Research On Effect Of Ceramic Membrane Heat Exchanger On Water And Heat Recovery In Chemical Absorption Technology

The large amount of CO₂ emission has caused global warming.Controlling and reducing CO₂ emission have attracted much attention.The CO₂ chemical absorption technology for large-scale CO₂ emission sources such as coal-fired power plants has important strategic significance for China.But the high energy consumption makes it a bottleneck in large-scale commercial applications.The optimization of processes in chemical absorption carbon capture system is an important part of improving the comprehensive performance of chemical absorption.This subject is based on an innovative ceramic membrane heat exchanger,which optimizes and improves the rich-split regeneration process to reduce the energy consumption.Aiming at the influence of operating parameters on water and heat recovery of membrane heat exchangers,this paper studied different working conditions including regeneration gas flow rate,regeneration gas temperature,water vapor molar fraction in regeneration gas,rich-CO₂ solvent flow rate,rich-CO₂ solvent temperature,and rich-CO₂ solvent concentration.We found that the heat recovery flux is more sensitive to the rich-CO₂ solvent flow rate,the regeneration gas temperature,and the water vapor molar fraction in regeneration gas.Especially when the water vapor molar fraction in regeneration gas is increased from 0.5 to 1.5,the heat recovery flux can increase by 188.9%.And the effect of rich-CO₂ solvent concentration is almost negligible.With the change of working conditions,the increase rate of water recovery rate is limited,but the recovery effect is considerable remaining at 78%-91%.Aiming at the influence of ceramic membrane specifications on water and heat recovery of membrane heat exchangers,tubular ceramic membranes with lengths of200mm and 300mm and pore diameters of 10nm and 20nm are selected to form four different types of ceramic membrane heat exchanger components.It was found that the effect of changing length is greater than the change of pore size,and pore size is not directly related to heat recovery performance.The membrane heat exchanger with a pore size of 10 nm and a length of 300 mm has the best heat recovery effect.The consumption reduction potential can reach 7.25%,which is better than directly using the rich-split regeneration process.And the membrane heat exchanger with a pore size of 20 nm and a length of 300 mm has the maximum water recovery rate which can reach 91%,showing that the ceramic membrane heat exchanger has great potential in recovering water vapor in regeneration gas.Aiming at the heat and mass transfer mechanism of the membrane heat exchanger,this paper explains the capillary condensation process in the ceramic membrane separation layer,which dominates the entire mass transfer process.The occurrence of water vapor condensate blocks the transmembrane transmission of MEA and CO₂,and realizes the recovery of both the sensible and latent heat of regeneration gas.The main form of heat recovery is the heat conduction process with the ceramic membrane.The selection of a ceramic film with a large effective thermal conductivity can greatly improve the heat recovery effect.We tried to establish a theoretical empirical model of heat recovery flux,and the overall heat transfer coefficient is used to evaluate the heat recovery effect,which has good adaptability to different ceramic membrane specifications,providing a basis for industrial applications.