U.S. patent application number 13/280700 was filed with the patent office on 2013-04-25 for air compressor powered by differential gas pressure.
This patent application is currently assigned to MIDWEST PRESSURE SYSTEMS, INC.. The applicant listed for this patent is Robert Vogt. Invention is credited to Robert Vogt.
Application Number | 20130101440 13/280700 |
Document ID | / |
Family ID | 48136123 |
Filed Date | 2013-04-25 |
United States Patent
Application |
20130101440 |
Kind Code |
A1 |
Vogt; Robert |
April 25, 2013 |
AIR COMPRESSOR POWERED BY DIFFERENTIAL GAS PRESSURE
Abstract
A gas-driven air compressor system and a method for using it. No
electricity, lubrication or cooling water is required. A high
pressure gas used to drive the compressor may be recovered at a
pressure high enough to be retain its economic value. In one
preferred embodiment, the air compressor includes a gas-driven
drive cylinder and an air-driven boost cylinder, interconnected by
reciprocating drive and boost pistons. The drive piston supplies
force to power the boost piston, which pulls in atmospheric air and
discharges it at a higher pressure for use by
pneumatically-operated controls and equipment. A four-way valve
operating on differential gas pressure may be used to automatically
actuate the reciprocating piston. Using the present invention,
fugitive gas emissions, such as normally occur when using a
separator to remove oil and water from a wellhead gas stream, may
be avoided.
Inventors: |
Vogt; Robert; (Elmhurst,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Vogt; Robert |
Elmhurst |
IL |
US |
|
|
Assignee: |
MIDWEST PRESSURE SYSTEMS,
INC.
Bensenville
IL
|
Family ID: |
48136123 |
Appl. No.: |
13/280700 |
Filed: |
October 25, 2011 |
Current U.S.
Class: |
417/53 ;
417/399 |
Current CPC
Class: |
F04B 9/133 20130101 |
Class at
Publication: |
417/53 ;
417/399 |
International
Class: |
F04B 17/00 20060101
F04B017/00 |
Claims
1. A gas-driven air compressor, comprising: a gas drive cylinder
and an air compression cylinder interconnected by reciprocating gas
drive and air compression pistons; the drive piston supplying force
powered by a first gas stream at a first pressure within the drive
cylinder which exhausts to a second gas stream at a second pressure
lower than the first pressure; and the air compression piston
moving under the force supplied by the drive piston, which movement
induces air at atmospheric pressure to flow into the air
compression cylinder and boosts the pressure of the air in the air
compression cylinder to a higher pressure than atmospheric
pressure.
2. The air compressor of claim 1, further comprising a four-way
valve actuating the reciprocating piston, the four-way valve
operating on differential gas pressure.
3. The air compressor of claim 2, wherein movement of the four-way
valve is actuated by gas pilot pressure applied on each side of the
valve.
4. The air compressor of claim 2, wherein movement of the four-way
valve is actuated by gas pilot pressure applied on one side of the
valve.
5. The air compressor of claim 4, wherein venting of the gas pilot
pressure results in a spring actuating a side opposing the one side
of the valve.
6. The air compressor of claim 2, wherein movement of the four-way
valve is actuated by gas pilot pressure applied to a first valve
piston on one side of the valve.
7. The air compressor of claim 6, wherein venting of the gas pilot
pressure results in supply pressure actuating the valve by acting
on a second valve piston on a side opposing the one side of the
valve, wherein the second valve piston is smaller than the first
valve piston.
8. The air compressor of claim 3, wherein a return movement of the
valve is actuated by venting the gas pilot pressure to a low
pressure gas line.
9. The air compressor of claim 4, wherein a return movement of the
valve is actuated by venting the gas pilot pressure to a low gas
pressure line.
10. The air compressor of claim 6, wherein a return movement of the
valve is actuated by venting the gas pilot pressure to a low gas
pressure line.
11. The air compressor of claim 1, further comprising a
mechanically-actuated four-way valve actuating the reciprocating
gas drive piston.
12. The air compressor of claim 1, wherein the air compressor
operates without the need for electricity, lubrication or cooling
water.
13. The air compressor of claim 1, wherein the air compression
piston pulls air at atmospheric pressure into the air compression
cylinder through an inlet check valve on a forward stroke of the
air compression piston, and pushes air at an elevated pressure
above atmospheric pressure out of the air compression cylinder
through a discharge check valve on a reverse stroke of the air
compression piston.
14. The air compressor of claim 1, wherein the air compression
piston pulls air at atmospheric pressure into the air compression
cylinder through an inlet check valve on one side of the cylinder,
while simultaneously pushing air at an elevated pressure above
atmostpheric pressure out of the air compression cylinder on the
other side of the piston through a discharge check valve on a
forward stroke of the air compression piston, and repeats the
process on a reverse stroke of the air compression piston.
15. The air compressor of claim 1, wherein the first gas stream
originates from a well head, and wherein the compressed air
supplied from the air compressor is used to operate controls of a
separator used to remove oil and water from the first gas
stream.
16. A method for using a gas-driven air compressor having a gas
drive cylinder and an air compression cylinder interconnected by
reciprocating gas drive and air compression pistons, comprising the
steps of moving the drive piston using a first gas stream at a
first pressure within the drive cylinder which exhausts to a second
gas stream at a second pressure lower than the first pressure; and
the air compression piston moving under the force supplied by the
drive piston, which movement induces air at atmospheric pressure to
flow into the air compression cylinder, thereby boosting air within
the air compression cylinder to a higher pressure than atmospheric
pressure.
17. The method of claim 16, wherein the first gas stream originates
from a well head, and further comprising the step of using the
compressed air supplied from the air compressor to operate controls
of a separator used to remove oil and water from the first gas
stream.
18. The method of claim 16, wherein a four-way valve is provided in
fluid communication with the reciprocating gas drive piston, and
further comprising the step of actuating movement of the four-way
valve using differential gas pressure between the first and second
gas streams.
19. The method of claim 18, further comprising the step of
actuating movement of the four-way valve using gas pilot pressure
applied on at least one side of the valve.
20. The method of claim 16, further comprising the step of the air
compression piston pulling air at atmospheric pressure into the air
compression cylinder through an inlet check valve on a forward
stroke of the air compression piston, and the air compression
piston pushing air at an elevated pressure above atmospheric
pressure out of the air compression cylinder through a discharge
check valve on a reverse stroke of the air compression piston.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to gas-driven air compressors.
More specifically, the present invention relates to methods and
systems for compressing air using energy available in a high
pressure gas stream, while exhausting the drive gas to a lower
pressure gas stream and still retaining the commercial value of the
gas.
[0002] There is a need for using gas-driven air compressors in
applications such as oil and gas wells. In many cases, particularly
in remote, rural areas, no electricity may be available, and all
equipment may be run off of natural gas. Available gas pressures
can be substantial (e.g., 200-1000 psi). In a gas well, for
example, gas from the well enters a separator to remove oil and
water. The gas is filtered and transported to a "sales line," which
collects gas and transports it to a natural gas processing
facility. Sales line pressure may be in the 100-250 psi range. The
controls which operate the separator are run off of natural gas,
which is vented to the atmosphere. It would be advantageous to
develop a system for eliminating the fugitive gas emissions from
the separator controls by operating the controls on compressed air.
If the air compressor was driven by the differential pressure that
exists between the well head and the sales line, there would be no
energy cost. If the discharge from the gas drive is fed into the
sales line, there would be no pollutant emissions associated with
the gas-driven air compressor and no loss of revenue.
[0003] These fugitive emissions of volatile organic compounds are a
safety and environmental hazard. In Colorado, for example,
environmental standards were implemented in December of 2006 in an
effort to reduce volatile organic compound emissions which create
ozone and negatively affect air quality. These standards were made
more stringent after May of 2008 to help reduce the high levels of
ozone concentrations in the area and to keep Colorado in compliance
with national air standards.
[0004] By way of backround, air compressors typically include a
drive system which provides the energy required to operate the air
compression system, and an air compression system which elevates
air pressure. The drive systems may include: a crankcase driven by
an electric motor or an engine; a turbine drive; and a hydraulic
piston driven by an electric motor or an engine.
[0005] As further backround, the air compression system may
include: a reciprocating piston (providing moderate compression
ratios and flowrates, suitability for high operating pressures, low
to moderate cost, a compact design, rod seal leakage and vibration,
and a moderate operating life for the seals, especially
non-lubricated seals); a turbine (providing high flowrates, low
vibration, a long operating life, suitability for high pressures,
low compression ratios, high cost, shaft seal leakage, and a large
size); a diaphragm (providing high compression ratios, no seal
leakage, suitability for high pressures, very low flow, high cost,
vibration, and a low operating life); a bellows (providing no seal
leakage, moderate cost, low flow, low compression ratios,
vibration, and a lack of suitability for high pressures); a rotary
vane (providing high flowrates, low cost, low compression ratios, a
lack of suitability for high pressures, and a low operating life);
a fan (providing high flowrates, low cost, very low compression
ratios, and a lack of suitability for high pressures); a "roots
type" blower (providing high flowrates, moderate cost, long life,
low compression ratios, shaft leakage, and a lack of suitability
for high pressures); and a rotary screw (providing high flowrates,
moderate cost, long life, moderate compression ratios, shaft
leakage, and a lack of suitability for high pressures).
[0006] With low flowrates and moderate compression ratios, which
are the focus of the preferred embodiment described below, the most
practical air compression system utilizes a reciprocating piston.
Most existing piston air compressors utilize crankcase drives. For
many applications, such as pneumatic controls on natural gas or oil
production equipment, electricity is either not available, or not
available in sufficient quantities to drive an air compressor. Gas
or oil-fueled engine compressor drives are impractical due to first
cost, maintenance costs, fuel costs and pollutant emissions.
Accordingly, compact air compressors powered by a gas-driven
reciprocating piston may be a good engineering fit in such
applications which have high pressure gas (instead of compressed
air) available to drive the booster.
[0007] Gas-driven compressors, also called gas boosters, booster
compressors and air amplifiers, that utilize compressed gas (or
compressed air) as the motive force to boost air pressure, are
known. They are typically used to boost shop air pressure for
applications which require higher pressures than the utility air
pressure available. Gas-driven compressors have various advantages:
the pressure boost in such devices can be as low as 5 psi or as
high as thousands of psi; they require no electricity, cooling
water or lubrication; and they are explosion-proof, compact, easy
to install and economical. Such advantages may be important in
applications located in remote areas where electricity may not be
available (e.g., oil and gas wells). Gas-driven compressors are
available, for example, from Midwest Pressure Systems, Inc. of
Bensenville, Ill.
[0008] With existing gas-driven compressors, the air compression
section includes a single-acting or double-acting cylinder with
inlet and discharge check valves for each pumping chamber. There
are variations in check valve, piston and rod seal designs, and
materials, but all of the existing systems are similar in
engineering design.
[0009] The drive section of the boosters may have several
variations, but generally consist of a four-way valve which causes
the drive piston to reciprocate automatically. The differences are
in the manner used to actuate the valve:
[0010] 1. Mechanical actuation causes the four-way valve to shift
as a result of the drive piston mechanically moving the valve
element at the end of stroke.
[0011] 2. Pilot shifting actuates the four-way valve through a
small amount of pressurized air or gas which forces a piston
attached to the valve to move, causing the valve to shift. There
are three versions of this design. A first version uses a four-way
valve with a double-pilot design which receives a pilot signal at
each end of the valve. With this first version, pilot valves are
triggered by the piston at the end of each stroke. Each pilot valve
sends a pilot air or gas signal to the four-way valve, causing it
to shift. After the four-way valve shifts, the pilot air or gas is
vented. The second version uses the same two pilot valves, but one
valve sends a pilot signal to the pilot side of a single-pilot,
spring-return, four-way valve. The pilot air or gas shifts the
four-way valve against the spring and remains trapped in the pilot
section until the other pilot valve is tripped, venting the air or
gas in the pilot section. With this second version, the spring then
shifts the four-way valve back to the original position. The third
version is similar to the second version. Pilot air or gas actuates
a larger pilot piston on one side of the four-way valve and holds
it in place. The piston on the other side of the four-way valve is
smaller, and is always charged with supply air or gas. When pilot
air or gas is vented from the first piston, the smaller piston
shifts the four-way valve back to its original position.
[0012] 3. Existing gas-driven compressor designs vent the drive gas
to air atmosphere. The pilot air or gas also vents to atmosphere.
The drive force is determined by the pressure of the drive air or
gas above atmospheric pressure. The flow capability is a function
of this drive force as well as the amount of drive air or gas that
is available. Typically, the maximum pressure rating of gas booster
drive systems is 10 barg or 150 psig, which encompasses the shop
air pressure available in most industrial applications.
[0013] Rod seal design and materials, piston seal design and
materials, and structural materials vary in the pneumatic drive
section, but the various models are similar in engineering
design.
[0014] Accordingly, there is a need for a system and method for
eliminating the fugitive gas emissions from gas-operated controls
and equipment (such as but not limited to well separators) by
operating the gas-operated controls and equipment on compressed
air. It would be advantageous to drive the air compressor using
differential gas pressure (such as but not limited to that
differential gas pressure that exists between a well head and the
sales line), in which case there would be no additional energy
cost. It would also be advantageous to feed the discharge from the
gas drive into the sales line, so that there would be no pollutant
emissions associated with the gas-driven air compressor, and no
loss of revenue.
Definition of Claim Terms
[0015] The terms used in the claims of the patent as filed are
intended to have their broadest meaning consistent with the
requirements of law. Where alternative meanings are possible, the
broadest meaning is intended. All words used in the claims are
intended to be used in the normal, customary usage of grammar and
the English language.
[0016] "Atmospheric pressure" means the pressure exerted by the
atmosphere. This pressure is 14.7 psia (absolute pressure) at sea
level or 0 psig (gauge pressure). Atmospheric pressure falls as
elevation increases. For example, atmospheric pressure in Denver,
Colorado at 5280 feet elevation is approximately 12.1 psia asolute
pressure and 0 psig gauge pressure.
[0017] "Compression ratio" means the ratio of the increased
pressure of the air over atmospheric pressure.
SUMMARY OF THE INVENTION
[0018] The objects mentioned above, as well as other objects, are
solved by the present invention, which overcomes disadvantages of
prior gas delivery and air compression systems and methods, while
providing new advantages not believed associated with such systems
and methods.
[0019] In a preferred embodiment of the invention, a gas-driven air
compressor is provided, and includes a drive cylinder and an air
compression cylinder interconnected by reciprocating drive and
compressor pistons. Initially, the drive cylinder may be filled
with drive gas at a first gas pressure, moving the drive gas piston
through a full stroke based on the length of the cylinder. At the
end of the stroke, drive gas may be vented at a second gas pressure
which is lower than the first gas pressure. The drive gas piston is
connected to the air compressor piston, so that they work in
tandem. During a piston stroke, one side of the compressor cylinder
may be charged through an inlet check valve with air at atmospheric
pressure. The other side of the compressor cylinder may be used to
compress air to an elevated pressure, and discharge the air through
a check valve to a storage tank or to pneumatically-operated
equipment.
[0020] In a particularly preferred embodiment, a four-way valve
operating on differential gas pressure may be used to actuate the
reciprocating pistons. The four-way valve may be actuated in
various ways. For example, it may be actuated using gas pilot
pressure, or a mechanical actuation, applied on each side of the
valve. As another example, the four-way valve may be actuated by
pilot pressure applied on one side of the valve; when this pressure
is vented, a spring may be used to actuate the other side of the
valve. As a further example, the four-way valve may be actuated by
pilot pressure applied to a valve piston acting on one side of the
valve; when this pilot pressure is vented, supply pressure acting
on a smaller valve piston on the other side of the valve may be
used to actuate the valve. In each case, return of the valve may be
actuated by venting the pilot pressure to a low gas pressure
line.
[0021] The gas pressure booster may be operated without the need
for electricity, lubrication or cooling water.
[0022] In a particularly preferred embodiment, the first gas stream
may originate from a well head, and the compressed air supplied
from the air compressor may be used to operate pneumatic controls
for (e.g.) a separator used to remove oil and water from the first
gas stream.
[0023] In another embodiment of the invention, a method is
disclosed for using a gas-driven air compressor having a gas drive
cylinder and an air compression cylinder interconnected by
reciprocating gas drive and air compression pistons. Using the
first gas stream on one side of the drive gas cylinder, the drive
piston is moved within the drive cylinder, exhausting a second gas
stream on the other side of the drive gas cylinder at a lower
pressure. The air compression piston moves under the force supplied
by the drive piston, inducing air at atmospheric pressure to flow
into one side of the air compression cylinder, thereby boosting air
in the other side of the air compression cylinder to a higher
pressure than atmospheric pressure. In one method example, the
first gas stream can originate from a well head, the second gas
stream may be fed to the "sales line," and compressed air may be
supplied from the air compressor and used to operate the pneumatic
controls of a separator for removing oil and water from the first
gas stream. The four-way valve may be used in the method claim in
various ways in a similar manner to how it is used in the system
claim.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The novel features which are characteristic of the invention
are set forth in the appended claims. The invention itself,
however, together with further objects and attendant advantages
thereof, can be better understood by reference to the following
description taken in connection with the accompanying drawings, in
which:
[0025] FIGS. 1-4 are progressive, illustrative schematic views
showing air compressor stages 1-4 (corresponding to FIGS. 1-4) for
a gas-driven air compressor system according to a preferred
embodiment of the present invention.
[0026] The components in the drawings are not necessarily to scale,
emphasis instead being placed upon clearly illustrating the
principles of the present invention. In the drawings, like
reference numerals designate corresponding parts throughout the
several views.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] Set forth below is a description of what are believed to be
the preferred embodiments and/or best examples of the invention
claimed. Future and present alternatives and modifications to this
preferred embodiment are contemplated. Any alternatives or
modifications which make insubstantial changes in function, in
purpose, in structure, or in result are intended to be covered by
the claims of this patent.
[0028] FIGS. 1-4 show progressive schematic views of a preferred
embodiment of a gas-driven air compressor system of the present
invention, generally referred to by the reference numeral 10.
Referring to the figures, air compressor system 10 includes a high
pressure, gas-driven drive cylinder 20 and an air compression
cylinder 30. High pressure gas emanates from a source 60, while low
pressure gas flows to sink 80. Drive cylinder 20 and air
compression cylinder 30 share a common piston rod 40, so that drive
piston 23 and air compressor piston 33 move in tandem. Four-way
valve 50 is in fluid communication with the front and back sides of
drive cylinder 20, as well as with high pressure gas source 60 and
low pressure gas sink 80, and the four-way valve moves in the
manner described below.
[0029] Referring now to FIG. 1, stage 1 of the air compressor
system's operation will be described. The direction of the stroke
of piston rod 40 is shown by the arrow located above drive piston
23 (i.e., the piston rod is moving right-to-left). In the middle of
a forward stroke, high pressure gas from source 60 (e.g., from the
wellhead and regulated to a pressure level above the sales line
pressure, which may be in the, e.g., 100-750 psi range in this
application) flows through line 75, which fills chamber 21 and
pushes drive piston 23, piston rod 40 and air compression piston 33
in the direction of stroke shown. Air compression piston 33 induces
a vacuum in chamber 31, closing check valve 36, and causing
atmospheric air from line 70 to flow through check valve 34 and
fill chamber 31. Concurrently, air compression piston 33 pushes air
from chamber 32, which closes check valve 35 and exits through
check valve 37 at elevated pressure through line 72. Low pressure
gas at the sink pressure also exits chamber 22 of drive cylinder 20
through line 74, moving through 4-way valve 50 and to low pressure
sink 80.
[0030] Referring now to FIG. 2, the second stage occurs when drive
piston 22 reaches the end of its forward stroke. At this point, all
of the air has been pushed out of the chamber 32 of the air
compression cylinder 30 through check valve 37 and line 72, and
chamber 31 of the air compression cylinder is fully charged with
air at near-atmospheric pressure. Drive cylinder chamber 21 is
fully charged with high-pressure gas. Now, the drive piston
triggers a pilot valve (not shown), which shifts four-way valve 50,
leading to the third stage shown in FIG. 3.
[0031] Referring now to FIG. 3, in the third stage of the air
compressor system's operation, 4-way valve 50 shifts to the right.
After this shift occurs, high pressure gas from the chamber 21 of
the drive cylinder flows through line 75, the four-way valve, line
76, and into low pressure sink 80. Air from chamber 31 of the air
compression cylinder is at near-atmospheric pressure. High pressure
gas starts flowing from source 60, through the 4-way valve, through
line 74, and into chamber 22 of the drive cylinder, initiating the
reverse stroke of the drive piston 23, piston rod 40 and air
compression piston 32.
[0032] Referring now to FIG. 4, which shows the fourth and final
stage of the air compressor system's operation, in the middle of a
reverse stroke. High pressure gas from line 74 pushes drive piston
23, piston rod 40 and air compression piston 33 left-to-right in
the direction of the arrow. The remaining gas in chamber 21 is
pushed out through line 75, four-way valve 50 and line 76 to low
pressure sink 80. Atmospheric air is sucked into chamber 32 of air
compression cylinder 30 through line 82 and check valve 35. Low
pressure in chamber 32 closes check valve 37. Concurrently,
compressed air exits the back-side chamber 31 of air compression
cylinder 30, through check valve 36 and line 83. High pressure in
chamber 31 causes check valve 34 to close. When drive piston 23
reaches the end of the reverse stroke, it triggers a pilot valve
(not shown) which again switches the four-way valve 50, iniating a
new forward stroke for the piston rod.
[0033] Those of ordinary skill in the art will appreciate that the
gas-driven air compressor of the present invention may be
advantageously employed to supply compressed air from an available
high pressure gas source, and that it may be used in a variety of
devices and systems, including but not limited to oil or gas
wells.
[0034] The above description is not intended to limit the meaning
of the words used in the following claims that define the
invention. Persons of ordinary skill in the art will understand
that a variety of other designs still falling within the scope of
the following claims may be envisioned and used. It is contemplated
that future modifications in structure, function, or result will
exist that are not substantial changes and that all such
insubstantial changes in what is claimed are intended to be covered
by the claims.
* * * * *