Refrigeration – Cryogenic treatment of gas or gas mixture – Separation of gas mixture
Reexamination Certificate
1999-10-05
2001-02-27
McDermott, Corrine (Department: 3744)
Refrigeration
Cryogenic treatment of gas or gas mixture
Separation of gas mixture
Reexamination Certificate
active
06192706
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to the production of carbon monoxide and is particularly useful for the production of carbon monoxide at relatively low production rates.
BACKGROUND ART
Carbon monoxide is used as a reactant in a number of important industrial chemical synthesis processes. Carbon monoxide may be produced by the partial oxidation of hydrocarbons followed by purification, including the removal of carbon dioxide using chemical based absorption typically involving an amine based reactant. While such a system is very effective for the production of carbon monoxide on a large scale, it is cost prohibitive for the production of carbon monoxide on a relatively small scale such as at a production rate of less than 50,000 cubic feet per hour.
Accordingly it is an object of this invention to provide an improved system for producing carbon monoxide which will enable effective production of carbon monoxide even at relatively low production rates.
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 producing carbon monoxide comprising:
(A) providing a feed comprising carbon monoxide, carbon dioxide, hydrogen and hydrocarbons, and passing the feed through a membrane separation unit to separate the feed into a permeate, which comprises some of the hydrogen and carbon dioxide of the feed, and into retentate which has a higher concentration of carbon monoxide than does the feed;
(B) cooling the retentate to remove essentially all of the remaining carbon dioxide, and passing the resulting fluid comprising carbon monoxide, hydrogen and hydrocarbons into a first cryogenic separation column as first column feed;
(C) separating the first column feed in the first cryogenic separation column into hydrogen top fluid and into bottom fluid comprising carbon monoxide and hydrocarbons;
(D) passing bottom fluid into a second cryogenic separation column and separating the bottom fluid in the second cryogenic separation column into carbon monoxide vapor and hydrocarbon liquid; and
(E) recovering carbon monoxide vapor from the upper portion of the second cryogenic separation column as product carbon monoxide.
Another aspect of this invention is:
Apparatus for producing carbon monoxide comprising:
(A) a membrane separation unit and means for passing a feed comprising carbon monoxide, carbon dioxide, hydrogen and hydrocarbons to the membrane separation unit;
(B) a carbon dioxide removal cooler and means for passing fluid from the membrane separation unit to the carbon dioxide removal cooler;
(C) a first cryogenic separation column and means for passing fluid from the carbon dioxide removal cooler to the first cryogenic separation column;
(D) a second cryogenic separation column and means for passing fluid from the lower portion of the first cryogenic separation column into the second cryogenic separation column; and
(E) means for recovering fluid from the upper portion of the second cryogenic separation column as product carbon monoxide.
As used herein the term “membrane separation unit” means a system which separates gas components from gas mixtures using polymeric membranes and employing gas concentration and pressure gradients across the membrane.
As used herein the term “carbon dioxide removal cooler” means a system which receives a gas stream comprising carbon dioxide and wherein the gas stream is cooled so as to condense and/or sublime carbon dioxide out from the gas stream.
As used herein the term “hydrocarbons” means one or more hydrocarbon species having up to 5 carbon atoms. Examples include methane, ethane, acetylene and propane.
As used herein the term “column” means a distillation or fractionation column or zone, i.e., a contacting column or zone wherein liquid and vapor phases as countercurrently contacted to effect separation of a fluid mixture, as for example, by contacting or the vapor and liquid phases on a series of vertically spaced trays or plates mounted within the column and/or on packing elements such as structured or random packing. For a further discussion of distillation columns, see the Chemical Engineer's Handbook fifth edition, edited by R. H. Perry and C. H. Chilton, McGraw-Hill Book Company, New York, Section 13,
The Continuous Distillation Process
. Vapor and liquid contacting separation processes depend on the difference in vapor pressures for the components. The high vapor pressure (or more volatile or low boiling) component will tend to concentrate in the vapor phase whereas the low vapor pressure (or less volatile or high boiling) component will tend to concentrate in the liquid phase. Partial condensation is the separation process whereby cooling of a vapor mixture can be used to concentrate the volatile component(s) in the vapor phase and thereby the less volatile component(s) in the liquid phase. Rectification, or continuous distillation, is the separation process that combines successive partial vaporizations and condensations as obtained by a countercurrent treatment of the vapor and liquid phases. The countercurrent contacting of the vapor and liquid phases is adiabatic and can include integral or differential contact between the phases. Separation process arrangements that utilize the principles of rectification to separate mixtures are often interchangeably termed rectification columns, distillation columns, or fractionation columns. Cryogenic separation is a separation process carried out in a column at least in part at temperatures at or below 150 degrees Kelvin (K).
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 fluid with each other.
As used herein the terms “upper portion” and “lower portion” mean those sections of a column respectively above and below the mid point of the column.
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Bergman, Jr. Thomas John
Billingham John Fredric
Couche Michael Robert
Shah Minish Mahendra
Black Donald T.
Drake Malik N.
McDermott Corrine
Praxair Technology Inc.
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