Carbon dioxide (CO2) is the largest volume contributor and the fastest growing component of greenhouse gases. Based on current technology the only commercially available process that can absorb a reasonable amount of CO2 from flue gases is chemical absorption. The other techniques are generally less energy efficient and more expensive. Microchannel technology can be used to enhance the mass transfer rate by increasing surface-to-volume ratio and improving the thermal controllability of the absorption process. In the current study we investigated the performance of microchannel contactors for absorption of
CO2 in aqueous diethanolamine (DEA). A series of experiments was performed to measure CO2 absorption rate and removal efficiency for various gas-to-amine flow rate ratios. The rate of absorption was determined based on the variation of electrical conductivity of the aqueous DEA due to the CO2 absorption process. The effect of contactor length was studied for 200, 500, and 800 mm long microchannels. The pressure drops of two-phase flow for various flow rate ratios and microchannel length were measured. The results demonstrated high potential of the microchannel contactors for enhancement of the absorption process.
The removal of acidic gases such as carbon dioxide from gas streams is an important process in the process industry. For example, in gas sweetening at least 4% by volume of raw natural gas consists of CO2, which must be reduced to 2% to prevent pipeline corrosion, to avoid consuming excess energy for transport, and to increase heating value. Aaron and Tsouris [1] reviewed various methods for the separation of CO2 from flue gas and provide a ranking of various methods. They ranked CO2 separation based on membrane diffusion as the most promising method. However, they noted that the technology is still at the research and development stage, and it is still a challenge to find the material that can operate at high enough temperatures. The second most promising separation method, according to their ranking, was absorption. Based on current technology, the only commercially available process that can absorb a reasonable amount of CO2 from flue gases is chemical absorption. However, the absorber columns used in industry are generally bulky and require large amounts of expensive amines to operate.
Numerous studies have focused on improving gas-liquid reactor performance via process intensification. In recent years, microreactors featuring two-phase flow in well-defined microchannel structures with diameters in the order of microns to hundreds of microns have received significant attention from industrial and academic communities because of their potential for enhancement of mass and heat transfer. These microreactors offer several advantages over their conventional counterparts. They feature high surface-to-volume ratios, leading to high interphase mass transfer rates, and they provide superior heat transfer control and thermal management. In addition, they can lead to substantial reductions in reactor volume and the amount of chemicals required.
