Method and Apparatus for Eliminating Hydrocarbon Gas Venting from Pneumatic Controllers

Abstract

A method and apparatus which provides the ability to capture natural gas which would otherwise be vented from control valves and use the captured natural gas to power a low pressure pilot light of a burner and/or to power a natural gas engine. In one embodiment, the captured natural gas can be supplemented with an additional supply of natural gas to ensure operation of the pilot and/or natural gas engine in the even that the captured natural gas is not sufficient to provide continuous power of the pilot and/or engine. Optionally, the captured natural gas can be sequestered in a storage vessel.

Claims

1. A method for eliminating hydrocarbon gas venting comprising: capturing hydrocarbon gas vented by one or more pneumatic controls; storing the captured hydrocarbon gas in a vessel; and directing the captured hydrocarbon gas to an apparatus, the apparatus not comprising a compressor.

2. The method of claim 1 wherein directing the captured hydrocarbon gas to an apparatus comprises directing the captured hydrocarbon gas to a hydrocarbon gas burner assembly.

3. The method of claim 1 wherein directing the captured hydrocarbon gas to an apparatus comprises directing the captured hydrocarbon gas to an engine.

4. The method of claim 2 wherein directing the captured hydrocarbon gas to a hydrocarbon gas burner assembly comprises directing the captured hydrocarbon gas to a pilot of the hydrocarbon gas burner assembly.

5. The method of claim 1 further comprising supplementing a supply of the captured hydrocarbon gas with an additional supply of hydrocarbon gas.

6. The method of claim 5 wherein supplementing a supply of the captured hydrocarbon gas with an additional supply of hydrocarbon gas comprises supplementing a supply of the captured hydrocarbon gas with a fuel gas train.

7. The method of claim 6 wherein supplementing a supply of the captured hydrocarbon gas with a fuel gas train comprises supplementing a supply of the captured hydrocarbon gas with a fuel gas train of a burner of the hydrocarbon gas burner assembly.

8. The method of claim 5 wherein supplementing a supply of the captured hydrocarbon gas comprises regulating at least a portion of the additional supply of hydrocarbon gas with a pressure control valve.

9. The method of claim 8 wherein regulating at least a portion of the additional supply of hydrocarbon gas with a pressure control valve comprises regulating at least a portion of the additional supply of hydrocarbon gas at a pressure less than an expected venting pressure of the one or more pneumatic controls but greater than a minimum operating pressure of at least a portion of the hydrocarbon gas burner assembly.

10. The method of claim 9 wherein regulating at least a portion of the additional supply of hydrocarbon gas at a pressure greater than a minimum operating pressure of at least a portion of the hydrocarbon gas burner assembly comprises regulating at least a portion of the additional supply of hydrocarbon gas at a pressure greater than a minimum operating pressure of a pilot of the hydrocarbon gas burner assembly.

11. The method of claim 3 further comprising supplementing a supply of the captured hydrocarbon gas with an additional supply of hydrocarbon gas.

12. A system for capturing and using pneumatic control hydrocarbon vent gas comprising: a supply line configured to collect hydrocarbon gas vented from one or more pneumatic controls; a vessel, said vessel comprising an inlet coupled to said supply line; and an outlet of said vessel coupled an apparatus, said apparatus not comprising a compressor.

13. The system of claim 12 wherein said apparatus comprises a hydrocarbon gas burner assembly.

14. The system of claim 13 wherein said outlet of said vessel is coupled to a pilot of said hydrocarbon gas burner assembly.

15. The system of claim 12 wherein said system further comprises an additional supply of hydrocarbon gas.

16. The system of claim 12 wherein said additional supply of hydrocarbon gas is derived from a fuel gas train.

17. The system of claim 12 wherein said fuel gas train comprises a fuel gas train for a burner.

18. The system of claim 12 wherein said apparatus comprises an engine.

19. The system of claim 18 wherein said system further comprises an additional supply of hydrocarbon gas.

20. The system of claim 18 further comprising a make-up pressure regulator set at or about a minimum operating pressure of said engine.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0015] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more embodiments of the invention and are not to be construed as limiting the invention. In the drawings:

[0016] FIG. 1 is a schematic diagram which illustrates a system for collecting and using gas from pneumatic controls in a low pressure pilot; and

[0017] FIG. 2 is a schematic diagram which illustrates a system for collecting and using gas from pneumatic controls on systems that utilize a natural gas fueled engine.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Embodiments of the present invention relate to system for collecting gas from pneumatic control units, storing it, and using it in a low-pressure pilot light for a gas burner. Embodiments of the present invention also relate to a system for collecting gas from pneumatic control units, storing it, and using it in a low-pressure fuel system for a natural gas fueled engine. Because this low-pressure fuel system supplements the fuel requirements to operate the engine, embodiments of the present invention thus enable operators to sell the fuel that would otherwise have been used to power the engine. Embodiments of the present invention thus not only generate additional revenue for the operator but also provide an effective and efficient system that allows operators to avoid venting natural gas into the atmosphere.

[0019] As best illustrated in FIG. 1 fuel recovery system, generally referred to herein as low-pressure pilot system 10 which powers low pressure pilot 12 for natural gas burner 14, which can include a burner orifice, venturi and burner tip. Low pressure pilot 12 can include a low pressure pilot orifice, venturi, and tip. Low-pressure pilot system 10, preferably collects one or more inflows of pneumatic control vent gas through one or more inlets 16, which then pass through one or more check valves 18 and enter pilot fuel vessel 20, which most preferably comprises drain valve 22 and/or pressure relief valve 24. Optionally, pilot fuel vessel 20 can be coupled to pressure gauge 26, which can optionally comprise a pressure sensor. An outlet of pilot fuel vessel 20 then preferably passes through valve 28, which is coupled to low pressure pilot 12, which is part of burner assembly 15. In one embodiment, pilot fuel vessel 20 need not be provided.

[0020] For embodiments, where the volume of pneumatic control vent gas may not be sufficient to reliably maintain ignition of low-pressure pilot 12, a flow of existing fuel gas 30 can be passed through pressure control valve 32, which is coupled to main burner fuel vessel 34. Main burner fuel vessel 34 preferably comprises drain valve 36 and/or pressure relief valve 38. Optionally, pressure gauge 40, which can comprise a pressure sensor, is preferably positioned to monitor pressure within main burner fuel vessel 34. An outlet of main burner fuel vessel 34 is preferably coupled to pressure control valve 42, an outlet of which can be coupled to, and thus have its outlet pressure monitored by, pressure gauge 44, which can optionally comprise a pressure sensor. An outlet of pressure control valve 42 is preferably coupled to valve 46 before being directed into pilot fuel vessel 20. Optionally, pressure control valve 48 can be disposed between valve 46 and pilot fuel vessel 20. In one embodiment, pressure control valve 48 can be set such that it discharges at a pressure that is below an expected venting pressure of collected pneumatic control vent gas 16, but at or above a minimum required operating pressure for low-pressure pilot 12. Thus, in one embodiment, pressure control valve 48 is preferably configured to have a discharge pressure of about 2 inches wc to about 12 inches wc and more preferably about 3 inches wc to about 7 inches wc. In one embodiment, pressure control valve 42 and/or pressure gauge 44 are optionally not provided.

[0021] In addition to an outlet of main burner fuel vessel 34 being directed through pressure control valve 42, an outlet of main burner fuel vessel 34 can also be coupled to pressure control valve 50 before passing to natural gas burner 14. Optionally, an outlet of pressure control valve 50 can be coupled to and thus monitored by pressure gauge 52, which can optionally comprise a sensor. Temperature control valve 54 can be provided to control a flow of gas entering natural gas burner 14. Optionally, valve 56 can also be provided between main burner fuel vessel 34 and natural gas burner 14. One or more of the various foregoing pressure and/or temperature control valves can be electrical or pneumatic. In one embodiment of the present invention, pneumatic controllers are used to control the various control and/or temperature valve. In one embodiment, the electrical control and/or temperature valves can comprise electrical control valves. In this embodiment, an electric control module preferably monitors one or more sensors, which can include one or more pressure and/or temperature sensors. The electric control module then controls one or more of the control and/or temperature valves based at least in part on the outputs of the one or more sensors.

[0022] Although numerous devices can be used and will provide desirable results, depending on the details of a particular application, in one embodiment, the following have been found to provide particularly desirable results for some applications:

[0023] pressure control valve 48 can include a FISHER® 912N, 250 Psig maximum inlet pressure, 3″-7″ wc outlet pressure, ¼″ FNPT inlet, ¼″ FNPT outlet (FISHER is a registered trademark of Fisher Controls International, LLC);

[0024] pressure relief valve 24 can include a Control Devices model 36JN37, brass body, 20 psig maximum operating pressure, set at 0.5 psig, brass seat, SS spring, ⅜″ MNPT connection;

[0025] check valve 18 can include a CHECK-ALL® Model U3DCSVT.125SS, carbon steel body, VITON® seat, 0.125 psig cracking pressure, SS spring, ½″ FNPT body connections (CHECK-ALL is a registered trademark of International Valve Corporation DBA Check-All Valve Manufacturing Co., VITON is a registered trademark of Dupont Down Elastomers L.L.C.);

[0026] One or more of the various pressure gauges can include a MARSH® model G22704, 2 ½″ dial face, 0-30″ wc range, brass socket, ¼″ MNPT bottom mount (MARSH is a registered trademark of Bellofram Corporation); and

[0027] Low-pressure pilot 12 can include an Eclipse LP injector model 04A, 20,000 Btu/hr@7″ wc pressure, ¼″ FNPT gas inlet, 1″ FNPT injector outlet.

[0028] By routing the vent gas to a system utilizing a low-pressure pilot capable of operating at about 3.5″ to about 28″ water column fuel pressure (about 0.125 psig to about 1 psig) instead of the traditional high-pressure pilot fuel pressures of about 5 psig to about 8 psig, embodiments of the present invention enable the consumption of the pneumatic controller vent gas in the pilot process, saving fuel gas that is traditionally used for the high-pressure pilot. In addition, the low-pressure pilot of embodiments of the present invention consumes approximately the same amount of fuel gas as the traditional pilot operating at about 5 psig to about 8 psig, so there is no significant increase or decrease in the heat input into the process or in the products of combustion released into the atmosphere when compared to a traditional high-pressure pilot. If, on occasion, there is a brief increase in the pilot heat output, the process thermostat will compensate by reducing the main burner output. A standard oil and gas production unit, typical of the Denver Basin, Colo., which utilizes pneumatic controllers designed to the preferred Environmental Protection Agency (“EPA”) National Gas Star Best Management Practices, produces approximately 10 ft.sup.3/hr to approximately 14 ft.sup.3/hr of vent gas from the pneumatic controls. This volume closely matches the volume of fuel gas used by a typical high-pressure pilot. Thus, in one embodiment, low-pressure pilot system 10 be used to replace a high-pressure pilot on legacy oil and gas production systems in the field today and/or can be incorporated into new production systems in lieu of a high-pressure pilot system. Replacing a high-pressure pilot system with low-pressure pilot system 10 eliminates the venting of pneumatic controller vent gas to the atmosphere as well as the need to add costly and ineffective add-on control devices that are required to collect the vent gas. Often, the add-on control devices are prone to poor online run times, which allows the pneumatic controllers to vent to the atmosphere uncontrolled for the period the add-on device is not operating.

[0029] Embodiments of low-pressure pilot system 10 can be integral to the operation of the process. Standing pilot technology and practice is well accepted, customary, and utilized all over the world. Embodiments of the present invention enable the use of most of the existing fuel gas and control systems on existing production units in the field today, for both large and small volume venting applications. Low-pressure pilot system 10 can collect all the vent gas available and route it to the low-pressure pilot. In one embodiment, low-pressure pilot system 10 preferably has the capacity to consume approximately 20 ft.sup.3/hr to about 60 ft.sup.3/hr and more preferably about 40 ft.sup.3/hr of vent gas when operating at about 28″ water column (about 1 psig) operating pressure. This pilot capacity enables embodiments of the present invention to be installed on many large modules utilizing numerous pneumatic controls, far greater in number than what would typically be encountered on a typical oil field production unit.

[0030] If an embodiment of the present invention is installed on small applications where the volume of vent gas is not sufficient to maintain a stable low-pressure pilot flame, embodiments of the present invention preferably incorporate a separate low-pressure pilot fuel gas system, which includes a make-up fuel pressure regulator set to a minimum operating pressure and volume that is needed to maintain a stable flame at the low-pressure pilot tip, and a pilot fuel vessel adequate in volume to smooth-out any sudden increase in vent gas (multiple pneumatic controllers venting at once as an example) without upsetting the operation of the pilot or over pressuring the pilot fuel gas system. Although the volume of pilot fuel vessel can be constructed to any desired size, in one embodiment, the volume of the pilot fuel vessel is most preferably about 1.5 cubic feet to about 4 cubic feet.

[0031] Although in one embodiment, low-pressure pilot 12 can remain continuously lit, as a standing pilot, in one embodiment, low-pressure pilot 12 is preferably only ignited shortly before natural gas burner 14 is to be ignited. In this embodiment, an electric arc can be initiated to ignite low-pressure pilot 12. Thus, in one embodiment, low-pressure pilot 12 does not remain continuously lit and thus is not a standing pilot. Optionally, the control unit can provide a burner management process such that a valve coupled to low-pressure pilot 12 is opened and an electric spark is initiated to ignite low-pressure pilot before gas is sent to natural gas burner 14. In one embodiment, the control unit can include an algorithm which initiates ignition of low-pressure pilot 12 based on pressure within vessel 20 and/or based on heat demand.

[0032] Referring now to FIG. 2 low-pressure fuel system 57, can be used to power engine 58, which can optionally comprise a naturally aspirated engine. Low-pressure fuel system 57 preferably collects one or more inflows of pneumatic control vent gas through one or more inlets 59, which then preferably pass through one or more check valves 60 and enter vent gas vessel 61, which most preferably comprises drain valve 62 and/or pressure relief valve 63. Optionally, vent gas vessel 61 can be coupled to pressure gauge 64, which can optionally comprise a pressure sensor. An outlet of vent gas vessel 61 then preferably passes through valve 66, then through fuel line 65 which is coupled to the fuel inlet of engine 58, which can include a fuel inlet of a carburetor or fuel injection system of engine 58. In one embodiment, vent gas vessel 61 need not be provided.

[0033] For embodiments, where the volume of pneumatic control vent gas will not be sufficient to reliably maintain fuel to engine 58, a flow of existing fuel gas 67 can be passed through fuel pressure control valve 68, which is preferably coupled to the engine low-pressure fuel gas valve 69, through fuel line 70. Optionally, pressure gauge 71, which can comprise a sensor, is preferably positioned to monitor pressure downstream of fuel gas pressure control valve 68. An outlet of fuel gas pressure control valve 68 is preferably coupled to fuel gas low-pressure control valve 69 through fuel line 72. An outlet of fuel gas low-pressure fuel gas valve 69 can be directed through fuel line 70 into vent gas vessel 61, an outlet of which can be coupled to, and thus have its outlet pressure monitored by, pressure gauge 64, which can optionally comprise a sensor. An outlet of vent gas vessel 61 is preferably coupled to valve 66 before being directed into the inlet of the carburetor or fuel injection system of engine 58, which can optionally include a naturally aspirated engine, through fuel line 65. One or more of the various foregoing pressure control valves can be electrical or pneumatic. In one embodiment of the present invention, pneumatic controllers can be used to control the various control valves. In one embodiment, the electrical control can comprise electrical control valves. In this embodiment, an electric control module preferably monitors one or more sensors, which can include one or more pressure and/or temperature sensors. The electric control module then controls one or more of the control valves based at least in part on the outputs of the one or more sensors.

[0034] Although numerous devices can be used and will provide desirable results, depending on the details of a particular application, in one embodiment, the following have been found to provide particularly desirable results for some applications:

[0035] pressure control valve 69 can include a IMPCO® Model KN regulator, 13.4″ wc maximum inlet pressure, 8″-10″ wc outlet pressure, ¾″ FNPT inlet, ⅜″ FNPT outlet (IMPCO is a registered trademark of EMPCO, LLC);

[0036] pressure relief valve 63 can include a Control Devices model 36JN37, brass body, 20 psig max. operating pressure, set at 0.75 psig, brass seat, SS spring, ⅜″ MNPT connection;

[0037] check valve 60 can include a CHECK-ALL® Model U3DCSVT.125SS, carbon steel body, Viton seat, 0.125 psig cracking pressure, SS spring, ½″ FNPT body connections;

[0038] One or more of the various pressure gauges can include a MARSH® model G22704, 2 ½″ dial face, 0-30″ wc range, brass socket, ¼″ MNPT bottom mount.

[0039] By routing the vent gas to a fuel system utilizing a low-pressure regulator capable of operating from about 0.5″ to about 14″ water column fuel pressure (about 0.02 psig to about 0.51 psig), embodiments of the present invention enable the consumption of the pneumatic controller vent gas in the engine fuel system, saving fuel gas that is traditionally vented to the atmosphere. In addition, a typical natural gas fueled engine of the horsepower size common in the industry consumes much greater amounts of fuel gas per hour than that what is typically produced by pneumatic controls. A typical 95 brake horsepower (“bhp”) natural gas fueled engine running at approximately 75% load will consume approximately 7850 Btu/bhp-hr fuel gas, or approximately 560 standard cubic feet per hour (“scf/hr”) of natural gas. A standard oil and gas industry wellhead compression system utilizing a naturally aspirated natural gas fueled engine system typical of the Denver Basin, Colo., which utilizes pneumatic controllers designed to the preferred Environmental Protection Agency (“EPA”) National Gas Star Best Management Practices, produces approximately 10 ft.sup.3/hr to approximately 14 ft.sup.3/hr of vent gas from the pneumatic controls. For a typical 95 bhp engine system operating at or near 75% load, there is no increase in the products of combustion released into the atmosphere when compared to a traditional engine fuel gas system. If, on occasion, there is a brief increase in the vent gas volume, the engine fuel intake system will compensate by reducing the volume of fuel introduced into the vent vessel through the low-pressure regulator. Thus, in one embodiment, low-pressure fuel system 57 be retrofitted to capture pneumatic controller vent gas on legacy engine systems in the field today and/or can be incorporated into new engine systems. Installation of low-pressure fuel system 57 eliminates venting of pneumatic controller vent gas to the atmosphere as well as the need to add costly and ineffective add-on control devices that are required to collect the vent gas. Often, the add-on control devices are prone to poor online run times, which allows the pneumatic controllers to vent to the atmosphere uncontrolled for the period the add-on device is not operating.

[0040] Embodiments of low-pressure fuel system 57 can be integral to the operation of the process. Low-pressure natural gas engine fuel technology and practice is well accepted, customary, and utilized all over the world. Embodiments of the present invention enable the use, with some modification, of most of the existing fuel gas and control systems on existing engine systems in the field today, for both large and small horsepower applications. Low-pressure fuel system 57 can collect all the vent gas available and route it to the engine fuel inlet. In one embodiment, low-pressure fuel system 57 has the capacity to consume approximately 60 ft.sup.3/hr and more of vent gas when operating at about 10″ water column (about 0.37 psig) operating pressure. This capacity enables embodiments of the present invention to be installed on many large modules utilizing numerous pneumatic controls, far greater in number than what would typically be encountered on a typical engine system.

[0041] If an embodiment of the present invention is installed on small horsepower applications where the volume of vent gas is not sufficient to maintain a stable running engine, embodiments of the present invention preferably incorporate a separate low-pressure fuel gas system, which includes a make-up fuel pressure regulator set to at or about minimum operating pressure and volume that is needed to maintain a stable running engine, vent gas vessel adequate in volume to smooth-out any sudden increase in vent gas (multiple pneumatic controllers venting at once as an example) without upsetting the operation of the engine or over pressuring the engine fuel gas system. Although the volume of the vent gas vessel can be constructed to any desired size, in one embodiment, the volume of the vent gas vessel is most preferably about 1.5 cubic feet to about 4 cubic feet. In one embodiment, collected pneumatic control vent gas can be stored and routed to a pilot of the natural draft gas burner. Optionally, collected pneumatic control vent gas can be sent to any other desired location, including other low-pressure systems. For example, in one embodiment, the recovered vapors can be sent to oil storage tanks, where additional vapors accumulate and are collected and used in other processes. Throughout the application, where reference is made to a gauge, such gauge can optionally include one or more of a mechanical gauge, and/or an electronic sensor, which can be monitored by a microcontroller, processor, and/or circuit, which can perform one or more functions based on sensor output and/or measurement, including but not limited to displaying a value, and/or causing activation of one or more valves.

[0042] In one embodiment, the present invention utilizes captured vent gas from one or more pneumatic controls without compressing the captured vent gas. The term “vent gas” as used herein can include gas that was used to activate a control. In one embodiment, the captured control vent gas can be sent to a burner assembly.

[0043] Optionally, the control unit, if provided, can include a field programmable gate array and/or a general or specific purpose computer or distributed system programmed with computer software implementing steps described above, which computer software may be in any appropriate computer language, including but not limited to C, C++, FORTRAN, BASIC, Java, Python, Linux, assembly language, microcode, distributed programming languages, etc. The control unit can include a plurality of such computers/distributed systems (e.g., connected over the Internet and/or one or more intranets) in a variety of hardware implementations. For example, data processing can be performed by an appropriately programmed microprocessor, microcontroller, computing cloud, Application Specific Integrated Circuit (ASIC), or the like, in conjunction with appropriate memory, network, and bus elements. One or more processors and/or microcontrollers can operate via instructions of the computer code and the software is preferably stored on one or more tangible non-transitive memory-storage devices. All computer software disclosed herein may be embodied on any non-transitory computer-readable medium (including combinations of mediums), including without limitation CD-ROMs, DVD-ROMs, hard drives (local or network storage device), USB keys, other removable drives, ROM, and firmware.

[0044] Embodiments of the present invention can be used with high-bleed pneumatic control devices and/or low-bleed control devices. In one embodiment, high-bleed devices can optionally be used to power a natural-gas engine, while low-bleed control devices can be used to provide fuel to a low-pressure pilot. Thus, embodiments of the present invention can be used for controllers that have not yet been replaced and/or modified to low-bleed devices and embodiments of the present invention can be used to eliminate the venting of natural gas from controllers that have already been remediated according to current industry-recognized “best practices”.

[0045] Note that in the specification and claims, “about”, “approximately”, and/or “substantially” means within twenty percent (20%) of the amount, value, or condition given.

[0046] Embodiments of the present invention can include every combination of features that are disclosed herein independently from each other. Although the invention has been described in detail with particular reference to the disclosed embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference. Unless specifically stated as being “essential” above, none of the various components or the interrelationship thereof are essential to the operation of the invention. Rather, desirable results can be achieved by substituting various components and/or reconfiguring their relationships with one another.