Refrigeration – Cryogenic treatment of gas or gas mixture – Separation of gas mixture
Reexamination Certificate
2000-07-11
2001-10-16
Capossela, Ronald (Department: 3744)
Refrigeration
Cryogenic treatment of gas or gas mixture
Separation of gas mixture
C062S929000
Reexamination Certificate
active
06301927
ABSTRACT:
FIELD OF INVENTION
The present invention relates to methods for separating Carbon Dioxide from gases containing Carbon Dioxide.
BACKGROUND
Many facilities, including petroleum refineries, fertilizer plants, and fermentation plants, produce gases containing Carbon Dioxide (CO
2
). Often the Carbon Dioxide is considered a waste gas, and is merely vented to the atmosphere. In other instances the Carbon Dioxide can be separated out from the remaining gases, and utilized in some manner.
There are numerous known methods for separating Carbon Dioxide from other gases, including absorption by physical and chemical solvents, membranes and molecular sieves, and so forth. Such processes are, however, not particularly cost effective, if the Carbon Dioxide is required to be recovered as a liquefied product. Typically, Carbon Dioxide liquefaction utilized as part of a Carbon Dioxide separation process is performed using an added, (i.e., non-Carbon Dioxide) refrigerant. In prior art
FIG. 1
, for example, feed gas provided by a feed gas stream
100
is compressed in compressor
102
, and is cooled against cooling water in water stream
106
A. The compressed gas is then passed to a gas cooling unit
104
, where it is cooled against cooling water in stream
106
B and refrigerant in stream
108
A. The cooled gas is then dried in gas drier
112
,which typically uses molecular sieve or alumina desiccants. Gas drier
112
uses heat in stream
110
. The desiccant bed is typically heat regenerated after it is fully loaded with moisture. Carbon Dioxide in the dried gas is then liquefied in liquefaction unit
114
against refrigerant in stream
108
B, while other gases remain gaseous. Finally, since undesirable concentrations of impurities may be dissolved in the liquefied Carbon Dioxide, the impurities are removed using a stripping column
116
. The output of the process is a purge stream containing impurities
118
, and a purified Carbon Dioxide stream
120
.
Liquefaction using an added refrigerant as depicted in
FIG. 1
is problematic. For example, refrigerants having high operational efficiency, including ammonia and chlorofluorocarbons (CFCs), are often considered environmentally hazardous, and their use in many geographic areas may be severely restricted or even prohibited. Added refrigerants may also be expensive to purchase and maintain through the life span of the separation process. Still further, refrigerants introduce complexity, which results in increased capital and operational expenses, especially where regulatory changes require the use of a substitute refrigerant.
Thus, there remains a need for methods and apparatus that provides Carbon Dioxide separation without necessarily relying on refrigerants.
SUMMARY OF THE INVENTION
The present invention is directed to methods and apparatus in which Carbon Dioxide is separated from other gases using autorefrigeration. In, general, a feed gas containing Carbon Dioxide is compressed, and then expanded to produce work. Carbon Dioxide in the feed gas is thereby liquefied, and the liquefied Carbon Dioxide is then separated from other components that remain gaseous.
While all commercially viable embodiments are contemplated, embodiments are preferred in which the claimed methods and apparatus provide significant commercial advantages over the prior art. For example, it is preferred that feed gases are employed in which the Carbon Dioxide concentration is at least 30%, more preferably at least 50%, still more preferably at least 80%, and still more preferably at least 90%. All gas percentages herein are given in mole percent. It is also preferred that feed gases be compressed to at least 15 bar absolute in all applications, at least 30 bar absolute in some embodiments, and at least 60 bar absolute in other embodiments. It is still further preferred that the Carbon Dioxide separated out from the feed gas is purified to at least 98% purity, and more preferably at least 99% purity.
It is contemplated that the claimed methods and apparatus will have widespread applicability. Among other things, the Carbon Dioxide containing feed gases can arise from many different sources, including fertilizer plants, chemical plants, refineries, gasification plants, landfills and natural gas supplies. Depending on the source, preliminary purification may involve removal of (1) particulate matter, (2) sulfur compounds, and (3) organic compounds in general.
Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components.
REFERENCES:
patent: 2617484 (1952-11-01), Swearingen
patent: 2632216 (1953-03-01), Eastman
patent: 2996891 (1961-08-01), Tung
patent: 3132016 (1964-05-01), Kurata
patent: 3324668 (1967-06-01), Lohrenz
patent: 3398544 (1968-08-01), Crownover
patent: 3417572 (1968-12-01), Pryor
patent: 3420633 (1969-01-01), Lee
patent: 4822394 (1989-04-01), Zeigler et al.
patent: 4952223 (1990-08-01), Kirshnamurthy et al.
patent: 5233837 (1993-08-01), Callahan
patent: 5956971 (1999-09-01), Cole et al.
patent: 6155076 (2000-12-01), Cullen
Capossela Ronald
Fish & Associates, LLP
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