| Carbon capture from flue gas after fossil fuel combustion is considered as one of the effective near-term technologies for reducing CO2 emissions,and chemical absorption using aqueous amine solutions is the most promising one in the industry.Due to high boiling point,low heat capacity and volatility,nonaqueous solutions can make up for the disadvantages of large solvent loss,high energy consumption and easy equipment corrosion of aqueous solutions.Since polar products are generated after CO2 absoipted by amine,microwave heating is considered as a potential and novel regeneration technique due to its selective heating.However,basic research in this area is currently lacking.To explore the feasibility of CO2 nonaqueous absorbent in microwave heating regeneration,CO2 absorption and microwave regeneration experiments of different triethylenetetramine(TETA)nonaqueous absorbents were conducted to evaluate the performance including absorption capacity,regeneration rate,desorption capacity,CO2 recovery and energy consumption of absorbents,and then ones suitable for microwave regeneration were selected.After that,the mechanism of microwave regeneration and effects of different conditions on regeneration performance were studied.The regeneration performances of microwave and conduction heating,TETA nonaqueous absorbents and monoethanolamine(MEA)aqueous solution were compared respectively to provide necessary experimental data and theoretical basisFrom the CO2 absorption experiments,phase change phenomena will appear after absorption in some solutions like TETA/Ethanol.The solvent law of phase change is that its polarity should be lower than water and the number of hydroxyl in the molecule is less than two,or the number is more than one but its polarity should be not higher than polyethylene glycol(PEG200).The presence of hydroxyl in the solvent promotes the CO2 absorption capacity of solution,and the TETA/PEG200 solution has the highest capacity of 1.80 mol/mol TETA among the fourteen TETA nonaqueous solutions.According to volatility and absorption capacity,nine TETA nonaqueous solutions of organic solvents such as PEG200 and 1,4-butanediol(BDO)were chosen and studied for microwave regeneration.From the microwave regeneration experiments,solvents and absorbents owning higher dielectric constant,smaller viscosity and heat capacity showed faster heating rates under microwave,while the effect of density was small.TETA/BDO and TETA/PEG200 absorbents exhibited excellent regeneration and stable cyclic performance through microwave single and cyclic regeneration experiments,with desorption capacities of 1.49 and 1.65 mol/mol TETA,and CO2 recovery of 86.18%and 91.39%after eight absorption/desoiption cycles.Besides,the proper regeneration temperatures for them are 110℃ and 120℃,respectively.And the effect of microwave irradiation on the absorbent regeneration was "thermal effect".The energy consumption(EC)of absorbents has a strong linear correlation with the dielectric constant(ε’)of the solvents within a certain solvent viscosity range(1.4-88.8 mPa s,20℃),and the equation of fitting line is EC=81.556+0.926ε’.Within a certain range,changes in microwave power(160-800 W),amine concentration(0.3-2.2 mol/L),and solution volume(100-500 mL)affected the CO2 recovery and energy consumption.When microwave power increased from 160 to 800 W,amine concentration increased from 0.3 to 1.5 mol/L and solution volume increased from 100 to 500 mL,the energy consumption reduced by 39%,75%and 23%respectively.Compared with conductive heating,the microwave heating of nonaqueous absorbent had advantages in regeneration rate,desorption capacity,CO2 recovery,energy consumption and regeneration temperature,and was more suitable for phase change absorbent,while MEA aqueous solution performed better under conductive heating.Under optimal conditions,compared with the 30 wt%MEA aqueous solution regenerated by conductive heating,the CO2 recovery with microwave regeneration for 30 wt%TETA/BDO and TETA/PEG200 absorbents increased by 2.6 and 2.7 times,while energy consumption decreased by 69%and 76%,respectively. |
PDF Full Text Request