are some shortcomings, such as high regeneration energy consumption, great solvent loss and heavy equipment corrosion. Ionic liquid is a new type of green solvents with small volatile, low heat capacity, good thermal stability and other advantages, which has great potential in the CO₂ capture process. For the 90% CO₂ removal task of a 600MW coal-fired power plant flue gas, this paper first set up a new CO₂ capture process for ionic liquids [bmim][BF4] and [bmim][PF6].After that, the process was simulated by the software Aspen Plus. In addition, the MEA aqueous solution and [bmim][BF4]+MEA aqueous solution were used in the simulation of CO₂ capture process. For these four kinds of absorbent capture systems, this paper separately analysed the influence of some main working parameters and got the best working parameters.Under the optimized working conditions, simulation results show that there will be a heat consumption of 3.74GJ/t CO₂ and electricity consumption of 0.0527GJ/t CO₂, when MEA solution is used. Meanwhile, the MEA and H2O loss will be 0.220kg/t CO₂ and 189.3kg/t CO₂. As for ionic liquid absorbent [bmim][BF4], there will be a electricity consumption of 2.63GJ/t CO₂ and solvent loss of 0.299g/t CO₂. When [bmim][PF6] is used to absorb CO₂, the system electricity consumption and solvent loss will be 2.70GJ/t CO₂ and 0.391g/t CO₂. When [bmim][BF4]+MEA aqueous solution is used to capture CO₂, it will be a heat energy consumption of 3.11GJ/t CO₂, electricity consumption of 0.0531GJ/t CO₂. In this capture process, it will loss 1.47kg MEA/t CO₂,59.6kg H2O/t CO₂ and 0.282g [bmim][BF4]/t CO₂.Finally, the total capture cost composed of solvent loss and energy consumption was calculated. It was found that using alcohol amine method takes cost of 163.31 yuan for per tonne CO₂ capture. Compared to alcohol amine method, IL+MEA method could save 15.4% of capture cost. The capture cost of ionic liquid method was over 3.8 times as much as that of the alcohol amine method.Compared to MEA method, ionic liquid method has some advantages, solvent loss for example, but its power consumption is much higher than that of MEA, and so is the total capture cost. Although IL+MEA has no advantages on solvent loss, IL+MEA can reduce lots of power consumption, and the total capture cost is lower than MEA. On the whole, for the specified gas capture task of this paper, the IL+MEA method is superior to the MEA method, which is superior to the ionic liquid method.