Research On High-efficiency Fully Welded Plate Heat Exchanger Of CO₂ Chemical Absorption System

The chemical absorption method is one of the most mature technologies for large-scale capture of flue gas carbon dioxide.At present,there are mainly problems of high system investment and large energy consumption of absorption liquid regeneration.The lean-rich liquid heat exchanger is used to recover the heat of the lean liquid at the outlet of the regeneration tower,and the regeneration energy consumption of the absorption liquid decreases with the decrease of the cold lean liquid-cold rich liquid TTD（Terminal temperature difference）of the lean rich liquid heat exchanger.The traditional stainless steel shell-and-tube heat exchanger used in the chemical absorption carbon capture process has problems such as low heat transfer coefficient and large footprint,resulting in a high economic TTD of the lean-rich liquid heat exchanger.All-welded plate-and-frame heat exchangers have high heat exchange efficiency,compact size,and higher pressure-bearing capacity than detachable plate-and-frame heat exchangers,which can solve the problems of easy leakage and large TTD.,which is convenient for equipment cleaning and maintenance.In this paper,a high-efficiency all-welded plate-and-frame heat exchanger for heat exchange of lean and rich liquids in carbon capture systems is studied.According to the test data of 30wt%monoethanolamine（MEA）/water,the CFD numerical calculation model is verified and optimized,and the higher viscosity absorption is simulated.The thermal performance of the corrugated plate fully welded plate heat exchanger used with the agent was investigated,and the parameters such as the corrugated inclination angle and corrugation height of the corrugated plate were simulated and optimized,and the optimal plate type for the poor-rich liquid heat exchanger was obtained.On this basis,the thermal performance of the capsule plate type is emphatically studied,and the design and selection of the lean-rich liquid heat exchanger for the 150,000-ton/year carbon capture project is completed according to the research results.The main research contents and results of this paper include:（1）The numerical simulation model of the plate heat exchanger was established;the geometric model was constructed according to the reduction of the plate parameters of the experimental device,and the temperature field,velocity field and pressure field of the absorbing liquid were studied through numerical simulation under the condition of 0.1-0.7 m/s flow velocity,By comparing the calculated values of different turbulence models with the experimental data,the SST k-εmodel with the smallest difference from the experimental values is selected as the numerical turbulence model;（2）Study the influence of corrugation height and corrugation inclination on the heat transfer coefficient and resistance loss;under the condition that the variation range of the pattern inclination angleβis 40-70°,the variation range of the corrugation heightδis 1.5-4.5mm,the absorption liquid temperature field,pressure field under different flow velocity conditions;the research result show that when the corrugation inclination angle is 60°,the cross flow and the Z-shaped flow achieve resonance effect and achieve the best turbulent flow state.meanwhile,as the corrugation height continues to increase,the fluid will form a vortex rebound after sliding tangentially from the top of the wave to the corrugation depression,resulting in a gradual decrease in the strength of the cross flow.The best turbulent heat transfer effect is achieved when the corrugation inclination is 60°and the corrugation height is 3.5mm.（3）Capsule-type plate heat exchangers are developed for high viscosity absorbents.Numerical simulation of single-phase flow and heat transfer in a capsule-type plate heat exchanger was carried out and the results were analyzed.It was found that the vortex formed by the shape and arrangement of the concave capsule,the vortex and the scouring of the fluid strengthened the upstream and downstream of the concave capsule.Heat transfer effect downstream of the convex capsule.（4）The 150,000 tons/year flue gas CO₂ capture system of Guoneng Jinjie Power Plant adopts a capsule-type all-welded plate heat exchanger with a design heat transfer coefficient of 1563 W/m2.K and a heat exchange area of 2000 square meters.The application results and design comparison of the final product are given to illustrate the application prospect of the heat exchanger.