U.S. patent application number 10/598739 was filed with the patent office on 2007-08-02 for method of power generation from pressure control stations of a natural gas distribution system.
This patent application is currently assigned to TRI GAS & OIL TRADE SA. Invention is credited to Jose Lourenco.
Application Number | 20070177969 10/598739 |
Document ID | / |
Family ID | 34916939 |
Filed Date | 2007-08-02 |
United States Patent
Application |
20070177969 |
Kind Code |
A1 |
Lourenco; Jose |
August 2, 2007 |
Method of power generation from pressure control stations of a
natural gas distribution system
Abstract
A method is described of generating power from a pressure
control station of a natural gas distribution system. A first step
involves channeling natural gas entering the pressure control
station into a turbine (52) which is powered by expansion of the
natural gas as the pressure of the natural gas is reduced. A second
step involves capturing the output of the turbine (52) for useful
purposes.
Inventors: |
Lourenco; Jose; (Toronto,
CA) |
Correspondence
Address: |
CHRISTENSEN, O'CONNOR, JOHNSON, KINDNESS, PLLC
1420 FIFTH AVENUE
SUITE 2800
SEATTLE
WA
98101-2347
US
|
Assignee: |
TRI GAS & OIL TRADE SA
9, rue Massot
Geneva
CH
|
Family ID: |
34916939 |
Appl. No.: |
10/598739 |
Filed: |
March 9, 2005 |
PCT Filed: |
March 9, 2005 |
PCT NO: |
PCT/CA05/00359 |
371 Date: |
September 8, 2006 |
Current U.S.
Class: |
415/1 |
Current CPC
Class: |
F01K 25/10 20130101 |
Class at
Publication: |
415/001 |
International
Class: |
F04D 27/02 20060101
F04D027/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 9, 2004 |
CA |
2461086 |
Claims
1. A method of generating power from a pressure control station of
a natural gas distribution system, comprising the steps of:
channeling natural gas entering the pressure control station into a
turbine (52) which is powered by expansion of the natural gas as
the pressure of the natural gas is reduced; and capturing the
output of the turbine (52) for application for useful purposes.
2. The method as defined in claim 1, the natural gas not being
pre-heated prior to being channeled into the turbine (52), with a
view to intentionally generating cold temperatures, a heat
exchanger (56) being provided to utilize the cold temperatures
generated for one of refrigeration or air conditioning.
3. The method as defined in claim 1, the turbine (52) being used to
power an electrical generator (54).
4. The method as defined in claim 1, using a portion of the natural
gas to power a gas fueled turbine power generator (58), passing the
exhaust gases from the gas fueled turbine power generator (58)
through a second heat exchanger (66) to preheat the natural gas
being channeled into the turbine (52) and capturing the output of
the gas fueled turbine power generator (58) for application for
useful purposes.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to method of generating power
from pressure control stations of a natural gas distribution
system.
BACKGROUND OF THE INVENTION
[0002] Natural gas distribution systems use three types of natural
gas pipeline networks:
[0003] high pressure (approximately 1,000 psig), medium pressure
(approximately 100 psig) and low pressure (approximately 5 psig).
Where the high pressure pipeline network feeds into the medium
pressure pipeline network, the pressure must be reduced from 1000
psig to 100 psig. Where the medium pressure pipeline network feeds
into the low pressure pipeline network, the pressure must be
reduced from 100 psig to 5 psig. This is done through a series of
pressure reducing control valves at facilities known as Pressure
Control Stations.
[0004] As the pressure of natural gas is reduced, it expands. As
the natural gas expands, the temperature of the natural gas
decreases. This dramatic drop in temperature leads to the formation
of hydrates, which damage the pressure reducing control valves. In
order to avoid the formation of hydrates, the natural gas is
pre-heated at the Pressure Control Stations before pressure is
reduced, with a view to maintaining an outlet temperature of 5
degrees Celsius. The mode of preheating the natural gas upstream of
the pressure control valves is by consuming some of the natural gas
in a hot water or low pressure steam boiler, which supplies heat to
a heat exchanger. The heat exchanger is then used to preheat the
incoming natural gas.
[0005] In this typical mode of pipeline pressure control
arrangement, the energy lost across the pressure reducing control
valves in bringing the pressure down from 1000 psig to 100 psig is
significant. Similarly, there is energy lost across the pressure
reducing control valves in bringing the pressure down from 100 psig
to 5 psig. If this energy could be captured, there potentially
could be a net energy gain, as opposed to a net energy loss
realized from the Pressure Control Stations.
SUMMARY OF THE INVENTION
[0006] What is required is a method of generating power from
pressure control stations of a natural gas distribution system.
[0007] According to the present invention there is provided a
method of generating power from a pressure control station of a
natural gas distribution system. A first step involves channeling
natural gas entering the pressure control station into a turbine
which is powered by expansion of the natural gas as the pressure of
the natural gas is reduced. A second step involves capturing the
output of the turbine for application for useful purposes.
[0008] The method described above utilizes energy that is presently
lost across the stem of the pressure control valves and utilizes it
in a form of turbine which is powered by expanding gases, commonly
known as a Turbo-expander.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] These and other features of the invention 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 in any way limit the
scope of the invention to the particular embodiment or embodiments
shown, wherein:
[0010] FIG. 1 labelled as PRIOR ART is a schematic diagram of a
Pressure Control Station.
[0011] FIG. 2 is a schematic diagram of a Pressure Control Station
constructed in accordance with the teachings of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0012] The preferred method of generating power from a pressure
control station of a natural gas distribution system will now be
described with reference to FIGS. 1 and 2.
[0013] In order to place the present method in context, the PRIOR
ART system will first be described. Referring to FIG. 1, a high
pressure pipeline network is indicated by reference numeral 12 and
a low pressure pipeline network is indicated by reference numeral
14. Interposed between high pressure pipeline network 12 and low
pressure pipeline network 14 is a Pressure Control Station
generally indicated by reference numeral 16. High pressure natural
gas flowing from high pressure pipeline network 12 passes through a
first line shut off valve 18, a course control valve assembly,
generally indicated by reference numeral 20, a fine control valve
assembly 22, before encountering a second line shut off valve 24. A
boiler 26 with an associated heat exchanger 28 is positioned on a
diversion loop 30. Three valves 32 are provided which control the
feed of natural gas into and out of heat exchanger 28. Natural gas
is pre-heated in heat exchanger 28. The pre-heated natural gas is
then directed through a series of pressure reducing control valves
34. A third line shut off valve 36 enables Pressure Control Station
16 to be isolated from low pressure pipeline network 14. A fuel gas
supply conduit 38 diverts some of the processed low pressure
natural gas for use in fueling boiler 26. The principle of
operation is to preheat the natural gas in heat exchanger 28 to
avoid the production of hydrates when the natural gas passes
through the series of pressure reducing control valves 34. The
energy generated as the pressure of the natural gas is produced is
lost at pressure reducing control valves 34. In addition, energy
input is needed in the form of gas consumption to power boiler 26.
There is, therefore, a net energy loss.
[0014] Referring to FIG. 2, a configuration in accordance with the
present method is illustrated as being super-imposed upon the PRIOR
ART Pressure Control Station of FIG. 1. It is envisaged that the
existing infrastructure will be kept in place to maintain redundant
systems for reasons of public safety.
[0015] In accordance with the teachings of the present method,
natural gas is diverted by passing heat exchanger 28 and series of
pressure reducing control valves 34. A key aspect of the present
method is channeling natural gas entering Pressure Control Station
along line 50 and into a turbine 52 which is powered by expansion
of the natural gas as the pressure of the natural gas is reduced.
The output of turbine 52 is then captured for application for
useful purposes. It is preferred that the turbine be used to power
an electrical generator 54. The use of turbine 52 can be done
either with or without the natural gas being pre-heated, as will
hereinafter be further described.
[0016] Turbine 52 is preferably a turbine known as a
"turbo-expander". It is a radial inflow turbine with variable inlet
guide vanes for flow control, which are used to extract energy from
a gas stream. The method uses the turbo-expander (turbine 52) to
generate power in Pressure Control Stations 16 in a natural gas
distribution system. The expansion across the inlet guide vanes and
expander wheel produces torque and therefore shaft power that can
be used to turn power generator 54.
[0017] Where the natural gas specifications of the working stream
permit, turbine 52 can be used without preheating the natural gas.
The natural gas is channeled into turbine 52, with a view to
intentionally generating cold temperatures. A heat exchanger 56 is
provided to capture the cold temperatures generated for use in
either refrigeration or air conditioning. A fluid circulation can
then be provided through heat exchanger 56 which can be used for
air conditioning of nearby facilities or refrigeration of nearby
cold storage warehouses. The refrigeration achieved by expansion of
the gas is usually much more than achieved by Joule-Thompson (J-T)
expansion across a valve.
[0018] Where preheating of the natural gas is required, boiler 26
replaced by a gas fueled turbine power generator 58, sometimes
referred to as a "micro-turbine". A portion of the high pressure
natural gas is diverted along conduit 60 and passed through a gas
conditioning system 62 to condition the natural gas so that the
natural gas is suitable to power gas fueled turbine power generator
58. Exhaust gases from gas fueled turbine power generator flow
along conduit 64 and are passed through a first heat exchanger 66.
A hot water circulation circuit is provided which includes
expansion tank circulation conduit 68, expansion tank 70, a pump 74
and valves 76. Expansion tank 70 provides make up water for
circulation conduit 68, as required. Pump 74 is used to circulate
hot water through circulation conduit 68. Water is circulated
through conduit 68, which passes heat exchanger 66, so that a heat
transfer takes place with the hot exhaust gases from gas fueled
turbine power generator 58 and heating the water. The exhaust gases
are then released to atmosphere. A secondary heat exchange then
takes place in a second heat exchanger 78 between the hot water and
the natural gas. The natural gas, which has been preheated in
second heat exchanger 78 is then channeled through line 50 to
turbine 52. The output of gas fueled turbine power generator 58 is
also captured for useful purposes of power generation through
generator portion 54. The intent of the method is to capture and
use energy that is currently being wasted. Depending upon the
circumstances, it may be desirable to position a dehydrator
upstream of second heat exchanger 78, to dry the natural gas.
Suitable dehydrators which use absorbent medium are well known in
the art. Normally two are used. One is always in service, while the
absorbent medium in the other is being regenerated. Of course,
where the objective is to generate low temperatures for the purpose
of air conditioning or refrigeration, the hot water circulation
circuit will not be used.
[0019] In this patent document, the word "comprising" is used in
its non-limiting sense to mean that items following 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.
[0020] It will be apparent to one skilled in the art that
modifications may be made to the illustrated embodiment without
departing from the spirit and scope of the invention as hereinafter
defined in the Claims.
* * * * *