Energy-efficient evaporation process with means for vapor recovery
First Claim
1. An energy-efficient process for the recovery of latent heat from a drying process comprising (1) contacting a material containing a volatile liquid with a gaseous drying medium and supplying heat to said drying medium or to said material and thereby producing an exhaust mixture of noncondensable gas and condensable vapor, (2) separating the condensable vapor in said exhaust mixture by passing it through a nonporous nonionic polymeric membrane which is substantially permeable to said condensable vapor and substantially impermeable to said noncondensable gas, (3) transferring said separated condensable vapor, together with the latent heat of condensation contained therein, to a compressor, (4) compressing in said compressor said separated condensable vapor, and (5) condensing said separated condensable vapor by heat exchange, thereby recovering the latent heat of condensation of said separated condensable vapor.
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Accused Products
Abstract
A process is disclosed for the recovery and reuse of heat contained in the wet exhaust gases emanating from a solids dryer or liquor concentrator, particularly one in which drying or concentration is facilitated by purging the vapor with some noncondensable gas such as air or nitrogen. Water or solvent vapor in the moist exhaust mixture is separated from the noncondensable gas or gases by preferentially passing the vapor through a semipermeable membrane. The water or solvent vapor is then compressed and subsequently condensed in a heat exchanger, permitting recovery of its latent heat of vaporization for reuse in the evaporation process. In a drying process, this recovered energy is conveniently used to reheat the dry gases that exit from the membrane separator, permitting the hot, dry gases to be recirculated through the dryer. Alternatively, an indirect heat exchanger may be used to transfer this heat to the material being dried. In an evaporative process for the concentration of a liquor, the recovered energy may be used either to preheat the dry purge gases or to heat the dilute liquor being concentrated.
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Citations
37 Claims
- 1. An energy-efficient process for the recovery of latent heat from a drying process comprising (1) contacting a material containing a volatile liquid with a gaseous drying medium and supplying heat to said drying medium or to said material and thereby producing an exhaust mixture of noncondensable gas and condensable vapor, (2) separating the condensable vapor in said exhaust mixture by passing it through a nonporous nonionic polymeric membrane which is substantially permeable to said condensable vapor and substantially impermeable to said noncondensable gas, (3) transferring said separated condensable vapor, together with the latent heat of condensation contained therein, to a compressor, (4) compressing in said compressor said separated condensable vapor, and (5) condensing said separated condensable vapor by heat exchange, thereby recovering the latent heat of condensation of said separated condensable vapor.
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8. In an industrial drying process for drying material, said process utilizing hot, dry gas as the drying medium and producing moist or solvent-containing exhaust gas, the improvement comprising:
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(a) separating the exhaust gas into a warm, dry noncondensable gas component and a condensable vapor component by passing the condensable vapor in said exhaust mixture through a nonporous nonionic polymeric membrane that is substantially permeable to said condensable vapor and substantially impermeable to said noncondensable gas; (b) transferring said separated condensable vapor, together with the heat of condensation contained therein, to a compressor; (c) compressing in said compressor the condensable vapor in said condensable vapor component; (d) condensing the condensable vapor in said condensable vapor component by heat exchange, thereby recovering the heat of condensation of said condensable vapor; and (e) transferring by heat transfer means said heat of condensation to said hot, dry gas-drying medium or to the material being dried. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 32)
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22. In a process for the concentration of a liquid mixture or solution by evaporation, said process comprising heating the liquid mixture or solution, contacting the liquid mixture or solution with a substantially dry, gaseous stream, and thereby producing a moist, gaseous exhaust mixture, the improvement comprising:
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(a) separating the moist, gaseous exhaust mixture into a warm, dry noncondensable gas component and a condensable vapor component by passing said exhaust mixture through a nonporous nonionic polymeric membrane that is substantially permeable to said condensable vapor component and substantially impermeable to said noncondensable gas component; (b) transferring said separated condensable vapor, together with the heat of condensation contained herein, to a compressor; (c) compressing in said compressor the condensable vapor in said condensable vapor component; (d) condensing the condensable vapor in said vapor component by heat exchange, thereby recovering the heat of condensation of said condensable vapor; and (e) transferring by heat transfer means said heat of condensation to the gaseous drying medium or to the material being concentrated. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 33, 34, 35, 36, 37)
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Specification