Thermal Swing

Thermal Swing. In thermal swing operation the bed is regenerated by heating, usually with a stream of hot gas (or less commonly with hot liquid), to 

FIGURE n.U Schematic diagram showing the two basic modes of operation (a) cyclic batch two-bed system (b) continuous countercurrent system with adsorbent recirculation. Concentration profiles through the bed are indicated. A is the more strongly adsorbed species. 

TABLE ILL EKamples of Cyclic Adsorption Separation Processes 

Process Liquid (1) or Gas Phase (G) Adsorbent Selectivity Regeneration Method 

Drying of gas streams G 13X, 4A, or 3A mol. sieve Equilib. T swing or P swing 

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Steps. Thermal-swing cycles have at least two steps, adsorption and heating. A cooling step is also normally used after the heating step. A portion of the feed or product stream can be utilized for heating, or an independent fluid can be used. Easily condensable contaminants may be regenerated with noncondensable gases and recovered by condensation. Water-iminiscible solvents are stripped with steam, which may be condensed and separated from the solvent by decantation. Fuel and/or air may be used when the impurities are to be burned or incinerated. 

Stea.ming Retjuirements. The steaming of fixed beds of activated carbon is a combination of thermal swing and displacement purge swing. The exothermic heat released when the water adsorbs from the vapor phase is much higher than is possible with heated gas purging. This cycle has been successhiUy modeled by equiUbrium theory (128). 

Regenerative adsorption units can be operated by a thermal-swing cycle, pressure-swing cycle, displacement-purge cycle, or inert-purge cycle. Combinations of these are frequently employed. 

Fig. 11. Schematic illustration of the thermal-swing and pressure-swing cycles. In thermal swing, the differential loading, Av, is given by — x at...

D. Basmadjian, Dying, 3, 307—357 (1984). A review of thermal-swing iadustrial dryiag appHcations with 108 references. 

Do Not Require Process Modifications iv. Thermal swing adsorption V. Pressure swing adsorption... 

There should be a means to monitor the several cycles of the desiccant drier, particularly the thermal-swing unit. 

Nelson, T.O., P.D. Box, D.A. Green, and R.P. Gupta, Carbon Dioxide Recovery from Power Plant Flue Gas using Supported Carbonate Sorbents in a Thermal Swing Process, Sixth Annual Conference on Carbon Capture and Sequestration, Pittsburgh, PA, May 2007. 

A temperature-swing, or thermal-swing, adsorption (TSA) process cycle is one in which desorption takes place at a temperature much higher than adsorption. The elevation of temperature is used to shift the adsorption equilibrium and affect regeneration of the adsorbent. Figure 16-38 depicts a simplified (and ideal) TSA cycle. The feed fluid containing an adsorbate at a partial pressure of p1 is passed through an... 

The operating temperature range is 450 to 700°C either pressure-swing or thermal-swing modes can be used. 

Desorption Displacement desorption Gas separation adsorption Liquid separation adsorption Pressure swing adsorption Thermal swing adsorption asbestos fibers, 3 304 for bioremediation, 3 782 capillary condensation, 1 585, 591 dessicants and, 3 375-377 detergency and, 3 428 129 in dispersions, 3 707 filler measurement via, 22 571 general separation heuristics for,... 

Molecular sieves are crystalline metal aluminosilicates (1). Openings in their crystal structure permit passage of many gas constituents while preferentially adsorbing large, polar, or unsaturated compounds. Acid gas compounds may be adsorbed by certain types of molecular sieves. When used for H2S removal, the sieve is regenerated by a thermal swing cycle CL), being heated to release the H2S for downstream sulfur recovery. 

In thermal-swing regeneration, the bed may need a substantial time to reach the regeneration temperature. The high temperatures may also affect the product and accelerate the ageing processes in the adsorbent. 

While adsorption equiUbrium considerations do justify the possibility to regenerate an adsorbent bed completely and to uniform levels, this is rarely achieved in practice in either thermal swing adsorption and is almost never the case in pressure swing adsorption. Some residual sorbate is always left on the sorbent and in general, except for TSA with only one or two sorbates, the residual loadings are almost always found as a non-uniformly distributed profile across the length of the bed. 

Thermal swing adsorption (TSA) has been practiced with zeoHte molecular sieves for more than 50 years. In the following sections 1 discuss design methods and provide some reference data so that the design process can be understood. 

The requirements for an effective thermal swing design include ... 

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