CA3061854A1 - Method and apparatus for recovering vented volumes of gas into containment - Google Patents

Abstract

ABSTRACT 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 pressurized containment. 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. Date reçue/Received date 2020-04-08

Description

2 TITLE
Method and apparatus for recovering vented volumes of gas into containment.
INTRODUCTION
The invention relates to a method and apparatus for eliminating or significantly reducing the volume of vented gas(es) released into the atmosphere.
BACKGROUND OF THE INVENTION
The invention relates to a method and apparatus for introducing a gathered low pressure volume of gas(es) into a pressure containment of higher pressure, thereby eliminating or significantly reduce the venting of these gases to atmosphere. 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 low pressure vented gas(es) and discharge the combined volumes into a contained pressure higher than the suction gas but lower than the motive gas.
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 are compressor seals and packings, valve actuators and positioners, pneumatic instrumentation, liquid storage tanks and other hydrocarbon processes such as dehydration.
Generally referred to as leaked or vented gases, these volumes are frequently released into the atmosphere or introduced into a flare system and combusted.
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.

3 The embodied invention provides a new and innovative method and apparatus to mitigate routine vent gas releases to atmosphere by introducing it into or back into pressure containment such as a gas compressor inlet or an engine fuel gas supply.
The embodied invention provides an innovative method to economically recover small volumes of vented gases released in normal day to day hydrocarbon production operations.
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 B2, 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 check 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

4 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, 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 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 byproduct of oil and gas production or other like industries. 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 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 higher than the vented gas pressure 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.

5 SUMMARY OF THE INVENTION
The present invention is directed to a means and method to inlet zero to low pressure vented or exhausted gas volumes and discharge those volumes into the pressure containment of a higher pressure. 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 where the cost and configurability of a conventional vapor recovery compressor 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 suction port on two or more gas to gas ejectors. Sources for vented gases could be reciprocating compressor rod packings, compressor cylinder distance pieces, actuators, valve positioners and other instrumentation and source components on and off the compressor skid.
High pressure motive gas 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 activated as warranted by suction gas pressure and system design parameters. As the motive gas enters and passes through the ejector, suction gas volumes are drawn in, the ejector will then discharge the combined high pressure motive gas and low pressure suction gas into the desired point of containment such as natural gas compressor inlet or a utility fuel gas line. The innovative design of this invention will also provide for use in applications

6 where H2S or CO2 content in the vented gases may have previously made recovery unpractical or prohibitively expensive.
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 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, the apparatus control logic will detect a rise in suction pressure and, at a specific value, open a valve and release suction gas to atmosphere 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 suction 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.
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. The ubiquitous limitation of variable volume capability through a single ejector will be eliminated by 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

7 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 by an external means.
FIG 2 is a representational schematic of the invention depicted in a simplistic control application where two parallel ejectors are enabled by an external means and actuated via an analogue suction pressure input device that produces at least two discrete output signals to activate one or both injectors.
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.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring first to FIG: 1 a depiction of the method and apparatus 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 where desired motive gas pressure is maintained. An optional flow measurement device 4a to measure motive gas flow volumes for calculation and reporting requirements. An actuated solenoid valve 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 10 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

8 pressure) gas flows into the ejector through the nozzle into the diffuser creating an internal low pressure are into witch inlet gas volumes, "Inlet" flow through a one-way low pressure cracking check valve into the ejector housing to combine with the motive gas and enter the discharge diffuser portion of the ejector. 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 install 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 would be application specific and prevent undesirable high vacuum at inlet should inlet flows 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 flare or vent, a manual valve

9 allows bypass of entire apparatus.
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 valve 7a and 7c are opened. A
downstream pressure sensing regulator is used to set and maintain motive gas pressure. A flow measurement device is installed at 4a. Motive gas 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 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 met 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 manual valve 9 allows bypass of entire apparatus. 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

10 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.

Claims (15)

11The embodiments of the invention in which exclusive property or privilege is claimed are defined as follows:

1. A method for delivering a volume of zero or low pressure gas into a higher contained pressure by utilizing 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 apparatus suction, an immediately available motive gas supply of appropriate pressure and volume is utilized, the gas to gas ejector(s) design is such that a useful discharge volume of gas comprising of combined suction and motive flow volumes will be produced.

2. Apparatus 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 for reducing the amount of a gas being vented, 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 method described in claim 1 will be suitable for vented gases recovery into conventional oil and gas production streams such as natural gas engine fuel gas supply, combustion burner fuel gas, incinerators, flare systems, gathering or vapor recovery compressor inlets.

6. Claim 5 described end-source usage of apparatus discharge gas volumes is representative, included but not limited to.

7. The gas to gas ejector(s) incorporated in the apparatus and operated in this method 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. An apparatus for abating typically vented volumes of gases 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 low pressure inlet gas volumes and higher pressure motive gas volumes at an intermediate pressure.
d. A discharge to inlet recycle provision provides additional throughput flow variance capability shout inlet gas volumes be insufficient to maintain ejector design performance. Recycle will be common to all ejectors via inlet and discharge headers.
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. Apparatus 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. 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 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 gas may impair the equipments, components, and devices' intended operation. Apparatus inlet will operate within a desired range, typical -10"hg to 0 psig or higher if so desired.

15. 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.