Processes and systems for the removal of nitrogen from natural gas

Abstract

A process 100 for the removal of nitrogen from natural gas 102 is described. The process 100 comprises a) providing a feed stream 102 comprising natural gas, wherein the natural gas comprises at least

Description

FIELD

[0001] The present disclosure relates to processes and systems for the removal of nitrogen from natural gas. BACKGROUND

[0002] Natural gas is a mixture of gases comprising primarily methane along with small amounts of higher alkanes, and for example, carbon dioxide, nitrogen, hydrogen sulfide, and helium. The composition of the natural gas mixture varies depending upon the source.

[0003] Natural gas recovered from a source (such as a well or reservoir) typically requires further processing to achieve an acceptable purity of methane in order to be utilized. Known processes for the production of high purity methane gas streams are, for example, based on membrane separation systems, pressure swing-adsorption units (PSA), or vacuum swingadsorption units (VSA).

[0004] The membrane separation systems typically require the use of stand-alone membrane units. The production of high purity methane streams (for example, comprising greater than 96 mol% methane) using membrane separation systems is considered to be inefficient because the processes usually require large membrane areas, and corresponding high power demands.

[0005] PSA and VS A units, on the other hand, are considered to be very efficient in producing a high purity methane stream, particularly from feed streams which, for example, contain methane at concentrations of greater than 70 mol %. However, these processes are less efficient at yielding high purity product streams at a high rate of recovery when the feed stream has relatively low purity, for example less than 70 mol% methane.

[0006] These known separation process are also considered to inefficient for removing nitrogen from the natural gas mixture Cryogenic distillation can also be used to remove nitrogen, however, this process is very energy intensive and is typically employed for liquified natural gas (LNG) production.

[0007] Therefore, a need exists to provide improved methods for the treatment of natural gas in order to provide natural gas product streams having a desired methane purity, with a high rate of recovery. SUMMARY

[0008] According to a first aspect of the present disclosure, there is provided a process for the removal of nitrogen from natural gas, the process comprising: a) providing a feed stream comprising natural gas, wherein the natural gas comprises at least a gaseous mixture of methane and nitrogen; b) supplying the feed stream to a separator, wherein the separator comprises a membrane separator having nitrogen-methane selectivity and the membrane separator being configured to allow nitrogen to permeate through the membrane; and c) separating the components of the feed stream using the separator into a product retentate stream comprising methane, and a nitrogen waste permeate stream.

[0009] The process of the present disclosure provides an efficient process for obtaining methane product streams with a desired purity by effectively removing nitrogen from a feed stream comprising natural gas. The process utilizes a membrane-based separation process that can be applied to both onshore and offshore natural gas processing facilities. Furthermore, the proposed processes are less energy intensive than, for example, existing cryogenic distillation processes.

[0010] The product retentate stream may comprise at least about 96 mol% methane. The product retentate stream may comprise at least about 99 mol% methane. Current export specifications for natural gas require the natural gas to comprise no more than 4 mol % nitrogen. The process may comprise providing a feed stream comprising natural gas, wherein the natural gas composition comprises from about 4 mol % to about 80 mol % nitrogen, or from 4 mol % to about 50 mol% nitrogen, or from about 4 mol% to about 10 mol % nitrogen.

[0011] The process may comprise maintaining a pressure of the product retentate stream at a pressure of the feed stream. The process may comprise an operating pressure, wherein the operating pressure is the pressure of the feed stream, and an operating pressure of separator, wherein the product retentate stream is maintained at the operating pressure. The operating pressure may comprise a pressure of from about 0 bar to about 250 bar. The operating pressure may comprise a pressure of from about 10 bar to about 150 bar. The operating pressure may comprise a pressure of from about 20 bar to about 80 bar. Maintaining the operating pressure across the membrane separator may facilitate the permeation of nitrogen through the membrane separator whilst also allowing energy savings to be made compared to existing processes which may require higher operating pressures.

[0012] The process may comprise operating the separator at an operating temperature of from about 0 °C to about 100 °C, or from about 5 °C to about 70 °C, or from about 10 °C to about 50 °C.

[0013] The process may comprise maintaining the pressure of the feed stream and the product retentate stream at a pressure required for exporting natural gas. This may provide for energy efficiencies to be made during the process, and reduce capital expenditure on the process by minimizing the requirement for ancillary processing and equipment. Existing processes typically utilize membrane separations based on methane selectivity with the methane being recovered on a low pressure side of the membrane separator. In contrast, the present process uses membranes having nitrogen-methane selectively, permitting the methane to be recovered on a high pressure side of the membrane.

[0014] The process may comprise supplying the nitrogen waste permeate stream to a nitrogen adsorption unit and producing an adsorption product stream comprising methane, and an adsorption waste stream comprising nitrogen. This process step facilitates further removal of nitrogen from the natural gas, improving the methane recovery rate for the process.

[0015] The nitrogen adsorption unit may comprise at least one of a pressure swing adsorption system, or a vacuum swing adsorption system. The pressure swing adsorption and / or vacuum swing adsorption systems may comprise multiple adsorption beds.

[0016] The process may comprise disposing of the waste permeate stream. Disposing may comprise injecting the waste permeate stream into a well, for example, a natural gas production well. Disposing may comprise exporting the waste permeate stream for subsequent use. The process of the present disclosure provides to minimize the amount of methane within the nitrogen waste permeate stream, and as such, the disposal of the wastes permeate stream is more environmentally friendly compared to, for example, current off-gas processes. When the process comprises injecting the waste permeate stream into a well, the process may be considered to be a zero or minimal emissions process.

[0017] The process may further comprise recycling the product retentate stream back to the separator. Recycling the product retentate stream may improve the rate of recovery of methane and the nitrogen removal rate of the process.

[0018] The membrane separator may have a nitrogen / methane selectivity of equal to or greater than about 10. The membrane may comprise an inorganic membrane The membrane separator may comprise a hollow fiber membrane separator comprising a plurality of membrane hollow fibers. The membrane separator may comprise a membrane unit comprises a plurality of membrane hollow fibers. The membrane unit may comprise a plurality of membrane hollow fibers having a packing density of about 10,000 m2 / m3, or about 20,000 m2 / m3, or about 30,000 m2 / m3, or about 40,000 m2 / m3, or about 50,000 m2 / m3, or any intermediate packing density value.

[0019] The separator may comprise a multi-stage membrane process which includes a plurality of membrane stages arranged in series, such that a product retentate stream (comprising methane) is produced from each membrane stage. A waste permeate stream (comprising nitrogen) from each membrane stage may be fed to subsequent membrane stages until a final membrane stage, wherein a final waste permeate stream may be disposed of. Any number of stages of membrane units may be arranged in series according to the desired application. For example, 1, 2, 3, 5, up to and including 10, or up to and including 20 membrane stages, up to and including n-membrane stages, wherein each waste permeate stream may be supplied to a subsequent membrane stage until the nth membrane stage, where the nth waste permeate stream may be disposed of. Each stage may comprise a plurality of hollow fiber membranes.

[0020] The separator may comprise a multi-stage membrane process having a first membrane stage with nitrogen-methane selectivity and a second membrane stage with nitrogen-methane selectivity. The process may comprise the nitrogen from the feed stream permeating through the first membrane stage and producing a first product retentate stream and a first waste permeate stream. The first waste permeate stream may be supplied to the second membrane stage wherein the nitrogen from the first waste permeate stream permeates through the second membrane stage, producing a second product retentate stream and a second waste permeate stream.

[0021] The first membrane stage may comprise a membrane with a nitrogen / methane selectivity of about 7. The first membrane stage may comprise a nitrogen permeance of equal to or more than 2500 GPU. The second membrane stage may comprise a membrane with a nitrogen / methane selectivity of about 10. The second membrane stage may comprise a nitrogen permeance of about 1500 GPU. Use of membranes having these selectivity and permeance values may allow for the footprint (i.e. the area) of the separating process to be reduced compared to existing membrane separation processes.

[0022] The process may further comprise recycling a product retentate stream (for example, from a first, second, subsequent or nth membrane stage) to the first membrane stage. This can provide for improved rates of nitrogen removal and methane recovery.

[0023] The process may comprise supplying the second waste permeate stream, or a subsequent waste permeate stream (for example, from a second, third, subsequent or nth membrane stage) to a nitrogen adsorption unit and producing a methane product stream, and an adsorption waste stream comprising nitrogen.

[0024] The process may comprise supplying the second product retentate stream, or subsequent product retentate stream (for example, from a second, third, subsequent or nth membrane stage) to a nitrogen adsorption unit and producing a methane product stream, and an adsorption waste stream comprising nitrogen.

[0025] The processes described herein are compact and modular by design. That is to say the membranes having the required selectivity require relatively small areas compared to existing membrane systems and compared to existing cryogenic distillation processes. The composition of natural gas is dependent upon the source of natural gas, and the processes for removing nitrogen from natural gas as outlined in this disclosure allow for the processes to be adapted as required, for example utilizing combination of membranes and nitrogen adsorption units, or including a recycle loop or including a multi-stage membrane process.

[0026] The process may further comprise compressing the methane product stream produced from the nitrogen adsorption unit. The process may comprise combining the methane product stream produced from the nitrogen adsorption unit with the product retentate stream. The process may comprise supplying the combined methane produce stream to a natural gas export pipeline.

[0027] The process may further comprise pre-treating the feed stream prior to supplying the feed stream to the separator. Pre-treating comprises at least one of: changing the temperature of the feed stream, changing the pressure of the feed stream, removing higher alkanes and other contaminants from the natural gas. The process may comprise treating the feed stream comprising natural gas to provide a feed stream having a natural gas composition which may comprise from about 4 mol % to about 80 mol % nitrogen, or from 4 mol % to about 50 mol% nitrogen, or from about 4 mol% to about 10 mol % nitrogen.

[0028] According to a second aspect of the disclosure, there is provided a system configured to perform the process according to the first aspect, the system comprising a separator, wherein the separator comprises a membrane separator having nitrogen-methane selectivity and the membrane separator is configured to allow nitrogen to permeate through the membrane.

[0029] The separator may comprise a multi-stage membrane separator.

[0030] The system may further comprise a nitrogen adsorption unit arranged to be supplied by at least one of a waste permeate stream and product retentate stream from the membrane separator. The nitrogen adsorption unit may comprise at least one of a pressure swing adsorption system or a vacuum swing adsorption system.

[0031] According to a third aspect of the disclosure, there is provided a methane process stream produced according to the processes of the first aspect, or the systems of the second aspect. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0032] The above and other characteristics will become clear from the following description of illustrative, non-restrictive examples, with reference to the attached drawings, in which:

[0033] FIG. 1 is a schematic flow diagram of a single stage membrane separation process according to a process of the present disclosure;

[0034] FIG. 2 is a schematic flow diagram of a two stage membrane separation process according to a process of the present disclosure;

[0035] FIG. 3 is a schematic flow diagram of a single stage membrane and adsorption separation process according to a process of the present disclosure;

[0036] FIG. 4 is a schematic flow diagram of a two stage membrane separation process comprising a recycle loop according to a process of the present disclosure;

[0037] FIG. 5 is a schematic flow diagram of a two stage membrane separation and adsorption separation process according to a process of the present disclosure;

[0038] FIG. 6 is a schematic flow diagram of a single stage membrane separation process according to a process of the present disclosure; and

[0039] FIG. 7 is a schematic flow diagram of two stage membrane separation process of according to the present disclosure. DETAILED DESCRIPTION

[0040] The present disclosure relates to improved processes and systems for the removal of nitrogen from nitrogen-methane mixtures, particularly natural gas. Although, it will be appreciated that other gaseous mixtures comprising methane and nitrogen can be processed according to the methods disclosed herein. The processes described herein are suitable for use with both onshore and offshore natural gas processing facilities.

[0041] Figure 1 shows a schematic flow diagram of a single stage membrane separation process 100 according to the processes of the present disclosure. In this example, a natural gas feed stream 102 is pretreated in a pretreatment process 104 to remove higher alkanes and other contaminants from the natural gas feed stream 102. The pretreatment process 104 may also include compressing the natural gas feed stream 102 to a pressure required for the membrane separation process. For example, the membrane separation may be carried out at operating pressure of from 0 bar to 250 bar, or from about 10 to 150 bar, or from about 20 to 80 bar. The membrane separation can be carried out at an operating temperature of from about 0 °C to about 100 °C, or from about 5 °C to about 70 °C, or from about 10 °C to about 50 °C.

[0042] The resulting treated feed stream 105 comprises a composition comprising from about 4 mol % to about 80 mol % nitrogen, or from 4 mol % to about 50 mol% nitrogen, or from about 4 mol% to about 10 mol % nitrogen Feed stream 105 is supplied to a single stage membrane unit 106. The membrane unit 106 can comprise any membrane with a nitrogen / methane selectivity equal to or greater than about 10. Examples of such membranes include inorganic hollow fiber membranes. The membrane unit 106 in this example comprises a single membrane stage. The single membrane stage can comprise a plurality of hollow fiber membranes. For example, inorganic hollow fiber membranes having the required N2 / CH4 selectivity can be utilized. The hollow fiber membranes can have a packing density of about 30,000 m2 / m3. The feed stream 105 is supplied to the membrane unit 106, and permeation of nitrogen through the membrane unit 106 occurs resulting in the production of a waste permeate stream 110 comprising nitrogen. A product retentate stream 108 comprises at least about 96 mol% methane, or about 99 mol % methane is also produced. The product retentate stream 108 can be exported directly to a natural gas pipeline. In this example, the waste permeate stream 110 is injected back into a well 112, or otherwise disposed of.

[0043] Figure 2 shows a schematic of a two-stage membrane separation process 200 according to the processes of the present disclosure. Natural gas 202 is pretreated in a pretreatment process 204 to remove, for example higher alkanes and other contaminants. The resulting feed stream 205 comprises a composition comprising from about 4 mol % to about 80 mol % nitrogen, or from 4 mol % to about 50 mol% nitrogen, or from about 4 mol% to about 10 mol % nitrogen. Feed stream 205 is supplied to first stage membrane unit 206a. The process 200 comprises maintaining a pressure across the first stage membrane unit 206a (for example, a pressure of from about 0 bar to about 250 bar) resulting in the permeation of nitrogen through the first stage membrane unit 206a to produce a first waste permeate stream 210a comprising nitrogen. The membrane separation can be carried out at an operating temperature of from about 0 °C to about 100 °C, or from about 5 °C to about 70 °C, or from about 10 °C to about 50 °C.

[0044] A first product retentate stream 208a is also produced and comprises at least 96 mol% methane, or about 99 mol% methane. The first product retentate stream 208a can be exported directly to a natural gas pipeline 214.

[0045] In this example, the first waste permeate stream 210a is compressed via compressor 211 and supplied to a second membrane stage 206b for further nitrogen removal. The second membrane stage 206b produces a second product retentate stream 208b and a second waste permeate stream 210b. The process 200 then recycles the second product retentate stream 208b back to the first membrane stage 206a. The recycling process can comprise compressing the second product retentate stream 208b using a compressor 213 to the desired operating pressure for the first membrane stage 206a. The compressed second product retentate stream 209 can be combined with the pre-treated feed stream 205 prior to being supplied to the first membrane stage 206a. The provision of such a recycle loop from the second stage allows for more effective nitrogen removal during the first stage membrane unit 206a. The second waste permeate stream 210b from the second stage membrane unit 206b is injected back into a well 212, or otherwise disposed of.

[0046] The skilled person will appreciate that any number of stages of membrane units may be arranged in series according to the desired application, for example depending on the composition of the natural gas obtained from the source of natural gas. For example, 1, 2, 3, 5, up to and including 10, or up to and including 20 membrane stages, or up to and including n-membrane stages, wherein each waste permeate stream is supplied to a subsequent membrane stage until the nth stage, where the nth waste permeate stream is injected into a well or otherwise disposed of.

[0047] In case of two membrane stages, first stage membrane unit 206a can have a N2 / CH4 selectivity equal or higher than about 7 and N2 permeance of equal to or higher than 2500 GPU (Gas permeance unit). The second stage membrane unit 206b can have a N2 / CH4 selectivity equal to or higher than about 10 and N2 permeance of 1500 GPU. Each membrane unit 206a, 206b comprises a single membrane. Examples of such membranes include inorganic, hollow fiber membranes. The hollow fiber membranes can have a packing density of about 30,000 m2 / m3.

[0048] Figure 3 shows a schematic flow diagram of a single stage membrane separation and adsorption process 300 according to the processes of the present disclosure. The process 300 is the same as that described for Figure 1 and like numerals are used to denote like features incremented by 200. In this example, the waste permeate stream 310 from the membrane separator 306 is fed to a nitrogen adsorption unit 320 for further removal of the nitrogen from the waste permeate stream 310. Example nitrogen adsorption units include multi-bed pressure swing adsorption systems or vacuum swing adsorption systems. The recovered nitrogen waste stream 322 from the adsorption unit may be injected into a well 312, or otherwise disposed of. The adsorption product stream 324 comprises methane and is compressed via a compressor 325 then combined with the product retentate stream 308 from the membrane separation unit 306. The resulting methane product stream 309 can be exported directly to a natural gas pipeline 314.

[0049] Figure 4 shows a schematic flow diagram of a two stage membrane separation and adsorption process 400 according to the processes of the present disclosure. The process 400 is the same as that described in process 200 shown in Figure 2, and like numerals are used to denote like features incremented by 200. In this process 400, the waste permeate stream 410b from the second membrane stage 406b is fed to a nitrogen adsorption unit 420 for further removal of the nitrogen from the waste permeate stream 410b. Example nitrogen adsorption units include multibed pressure swing adsorption systems or vacuum swing adsorption systems. The recovered nitrogen waste stream 422 from the adsorption unit 420 may be injected into a well 412, or otherwise disposed of. The resulting adsorption product stream 424 is compressed via a compressor 425 then combined with the first product retentate stream 408a from the first stage membrane unit 306a. The combined product stream 409 can be exported directly to a natural gas pipeline. In the same manner as process 200 shown in Figure 2, in the process 400, the second product retentate stream 408b from the second stage membrane 406b is recycled and combined with the treated natural gas feed stream 405 before being supplied to the first stage membrane 406a.

[0050] Alternatively, as shown in Figure 5, a two-stage membrane and adsorption process 500 can be provided. The process 500 is the similar to that described in process 200 shown in Figure 2, and like numerals are used to denote like features incremented by 300, except rather than recycle the second product retentate stream 508b, the second product retentate stream 508b from is fed to a nitrogen adsorption unit 520 for further removal of nitrogen from the second product retentate stream 508b. The resulting adsorption product stream 524 from the nitrogen adsorption unit 520 can be combined with the first product retentate streams 508a from the first membrane stage 506a and exported to a natural gas pipeline 514. The second waste permeate stream 510b from the second membrane stage 506b is combined with the nitrogen adsorption waste stream 522 from the nitrogen adsorption unit 520. The combined waste streams are injected into a well 512, or otherwise disposed of.

[0051] Similarly to the two-stage process 200 of Figure 2, in both process 400 and 500, the first stage membrane 406a, 506a has a N2 / CH4 selectivity equal or higher than about 7 and a N2 permeance of equal to or higher than about 2500 GPU (Gas permeance unit). The second stage membrane unit 406b, 506b can have a N2 / CH4 selectivity equal or higher than about 10 and N2 permeance of about 1500 GPU.

[0052] In some examples, the process may further comprise a subsea compression unit as shown in the schematics of process 600 in Figure 6 and process 700 in Figure 7. The process 600 is identical to the process 100 shown in Figure 1 and the like features are shown in like reference numbers incremented by 500. The process 600 is provided with an additional subsea compression unit 630 arranged to compress the waste permeate stream 610 from the membrane separation unit 606 prior to injection of the waste permeate stream 610 into a well 612. The process 700 is identical to the process 200 shown in Figure 2 and the like features are shown in like reference numbers incremented by 500. The process 700 is provided with an additional subsea compression unit 730 arranged to compress the second waste permeate stream 710b from the second membrane stage 706b prior to injection of the waste permeate stream 710b into a well 712.

Claims

What is claimed is:

1. A process for the removal of nitrogen from natural gas, the process comprising:a) providing a feed stream comprising natural gas, wherein the natural gas comprises at least a gaseous mixture of methane and nitrogen;b) supplying the feed stream to a separator, wherein the separator comprises a membrane separator having nitrogen-methane selectivity and the membrane separator being configured to allow nitrogen to permeate through the membrane; andc) separating the components of the feed stream using the separator into a product retentate stream comprising methane, and a nitrogen waste permeate stream.

2. The process of claim 1, wherein the product retentate stream comprises at least about 96 mol% methane.

3. The process of claim 1 or 2, comprising maintaining a pressure of the product retentate stream at a pressure of the feed stream.

4. The process of claim 3, wherein the pressure of the feed stream and product retentate stream is a pressure required for exporting natural gas.

5. The process of any of claims 1 to 4, wherein the process comprises supplying the nitrogen waste permeate stream to a nitrogen adsorption unit and producing an adsorption product stream comprising methane, and an adsorption waste stream comprising nitrogen.

6. The process of claim 5, wherein the nitrogen adsorption unit comprises at least one of a pressure swing adsorption system, or a vacuum swing adsorption system.

7. The process of any one of claims 1 to 6, wherein the process comprises disposing of thewaste permeate stream.

8. The process of any one of claims 5 to 7, wherein the process comprises disposing of the waste adsorption stream.

9. The process of any one of claims 1 to 8, further comprising recycling the product retentate stream back to the separator.

10. The process of any one of claims 1 to 9, wherein the membrane has a nitrogen / methane selectivity of equal to or greater than about 10.

11. The process of any one of claims 1 to 10, wherein the separator comprises a multi-stage membrane process which includes a plurality of membrane stages arranged in series, such that a product retentate stream is produced from each membrane stage and a waste permeate stream from each membrane stage is fed to subsequent membrane stages until a final membrane stage, where a final waste permeate stream is disposed of.

12. The process of any one of claims 1 to 10, wherein the separator comprises a multi-stage membrane process having a first membrane stage with nitrogen-methane selectivity and a second membrane stage with nitrogen-methane selectivity,wherein the process comprises nitrogen from the feed stream permeating through the first membrane stage and producing a first product retentate stream and a first waste permeate stream; andsupplying the first waste permeate stream to the second membrane stage wherein the nitrogen from the first waste permeate stream permeate through the second membrane stage, producing a second product retentate stream and a second waste permeate stream.

13. The process of claim 11 or 12, further comprising recycling the product retentate stream, or the second product retentate stream to the first membrane stage.

14. The process of any of claims 11 to 13, further comprising supplying the second waste permeate stream, or a subsequent waste permeate stream to a nitrogen adsorption unit and producing a methane product stream, and an adsorption waste stream comprising nitrogen.

15. The process of any of claims 11 to 14, further comprising supplying the second product retentate stream, or subsequent product retentate stream to a nitrogen adsorption unit and producing a methane product stream, and an adsorption waste stream comprising nitrogen.

16. The process of any of claims 5 to 15, further comprising compressing the adsorption product stream produced from the nitrogen adsorption unit.

17. The process of claim 16, comprising combining the adsorption product stream produced from the nitrogen adsorption unit with the product retentate stream.

18. The process of any of claims 12 to 17, wherein the first membrane stage comprises a membrane with a nitrogen / methane selectivity of equal to or greater than about 7 and a nitrogen permeance of equal to or more than about 2500 GPU.

19. The process of any of claims 12 to 18, wherein the second membrane stage comprises a membrane with a nitrogen / methane selectivity of equal to or greater than about 10 and a nitrogen permeance of about 1500 GPU.

20. The process of any of claims 1 to 19, further comprising pre-treating the feed stream prior to supplying the feed stream to the separator, wherein pre-treating comprises at least one of: changing the temperature of the feed stream, changing the pressure of the feed stream, removing higher alkanes and other contaminants from the natural gas.

21. A system configured to perform the process according to any one of claims 1 to 20, the system comprising a separator, wherein the separator comprises a membrane separator having nitrogen-methane selectivity and the membrane separator is configured to allow nitrogen to permeate through the membrane.

22. A methane product stream produced according to the process of any of claims 1 to 20.Application No: GB2313501.5 Examiner: Mr Martin PriceClaims searched: 1-22Date of search: 11 October 2023Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance X 1-22 CN 113289462 A Univ South China - see e.g. claim 1 X 1-22 CN 113357840 A Univ Dalian - see e.g. claim 1 X 1-22 CN 113209839 A Univ Tianjin - see e.g. claim 1 v A 1-22 US 2017 / 0100696 Al Noda - see e.g. claim 1, figure 1 and Table 1 X 1-22 WO 2014 / 070789 Al Georgia Tech - see e.g. claim 1 v A 1-22 JP 2015091918 A JFE - see e.g. claim 1 X 1-22 US 6565626 Al Baker - see e.g. claim 1 X 1-22 US 2021 / 0162337 Al Terrien - see the abstract and figureCategories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of same category. before the filing date of this invention. & Member of the same patent family J7 Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:Search of GB. EP, WO &US patent documents classified in the following areas of the UKCX :Worldwide search of patent documents classified in the following areas of the IPC____________C10L_______________________________________________________The following online and other databases have been used in the preparation of this search reportWPI, EPODOCInternational Classification:Subclass Subgroup Valid From C10L 0003 / 10 01 / 01 / 2006 BOID 0053 / 22 01 / 01 / 2006 C07C 0007 / 144 01 / 01 / 2006

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