Chemical Absorption Method Study For CO₂Capture From Coal-fired Flue Gas

The disasters caused by the extreme weather turn to be more frequent due to the greenhouse effect, while CO2is the largest contributer to the greenhouse effect. To reduce the CO2emission by human is an effective mean for tackling with the climate change. The reduction of CO2emission by large-scale stationary emitter is considered to be the most feasible and effective solution. Chemical absorption method is one of the most mature and most likely commercial technologies for CO2capture in coal-fired power plants. However, high energy consumption and huge water withdrawal still hinder the application of chemical absorption method. In this paper, research has already been carried out into development of novel absorbents and process modification. The potential of improving absorption performance, cutting down the energy consumption and water withdrawal has been discussed.The semi-batch experiments have already been carried out to mixed amine solvents and aqueous ammonia in order to develop novel solvents. The experiment results show that,(1)20%MEA+10%DETA and25%MEA+5%PZ are two of best solvents for all the MEA based mixture solution, while15%MDEA+15%DETA is the best MDEA based mixed amine solvents. The former two solvents can increase the absorption score to54%～76%compared to30%MEA solution, meanwhile the regeneration performance of the two mixed amine solvents are almost apromiate to that of30%MEA solution.15%MDEA+15%DETA can reduce the energy consumption to25%compared to typical30%MEA solution.(2)12%is the most suitable mass concentration for aqueous ammonia solution during all the tested mass concentrations.15℃and35℃are two critical operation temperature values under which the CO2absorption of ammonia solution reaches the best mode.90℃is the best regeneration temperature during all the tested temperature values.0.4mol CO2mol NH3is the recommended CO2loading for cyclic lean ammonia solution. According to the study results on ammonia slippery and the control of ammonia slippery, the ammonia slippery increases with the temperature increase and intial ammonia mass concentration. AEPD and AMP of weight concentration1%added into13%aqueous ammonia solution can decreases the ammonia slippery during the30minutes to about33%. In addition, the screening parameters and evaluation method have been discussed in this paper. Enhancement factor and correlation factor have been introduced to analyze the appropriate blending ratio of mixed amine solutions.Water balance of CO2capture process is another focus of this paper. A review of process flow sheet modifications for energy efficient CO2capture from flue gases using chemical absorption has been given out. Suprisingly, most of the process modifications focus on saving energy for CO2capture, while seldom people pay enough attention to water issue caused by chemical absorption method. In fact, the water withdrawal is a rather huge rock for the application of chemical absorption.Based on this background, detail analysis of water withdraw and water consumption for the power plants and the CCS process have been presented in this paper. Some potential measures are also afforded. At last, an estimation of water consumption for300MW coal-fired power plants retrofitted with CCS has been given.The experimental study on the development of novel solvents and the theortical analysis on the process modification supply a large number of helpful parameters and method for cyclic experimental study. Based on the research background, a200Nm3/h test rig for CO2capture from coal-fired flue gas have been designed and built. The design CO2removal efficiency of this facility is90%. The aim of building such a test rig is to test different absorbents, to test hydraulic performance of pakced columns so as to achieveing the modification of absorbers.