Theoretical investigations on the effect of absorbent type on carbon dioxide capture in hollow-fiber membrane contactors

Abstract

Chemical absorption of carbon dioxide from flue or natural gas in hollow-fiber membrane contactors (HFMCs) has been one of the most beneficial techniques to alleviate its emission into the environment. A theoretical research study was done to investigate the change in membrane specifications and operating conditions on CO 2 absorption using different alkanolamine solvents. The mathematical model was developed for a parallel counter-current fluid flow through a HFMC. The developed model's equations were solved based on finite element method. The simulations revealed that the increase in membrane porosity, length and the number of fibers has a positive impact on CO 2 removal, while the gas flow rate and tortuosity enhancement resulted in the reduction of CO 2 absorption. Furthermore, it was found that 4-diethylamino-2-butanol (DEAB) with approximately 100% CO 2 absorption is suggested as the best solvent in this system, but ethyl-ethanolamine (EEA) with only 46% CO 2 absorption had the lowest capacity for CO 2 absorption (DEAB>MEA>EDA>MDEA> EA>EEA). It is worth pointing out that the CO 2 absorption can be improved using EEA solvent via change in membrane specifications such as increase in membrane porosity, length and the number of fibres.

Intensification of CO2 absorption using MDEA-based nanofluid in a hollow fibre membrane contactor

“…2 , MDEA-based NF flows in the tube subdomain, whereas the gas mixture fed to the shell subdomain in the opposite direction. The mechanistic model is built axis-symmetrically (two dimensional) because of the non-existence of angular gradient 6 . Here, we used Happel’s formula to estimate the shell side radius (Fig.…”

“…The mathematical formula that describes the transport of CO 2 molecules from the gas phase (N 2 and CO 2 mixture) to MDEA-based NF is the continuity equation, which can be expressed as 25 , 26 : where C , R and N refer to the CO 2 concentration, reaction rate, and mass flux, respectively. The mass transfer flux is calculated using 6 , 26 : where D is the diffusivity and V z is the velocity. The steady-state mass transfer equation in the shell side is then derived as 27 : …”

“…Here, the fibers are considered to be filled with the gas phase due to the hydrophobic polymer used as the membrane and controlling the operational conditions 6 .…”

“…Chemical absorption in aqueous amine solvents is the most common approach for CO 2 capture at industrial scale because of its advantages such as high efficiency and mature process 6 . Methyldiethanolamine (MDEA) is a tertiary amine and cost-effective absorbent which is widely used for CO 2 removal owing to its acceptable CO 2 absorption capacity, carbamate formation, low corrosion rate, and lower heat regeneration 7 .…”

Mechanistic modeling and numerical simulation of axial flow catalytic reactor for naphtha reforming unit

“…From the enthalpy balance and the combination of the same kinetic and thermodynamic equations, the equation of temperature distribution in the reactor is obtained. The equations related to the mass balance of all the chemical components involved in the reaction for the porous catalytic reactor are as follows [17][18][19][20][21][22]:…”