Adsorption temperature-swing

The extensive literature on fixed-bed adsorber modeling and analysis has been discussed elsewhere (Wankat, 1986 Yang, 1987 Suzuki, 1990 Tien, 1994 Bas-madjian, 1997 Crittenden and Thomas, 1998). The theoretical analyses primarily resort to equilibrium theory, that is, mass and heat transfer rates are assumed to be instantaneous. Because the adsorption and desorption steps in TSA are operated slowly, each spanning for hours, the equilibrium theories are indeed good. Often, quantitative agreements are obtained between theory and experiment (see 

Chapter 5, Yang, 1987). Mass and heat transfer are considered dispersive forces, which have a dispersive or smearing effect on the concentration and temperature fronts. The detailed bed profiles and breakthrough curves can be calculated only by the numerical solution of the mass and heat balance equations (Yang, 1987), coupled with the equations for equilibrium adsorption from mixture. 

The regeneration step in the TSA cycle requires time to heat, desorb, and cool the bed. It is often the time-limiting step in the TSA cycle and is also the most complex and least nnderstood one. The following discussion on TSA focuses on the regeneration step and presents some simple rules for design. 

Minimum Purge Temperature. The minimum purge temperature was derived based on the equihbrinm theory by Basmadjian et al. (1975a and 1975b), which has been discussed in detail elsewhere (Yang 1987 Basmadjian, 1997). 

Efficient desorption is accomplished at temperatures above the characteristic temperature, Tq. The characteristic temperature is equal to the temperature at which the slope of the adsorption isotherm at the origin is equal to CpsICpb, the ratio of the heat capacities of the soUd phase and the inert carrier gas. For a 

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Many different forms of the energy balance have been used in fixed-bed adsorption studies. The form chosen for a particular study depends on the process considered (e.g., temperature swing adsorption or pressure swing adsorption) and on the degree of approximation that is appropriate. 

TSA [Thermal (or Temperature) swing adsorption] A method for separating gases by cyclic adsorption and desorption from a selective adsoibent, at alternating temperatures. Less commonly used than PSA. 

Temperature standards, 75 749 Temperature swing adsorption (TSA) process, 73 459, 7 636-642 damage to internal structure of adsorbent, 7 636 design, 7 656 regeneration, 7 655... 

TAR tee TDM toe TPES TSA TTW IPCC Third Assessment Report Tons of coal equivalent Transport demand management Tons of oil equivalent Total primary energy supply Temperature swing adsorption Tank-to-wheel... 

Compared to adsorption s use in bulk-gas separations, its use in gas purifications is much more frequent (see Table I and references 13, 36 and 37), and the technology is, for the most part, more conventional Temperature-swing adsorption, often combined with inert-purge stripping, is by far the most common process used Two or more fixed beds operated in parallel, typically with one adsorbing and one or more regenerating, constitute the standard flowsheet ... 

Temperature-swing adsorption processes have to identical, parallel adsorption beds. One of the beds is in the adsorption cycle while the other bed is being regenerated by heating with a regenerating gas. The two beds generally operate 180 degrees out of phase (Knaebel, 1999). 

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