Adsorption refrigerators

Many units have waste heat recovery systems that generate low pressure steam from reaction heat. Such steam is often employed to drive adsorption refrigeration units to cool the reactor feed stream and to increase polymer conversion per pass, an energy-saving process that reduces the demand for electrical power. 

Tamainot-Telto, Z. and Critoph R.E, Adsorption refrigeration using monolithic carbon - ammonia pair. International Journal of Refrigeration, 1997, 20(2), 146 155. 

In addition to the particulate adsorbents listed in Table 16-5, some adsorbents are available in structured form for specific applications. Monoliths, papers, and paint formulations have been developed for zeolites, with these driven by the development of wheels (Fig. 16-60), adsorptive refrigeration, etc. Carbon monoliths are also available as are activated carbon fibers, created from polymeric materials, and sold in the forms of fabrics, mats, felts, and papers for use in various applications including in pleated form in filters. Zeolitic and carbon membranes are also available, with the latter developed for separation by selective surface flow [Rao and Sircar, J. Membrane Sci., 85, 253 (1993)]. 

The physical processes by which natural gas liquids are recovered include phase separation, cooling, compression, absorption, adsorption, refrigeration, and any combination of these. Obviously the definition already stated excludes refinery light volatiles produced by the destructive decomposition of heavy petroleum fractions and it also excludes liquids that may be produced synthetically from natural gas. These distinctions are of economic importance in considering our basic energy reserves. Both the refinery volatiles and the synthetic liquids represent conversion products from other hydrocarbons and the conversion is usually attended by a considerable loss. Thus it has been stated that only about 47% (17) of the energy of natural gas is realized in the liquid hydrocarbon products of the Fischer-Tropsch type of synthesis. 

Fluor Process. The Fluor process [280], [934], [940], [1094] uses the proprietary propylene carbonate based C02 removal system with adsorption refrigeration using low level heat downstream of the low-temperature shift. Methanation and C02 removal are placed between the compression stages and thus operate at higher pressure. With a value of 32 GJ/t NH3 [934] this is not really a low-energy concept. 

Critoph, R.E. and Metcalf, S.J. (2004). Specific cooling power intensification limits in ammonia-carbon adsorption refrigeration systems. Applied Thermal Engineering, Vol. 24, pp. 661-678. 

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