CA3069063A1 - System and methdo for controlling and introducing a flow of vent gases into the fuel supply of a natural gas engine - Google Patents

Abstract

ABSTRACT OF THE DESCRIPTION
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 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 Date Recue/Date Received 2020-04-29 corresponding ejectors 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 Date Recue/Date Received 2020-04-29 valve exhausting to atmosphere or flare is a last fail-safe should discharge pressures reach a critical high value.
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 Date Recue/Date Received 2020-04-29 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.
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.
Date Recue/Date Received 2020-04-29

Description

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

2 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.

3 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,

4 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

5 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.

6 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

7 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.

8 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.

9 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.

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.

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.

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 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 , 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.

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 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.

Claims (18)

1The embodiments of the invention in which exclusive property or privilege is claimed are defined as follows:

1. A system for delivering a flow volume of zero or very low pressure gas into the fuel gas supply system of natural gas fuelled engines by mean of utilizing a singular or an arrangement of gas-to-gas ejectors configured, controlled and operated in such a manner.
Normally vented gas volumes are captured, contained and inlet to the system suction or inlet port, an immediately available motive gas supply of appropriate pressure and volume is utilized, the gas to gas ejector(s) design is such that a discharged volume of gas comprising of combined suction and motive flow volumes will be produced at a pressure suitable for use.

2. Said system may comprise of one or more gas to gas ejectors employed in the method as described in claim 1. Ejector flow volume design may vary with each ejector employed on a single system or ejector flow volume design may be identical to each ejector employed on a single system. Functional motive pressure and volume may vary for each ejector employed on a single system or motive pressure and volume may be identical for each ejector employed on a single system.

3. A method and system for reducing the amount of vented natural gas being exhausted or released into the atmosphere.

4. A method for reducing the amount of recognized green house gas volume releases, such as methane gas into the atmosphere.

5. The discharged volume of gas produced by the system described in claim 1, the combined inlet vent gas and motive gas flows, will be introduced into the fuel system of a natural gas engine. Rather than being released to atmosphere, vent gas will be consumed as fuel.

6. Claim 5 described end-source usage of system discharge gas volumes is representative, _ included to but not limited to natural gas engines. Other end use possibilities are potential and probable.

7. The gas to gas ejectors incorporated in the system and operated as described herein will be of varying internal geometries, a constant area design of varying fixed clearances when combined with a reasonable range of motive gas pressures, in application specific arrangements, will provide an innovative functionality over a broad performance range.

8. A system useful for the recovery and practical use of typically vented volumes of natural gas released during the processing production of hydrocarbon products comprising:
a. An inlet for one or more sources of vented gas.
b. An inlet for locally sourced motive gas of sufficient pressure and volume to operate.
c. A discharge, where as a determined application of incorporated gas to gas ejector(s), produce a combined flow of low pressure inlet gas volumes and higher pressure motive gas volumes at an intermediate pressure.
d. A discharge to inlet recycle provision (vacuum breaker) provides additional inlet flow variance capability should inlet gas volumes be insufficient to maintain ejector design performance. Recycle will be applied to primary ejectors as required.
System discharge flow will remain relatively consistent regardless of variances in vent gas (suction).
e. One or more gas to gas ejectors as described in claim 7 are arranged and deployed in an innovative and manner unique to application requirement.

9. Method incorporates various means to enable and operate one or more gas to gas ejectors thereby allowing a range of throughput flows.

10. Method includes upset condition over-pressure provisions to protect equipments and workers. Over pressure protection devices are utilized at inlet and discharge.

11. Method incorporates a discharge back pressure regulation device in order to maintain gas to gas ejector fixed area flow consistency.

12. Method provides for global motive gas pressure regulation with the option of additional devices deployed to reduce motive gas pressure below global motive pressure at individual ejectors as desired to optimize application.

13. System initialization, flow solenoid activation, can be 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. System is to be enabled only when discharged gas volumes can be consumed in quantity sufficient to enable effective gas to gas ejector function; that is below ejector back pressure stall point.
Enablement sensing points may include engine intake manifold pressure, engine speed, engine calculated percentage load (PLC), process valve position or process pressure points.
Apparatus to be switched off by a predetermined operations process value or at discharge pressure sensing point high value.

14. Method provides no restriction at apparatus inlet during non-upset operation; this is an important and innovative operational characteristic as any additional backpressure on equipments, components and devices venting characteristics may impair the equipments, components, and devices' intended operation. At design throughput, system inlet will operate within a desirable pressure range, typical -10"hg to 1 psig.

15. Though omitted from drawings, system may incorporated strainers, filters, nd/or demisters as a matter of course and requirement to provide clean and suitable gas flows at inlet, motive and discharge.

16. Shut off valves type, requirement and configuration as illustrated in Fig:
1, 7c, are dependent on the point of system discharge into engine fuel gas system and appliocable codes and regulations.

17. Method is capable of providing a variable throughput. 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.

18. Notable to this method is the unique and heretofore unrealized method of vent gas volumes being discharged into the natural gas engine fuel gas supply system.
Method does not require any significant modifications or additions to engine fuel supply and control components.