Research On The CO₂ Compound Absorber Of High Desorption Rate

Human being should lower greenhouse emissions in case of global warming. It is fundmental to develop carbon capture technologies for fossil fuel-based power plant, which contribute half of CO2 emmission in the world. To overcome the difficult of flue gas, which have properties of large quantity, high impurity and low CO2 partial pressure, alkylamine scrubing technology has been widely used for post-combustion CO2 capture process in fossil fuel-based power plant. However, high energy consumption limits the application of alkylamine scrubing technology and effective CO2 absorbent needs to be developed.Traditional alkylamine CO2 absorber remains contradiction in absorption and desorption:the primary and secondary alkylamine perform well in absorption but insufficiently in desorption; the tertiary alkylamine gets batter in energy consumption yet shortages in absorption rate. Compounded alkylamine CO2 absorbents have been developed to overcome the defect of traditional alkylamine:One kind is based on the primary or second amine, adding tertiary amines to lower the desorption energy consumption; anothrer takes tertiary amines as main body, compounding primary amine to improve absorption rate. However, according to the results of the present study, compounded amine absorbent still can not simultaneously improve absorption and desorptioin performance. Therefore, the objective of new-type CO2 absorbent should have the properties of "high absorption rate, large CO2 capacity, low energy consumption", promoting both absorbtion and desorbtion.In this work, N-Methyldiethanolamine aqueous compounded with polar aprotic solvents, such as alcohols and amides were studied:on one hand, compound absorbents were systematically investigated by experiments; on the other hand, theoretical calculation and parameter correlation were performed in this research. In addition, the compounded absorber were investigated in throttling expansion process, showing great advantage in saving energy and matrtial consumption.As is shown in our studies, compound acborbent composed of mass fraction 30%MDEA+30%n-propanol+40%H2O showed more advantage than 30%MDEA. In the case of absorbing at 20℃ and desorbing at 70℃, CO2 desorption efficiency is as high as 90.9%, CO2 loading is 1.90mol/kg and CO2 absorbing rate is 0.071mmol/s.Compared with MDEA aqueous, compounded absorbent can promote absprbtion and desorbtion simultaneously, which show significance in lower energy consumption and process cost. Besides, theory study reveals the mechanism that solvent effection contribute to the promotion of compounded absorbent.