U.S. patent application number 13/980548 was filed with the patent office on 2013-12-19 for method of recovery of natural gas liquids from natural gas at ngls recovery plants.
The applicant listed for this patent is Jose Lourenco, MacKenzie Millar. Invention is credited to Jose Lourenco, MacKenzie Millar.
Application Number | 20130333416 13/980548 |
Document ID | / |
Family ID | 46514922 |
Filed Date | 2013-12-19 |
United States Patent
Application |
20130333416 |
Kind Code |
A1 |
Lourenco; Jose ; et
al. |
December 19, 2013 |
METHOD OF RECOVERY OF NATURAL GAS LIQUIDS FROM NATURAL GAS AT NGLS
RECOVERY PLANTS
Abstract
A method to recover natural gas liquids from natural gas streams
at NGL recovery plants. The present invention relates to methods
using liquid natural gas (LNG) as an external source of stored cold
energy to reduce the energy and improve the operation of NGL
distillation columns. More particularly, the present invention
provides methods to efficiently and economically achieve higher
recoveries of natural gas liquids at NGL recovery plants.
Inventors: |
Lourenco; Jose; (Edmonton,
CA) ; Millar; MacKenzie; (Edmonton, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lourenco; Jose
Millar; MacKenzie |
Edmonton
Edmonton |
|
CA
CA |
|
|
Family ID: |
46514922 |
Appl. No.: |
13/980548 |
Filed: |
January 18, 2012 |
PCT Filed: |
January 18, 2012 |
PCT NO: |
PCT/CA2012/050030 |
371 Date: |
September 5, 2013 |
Current U.S.
Class: |
62/611 |
Current CPC
Class: |
F25J 2205/30 20130101;
F25J 2200/74 20130101; F25J 3/0238 20130101; F25J 2205/04 20130101;
F25J 2270/904 20130101; B01D 3/4211 20130101; F25J 3/0209 20130101;
F25J 3/0233 20130101; F25J 1/0022 20130101; F25J 3/0214 20130101;
F25J 2200/70 20130101; F25J 2210/62 20130101; F25J 2205/50
20130101; F25J 2200/02 20130101; C10G 5/06 20130101; F25J 2240/02
20130101; C10G 2300/1025 20130101 |
Class at
Publication: |
62/611 |
International
Class: |
F25J 1/00 20060101
F25J001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 18, 2011 |
CA |
2728716 |
Claims
1. A method for recovery of natural gas liquids from natural gas
using the cold energy stored in LNG comprising the step of: The
storage and supply of LNG as an external cooling source to control
the operation and recovery of NGLs in a distillation column.
2. The method as defined in claim 1, providing LNG as a reflux
stream by a temperature control of the overhead gas stream by
mixing of LNG with the rising gas stream in the distillation
column.
3. The method as defined in claim 1, providing LNG to directly mix
with un-distilled expanded, feed gas to allow distillation column
to operate at higher pressures without loss of recovery.
4. The method as defined in claim 1, providing LNG as a stripping
gas for carbon dioxide concentration in NGL product stream.
5. method described in claim 1, providing LNG to cool an overhead
stream to generate a second reflux stream for a dual reflux
distillation column operation.
6. A method for recovery of natural gas liquids from a natural gas
comprising the steps of: positioning a storage vessel for liquid
natural gas (LNG) at a NGL recovery plant facility that has at
least one distillation column for recovering natural gas liquids
(NGLs); adding LNG from the storage vessel by direct mixing to
control the temperature profile in a NGL distillation column, the
temperature in the overhead product of the distillation column
being controlled by controlling addition of LNG as a reflux stream,
the temperature in the expanded feed gas to the distillation column
being controlled by controlling addition of LNG as a tempering gas,
the stripping of carbon dioxide from the NGL product stream being
controlled by controlling the addition of LNG as stripping gas.
7. The NGL recovery plant as defined in claim 6, wherein LNG
provides additional cooling energy to the inlet plant gas feed.
8. NGL recovery plant as defined in claim 6, wherein the use of LNG
as an external cold energy source is used to increase the overall
energy efficiency and recovery of NGLs.
Description
FIELD
[0001] The present invention relates to methods for recovery of
natural gas liquids (NGLs) from methane rich gases using liquid
natural gas (LNG). More particularly, the present invention
provides methods to efficiently and economically achieve higher
recoveries of natural gas liquids at NGL recovery plants.
BACKGROUND
[0002] Natural gas from producing wells contain natural gas liquids
(NGLs) that are commonly recovered. While some of the needed
processing can be accomplished at or near the wellhead (field
processing), the complete processing of natural gas takes place at
gas processing plants, usually located in a natural gas producing
region. In addition to processing done at the wellhead and at
centralized processing plants, some final processing is also
sometimes accomplished at `straddle plants`, These plants are
located on major pipeline systems. Although the natural gas that
arrives at these straddle plants is already of pipeline quality,
there still exists quantities of NGLs, which are recovered at these
straddle plants.
[0003] The straddle plants essentially recover all the propane and
a large fraction of the ethane available from the gas before
distribution to consumers. To remove NGLs, there are three common
processes; Refrigeration, Lean Oil Absorption and Cryogenic.
[0004] The cryogenic processes are generally more economical to
operate and more environmentally friendly, current technology
generally favors the use of cryogenic processes over refrigeration
and oil absorption processes. The first generation cryogenic plants
were able to extract up to 70% of the ethane from the gas,
modifications and improvements to these cryogenic processes
overtime have allowed for much higher ethane recoveries >90%.
This increase in recovery comes with consumption of relatively
large quantities of energy due to their compression requirements.
Prior art has taught that use of lean reflux streams reduce energy
consumption and achieves high ethane recoveries, Moreover, methane
gas has been proven to be a superior stripping gas to control
carbon dioxide concentrations in NGL product. Many patents exist
disclosing improved designs for generation of lean reflux to
recover ethane and heavier components in NGL plants. they typically
involve significant capital expenditures and increased operational
costs. A need exists for an efficient ethane and NGL recovery
process that is capable of achieving very high ethane recoveries at
a lower energy consumption and a lower capital cost when compared
to prior art.
SUMMARY
[0005] The present invention provides a method for recovery of
natural gas liquids from natural gas streams in a NGL recovery
plant. The method involves the use of LNG as a reflux stream, a
feed mixer and a stripping gas in the operation of a LNG recovery
plant. The use of LNG as stored cold energy to control a NGL
distillation column temperature profile and operation, increases
the efficiency and recovery of NGLs in natural gas streams.
Moreover, LNG, primarily methane, is an ideal stripping gas to
control carbon dioxide concentration in the NGL product stream.
[0006] As will hereinafter be further described, the interacting
step can be either direct or indirect. Direct interaction is
achieved by injecting LNG as a liquid reflux to the distillation
column to control overhead temperature, by direct mix with expanded
gas stream to control distillation column pressure and as a
stripping gas for carbon dioxide control in NGL product stream.
Indirect interaction is achieved by, first cooling the distillation
column overhead stream in a heat exchanger and then used as a
reflux in the distillation column. The condensate generated from
overhead stream is used as a second reflux stream for a dual reflux
operation, increasing NGLs recovery.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These and other features will become more apparent from the
following description in which reference is made to the appended
drawings, the drawings are for the purpose of illustration only and
are not intended to be in any way limiting, wherein:
[0008] FIG. 1 is a schematic diagram of a facility equipped with
LNG storage and supply for direct cooling in accordance with the
teachings of the present invention.
[0009] FIG. 2 is a schematic diagram of a facility equipped with
LNG storage and supply for indirect cooling in a heat exchanger to
generate a second reflux stream.
DETAILED DESCRIPTION
[0010] The method will now be described with reference to FIG.
1.
[0011] Referring to FIG. 1, a pressurized natural gas stream 1 is
routed to heat exchanger 2 where the temperature of the feed gas
stream is reduced by indirect heat exchange with counter-current
cool streams 24, 19, 6 and 21. The cooled stream 1 enters feed
separator 3 where it is separated into vapour and liquid phases.
The liquid phase stream 4 is expanded through valve 5 and
pre-heated in heat exchanger 2 prior to introduction into
distillation column 20 through line 6. The gaseous stream 7 is
routed to gas expander 8. The expanded and cooler vapor stream 9,
is mixed with LNG for temperature control and routed through stream
17 into the upper section of distillation column 20. A LNG storage
drum 10, supplies LNG through line 11 to LNG pump 12. The
pressurized LNG stream 13 is routed through temperature control
valve 14 providing the reflux stream to distillation column 20. A
slipstream from the pressurized LNG stream 13 provides temperature
control to stream 9 through temperature control valve 16,
temperature controlled stream 17 enters the upper section of
distillation column 20. The controlled temperature of stream 17 by
addition of LNG enables operation of the distillation column at
higher pressures to compensate for the loss of coolth energy
generated by the expander at higher backpressures. A second
slipstream from pressurized LNG stream 13 provides methane for
carbon dioxide stripping through flow control valve 18, the LNG is
pre-heated in heat exchanger 2 before introduction into the lower
section of the distillation column 20 as a stripping gas. The
distilled stream 21, primarily methane, is pre-heated in heat
exchanger 2 and routed to compressor 22 for distribution and or
recompression through line 23, The liquid fraction stream 24 is
reboiled in heat exchanger 2 and routed back to the bottom section
of distillation column 20, to control NGL product stream 25.
[0012] Referring to FIG. 2, the coolth energy of LNG is used to
first condense the overhead stream of the distillation column
generating a second reflux stream before its use as the primary
reflux stream, allowing for an increase in efficiency in plant
operations. A pressurized natural gas stream 1 is routed to heat
exchanger 2 where the temperature of the feed gas stream is reduced
by indirect heat exchange with counter-current cool streams 28, 18,
6 and 25. The cooled stream 1 enters feed separator) where it is
separated into vapour and liquid phases. The liquid phase stream 4
is expanded through valve 5 and pre-heated in heat exchanger 2
prior to introduction into distillation column 19 through line 6.
The gaseous stream 7 is routed to gas expander 8, the expanded and
cooler vapor stream 9 is routed into the upper section of
distillation column 20. A LNG storage drum 10, supplies LNG through
line 11 to LNG pump 12. The pressurized LNG stream 13 enters heat
exchanger 11 and is routed through temperature control valve 15 as
reflux stream 16 to distillation column 19. A slipstream from
pressurized LNG stream 13 provides methane for carbon dioxide
stripping through flow control valve 17, the LNG is pre-heated in
heat exchanger 2 before introduction into the lower section of the
distillation column 19 as a stripping gas. The distilled stream 20,
primarily methane, is cooled in heat exchanger 14 and discharged
into overhead separator 21. The condensed stream 22 feed reflux
pump 23, the pressurized reflux stream 24 enters distillation
column 19 as a second reflux stream for a dual reflux distillation
column operation. The vapour stream 25 is pre-heated in heat
exchanger 2 and routed to compressor 26 for distribution and or
recompression through line 27. The liquid fraction stream 28 is
reboiled in heat exchanger 2 and routed back to the bottom section
of distillation column 19, to control NGL product stream 29.
[0013] In the preferred method, LNG provides stored cold energy
that improves the operation and efficiency of NGL distillation
columns. The above described method uses this stored cold energy to
condense natural gas liquids from natural gas streams by direct
mixing. This direct mixing provides better heat transfer and
reduces the energy requirements to condense NGLs. It also reduces
the energy required for recompression of gas for distribution.
[0014] In this patent document, the word "comprising" is used in
its non-limiting sense to mean that items the word are included,
but items not specifically mentioned are not excluded. A reference
to an element by the indefinite article "a" does not exclude the
possibility that more than one of the element is present, unless
the context clearly requires that there be one and only one of the
elements.
[0015] The following claims are to be understood to include what is
specifically illustrated and described above, what is conceptually
equivalent, and what can be obviously substituted. Those skilled in
the art will appreciate that various adaptations and modifications
of the described embodiments can be configured without departing,
from the scope of the claims. The illustrated embodiments have been
set forth only as examples and should not be taken as limiting the
invention. It is to be understood that, within the scope of the
following claims, the invention may be practiced other than as
specifically illustrated and described.
* * * * *