U.S. patent application number 11/640584 was filed with the patent office on 2008-06-19 for hybrid cycle liquefaction of natural gas with propane pre-cooling.
Invention is credited to Adam Adrian Brostow, Mark Julian Roberts, Christopher Geoffery Spilsbury.
Application Number | 20080141711 11/640584 |
Document ID | / |
Family ID | 39525511 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080141711 |
Kind Code |
A1 |
Roberts; Mark Julian ; et
al. |
June 19, 2008 |
Hybrid cycle liquefaction of natural gas with propane
pre-cooling
Abstract
Natural gas is liquefied in a hybrid liquefaction cycle in which
the gas feed is precooled using vaporizing liquefied refrigerant
gas; liquefied using vaporizing mixed refrigerant comprising
ethylene and at least one other refrigerant selected from
hydrocarbons and halocarbons; and subcooled using a work expanded
pressurized gaseous refrigerant stream. Preferably, the liquefied
refrigerant gas used for precooling is propane, the mixed
refrigerant does not contain ethane or nitrogen and the pressurized
gaseous refrigerant is nitrogen.
Inventors: |
Roberts; Mark Julian;
(Kempton, PA) ; Spilsbury; Christopher Geoffery;
(Haslemere, GB) ; Brostow; Adam Adrian; (Emmaus,
PA) |
Correspondence
Address: |
AIR PRODUCTS AND CHEMICALS, INC.;PATENT DEPARTMENT
7201 HAMILTON BOULEVARD
ALLENTOWN
PA
181951501
US
|
Family ID: |
39525511 |
Appl. No.: |
11/640584 |
Filed: |
December 18, 2006 |
Current U.S.
Class: |
62/611 |
Current CPC
Class: |
F25J 1/0218 20130101;
F25J 1/0072 20130101; F25J 1/0097 20130101; F25J 1/005 20130101;
F25J 1/0217 20130101; F25J 1/0292 20130101; F25J 1/0265 20130101;
F25J 1/0022 20130101; F25J 1/0052 20130101; F25J 1/0087
20130101 |
Class at
Publication: |
62/611 |
International
Class: |
F25J 1/00 20060101
F25J001/00 |
Claims
1. A method of liquefying natural gas which comprises: precooling a
natural gas feed stream to a temperature below ambient temperature
with refrigeration provided by vaporizing a liquefied refrigerant
gas; liquefying the precooled gas stream with refrigeration
provided by vaporizing a mixed refrigerant comprising two or more
refrigerants selected from hydrocarbons and halocarbons; subcooling
the liquefied stream with refrigeration by work expanding a
pressurized gaseous refrigerant stream characterized in that the
mixed hydrocarbon refrigerant comprises ethylene.
2. The method of claim 1, wherein the natural gas feed stream is
precooled to a temperature not below about -40.degree. F.
(-40.degree. C.)
3. The method of claim 2, wherein the natural gas feed stream is
precooled to a temperature not below about -35.degree. F.
(-37.degree. C.)
4. The method of claim 3, wherein the natural gas feed stream is
precooled to a temperature of about -30.degree. F. (-35.degree.
C.)
5. The method of claim 1, wherein the liquefied refrigerant gas
used for the pre-cooling consists of a single component.
6. The method of claim 5, wherein the single component is
propane.
7. The method of claim 1, wherein the mixed refrigerant does not
comprise ethane.
8. The method of claim 1, wherein the mixed refrigerant comprises
ethylene and one or more refrigerants selected from hydrocarbons
and halocarbons
9. The method of claim 8, wherein the mixed refrigerant consists of
ethylene and one or more refrigerants selected from C.sub.1 to
C.sub.5 hydrocarbons.
10. The method of claim 9, wherein the mixed refrigerant does not
comprise ethane.
11. The method of claim 1, wherein the mixed refrigerant comprises
methane, ethylene and propane.
12. The method of claim 11, wherein the mixed refrigerant consist
of methane, ethylene and propane.
13. The method of claim 1, wherein the pressurized gaseous
refrigerant stream is nitrogen.
14. A method of liquefying natural gas which comprises: precooling
a natural gas feed stream to a temperature not below about
-40.degree. F. (-40.degree. C.) with refrigeration provided by
vaporizing a single component liquefied refrigerant gas; liquefying
the precooled gas stream with refrigeration provided by vaporizing
an essentially ethane-free mixed refrigerant comprising methane,
ethylene and propane; and subcooling the liquefied stream with
refrigeration by work expanding a pressurized gaseous nitrogen
stream.
15. The method of claim 14, wherein the natural gas feed stream is
precooled to a temperature of about -30.degree. F. (-35.degree.
C.)
16. The method of claim 14, wherein the liquefied refrigerant gas
used for the pre-cooling is propane.
17. The method of claim 14, wherein the mixed refrigerant consist
of methane, ethylene and propane.
18. A method of liquefying natural gas which comprises: precooling
a natural gas feed stream to a temperature of about -30.degree. F.
(-35.degree. C.) with refrigeration provided by vaporizing propane;
liquefying the precooled gas stream with refrigeration provided by
vaporizing a mixed refrigerant consisting of methane, ethylene and
propane; and subcooling the liquefied stream with refrigeration by
work expanding a pressurized gaseous nitrogen stream.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to the liquefaction of natural
gas (LNG) using a hybrid cycle in which the gas is liquefied using
refrigeration provided by vaporizing a refrigerant stream and the
liquefied gas subcooled using refrigeration provided by work
expanding a pressurized gaseous refrigerant stream. In particular,
the invention provides an improved method of liquefying natural gas
when the gas feed is precooled using refrigeration provided by
vaporizing propane.
[0002] The production of liquefied natural gas (LNG) usually is
achieved by cooling and condensing a feed gas stream against
multiple refrigerant streams provided by recirculating
refrigeration systems. Cooling of the natural gas feed is
accomplished by various cooling process cycles such as the
well-known cascade cycle in which refrigeration is provided by
three different refrigerant loops. One such cascade cycle uses
methane, ethane or ethylene, and propane cycles in sequence to
produce refrigeration at three different temperature levels.
Another well-known refrigeration cycle uses a propane pre-cooled,
mixed refrigerant cycle ("C3MR") in which a mixed refrigerant
mixture generates refrigeration over a selected temperature range.
The mixed refrigerant can contain at least two refrigerants
selected from C.sub.1-C.sub.5 hydrocarbons, such as for example
methane, ethane, ethylene, propane and propylene, and halocarbons,
such as for example chlorinated and/or fluorinated methane and
ethane, and also may contain nitrogen.
[0003] The use of ethylene as a component of a mixed refrigerant
for liquefying natural gas is disclosed in, for example, U.S. Pat.
No. 3,645,106 (published Feb. 29, 1972), GB-A-1314174 (published
Apr. 18, 1973), U.S. Pat. No. 4,229,195 (published Oct. 21, 1980),
U.S. Pat. No. 4,548,629 (published Oct. 22, 1985), U.S. Pat. No.
6,062,041 (published May 16, 2000), U.S. Pat. No. 6,253,574
(published (Jul. 3, 2001), U.S. Pat. No. 6,742,357 (published Jun.
1, 2004), and U.S. Pat. No. 7,086,251 (published Aug. 8, 2006). It
is stated in U.S. Pat. No. 4,548,629 that, from the sole standpoint
of thermodynamic efficiency, ethane is preferred over ethylene.
[0004] Another type of refrigeration process for natural gas
liquefaction involves the use of an expander cycle in which gas,
usually nitrogen, is first compressed and cooled to ambient
conditions with air or water cooling and then is further cooled by
counter-current exchange with cold low-pressure gas. The cooled gas
stream is then work expanded through a turbo-expander to produce a
cold low pressure stream. The cold gas stream is used to cool the
natural gas feed and the high pressure gas stream. The work
produced by expansion can be used to drive a nitrogen booster
compressor connected to the shaft of the expander. In this process,
the cold expanded gas is used to liquefy the natural gas and also
to cool the compressed gas in the same heat exchanger. The cooled
pressurized gas is further cooled in the work expansion step to
provide the cold refrigerant.
[0005] In hybrid cycles for liquefaction of natural gas, the
natural gas feed is liquefied using refrigeration provided by
vaporizing a mixed refrigerant stream and the liquefied gas
subcooled using refrigeration provided by work expanding a
pressurized gaseous refrigerant stream. Such hybrid processes are
described in DE-A-2440215 (published Mar. 4, 1976) and U.S. Pat.
No. 6,308,531 (published Oct. 30, 2001 and the entire contents of
which are incorporated herein by way of this reference). Recently,
such processes have been commercialized under the Trade Mark AP-X
by Air Products & Chemical Inc. In the AP-X.RTM. process, the
natural gas feed can be precooled by a propane cycle and the mixed
refrigerant comprises methane, ethane and propane.
[0006] In the process of DE-A-2440215 the natural gas feed is
precooled by vaporization of the mixed refrigerant stream but in
the some of the exemplified embodiments of U.S. Pat. No. 6,308,531,
the feed is precooled by vaporizing propane. Neither DE-A-2440215
nor U.S. Pat. No. 6,308,531 discloses the use of ethylene in the
mixed refrigerant of a hybrid process.
[0007] There is a need to optimize the mixed composition in the
second refrigerant circuit for the liquefaction step of the
three-circuit hybrid liquefaction cycle which uses propane
refrigeration for precooling, mixed refrigeration for liquefaction,
and expansion of gaseous nitrogen for subcooling. In particular, it
is an object of the present invention to reduce power consumption,
increase production, and/or provide for more even power
distribution between the three circuits allowing better selection
of drivers such as gas turbines. The solution should be applicable
to new LNG plants and for retrofitting and debottlenecking existing
LNG plants.
BRIEF SUMMARY OF THE INVENTION
[0008] It has been found that the aforementioned three-circuit
hybrid liquefaction cycle is improved if the mixed refrigerant
comprises ethylene and at least one other refrigerant selected from
hydrocarbons and halocarbons but, preferably, does not contain
ethane.
[0009] In its broadest aspect, the present invention provides a
method of liquefying natural gas which comprises: [0010] precooling
a natural gas feed stream to a temperature below ambient
temperature with refrigeration provided by vaporizing a liquefied
refrigerant gas; [0011] liquefying the precooled gas stream with
refrigeration provided by vaporizing a mixed refrigerant comprising
two or more refrigerants selected from hydrocarbons and
halocarbons; and [0012] subcooling the liquefied stream with
refrigeration by work expanding a pressurized gaseous refrigerant
stream, characterized in that the mixed refrigerant comprises
ethylene.
[0013] In accordance with a preferred embodiment, the method
comprises:
[0014] precooling the natural gas feed stream to a temperature not
below about -40.degree. F. (-40.degree. C.) with refrigeration
provided by vaporizing a single component liquefied refrigerant
gas; [0015] liquefying the precooled gas stream with refrigeration
provided by vaporizing an essentially ethane-free mixed refrigerant
comprising methane, ethylene and propane; and [0016] subcooling the
liquefied stream with refrigeration by work expanding a pressurized
gaseous nitrogen stream.
[0017] In accordance with the most preferred embodiment, the method
comprises: [0018] precooling a natural gas feed stream to a
temperature of about -30.degree. F. (-35.degree. C.) with
refrigeration provided by vaporizing propane; [0019] liquefying the
precooled gas stream with refrigeration provided by vaporizing a
mixed refrigerant consisting of methane, ethylene and propane; and
[0020] subcooling the liquefied stream with refrigeration by work
expanding a pressurized gaseous nitrogen stream.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0021] FIG. 1 is a simplified, schematic diagram of a three-circuit
hybrid process for liquefying natural gas.
[0022] FIG. 2 is a graph showing the temperature profile of the
liquefier heat exchanger that uses a methane-ethane-propane mixture
as a refrigerant in the second refrigerant circuit of the
three-circuit hybrid of FIG. 1.
[0023] FIG. 3 is a graph showing the temperature profile of the
liquefier heat exchanger that uses a methane-ethylene-propane
mixture as a refrigerant in the second refrigerant circuit of the
three-circuit hybrid of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The present invention relates to the liquefaction of natural
gas (LNG) using a three-circuit hybrid cycle in which the gas is
precooled below ambient temperature using refrigeration provided by
vaporizing a liquefied refrigerant gas, preferably propane; the
precooled gas is liquefied using refrigeration provided by
vaporizing a mixed refrigerant stream and the liquefied gas is
subcooled using refrigeration provided by work expanding a
pressurized gaseous refrigerant stream. The invention resides in
the composition of the mixed refrigerant.
[0025] According to the invention, there is provided a method of
liquefying natural gas which comprises: [0026] precooling a natural
gas feed stream to a temperature below ambient temperature with
refrigeration provided by vaporizing a liquefied refrigerant gas;
[0027] liquefying the precooled gas stream with refrigeration
provided by vaporizing a mixed refrigerant comprising ethylene and
one or more refrigerants selected from hydrocarbons and
halocarbons; and [0028] subcooling the liquefied stream with
refrigeration by work expanding a pressurized gaseous refrigerant
stream.
[0029] Usually, the natural gas feed stream will be precooled to a
temperature not below about -40.degree. F. (-40.degree. C.),
preferably to a temperature not below about -35.degree. F.
(-37.degree. C.) and especially to a temperature of about
-30.degree. F. (-35.degree. C.). The liquefied refrigerant gas can
be any of those known for use in pre-cooling natural gas to such
temperatures but preferably consists of a single component such as
propylene, ethane, a halocarbon or, preferably, propane.
[0030] The mixed refrigerant comprises ethylene and one or more
refrigerants selected from hydrocarbons and halocarbons. Suitable
hydrocarbon refrigerants for use in the invention include methane,
propane, i-butane, butane, and i-pentane. Representative halocarbon
refrigerants include R22 (chlorodifluoromethane), R23
(trifluoromethane), R32 (difluoromethane), R134a
(tetrafluoroethane), and R410a (mixed difluoromethane and
pentafluoroethane). The mixed refrigerant can include nitrogen but,
except when the present invention is applied to an existing
liquefaction plant employing a nitrogen-containing mixed
refrigerant, it is preferred that it consists only of hydrocarbons
and optionally halocarbons. Preferably, the mixed refrigerant will
consist of ethylene and one or more other refrigerants selected
from C.sub.1 to C.sub.5 hydrocarbons. It is highly preferred that
the mixed refrigerant does not comprise ethane and suitably the
mixed refrigerant comprises or consists of methane, ethylene and
propane.
[0031] It is highly preferred that the pressurized gaseous
refrigerant stream is nitrogen although other gases such as argon
could be used.
[0032] In a preferred embodiment, the method of liquefying natural
gas comprises: [0033] precooling the natural gas feed stream to a
temperature not below about -40.degree. F. (-40.degree. C.) with
refrigeration provided by vaporizing a single component liquefied
refrigerant gas; [0034] liquefying the precooled gas stream with
refrigeration provided by vaporizing an essentially ethane-free
mixed refrigerant comprising methane, ethylene and propane; and
[0035] subcooling the liquefied stream with refrigeration by work
expanding a pressurized gaseous nitrogen stream.
[0036] It is particularly preferred that the method of liquefying
natural gas comprises: [0037] precooling a natural gas feed stream
to a temperature of about -30.degree. F. (-35.degree. C.) with
refrigeration provided by vaporizing propane; [0038] liquefying the
precooled gas stream with refrigeration provided by vaporizing a
mixed refrigerant consisting of methane, ethylene and propane; and
[0039] subcooling the liquefied stream with refrigeration by work
expanding a pressurized gaseous nitrogen stream.
[0040] Referring to the embodiment illustrated by the simplified,
schematic diagram on FIG. 1, natural gas (NG) is precooled in heat
exchanger(s) 10, liquefied in liquefier heat exchanger 20, and
subcooled in subcooler heat exchanger 30. The natural gas
liquefaction process comprises three refrigerant circuits. The
first circuit (1) provides precooling. Propane is compressed in
compressor 12, cooled and condensed by air or cooling water in heat
exchanger(s) 14, expanded through valve(s) 16 to different pressure
levels, and evaporated in multi-stream heat exchanger or a series
of kettles shown as heat exchanger(s) 10. Typically, the propane
precools both the natural gas feed and refrigerants in the second
and third circuits (which refrigerant precooling is not shown for
simplicity) to about -30.degree. F. (-35.degree. C.).
[0041] Although in known three-circuit hybrid processes, the first
circuit usually uses a mixed refrigerant of suitable composition,
the use of propane at multiple pressure levels is simpler and at
least as efficient. The efficiency loss in using a mixed
refrigerant is due to the fact that it is typically condensed at
close-to-ambient temperature by heat exchange with air or cooling
water over a range of temperatures and the condenser cooling curves
are relatively far apart.
[0042] The second circuit provides refrigeration for the
liquefaction. It uses a mixed refrigerant that comprises ethylene,
preferably with very little or no ethane. Typical components for
use in the present invention are methane, ethylene, and propane.
The mixed refrigerant is compressed in compressor 24, precooled by
air or water and liquefied by heat exchange with refrigerant in the
first circuit in heat exchanger(s) 24, further cooled in the
liquefier heat exchanger 20, expanded through valve 26 or a
hydraulic turbine, and evaporated in the same liquefier heat
exchanger 20 to provide refrigeration for the condensing natural
gas stream.
[0043] Typical the mixed refrigerant in three-circuit hybrid
processes evaporates at a pressure of 64 psia (0.44 MPa). At this
pressure, the boiling points of methane, ethylene, ethane, and
propane are about -220.degree. F. (-140.degree. C.), -100.degree.
F. (-73.3.degree. C.), -68.degree. F. (-55.5.degree. C.), and
29.degree. F. (-1.7.degree. C.), respectively. In accordance with
an embodiment of the present invention, the mixed refrigerant
consists of methane, ethylene and propane and a comparative
refrigerant consists of methane, ethane and propane. For the
comparative mixture, the boiling point difference between the light
component (methane) and the middle component (ethane) is
152.degree. F. (84.5.degree. C.) and the boiling point difference
between the middle component and the heavy component (propane) is
97.degree. F. (53.8.degree. C.). For the mixture of the invention,
the boiling point difference between the light component (methane)
and the middle component (ethylene) is 120.degree. F. (66.7.degree.
C.) and the boiling point difference between the middle component
and the heavy component (propane) is 129.degree. F. (71.6.degree.
C.). Therefore, unlike the boiling point of ethane, the boiling
point of ethylene is close to the middle of the boiling range
thereby allowing better utilization of all three of the mixed
refrigerant components.
[0044] Usually, the liquefaction step cools the natural gas to a
temperature not below about -190.degree. F. (-125.degree. C.).
Typically the liquefaction step cools the natural gas from a
temperature of about -30.degree. F. (-35.degree. C.), which is the
temperature of evaporating propane in the first circuit, to a
temperature of about -170.degree. F. (-112.degree. C.), which is
towards the middle of the methane-ethylene-propane boiling range.
If the first refrigerant circuit used a mixed refrigerant instead
of propane, the precooling typically would be to a significantly
lower temperature of about -45.degree. F. (-43.degree. C.), and the
benefit of using ethylene in the second circuit is lower. Further,
there is no benefit in using ethylene instead of ethane in the
first (mixed) refrigerant circuit.
[0045] Ethylene does not offer the same advantage over ethane in a
conventional C3MR process. In such processes, the mixed refrigerant
typically contains nitrogen and provides cooling to about
-240.degree. F. (-150.degree. C.). It is partially liquefied and
separated into liquid and vapor. If ethylene is used, it escapes to
the vapor phase and is not as useful as ethane in balancing the
warm end of the heat exchanger.
[0046] The third refrigerant circuit subcools the liquefied natural
gas to a temperature usually not below about -250.degree. F.
(-155.degree. C.). Typical the third refrigerant circuit subcools
the liquefied natural gas from a temperature of about -170.degree.
F. (-112.degree. C.) to a temperature of about -240.degree. F.
(-150.degree. C.). This circuit uses works expansion of gaseous
nitrogen (the reverse-Brayton cycle). Nitrogen is compressed in
compressor 32, precooled in heat exchanger(s) 34, cooled in the
economizer heat exchanger 36, expanded in turbine(s) 38 and warmed
back up in the subcooler heat exchanger 30. Typically, there are
two nitrogen turbines but only one is shown for simplicity. The
reverse-Brayton cycle is at least as efficient as mixed refrigerant
cooling in this temperature range and the equipment is simpler.
[0047] FIG. 2 shows the temperature profile of the liquefier heat
exchanger (24) when using the methane-ethane-propane mixed
refrigerant in the second refrigerant circuit and FIG. 3 shows the
corresponding profile for the methane-ethylene-propane mixture. As
can be seen, the cooling curves are closer together for the
methane-ethylene-propane mixture and hence the process is
thermodynamically more reversible.
EXAMPLE
[0048] A plant as shown in FIG. 1 liquefies 33,000 tonne/day of
natural gas using the propane circuit to precool natural gas to
about -30.degree. F. (-35.degree. C.), the mixed refrigerant ("MR")
circuit to liquefy it and cool it to about -173.degree. F.
(-114.degree. C.), and the nitrogen circuit to subcool it to about
-239.degree. F. (-150.5.degree. C.).
[0049] Run 1:
[0050] The plant was operated using an optimized MR composition
consisting of 45.4% methane, 53.7% ethane, and 0.9% propane on a
molar basis and the results are set forth in Tables 1 and 2. The
propane compressor power is 50.5 MW; the MR compressor power is
124.9 MW and the nitrogen compressor power is 99.5 MW (i.e. 20%
lower than the MR. compressor power). Thus, the total plant power
consumption is 274.9 MW.
[0051] Run 2:
[0052] The MR composition of Run 1 was replaced by an optimized MR
composition consisting of 33.0% methane, 54.6% ethylene, and 12.4%
propane on molar basis and the results also are set forth in Tables
1 and 2. The presence of ethylene allows better utilization of
propane at the warm end. The propane compressor power is 44.1 MW
(i.e. 13% lower than in Run 1). The MR compressor power is 119.4 MW
(i.e. 4.4% lower than in Run 1) and the nitrogen compressor power
is 107.0 MW (i.e. 7.5% higher than in Run 1; 10% lower than the MR
compressor power of Run 2). The total plant power consumption is
270.5 MW (i.e. 1.6% lower than in Run 1). Thus, the overall power
consumption was reduced while the power was shifted from propane
and MR compression to nitrogen compression. The lower power
consumption also means that higher production is possible for equal
power.
[0053] If the same gas turbines of about 116-MW are chosen for both
MR and nitrogen compression, then the power saving from using
ethylene instead of ethane is 2.5%.
[0054] Other embodiments and benefits of the invention will be
apparent to those skilled in the art from a consideration of this
specification or from practice of the invention disclosed herein.
It is intended that this specification be considered as exemplary
only with modifications and variations being within the scope and
spirit of the invention as defined by the following claims.
TABLE-US-00001 TABLE 1 Run 2 (Invention) 1 (Comparative) 2 1 2
(Invention) 1 (Comparative) Feed Feed (Invention) (Comparative) MR
MR Stream (Mole Fraction) (Mole Fraction) LNG (Mole Fraction) LNG
(Mole Fraction) (Mole Fraction) (Mole Fraction) N.sub.2 0.020798
0.020798 0.006615 0.006615 0 0 CO.sub.2 0.0036 0.0036 0 0 0 0
CH.sub.4 0.947405 0.947405 0.966381 0.966381 0.329563 0.454214
C.sub.2H.sub.4 0 0 0 0 0.546465 0 C.sub.2H.sub.6 0.015898 0.015898
0.017509 0.017509 0 0.537237 C.sub.3H.sub.8 0.005299 0.005299
0.005828 0.005828 0.123972 0.008549 i-C.sub.4H.sub.10 0.0011 0.0011
0.001202 0.001202 0 0 n-C.sub.4H.sub.10 0.0018 0.0018 0.001959
0.001959 0 0 i-C.sub.5H.sub.12 0.0007 0.0007 0.000249 0.000249 0 0
n-C.sub.5H.sub.12 0.0005 0.0005 0.000143 0.000143 0 0
C.sub.6H.sub.14 0.0006 0.0006 0.000059 0.000059 0 0 C.sub.7H.sub.16
0.0023 0.0023 0.000057 0.000057 0 0 Total Flow lbmol/h 175733
175733 1159350 159349 149187 160155 (Kgmol/h) 79711.3 79711.3
72279.8 72279.5 67670.1 72645.2 Total Flow lb/h 3020731 3020731
2660367 2660356 3891470 381468 (Kg/h) 1370180.6 1370180.6 1206722.2
1206717.3 1765141.2 173031.2 Temperature .degree. F. 51 51 -260.854
-260.854 48.2 48.2 (.degree. C.) 10.5 10.5 -127.141 -127.141 9.0
9.0 Pressure psi 957.2 957.2 15.2 15.2 893.4 893.4 (kPa) 6600 6600
104.8 104.8 6160 6160
TABLE-US-00002 TABLE 2 Invention Comparative Power 270.48 MW 274.92
MW Power difference 0 MW 4.44 MW Power difference 0.00% 1.64%
C.sub.3H.sub.6 compressor 44.11 MW 50.51 MW MR compressor 119.40 MW
124.89 MW N.sub.2 compressor 106.97 MW 99.53 MW
* * * * *