CO_(2)化学吸收系统的垂直管式降膜再沸器传热传质研究

Study on Heat and Mass Transfer of Vertical Tube Falling Film Reboiler in CO_(2) Chemical Absorption System

针对CO_(2)化学吸收系统中存在的高再生耗能和吸收剂长时间高温受热产生热降解的问题,提出了一种新型管式降膜再沸器。通过对降膜流动特性分析,开展了液体分布器结构优化设计研究,并且在200m^(3)/h烟气CO_(2)化学吸收中试平台进行了系统热工实验,以验证降膜再沸器的传热传质性能并寻找最优操作参数。通过降膜流动实验发现,优化接管开孔和分布槽孔径后的液体分布器不均匀度可显著降低至0.026。结果表明,随着管内液相流速的增加及层流与湍流状态的转变,降膜再沸器总传热系数呈先减小后增大的趋势。同时,随着蒸汽质量流量由60kg/h增加至70kg/h和80kg/h,再生率可由10%左右上升至20%左右,最高可达到24.7%,从而促进了胺溶液的二次解吸。增加蒸汽流量和胺溶液进口温度,降膜再沸器热流量逐渐增大,整体传热性能逐渐增强,总传热系数随之增加。所开发的CO_(2)化学吸收管式降膜再沸器,实现了降低吸收剂在再沸器内停留时间,同时提升了再沸器传热效率及胺溶液CO_(2)再生率,有望显著降低碳捕集再生热耗。

To solve the problems of the high regenerationenergy consumption and the thermal degradation caused by prolonged high-temperature heating of absorber in CO_(2) chemical absorption system,a new type of tubular falling film reboiler was proposed.By analyzing the flow characteristics of falling film,a research was conducted on structural optimization design of liquid distributors.To verify the heat and mass transfer performance of the falling film reboiler and find the optimal operating parameters,a systematic thermal experiment was conducted on a 200 m^(3)/h flue gas CO_(2) chemical absorption pilot platform.The experiment results of falling film flow reveal that the unevenness of the liquid distributor can be significantly reduced to 0.026 after optimizing the direct opening of the connecting tube and the aperture of the distribution slot.Results show that,with the increase of liquid phase flow velocity within the tubes and the transition between laminar and turbulent flow states,the overall heat transfer coefficient of the falling film reboiler initially decreases and then increases.Concurrently,as the mass flow rate of steam increasing from 60 kg/h to 70 kg/h and 80 kg/h,the regeneration rate can be increased from approximately 10%to approximately 20%,and with a peak of up to 24.7%,thereby promoting the secondary desorption of the amine solution.By increasing the steam flow rate and the inlet temperature of the amine solution,the heat flux of the falling film reboiler gradually increases,resulting in a gradual enhancement of the overall heat transfer performance and a subsequent increase in the overall heat transfer coefficient.The CO_(2) chemical absorption tube-type falling film reboiler developed in this study has achieved a reduction in the residence time of the absorbent within the reboiler,while simultaneously can improve the heat transfer efficiency of the reboiler and the CO_(2) regeneration rate of the amine solution.This is expected to significantly reduce the heat consumption for carbon capture.