U.S. patent application number 12/513714 was filed with the patent office on 2010-05-13 for methods for recovering argon.
Invention is credited to Arthur I. Shirley.
Application Number | 20100115992 12/513714 |
Document ID | / |
Family ID | 39536974 |
Filed Date | 2010-05-13 |
United States Patent
Application |
20100115992 |
Kind Code |
A1 |
Shirley; Arthur I. |
May 13, 2010 |
METHODS FOR RECOVERING ARGON
Abstract
Methods for recovering argon from a natural gas stream being
purified are disclosed. The argon will be separated from the
natural gas with helium and other impurities and can be recovered
as liquids from the flash separation step of purifying the helium.
The argon that is separated from the helium can be rectified to
remove further impurities from the argon which can be recovered for
storage or other uses.
Inventors: |
Shirley; Arthur I.;
(Hillsborough, NJ) |
Correspondence
Address: |
The BOC Group, Inc.
575 MOUNTAIN AVENUE
MURRAY HILL
NJ
07974-2082
US
|
Family ID: |
39536974 |
Appl. No.: |
12/513714 |
Filed: |
December 13, 2007 |
PCT Filed: |
December 13, 2007 |
PCT NO: |
PCT/US07/87341 |
371 Date: |
January 12, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60875509 |
Dec 18, 2006 |
|
|
|
Current U.S.
Class: |
62/618 |
Current CPC
Class: |
F25J 3/029 20130101;
F25J 3/0285 20130101; F25J 3/0209 20130101; F25J 3/0257 20130101;
F25J 3/0233 20130101 |
Class at
Publication: |
62/618 |
International
Class: |
F25J 3/00 20060101
F25J003/00 |
Claims
1. A method for recovering argon from a natural gas stream
comprising the steps: a) directing a natural gas stream containing
natural gas, hydrocarbons, crude helium and argon to a helium
recovery unit; b) separating a gas stream containing helium and
argon from said natural gas stream and directing said helium and
argon to a helium purifier; c) purifying said helium; and d)
recovering argon from said purified helium.
2. The method as claimed in claim 1 wherein said helium recovery
unit is a cryogenic rectifier.
3. The method as claimed in claim 2 wherein argon is present in an
amount ranging from 10 ppm to about 10000 ppm.
4. The method as claimed in claim 1 wherein said purified helium is
directed to a helium liquefier or storage.
5. The method as claimed in claim 1 wherein said argon is recovered
by rectification.
6. The method as claimed in claim 5 wherein said rectification is
selected from the group consisting of cryogenic rectification and
selective adsorption.
7. A method for recovering argon from a natural gas stream
comprising the steps; a) separating crude helium and argon from
said natural gas stream; b) directing said separated gas stream to
a first helium separation unit, wherein argon is separated from
said gas stream and directed to an argon concentration unit; c)
directing said helium from said first helium separation unit to an
enriched helium separation unit; d) concentrating argon by removing
nitrogen from said argon concentration unit; and e) recovering
concentrated argon from said argon concentration unit.
8. The method as claimed in claim 7 wherein said helium recovery
unit is a cryogenic rectifier.
9. The method as claimed in claim 8 wherein argon is present in an
amount ranging from 10 ppm to about 10000 ppm.
10. The method as claimed in claim 7 wherein said helium is
withdrawn from said enriched helium separation unit and directed to
a helium liquefier or storage.
11. The method as claimed in claim 7 wherein said argon
concentration unit is a rectification unit.
12. The method as claimed in claim 11 wherein said rectification
unit is a cryogenic rectification unit.
13. The method as claimed in claim 11 wherein said argon
concentration unit is an adsorptive separation unit.
14. A method for recovering argon during the purification of a
helium gas stream mixture separated from a natural gas stream
comprising recovering the liquid bottoms from the purification of
said helium and subjecting said liquid bottoms to a rectification
process to recover argon.
15. The method as claimed in claim 14 wherein said purification of
helium is performed in a helium recovery unit.
16. The method as claimed in claim 14 wherein said helium recovery
unit is a cryogenic rectifier.
17. The method as claimed in claim 16 wherein argon is present in
an amount ranging from 10 ppm to about 10000 ppm.
18. The method as claimed in claim 14 wherein said liquid bottoms
contain argon and nitrogen.
19. The method as claimed in claim 5 wherein said rectification is
selected from the group consisting of cryogenic rectification and
selective adsorption.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from International
Application Serial No. PCT/US2007/087341 filed 13 Dec. 2007
(published as WO 2008/076782 A2, with publication date 26 Jun.
2008), which claims priority from U.S. Provisional Patent
Application Ser. No. 60/875,509, filed Dec. 18, 2006.
BACKGROUND OF THE INVENTION
[0002] Current cosmological models predict the existence of "dark
matter" to explain the observed expansion of the universe. Dark
matter is so called because it hypothetically lacks the property of
emissivity of electromagnetic radiation while still having
substantial mass. Consequently, one shouldn't be able to "see" it
as one can see normal matter reacting to electromagnetic radiation,
but one should be able to detect it by its interactions with normal
matter.
[0003] Many cosmological models predict that dark matter should be
prevalent in a form called WIMPs, or "Weakly Interacting Massive
Particles". The large mass of these particles should make
collisions with similar large atoms of normal matter observable,
and the physics have been derived to quantify what these
interactions should look like. As a result, it appears that argon
forms the perfect collision target for WIMPs. Several investigators
have designed a series of WIMP detectors using liquid Ar to capture
the collisions and distinguish them from other radioactive
phenomena. See "Measurement of the Specific Activity of .sup.39Ar
in Natural Argon", http://www.arxiv.org/pdf/astro-ph/0603131, 6
Mar. 2006.
[0004] A problem exists with the argon source, however, which has
led some to seek new sources. The collision between a WIMP and the
normal Ar isotope, .sup.40Ar, can yield .sup.39Ar as an artifact.
Normal atmospheric argon contains a low level of .sup.39Ar (1 part
in 1 million billion) due to the effects of solar radiation, so
this background level creates "noise" in the detector signal. Argon
from underground sources should in principle be free from .sup.39Ar
and thus would constitute a more sensitive detector for WIMP. See
"A Dating Method with .sup.39Ar", H. H. Loosli, Earth and Planetary
Science Letters, 63 (1983) 51-62.
[0005] Argon is known to exist in natural gases around the world.
See "Helium--Its Relationship to Geologic Systems and its
Occurrence with the Natural Gases, Nitrogen, Carbon Dioxide, and
Argon", Claude A. Tongish, United States, Bureau of Mines Report of
Investigations 8444 (1980).
[0006] Some analyses show argon at average levels around 0.05-0.1%.
This level is quite low and would not be economically recoverable
by conventional means, especially without concomitant recovery and
purification of any contained hydrocarbons and helium. The present
invention is to directed to a means to concentrate and recover
argon economically from natural gas.
SUMMARY OF THE INVENTION
[0007] The present invention relates to a method for recovering
argon from natural gas. The proposed method improves on earlier
methods of trying to separate the argon from the bulk of the
natural gas stream, thereby reducing the size of the stream to be
treated, and allowing for recovery of the valuable components
(hydrocarbons and helium) that result from the separation. The
liquid off the primary feed separator is currently used as part of
liquid nitrogen circuit in the helium plant, but can be replaced by
imported liquid nitrogen.
[0008] Accordingly, there is disclosed a method for recovering
argon from bottoms liquid from the flash separation of a helium gas
mixture containing argon comprising subjecting the bottoms liquid
to a rectification process.
[0009] Further, the present invention provides for a method for
recovering argon present in a natural gas stream during the
purification of a helium gas mixture withdrawn from the natural gas
stream comprising recovering the liquid bottoms from the helium
purification and subjecting the liquid bottoms to a rectification
process specific for argon.
[0010] Accordingly, in one embodiment of the invention, there is
disclosed a method for recovering argon from a natural gas stream
comprising the steps:
a) directing a natural gas stream containing natural gas,
hydrocarbons, crude helium and argon to a helium recovery unit; b)
separating a gas stream containing helium and argon from the
natural gas stream and directing the helium and argon to a helium
purifier; c) purifying the helium; and d) recovering argon from the
purified helium.
[0011] In a further embodiment of the present invention there is
disclosed a method for recovering argon from a natural gas stream
comprising the steps;
a) separating crude helium and argon from the natural gas stream;
b) directing the separated gas stream to a first helium separation
unit, wherein argon is separated from the gas stream and directed
to an argon concentration unit; c) directing the helium from the
first helium separation unit to an enriched helium separation unit;
d) concentrating argon by removing nitrogen from the argon
concentration unit; and e) recovering concentrated argon from the
argon concentration unit.
[0012] In a further embodiment of the present invention, there is
disclosed a method for recovering argon during the purification of
a helium gas stream mixture separated from a natural gas stream
comprising recovering the liquid bottoms from the purification of
the helium and subjecting the liquid bottoms to a rectification
process to recover argon.
[0013] The purification of helium is typically performed in a
helium recovery unit which can be a cryogenic rectifier. Once
purification is achieved the helium is directed to either a helium
liquefier or to storage.
[0014] Argon will typically be present in the natural gas stream in
an amount ranging from about 10 ppm to about 10000 ppm.
[0015] The rectification that is performed on the argon is designed
to separate the argon from any further impurities originating in
the natural gas stream and passing through to the helium separation
processes. This impurity typically is nitrogen and the
rectification processes are typically cryogenic rectification and
selective adsorption.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The FIGURE is a schematic representation of the process
whereby argon is recovered from a helium purification process.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The FIGURE is a schematic representation of a crude helium
stream 1 which has been recovered from a natural gas prior to the
natural gas being added to a pipeline. The crude helium stream
contains impurities such as nitrogen, methane, argon and other
noble gases (see Table 1).
TABLE-US-00001 TABLE 1 Typical composition of crude helium
extracted from the National Helium Reserve. Component Concentration
by Volume He 77.3% N.sub.2 20.3% CH.sub.4 1.6% H.sub.2 8000 ppm Ar
680 ppm CO.sub.2 110 ppm
[0018] This stream is pre-treated to remove hydrogen and carbon
dioxide, and then fed into the primary feed separator A where the
crude helium is flash separated by being cooled to below about
-300.degree. F. The flashed helium which is about 95 to 98% by
volume helium leaves the primary feed separator A through line 2
and enters the enriched helium separator B.
[0019] The enriched helium separator B is also a flash separator
where the further purified helium is further purified and is at a
lower temperature below about -315.degree. F. than the primary feed
separator A. This further purified helium can be recovered through
line 6 for storage purposes. The liquids leaving the enriched
helium separator B are primarily nitrogen and small amounts of
other gases (Table 2) and exit through line 7 to connect with line
4 nitrogen discharge from concentrator C where the nitrogen can be
stored for other uses or discharged to the atmosphere.
TABLE-US-00002 TABLE 2 Typical composition of rejected liquid from
helium purification. Component Concentration by Volume He 0.5%
N.sub.2 96.0% CH.sub.4 3.5% H.sub.2 0 ppm Ar 2800 ppm CO.sub.2 0
ppm
[0020] The bottoms from the primary feed separator A leave through
line 3 and are directed to the .sup.40Ar concentrator C. The
concentrator is designed to rectify the liquids mixture from the
bottoms liquid from the primary feed separator A which comprise
nitrogen, methane, argon and other noble gases. The rectification
can be performed by a variety of techniques, including cryogenic
rectification or adsorptive separation depending upon the
concentration of the argon and other constituents in the bottoms
liquid.
[0021] The rectified argon will leave the concentrator C through
line 5 where it can be directed to storage or to an on-site usage
as necessary. The nitrogen present in the bottoms liquid is also
recovered through line 4 and can be directed to storage or
discharged into the atmosphere.
[0022] While this invention has been described with respect to
particular embodiments thereof, it is apparent that numerous other
forms and modifications of the invention will be obvious to those
skilled in the art. The appended claims in this invention generally
should be construed to cover all such obvious forms and
modifications which are within the true spirit and scope of the
present invention.
* * * * *
References