Since the time of the industrial revolution, the atmospheric CO(2) concentration has risen by nearly 35 % to its current level of 383 ppm. The increased carbon dioxide concentration in the atmosphere has been suggested to be a leading contributor to global climate change. To slow the increase, reductions in anthropogenic CO(2) emissions are necessary. Large emission point sources, such as fossil-fuel-based power generation facilities, are the first targets for these reductions. A benchmark, mature technology for the separation of dilute CO(2) from gas streams is via absorption with aqueous amines. However, the use of solid adsorbents is now being widely considered as an alternative, potentially less-energy-intensive separation technology. This Review describes the CO(2) adsorption behavior of several different classes of solid carbon dioxide adsorbents, including zeolites, activated carbons, calcium oxides, hydrotalcites, organic-inorganic hybrids, and metal-organic frameworks. These adsorbents are evaluated in terms of their equilibrium CO(2) capacities as well as other important parameters such as adsorption-desorption kinetics, operating windows, stability, and regenerability. The scope of currently available CO(2) adsorbents and their critical properties that will ultimately affect their incorporation into large-scale separation processes is presented.

Adsorbent Materials for Carbon Dioxide Capture from Large Anthropogenic Point Sources

The Maxwell-Stefan approach to mass transfer

Pressure swing adsorption (PSA) processes have been used extensively for gas separation, especially in the separation of hydrogen from CO2, and in air purification. The objective of this paper is to examine the economic feasibility of pressure swing adsorption (PSA) for recovering CO2 from postcombustion power plant flue gas. The analysis considers both high-pressure feed and vacuum desorption using commercial adsorbent 13X, which has a working capacity of 2.2 mol/kg and CO2/N2 selectivity of 54. The results show that using vacuum desorption reduces the capture cost from US$57 to US$51 per ton of CO2 avoided and is comparable in cost to CO2 capture using conventional MEA absorption of US$49 per ton of CO2 avoided. In this paper, a sensitivity analysis is also presented showing the effect on the capture cost with changes in process cycle; feed pressure and evacuation pressure; improvements the adsorbent characteristics; and selectivity and working capacity. The results show that a hypothetical adsorbent wi...

Reducing the Cost of CO2 Capture from Flue Gases Using Pressure Swing Adsorption

Carbon capture by physical adsorption: Materials, experimental investigations and numerical modeling and simulations - A review

Separation and purification of multicomponent gas mixtures by adsorption is an established process technology. Adsorptive process design requires accurate data on multicomponent gas adsorption equilibria, kinetics, and heats as input variables. These data often cannot be predicted by using today's models, particularly for complex practical systems where the gas mixtures have adsorbates of different sizes and polarities, and the adsorbent is energetically heterogeneous. There is a large volume of pure gas and some binary gas adsorption equilibrium and kinetic data in the published literature, but multicomponent adsorption data are rare. The data for heats of adsorption are only emerging. There is a desperate need to generate a multicomponent adsorption database for better understanding of the complex phenomenon, for seriously testing existing models, and for development of new models. Two recently developed methods called “isotope exchange technique” and “microcalorimetry for adsorption heats” are recommen...

Basic Research Needs for Design of Adsorptive Gas Separation Processes

A theoretical and experimental study is performed for the bulk separation of a ternary mixture by pressure swing adsorption. Three concentrated products can be obtained by cycling the pressure in the adsorber. Three models are formulated for the cyclic process: equilibrium, Knudsen diffusion, and Knudsen plus surface diffusion. The latter model provides the best results when compared with the experimental data, due to the important contribution of surface flux to the total flux in the sorbent pores.

Bulk separation of multicomponent gas mixtures by pressure swing adsorption: Pore/surface diffusion and equilibrium models

Extension de l'equation de Dubinin-Astakhov au calcul du volume d'adsorption d'un melange gazeux sur un materiau poreux

A simple potential-theory model for predicting mixed-gas adsorption

The published theoretical models for pressure swing adsorption (PSA) are of either the equilibrium type, i.e., instantaneous equilibrium is assumed between the gas and adsorbed phases, or the diffusion type considering only a monodisperse pore structure. There is reason for doubt that either type of model is applicable to adsorption processes using zeolite sorbent, which has a bidisperse pore structure. Commercial zeolite sorbents contain crystals of the size 1-9 microns that are pelletized with a binder. Sorption is entirely within the crystals, which contain micropores, whereas the binder contains macropores with a negligible sorption capacity. This paper presents a general PSA model for zeolite sorbents. Both micropore and macropore diffusion are considered. The mathematical complexity of the pore diffusion equations for the two types of pores is reduced by assuming parabolic concentration profiles in both crystals and pellets. Thus the two partial differential equations are converted into ordinary differential equations containing only time derivatives, and the burden of integration along the radial distance is completely eliminated. The model is general enough to be applied to bulk, multicomponent separations using any PSA cycle. The specific separation discussed in this work is the bulk separation of a hydrogen methane mixture using 5Amore » zeolite. The boundary conditions in the model depend on the PSA cycle.« less

S. J. Doong

Papers

Bulk separation of multicomponent gas mixtures by pressure swing adsorption: Pore/surface diffusion and equilibrium models

A simple potential-theory model for predicting mixed-gas adsorption

Bidisperse pore diffusion model for zeolite pressure swing adsorption.

Bulk separation of multicomponent gas mixtures by pressure swing adsorption: pore/surface diffusion and equilibrium models