WO2025151947A1

WO2025151947A1 - Decomposing a feedstock using an oxidant buffer

Info

Publication number: WO2025151947A1
Application number: PCT/CA2025/050020
Authority: WO
Inventors: David Aaron Leboe; Timothy Scott Coleman; Dana Jennifer MRAZ
Original assignee: Ekona Power Inc
Current assignee: Ekona Power Inc
Priority date: 2024-01-15
Filing date: 2025-01-09
Publication date: 2025-07-24
Anticipated expiration: 2026-07-15

Abstract

A pre-heated feedstock is delivered to a reaction chamber, and an oxidant buffer is delivered to a combustion chamber. The combustion chamber is connected to the reaction chamber such that gases in the combustion chamber may flow into the reaction chamber. A fuel is delivered to the combustion chamber. The fuel is combusted to generate combustion products. The combustion products are used to force the oxidant buffer to flow into the reaction chamber and mix with the pre-heated feedstock. A first portion of the pre-heated feedstock combusts in response to coming into contact with the oxidant buffer and causes a second portion of the pre- heated feedstock to decompose.

Description

DECOMPOSING A FEEDSTOCK USING AN OXIDANT BUFFER

Field

[0001] The present disclosure relates to thermal pyrolysis and in particular to methods and systems for decomposing a feedstock using an oxidant buffer.

Background

[0002] Thermal pyrolysis is a method by which a feedstock gas, such as a hydrocarbon, is decomposed without oxygen into its constituent elements (in the case of a hydrocarbon, carbon and hydrogen). The decomposition is triggered by sufficiently raising the temperature of the feedstock gas to a point at which the chemical bonds of the elements of the feedstock gas break down.

[0003] Pyrolysis may be achieved by bringing the feedstock gas into thermal contact with a hot fluid. In one example, combustion product gases, formed as a result of combusting a combustible fuel, may be mixed with the feedstock gas. At high-enough temperatures, the mixing of the hot fluid with the feedstock gas, and the transfer of thermal energy from the hot fluid to the feedstock gas, is sufficient to cause the feedstock gas to break down and decompose.

[0004] According to one type of feedstock reactor, a combustor is fluidly connected, via one or more nozzles, to a reaction chamber in which the feedstock is to be decomposed. A combustible mixture is combusted in a combustion chamber of the combustor, and the resulting combustion products are expelled under high pressure through orifices in the nozzle(s) and into the reaction chamber, wherein the combustion products mix with the feedstock and cause decomposition of the feedstock.

[0005] However, in some cases the combustible mixture may undergo non-ideal combustion in which extremely high temperatures and pressures are achieved in the combustion chamber. Such non-ideal combustion may resemble an uncontrolled detonation rather than controlled deflagration of the fuel. Furthermore, excessive heating of the combustion chamber generally requires active cooling, reducing the net heat that is available for transfer to the feedstock in the reaction chamber. Still further, extreme temperatures and pressures in the combustor can lead to excessive wear on high-temperature components, such as the gas distribution nozzles, valves, and the walls of the combustion chamber. Summary

[0006] According to a first aspect of the disclosure, there is provided a method of decomposing a feedstock, comprising: delivering a pre-heated feedstock to a reaction chamber; delivering an oxidant buffer to a combustion chamber, wherein the combustion chamber is connected to the reaction chamber such that gases in the combustion chamber may flow into the reaction chamber; delivering a fuel to the combustion chamber; combusting the fuel to generate one or more combustion products; and using the one or more combustion products to force at least a portion of the oxidant buffer to flow into the reaction chamber and mix with the pre-heated feedstock, wherein a first portion of the pre-heated feedstock combusts in response to coming into contact with the at least a portion of the oxidant buffer and causes a second portion of the pre-heated feedstock to decompose.

[0007] After delivering the fuel to the combustion chamber, the oxidant buffer may be located between the fuel and an outlet of the combustion chamber.

[0008] Delivering the fuel to the combustion chamber may be performed after delivering the oxidant buffer to the combustion chamber.

[0009] Delivering the oxidant buffer and the fuel to the combustion chamber may comprise delivering a lean combustible gas mixture to the combustion chamber.

[0010] Delivering the fuel may comprise delivering a combustible gas mixture comprising the fuel in combination with further oxidant.

[0011] The further oxidant may be pure O2 or air.

[0012] Delivering the pre-heated feedstock may comprise: pre-heating the feedstock; and delivering the pre-heated feedstock to the reaction chamber.

[0013] The oxidant buffer may comprise pure O2.

[0014] The feedstock may comprise a hydrocarbon.

[0015] The fuel may have the same composition as the feedstock.

[0016] Delivering the oxidant buffer to the combustion chamber may comprise delivering the oxidant buffer at a temperature that is less than an auto-ignition temperature of the fuel fuel.

[0017] Delivering the oxidant buffer to the combustion chamber may comprise delivering the oxidant buffer at a temperature of no more than 675 K. [0018] According to a further aspect of the disclosure, there is provided a feedstock reactor comprising: a reaction chamber connected to a combustion chamber such that gases in the combustion chamber may flow into the reaction chamber; at least one compressor; an igniter; valving; and at least one controller comprising circuitry and programmed to operate the valving, the at least one compressor, and the igniter to: deliver pre-heated feedstock to the reaction chamber; deliver an oxidant buffer to the combustion chamber; deliver a fuel to the combustion chamber, wherein, after delivering the fuel to the combustion chamber, the oxidant buffer is located between the fuel and an outlet of the combustion chamber; and trigger the igniter to combust the fuel to generate one or more combustion products that force at least a portion of the oxidant buffer to flow into the reaction chamber and mix with the pre-heated feedstock, wherein a first portion of the pre-heated feedstock combusts in response to coming into contact with the at least a portion of the oxidant buffer and causes a second portion of the pre-heated feedstock to decompose.

[0019] The at least one controller may be further programmed to deliver the fuel to the combustion chamber after delivering the oxidant buffer to the combustion chamber.

[0020] The feedstock reactor may further comprise a heater for pre-heating the feedstock.

[0021] This summary does not necessarily describe the entire scope of all aspects. Other aspects, features and advantages will be apparent to those of ordinary skill in the art upon review of the following description of specific embodiments.

Drawings

[0022] Embodiments of the disclosure will now be described in detail in conjunction with the accompanying drawings of which:

[0023] FIG. 1A is a schematic diagram showing an oxidant buffer being loaded into a combustion chamber, according to an embodiment of the disclosure;

[0024] FIG. 1 B shows a fuel and an oxidant being loaded into the combustion chamber of FIG. 1 A, according to an embodiment of the disclosure;

[0025] FIG. 1C shows activation of an igniter to trigger ignition of the fuel, according to an embodiment of the disclosure;

[0026] FIG. 1 D shows combustion of the fuel and oxidant, and injection of the oxidant buffer into the reaction chamber, according to an embodiment of the disclosure; [0027] FIG. 1 E shows pyrolysis of a feedstock in the reaction chamber, according to an embodiment of the disclosure; and

[0028] FIG. 2 is a flow diagram of a method of decomposing a feedstock using an oxidant buffer, according to an embodiment of the disclosure.

Detailed Description

[0029] The present disclosure seeks to provide a novel methods and systems for decomposing a feedstock using an oxidant buffer. While various embodiments of the disclosure are described below, the disclosure is not limited to these embodiments, and variations of these embodiments may well fall within the scope of the disclosure which is to be limited only by the appended claims.

[0030] Generally, embodiments of the disclosure relate to methods and systems for performing pyrolysis of a feedstock gas, such as natural gas or a hydrocarbon gas, such as methane. Such methods of pyrolysis, as well as example feedstock gas reactors that may be used for such pyrolysis, are described in further detail in PCT Publication No. WO 2020/118417, herein incorporated by reference in its entirety.

[0031] In order to remedy some of the drawbacks noted above in connection with non-ideal combustion of the fuel, fuel energy can be converted into heat in situ (in other words, in the reaction chamber itself) rather than ex situ (i.e., rather than in the combustion chamber). However, such an approach would, on its own, eliminate the need for combustors, and, without high-pressure combustion, mixing of the hot combustion products with the feedstock would be reduced.

[0032] Therefore, according to embodiments of the disclosure, a hybrid method is described wherein one or more external combustors are used to propel the injection of O2 into the reaction chamber, thereby using the mixing nozzles to evenly distribute the O2 throughout the pre-heated feedstock.

[0033] In particular, according to embodiments of the disclosure, there is described a method of decomposing a feedstock in which: a pre-heated feedstock is delivered to a reaction chamber; an oxidant buffer is delivered to a combustion chamber connected to the reaction chamber such that gases in the combustion chamber may flow into the reaction chamber via an outlet of the combustion chamber; a fuel is delivered to the combustion chamber; the fuel is combusted to generate one or more combustion products; and the one or more combustion products are used to force at least a portion of the oxidant buffer to flow into the reaction chamber via the outlet and mix with the pre-heated feedstock. Upon coming into contact with the oxidant buffer, a first portion of the pre-heated feedstock combusts and causes a second (unreacted) portion of preheated feedstock to decompose by pyrolysis.

[0034] Turning now to FIGS. 1A-1 E, there is shown a simplified schematic diagram of various stages of decomposing a feedstock using an oxygen buffer, according to an embodiment of the disclosure. As shown in FIGS. 1A-1 E, a combustion chamber 10 is connected to a reaction chamber 11 via a nozzle 18. Combustion chamber 10 includes an igniter 19, a fuel valve 13, and an oxidant valve 14.

[0035] In FIG. 1A, a pure oxygen (O2) buffer 12 is loaded into combustion chamber 10 via oxidant valve 14. Oxygen buffer 12 may be cold (e.g., at a temperature below 675 K (below the auto-ignition temperature of the fuel), or at a temperature of about 300 K) to provide cooling to mixing nozzle 18 when injected through mixing nozzle 18, as described in further detail below. At the same time, a pre-heated feedstock 16 is loaded into reaction chamber 11 . The feedstock is pre-heated to at least its auto-ignition temperature (e.g., at least 500 °C in the case of the feedstock being combusted in the presence of oxygen at 5 bars). The feedstock may be preheated using a heater (not shown) such as a thermal energy recovery unit (e.g., a heat exchanger), or a gas or electric-fuelled heater. The pressures within combustion chamber 10 and reaction chamber 11 are about equal such that little or no leakage occurs between the two chambers during loading of combustion chamber 10 with fuel and oxidant (as described below in connection with FIG. 1 B), and loading of reaction chamber 11 with feedstock 16. For example, feedstock 16 may be loaded into reaction chamber 11 substantially at the same time as combustion chamber 10 is loaded with the fuel and oxidant. Residual combustion products 15 from the previous reaction cycle are moved to the bottom of combustion chamber 10 (i.e., adjacent nozzle 18) by the injection of oxygen buffer 12 into combustion chamber 10.

[0036] In FIG. 1 B, a fuel and an oxidant (e.g., pure oxygen or air) are loaded into combustion chamber 10 via respective valves 13 and 14, forming a combustible gas mixture 17 within combustion chamber 10. As a result, oxygen buffer 12 is positioned between combustible gas mixture 17 and nozzle 18.

[0037] In FIG. 1C, igniter 19 is activated and causes combustion of combustible gas mixture 17, triggering the generation of hot combustion products 20. [0038] In FIG. 1 D, hot combustion products 20 expand and cause injection of oxygen buffer 12 into reaction chamber 11 , via apertures in nozzle 18. According to some embodiments, the apertures may be differently-oriented to improve mixing. Oxygen buffer 12 mixes with preheated feedstock 16, triggering auto-ignition of some of the pre-heated feedstock 16. This results in the energy of combustion being transferred to unreacted pre-heated feedstock 16. Energy may also be transferred to unreacted pre-heated feedstock 16 via dynamic fluid mixing and compression of unreacted pre-heated feedstock 16 as a result of the pressure increasing within reaction chamber 11 in response to the combustion of some of the pre-heated feedstock 16. Past a certain point, the increase in the temperature of the unreacted feedstock 16 is sufficient to drive decomposition or pyrolysis of the unreacted feedstock 16 (FIG. 1 E). In the case of methane, for example, the decomposition takes the following form:

CH4 + energy — > C + 2H2

The pyrolysis reaction generates reaction products 21 that are extracted from reaction chamber 11 via an outlet 22. A portion of reaction products 21 may be recycled back to reaction chamber 11 for future reaction cycles (not shown). The reaction products may comprise one or more of hydrogen, nitrogen, and carbon. The unwanted products may comprise primarily carbon dioxide and water. The recycled gas mixture may comprise primarily unreacted natural gas, hydrogen, nitrogen, and carbon monoxide.

[0039] Turning to FIG. 2, there is shown a flow diagram of a method 200 of decomposing a feedstock using an oxidant buffer, according to an embodiment of the disclosure.

[0040] At block 201 , a feedstock, such as a hydrocarbon, is pre-heated.

[0041] At block 202, the reaction chamber of the feedstock reactor is loaded with the pre-heated feedstock.

[0042] At block 203, the combustion chamber of the feedstock reactor is loaded with the oxidant buffer. The oxidant buffer may comprise cold or hot O2 (provided that the temperature of the buffer is below the auto-ignition temperature of the fuel).

[0043] At block 204, a combustible gas mixture (i.e., a fuel, such as a hydrocarbon, and an oxidant, such as O2) is loaded into the combustion chamber. According to some embodiments, the fuel may have the same composition as the feedstock, and for example may comprise recycled, unreacted feedstock from a previous reaction cycle. [0044] At block 205, the combustor is fired by triggering combustion of the combustible gas mixture. The hot combustion products that are generated expand and force the oxidant buffer through the mixing nozzle, wherein the oxidant buffer is jetted and dispersed into the reaction chamber. Upon coming into contact with the oxidant buffer, some of the pre-heated feedstock auto-ignites and combusts.

[0045] At block 206, unreacted pre-heated feedstock is decomposed by pyrolysis in an endothermic reaction which is driven by the heat of combustion.

[0046] A block 207, one or more reaction products produced by the decomposition of the feedstock are extracted from the reaction chamber. The process may then be repeated.

[0047] While FIGS. 1A-1 E illustrate a method in which a combustible gas mixture (fuel and an oxidant, such as O2 or air) is delivered to the combustion chamber after the oxidant buffer has already been delivered to the combustion chamber, this is not the only one way of loading the combustion chamber prior to ignition. According to other embodiments, fuel may be delivered to the combustion chamber on its own (i.e., in the absence of any other oxidant), and combustion of the fuel may be achieved based on the fact that some of the fuel will mix with the oxidant buffer and therefore result in a combustible gas mixture. In such a case, the local “leanness” of the mixture (i.e., the fuel equivalence ratio) must be sufficient to allow the mixture to be ignitable, and the oxidant buffer should mix sufficiently with the fuel in the region of ignition. According to some embodiments, the fuel and the oxidant buffer may be delivered to the combustion chamber in a pre-mixed, lean state. In this case, sufficient fuel should be delivered to the combustion chamber to, again, ensure that the mixture is ignitable.

[0048] Advantageously, by employing an oxidant buffer as described herein, the combustor may require less active cooling, preserving the longevity of high-temperature components of the reactor. Furthermore, a cold oxidant buffer may provide cooling to the mixing nozzle. Heat is generated in situ inside the refractory- lined reaction chamber, reducing the amount of reaction heat that may otherwise be lost in the case of combustion products, used to transfer heat to the feedstock, being generated outside the reaction chamber (i.e., in the combustion chamber). Furthermore, by operating the reactor on a cyclic basis, the cyclical nature of the combustion may preserve the reactor’s mixing and anti-fouling benefits.

[0049] Operation of the reactor’s valves may be controlled by a suitable controller (such as a microprocessor) comprising circuitry. The controller, or some other controller, may control the loading of the combustion and reaction chambers by controlling compressors or similar devices. Loading of the gases may be controlled by changing gas delivery pressure, gas temperature, and/or valve timing. The controller can control each of these via intermediate control elements (regulators, heaters, compressors, etc.) as well as via mechanically-designed pressure drops (orifices, etc.). The parameters may also be set manually.

[0050] The word “a” or “an” when used in conjunction with the term “comprising” or “including” in the claims and/or the specification may mean “one”, but it is also consistent with the meaning of “one or more”, “at least one”, and “one or more than one” unless the content clearly dictates otherwise. Similarly, the word “another” may mean at least a second or more unless the content clearly dictates otherwise.

[0051] The terms “coupled”, “coupling” or “connected” as used herein can have several different meanings depending on the context in which these terms are used. For example, as used herein, the terms coupled, coupling, or connected can indicate that two elements or devices are directly connected to one another or connected to one another through one or more intermediate elements or devices via a mechanical element depending on the particular context. The term “and/or” herein when used in association with a list of items means any one or more of the items comprising that list.

[0052] As used herein, a reference to “about” or “approximately” a number or to being “substantially” equal to a number means being within +/- 10% of that number.

[0053] Use of language such as “at least one of X, Y, and Z,” “at least one of X, Y, or Z,” “at least one or more of X, Y, and Z,” “at least one or more of X, Y, and/or Z,” or “at least one of X, Y, and/or Z,” is intended to be inclusive of both a single item (e.g., just X, or just Y, or just Z) and multiple items (e.g., {X and Y}, {X and Z}, {Y and Z}, or {X, Y, and Z}). The phrase “at least one of’ and similar phrases are not intended to convey a requirement that each possible item must be present, although each possible item may be present.

[0054] While the disclosure has been described in connection with specific embodiments, it is to be understood that the disclosure is not limited to these embodiments, and that alterations, modifications, and variations of these embodiments may be carried out by the skilled person without departing from the scope of the disclosure.

[0055] It is furthermore contemplated that any part of any aspect or embodiment discussed in this specification can be implemented or combined with any part of any other aspect or embodiment discussed in this specification.

Claims

1 . A method of decomposing a feedstock, comprising: delivering a pre-heated feedstock to a reaction chamber; delivering an oxidant buffer to a combustion chamber, wherein the combustion chamber is connected to the reaction chamber such that gases in the combustion chamber may flow into the reaction chamber; delivering a fuel to the combustion chamber; combusting the fuel to generate one or more combustion products; and using the one or more combustion products to force at least a portion of the oxidant buffer to flow into the reaction chamber and mix with the pre-heated feedstock, wherein a first portion of the pre-heated feedstock combusts in response to coming into contact with the at least a portion of the oxidant buffer and causes a second portion of the preheated feedstock to decompose.

2. The method of claim 1 , wherein, after delivering the fuel to the combustion chamber, the oxidant buffer is located between the fuel and an outlet of the combustion chamber.

3. The method of claim 1 or 2, wherein delivering the fuel to the combustion chamber is performed after delivering the oxidant buffer to the combustion chamber.

4. The method of claim 1 or 2, wherein delivering the oxidant buffer and the fuel to the combustion chamber comprises delivering a lean combustible gas mixture to the combustion chamber.

5. The method of any one of claims 1-3, wherein delivering the fuel comprises delivering a combustible gas mixture comprising the fuel in combination with further oxidant.

6. The method of claim 5, wherein the further oxidant is pure O2.

7. The method of claim 5, wherein the further oxidant is air.

8. The method of any one of claims 1-7, wherein delivering the pre-heated feedstock comprises: pre-heating the feedstock; and delivering the pre-heated feedstock to the reaction chamber.

9. The method of any one of claims 1-8, wherein the oxidant buffer comprises pure O2.

10. The method of any one of claims 1-9, wherein the feedstock comprises a hydrocarbon.

11. The method of any one of claims 1-10, wherein the fuel has the same composition as the feedstock.

12. The method of any one of claims 1-11 , wherein delivering the oxidant buffer to the combustion chamber comprises delivering the oxidant buffer at a temperature that is less than an auto-ignition temperature of the fuel.

13. The method of any one of claims 1-12, wherein delivering the oxidant buffer to the combustion chamber comprises delivering the oxidant buffer at a temperature of no more than 675 K.

14. A feedstock reactor comprising: a reaction chamber connected to a combustion chamber such that gases in the combustion chamber may flow into the reaction chamber; at least one compressor; an igniter; valving; and at least one controller comprising circuitry and programmed to operate the valving, the at least one compressor, and the igniter to: deliver pre-heated feedstock to the reaction chamber; deliver an oxidant buffer to the combustion chamber; deliver a fuel to the combustion chamber, wherein, after delivering the fuel to the combustion chamber, the oxidant buffer is located between the fuel and an outlet of the combustion chamber; and trigger the igniter to combust the fuel to generate one or more combustion products that force at least a portion of the oxidant buffer to flow into the reaction chamber and mix with the pre-heated feedstock, wherein a first portion of the preheated feedstock combusts in response to coming into contact with the at least a portion of the oxidant buffer and causes a second portion of the pre-heated feedstock to decompose.

15. The feedstock reactor of claim 14, wherein the at least one controller is further programmed to deliver the fuel to the combustion chamber after delivering the oxidant buffer to the combustion chamber.

16. The feedstock reactor of claim 14 or 15, further comprising a heater for pre-heating the feedstock.