Study On Biphasic Absorption And Separation Of CO₂in Biogas

The researchers in various countries are paying more attention to the study on renewable energy resources with the decreasing petroleum source. Biogas, an important kind of biomass energy source, has been widely used. The biogas could be used as vehicle fuel and the substitute of natural gas after cleaned and upgraded. For regeneration required large amount of heat energy, the method of chemical absorption is rarely used in biogas upgrading. Some researchers put forward the concept of biphasic absorption, which entails a phase transition during or after absorption. The two phases can be separated into the CO2-rich phase and CO2-poor phase, which reduces the heat amount by just regenerating the CO2-rich phase. Well, the inion liquid and polymer was attracted by some researchers recently, but its synthesis process is complex and cost more. Therefore, our research aimed to investigate a new two-phase absorption solution to reduce the heat used in regeneration. In order to acquire higher absorption capacity and absorption rate than aqueous alkanolamine solution, a series of organic solvents were studied instead of water.In our work, phase changing was observed in enamine/ethanol solution. We used0.1-0.3M TETA/ethanol solution as absorption solution to investigate its absorption rate and absorption capacity with absorption time in double stirred-cell absorber. We found that CO2of0.2M TETA/ethanol solution (200mL) stored in solid product got to81.8%after absorption. This solid product decomposed temperature was90℃, lower than alkanolamine aqueous solutions. What’s more, absorption rate and absorption capacity of TETA/ethanol solution were higher than TETA aqueous and DEA aqueous system. Thus, TETA/ethanol solution has the potential to be used as biphasic absorption solution. The absorption rate, absorption capacity and amine group load of TETA/ethanol were compared with DETA/ethanol and TEPA/ethanol solution. TEPA/ethanol has the highest absorption rate and capacity, while DETA/ethanol has the highest amine group load.