Patent Application
20250042731
The present invention relates to the field of producing dihydrogen (H2) by pyrolysis of a pure gas or a gaseous mixture.
Dihydrogen, or more commonly called hydrogen molecule or simply hydrogen consists of two hydrogen atoms.
Hydrogen is commonly used in the industry for manufacturing chemical fertilizers or in the oil industry, but also as energy. The fight against global warming and using carbon-free energy has strengthened research and development on using hydrogen as energy, in particular for motorisation of heavy vehicles (lorries, buses, trains, aeroplanes, etc.). Thus, it is estimated that global hydrogen needs, all sectors combined, will go from 71 million tonnes in 2019 to almost 137 million tonnes by 2040, and to 519 million tonnes in 2070, with a use mainly in transport and aviation (more than 50%), in the industry (around 15%) and electricity production (around 15%).
To meet this demand, it is therefore essential to increase global hydrogen production capacities. Currently, 45 million tonnes of hydrogen are produced a year, mainly from fossil raw materials such as oil, coal or gas, by gasifying coal or steam reforming of natural gas. These two methods emit a great quantity of polluting or greenhouse gases such as CO or CO2.
It is also possible to produce hydrogen by water electrolysis, but this assumes water is consumed, which is not always possible. Biological methods for producing hydrogen are also undergoing development, they have even lower yields and also produce CO2.
Another method known as “Kvaerner Carbon Black & Hydrogen” makes it possible to produce hydrogen and carbon from hydrocarbons by high-temperature thermal cracking. The quantity of heat necessary to produce thermal cracking is provided by a recycled hydrogen-based plasma burner coming from said method which cuts off the quantity of hydrogen obtained and makes a method which consumes a lot of energy with a hydrogen yield which is ineffective.
Furthermore, hydrogen is often produced in large units requiring its transport from said units to the final location of use over sometimes long distances, also increasing the environment cost of producing hydrogen.
Thus, it is necessary to develop more effective, less polluting and less energy-consuming methods, local dihydrogen production units should also be proposed, which are easy to implement and to size, according to the quantity of dihydrogen to be produced.
The invention aims, in particular, to propose a machine for producing dihydrogen by pyrolysis of a gas, in particular, a hydrocarbon gas, which is easy to install locally, that can be sized according to the quantity of dihydrogen to be produced, the invention also proposes an integrated installation for producing dihydrogen, as well as a method for producing dihydrogen by pyrolysis of a gas, in particular of a hydrocarbon gas, said production being able to be done locally, being more effective, less energy-consuming and less polluting than current production methods.
To this end, a machine for producing dihydrogen by pyrolysis of a gas is provided, according to the invention, comprising:
The machine according to the invention is particularly suitable for treating a hydrocarbon gas, in which the solid particles recovered by the collecting means are mainly carbon and the gas leaving the treating device is mainly dihydrogen.
According to the particular features of the invention, which can be used individually or in combination:
The invention also relates to an integrated installation for producing dihydrogen by pyrolysis of a hydrocarbon gas, comprising:
Preferably, the integrated installation is sized according to the quantity of hydrogen to be produced. Thus, if needed, the reactor comprises a tube section array connected in pairs in series and extending parallel to one another and facing one another, each section, being shaped in a spiral with a diameter of between 25 and 250 mm, a deployed length of between 20 m and 150 m, a bending diameter of between 100 mm and 3000 mm. The respective dimensions of the tube sections, as well as the number of sections are suitable according to the quantity of hydrogen to be produced.
More preferably, the device for treating the integrated installation comprises at least one pressure swing adsorption device.
The invention also relates to a method for producing dihydrogen from hydrocarbon gas comprising the steps of:
Other features and advantages of the invention appear on reading the following description of a particular and non-limiting embodiment of the invention.
Reference is made to the accompanying drawings, among which:
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According to a preferable embodiment of the invention and in reference to
The tube 2 is, in this case, entirely made of electrically conductive material and is shaped in a spiral with a first end 2a forming an inlet for a gas G and an opposite second end 2b forming an outlet for the pyrolysed gas Gp.
A power supply circuit 3 is connected to the tube 2 in order to heat the tube by Joule heating to a temperature above a pyrolysis temperature of the gas circulating in the tube. It is reminded that the pyrolysis of the gas is a chemical breakdown of said gas under the effect of the temperature and in the total absence of oxygen. The power supply circuit 3 comprises, in this case, a current generator 3a. A person skilled in the art will know how to size the generator to obtain the electrical power necessary for the heating by Joule heating of the tube 2 for the pyrolysis of the gas to be treated. Generally, the tube is powered by a low-voltage, but high-intensity electrical current. The generator can deliver a direct or alternating current. The power supply circuit 3 can be connected to an electrical distribution network, to batteries or to an electricity generator (as examples, these can be solar panels, wind turbines or a powered generator). Naturally, there can be multiple power supply sources. According to a favoured embodiment of the invention, the current is at least partially generated by an engine or a gas turbine 3a. The electrical power necessary is calculated according to the temperature to be reached in the tube such that the gas G is pyrolysed. As an example, the adjustment of the temperature can be controlled by a thyristor, subject to the temperature of the gas Gp at the second end 2b of the tube 2 which makes it possible to control the voltage and/or the intensity of the current sent into the tube 2, the adjustment is done equally by wave train or by phase angle.
At the second end of the tube 2b, a member 4 for cooling and for separating the gas Gp leaving the tube 2 is connected, intended on the one hand, to cool the gas Gp and on the other hand, to separate the pyrolysed gas Gp and the solid particles present in said pyrolysed gas. The cooling and separating member 4, in this case, consists of at least one cyclone. A person skilled in the art will know how to size the number and the size of the cyclones, according to the volume of pyrolysed gas to be cooled and to be separated.
A collecting means 5 is associated with the separating member 4 to collect the solid particles S extracted from the pyrolysed gas Gp. The collecting means is of the tray or airtight conveyor type. If a person skilled in the art deems it necessary, they can add to the collecting means 5, complementary devices for separating the finest carbon particles (for example, these could be bag filters, ceramic filters, etc.).
A treating device 6 is connected to the cooling and separating member 4 to treat the pyrolysed gas Gp after it has passed into the cooling and separating member 4. The treating device is, in this case, a pressure swing adsorption (PSA) device.
In the embodiment described in this case, the gas G to be treated is a hydrocarbon gas and more specifically methane of chemical formula CH4.
The pyrolysis reaction of methane CH4 is done according to the following reaction:
CH4->2H2+C
The pyrolysis temperature of methane is well-known to a person skilled in the art, and is between 1000° C. and 1100° C. and makes it possible to produce, on the one hand, carbon which constitute solid particles S, recovered by the collecting means 5 of the machine which is the subject matter of the invention and, on the other hand, mainly dihydrogen H2 after passing through the treating device 6 of the machine which is the subject matter of the invention.
Pyrolysis is, in this case, performed in the tube 2 which constitutes a current passage tube, as is more specifically illustrated in
Naturally, the tube 2 must be made of an electrically and thermally conductive, and high temperature-resistant material. Preferably, the tube 2 is made of metal alloy (for example, of Inconel), of tantalum, of steel of reference 602 CA, of molybdenum or any other heat-resistant steel which can be used at a very high temperature (i.e. at more than 1200° C.).
Further to its conduction and high temperature-resistance capacities, the tube 2 must be shaped, such that the exchange surface between the tube 2 and the gas to be pyrolysed is as large as possible.
Thus, the inventors have determined that the optimal configuration of the tube 2 is a tube which is helically wound about a longitudinal axis to form a spiral with a diameter, a deployed length, a bending diameter and a number of turns defined according to the nature and the pyrolysis temperature of the gas to be treated, according to the transit time and the minimum speed of the gas to be treated in the reactor and according to the ratio between the quantity of electrical energy necessary to heat the tube 2 by Joule heating and the chemical energy necessary for the pyrolysis reaction.
The diameter of the tube 2 must be reduced as much as possible to guarantee a high convective exchange coefficient between the gas to be treated and the internal surface of the tube. The exchange coefficient is better when the circulation speed of the gas to be treated is high. Thus, the inventors have established that the diameter of the tube 2 is defined so as to obtain a propagation speed of the gas to be treated in the reactor of at least 15 m/s to 20 m/s. Such a speed enables the driving of solid particles through gas streams during the process of the pyrolysis reaction, by thus avoiding the deposition of carbon particles on the inner surface of the tube. Such a speed also enables an optimal adjustment for a cyclonic separation of the particles S in the cooling/separating member 4 at the reactor outlet. The reduced diameter of the tube 2 imposes a long length of the tube 2 to guarantee a sufficient exchange surface to transmit the total thermal power necessary to achieve the desired heating of the gas to the pyrolysis temperature, and also to absorb the transformation energy from the methane into dihydrogen. The helical shaping of the tube 2 therefore makes it possible to combine a diameter as narrow as possible with a long deployed length for a size which is as limited as possible.
Preferably and as particularly illustrated in
Thus, the hydrocarbon gas G enters into the reactor, circulates in the tube 2 in which it is pyrolysed and, leaving the reactor, the pyrolysed gas Gp is sent into the separating member 4 which cools and separates the solid particles S from the pyrolysed gas Gp. Yet, as already mentioned, the chemical reaction of pyrolysis of the gas G produces solid carbon particles S and pyrolysed gas Gp, which makes it necessary to separate the solid particles S and the pyrolysed gas Gp. The passing of the pyrolysed gas through the cyclone of the separating member 4 makes it possible to cool and separate, on the one hand, the solid particles S, mainly consisting of carbon, which will be collected in the collecting means 5 and, on the other hand, the pyrolysed gas Gp. The heavier solid carbon particles S will, under the effect of gravity and the cyclonic effect, be separated from the pyrolysed gas Gp and fall into the collecting means 5. The carbon particles thus collected can be valuated in the industry as carbon black, in particular, the tyre industry, water treatment, plastics processing, or the automotive industry.
Furthermore, the pyrolysed gas Gp obtained at the outlet of the reactor is a gaseous mixture consisting of dihydrogen (H2) and non-pyrolysed or poorly pyrolysed residual gases (otherwise called off-gases), that is why, it is necessary that pyrolysed gas Gp is treated through the treating device, in order to separate the dihydrogen H2 from the off-gases. During its passing through the cooling/separating member 4, the pyrolysed gas Gp is also cooled to return to a temperature close to the ambient temperature, before being sent into the treating device 6 intended to separate the dihydrogen from the other residual gases.
At the machine outlet, the user therefore collects carbon and dihydrogen, dihydrogen that they can then condition for a later use.
They also recover residual gases. In order to improve the environmental and energy performance of the machine, the residual gases are preferably recovered at the outlet of the treating device to power the engine or the gas turbine 3a which generates some of the current necessary for powering the reactor. If necessary, the off-gases can be reinjected into the machine to follow a new complete treating cycle.
In the preferred embodiment of the invention, the machine comprises, upstream of the reactor, a gas G preheating device. This preheating device 1 preferably comprises a heat exchanger 1a comprising a “cold” circuit in which the gas G circulates and a “hot” circuit la in which a heat-transfer fluid circulates. Preferably, the heat-transfer fluid can be constituted by the exhaust gas of the gas engine of the power supply circuit 2. Such an arrangement is particularly interesting during the start-up of the machine, in order to optimise the pyrolysis reaction in the tube 2. Moreover, the energy recovered during the passing of the treated gas through the separating and cooling member(s) can also be directed to the heat exchanger 1a. Indeed, the higher the temperature of the gas G entering into the tube 2 is, the quicker the gas G will reach the pyrolysis temperature in the tube 2, the quicker the pyrolysis reaction along the tube will occur, and the better the yield of the reaction will be. The gas to be treated will preferably be preheated to reach a temperature of around 100 to 300° C.
In an integrated installation for producing hydrogen, according to the invention, the integrated installation has an inlet directly connected to a gas source to be treated, in this case, methane. A person skilled in the art will know how to use the connections, valves, and pipes suitable for the circulation of the gas to be treated and for the supply flow rate of the latter. The methane to be treated can come directly from a gas distribution network, of gas reservoir or biogas. A person skilled in the art will also know how to adapt the gas circulation parameters in the installation, according to the features of the gas, like pressure and the inlet temperature of the gas in the installation.
Thus, the installation according to the invention comprises:
Furthermore, the temperature of the gas to be treated can be controlled at any time, thanks to temperature sensors making it possible to finely control the preheating device 1, 1a and the electrical power necessary for the power supply of the tube 2. In particular, the installation can comprise residual gas distribution means according to which they undergo another treatment cycle, or that they are used to power the engine or the gas turbine 3a.
The installation can also comprise means for controlling the engine or the gas turbine according to the residual gases received, such that the current generated can correctly power the installation for an optimum operation.
In the particular embodiment illustrated by
Thus, the installation according to the invention is fully integrated and makes it possible to produce dihydrogen by pyrolysis from a hydrocarbon gas source, in particular from methane, locally and with a good energy and environmental performance: the installation can be sized, in particular concerning the number and the sizing of the tube sections according to the local dihydrogen production needs, the pyrolysis of methane does not produce CO2, the carbon particles are enhanced in the industry and the residual gases are reinjected into the installation for its operation.
The two examples below have particular implementations of the invention.
Example 1: Sizing of the machine according to imposed inlet parameters and to the volume flow rate of the gas to be treated.
Hypothetically:
That is Qv, the volume flow rate of methane to be treated, expressed in Nm3/h, then the following estimated sizing elements are obtained:
Example 2: Configuration of the machine according to the invention for producing dihydrogen from methane, according to the following features:
The inventors consider that the temperature to be obtained in the tube to perform the pyrolysis is around 1100° C. Indeed, the theoretical pyrolysis temperature of methane is between 1000° C. and 1100° C.
The required energy calculated to achieve the temperature increase and the pyrolysis of methane is 70 kW, by applying a 20% margin on this value to cover possible losses, the inventors consider that the energy required is 84 kW.
According to these parameters and according to a more precise calculation based on the general formulas presented above, the configuration of the tube 2 is as follows:
the power supply of the machine must be able to supply 84 kW, an electrical generator capable of supplying at least 94 kW should therefore be installed.
At the outlet, and considering a conversion yield of 80%, the machine produces:
The residual gases, if they are recycled to supply the gas engine of the machine, making it possible to supply between 40% and 50% of the electrical power necessary.
Naturally, at the machine outlet, it is necessary to provide a system for compressing hydrogen for an injection into a dedicated network, or to reach a pressure of 350 bars or 700 bars, pressure at which hydrogen is generally stored.
Such a dihydrogen production subject to a dihydrogen purity of 99.999% from methane could make it possible to supply vehicles.
Naturally, the invention is not limited to the embodiment described, but covers any variant coming within the scope of the invention such as defined by the claims.
In particular, the machine, the installation and the method of the invention partially apply to methane, but they can also apply to any hydrocarbon gas, such as butane, propane, etc., or any other synthesis gas obtained by methanisation, pyrolysis or gasification of biomasses or waste.
The reactor can equally be installed vertically or horizontally.
Although, in this case, one or more cyclones are used as a cooling and separating member, it is possible to use a cooling member to cool the pyrolysed gas, then at the outlet of the cooling member, send the cooled pyrolysed gas into a distinct separating member to separate the solid particles from the pyrolysed gas.
For example, although the treating device is, in this case, a pressure swing adsorption device. A person skilled in the art can use any other treating device making it possible to separate dihydrogen from off-gases.
The power supply circuit can mix different energy sources, for example, from among the following: electrical network, battery, solar panels, wind turbines, hydroelectricity, turbines, generator, etc.
Although the electrical power delivered to each tube section of the integrated installation is identical, it can also be different according to the tube sections, so as to finely manage the temperature profiles.
Although the tube sections of the installation are, in this case, mounted in series, they can also be mounted in parallel. A person skilled in the art will thus know how to adapt the inlet and the outlet of the gas to be treated.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2112955 | Dec 2021 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/084132 | 12/1/2022 | WO |
