Study Of CO₂ absorption into aqueous diethanolamine (Dea) using microchannel reactors

Removal of CO₂ from gas streams is a major step in the purification of natural gas and of interest for carbon capture and storage applications. Industrial scale implementations of the process with most state of the art technologies use aqueous alkanolamines as liquid solvents to chemically absorb CO₂. Although the kinetics of the absorption process are fast, sufficient absorption performance can only be met by very large columns due to the limited interfacial area present between gas and liquid phases in these systems. In the present study we utilize micro structure surfaces in two-phase regime to provide substantially higher interfacial area and hence enhanced mass transfer characteristics. We report experimental data on the separation of CO₂ from a gas stream containing 10% CO₂ and 90% N₂ by volume. An aqueous solution of 20% diethanolamine in water by weight was used as the solvent, and absorption performance was measured by potentiometric titration of the liquid product with potassium hydroxide. The microchannel-based reactors had circular cross-sectional geometry with an inner diameter of 762 μm and two different lengths of 10 cm and 30 cm. Additionally, blank experiments were performed for component-level analysis. Parametric studies varying the gas and liquid phase superficial velocities were conducted and discussed. The potential to use microchannel reaction systems in multiple pass configurations for scaled up implementation was investigated. The present work achieved mass transfer coefficients that are at least one order of magnitude higher than those of most conventional absorption technologies, thus indicating the substantial process intensification that can be achieved using the proposed microreactor system for CO₂ separation processes.