Experimental Study Of CO₂ Absorption By Novel Biphasic Solvents

Carbon Capture and Sequestration（CCS）is an important method for mitigating global warming,which has attracted extensive attention from the international community in recent years.The absorption by alcohol amine solvents is the most widely used in the industry,but the high regeneration energy consumption is economically unaffordable.Therefore,the research and development of CO₂ capture technology with low cost and energy has become the focus of attention.In the process of CO₂ absorption by biphasic solvents,absorbent and absorption products are separated.Only the absorption products are sent to the desorber for regeneration,and the absorbent can be directly reused.This operation can greatly reduce the energy loss in the regeneration process.Therefore,biphasic solvents can be used as ideal substitutes for alcohol amine solvents.In this study,TETA,1-MI and water were mixed to prepare a novel biphasic solvent TETA-1-MI.Using the wet wall column（WWC）as a reaction device to explore the CO₂ absorption kinetics,investigate the phase separation performance,obtain the total mass transfer resistance（1/K_G）,liquid phase mass transfer resistance（1/k_l）,gas phase mass transfer resistance（1/k_g）and other parameters under various working conditions,and clarify the speed control steps of CO₂ absorption by biphasic solvent.The kinetic results showed that the 1/k_g was dominant under low CO₂ loading.With the increase of CO₂ loading,the 1/k_l began to play a dominant role,and its ratio increased from 25.4%to 83.1%.This phenomenon indicated that the absorption rate was mainly related to 1/k_l.The absorption product TETA-carbamate limited the solubility of 1-MI,resulting in the phase separation.The material distribution was analyzed by nuclear magnetic resonance（NMR）.The results showed that the upper layer was CO₂-lean phase,containing 1-MI and water.The lower layer was CO₂-rich phase,mainly composed of TETA and TETA-carbamate.For thermodynamics,compared with MEA,TETA-DEAPD,TETA-DMCA,TETA-DEEA,the regeneration energy consumption of TETA-1-MI was reduced by about 40.0%,16.3%,24.2%and 8.1%,respectively,which was only 2.26 GJ/t CO₂.It was equivalent to the heat consumption of the second-generation absorption solvents CANSOLV（2.33 GJ/t CO₂）and KS-1（2.44 GJ/t CO₂）reported internationally.The above results indicated that TETA-1-MI developed in this study can be used as an ideal candidate for CO₂ capture technology with the absorption performance of high loading,fast absorption rate,low viscosity and low energy consumption,which has a great development prospect.