Rate-Based Modeling of Reactive Absorption of CO₂ and H₂S into Aqueous Methyldiethanolamine

Abstract

A general framework was developed to model the transport processes that take place during reactive absorption when both rate- and equilibrium-controlled reactions occur in the liquid phase. This framework was applied to the selective absorption of H2S from fuel gas containing CO2 using aqueous methyldiethanolamine. A rate-based distillation column module was used for the column integration. The Maxwell−Stefan and enhancement factor theories were utilized. In packed columns, CO2 absorption is controlled by diffusion with fast chemical reactions; in trayed columns it is controlled primarily by physical absorption. Gas−film resistance is never significant for CO2 absorption. For H2S absorption, gas− and liquid−film resistances are important, and diffusion of bisulfide controls the liquid−film resistance. Heat effects produce temperature bulges that can cause equilibrium “pinches” at the maximum temperature. This phenomenon gives an optimum packing height for the H2S removal. Trayed columns are more selective than packed columns for H2S removal, primarily because of the larger number of liquid-film mass transfer units.

Dynamic simulation of MEA absorption process for CO2 capture from power plants

“…Following previous works on packed column design, the two-film theory was applied to describe the heat and mass transfer in this process (Pacheco, 1998;Kenig et al, 1999;Schneider et al, 1999;Al-Baghli et al, 2001;Schneider et al, 2003;Kucka et al, 2003;Lawal et al, 2008;Kvamsdal et al, 2009). The two-film theory model offers several advantages; simpler mathematical formulation (algebraic equations instead of differential equations) that allows for a fast calculation of multicomponent mass transfer; also, many correlations for mass transfer coefficients on the basis of the two-film model have been developed.…”

“…The rate of mass transfer is driven by the chemical potential gradient. In practice, mole fraction or partial pressure difference are the preferred methods to define the driving force (Pacheco, 1998). A model of mass transfer using two-film theory is shown in Figure 3.4.…”

“…One of the most widely used mass transfer coefficients is that proposed by Onda et al (1968) and validated by Bravo and Fair (1982). Several studies on MEA absorption process have used this correlation (Pacheco, 1998;Liu et al, 2006;Kvamsdal et al, 2009;Ghaemi et al, 2009 …”

Removal of hydrogen sulfide in air using cellular concrete waste: Biotic and abiotic filtrations

“…H 2 S also occurs in volcanic and natural gases. Several processes are available for the treatment of hydrogen sulfide, including absorption [1][2][3][4][5], adsorption [6][7][8][9][10][11], and membrane separation [12][13][14][15][16]. These methods generally entail high energy, chemical and disposal costs.…”

“…[1][2]. The bacteria most used in the biofiltration of hydrogen sulfide belong to the genus Thiobacillus, which uses H 2 S as an energy source for growth.…”