Refrigeration – Cryogenic treatment of gas or gas mixture – Liquefaction
Reexamination Certificate
2002-11-19
2003-07-15
Capossela, Ronald C (Department: 3744)
Refrigeration
Cryogenic treatment of gas or gas mixture
Liquefaction
C062S096000, C062S434000
Reexamination Certificate
active
06591632
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to providing refrigeration to a fluid and is particularly advantageous for use in conjunction with the operation of a cryogenic air separation plant for the production of liquefied industrial gas.
BACKGROUND ART
The production of liquefied industrial gas, such as liquid nitrogen, is very costly. Early liquefiers utilized single fluid mechanical refrigeration to provide forecooling at the higher temperatures with a turboexpander to provide refrigeration at lower temperature levels. The mechanical units provided the refrigeration at a fixed temperature. Later dual turbine liquefier cycles which eliminated the forecooler were introduced.
In view of the continuing demand for chilled or liquefied industrial gases, any improvement in systems for producing chilled or liquefied industrial gases would be highly desirable.
Accordingly, it is an object of this invention to provide an improved system for producing chilled or liquefied industrial gases.
SUMMARY OF THE INVENTION
The above and other objects, which will become apparent to those skilled in the art upon a reading of this disclosure, are attained by the present invention, one aspect of which is:
A method for providing refrigeration to a fluid comprising:
(A) compressing a multicomponent refrigerant, condensing the compressed multicomponent refrigerant, expanding the condensed multicomponent refrigerant, and warming the expanded multicomponent refrigerant by indirect heat exchange with said condensing compressed multicomponent refrigerant;
(B) compressing a fluid, cooling a first portion of the compressed fluid by indirect heat exchange with said warming expanded multicomponent refrigerant, and turboexpanding the cooled first portion of the fluid to generate refrigeration; and
(C) warming the refrigeration bearing first portion of the fluid by indirect heat exchange with a second portion of the compressed fluid to provide refrigeration to the second portion of the fluid.
Another aspect of the invention is:
Apparatus for providing refrigeration to a fluid comprising:
(A) a multicomponent refrigerant circuit comprising a compressor, an expansion device, means including at least one cooling heat exchanger pass for passing compressed multicomponent refrigerant from the compressor to the expansion device, and means including at least one warming heat exchanger pass for passing multicomponent refrigerant fluid from the expansion device to the compressor;
(B) a turboexpander, a product heat exchanger, means for passing a first fluid portion in indirect heat exchange relation with said warming heat exchanger pass and thereafter to the turboexpander, and means for passing a second fluid portion to the product heat exchanger; and
(C) means for passing the first fluid portion from the turboexpander to the product heat exchanger, and means for withdrawing refrigerated second fluid portion from the product heat exchanger.
As used herein the term “providing refrigeration” means chilling and/or liquefying.
As used herein the terms “turboexpansion” and “turboexpander” mean respectively method and apparatus for the flow of high pressure fluid through a turbine to reduce the pressure and the temperature of the fluid thereby generating refrigeration.
As used herein the term “expansion” means to effect a reduction in pressure.
As used herein the term “expansion device” means apparatus for effecting expansion of a fluid.
As used herein the term “compressor” means apparatus for effecting compression of a fluid.
As used herein the term “multicomponent refrigerant” means a fluid comprising two or more species and capable of generating refrigeration.
As used herein the term “refrigeration” means the capability to reject heat from a subambient temperature system.
As used herein the term “refrigerant” means fluid in a refrigeration process which undergoes changes in temperature, pressure and possibly phase to absorb heat at a lower temperature and reject it at a higher temperature.
As used herein the term “variable load refrigerant” means a mixture of two or more components in proportions such that the liquid phase of those components undergoes a continuous and increasing temperature change between the bubble point and the dew point of the mixture. The bubble point of the mixture is the temperature, at a given pressure, wherein the mixture is all in the liquid phase but addition of heat will initiate formation of a vapor phase in equilibrium with the liquid phase. The dew point of the mixture is the temperature, at a given pressure, wherein the mixture is all in the vapor phase but extraction of heat will initiate formation of a liquid phase in equilibrium with the vapor phase. Hence, the temperature region between the bubble point and the dew point of the mixture is the region wherein both liquid and vapor phases coexist in equilibrium. In the preferred practice of this invention the temperature differences between the bubble point and the dew point for a variable load refrigerant generally is at least 10° C., preferably at least 20° C., and most preferably at least 50° C.
As used herein the term “indirect heat exchange” means the bringing of two fluids into heat exchange relation without any physical contact or intermixing of the fluids with each other.
As used herein the term “subcooling” means cooling a liquid to be at a temperature lower than the saturation temperature of that liquid for the existing pressure.
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Capossela Ronald C
Ktorides Stanley
Praxair Technology Inc.
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