Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1
INTRODUCTION
The invention relates to a system and method used to gather volumes of gases
normally
vented to atmosphere and utilizing a gas over gas ejector component, under
specific operating
conditions, introduce the combined vent and motive gas volumes into the fuel
gas supply of a
natural gas fuelled engine. The invention incorporates vent gas high pressure
relief, fail open
safeties and low pressure make-up (recycle) devices. Discharge pressure high
pressure relief and
back pressure control valves and fail closed shut off valve(s). Motive gas
flow valve(s) are of fail
closed configuration. System configurable control points will provide control
valve operation by
utilizing pressure sensing switches or transmitters. A customer inter-connect
to support equipment
and facility initiated fuel gas shut off is also provisioned.
BACKGROUND OF THE INVENTION
The detrimental effect of green house producing gases such as methane is of
practical
concern. Hydrocarbon vapours may be routinely vented to the atmosphere in the
course of energy
production activities. Efforts to eliminate or mitigate the release of vented
or fugitive natural gas
volumes are broad-ranging and encouraged by various levels of government and
regulatory
overseers. Several methods to control large volumes of vented production gas
are in common
practice today, the inventive system and method presented herein is intended
to minimize the
venting of smaller volumes or routinely vented in the course of natural gas
gathering, compression
and transmission.
Particularly useful in the upstream and midstream segments of oil and gas
production ¨
where the activity of natural gas production at various pressure values is
prevalent ¨the invention
makes use of available high-pressure motive gas to power a parallel,
sequentially initiated train of
ejectors to inlet a volume of zero pressure vented natural gas and discharge
the combined volumes
into the fuel gas system of a natural gas fuelled engine. Uniquely, the gas
discharged will not
require any significant modification to existing engine fuel gas systems.
Discharged gas volumes
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are introduced downstream of engine fuel gas pressure regulators on
turbocharged engines at a
pressure sufficient to admit discharged volumes into existing fuel gas
streams. Introducing
discharge volumes upstream of engine fuel gas pressure regulator(s) may also
prove capable,
primarily on normally aspirated engines. The addition of air to fuel ratio
control systems is not
required as existing engine fuel gas pressure and volume control devices are
sufficient to maintain
desired fuel supply as intended in natural gas fuelled engines of all
combustion types, including but
not limited to lean burn, lean turbulent, lean pre-chamber and conventional
rich burn
(stoichiometric).
Various processes common to the production and transmission of natural gas and
associated hydrocarbons result in the venting or release of gas(es) into the
atmosphere. Typical
sources of small volume vented methane emitters are compressor seals and
packings, valve
actuators and positioners - pneumatic instrumentation and controllers.
Generally referred to as
fugitive or vented natural gas volumes consisting of a typical 82 percent
methane (CH4) content; it
is desirable and prudent, given the global warming potential (GWP) value of
methane at ¨25 CO2e,
to mitigate the release of all, even the relatively small releases of natural
gas to atmosphere. The
invention depicted herein is intended to that purpose.
Natural gas consists largely of methane and other flammable hydrocarbon gases
deemed to
be greenhouse gases. Methane gas has been assigned a 100-year global warming
potential
(GWT)of 25 X, giving 1 kg methane an equivalence of 25 kg CO2 or 25 kg CO2e.
Continuing to allow
these vented gas emissions to be released directly into the atmosphere is
undesirable and may
have associated regulatory penalties; active flaring is a highly visible and
also a subjectively
objectional activity; directing into the combustion air intake of an engine or
burner may be cost
prohibative and due to the inconsistencies inherent with vented gas volumes
and pressures, create
complicated equipment performance instability issues.
The embodied invention provides a new and innovative system and method to
mitigate
routine vent gas releases to atmosphere by controlling and directing these
normally vented gas
volumes into the fuel supply system of a natural gas fuelled engine where it
will be combusted,
effectively creating a value add situation for the energy producer or
operator.
The embodied invention provides an innovative method to economically recover
small
volumes of vented gases released in normal day to day hydrocarbon production
operations.
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Use of multiple ejectors in a tandem, series configuration as described in
Canadian Patent
CA 2736412, Dresser-Rand Company, US, 2015/11/24, SUPERSONIC EJECTOR PACKAGE:
this
method consists of various series arrangements and constructs of gas to gas
ejectors perhaps
capable of higher ratios of compression than absolutely necessary. The lack of
a subsonic ejector
offering or a control and throughput capacity means or philosophy could also
limit the effective
performance of the prior disclosure.
The use of a high pressure liquid as a motive source for an ejector to inlet
gathered liquid
hydrocarbon storage tank vapors and discharge into a pressurized flare, sales
or inlet line is
described in United States Patent 5,195,587, Conoco Inc., 1993/03/23, VAPOR
RECOVERY SYSTEM.
In this instance the versatility of an ejector in a multi-phase application is
evident. No variable
capacity control is described. A high pressure liquid source compatible with
the process must be
available. The use of produced water as a motive fluid requires cold weather
considerations.
As detailed in United States Patent 5,533890, Thermatrix Inc., 1996/07/09,
METHOD AND
APPARATUS FOR CONTROL OF FUGITIVE VOC EMISSIONS: embodies an arrangement of
components suitable to collect and process a VOC emission stream into a
flameless combustor. A
gas to gas ejector is mentioned as an option to draw a slight vacuum on the
entire system post
combustor. Compressed air is to be considered as a motive source. The primary
attribute of this
method and apparatus appears to be the combustor.
In United States Patent, 8,113,181 62, REM Technology Inc., 2012/02/14, METHOD
AND
APPARATUS FOR CAPTURING AND CONTROLLING FUGITIVE GASES: the method describes
one in
which emitted gases are captured and directed to the air intake of an engine
or, should the
pressure at the air intake system exceed a predetermined value, release the
gases to vent through
a relief valve. Significant effort is made to manage the fluctuations in
volumes being introduced to
the intake air stream of the engine and the stability of the engine itself as
air/fuel control systems
react to varying air to fuel volumes and ratios. A sudden pressure and volume
fluctuation burst of
vented gases may over-tax the control system and cause the vented gas to vent
to atmosphere or
to flare. The requirement of sophisticated engine air-fuel control systems,
site utility power
requirements and PLC instrumentation and controls may eliminate this approach
uneconomical.
See also: World Intellectual Property Organization, WO 2009/052622 Al, REM
Technology Inc.,
2009/04/30 and WO 2006/094391 Al, REM Technology Inc., 2006/09/14 and United
States Patent,
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8,235,029 B2, REM Technology Inc., 2012/08/07, METHOD AND APPARATUS FOR
PROCESSING
DILUTED FUGITIVE GASES.
A similar system and method for capturing emitted vent gas(es) and directing,
as a diluted
stream, into the combustion air intake of an engine are described in United
States Patent,
9,046,062 B2, Dresser-Rand Company, 2015/06/02. Several sources from which
vent gas is sourced
are depicted in the drawings and description, the sources indicated are common
and not unique.
The use of a eductor with a gas motive inlet, vent gas inlet and combined gas
outlet
discharging into a fuel gas stream is briefly described and depicted in
Canadian Patent CA
2,685,655, REM Technology Inc., CA, 2017/04/25, METHOD AND APPARATUS FOR
PROCESSING
DILUTED FUGITIVE GASES. Illustration 14B is described for use on fuel injected
engines primarily as
a governing speed/fuel control device.
In both Canadian Patent CA 2,838,150, REM Technology Inc., CA, 2015/04/14,
SYSTEM AND
METHOD FOR CONTROLLING A FLOW OF VENT GASES TO A NATURAL GAS ENGINE and
Canadian
patent CA 2,601,027. REM Technology Inc., CA, 2013/08/20, METHOD AND APPARATUS
FOR
UTILISING FUGITIVE GASES AS A SUPPLEMENTARY FUEL SOURCE a system and method to
flow vent
gases into an engine combustion air supply is discussed. This approach
introduced fuel gas into the
engine air intake effectively altering manufacturer air to fuel ratio
intention and requiring the
addition of costly and somewhat elaborate air to fuel ration control systems
to compensate.
Introducing normally vented volumes of gas to engine combustion air intake
systems is essentially
different to the system and method discussed and depicted herein.
In United States Patent, 9,095,784, 1nSite Technologies Ltd., 2011/05/29,
VAPOR
RECOVERY UINT FOR STEAM ASSISTED GRAVITY DRAINAGE (SAGD) SYSTEM the use of an
ejector is
discussed and claimed to be useful in the vapour recovery process for a SAGD
heavy oil recovery
facility. The described process outlets the combined active and passive gas
volumes to a low
pressure burner such as a flare stack.
The foregoing vent gas release mitigation techniques are useful but there
still remains a
need to provide additional solutions to reduce the amount of greenhouse gases
normally emitted
to atmosphere as a normal process in gas production facilities. Relative to
existing options the
embodied new and innovative approach will provide users: 1) lower capital
outlay, attractive ROI
as savings in regulatory activities and emissions mitigation credit programs
are realized. 2) simple
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and reliable arrangement of components common to industry. 3) a broad range of
operation. 4)
directing vented gases into the fuel gas supply rather than the air intake of
an engine will create no
impact to engine stability or performance. 5) method and apparatus is well-
suited to use at gas
compression stations and other gas production facilities. 6) the ability of
this embodied apparatus
to discharge into pressures significantly higher than the vented gas pressure
with effective and
economical motive gas flow volumes and without the use of conventional pumps
and compressors,
is an innovative and desirable feature.
The innovation in this invention lies with the multiple configuration and
application of one,
two or more gas to gas ejectors assembled into the apparatus with unique
internal geometries and
similar motive pressures, unique internal geometries and dissimilar motive
pressures, similar
internal geometries and similar motive pressures or similar internal
geometries and dissimilar
motive pressures and to discharge recovered vented gases at a useful pressure.
The embodied system and method uniquely controls and discharges the combined
motive
and vent gas flow volumes into the existing fuel supply system of a natural
gas fuelled engine. In
this application a focused installation pertaining to the field of natural gas
compression is
presented, providing a system and method to significantly and economically
reduce the quantity of
atmospherically vented natural gas, particularly methane gas, normally
released in gas
compression operations and the operation of natural gas compression equipment
by recovering
the gas to use as a fuel gas for a natural gas engine.
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SUMMARY OF THE INVENTION
The present invention is directed to a means and method to inlet zero to low
pressure
vented, fugitive or exhausted gas volumes and discharge those volumes into the
existing fuel gas
supply systems of a natural gas fueled engine. To this end, greenhouse gases
such as methane are
recovered and prevented from escaping into the atmosphere.
The use of parts and components common to industry innovatively arranged and
configured to sequentially enable a parallel train of two or more gas to gas
ejectors of same or
differing flow volume capabilities will provide industry a vented gas
containment solution with a
large capacity variance that is readily retrofittable or will suitably
integrate with new equipment
packaging. This invention will prove the control and small quantity recovery
of vented gases
economical where the cost and configurability of a conventional a vapor
recovery compressor or
similar systems would be considered impractical due to high capital and
operating costs.
A typical installation for this invention would be a gas compression unit or
station where
vented and fugitive gases are collected and accumulated by means current and
common to
industry such as seal pots, tanks and knock-out vessels and routed to the
inlet port on one or more
gas to gas ejectors. The use of a seal pot is depicted and discussed herein. A
seal pot is a preferred
type of tank in that is provides a trap space for gases, a siphon drain
arrangement to manage
liquids and immersion tube(s) which effectively isolate the individual sources
of vented gas to
eliminate the possibility of pressure communication between sources.
Typical sources for vented gases are reciprocating compressor rod packings,
compressor
cylinder distance pieces, actuators, valve positioners and other
instrumentation and source
components on and off the compressor skid.
To facilitate the operation of the embodied invention, a high pressure motive
gas of 350 to
500 psig would be supplied from an appropriate point in the gas compression or
production
process to ensure correct ratio of motive to suction gas for effective ejector
operation. Motive gas
pressure would be controlled by a pressure regulating device and connected to
each individual
ejector via an operated valve. These valves will be opened sequentially and
corresponding ejectors
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activated as warranted by suction gas pressure and system design parameters.
As the motive gas
enters and passes through the ejector, gathered suction gas volumes are drawn
in, the ejector will
then discharge the combined high pressure motive gas and low pressure suction
gas volumes at a
design controlled pressure into fuel gas system of a natural gas fuelled
engine. Uniquely, the gas
discharged will not require any significant capability modification to
existing engine fuel gas
systems beyond provisioning a connection port. Discharged gas volumes are
introduced
downstream of engine fuel gas pressure regulators on turbocharged engines at a
pressure
sufficient to admit discharged volumes into existing fuel gas streams.
Introducing discharge
volumes upstream of engine fuel gas pressure regulator(s) will also be an
option primarily on
normally aspirated engines. Original equipment combustion air and fuel gas
management systems
will continue to function as intended. The addition of air to fuel ratio
control systems is not
required as existing engine fuel gas pressure and volume control devices are
sufficient to maintain
desired fuel supply as intended in natural gas fuelled engines of all
combustion types, including but
not limited to lean burn, lean turbulent, lean pre-chamber and conventional
rich burn designs
(stoichiometric).
A method of sequentially activating and deactivating the ejectors allows for
variable flow
volumes. A flow control computer with programmable and configurable Al & DO
may be used to
manage control of motive gas activation solenoid valves, suction gas pressure
sensing and
metering, system alarms and communication. A simple control system might be
preferred; such as
an electric switch gage or electric pilot controller with milliamp input and
output triggering a
relayed actuator. Two or more ejectors would be sequentially activated as
initiated by suction
pressure ranges and required system throughput capacity. Ejectors will be of a
constant-area
double-choke subsonic configuration and engineered and arranged to function
under variable and
unique design conditions. Should unusual discharge conditions or hinderances
occur, or a sudden
burst of suction gas volumes larger that total system design capacity, a set-
pressure cracking check
valve will open and release suction gas to vent or flare. Should vented gas
volumes reduce to a
point where negative gauge pressure may be realized, a recycle device is
employed to provide a
method of maintaining a minimum suction pressure by routing a portion of
ejector discharge
volumes back into device suction port. A pressure relief valve exhausting to
atmosphere or flare is
a last fail-safe should discharge pressures reach a critical high value.
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This invention would be more attractive than current market offerings of vent
gas
evacuation via electric drive vacuum pumps or compressors; lower operating
costs would be
expected as there are no rotating components such as electric motors or
positive displacement
compressors that require lubrication and life-cycle wear maintenance. Lower
capital costs would
be expected as there will be no requirement for A.C. motor electrical supply
to be installed.
The embodied method of introducing vent gas volumes into the engine fuel gas
supply
rather than engine combustion air is preferred in that existing engine fuel
pressure regulation
devices are sufficient to maintain intended engine operability, no additional
air to fuel ratio control
systems are required as would be with vent gas into engine air intake systems.
In addition,
utilization of a ejector inherently produces a suction or vacuum effect at the
vent gas inlet port
whereas other system use a differential pressure at engine air intake
downstream of air filter(s) to
vent gas and may cause an undesirable backpressure on venting systems and
components.
Other attributes of this invention include provision for the safe operation
and control of
this apparatus in a multitude of gas compositions, site specific pressure and
volume conditions and
control scenarios. A vacuum breaker in employed to manage minimum inlet
pressure with make-
up volumes recycled from the discharge stream. A back pressure regulator will
provide constant
discharge pressure and stable throughput volumes to minimize existing engine
fuel gas pressure
regulator, fuel valve and air fuel mixer actions.
It is required the fuel consumption volume of the engine be of a volume large
enough to
accommodate the additional system discharge volume. To that end, a means to
manage system
engagement and disengagement is required. On a turbo charged engine sensing
engine manifold
boost pressure is an effective method; set point calculation will initiate
system to operate only
when engine load is sufficient to warrant the introduction of system discharge
gas volumes into
the engine fuel piping downstream of the fuel gas regulator. On naturally
aspirated and draw-
through carbureted engine arrangements, system discharge volumes are
introduced upstream of
fuel gas regulator; an aspect of the means and system embodied herein is a
high discharge
pressure switch which will prevent system discharge flows until engine fuel
system pressure drop
to a point low enough to satisfy switch and initiate system operation.
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All configurations will require one or more ¨ depending on applicable codes or
regulations ¨
fuel gas shut off valves be installed to prevent any possible flow of fuel gas
at unit shut down
events.
The ubiquitous limitation of variable volume capability through a single
ejector will be
eliminated by optionally utilizing an arrangement of two or more ejectors
individually sized to
application and activated into duty as variable requirement demand and
programmed control
philosophies dictate. This innovative approach to capacity control allows
significant turn-up and
turn-down vent gas volume capture and throughput to containment recovery. By
activating
additional ejectors in a parallel arrangement based on suction pressure value
measurement this
apparatus will successfully manage vent gas volume increases and decrease
while minimizing over-
pressure atmospheric releases and low volume recycle actions.
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BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings:
FIG 1 is a representational schematic of the invention depicted in a
simplistic control
application where a single ejector is enabled and actuated to inlet a flow of
vented gas combining
with a flow of motive gas to discharge at a pressure suitable to flow into the
fuel supply system of
a natural gas fueled engine.
FIG 2 is a representational schematic of the invention depicted in a
simplistic control
application where two parallel ejectors are enabled by an external signal and
actuated via an
analogue suction pressure input device that produces at least two discrete
output signals to
activate one or both injectors enabling a flow of vented gas, combining with a
flow of motive gas to
discharge at a pressure suitable to flow into the fuel supply system of a
natural gas fueled engine.
FIG 3 is a representational schematic of the invention depicted in a PLC
control application
where three parallel ejectors are enabled and actuated as programmed based on
suction pressure
input and designed activation of one, two or three ejectors enabling a flow of
vented gas,
combining with a flow of motive gas to discharge at a pressure suitable to
flow into the fuel supply
system of a natural gas fueled engine.
Fig 4 is a representational two-dimensional drawing of a seal pot tank of
typical
construction. This tank is used to gather vented gas flows from one or more
sources and
communicate them to the inlet port of the ejector.
Fig 5 is a representational schematic of the invention as depicted in Fig 1
connected to and
in communication with a seal pot, such as the one illustrated in Fig 4.
Figs 6, 6a, 6b, are representational schematics depicting typical connection
points where
the system and method embodied herein will discharge into the fuel gas system
of a natural gas
engine. Fig 6 being a turbocharged natural gas engine, Fig 6a being a
naturally aspirated natural gas
engine; Fig 6b being a turbocharged engine with a low pressure fuel supply,
draw-through
carburetor arrangement.
Fig 7 is a graph showing system throughput performance on a typical single
ejector
arrangement typical of an install at a natural gas compression package
installation.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring first to FIG: 1 a depiction of the method and system incorporating a
single gas to
gas ejector is presented. A locally available motive gas is connected at
"Motive"; motive gas first
flows through a downstream pressure sensing regulator by which desired motive
gas pressure is
maintained. An optional flow measurement device 4a is used to measure motive
gas flow volumes
for calculation and reporting requirements. An actuated solenoid valve 7a is
connected to a control
panel, an existing and expandable local control panel or one specific to
apparatus installation.
Control can be accomplished by PLC or process sensing switch gauges. Apparatus
is to be switched
on only when discharged gas volumes can be consumed at volume required to
enable gas to gas
ejector function ¨ that is ¨ below ejector back pressure stall point.
Apparatus to be switched off by
a predetermined operations process value or at discharge pressure sensing
point 10a high value.
When normally closed actuated valve 7a is opened motive gas is introduced into
gas to gas ejector.
As understood in conventional fixed-area gas to gas ejector operational
theory, motive (high
pressure) gas flows into the ejector through the nozzle and into the diffuser
via a mixing chamber
creating an internal low pressure into which inlet gas volumes flow from
source. The inlet flow
passes through a one-way low pressure cracking check valve into the ejector
housing mixing
chamber to combine with the motive gas and enter the discharge diffuser
portion of the ejector
through to the ejector discharge port. These combined gas volumes are now
discharged from the
ejector at an intermediate pressure determined by the downstream contained
pressure into which
the discharge volumes are introduced and the ejector geometry and backpressure
valve 6. Also
installed at apparatus discharge is a check valve 1, an actuated normally
closed solenoid valve 7c
which serves the purpose of a redundant shut down, a pressure safety valve 11
and a flow
measurement device 4b. Inlet gas flow volume would be calculated by the value
at 4b and
subtracting the value at measurement device 4a. A recycle valve 5 communicates
discharge to inlet
¨ valve set point is application specific and prevents undesirable high vacuum
at inlet should inlet
flow volume be less than ejector design point(s). Pressure sensing devices,
inlet 10b and discharge
10a, can be configured to provide additional apparatus control; connected in
series with solenoids
7a & 7b to deactivate and isolate when abnormal operating points are
determined. A pressure
cracking check valve 2 will open inlet pressure volumes to safe low pressure
disposal or vent.
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Valves 7c are controlled locally or remotely in communications with parent
equipment fuel gas
shut off signals.
Shown in FIG: 2 is the apparatus configured with to gas to gas ejectors in a
parallel
arrangement with the valves and regulators necessary to accomplish a
controlled variable flow
throughput by the activation of one or both of the ejectors. As depicted in
FIG: 2 motive gas
"Motive" flows into the apparatus when actuated normally closed valves 7a and
7c are opened. A
downstream pressure sensing regulator is used to set and maintain motive gas
pressure. A flow
measurement device is optionally installed at 4a. Motive gas pressure/volume
can now be lowered
(if desired) at regulator 3a before entering ejector 8a. As motive gas flows
through ejector 8a inlet
gas if flowed through a low pressure cracking check valve 1, to the suction
port of ejector 8a,
combined with the motive gas volumes and discharged at an intermediate
pressure through a flow
measurement device 4b, a one way check valve 1, an solenoid actuated normally
closed valve and
a backpressure regulating valve. A pressure sensing point at inlet 10b and
discharge 10a can be
configured to provide additional apparatus control; connected in series with
solenoids 7a & 7b to
deactivate and isolate when abnormal operating points are determined. A
pressure cracking check
valve 2 will open inlet pressure volumes to safe low pressure disposal flare
or vent, a manual valve
9 allows bypass of entire apparatus. A vacuum breaker acting as a recycle
valve will add discharge
gas into inlet and maintain a minimum inlet pressure avoiding undesirable high
vacuum situations.
A multi-point switch gauge 12 provides a discrete output to solenoid valve 7b
and, based on a
application specific value at inlet pressure sensing point 10b, will open
valve 7b to activate ejector
8b. Depending on design, ejector geometry, motive pressure delta at ejectors
8a and 8b, additional
throughput capacity will be added to the apparatus. This additional capacity
will activate and
deactivate as determined by inlet pressure, an increase in pressure may be
caused by an expected
venting event or as vented gas volumes increase when wear components such as
rod packings and
seal age. The innovation in this invention lies with the multiple
configuration and application of
one, two or more gas to gas ejectors assembled into the apparatus with unique
internal
geometries and similar motive pressures, unique internal geometries and
dissimilar motive
pressures, similar internal geometries and similar motive pressures or similar
internal geometries
and dissimilar motive pressures. Additionally, a pressure cracking check valve
2 will open inlet
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pressure volumes to safe low pressure disposal flare or vent. A pressure
safety valve 11 will protect
the apparatus and associated process equipment from over pressure.
Referring to FIG: 3, an arrangement of three gas to gas ejectors 8a, 8b and 8c
are
configured is a parallel arrangement. Vented gas volumes generated as a result
of a hydrocarbons
production process are inlet "Inlet" on a common header and individual low
pressure cracking
check valves 2 to the ejectors. Hi pressure motive "Motive" gas is admitted
through a flow
measurement device 4a, a downstream sensing pressure regulator 3 when, global
control,
normally closed, solenoid actuated valves 7a & 7d are opened. At
initialization, motive gas flows to
ejector 8a only, motive gas pressure to ejector 8a can be further regulated at
valve 3a. Inlet gas is
flowed into ejector 8a and discharged at an intermediate pressure combined
with motive gas
volumes through a check valve 2 the open control valve 7d and a flow
measurement device 4b.
Vent gas flow will be calculated by subtracting flow value at 4a from value at
4b. Pressure sensing
points at inlet 10a and discharge 10b are fed to a PLC 6, program will respond
to inlet pressure
increases by adding ejector throughput volume opening motive gas control valve
7b to enable
ejector 8b. should additional capacity be required to maintain inlet pressures
as vented gas
volumes increase, control valve 7c will be opened and ejector 8c enabled.
Should vented gas
volumes diminish and inlet pressure decline, valves will be closed and
ejectors 8c & 8b deactivated
in sequence. Should vented gas volumes continue to diminish below the design
throughput
capacity of ejector 8a, recycle valve 5 will open and make up inlet volumes
with communicated
discharge gas. PLC will manage high discharge pressure by closing control
valves 7a & 7d and
opening control valve 9 to relieve system pressure; a pressure safety relief
valve 11 is also
incorporated to prevent over pressure occurrence. A pressure cracking check
valve 1 will open inlet
pressure volumes to safe low pressure disposal flare or vent, a manual valve
12 allows bypass of
entire apparatus. The innovation in this invention lies with the multiple
configuration and
application of one, two or more gas to gas ejectors assembled into the
apparatus with unique
internal geometries and similar motive pressures, unique internal geometries
and dissimilar motive
pressures, similar internal geometries and similar motive pressures or similar
internal geometries
and dissimilar motive pressures.
Referring to FIG: 4, a representative drawing of a seal pot common in the
natural gas
compression industry used to manage reciprocating compressor packing and
compartment drain
,
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and vent emissions is depicted in a modified configuration suitable for use
with the method and
system embodied herein. Vented gas and fluids are introduced at fittings 52;
an immersion tube
can be installed with outlet below seal pot fluid level effectively isolating
sources of vented gas
from one another. Fitting 43 is a drain, to be fitted with a manually operated
valve. Port 44 is a
siphon drain, configured to maintain a level of fluid within the seal pot
tank. A fluid level sight
gauge is located at 42. A high fluid level switch 45 and a low level switch 46
are connected to
system electric control wiring and or parent equipment panel for status
indication. The tank is a
low pressure design, less than 14.9 psig, and is protected from overpressure
by a suitable pressure
rated cracking check valve fitted at 42, a normally open actuated valve fitted
at 42 that fails open
in a system upset condition, and the pressure displacement of liquid level
through the siphon drain
until gas is free to flow to drain unimpeded. One or more port(s) 42 are
fitted to method and
system ejector inlet. Seal pot contains a mesh pad, as gas flow through the
seal pot from 52 to 41,
accompanying liquids drop out at the mesh pad which acts as a demister to
retain the liquids in the
seal pot to be routed drain 44 or 43.
Referring to FIG: 5, a representative schematic of the seal pot described in
Fig 4 is depicted
in communication with the inlet and drain connection points of the system
embodied herein. A
source of vented gas 51 is indicated as capable of flow through the seal pot
or directly to the
ejector inlet; this is an illustrated connection example. Another device 56,
an accumulator could
also be employed to capture and collect vented gas from multiple sources for
communication the
system ejector inlet.
FIG: 6 is a schematic representation of the fuel 68, air 65 and exhaust 66
systems of a
turbocharged natural gas fuelled engine indicating the point 67 at which the
system presented
herein will discharge the combined vent gas and motive gas volumes into the
engine existing fuel
supply piping. Introducing the gas volumes downstream of the engine fuel gas
regulator 69, will
not impede the normal function of the engine fuel gas regulator, it will
simply reduce the primary
fuel gas flow volume to compensate for the addition of gas volumes introduced
at 67. As intended,
the combined fuel gas volumes will flow at pressure sufficient to overcome the
turbocharger
charge air press, mix with air within carburetor and feed into the engine
through the throttle body
at the desired air fuel ration as intended.
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FIG: 6a, is a schematic representation of the fuel 68, air 65 and exhaust 66
systems of a
naturally aspirated natural gas fuelled engine indicating the point 67 at
which the system
presented herein will discharge the combined vent gas and motive gas volumes
into the engine
existing fuel supply piping. Ejector discharge gas pressure is set at a
pressure just above primary
gas supply pressure; as indicated 67 combining flows upstream of engine fuel
gas regulator.
Optionally, and in situations where required due to unusually high fuel gas
supply pressure, system
discharge may enter existing fuel gas supply downstream of engine fuel gas
regulator similarly to
point 67 indicated in Fig: 6. No matter the system entry point into engine
fuel gas piping, existing
engine air and fuel management components operate as originally intended with
no or only minor
adjustments required.
FIG: 6b, is a schematic representation of the fuel 68, air 65 and exhaust 66
systems of a low
pressure, draw-through carbureted, turbocharged natural gas fuelled engine
indicating the point
67 at which the system presented herein will discharge the combined vent gas
and motive gas
volumes into the engine existing fuel supply piping. System discharge gas is
fed into existing fuel
gas piping upstream of the fuel gas regulator, existing fuel and air
management components will
operate as originally intended with little or no adjustments required.
FIG: 7, is a series of three graphs displaying a specific ejector type,
operating at a range of
motive gas pressures with a system discharge pressure range of 20 - 35 psig.
Motive gas pressure
and volume is indicated; suction (vent) gas pressure and volume is indicated;
combined gas or total
volume throughput is also indicated on the graph. Throughput curve is typical
of fixed volume
ejector performance, this is one example only, volumes throughput is a result
of ejector design
geometry and operating ratio of motive to inlet gas volumes. Employing two or
more ejectors of
varying throughput capability, arranged in a parallel configuration and
enabling as inlet volume
increases dictate, offers a degree of throughout flexibility and a reserve
capacity capability to
manage intermittent or temporary surges in vent gas volumes.
The method and system described herein provides a recovery for natural gas
normally
vented to atmosphere to be routed to the fuel gas system of a natural gas
engine thereby
contributing a much lessened environmental impact. The system is simplistic in
approach and
economical to employ. The description discloses example apparatus and
components in the
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system, as such are illustrative in nature and are not to be construed as
limiting by the illustrative
depictions contained herein.
The scope and application of the method and system should not be constrained
by the
embodied representations presented but granted a wide-ranging interpretation
in whole.
CA 3069063 2020-01-21
