Field of the Disclosure

The present invention relates to a methane oxidation device for recovering heat for reuse in oxidation for reduction of global warming potential of methane.

Background

Gas wells are found in large numbers across the globe and leak a considerable amount of natural gas. Nearly three quarters of US gas wells leak natural gas. Methane forms 70-90% of the composition of natural gas. Methane is known to be a potent greenhouse gas, having a global warming potential that is considerably higher than that of carbon dioxide. It is vital to reduce methane emissions from natural gas leaks. Governments and companies alike are pushing to solve this issue.

There is also a need to identify gas well leaks, the severity of leaks, and to monitor leaks once any action has been taken.

Methane can be oxidised to water and carbon dioxide (CO2) which is less harmful to the atmosphere. Flaring is the controlled combustion of natural gas to reduce methane emissions and is known in the art. However, flaring requires methane purities between 5% and 15%, which is not the case for leaking wells. The natural gas is diluted as it leaks.

Away from the exact source of the leak, methane purities quickly drop below the lower combustion limit of 5%.

The energy demand required for oxidation of low purity methane is high and leaks often occur in remote areas where access to power is limited or unavailable. As such, there is a need to recover and reuse the energy used in the oxidation process.

Objects and aspects of the present invention seek to alleviate at least these problems with the prior art.

Summary

According to a first aspect of the invention, there is provided a methane oxidation device for oxidising methane emissions from gas wells, the methane oxidation device comprising; an enclosable chamber comprising an enclosable volume, the enclosable chamber comprising an inlet portion configured to allow fluid from the external environment to enter the enclosable chamber; a methane oxidation unit located within the enclosable chamber, the methane oxidation unit configured to oxidise methane located within the enclosable chamber, a heat exchanger for recovering heat for re-use in oxidation, the heat exchanger located within the enclosable chamber, the heat exchanger comprising; a heat exchanger inlet configured to receive fluid from the source of methane emissions or the methane oxidation unit; a heat exchanger outlet; at least one flow path fluidly connecting the heat exchanger inlet to the heat exchanger outlet; and at least one counter flow path, wherein the at least one counter flow path is the counter of the at least one flow path, the at least one counter flow path having at least a portion passing though the methane oxidation unit, in use, the at least one flow path and counter flow path are arranged to permit heat transfer therebetween; an outlet portion located on an external portion of the enclosable chamber, the outlet portion configured to allow fluid from the enclosable chamber to enter the external environment.

Energy from the oxidation of methane emissions is recovered and reused within the oxidation process. As such, the reliance on any external power source for this process can be reduced or nullified. This heat recovery allows a self-sustaining methane oxidation device to be provided. Such a device is advantageous, in particular, in applications where the device is used in remote areas.

The present invention allows the oxidation of methane at lower purities than required for flaring. In this way, leaks which have diluted to below 5% methane purities can be oxidised and so the leak does not need to be treated at the exact location of the leak. The present invention allows for the oxidation of methane at levels of 200ppm to 30,000ppm.

The enclosable chamber encompasses the area about the gas leak such that the user does not need to locate the precise source of the leak. Preferably, the enclosable chamber comprises, for example, a dome, a tent, a rigid housing, a substantially cuboid box or any suitable structure.

In some embodiments, the methane oxidation unit comprises an oxidation chamber for catalytic oxidation of methane and the oxidation chamber comprises at least a portion of the enclosable chamber. The catalytic material promotes the oxidation of methane and is particularly advantageous when the methane purity level is low, such as in natural gas leaks. In particular, use of a catalytic material is advantageous when the methane concentration is below the level of flammability. Using catalytic material lowers the temperature required for oxidation and therefore lowers the energy demand for the oxidation process and the overall energy demand of the methane oxidation device.

In some embodiments, the methane oxidation unit comprises at least one catalytic material located within the heat exchanger. The oxidation of methane occurs within the heat exchanger, removing the need for a separate oxidation chamber. The catalytic material promotes the oxidation of methane, lowering the temperature required for oxidation. As the methane oxidation occurs within the heat exchanger, a greater amount of the energy released in the reaction can be recovered by the heat exchanger.

Preferably, the at least one catalytic material is located within at least one of the at least one flow path and/or the at least one counter flow path. Herein, the oxidation of methane occurs within the active portion of the heat exchanger and a greater amount of the energy released in the reaction can be recovered by the heat exchanger.

Preferably, the at least one catalytic material comprises a noble metal or a base metal. Alternatively, the at least one catalytic material consists of a noble metal or a base metal.

Preferably, the methane oxidation device comprises a heater unit configured to heat at least a portion of the heat exchanger. The heater unit can be configured to heat at least a portion of the heat exchanger to initiate the oxidation. The heater unit can be configured to increase the temperature by induction, resistance or any other suitable heating means. Preferably, the methane oxidation device comprises at least one temperature sensor. Preferably, the at least one temperature sensor is configured to detect the temperature in at least a portion of the heat exchanger. More preferably, the at least one temperature sensor is configured to detect when the temperature in at least a portion of the heat exchanger falls below a threshold temperature. Preferably, the methane oxidation device is configured to re-engage the heater unit with energy from an external source when the temperature in at least a portion of the heat exchanger falls below a threshold temperature. Preferably, the heater unit is configured be re-engaged automatically when the temperature in at least a portion of the heat exchanger falls below a threshold temperature. In this way, the methane oxidation device monitors and responds when the temperature in the heat exchanger falls below a threshold temperature, for example the minimum temperature required for oxidation.

In some embodiments, the methane oxidation unit is located between the inlet portion of the enclosable chamber and the heat exchanger and the heat exchanger is located between the methane oxidation unit and the outlet portion of the enclosable chamber. The fluid can flow through the inlet portion and into the methane oxidation unit wherein the methane in the air flow is oxidised and heat is released in the exothermic reaction. The post-oxidation fluid then flows through the heat exchanger, where the heat released in the reaction can be transferred via heat exchange in the heat exchanger, and exit out the outlet portion. In this way, energy is recaptured and can be re-used within the device.

Preferably, the outlet portion of the enclosable chamber is located distal the inlet portion of the enclosable chamber. In this way, there is a lower risk of methane exiting the enclosable chamber via the outlet portion before oxidation occurs.

Preferably, an unenclosed surface of the enclosable chamber comprises the inlet portion. An unenclosed surface is an opening spanning an area which could form a surface of the enclosable chamber. For example, the unenclosed surface can be the base of a dome. The enclosable chamber can then be placed over a methane source via the unenclosed surface, for example by placing the enclosed surface over a leaking pipe or joint. The exact source of the leak does not need to be located precisely, allowing the user to fit the device with greater ease and speed.

Preferably, the methane oxidation device comprises at least one temperature sensor located within the enclosable chamber. The temperature sensor can be used as an indicator of catalytic activity. The oxidation of methane is exothermic and so when oxidation is occurring, the temperature in and around the catalyst area will be higher than when oxidation is not occurring. A decrease in temperature could indicate that the oxidation has slowed or stopped. A decrease in the rate of oxidation could indicate that the levels of methane being released have reduced or that there is a problem with the oxidation process. More preferably, the temperature sensor is located proximate the catalytic material. Preferably, the methane oxidation device comprises at least two temperature sensors located within the enclosable chamber. Preferably, one of the temperature sensors is located proximate the catalytic material and one of the temperature sensors is located proximate the inlet portion or the outlet portion of the methane oxidation device. In this way, the temperature difference between the catalytic material and the external environment temperature can be calculated and used as an indicator of catalytic activity.

Preferably, the methane oxidation device comprises at least one pressure sensor located within the enclosable chamber. Preferably, a pressure sensor is located within the heat exchanger. Preferably, a pressure sensor is located proximate the catalytic material. The fluid heated by oxidation will have a higher pressure and therefore pressure can be used as an indicator of catalytic activity alone or alongside temperature.

Preferably, the methane oxidation device comprises at least one methane sensor located within the enclosable chamber. Preferably, at least one methane sensor is located proximate the inlet portion of the enclosable chamber. The methane sensor can be configured to measure the concentrations of methane entering the device and monitor the methane leak from the leak source.

Preferably, the methane oxidation device comprises at least one carbon dioxide (CO2) sensor located within the enclosable chamber. Preferably, a CO2 sensor is located proximate the outlet portion of the enclosable chamber. CO2 is produced by the oxidation of methane. The CO2 sensor can be used to map the activity of the catalyst and monitor methane oxidation. Preferably, the methane oxidation device comprises at least two CO2 sensors located in the enclosable chamber. Preferably, one of the CO2 sensors is located proximate the outlet portion of the enclosable chamber and one of the CO2 sensors is located proximate the inlet portion of the enclosable chamber. In this way, the difference in CO2 levels can be calculated and used to monitor methane oxidation.

Preferably, the device is configured to send data from the at least one temperature sensor, the at least one pressure sensor, the at least one methane sensor and/or the at least one CO2 sensor is to an external gateway device via at least one of long range (LoRa), radio frequency (RF), Bluetooth low energy (BLE) and Wi-Fi. The data can be accessed remotely via, for example, cloud storage. The data can be used to quantify and track methane oxidation at leak sites. The data can be reviewed, allowing the user to track catalytic activity and possibly alerting the user to any problems. Preferably, the gateway is located proximate the leak. Preferably, the gateway is located up to 10 km away from the leak. Preferably, the gateway is located up to 8 km away from the leak. Preferably, the gateway is located up to 5 km away from the leak. Connectivity via internet of things (IOT) will bring transparency to the emissions reductions efforts and help companies and governments remain aware and informed on the leaks and the mitigation strategy.

Preferably, the outlet portion of the enclosable chamber is coupled to the heat exchanger outlet to allow fluid exiting the heat exchanger outlet to enter the external environment. Preferably, the outlet portion restricts fluid passage to substantially one direction. In this way, the cooled post oxidation fluid leaving the heated exchanger exits directly to the external environment, minimising the amount of energy leaving the system and preventing the post oxidation fluid from re-entering the oxidation unit.

Preferably, the heat exchanger is tightly fitted to the enclosable chamber. Preferably, the heat exchanger is tightly fitted to the enclosable chamber using an airtight gasket fitting. In this way, fluid within the device cannot leak out without being directed through the desired flow paths.

Preferably, a portion of the at least one counter flow path is substantially parallel to a portion of the at least one flow path. In this way, a parallel flow heat exchanger is provided and the resistance to heat transfer between the flow path and counter flow path, and vice versa, is substantially identical along the length of the flow path and counter flow path.

Preferably, the heat exchanger comprises multiple flow paths and counter flow paths. In this way, efficient heat transfer from the heated post-oxidation fluid to the cooler incoming fluid is provided.

Preferably, the heat exchanger inlet comprises a heat exchanger inlet manifold and the heat exchanger outlet comprises a heat exchanger outlet manifold. In this way, the surface area for heat exchange is increased.

Preferably, the methane oxidation device is configured to minimise the pressure loss. Preferably, the device comprises a receiving rim which can be sunk into the ground. The enclosable chamber can then be fitted to the rim to secure the oxidation device in place over the leak. In this way, pressure loss through the enclosable chamber inlet is minimised.

Preferably, the methane oxidation device comprises an insulation unit configured to insulate the methane oxidation device to reduce heat loss to the external environment. Preferably, the insulation unit comprises at least one of basalt wool fibre insulation, aerogel, expanded polymer and/or glass fibre. It is understood that any suitable insulation may be used.

Minimising heat loss will minimise the external energy required for oxidation. Preferably, the insulation unit is configured to insulate the heat exchanger. By reducing the heat loss, the insulation unit reduces the need for external energy to maintain the temperature required for oxidation.

Preferably, the heat exchanger outlet faces an opposing direction to the heat exchanger inlet. Preferably, the heat exchanger outlet faces the external environment and the heat exchanger inlet faces the source of the leak. In this way, the chance of post-oxidation fluid re-entering the heat exchanger is reduced.

Preferably, the inlet portion and the outlet portion are substantially the only apertures of the enclosable chamber. In this way, fluid can only leave the enclosable chamber via the outlet portion, reducing the likelihood of fluid leaving the chamber without passing through the methane oxidation unit.

In some embodiments, the methane oxidation device comprises a plurality of heat exchangers. The heat exchangers may be configured with two or more in series, with the inlet of one heat exchanger feeding into the outlet of another heat exchanger, reducing the pressure loses due to any piping and fitting requirements and increasing the heat transfer efficiency. Alternatively, the plurality of heat exchangers may be located at multiple locations. In such cases, each heat exchanger comprises an outlet coupled to an outlet of the enclosable chamber. In this way, the enclosable chamber comprises a plurality of exits to external environment. In this way, if one exit is blocked, the methane oxidation device can still function.

Preferably, the heat exchanger is a recuperative heat exchanger and/or a regenerative heat exchanger. Preferably, the heat exchanger is a single pass heat exchanger.

Preferably, the methane oxidation device comprises fixing means for fixing the enclosable chamber about a source of methane emissions. It is understood that the term about encompasses enclosing the enclosable chamber directly around, over or entirely encompassing the source of methane emissions. Additionally, about may refer to location of the device over a surface, such as the ground, surrounding and including the source of methane emissions. Preferably, the fixing means comprises at least one of, magnetic, push fit, adhesive, pegs. In this way, the oxidation device is airtight and securely fixed about the source of methane emissions and the fluid from the leak follows the desired flow paths through the device.

Preferably, the methane oxidation device comprises a pump unit for assisting fluid flow through the methane oxidation device, in use. In this way, there is greater ease fluid flow within the device.

Preferably, the methane oxidation device comprises an emission separator unit for, in use, separating the emissions based on at least one emission characteristic. Preferably, the emission characteristic is the methane purity, the temperature, and/or the pressure.

Preferably, the emission characteristic is the methane purity. The emission separator may separate the fluid prior to entering the heat exchanger. In this way, the methane emissions can be filtered such that have low-purity emissions bypass the heat exchanger and high- purity emissions enter the heat exchanger. In some embodiments, the device comprises a valve in fluid communication with the external environment. In this way, the device may be configured such that all leaks with a methane purity below a certain level bypass the exchanger via a valve, and those over that level flow into the heat exchanger, in use. Separating the emissions by methane purity reduces the quantity of low-methane emissions undergoing oxidation, consequently improving energy generation from the oxidation process and reducing the quantity of undesirable cooling of fluid prior to oxidation.

Construction techniques which can be used to form the heat exchange include but are not limited to cutting repeated sections stacked or fused together using existing diffusion bonding techniques, welding, brazing and mechanical fastening with gaskets.

Brief Description of the Drawings

Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:

Figure 1 depicts a view of the methane oxidation device in accordance with the present invention positioned over a gas source, in use;

Figure 2 depicts a deconstructed view of the heat exchanger of the device of Figure 1 ;

Figure 3 depicts a view of a second embodiment of the methane oxidation device, positioned over a gas source in use; and

Figure 4 depicts a view of a third embodiment of the methane oxidation device, positioned over a gas source in use.

Detailed Description

With reference to Figure 1 there is illustrated a methane oxidation device 100 for oxidising methane emissions from gas well leaks, in use, mounted on a gas source. The oxidation device 100 comprises an enclosable dome 101 , with the enclosable dome 101 further comprising an inlet portion 102, a heat exchanger 200 and an outlet portion 103. The device 100 is configured to enclose a source of methane emissions, namely gas pipe 104. The arrows show that the fluid flows from the source 104 in direction A, through the inlet portion 102 to the heat exchanger unit 200 in direction B, where the methane in the fluid flow is oxidised to carbon dioxide and water. The oxidised fluid exits the enclosable dome 101 in direction C via the outlet portion 103.

The inlet portion 102 comprises an unenclosed surface 110 of the enclosable chamber 101. The inlet portion 102 is configured to enclose sections of pipe 104, such that the exact location of the leak does not need to be identified.

The heat exchanger 200 is tightly fitted to the enclosable chamber 101 using an airtight gasket fitting.

With reference to Figure 2 there is illustrated a heat exchanger 200 comprising an inlet 202, a flow path 203 entering an oxidation unit 204, the oxidation unit 204, a counter flow path 205 exiting of the oxidation unit and an outlet 206. The heat exchanger outlet 206 is coupled to the outlet portion 103 of the enclosable chamber 101 of the methane oxidation device 100. Fluid exiting the heat exchanger 200 enters directly into the external environment rather than remaining in the enclosable chamber 101 and returning to mix with the volume of non-oxidised fluid.

The flow path 203 is parallel to the counter flow path 205 and the length of the flow path 203 is identical to the length of the counter flow path 205. Fluid enters the heat exchanger at the temperature of the external environment. Fluid leaves the oxidation unit 204 heated by the energy released in the oxidation reaction. The heated post-oxidation fluid passes through the counter flow path 205 and the heat released from the oxidation reaction is transferred to the incoming fluid passing through the flow path 203. The heat exchanger 200 comprises multiple flow paths 203 and multiple counter flow paths 205 to increase the surface area for efficient heat exchange.

The oxidation unit 204 comprises a catalytic material comprising a noble metal which catalyses the oxidation of methane. The heat exchanger 200 is located at the top of the enclosable dome 101. The outlet 103 faces an opposing direction to the heat exchanger inlet 202. The outlet faces the external environment and the heat exchanger inlet faces the fluid source.

The heat exchanger 200 comprises 304 stainless steel.

With reference to Figure 3 there is illustrated a second embodiment of the methane oxidation device 300 of the present invention, for oxidising methane emissions from gas well leaks, in use, mounted on over a gas source. For this embodiment, similar reference numerals are used for similar parts of an embodiment of the present invention.

The oxidation device 300 comprises an enclosable chamber 301, with the enclosable chamber 301 further comprising an inlet portion 302, a heat exchanger 200 and an outlet portion 303. The fluid flows through the inlet portion 302 to the heat exchanger unit 200, where the methane is oxidised to carbon dioxide and water, and then out the outlet portion 303.

The inlet portion 302 is an unenclosed surface 310 of the enclosable chamber 301. The inlet portion covers sections of pipe 304, so that the exact location of the leak does not need to be identified.

The heat exchanger 200 is tightly fitted to the enclosable chamber 301 using an airtight gasket fitting.

The device further comprises a heater unit 305 proximate the catalytic material, an insulation unit 306 surrounding the heat exchanger 200, a temperature sensor 307 proximate the catalytic material, a CO2 sensor 308 proximate the outlet 303 and a methane sensor 309 proximate the inlet 302.

The heater unit 305 heats the heat exchanger 200 and the catalytic material within it to initiate the oxidation of methane. Once the methane oxidation has started, the heater unit 305 stops heating and the oxidation process is self-sustained by the heat produced in the reaction. If the temperature falls below that required for methane oxidation, the heater reactivates automatically.

The insulation unit 306 surrounds the heat exchanger 200 to reduce heat loss. The insulation unit can be made of basalt wool fibre insulation, aerogel, expanded polymer or glass fibre. The temperature sensor 307 measures the temperature around the catalytic material in order to monitor catalytic activity. The CO2 sensor 308 measures the CO2 levels at the outlet to monitor catalytic activity. The methane sensor 309 measure the methane levels at the inlet 302 to measure the levels of methane entering the device to track the leak.

With reference to Figure 4 there is illustrated a methane oxidation device 400 for oxidising methane emissions from gas well leaks, in use, mounted on over a gas source.

The oxidation device 400 comprises an enclosable chamber 401, with the enclosable chamber 401 further comprising an inlet portion 402, a methane oxidation unit 406, a heat exchanger 405 and an outlet portion 403. The fluid flows through the inlet portion to methane oxidation unit 406, where the methane is oxidised to carbon dioxide and water, to the heat exchanger unit 405, and then out the outlet portion 403.

The heat exchanger 405 is tightly fitted to the enclosable chamber 401 using an airtight gasket fitting. The heat exchanger 405 consists of 304 stainless steel or aluminium. The outlet 403 faces an opposing direction to the heat exchanger inlet.

The oxidation unit 406 comprises a catalytic material such as a noble metal which catalyses the oxidation of methane.

The inlet portion 402 is an unenclosed surface 410 of the enclosable chamber 401. The inlet portion covers sections of pipe 404, so that the exact location of the leak does not need to be identified.

The invention is not limited to the specific examples or structures illustrated, a greater number of components than are illustrated in the Figures could be used, for example.