CARBON-FREE DIHYDROGEN PRODUCTION AND DELIVERY UNIT; METHOD FOR OPERATING SAID UNIT

Abstract

A dihydrogen production and delivery unit for a dihydrogen consumer, may include at least one gaseous hydrocarbon supply device, at least one microwave plasma plasmalysis reactor configured to generate, at a pressure equal to atmospheric pressure +/15%, plasmalysis of the gaseous hydrocarbon supplied by the supply device and which produces, by carbon-free production, at least dihydrogen and solid carbon, the production and delivery unit comprising at least one storage device for the produced dihydrogen and at least one device for delivering to the consumer the dihydrogen stored in the storage device.

Claims

1. A dihydrogen production and delivery unit configured for a dihydrogen consumer, the unit comprising: a gaseous hydrocarbon supply device; a microwave plasma plasmalysis reactor configured to generate, at a pressure equal to atmospheric pressure +/15%, plasmalysis of the gaseous hydrocarbon supplied by the supply device, the microwave plasma plasmalysis reactor producing at least H.sub.2 and comprising a resonant microwave radiation cavity configured to hold a plasma; a storage device suitable for the H.sub.2produced; and a delivery device configured for delivering to the consumer H.sub.2 stored in the storage device.

2. The production and delivery unit of claim 1, wherein the gaseous hydrocarbon is methane and/or natural gas.

3. The production and delivery unit of claim 1, wherein the gaseous hydrocarbon supply device is a gaseous hydrocarbon transmission network and/or at least one storage tank constituting the production and delivery unit.

4. The production and delivery unit of claim 1, wherein the microwave plasma plasmalysis reactor comprises a microwave radiation generator, a transmission guide configured to guide microwave radiation from the microwave radiation generator to the microwave radiation cavity of the microwave plasma plasmalysis reactor, and a microwave radiation isolator configured to prevent the microwave radiation not absorbed by the plasma from returning to the microwave radiation generator.

5. The production and delivery unit of claim 1, wherein the microwave plasma plasmalysis reactor comprises a plasma ignition device comprising a retractable metal tip that is configured to be inserted into or retracted in the microwave radiation cavity using an actuator.

6. The production and delivery unit of claim 1, wherein the microwave plasma plasmalysis reactor comprises a gas injection device comprising a nozzle configured to generate a gas flow of gaseous hydrocarbon from the supply system and is arranged in the microwave radiation cavity so as to form a vortex from the flow of gaseous hydrocarbon in the microwave radiation cavity.

7. The production and delivery unit of claim 1, wherein the microwave plasma plasmalysis reactor comprises a nozzle tube configured to contain the plasma and ensure a gradual lowering of temperature of products from plasmalysis at an outlet of the microwave radiation cavity.

8. The production and delivery unit of claim 7, wherein the microwave plasma plasmalysis reactor comprises a pipe arranged around the nozzle tube such that at least a portion of the pipe defines a chamber suitable for thermally isolating the plasma.

9. The production and delivery unit of claim 8, wherein at least a other portion of the pipe further defines a chamber for cooling the H.sub.2 and solid carbon produced by plasmalysis.

10. The production and delivery unit of claim 1, further comprising: a separation and filtration device so as to purify the H.sub.2 produced by plasmalysis.

11. The production and delivery unit of claim 1, further comprising: an electricity generator configured for generating electricity from the H.sub.2 produced by the production and delivery unit and a battery configured for storing electricity produced by the electricity generator and configured for supplying the production and delivery unit with electricity.

12. The production and delivery unit of claim 1, further comprising: a recovery device configured for recovering solid carbon generated by the plasmalysis.

13. A dihydrogen delivery system, comprising: the production and delivery unit of claim 1; and a dihydrogen consumer, wherein the delivery device is configured to supply a tank of the consumer.

14. A method for operating the dihydrogen production and delivery unit of claim 4, the method comprising: delivering, with the microwave radiation, microwave radiation at a power in a range of from 1 to 100 kW and a frequency in a range of from 850 MHz to 6 GHz.

15. The method of claim 14, wherein the gaseous hydrocarbon is previously mixed with an auxiliary gas comprising H.sub.2, N.sub.2, and/or Ar, before the gaseous hydrocarbon is injected into the microwave radiation cavity, which is a resonant cavity.

16. The production and delivery unit of claim 1, wherein the gaseous hydrocarbon comprises methane.

17. The production and delivery unit of claim 1, wherein the gaseous hydrocarbon comprises natural gas.

Description

[0052] Other features and advantages of the invention will appear both from the description which follows and from several exemplary embodiments, which are given for illustrative purposes and without limitation with reference to the appended schematic drawings, in which:

[0053] FIG. 1 schematically shows a unit for the production and delivery of dihydrogen in a carbon-free manner using a plasma generated by microwave radiation according to the invention.

[0054] FIG. 2 schematically shows a microwave radiation cavity of the production and delivery unit of FIG. 1, viewed in a plane perpendicular to the longitudinal axis of the plasma.

[0055] FIG. 3 is a detail view of the microwave radiation cavity of FIG. 2 with a nozzle tube and a pipe of the production and delivery unit of FIG. 1, viewed in a plane comprising the longitudinal axis of the plasma.

[0056] FIG. 4 is a schematic view illustrating dimensions of the resonant microwave radiation cavity of the plasmalysis reactor.

[0057] It should first of all be noted that while the figures set out the invention in detail for its implementation, they may of course be used to better define the invention where appropriate. It should also be noted that, in all of the figures, similar elements and/or elements fulfilling the same function are indicated by the same numbering.

[0058] FIG. 1 illustrates a unit 100 for the production and delivery of dihydrogen, in particular in a carbon-free manner, for a dihydrogen consumer 51, comprising at least one gaseous hydrocarbon supply device 1, at least one microwave plasma plasmalysis reactor 5 which is configured to generate plasmalysis of the gaseous hydrocarbon supplied by the supply device 1 and which produces at least dihydrogen, the production and delivery unit 100 comprising at least one storage device 33 for the produced dihydrogen and at least one device 35 for delivering to the consumer 51 the dihydrogen stored in the storage device 33.

[0059] Plasmalysis is a method that makes it possible to decompose the gaseous hydrocarbon into solid carbon C.sub.(s) and dihydrogen gas H2.sub.(g) by virtue of a plasma generated by microwave radiation. The gaseous hydrocarbon may be methane CH.sub.4, propane C.sub.3H.sub.8, butane C.sub.4H.sub.10 and its isomers, and/or natural gas or biomethane. Natural gas may predominantly comprise methane CH.sub.4 and, to a lesser extent, propane C.sub.3H.sub.8, and/or butane C.sub.4H.sub.10 and its isomers. When the gaseous hydrocarbon is methane, the plasmalysis reaction is written as:

[00001]$\begin{array}{cc}C{H}_4\stackrel{Plasma}{.fwdarw.}2H_{2\left(g\right)}+C_{\left(s\right)}& \left[\mathrm{Math}\right]\end{array}$

[0060] Therefore, it can be seen that the plasmalysis method allows dihydrogen to be generated in a completely carbon-free process, that is without the emission of carbon dioxide.

[0061] In other words, gaseous dihydrogen and solid carbon are products of the plasmalysis.

[0062] The gaseous hydrocarbon required for the plasmalysis reaction that takes place in the plasmalysis reactor 5 is supplied by the supply device 1. The supply device 1 comprises at least one storage tank 2 which may be refilled, for example, by tanker trucks and/or be replaced when it is empty.

[0063] In one embodiment not shown, the gaseous hydrocarbon supply device is a hydrocarbon gas distribution network. The distribution network allows the gaseous hydrocarbon to be transported from the gas terminals. The distribution network is thus, for example, a gas distribution network for industrial or household use.

[0064] With reference to FIGS. 1 to 4, the plasmalysis reactor 5 comprises at least one microwave radiation cavity 13 formed in a metal block 12. The gaseous hydrocarbon from the supply device 1 is injected into the microwave radiation cavity 13, and the microwave radiation is also guided into the microwave radiation cavity 13. The microwave radiation cavity 13 is configured to at least partially hold the plasma 16. Thus, the resonant microwave radiation cavity 13 allows very effective coupling of the microwave radiation with the plasma 16.

[0065] As illustrated in FIGS. 3 and 4, the microwave radiation cavity 13 is coupled to a waveguide specific to the frequencies between 850 MHz and 6 GHz, preferentially equal to 896 MHz, 915 MHz, 922 MHz, 2.45 GHz or 5.8 GHz. It is resonant, that is to say that 100% of the microwave radiation is reflected across the microwave radiation cavity 13 by at least one wall of the block 12 that defines the microwave radiation cavity 13 when there is no plasma 16 present in the microwave radiation cavity 13.

[0066] As shown in FIG. 4, the dimensions of an active discharge zone 54 of the resonant microwave radiation cavity 13 are defined by the frequency used. The active discharge zone 54 is the zone where the plasma 16 forms. The width 55 of the resonant microwave radiation cavity 13 is defined by the frequency used and by the type of waveguide, the height 56 of the resonant microwave radiation cavity 13 is equal to half the width 55 of this resonant microwave radiation cavity 13 and the width 57 of the active discharge zone 54 is less than or equal to the height 56 of the resonant microwave radiation cavity 13. Because of the geometry of the resonant microwave cavity, the microwaves concentrate close to center of the cavity to form an electromagnetic field distribution with a power density high enough to ionize the gaseous hydrocarbon flow. The active discharge zone 54, also called the plasma zone for the plasma 16, is the zone where the interaction between the electromagnetic field and the ionized gaseous hydrocarbon flow is optimal. The plasma is ignited by inserting the ignition device 15 into the center of the active discharge zone 54.

[0067] The injection of the gaseous hydrocarbon into the microwave radiation cavity 13 is carried out by an injection device 3 of the plasmalysis reactor 5. More specifically, as illustrated in FIG. 2, the injection device 3 comprises at least one nozzle 43two nozzles 43 in this instancecoupled to at least one inlet 4 of the microwave radiation cavity 13. The nozzle 43 allows a gaseous hydrocarbon flow from the supply device 1 to be created.

[0068] The inlet 4 is arranged tangentially to a direction of elongation of the plasma 16. The inlet 4 is also arranged tangentially to a wall that defines the microwave radiation cavity 13. This configuration then allows a vortex of the gaseous hydrocarbon flow 14 to be created in the microwave radiation cavity 13 as illustrated in FIG. 2 and FIG. 3. The vortex helps to stabilize the plasma 16.

[0069] A portion of the gaseous hydrocarbon flow 14 in the vortex that is coupled with the microwave radiation contributes to producing the plasma 16. This portion of the gaseous hydrocarbon flow 14 in the vortex producing the plasma will also undergo plasmalysis. It is understood in this context that the gas used to form the plasma and the gas that undergoes plasmalysis are the same. In other words, a single gas from a single source makes it possible to produce the plasma and produce dihydrogen and solid carbon. Stated otherwise, the gaseous hydrocarbon serves both as a plasmagene gas and as a plasmalysis reactant.

[0070] With reference to FIG. 1, the plasmalysis reactor 5 comprises a microwave radiation generator 7 which allows a plasma to be created in the microwave radiation cavity 13. The microwave radiation generator 7 may be a magnetron microwave radiation generator or a semiconductor microwave generator, which is also called a solid-state microwave generator.

[0071] In one embodiment not shown, the microwave radiation generator 7 is cooled by a water and/or air cooling device. This allows the microwave radiation generator 7 to be kept at an optimum operating temperature.

[0072] The microwave radiation generator 7 is configured to generate microwave radiation at a power of between 1 kW and 100 kW and a frequency of between 850 MHz and 6 GHz, preferentially equal to 896 MHz, 915 MHz, 922 MHz, 2.45 GHz or 5.8 GHz.

[0073] As shown in FIG. 1, the microwave radiation is directed toward the microwave radiation cavity 13 by a transmission guide 11 that is coupled to the microwave radiation generator 7. The transmission guide 11 is a rectangular or cylindrical waveguide or a coaxial cable.

[0074] A microwave radiation isolator 9 is arranged between the microwave radiation generator 7 and the transmission guide 11, that is at the coupling between the microwave generator 7 and the transmission guide 11. The isolator 9 prevents microwave radiation not absorbed by the plasma 16 from returning to the microwave radiation generator 7 via reflection in the transmission guide 11.

[0075] With reference to FIGS. 1, 3 and 4, the plasmalysis reactor 5 comprises a device 15 for igniting the plasma 16. The ignition device 15 is an electromechanical mechanism including a metal tip 45 and an actuator 47 which moves the metal tip 45 between a position outside the microwave radiation cavity and a position inside the microwave radiation cavity. The metal tip 45 is therefore retractable.

[0076] Thus, to ignite the plasma, the microwave radiation generated by the microwave radiation generator 7 is transmitted to the microwave radiation cavity 13 into which the gaseous hydrocarbon is injected tangentially to the walls of the microwave radiation cavity 13 to form a vortex from the gaseous hydrocarbon flow. As soon as the required microwave radiation power is reached, the plasma is ignited by the ignition device 15, the metal tip 45 of which remains in the active discharge zone of the microwave radiation cavity 13 for less than a second. The gaseous hydrocarbon flow 14, which is itself used to produce the plasma 16, thus undergoes the plasmalysis reaction. After the plasma ignition phase, the plasma is maintained and stabilized by the microwave flux and the gaseous hydrocarbon flow in the vortex.

[0077] The pressure in the microwave radiation cavity 13 is greater than or equal to atmospheric pressure. More generally, the pressure within at least part of the production and delivery unit 100 is greater than or equal to atmospheric pressure.

[0078] With reference to FIG. 1 and FIG. 3, an outlet 6 of the microwave radiation cavity 13 is extended by a nozzle tube 17 composed at least partly of ceramic and/or metal. The nozzle tube 17 is used to contain the plasma. The nozzle tube 17 is also used to ensure that the plasmalysis reaction continues by protecting the reaction products, in particular the plasmalysis products, from rapid cooling at the outlet 6 of microwave radiation cavity 13. In other words, the nozzle tube 17 therefore allows the temperature of the reaction products, in particular the plasmalysis products, to reduce gradually at the outlet 6 of the microwave radiation cavity 13.

[0079] The plasma 16, once created, extends both inside the microwave radiation cavity 13 and into the nozzle tube 17 along a longitudinal axis L. Thus, the nozzle tube extends from the outlet 6 of the microwave radiation cavity 13 in a direction away from the microwave radiation cavity along the longitudinal axis L.

[0080] With reference to FIG. 1, the plasmalysis reactor 5 comprises a pipe 18 which extends from the vicinity of the outlet 6 of the microwave radiation cavity 13 in a direction opposite the microwave radiation cavity 13 along the longitudinal axis L. The dimension of the pipe 18 measured along the longitudinal axis L is greater than the dimension of the nozzle tube 17 measured along the longitudinal axis L. The pipe completely surrounds the nozzle tube 17.

[0081] A first portion 19 of the pipe 18 takes the shape of a cylinder that is concentric relative to the nozzle tube 17. Thus, a chamber for thermally isolating the plasma 16 is defined between an outer face of the nozzle tube 17 and an inner face of the first portion 19 of the pipe 18. The chamber 20 allows the plasma 16 to be thermally isolated in order to reduce, or even eliminate, temperature inhomogeneities within the plasma 16, in particular on its periphery.

[0082] The pipe 18 comprises a second portion 21 which extends the first portion 19 of the pipe along an axis parallel to the longitudinal axis L of the plasma 16. The second portion 21 of the pipe 18 defines a cooling chamber 22. Thus, the cooling chamber allows the reaction products to be cooled. Solidification of the carbon is thus improved thereby. The reaction products group together methane that did not decompose during the plasmalysis and the plasmalysis products, that is dihydrogen gas and solid carbon.

[0083] In the embodiment of the invention in FIG. 1, the second portion 21 of the pipe 18 includes, on its inner face, a plurality of fins 23 which extend radially from the inner face of the second portion 21 of the pipe 18 in the direction of the nozzle tube 17 and are thermally coupled to the inner face of the second portion of the pipe 18. Thus, heat exchanges with the reaction products that come into contact with the fins 23 are improved, facilitating solidification of the carbon produced by plasmalysis.

[0084] A fluid circulation device 24 is arranged against an outer wall of the second portion 21 of the pipe 18 so as to at least partly cool the second portion 21 of the pipe 18. Thus, the cooling of the reaction products in the cooling chamber 22 is ensured through convective and conductive exchange with at least part of the inner face of the second portion 21 of the pipe 18 which is cooled by the fluid circulation device 27. The separation of the dihydrogen from the other reaction products is improved by this cooling. When the pipe 18 further comprises the fins 23 which are then themselves also cooled by thermal conduction, the separation is even more efficient. This is very useful in particular when the flow of reaction products flows to a separation and filtering device 25, 29 with which the production and delivery unit 100 is equipped.

[0085] The separation and filtration device 25, 29 with which the production and delivery unit 100 is equipped comprises a vortex separator element 25. The separator element 25 is configured to suck in the flow of cooled reaction products from the cooling chamber 22. The cooled solid carbon is deposited either on a bottom of the separator element 25 or on an inner surface of a wall of the separator element 25.

[0086] Other solid particles are present in the flow of cooled reaction products and also are deposited at the same locations as the solid carbon.

[0087] The solid carbon thus recovered is stored in a recovery device 41 and may be taken care of by the same vehicle that changes or refills the storage tanks 2. The solid carbon may then be recycled for various industrial uses.

[0088] Next, the flow of reaction products free of solid particles is filtered by a filtration system 29 of the separation and filtration device 25, 29. The dihydrogen obtained after filtration then has a level of purity that allows it to be used either in a fuel cell or in an internal combustion engine. The other reaction products after filtration may be recycled by reinjecting them back into the microwave radiation cavity 13 via a return pipe 30.

[0089] The production and delivery unit 100 comprises a compression device 31 for transferring the purified dihydrogen to a storage device 33 such as a tank or a cylinder. The dihydrogen is then stored at a pressure of up to about 900 bars. Thus, it is possible to meet the consumer's demand for dihydrogen under all circumstances.

[0090] The delivery system 35 makes it possible to fill the dihydrogen tanks of at least one consumer 51, such as land transport means, in particular cars and/or trucks, sea transport means, such as a ship, or air transport means, such as an airplane. The delivery system 35 draws the dihydrogen from the storage device 33.

[0091] The production and delivery unit 100 further comprises an electricity generator 37 for generating electricity from the dihydrogen produced and a battery 39 for storing the electricity produced by the electricity generator 37.

[0092] The battery 39 thus allows the production and delivery unit 100 be supplied with electricity even if the electrical network is absent or unavailable. In this context, it is understood that the production and delivery unit as illustrated in FIG. 1 may be autonomous.

[0093] Of course, the invention is not limited to the examples that have just been described, and numerous modifications can be made to these examples without departing from the scope of the invention.

[0094] The invention as has just been described clearly achieves the aim that it set for itself, and makes it possible to provide a unit for the production and delivery of dihydrogen in a carbon-free manner that is, in particular, straightforward to implement, economically viable, does not emit greenhouse gases and is even autonomous if required by environmental constraints.