Multiphase flow regimes study in microchannel reactor for Co2 absorption application

Abstract. The use of sodium hydroxide (NaOH) as the absorbent for carbon dioxide (CO2) capture is considered interesting in commercial point of view due to the obtained products, sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3). Conventional absorbers have been used to remove the impurity in the natural gas but the low interfacial area due to their large volume has resulted in poor interfacial mass transport. Microchannel reactor which believed able to improve the mixing and mass transfer has been used to solve the problems. Hence, the purpose of this work is to study the characteristics of multiphase flow regimes in the CO2-NaOH system and to determine the optimum condition for the CO2 absorption in the microchannel reactor by varying the gas-to-liquid, G/L ratio and the NaOH concentration. The G/L ratio varied from 2.33 to 9.00 and the NaOH concentration varied from 0.05 M to 2.00 M. The characteristics of the multiphase flow regimes were observed through digital camera by measuring the slug length, distance of consecutive slug and the interfacial area (S/V). The amounts of CO2 absorbed by the system were estimated based on the quantities of products that existed in the sample to determine the effect of parameters variation. From the experiment, it was found that at highest G/L ratio, the slug length and distance produced was the longest that contributed to the highest S/V due to increase of the gas flowrate. Different from G/L ratio, the increased NaOH concentration would decrease the slug length, distance of consecutive slug, and the interfacial area produced by the slug due to increase of the rate of reaction. As for the effect of G/L ratio and NaOH concentration towards the CO2 absorption, it was observed that the G/L ratio is inversely proportional to the amount of CO2 absorbs while the increase of NaOH concentration would increase amount of CO2 absorbed by the system due to the availability of Na+ to react in the system, therefore the rate of reaction increase.