CO2Chemical Absorption And Its Combination With Fuel Extraction From Algae

Global warming caused by CO2emission from fossil combustion is threatening the ecological environment and human survival. Fossil fuels will continue to play an important role in both generation of heat and power and in heavy industrial manufacturing operations for the foreseeable future. Carbon capture and storage (CCS) is promising to achieve a meaningful reduction in CO2emissions in the short term. Post-combustion CO2capture with low cost and energy consumption needs to be further studied. In this dissertation, the effects of impurities on CO2capture using a hollow fiber membrane contactor, the performance of amine+ionic liquid+water absorbent used in an CO2absorption/desorption system, and the feasibility of fuel extraction from algae combined with CO2absorption have been systemically investigated. The main contents and conclusions are as follows:With a polypropylene (PP) hollow fiber membrane contactor as absorber and a packed column as stripper, the influence of SO2and O2on the CO2capture from coal-fired power plant flue gas was investigated in an absorption-desorption experimental set-up using aqueous monoethanolamine (MEA) as the absorbent. The experimental results showed that the MEA loss per ton captured CO2of each campaign with different gas source was:CO2-N2:1.3kg, CO2-O2(6%)-N2:3.32kg, CO2-SO2(294ppm)-N2:4.72kg, CO2-O2(6%)-SO2(30ppm)-N2:4.49kg. SO2in the flue stream plays a more important role than O2in CO2capture. When the SO2concentration of flue stream under30ppm which meets the requirement by national standard, the largest contribution to monoethanolamine loss was made by evaporation during desorption, followed by the formation of sulfate and heat stable salts.To reduce MEA loss and meanwhile lower down the energy consumption during CO2desorption, an aqueous amine solution mixed with ionic liquid (30wt%MEA+40wt%[bmim][BF4]+30wt%H2O) was proposed. The energy consumption of the mixed ionic liquid solution for absorbent regeneration was37.2%lower than that of aqueous MEA solution. The MEA loss per ton of captured CO2for the mixed solution was reduced to1.16kg. No ionic liquid loss was detected. In addition, the mixed ionic liquid solution showed a low viscosity of3.54mPa·s at50℃, indicating that the ionic liquid disadvantage of high viscosity can be overcome for absorbent delivery of CO2capture.The abilities of CO2capture and lipids extraction by algae+IL system were utilized to decrease the energy consumption. Chlorella hydrolysis integrating CO2removal by ILs ([bmim][BF4],[bmim]Cl and [amim]Cl) was demonstrated in this study. The addition of CO2to [bmim][BF4] can increase the lipids yield from14.2wt%to15.6wt%. The value of net energy gain increased from9.41to11.7with the CO2addition to [bmim][BF4]. Considering the compensated energy by CO2capture, the energy consumption of algae fuel extraction process integrating CO2absorption could be decreased to be10%of that of conventional solvents extraction process.