Multi-pump gas recovery systems

Abstract

Example multi-pump gas recovery systems are disclosed herein. An example gas recovery system includes a drawdown gas supply line fluidly coupled to a drawdown gas source, a drawdown gas return line fluidly coupled to a gas discharge line, and a pumping system including a first pump stage and a second pump stage. The first pump stage is to pump drawdown gas from the drawdown gas supply line to an interstage gas line. The second pump stage is arranged in series with the first pump stage, and is to pump the drawdown gas from the interstage gas line to the drawdown gas return line such that the drawdown gas is transferred from the drawdown gas source to the gas discharge line.

Description

MULTI-PUMP GAS RECOVERY SYSTEMSFIELD OF THE DISCLOSURE

[0001] This disclosure relates generally to gas recovery systems and, more particularly, to multi -pump gas recovery systems.BACKGROUND

[0002] Facilities such as buildings, manufacturing plants, factories, etc. commonly use natural gas for various purposes such as for heating (e.g., air heating, water heating, etc.), power generation, transportation, etc. The gas is routed through various lines (e.g., pipes) throughout the facility. In some instances, such as during maintenance or cleaning, it is desired to evacuate the natural gas from one or more pipes in the facility. Facilities often vent the natural gas to the atmosphere, which is wasteful and can be harmful to the environment.BRIEF DESCRIPTION OF THE DRAWINGS

[0003] FIG. 1 is a schematic diagram of an example multi-pump gas recovery’ system implemented in connection with a facility.

[0004] FIG. 2 is a more detailed schematic diagram of the example multi-pump gas recovery’ system of FIG. 1.

[0005] FIG. 3 is a schematic diagram of an example pump configuration of one of the pumps of the example multi-pump gas recovery system of FIG. 2.

[0006] FIG. 4 is a schematic diagram of another example pump configuration of one of the pumps of the example multi -pump gas recovery system of FIG. 2.

[0007] FIG. 5 is a schematic diagram of an example switching valve used in connection with one of the pumps of the example multi-pump gas recovery system of FIG. 2.

[0008] FIG. 6 is a schematic diagram of the example switching valve of FIG. 5 showing an example in which the example pump is used to produce pressurized air.

[0009] In general, the same reference numbers w ill be used throughout the drawing(s) and accompanying written description to refer to the same or like parts. The figures are not to scale. Instead, the thickness of the layers or regions may be enlarged in the drawings. Although the figures show layers and regions with clean lines and boundaries, some or all of these linesand / or boundaries may be idealized. In reality, the boundaries and / or lines may be unobservable, blended, and / or irregular.DETAILED DESCRIPTION

[0010] Disclosed herein are example gas recovery systems that can be used to transfer gas from a gas source, referred to herein as a drawdown or blowdown gas source, to a gas discharge line. Many facilities (e.g., compression stations, buildings, manufacturing plants, refineries, etc.) include one or more natural gas lines of different pressures (e.g., 100 pounds- per-square inch (psi) and lOOOpsi). These gas lines route the natural gas throughout the facility' for various purposes, such as for heating equipment, power generation equipment, transportation of natural gas to other locations, etc. In known operations, during maintenance or cleaning of the gas lines, the gas lines are isolated (e.g., by closing two valves) and then vented to the atmosphere. However, this venting is wasteful and potentially harmful to the environment. The example gas recovery' systems disclosed herein can be used to collect gas from a drawdown gas source (e.g., one or more pipes or pipe sections) and re-inject the gas back into one or more of the gas lines, which reduces or prevents harmful emissions to the atmosphere.

[0011] An example gas recover}' system disclosed herein includes a pumping system that includes two pump stages arranged in series. Each pump stage includes one or more pumps. The first pump stage pumps and / or otherwise transfers gas from the drawdown gas source to an interstage gas line, and the second pump stage pumps and / or otherwise transfers the gas from the interstage gas line to a gas discharge line, such as a high or low pressure gas line at the facility. As such, the first and second pump stages yvork in series to transfer gas from the drawdown gas source to the gas discharge line. In some examples, the first pump stage includes three pumps that are arranged in parallel with each other. In some examples, the three pumps of the first stage are configured as single acting piston pumps, while a fourth pump of the second stage is configured as a double acting piston pump. The three pumps of the first pump stage collect and pump gas from the drawdown gas source to the interstage gas line to ensure a sufficient flow of gas is provided to the fourth pump of the second stage, and the second stage then pumps the gas from the interstage gas line to the gas discharge line. Other known multi-pump systems may use multiple pumps in parallel only bet veen the drawdown gas source and the gas discharge line. However, these known configurations suffer from preferential floyv problems. The example gas recovery systems disclosed herein are configured to force the gas floyv through the system in a particular manner to avoid or eliminate such preferential flow problems. This gives greatercontrol and predictability on the load cycles of the pumps, as well as improves the ability to accurately predict drawdown time because there is no preferential bypass.

[0012] In some instances, the example systems disclosed herein may be operated entirely by pneumatics and hydraulics. In other words, the example gas recovery system may not include or utilize any electronic components or devices. Because natural gas is combustible, it is advantageous to avoid use of electrical components that could cause a spark in the vicinity of the combustible fluid. The example gas recovery system can operate entirely autonomously using pneumatic and hydraulic power. Further, because the example system does not require electrical power, the example systems can continue to operate even in the event of a power outage at the facility.

[0013] The example systems disclosed herein refer to various lines. The lines represent fluid connections between two or more locations. The lines may be implemented as any ty pe of line, hose, tube, pipe, fluid connector, etc. for routing fluid between two locations. The lines can also be implemented as passageways, channels, and / or openings in a structure (e.g., a device body) that allows fluid flow between two locations (directly or indirectly).

[0014] FIG. 1 is a schematic of an example gas recovery system 100 implemented in an example facility 102 having a high pressure gas line 104 and a low pressure gas line 106. The gas recovery system 100 includes a pumping system 110. The example gas recovery system 100 utilizes a pressure differential between the high pressure gas line 104 and the low pressure gas line 106 to operate the pumping system 110 for transfernng gas from a drawdown gas source 108 to a gas discharge line. In this example, the gas discharge line is the low pressure gas line 106. In other words, the drawdown gas is transferred from the draw down gas source 108 to the low pressure gas line 106. The facility' 102 can represent any facility (indoors or outdoors) that utilizes natural gas, such as a compression station, a manufacturing facility, a power plant, a refinery, an office building, etc. Many facilities have gas lines with higher and lower pressures. For example, the high pressure gas line 104 may cany' natural gas at about lOOOpsi, while the low pressure gas line 106 may carry natural gas at about lOOpsi. The high and low pressure gas lines 104, 106 may route gas to various equipment in the facility 102 such as heaters, gas power generators, etc. In some examples, the facility- 102 may have additional gas lines at other pressures. In some examples, natural gas is provided to the facility 102 by a single gas line at a certain pressure, and the facility' 102 provides devices (e.g., a pressure regulator, a compression station) for splitting the gas into various gas lines or manifolds at different pressures for use throughout the facility 102.

[0015] The drawdown gas source 108 can correspond to any source of gas that is desired to be emptied (evacuated) or reduced in pressure. For example, the drawdown gas source 108 may be from one or more pipes or vessels during maintenance and / or cleaning. For example, maintenance and / or cleaning may need to be performed on one or more pipes or pipe sections that carry natural gas. Before performing the maintenance, the pipes or sections of pipe can be isolated (e.g., by closing two valves) and the gas in the pipes or sections of pipe can be evacuated by the pumping system 100 and transferred to the low pressure gas line 106. Therefore, instead of venting the natural gas to the atmosphere as seen in known procedures, the example gas recovery' system 100 can be used to capture and transfer the gas from these drawdown sources and re-inject the gas into another gas location. In other examples, the drawdown gas source 108 can represent gas from another source. For example, the drawdown gas source 108 can be gas collected from one or more gas-operated device(s) (e.g., valves, actuators, sensors, etc.) rather than allowing these devices to vent gas to the atmosphere. In the illustrated example, the gas recovery system 100 injects the gas into the low pressure gas line 106, but in other examples could inject the gas into the high pressure gas line 104. Therefore, the example gas recovery system 100 reduces and / or prevents harmful emissions into the atmosphere.

[0016] In the illustrated example, the gas recovery system 100 includes the pumping system 110, which may also be referred to as a compressor system. The pumping system 100 includes multiple pumps, as disclosed in further detail in connection with FIG. 2. The pumping system 100 is driven by the differential pressure between the high pressure gas line 104 and the low pressure gas line 106. In particular, the gas recovery system 100 includes a drive gas supply line 112 that fluidly couples the high pressure gas line 104 to an inlet of the pumping system 110, and a drive gas return line 114 that fluidly couples an outlet of the driving side of the pumping system 110 to the low pressure gas line 106. High pressure gas flows through the pumps of the pumping system 110 from the high pressure gas line 104 to the low pressure gas line 106, which provides power to the pumps of the pumping system 110. The gas recovery system 100 includes a drawdown gas supply line 116 that fluidly couples the drawdown gas source 108 and an inlet of the driven side of the pumping system 110, and a drawdown gas return line 118 that fluidly couples the outlet of the driven side of the pumping system 110 and the low pressure gas line 106. Therefore, when the pumping system 110 is activated, the pumping system 110 pumps and / or otherwise transfers gas from the drawdown gas source 108 to the low pressure gas line 106.

[0017] FIG. 2 is a more detailed schematic diagram of the example gas recovery system 100 of FIG. 1. In the illustrated example, the pumping system 110 includes a first pump stage 201 and a second pump stage 203. Each of the pump stages 201, 203 can include one or more pumps, as disclosed in further detail herein. The first and second pump stages 201, 203 are arranged in series to pump drawdown gas from the drawdown gas source 108 to the low pressure gas line 106 (i.e., the gas discharge line). The first pump stage 201 is fluidly coupled to the drawdown gas supply line 116. The first pump stage 201 pumps drawdown gas from the draw down gas supply line 116 to an interstage gas line 208. The second pump stage 203 pumps the drawdown gas from the interstage gas line 208 to the draw dow n gas return line 118. As such, the drawdown gas is transferred from the drawdown gas source 108 to the low pressure gas line 106.

[0018] In the illustrated example, the first pump stage 201 includes three pumps, namely, a first pump 200, a second pump 202, and a third pump 204, and the second pump stage 203 includes a fourth pump 206. In this example, each of the pumps 200, 202, 204. 206 is a reciprocating piston pump. Each of the pumps 200. 202, 204. 206 has a driving cylinder (in the middle) and one or more pumping cylinders. For each pump, the driving cylinder drives and / or otherwise powers the pumping cylinder(s). The configurations of the pumps 200, 202, 204, 206 are discussed in further detail herein. The drive gas supply line 112 provides high pressure gas to the driving cylinders of each of the pumps 200, 202, 204. 206 for driving or powering the pumps 200, 202. 204, 206. The drive gas return line 114 supplies or routes the used gas from the driving cylinders to the low pressure gas line 106.

[0019] The draw down gas supply line 116 routes the drawdown gas to inlets of the pumping cylinder(s) of the first, second, and third pumps 200, 202, 206. The interstage gas line 208 fluidly connects the outlets of the pumping cylinder(s) of the first, second, and third pumps 200, 202, 206 to the inlets of the pumping cylinder(s) of the fourth pump 206. The draw dow n gas return line 118 routes the gas from the outlets of the pumping cylinder(s) of the fourth pump 206 to the low pressure gas line 106. Therefore, as can be appreciated, in this example, the first, second, and third pumps 200, 202. 204 (i.e., the first pump stage 201) arranged in parallel with each other, and the fourth pump 206 (i.e., the second pump stage 203) is arranged in series with the first, second, and third pumps 200, 202, 204.

[0020] Before describing the gas recovery' system 100 in further detail, a description of the operation of the pumps 200, 202, 204, 206 is provided in connection with FIGS. 3 and 4. In particular, FIG. 3 is a schematic of the first pump 200, and FIG. 4 is a schematic of the fourthpump 206. The first, second, and third pumps 200, 202, 204 are arranged or configured the same. Therefore, any description of the first pump 200 in connection with FIG. 3 can likewise apply to the second and third pumps 202, 204.

[0021] FIG. 3 is a schematic of the first pump 200. As disclosed above, the first pump 200 is driven and / or otherwise powered by the differential pressure between the high pressure gas line 104 and the low pressure gas line 106. When the first pump 200 is activated, the first pump 200 transfers fluid from the drawdown gas supply line 116 to the interstage gas line 208.

[0022] In the illustrated example of FIG. 3, the first pump 200 includes a drive cylinder 300 and first and second coupling blocks 302a, 302b coupled to opposite ends of the drive cylinder 300. The first pump 200 includes a first pumping cylinder 304a coupled to and extending from the first coupling block 302a, and a second pumping cylinder 304b coupled to an extending from the second coupling block 302b. The first pump 200 includes a first gas block 306a coupled to the distal end of the first pumping cylinder 304a, and a second gas block 306b coupled to the distal end of the second pumping cylinder 304b.

[0023] The drive cylinder 300 and the coupling blocks 302a, 302b define a drive chamber 308. In the illustrated example, the first pump 200 includes a drive piston 310 in the drive chamber 308. The drive piston 310 divides the drive chamber 308 into a first chamber 312a (between the drive piston 310 and the first coupling block 302a) and a second chamber 312b (between the drive piston 310 and the second coupling block 302b). As disclosed in further detail herein, high pressure gas from the high pressure gas line 104 is supplied, in an alternating sequence, into the first chamber 312a and the second chamber 312b to cause the drive piston 310 to move back-and-forth in the drive chamber 308 in a reciprocating motion.

[0024] In the illustrated example of FIG. 3, the first pump 200 includes a rod 314 coupled to an extending from the drive piston 310 in both directions. The rod 314 extends through the first coupling block 302a and into the first pumping cylinder 304a. As shown in FIG. 3, the first pump 200 includes a first piston 316a disposed in the first pumping cylinder 304a and coupled to the rod 314. The first piston 316a divides the first pumping cylinder 304a into first and second chambers 318a. 318b, which may be referred to as a double acting cylinder chamber. As show n in FIG. 3. the first gas block 306a includes (e.g.. forms or defines) a first fluid passageway 320a with an inlet check valve 322a that fluidly couples the draw-down gas supply line 116 and the first chamber 318a, and a second fluid passagew ay 320b with an outlet check valve 322b that fluidly couples the first chamber 318a and the interstage gas line 208. In other examples, any of the check valves can be arranged outside of the blocks. As the drivepiston 310 moves back-and-forth, the drive piston 310 moves the first piston 316a back-and- forth in the first pumping cylinder 304a. When the first piston 316a is moved in a first direction, such as to the right in FIG. 3, gas is drawn from the drawdown gas supply line 116 and through the inlet check valve 322a into the first chamber 318a, and when the first piston 316a is moved in a second (opposite) direction, such as to the left in FIG. 3, gas in the first chamber 318a is pushed through the outlet check valve 322b and to the interstage gas line 208. This reciprocating motion continues such that gas is pumped and / or otherwise transferred from the draw down gas supply line 116 to the interstage gas line 208.

[0025] Similar to the first pumping cylinder 304a, the first pump 200 includes a second piston 316b that is disposed in the second pumping cylinder 304b and coupled to the rod 314, and which divides the divides the second pumping cylinder 304b into first and second chambers 326a, 326b. As shown in FIG. 3, the second gas block 306b includes (e.g., forms or defines) a first fluid passageway 328a with an inlet check valve 330a that fluidly couples the drawdown gas supply line 116 and the first chamber 326a, and a second fluid passageway 328b with an outlet check valve 330b that fluidly couples the first chamber 326a and the interstage gas line 208. Therefore, movement of the second piston 316b similarly moves gas from the draw down gas supply line 116 to the interstage gas line 208.

[0026] In the illustrated example, the second chamber 318b of the first cy linder 304a and the second chamber 326b of the second cylinder 304b are fluidly connected by a line 332. The second chambers 318b, 326b may be filled with air or another gas (e.g., nitrogen). As the pistons 316a, 316b move back-and-forth, the air is merely transferred back-and-forth between the second chambers 318b, 326b. Therefore, in this example, the second chambers 318b, 326b (e.g., the back sides of the pistons 316a, 316b) are not used for pumping gas. As such, in this example, the pumping cylinders 304a. 304b are configured as single acting piston pumps. While in this example the first pump 200 includes two pumping cylinders 304a, 304b, in other examples, the first pump 200 may include only one pumping cylinder.

[0027] As disclosed above, the first pump 200 is powered or driven by high pressure gas from the high pressure gas line 104. The first pump 200 includes a switching valve 334. The switching valve 334 is fluidly coupled to the drive gas supply line 112. The switching valve 146 alternates betw een a first state and a second state. In the first state, the switching valve 146 fluidly connects the drive gas supply line 112 and the first chamber 312a, which supplies high pressure gas into the first chamber 312a to move the drive piston 310 to the right in FIG. 3, and fluidly connects the second chamber 312b and the drive gas return line 114 to release gas in thesecond chamber 312b to the drive gas return line 114 (and, thus, to the low pressure gas line 106 (FIGS. 1 and 2)). In the second state, the switching valve 334 fluidly connects the drive gas supply line 1 12 and the second chamber 312b, which supplies high pressure gas into the second chamber 312b to move the drive piston 310 to the left in FIG. 3, and fluidly connects the first chamber 312a and the drive gas return line 114 to release gas in the first chamber 312a to the driving gas return line 114 (and, thus, to the low pressure gas line 106). The switching valve 146 alternatives rapidly between these first and second states. This operation causes the drive piston 310 to move back-and-forth in a reciprocating motion.

[0028] To signal to the switching valve 334 when the drive piston 310 has reached the end of the drive chamber 308, the first pump 200 includes a first example end-of-stroke switch 336a and a second example end-of-stroke switch 336b. The first and second end-of-stroke stiches 336a, 336b may be pneumatic switches that provide signals (e.g., air pressure signals) to the switching valve 334. In the illustrated example, the first switch 336a is coupled to the first coupling block 302a, and the second example switch 336b is coupled to the second coupling block 302b, but in other examples can be disposed in other locations. As an example operation, the switching valve 146 is in the second state in which high pressure gas is supplied into the second chamber 312b while the first chamber 312a is vented to the drive gas return line 114 (and, thus, to the low pressure gas line 106). This causes the drive piston 310 to move to the left in FIG. 3. When the drive piston 310 reaches the left end of the drive chamber 308 (e.g.. the end-of-stroke). the drive piston 310 physically contacts or engages the first switch 336a. This triggers the first switch 336a to transmit a pneumatic signal (e.g., a pressurized air signal) to the switching valve 334. In response to receiving the pneumatic signal, the switching valve 334 switches to the first state in which high pressure gas is supplied to the first chamber 312a and while gas from second chamber 312b is vented to the drive gas return line 114 (and, thus, to the low pressure gas line 106), which causes the drive piston 310 to move to the right in FIG. 3. When the drive piston 310 reaches the right end of the drive chamber 308 (e.g., the end-of- stroke), the drive piston 310 physically contacts or engages the second switch 336b. The second switch 336b transmits a pneumatic signal to the switching valve 334. In response, the switching valve 334 switches back to the second state, and the example process continues. This switching causes the drive piston 310 to move back-and-forth in a reciprocating mod on. As such, the first and second pistons 316a, 316b are also driven back-and-forth in their respective cylinders 304a, 304b. which causes the pumping action to transfer fluid from the drawdown gas supply line 116 to the interstage gas line 208.

[0029] FIG. 4 is a schematic of the fourth pump 206. The fourth pump 206 is substantially the same as the first pump 200. Therefore, the parts of the fourth pump 206 in FIG. 4 that are the same as the first pump 200 of FIG. 3 have been renumbered as 400 series numbers.

[0030] As shown in FIG. 4, the first coupling block 402a includes (e.g., forms or defines) a first fluid passageway 438a with an inlet check valve 440a that fluidly couples the interstage gas line 208 and the second chamber 418b of the first cylinder 404a, and a second fluid passageway 438b with an outlet check valve 440b that fluidly couples the second chamber 418b and the drawdown gas return line 118. Similarly, the second coupling block 402b includes (e.g., forms or defines) a first fluid passagew ay 442a with an inlet check valve 444a that fluidly couples the interstage gas line 208 and the second chamber 426b of the second cylinder 404b, and a second fluid passageway 442b with an outlet check valve 444b that fluidly couples the second chamber 426b and the drawdown gas return line 118. Therefore, both chambers 418a, 418b of the first pumping cylinder 404a and both chambers 426a, 426b of the second pumping cylinder 404b are used for pumping the draw down gas from the interstage gas line 208 to the drawdown gas return line 118. As such, the pumping cylinders 404a. 404b are configured as double acting piston pumps. While in this example the fourth pump 206 includes two pumping cylinders 404a, 404b, in other examples, the fourth pump 206 may include only one pumping cylinder.

[0031] Referring back to FIG. 2, the first, second, and third pumps 200. 202, 204 are arranged in parallel and pump drawdown gas from the drawdown gas supply line 116 to the interstage gas line 208, and the fourth pump 206 is arranged in series with the first, second, and third pumps 200, 202, 204 and pumps gas from the interstage as line 208 to the drawdown gas return line 118 and, thus, to the low pressure gas line 106. Also, in this example, the first, second, and third pumps 200, 202. 204 only utilize the outer chambers of the pumping cylinders to pump the drawdown gas (as shown in FIG. 3), while the fourth pump 206 utilizes both chambers of both pumping cylinders to pump the drawn gas (as shown in FIG. 4). In other words, the first, second, and third pumps 200, 202, 204 utilize single acting piston pumping action, while the fourth pump 206 utilizes double acting piston pumping action. In this configuration, the first, second, and third pumps 200, 202, 204 collect and compress the drawdown gas as a single acting application to increase the preloaded gas volume to feed the fourth pump 206 as a double acting cylinder. This allow s for greater compressor efficiency and for all gas flow to be utilized throughout the pump arrangement. Also, drawdown gas is forced to flow through the pumps in this particular flow path, which gives more control andpr edictability on load cycles. Further, this configuration also has decreased drawdown time that can be more accurately calculated as there is no preferential bypass route as seen in other known pumping configurations.

[0032] In the illustrated example of FIG. 2, the drive gas supply line 112 provides high pressure gas from the high pressure gas line 104 to each of the driving cylinders of the pumps 200, 202. 204, 206. As shown in FIG. 2, the gas recovery system 100 include a first filter 210 coupled to the drive gas supply line 112. In some instances, the natural gas in the high pressure gas line 104 may carry contaminants (e.g., particulate or debris such as pipe scale, grit, sand, rust, etc., chemicals such as iron sulfide, etc.) that could cause damage or adverse effects to the downstream devices. Therefore, the first filter 210 is used to filter out and / or otherwise remove these contaminants before reaching the downstream devices (e.g.. the valve 212, the pumps 200. 202, 204, 206, etc.).

[0033] In the illustrated example, the gas recovery’ system 100 includes a valve 212 (e.g., a switch) coupled to and / or otherwise incorporated into the drive gas supply line 112, between the high pressure gas line 104 and the pumps 200. 202, 204, 206. The valve 212 controls whether high pressure gas flows to the pumps 200, 202, 204, 206. The valve 212 is operable between a closed state and an open state. When the valve 212 is closed, the valve 212 blocks or prevents the flow of gas to the pumps 200, 202, 204, 206 and, thus, the pumping sy stem 110 is off or deactivated. When it is desired to utilize the gas recovery’ system 100 (e.g., to transfer gas from the drawdown gas source 108 to the low pressure gas line 106). the valve 212 can be opened. When the valve 212 is opened, the high pressure gas is allowed to flow through the pumps 200, 202, 204, 206 to the low pressure gas line 106, therefore activating and / or otherwise driving each of the pumps 200, 202, 204, 206. In some examples, the valve 212 is a manually operated valve. The valve 212 can be manually opened or closed when it is desired to activate or deactivate the pumping system 110. In other examples, the valve 212 is a pneumatically or hydraulically operated valve. The valve 212 may be configured to automatically open or close.

[0034] As shown in FIG. 2, the gas recovery system 100 includes a second filter 214 coupled to the drawdown gas supply line 116, which is used to filter and / or remove contaminates from the drawdown gas before reaching the pumps 200, 202. 204, 206. The gas recovery system 100 also includes a sensor 216 coupled to the drawdown gas supply line 116.

[0035] As shown in FIG. 2, the draw down gas exits the fourth pump 206 and flows through the drawdown gas return line 118 to the low pressure gas line 106. In this example, the drawdown gas return line 118 is fluidly connected to the drive gas return line 114 upstream ofthe low pressure gas line 106. As such, the two gases combine together and flow into the low pressure gas line 106. However, in other examples, the drive gas return line 114 and the drawdown gas return line 118 can be separately fluidly connected to the low pressure gas line 106.

[0036] In the illustrated example, the gas recovery system 100 includes a heat exchanger 218 coupled to the drawdown gas return line 118. The heat exchanger 218 may be an air-cooled heat exchanger. The heat exchanger 218 reduces the temperature of the drawdown gas before being injected into the low pressure gas line 106.

[0037] In the illustrated example, the gas recovery system 100 includes a sensing and pressure reducing valve 220 coupled to the drive gas return line 114 upstream of the low pressure gas line 106.

[0038] In the illustrated example, the gas recovery system 100 utilizes pressurized air from a compressed air line 222 to control one or more devices of the system 100. Many facilities have compressed air lines throughout the facility that can be tapped into and used. As shown in FIG. 2. the high pressure air is routed via one or more lines to the sensor 216 and the sensing and PRV 220. Further, the high pressure air is routed to each of the pump 200, 202, 204, 206. As disclosed above in connection with FIGS. 3 and 4, the pumps 200, 202, 204, 206 include end-of-stroke switches 336a, 336b, 436a, 436b that provide a pneumatic signal to the switching valves 334, 434. The end-of-stroke switches 336a, 336b. 436a, 436b utilize the compressed air to provide pneumatic signals to the switching valves 334. 434 to cause the switching valves 334, 434 to switch states.

[0039] As disclosed above, the pumps 200, 202, 204, 206 can be powered by gas (natural gas) from the high pressure gas line 104 based on the pressure differential between the high pressure gas line 104 and the low pressure gas line 106. In some examples, the pumping system 110 is operable between a gas driven mode in which high pressure gas (natural gas) is used to drive the pumps 200, 202, 204, 206, and an air driven mode in which high pressure air is used to drive the pumps 200, 202, 204, 206. This may be beneficial in situations where a differential gas pressure is not available or is not high enough to effectively drive the pumps 200, 202. 204, 206.

[0040] As shown in FIG. 2, a valve 224 is coupled to the drive gas supply line 112. The compressed air line 222 is fluidly coupled to the valve 224. The valve 224 operates between a first state in which the valve 224 allows high pressure drive gas from the high pressure gas line 104 to be supplied through the drive gas supply line 1 12 to the pumps 200, 202, 204. 206, and asecond state where the high pressure drive gas is shut off and instead high pressure air from the compressed air line 222 is supplied through the drive gas supply line 112 to the pumps 200, 202. 204, 206. When it is desired to switch to air driven configuration, the valve 212 is closed (to block the flow of high pressure gas into the drive gas supply line 112), and the valve 224 switches from the first state to the second state. As such, in the second state, high pressure air is supplied to the driving cylinders of the pumps 200, 202. 204, 206, which therefore drives the pumps 200, 202, 204, 206 in the same manner as described in connection with FIGS. 3 and 4. In some examples, the valve 224 is pneumatically operated (e.g., using the compressed air from the compressed air line 222).

[0041] As shown in FIG. 2, a valve 226 is coupled to the drive gas return line 114, upstream of the low pressure gas line 106. When the pumping system 110 is in the gas driven mode, the valve 226 is in a first state that allows the drive gas coming from the pumps 200, 202, 204, 206 to be supplied the low pressure gas line 106. However, when the pumping system 110 is in the air driven move, the valve 226 switches to a second state in which the valve 26 vents the air in the drawdown gas supply line 116 to the atmosphere. As such, the air exiting the driving cylinders of the pumps 200, 202, 204, 206 is vented to the atmosphere, rather than being injected into the low pressure gas line 106. When it is desired to switch back to the gas driven mode, the valve 224 switches back to the first state, and the valve 212 is opened. The valve 226 is left in the second state (e.g., open) until gas begins exiting the valve 226. As such, all air is purged from the drive gas return line 114. This purging ensures no air is injected into the low pressure gas line 106. Then, after gas begins exiting the valve 226, the valve 226 is switched back to the first state to direct the gas to the low pressure gas line 106.

[0042] FIG. 5 is a schematic of an example the switching valve 334 for the first pump 200. The other pumps 202, 204. 206 include similar switching valves 334, 434. Therefore, any of the aspects disclosed in connection with the switching valve 334 for the first pump 200 can likewise apply to the switching valves 334, 434 for the other pumps 202, 204, 206.

[0043] The switching valve 334 includes a first switch 500 and a second switch 502 that alternate between connecting the high pressure gas line 104 to one of the chambers 312a, 312b of the drive chamber 308 and venting the other chamber 312a, 312b to the low pressure gas line 106. For instance, the first switch 500 is operable between a first state in which the drive gas supply line 112 is fluidly connected to the first chamber 312a and a second state in which the drive gas supply line 112 is fluidly connected to the second chamber 312b. The second switch 502 is operable between a first state in which the first chamber 312a is fluidly connected thedrive gas return line 114 and a second state in which the second chamber 312b is fluidly connected to the drive gas return line 114. The first and second switches 500, 502 are always in opposite states and switch back-and-forth at the same time. Therefore, one of the chambers 312a, 312b is always receiving high pressure gas from the high pressure gas line 104 while the other chamber 312a, 312b is releasing or evacuating gas to the low pressure gas line 106. The first and second switches 500, 502 are spring-loaded pneumatic switches. In some examples, the first switch 500 is biased or defaulted its first state, and the second switch 502 is biased or defaulted to its second state, or vice versa.

[0044] In the illustrated example, the switching valve 334 includes a third switch 504. The third switch 504 provides pilot pressure to switch the first and second switches 500, 502 between their first and second states. The switching valve 334 has an air supply line 506 that provides compressed air from the compressed air line 222 to the end-of-stroke switches 336a, 336b and to the third switch 504. The third switch 504 is operable between a first state and a second state. In the first state, the third switch 504 fluidly couples the air supply line 506 to a pilot line 508 that causes the first and second switches 500, 502 to move their first and second states, respectively. In the second state, the third switch 504 vents the air in the pilot line 508, which enables the first and second switches 500, 502 to move back to their second and first states, respectively. When one of the end-of-stroke switches 336a, 336b is engaged, the engaged end-of-stroke switch 336a, 336b transmits a signal, in the form of high pressure air, to one pilot side of the third switch 504. This moves or switches the third switch 504 to one of its first or second states. As mentioned above, in the first state, high pressure air is supplied to the pilot 508 of the first and second switches 500, 502 to move to their first and second states, respectively. Then, when the other one of the end of stroke switches 336a, 336b is engaged, the switch 336a, 336b transmits another signal to the opposite pilot side of the third switch 504, such that the third switch 504 switches states. In the second state, the pilot line 508 is vented to the atmosphere, which enables the first and second switches 500, 502 to move back to their biased or default states. This process continues rapidly such that high pressure gas is injected into the first and second chambers 312a. 312b in an alternating manner to drive the drive piston 310 in a back-and-forth or reciprocating motion.

[0045] In some examples, one or more of the pumps 200-206 can be used to produce pressurized air for controlling / operating the various devices of the gas recovery' system 100. For example, as shown in FIG. 6, intake air 600 is provided to the first chamber 318a of the first pumping cylinder 304a. The first pumping cylinder 304a pressurizes the air and provides thepressurized air to the compressed air line 222, which is then distributed throughout the gas recovery system 200 (FIG. 2) and used to operate one or move devices such as the sensor 216 (FIG. 2), the sensing and pressure reducing valve 220 (FIG. 2), the valve 224 (FIG. 2), and / or the switching valves 334 associated with the pumps 200, 202, 204, 206. Therefore, in some examples, the gas recovery system 100 does not utilize or require pressurized air from the facility 102. Instead, the gas recovery system 100 can produce its own pressurized air. The example pump 200 can be configured in other arrangements where one or more of the chambers 318a, 318b, 326a, 326b are used to produce pressurized air, while one or more of the other chambers 318a, 318b, 326a, 326b are used to pump draw down gas.

[0046] In some examples, as shown in FIG. 6. a portion of the pressurized air is directed through 130 (e.g., a heat exchanger) and sprayed at the outside of the first pump 200 to help cool or reduce the temperature of the first pump 200.

[0047] "Including” and “comprising” (and all forms and tenses thereof) are used herein to be open ended terms. Thus, whenever a claim employs any form of "‘include” or ‘"comprise” (e.g., comprises, includes, comprising, including, having, etc.) as a preamble or within a claim recitation of any kind, it is to be understood that additional elements, terms, etc., may be present without falling outside the scope of the corresponding claim or recitation. As used herein, when the phrase “at least” is used as the transition term in, for example, a preamble of a claim, it is open-ended in the same manner as the term “comprising” and “including” are open ended. The term “and / or” when used, for example, in a form such as A. B, and / or C refers to any combination or subset of A, B, C such as (1) A alone, (2) B alone, (3) C alone, (4) A with B, (5) A with C, (6) B with C, or (7) A with B and with C. As used herein in the context of describing structures, components, items, objects and / or things, the phrase “at least one of A and B” is intended to refer to implementations including any of (1) at least one A, (2) at least one B, or (3) at least one A and at least one B. Similarly, as used herein in the context of describing structures, components, items, objects and / or things, the phrase “at least one of A or B” is intended to refer to implementations including any of (1) at least one A, (2) at least one B, or (3) at least one A and at least one B. As used herein in the context of describing the performance or execution of processes, instructions, actions, activities, etc., the phrase “at least one of A and B” is intended to refer to implementations including any of (1) at least one A, (2) at least one B, or (3) at least one A and at least one B. Similarly, as used herein in the context of describing the performance or execution of processes, instructions, actions, activities, etc., the phrase “at leastone of A or B” is intended to refer to implementations including any of (1) at least one A, (2) at least one B, or (3) at least one A and at least one B.

[0048] As used herein, singular references (e.g., “a”, ‘'an”, ‘"first”, “second”, etc.) do not exclude a plurality. The term “a” or “an” object, as used herein, refers to one or more of that object. The terms “a” (or “an”), “one or more”, and “at least one” are used interchangeably herein. Furthermore, although individually listed, a plurality of means, elements, or actions may be implemented by, e.g., the same entity or object. Additionally, although individual features may be included in different examples or claims, these may possibly be combined, and the inclusion in different examples or claims does not imply that a combination of features is not feasible and / or advantageous.

[0049] As used herein, connection references (e.g., attached, coupled, connected, and joined) may include intermediate members between the elements referenced by the connection reference and / or relative movement between those elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and / or in fixed relation to each other. As used herein, stating that any part is in “contact” with another part is defined to mean that there is no intermediate part between the two parts.

[0050] Unless specifically stated otherwise, descriptors such as “first,” “second,” “third,” etc., are used herein without imputing or otherwise indicating any meaning of priority, physical order, arrangement in a list, and / or ordering in any way. but are merely used as labels and / or arbitrary names to distinguish elements for ease of understanding the disclosed examples. In some examples, the descriptor “first” may be used to refer to an element in the detailed description, while the same element may be referred to in a claim with a different descriptor such as “second” or “third.” In such instances, it should be understood that such descriptors are used merely for identifying those elements distinctly within the context of the discussion (e.g., within a claim) in which the elements might, for example, otherw ise share a same name.

[0051] From the foregoing, it will be appreciated that example systems, methods, apparatus, and articles of manufacture have been disclosed that can be used to pump and / or otherwise transfer gas from a drawdown gas source to a gas discharge line. This prevents or reduces venting of natural gas to the atmosphere, which is wasteful and potentially harmful to the environment. The example gas recovery systems disclosed herein utilize a unique arrangement or configuration of pumps to ensure steady pumping and predictable drawdown times.

[0052] Examples and combinations of examples disclosed herein include the following:

[0053] Example 1 is a gas recovery' system comprising a drawdown gas supply line fluidly coupled to a drawdown gas source, a drawdown gas return line fluidly coupled to a gas discharge line, and a pumping system including: a first pump stage, the first pump stage to pump draw down gas from the draw down gas supply line to an interstage gas line; and a second pump stage arranged in series with the first pump stage, the second pump stage to pump the drawdow n gas from the interstage gas line to the drawdown gas return line such that the drawdown gas is transferred from the drawdown gas source to the gas discharge line.

[0054] Example 2 includes the gas recovery system of Example 1, wherein the first pump stage includes: a first pump; a second pump; and a third pump, wherein the first, second, and third pumps are arranged in parallel with each other, such that each of the first, second, and third pumps can pump the drawdown gas from the drawdown gas supply line to the interstage gas line.

[0055] Example 3 includes the gas recovery' system of Example 2, wherein the second pump stage includes a fourth pump.

[0056] Example 4 includes the gas recovery system of Example 3, wherein each of the first, second, and third pumps includes at least one pumping cylinder configured as a single acting piston pump.

[0057] Example 5 includes the gas recovery system of Example 4, wherein the fourth pump includes at least one pumping cycle configured as a double acting piston pump.

[0058] Example 6 includes the gas recovery system of Example 5, wherein the first, second, third, and fourth pumps are driven by differential gas pressure between a high pressure drive gas line and a low' pressure gas line.

[0059] Example 7 includes the gas recovery system of Example 6, wherein the gas discharge line is the low pressure gas line.

[0060] Example 8 includes the gas recovery system of Example 7, further including: a drive gas supply line to supply high pressure drive gas from the high pressure gas line to the first, second, third, and fourth pumps; and a drive gas return line to supply the high pressure drive gas from the first, second, third, and fourth pumps to the low pressure gas line.

[0061] Example 9 includes the gas recovery system of Example 8, wherein the draw dow n gas return line is fluidly coupled to the drive gas return line upstream of the low' pressure gas line.

[0062] Example 10 includes the gas recovery system of Examples 8 or 9, wherein the pumping system is operable between a gas driven mode in which high pressure natural gas isused to drive the first, second, third, and fourth pumps and an air driven mode in which high pressure air is used to drive the first, second, third, and fourth pumps.

[0063] Example 11 includes the gas recovery system of Example 10, further including: a first valve coupled to the drive gas supply line; and a compressed air line is fluidly coupled to the valve, the valve operable between a first state to supply high pressure drive gas through the drive gas supply line to drive the first, second, third, and fourth pumps, and a second state to supply high pressure air through the drive gas supply line to drive the first, second, third, and fourth pumps.

[0064] Example 12 includes the gas recover}7system of Example 11, further including a second valve coupled to the drive gas return line, wherein, in the air driven mode, the second valve is operated to vent air in the drive gas return line to the atmosphere.

[0065] Example 13 includes the gas recovery system of any of Examples 8-12, further including a first filter coupled the driving gas supply line.

[0066] Example 14 includes the gas recovery7system of Example 13, further including a second filter coupled to the drawdown gas supply line.

[0067] Example 15 includes the gas recovery system of any of Examples 1-14, further including a heat exchanger coupled to the draw dow n gas return line.

[0068] Example 16 is a gas recovery system for use in a facility having a high pressure gas line and a low pressure gas line. The gas recovery7system comprises a first pump; a second pump; a third pump, wherein the first, second, and third pumps are arranged in parallel and configured to pump drawdown gas from a draw down gas source to an interstage gas line; and a fourth pump arranged in series with the first, second, and third pumps, the fourth pump configured to pump the draw down gas from the interstage gas line to a gas discharge line, wherein the first, second, third, and fourth pumps are driven by differential gas pressure between the high pressure gas line and the low pressure gas line.

[0069] Example 17 includes the gas recovery system of Example 16, w herein the gas discharge line is the low pressure gas line.

[0070] Example 18 includes the gas recovery system of Examples 16 or 17, wherein each of the pumps includes a driving cylinder and two pumping cylinders.

[0071] Example 19 includes the gas recovery system of Example 18, wherein the pumping cylinders of the first, second, and third pumps are configured as single acting piston pumps, and the pumping cylinders of the fourth pump are configured as double acting piston pumps.

[0072] Example 20 includes the gas recovery system of any of Examples 16-19, wherein the gas recovery system does not include any electronic devices.

[0073] The following claims are hereby incorporated into this Detailed Description by this reference. Although certain example systems, methods, apparatus, and articles of manufacture have been disclosed herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all systems, methods, apparatus, and articles of manufacture fairly falling within the scope of the claims of this patent.

Claims

What Is Claimed Is:

1. A gas recovery system comprising: a drawdown gas supply line fluidly coupled to a drawdown gas source; a draw down gas return line fluidly coupled to a gas discharge line; and a pumping system including: a first pump stage, the first pump stage to pump drawdown gas from the drawdown gas supply line to an interstage gas line; and a second pump stage arranged in series with the first pump stage, the second pump stage to pump the drawdown gas from the interstage gas line to the drawdown gas return line such that the drawdown gas is transferred from the drawdown gas source to the gas discharge line.

2. The gas recovery' system of claim 1, wherein the first pump stage includes: a first pump; a second pump; and a third pump, wherein the first, second, and third pumps are arranged in parallel with each other, such that each of the first, second, and third pumps can pump the draw dow n gas from the drawdown gas supply line to the interstage gas line.

3. The gas recovery’ system of claim 2. wherein the second pump stage includes a fourth pump.

4. The gas recovery' system of claim 3, wherein each of the first, second, and third pumps includes at least one pumping cylinder configured as a single acting piston pump.

5. The gas recovery' system of claim 4, wherein the fourth pump includes at least one pumping cycle configured as a double acting piston pump.

6. The gas recovery' system of claim 5. wherein the first, second, third, and fourth pumps are driven by' differential gas pressure between a high pressure drive gas line and a low' pressure gas line.

7. The gas recovery' system of claim 6, wherein the gas discharge line is the low pressure gas line.

8. The gas recovery' system of claim 7, further including: a drive gas supply line to supply high pressure drive gas from the high pressure gas line to the first, second, third, and fourth pumps; and a drive gas return line to supply the high pressure drive gas from the first, second, third, and fourth pumps to the low pressure gas line.

9. The gas recovery’ system of claim 8, wherein the drawdown gas return line is fluidly coupled to the drive gas return line upstream of the low pressure gas line.

10. The gas recovery’ system of claim 8, wherein the pumping system is operable between a gas driven mode in which high pressure natural gas is used to drive the first, second, third, and fourth pumps and an air driven mode in which high pressure air is used to drive the first, second, third, and fourth pumps.

11. The gas recovery system of claim 10, further including: a first valve coupled to the drive gas supply line; and a compressed air hne is fluidly coupled to the valve, the valve operable between a first state to supply high pressure drive gas through the drive gas supply line to drive the first, second, third, and fourth pumps, and a second state to supply high pressure air through the drive gas supply line to drive the first, second, third, and fourth pumps.

12. The gas recovery system of claim 11, further including a second valve coupled to the drive gas return line, wherein, in the air driven mode, the second valve is operated to vent air in the drive gas return hne to the atmosphere.

13. The gas recovery system of claim 8, further including a first filter coupled the driving gas supply line.

14. The gas recovery system of claim 13, further including a second filter coupled to the drawdown gas supply line.

15. The gas recovery system of claim 1, further including a heat exchanger coupled to the drawdown gas return line.

16. A gas recovery system for use in a facility having a high pressure gas line and a low pressure gas line, the gas recovery system comprising: a first pump; a second pump; a third pump, wherein the first, second, and third pumps are arranged in parallel and configured to pump drawdown gas from a drawdown gas source to an interstage gas line; and a fourth pump arranged in series with the first, second, and third pumps, the fourth pump configured to pump the drawdown gas from the interstage gas line to a gas discharge line, wherein the first, second, third, and fourth pumps are driven by differential gas pressure between the high pressure gas line and the low pressure gas line.

17. The gas recovery system of claim 16, wherein the gas discharge line is the low pressure gas line.

18. The gas recovery system of claim 16, wherein each of the pumps includes a driving cylinder and two pumping cylinders.

19. The gas recovery7system of claim 18, wherein the pumping cylinders of the first, second, and third pumps are configured as single acting piston pumps, and the pumping cylinders of the fourth pump are configured as double acting piston pumps.

20. The gas recovery system of claim 16, wherein the gas recovery system does not include any electronic devices.

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