A Rigorous Membrane Gas-Solvent Contactor Model for Flowsheet Simulation of the Carbon Capture Process

Abstract

A rate-based membrane gas-solvent contactor model was programmed in Aspen Custom Modeler (ACM) and interfaced with the Aspen Plus software suite to enable flowsheet simulations of carbon capture processes. After validation with different sets of laboratory and pilot plant data, the model's rigorous approach was examined against the commercial RadFrac model of Aspen Plus used for conventional absorption−stripping column simulations. Under identical processing conditions, both models predicted similar results for the temperature, flow rate, and composition of the streams leaving the absorption and stripping units. Differences between the two models were most pronounced for liquid and gas temperature profiles, which were attributed to the different energy balance methods used in the two models, but the difference was not large enough (∼10 °C) to influence the mass transfer within the membrane contactor, as the composition and flow rate of leaving streams were almost identical to that of the RadFrac model. A process intensification factor analysis showed that membrane contactor technology could reduce the volume of equipment required by a magnitude of 44 to undertake the same carbon capture ratio as the conventional column process.

Simulation model of carbon capture with MEA and the effect of temperature and duty on efficiency

“…Analyzing the solvent composition reveals that the ratio between MDEA and PZ is a crucial design parameter for carbon adsorption efficiency and process energy demand. Sarodan et al [27] reported that the discrepancy between the two models for the liquid and gas temperature profiles was sufficient (approximately ten degrees Celsius) to affect the transfer. Because the composition and flow rate of the outflow streams were nearly identical to what the RadFrac model predicted, the crime did not occur in the membrane contactor.…”

Numerical modelling and process simulation of a post-combustion CO2 capture pilot plant based on a membrane contactor unit

“…Mass and energy balances are evaluated for the gas and liquid side, and chemical equilibrium is solved for the liquid phase. This kind of modelling approach has been presented in several journal publications [10,12,13,18]. The following assumptions have been made during model development:…”

“…The estimation of the equilibrium concentration for each chemical species is done according to the model proposed by Astarita et al [19] and already employed in similar studies [12,13,18]. This approach is based on the evaluation of the equilibrium reaction constants (i.e., K eq,i , where i represents a specific chemical reaction) and the resolution of the molar balance equations assuming that the concentration of �CO 3 -2 � is negligible and all the dissolved CO2 is absorbed via reaction (2.4).…”

“…The expression of the Sherwood number for the gas phase is taken from [18], while the Sherwood number for the liquid phase is estimated using the Chilton-Colburn analogy [21,22].…”

“…The membrane heat transfer coefficient (h M [W/m 2 /K]) is defined under the assumption that the pores are filled with the gas, and it is the results of the effective contribution to conductive heat transfer trough the membrane material (λ M is the thermal conductivity of the membrane assumed to be 0.2 [W/m/K]) and the gas phase (λ G is the thermal conductivity of the gas [W/m/K]) [18]:…”