Internal Combustion Engine Fuel Gas Blending System

Abstract

A fuel gas blending system for internal combustion engines combines two or more gas streams to achieve a blended fuel gas having a suitable heating value (HV) for a given engine. A relatively high HV gas, for example gas produced from an oil and/or gas well, or containerized propane, is blended with a relatively low HV gas, for example nitrogen. The blended gas achieves a fuel gas with a suitable HV. Suitable means for combining the gas streams, analyzing the blended gas stream for HV and other properties, and adjusting the blend as needed are all provided. The system permits use of available gaseous fuel sources, even if not suitable in an unblended state, to efficiently fuel internal combustion engines.

Claims

1. A system for producing a gaseous fuel stream of a desired composition for an internal combustion engine, comprising: a relatively high heating value gas source; a relatively low heating value gas source; a means for blending the relatively high and low heating value gas sources; and a means for adjusting the respective flow rates of the relatively high heating value gas source and the relatively low heating value gas source.

2. The system of claim 1, further comprising: a means for analyzing the composition of the blended gas stream; and a means for supplying the blended gaseous fuel stream to an internal combustion engine.

3. The system of claim 1, wherein said relatively high heating value gas source comprises a gas stream from an oil and/or gas well.

4. The system of claim 1, wherein said relatively high heating value gas source comprises gas from a containerized liquified gas source.

5. The system of claim 1, wherein said relatively low heating value gas source comprises nitrogen.

6. The system of claim 1, wherein said relatively low heating value gas source comprises ambient air.

7. The system of claim 1, wherein said relatively low heating value gas source comprises engine exhaust gas.

8. The system of claim 1, wherein said relatively high heating value gas source comprises a gas stream from an oil and/or gas well; and said relatively low heating value gas source comprises nitrogen.

9. The system of claim 1, wherein: said relatively high heating value gas source comprises a gas stream from an oil and/or gas well; and said relatively low heating value gas source comprises ambient air.

10. The system of claim 1, wherein: said relatively high heating value gas source comprises a gas stream from an oil and/or gas well; and said relatively low heating value gas source comprises engine exhaust gas.

11. The system of claim 1, wherein: said relatively high heating value gas source comprises gas from a containerized liquified gas source; and said relatively low heating value gas source comprises nitrogen.

12. The system of claim 1, wherein: said relatively high heating value gas source comprises gas from a containerized liquified gas source; and said relatively low heating value gas source comprises ambient air.

13. The system of claim 1, wherein: said relatively high heating value gas source comprises gas from a containerized liquified gas source; and said relatively low heating value gas source comprises engine exhaust gas.

14. The system of claim 1, wherein: said means for blending the relatively high and low heating value gas sources comprises one or more flow control valves independently controlling flow from said relatively high and relatively low heating value gas sources; said means for analyzing the composition of the blended gas stream comprises an oxygen sensor which measures oxygen in an exhaust stream from said engine; said means for adjusting the respective flow rates of the relatively high and relatively low heating value gas sources comprises a programmable logic controller which receives input from said oxygen sensor, and which is operatively connected to actuators on said flow control valves which can adjust flow rates through said flow control valves in response to a signal from said programmable logic controller; and further comprising one or more digital processors operatively coupled to said system.

15. The system of claim 14, wherein said relatively high heating value gas source comprises a containerized liquified gas source, and further comprising a heat exchanger which receives heat from an exhaust stream from said engine, and transfers said heat to said liquified gas source flowing through said heat exchanger, thereby gasifying said liquified gas source.

16. The system of claim 1, wherein said relatively high heating value gas source comprises a liquified gas source, and further comprising a heat exchanger which receives heat from an exhaust stream from said engine, and transfers said heat to said liquified gas source flowing through said heat exchanger, thereby gasifying said liquified gas source.

17. A system for producing a gaseous fuel stream of a desired composition for an internal combustion engine, comprising: a relatively high heating value gas source; a relatively low heating value gas source; a means for blending the relatively high and low heating value gas sources comprising one or more flow control valves independently controlling flow from said relatively high and relatively low heating value gas sources, said gas sources flowing into an accumulator tank; a means for adjusting the respective flow rates of the relatively high heating value gas source and the relatively low heating value gas source comprising a programmable logic controller which receives input from said oxygen sensor, and which is operatively connected to actuators on said flow control valves which can adjust flow rates through said flow control valves in response to a signal from said programmable logic controller; a means for analyzing the composition of the blended gas stream comprising an oxygen sensor which measures oxygen in an exhaust stream from said engine; a means for supplying the blended gaseous fuel stream to an internal combustion engine; and one or more digital processors operatively coupled to said system.

18. A method for producing a fuel gas stream of a desired heating value, from at least a relatively high heating value gas source and a relatively low heating value gas source, comprising the steps of: a) providing a fuel gas blending system comprising: a means for blending said relatively high and low heating value gas sources; and a means for adjusting the respective flow rates of said relatively high and low heating value gas sources; b) flowing gas from said relatively high and relatively low heating value gas sources to said fuel gas blending system and blending said relatively high and relatively low heating value gases, forming a blended fuel gas stream; c) analyzing the composition of said blended fuel gas stream; d) adjusting the flows of said relatively high and relatively low heating value gases, as required, to yield a desired composition of said blended fuel gas stream; and e) flowing said desired composition of blended fuel gas to an internal combustion engine.

19. The method of claim 18, wherein said relatively high heating value gas source is an oil and/or gas well.

20. The method of claim 18, wherein said relatively high heating value gas source is a containerized liquified gas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a simplified view of the apparatus embodying the principles of the present invention.

[0014] FIG. 2 is a more detailed diagram setting out certain elements of the apparatus.

[0015] FIG. 3 is a perspective view of one embodiment of the apparatus.

[0016] FIGS. 4 and 5 are additional views of the apparatus mounted in a frame, FIG. 5 showing shrouding doors in place on the frame.

DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT(S)

[0017] While various fuel gas monitoring and modification systems can be made, embodying the principles of the present invention, with reference to the drawings some of the presently preferred embodiments can be described.

[0018] FIG. 1 is a simplified diagram of the system of the present invention, broadly illustrating the fundamental elements of the system. FIG. 2 is a diagram setting forth additional detail of an exemplary system. An accumulator tank, shown, receives two gas streams: a (relatively) high HV stream, as labeled; and a (relatively) low HV stream, as labeled. For convenience, these two streams will be referred to as the high HV stream and the low HV stream. A fuel line carries a blended fuel gas stream (that is, a blend of the high HV stream and the low HV stream) from the accumulator tank to the engine, labeled. The blended fuel gas stream has properties, primarily a HV figure, which permit efficient operation of the engine. As shown in FIG. 2, the high HV stream may comprise field gas, namely natural gas produced from one or more oil/gas wells, in substantially a non-processed state, having undergone only primary separation (to separate hydrocarbon liquids and water from the natural gas, still leaving typically a relatively rich natural gas stream). Alternatively, the high HV stream may comprise propane or other hydrocarbon, stored in liquid state on site, as all or part of the stream. An appropriate valve 10 controls this gas stream flow.

[0019] It is understood that still other sources may comprise the HV fuel stream and the scope of the present invention encompasses any such sources. As a further example, the HV stream may comprise propane or other hydrocarbon produced in a refinery or similar installation, which may comprise an excess gas stream from the refinery.

[0020] The internal combustion engine may be any type of engine using a gas fuel stream, including but not limited to a reciprocating (piston) engine, a turbine, a rotary engine, or any other type.

[0021] Typically, a valve, which may be a ball valve 6, a check valve 7, a pressure regulator 8, and a flow control valve 9 (which may be a v-notch ball valve, and which is fitted with an actuator) are installed in the flowline of the high HV stream, and control flow of that stream into the accumulator tank. As described in more detail later, flow control valve 9 is responsive to readings from the O2 (oxygen) sensor, 1; and related PLC (programmable logic controller), 2.

[0022] As an alternative to an O2 sensor, a chromatograph can be used to determine the richness of the fuel gas stream.

[0023] The other input to the accumulator tank is the low HV stream. In the embodiment shown in FIG. 2, one of the possible sources for the low HV gas stream is exhaust gas from the engine. The exhaust gas (from engine exhaust outlet, noted) is flowed through a heat exchanger 4, to lower the temperature to an acceptable value; through a compressor 5, to achieve the desired pressure; then through a ball valve 6, a check valve 7, a pressure regulator 8, and a flow control valve 9 (which may be a v-notch ball valve, and which is fitted with an actuator) and control flow of that stream into the accumulator tank. As described in more detail later, flow control valve 9 is responsive to readings from the O2 (oxygen) sensor, 1; and related PLC (programmable logic controller), 2.

[0024] Alternatively, rather than use of exhaust gas from the engine, ambient air may be used as the low HV gas source. Use of air (which is still compressed before flowing to the accumulator tank) avoids the need for a heat exchanger and cooling of the low HV stream. In FIG. 1, in the event that ambient air, or an inert gas such as nitrogen, is to be used as the low HV gas, the air or inert gas is introduced to the low HV flowstream generally as noted (downstream of heat exchanger 4, which is not needed, and upstream of compressor 5, so that the air or inert gas can be compressed). It is understood that the scope of the present invention encompasses all low HV sources.

[0025] The system monitors the overall HV of the fuel gas stream and adjusts the ratios (relative flowrates) of the high HV and low HV streams to yield a fuel gas with a suitable HV. Oxygen sensor 1 detects oxygen level in the engine exhaust; if the O2 level in the exhaust is too high, then there is insufficient high HV gas, and via PLC (2), and flow control valves 9, the flow rates are adjusted (in relative terms) to increase HV gas flow. Alternatively, if the O2 level in the exhaust is too low, then there is too much high HV gas, and via PLC (2), and flow control valves 9, the flow rates are adjusted (in relative terms) to decrease HV gas flow.

[0026] The accumulator tank also comprises pressure sensor 3. When pressure sensor 3 senses a decrease in the accumulator tank pressure, indicating increased fuel demand by the engine, then via pressure sensor 3, PLC 2, and flow control valves 9, flow rate from the accumulator tank is increased by opening both flow control valves in unison, thereby preserving the high HV/low HV ratio then in place. It is understood that a decrease in fuel demand results in an opposite action.

[0027] Any liquids which drop out of the combined gas streams in the accumulator tank can be evacuated via a liquid dump valve at the base of the accumulator tank. Strainers and filters as appropriate may be placed in the gas flow lines to ensure that no solids enter the system.

[0028] It is understood that the system can also be used to increase the HV of a gas source, to make it suitable for a fuel gas; e.g., if the primary gas source is a relatively low HV gas, such as bio-gas, then the HV of the blended fuel gas stream can be increased by the addition of propane or other relatively high HV gas.

[0029] FIG. 3 is a perspective view of an embodiment of the system, generally as depicted in FIG. 1, with various components labeled.

[0030] FIGS. 4 and 5 depict the key components of the system mounted in or on a frame, with FIG. 5 also showing protective or shroud doors in place on the frame.

[0031] Note that one or more digital processors are operatively connected to the various components of the system, to permit efficient operation.

Use of the System

[0032] An exemplary use of the system can be described. The fuel gas system, as noted above, can be mounted within a frame and transported to a desired location, for example a well pad on which are located one or more producing oil/gas wells, and at which is located an internal combustion engine. The engine may be used to drive an electric generating unit or for any other purpose. The gas stream from the on-site separator system (into which the overall flowstream from the well is flowed) can serve as the high HV stream, and connected to the inlet labeled in FIG. 2 as field gas in. A suitable low HV stream is connected, depending upon the HV (and other) characteristics of the HV stream. As noted above, the low HV stream may comprise (by way of example only) ambient air, exhaust from the engine, or gasified nitrogen (typically brought on site in a liquid state).

[0033] The characteristics of the engine are sufficiently known that some estimate of high HV/low HV ratio (a starting ratio) can be made. The high HV and low HV streams are then flowed to the accumulator tank in a desired ratio, the mixture flowed as fuel gas to the engine, and the engine started. Via oxygen sensor 1 feeding signals to PLC 2, and thence controlling flow control valves 9, the appropriate high HV/low HV mixture can be obtained and retained. As noted above, one or more digital processors enable collection of operating data and use of same to adjust flow conditions.

CONCLUSION

[0034] While the preceding description contains many specificities, it is to be understood that same are presented only to describe some of the presently preferred embodiments of the invention, and not by way of limitation. Changes can be made to various aspects of the invention, without departing from the scope thereof.

[0035] Therefore, the scope of the invention is to be determined not by the illustrative examples set forth above, but by the appended claims and their legal equivalents.

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