ES2990042B2 - Cracking device and process for obtaining hydrogen and pyrolytic oils - Google Patents

Description

DESCRIPTION

CRACKING DEVICE AND PROCESS FOR OBTAINING HYDROGEN AND PYROLYTIC OILS

TECHNICAL SECTOR

The present invention falls within the field of devices, systems and procedures for the production of hydrogen gas and pyrolytic oils from the valorization of reject material.

BACKGROUND OF THE INVENTION

Conventional hydrogen production technologies include steam reforming of natural gas (methane) and oil, catalytic decomposition of natural gas, partial oxidation of heavy hydrocarbons, and gasification of coal or coke.

Waste conversion processes can be divided into thermochemical and biochemical techniques, which differ in energy requirements, operating conditions (temperatures and pressures), raw material inputs, efficiencies, reaction times, and final yields. In general, thermochemical processes, such as gasification and pyrolysis, are faster than biochemical processes (e.g., fermentation), have higher stoichiometric hydrogen yields, higher conversion efficiencies, and shorter reaction times. However, biochemical processes are less energy-intensive, as they operate under moderate energy conditions, resulting in lower hydrogen yields.

Hydrogen can be produced from a mixture of waste rejects and biomass through thermal gasification, followed by the cleaning and purification of the resulting synthesis gases. However, these processes rely primarily on gasification, where pyrolysis and gasification reactions occur in the same reactor, making it impossible to precisely control the parameters of each reaction. In these processes, all fractions present in the raw materials used are gasified (both biogenic and plastic fractions), resulting in the production of both renewable and non-renewable hydrogen.

The invention described here outlines a system and process for the valorization of waste material, enabling the production of hydrogen and pyrolytic oils, two high-value compounds, through a pyrolysis/gasification process that combines different stages and processes. The key feature of this process is its ability to extract the highest-value compound from each fraction (biogenic and plastic) from a heterogeneous mixture of these fractions without prior physical separation.

EXPLANATION OF THE INVENTION

In a first aspect, the invention provides a biogenic material cracking device for the generation of chemical products including syngas (synthesis gas), as defined in the claims.

The cracking device, hereinafter referred to as the device, is designed to be fed with gases from thermal processes used to treat organic materials, such as biomass or certain waste materials. These thermal treatments may include torrefaction, pyrolysis, gasification, or any other process that results in a gas stream requiring post-treatment. Specifically, the gases fed to the device are from a previous stage of selective pyrolysis of a biogenic fraction of a waste material. This pyrolysis is carried out at temperatures below 350°C, yielding partially pyrolyzed waste material and a mixture of permanent gases, condensable volatile gases, and condensable compounds. The condensable volatile gases are converted into permanent gases through cracking within the device.

The device comprises a cracking chamber through which the gases to be cracked move from an inlet that enables their entry into the chamber until an outlet through which the cracked gas/syngas exits, where, preferably, the cracking of the gases is carried out at a temperature between 700 and 1200°C.

Inside the cracking chamber is a cracking unit configured to preheat the gas to be cracked and to crack the preheated gas, generating syngas (synthesis gas). The chamber-cracking unit arrangement allows the inlet gas temperature to be used to preheat the gases to be cracked, and also allows the heat from already cracked gases to be reused in preheating the gases to be cracked, increasing the device's thermal efficiency.

The cracking assembly comprises at least one outer tube arrangement to which an inner tube is concentric, preferably a plurality of such arrangements conveniently distributed within the chamber. In each arrangement, gases from the inlet circulate on the outside of the outer tube, such that the gases to be cracked circulate through a space between the outer and inner tubes, and a combustion gas circulates within the inner tube to crack the gas circulating in the space between the outer and inner tubes. In this way, the gases moving on the outside of the outer tube exchange heat with the gas moving in the space between the outer and inner tubes, producing preheating. Furthermore, the gases moving on the outside of the outer tube are directed into the space between the outer and inner tubes to be cracked.

The device also comprises at least one burner linked to each outer tube and inner tube arrangement, the burner being configured to heat the inner tube to produce cracking, wherein a fraction of the inlet gas is selectively distributed to said burner.

Gas cracking takes place at a temperature of at least 1200°C, where this temperature is maintained for at least two seconds as the gas passes through the space between the outer and inner tubes. In this process, the burner, by burning the combustion gas, raises the temperature of the tube to over 1500°C.

In addition to the above, the cracking device incorporates baffle plates that are spaced apart inside the cracking chamber, where these baffle plates support the cracking assembly, forming a circuit through which the gases from the inlet move around the outer tube of the array or arrays.

In one embodiment, the device comprises a manifold connected to the burner, i.e., to each burner, wherein said manifold is configured to direct the gas to be burned towards said burner and a pressurization chamber provided for introducing pressurized air towards each burner.

In another embodiment of the device, it comprises a regulating valve configured to split the gas into a combustion stream directed to the burner and a cracking gas stream directed to the cracking chamber, wherein said regulating valve is controlled based on the temperature of the cracking gas.

As can be seen from the above, one of the advantages of the cracking device of the invention is that it does not use any catalyst for cracking. Furthermore, the cracking of the gases is carried out indirectly, thus avoiding the mixing of the combustion gases with the cracked gases to thermally sustain the cracking process, thereby achieving greater purity and higher calorific value.

In a second aspect, the invention relates to a process for obtaining hydrogen and pyrolytic oils comprising the following steps:

a) selective pyrolysis of the biogenic fraction of the reject material at less than 350 °C, where partially pyrolyzed reject material and a mixture of permanent gases and condensable compounds are obtained;

b) selective pyrolysis of the synthetic fraction of the partially pyrolyzed reject material resulting from the previous stage, at high temperature, between 400-520°C where synthetic carbon and pyrogas are obtained;

c) indirect thermal cracking of the mixture obtained in step a) between 700 and 1,200 °C, where syngas is obtained, and where the thermal cracking takes place in a cracking device according to the first aspect of the invention;

d) gasification of the coal generated in stage b) at temperatures between 800 and 1,200 °C by means of air currents and/or water vapor;

e) condensation of the synthetic pyrogas generated in the high-temperature pyrolysis stage to obtain pyrolytic oils;

f) catalytic water displacement reaction from the syngas obtained in step c);

g) separation and storage of the hydrogen gas resulting from the previous stage, where stages a) to d) are carried out in separate reactors.

The described invention outlines a process for valorizing waste material, enabling the production of hydrogen and pyrolytic oils, two high-value compounds, through a pyrolysis/gasification process that combines different stages and processes. The advantage of this process lies in extracting the highest-value compound from each fraction (biogenic and plastic) from a heterogeneous mixture of these fractions without prior physical separation.

In the process of the invention, the different stages of pyrolysis, gasification, and indirect cracking occur in dedicated reactors, thus achieving precise control of the parameters of each reaction. The process allows for the production of hydrogen gas and pyrolytic oils from waste material. The biogenic fraction of this material, which includes paper, cardboard, biomass, and organic waste, is used for the production of renewable hydrogen. It is worth noting that hydrogen is considered renewable when it is produced from this biogenic waste. Furthermore, the process of the invention allows for the utilization of the synthetic fraction of waste material, such as plastics that can no longer be recycled, to obtain pyrolytic oils that can be used in the manufacture of recycled plastics, such as polyethylene, polypropylene, and polystyrene.

Additionally, the process allows for the revaluation of rejected material, a waste that can no longer be recovered and that has traditionally ended up being buried in landfills or sent to incinerators.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1.- Cracking device.

Figure 2. Schematic of the process for obtaining hydrogen gas and pyrolytic oils from reject material comprising a biogenic fraction and a synthetic fraction.

List of references and figures:

1. Gas inlet to the cracking chamber 7

2. Cracked gas outlet

3. Cracking chamber housing

4. Burner/burners

5. Inner tube

6. Outer tube

7. Cracking chamber

8. Deflector plates

10. Reject material inlet line

20. Pyrogas line of the biogenic fraction

30. Syngas line of the biogenic fraction

40. Syngas line mixing of the biogenic fraction

50. Enriched H2 line

60. H2 Line

70. Line of pyrogases of the synthetic fraction

80. Permanent gas line of the synthetic fraction

90. Permanent gas line of the biogenic fraction

100. Combustion flue line

110. Pyrolytic oil line

120. Char line

130. Ash line

140. Gasifier syngas line

150. Pyrolysis stage of the biogenic fraction

160. Pyrolysis stage of the synthetic fraction

170. Char gasification stage

180. Pyrogen filtration stage

190. Pyrogen cracking stage of the biogenic fraction

200. Syngas mixture cleaning and conditioning stage 210. Water displacement reaction stage

220. H2 separation stage

230. H2 storage stage

240. Cleaning and conditioning stage of synthetic fraction pyrolytic 250. Pyrolytic oil condensation stage

260. Combustion stage of permanent gas streams

270. Combustion fume cleaning stage

PREFERRED EMBODIMENT OF THE INVENTION

In the preferred embodiment, the invention provides a biogenic material cracking device for the generation of chemicals including syngas (synthesis gas), wherein the gases to be cracked come from previous pyrolysis processes of reject material, and wherein the gases from a selective pyrolysis process of a biogenic fraction of the reject material at less than 350 °C enter the cracking device, in which partially pyrolyzed reject material and a mixture of permanent gases and condensable compounds are obtained.

As shown in Figure 1, in the preferred embodiment, the cracking device comprises a cracking chamber 7 whose body resembles a heat exchanger with two groups of concentric tubes and a shell. Inner tubes 5, where combustion occurs, raising the temperature to crack the gases, are made of a special refractory material resistant to high temperatures and with a high thermal conductivity coefficient. Outer tubes 6, each positioned concentrically to the inner tubes 5, are also made of a refractory material, but with different characteristics, since they do not have to withstand the high combustion temperatures nor do they require such high conductivity.

Returning to the cracking chamber 7, this is preferably square in cross-section to optimize the arrangement of the inner tubes 5 and outer tubes 6, and is optionally made of metal to reduce the overall weight of the device. Each arrangement of inner tubes 5 and outer tubes 6 will be supported by baffle plates 8 distributed along the length of the cracking chamber 7. These plates also function as a labyrinth for the circulation of the gases to be cracked, which are preheated before the actual cracking process, and also optimize the internal preheating of the chamber 7.

Now, as stated above, the cracking device is preferably configured in a shape similar to a shell and tube heat exchanger, therefore comprising concentric tube arrangements supported by baffle plates 8 inside the cracking chamber 7. This tube arrangement is primarily intended for the indirect heating of the gases to be cracked, by means of the process gases or the already cracked gases.

Thus, each assembly consists of an inner tube 5 concentric to an outer tube 6, said tubes 5 and 6 being made of refractory steel. The gases to be cracked circulate through the space between these tubes 5 and 6. An outer shell 3, together with the baffle plates 8, creates a labyrinth that increases heat exchange. This shell 3 will be suitably insulated since the cracking temperature will be up to 1,200°C.

The inner tubes 5, in which combustion takes place, are hermetically sealed from the casing 3 to prevent the mixing of combustion fumes with the gases to be cracked or cracked. These inner tubes 5 are positioned at their front end on a base plate, which has a combustion chamber (not shown) for the combustion air supply plenum used in the burners 4.

Furthermore, each of the internal tubes 5 is associated with an automatic ignition burner 4, with ionization flame control and automatic operation without a pilot burner. Gas is supplied to these burners 4 via a blower (not shown) at a pressure of 0.5 bar, which also regulates the temperature using a signal from the cracked gases.

The combustion chamber includes an air inlet (not shown) supplied by a centrifugal fan (not shown) with the appropriate pressure to feed the burners 4, and is therefore combined with the blower. Both the fan and blower can be powered by the same motor, which simplifies regulation.

On the other hand, the cracking device includes a diverter valve (not shown) for the combustion gases in the inner tube 5, depending on the cracking temperature demand. This valve is automatically controlled by a positioner, which, at startup, directs a greater quantity of combustion gas until the operating temperature is reached. This operation is perfectly balanced because the combustion gases are continuously and automatically balanced with the cracking gases.

The cracking device also includes a heat exchanger arranged at the outlet of the combustion gases, which is configured to preheat the air to be used in combustion or oxidizer and thus increase the thermal efficiency of the device.

Now, with respect to the gas cracking procedure using the device of the invention, it comprises the following stages:

- distribution of the gas to be cracked into two streams, channeling part of this gas for combustion towards the burners 5 and thus providing the energy needed for cracking, and another part to direct it towards the inlet 1 and introduce it into the cracking chamber 7, the diverter valve controlled by the temperature of the gas to be cracked is responsible for directing the gas flow;

- direct the gas to be burned/combusted towards a collective collector that distributes said gas to the burners 4 arranged inside the inner tube 5 that allows temperatures above 1,500 °C;

- introduction of combustion air into the slightly pressurized chamber (0.5 Bar) from which the necessary air is supplied to each burner 5, where said air has been preheated in a heat exchanger using any heat source available in the installation, for example, from the already cracked gases or the combustion gases themselves;

- introduction of the gases to be cracked into the cracking chamber 7 where the tube arrangement 5, 6 is located, where the baffle plates 8 circulate the gas to be cracked in a labyrinth around the outer tubes 6 producing a preheating of them;

- the gases to be cracked, already preheated to a temperature close to the cracking temperature, pass through the space between the outer tubes 6 and the inner tubes 5, where combustion takes place, where in the passage through this space the gases reach a temperature of more than 1,200 °C and are maintained for more than 2 seconds, thus ensuring total cracking of all the gases; and

- The gas already cracked at a temperature above 1,200 °C is used to preheat the gas to be cracked from the thermal process of the reject material, so the consumption of the gas to be burned for cracking will be lower and the performance of the installation can be optimized.

The second aspect of the invention relates to a process for obtaining hydrogen gas and pyrolytic oils from waste material comprising the following steps:

a) selective pyrolysis of the biogenic fraction of the reject material at less than 350 °C, where partially pyrolyzed reject material and a mixture of permanent gases and condensable compounds are obtained;

b) selective pyrolysis of the synthetic fraction of the partially pyrolyzed reject material resulting from the previous stage at high temperature between 400-520 °C where synthetic carbon and pyrogas are obtained;

c) indirect thermal cracking of the mixture obtained in step a) between 700 and 1200 °C, where syngas is obtained, and where the thermal cracking takes place in a cracking device according to the first aspect of the invention;

d) gasification of the coal generated in stage b) at temperatures between 800 and 1,200 °C by means of air currents and/or water vapor;

e) condensation of the synthetic pyrogas generated in the high-temperature pyrolysis stage to obtain pyrolytic oils;

f) catalytic water displacement reaction from the syngas obtained in step c);

g) separation and storage of the hydrogen gas resulting from the previous stage, where stages a) to d) are carried out in separate reactors.

The pyrolysis of the different fractions of the reject material in different reactors allows precise control of the reaction conditions so that the products obtained, that is, biogenic and synthetic pyrogas, have particularly interesting characteristics for obtaining hydrogen gas and pyrolytic oils.

The term "waste material" refers to waste that cannot traditionally be separated by mechanical means and therefore cannot be recovered. This material is typically disposed of in landfills or used as fuel in incinerators. It comprises a heterogeneous mixture of plastic fractions (polyethylene, polypropylene, polystyrene, etc.) and biogenic fractions (wood, paper, cardboard, biomass, organic waste, etc.) in varying proportions.

The term "partially pyrolyzed reject material" refers to the solid material resulting from the selective low-temperature pyrolysis of the reject material where only the biogenic fraction of the reject material has been pyrolyzed.

The term "char" refers to the carbonaceous material resulting from the high-temperature pyrolysis of the reject material, which is also commonly called "cha?".

The term "permanent gases" refers to the gases obtained in a pyrolysis stage; these are usually gaseous mixtures of H2, carbon monoxide (CO), carbon dioxide (CO2) and water (H2O) in different proportions.

The term "syngas" refers to a mixture containing hydrogen (H2), carbon monoxide (CO) and other gaseous components, such as carbon dioxide (CO2), methane (CH4) and water vapor (H2O) in different proportions.

The term "pyrogas" refers to the gaseous mixture obtained from pyrolysis processes. This mixture generally contains hydrogen (H2), carbon monoxide (CO), as well as unreacted light and heavy hydrocarbons (especially methane (CH4), ethane (C2H6), propane (C3H8), and tar). Depending on the type of starting material, the composition of the pyrogas can vary; generally, pyrogas can be biogenic or synthetic.

The term "condensable products" refers to components resulting from pyrolysis that are in liquid or solid form at room temperature and atmospheric pressure. These products condense and are collected during the process, after the pyrolysis gases have cooled and condensed into liquids or solids.

The term "pyrolytic oils" refers to liquid products obtained through the pyrolysis of organic and/or synthetic materials. Their composition consists primarily of saturated, unsaturated, and aromatic hydrocarbons, and their characteristics can vary depending on the source of the materials and the processing conditions.

In the preferred embodiment of the process of the second aspect, the process comprises prior to step a) a pretreatment step of the reject material comprising drying, crushing, removal of inert materials and/or removal of metals.

In another preferred embodiment of the process of the second aspect, the operating temperature of the first pyrolysis stage is between 280°C and 350°C; while the operating temperature of the second pyrolysis stage is between 500 and 520°C.

In the most preferred embodiment of the process of the second aspect, the operating temperature of the first pyrolysis stage is between 280°C and 350°C; while the operating temperature of the second pyrolysis stage is between 500 and 520°C and the temperature of the indirect cracking of the biogenic pyrogas is between 700 and 1200°C.

The feed to the first pyrolysis stage (stage a) is carried out at room temperature and the feed temperature of the partially pyrolyzed material to the second pyrolysis reactor (stage b) is between 280 and 350 °C.

The temperature conditions in the selective pyrolysis stages and their corresponding feeding stages allow for maintaining a temperature gradient (temperature ramp) of 1°C/min to 20°C/min, preferably 1°C/min to 10°C/min, and even more preferably a gradient of 5°C/min. This gradient enables the production of the different products with excellent quality.

Additionally, the pyrolytic oils obtained in the second stage of selective pyrolysis continue to a condensation stage where the pyrolytic oils resulting from stage b) are condensed to obtain pyrolytic oils of excellent quality.

The process of the invention allows for obtaining two distinct fractions of pyrolysis oils with different compositions. The first comes from the selective pyrolysis of the biomass fraction of the reject material and is rich in oxygenated compounds (compounds that contain oxygen in their structure, in addition to carbon and hydrogen: benzoic acid, acetic acid, phenols, furfural, etc.) and nitrogenous compounds, such as caprolactams. This fraction, of low industrial value, is ideal for valorization through its transformation into hydrogen gas.

The second fraction obtained from the pyrolysis of the synthetic fraction of the reject material is rich in paraffins (linear hydrocarbons composed exclusively of carbon and hydrogen: heptane, octane, nonane...), olefins (linear hydrocarbons containing at least one carbon-carbon double bond, composed exclusively of carbon and hydrogen: 1-heptene, 1-octene, 1-nonene...) and aromatic compounds (hydrocarbons formed by cyclic compounds that form carbon-carbon double bonds: benzene, toluene, styrene, naphthalene), this fraction being of high industrial value.

In a preferred embodiment, the condensing units consist of a combination of shell and tube heat exchangers, in which a refrigerant fluid, such as air, thermal oil or water, circulates through the tubes, and the fuel gas circulates through the shell, configuring homogeneous cooling and progressive condensation.

In another embodiment of the second aspect of the process, the process includes filtration stages of the pyrolysis gas obtained in the selective pyrolysis stages a) and b). During filtration, ceramic filters and/or cyclones are used to retain solid impurities, mainly the particles generated in the pyrolyzers.

Preferably, the pyrogas obtained in step b) is subjected to a filtration step and a cleaning step. In a preferred embodiment, the pyrogas cleaning is carried out by adding Ca(OH)2 and/or NaHCO3 for the removal of acid gases and/or metals; and by adding carbon for the removal of dioxins and/or furans.

In another preferred embodiment, and in parallel with the previous embodiments, the procedure includes a stage of washing the gas resulting from indirect cracking.

In another preferred embodiment, the residence time of the reject material in the reactor of the first selective pyrolysis is between 1 and 3 hours, preferably approximately 2 hours.

In another preferred embodiment, the residence time of the reject material in the reactor of the second selective pyrolysis is between 1 and 3 hours, preferably approximately 2 hours.

In another preferred embodiment, the residence time of the mixture of permanent gases and condensable compounds (biogenic pyrogas) in the indirect cracking reactor is between 1 and 5 seconds, preferably approximately 2 seconds.

In the most preferred embodiment, the residence times of the reject material in the reactor of the first and in the reactor of the second selective pyrolysis are between 1 and 3 hours, preferably approximately 2 hours.

In this stage, the carbon monoxide (CO) present in the synthesis gas obtained in stage c) reacts with water molecules (H2O). This reaction is known as the "water displacement reaction." The water displacement reaction uses syngas, a mixture of hydrogen (H2) and carbon monoxide (CO), to react with water (H2O) and produce additional hydrogen gas (H2) and carbon dioxide (CO2). As a result of this reaction, hydrogen (H2) and carbon dioxide (CO2) are formed. The hydrogen produced is collected as a valuable product, while the remaining permanent gases are diverted to a cogeneration system.

In another preferred embodiment, the process includes a cleaning step for the syngas resulting from the indirect cracking of step c). This step is carried out by adding Ca(OH)₂ and/or NaHCO₃ to remove acid gases and/or metals, and by adding carbon to remove dioxins and/or furans. The objective is to remove any impurities that would impede the subsequent water displacement reaction of step d).

Preferably, the hydrogen obtained in step f) of the water displacement reaction is separated by pressure swing adsorption (PSA). This method takes advantage of the differences in the adsorption properties of the various gaseous components to achieve separation. PSA is used industrially for the separation of H2 from synthesis gas and allows obtaining H2 at practically the inlet pressure and an off-gas or tail gas stream containing a mixture of N2, CO2, CO, and CH4.

In step d), the carbon resulting from the second selective pyrolysis undergoes a gasification process. The carbon is converted into a combustible gas by reacting with a gasifying agent, such as water vapor (H2O), air, or carbon dioxide (CO2), at elevated temperatures. This process is carried out in the absence of oxygen (anoxia) or under oxygen-limited conditions to prevent complete combustion of the carbon and to obtain a gas rich in hydrogen and carbon monoxide, known as synthesis gas or syngas.

In step d), the mixture of coal and gasifying agent is introduced into the gasification reactor, which is heated to high temperatures, in the range of 800°C to 1,200°C. Preferably, the temperature of the gasification reactor during gasification is approximately 1,000°C. In step d), air and steam are used as gasifying agents in a ratio of 4:1.

In another preferred embodiment, the permanent synthetic gas, which comes from the second condensation stage of the synthetic pyrogas, will be recirculated to a cogeneration system, with the capacity to generate thermal and electrical energy to supply the different elements of the process itself.

Likewise, the excess thermal energy from the cogeneration system can be redirected to raise and/or maintain the temperature of the pyrolysis stages so that complete thermal and electrical utilization of the permanent gases obtained from the synthetic fraction of the reject material is achieved.

In this way, and according to previous implementations, the permanent gases are reused to reach and maintain operating temperatures without the need for external fuel gases. Furthermore, a portion of the permanent synthetic gas is reused for energy generation, enabling the plant where the process of this invention is installed to be self-sufficient.

Preferably, the process includes a flue gas cleaning stage for the cogeneration system. This flue gas cleaning stage comprises: a catalytic stage for NOx removal, the injection of a powdered additive (NaHCO3 or Ca(OH)2) for the removal of acid gases (SO2, HCl), and a filtration stage for the removal of solid material that may be generated during combustion.

Having sufficiently described the nature of the present invention, as well as the manner of putting it into practice, it is not considered necessary to make its explanation more extensive so that any expert in the field may understand its scope and the advantages that derive from it, it being noted that, within its essentiality, it may be put into practice in other forms of embodiment that differ in detail from the one indicated as an example, and to which the protection sought will also extend provided that its fundamental principle is not altered, changed or modified.

Claims (15)

1. Biogenic material cracking device for the generation of chemical products including syngas (synthesis gas), comprising: - a cracking chamber (7) through which the gases to be cracked move from an inlet (1) that enables their entry to an outlet (2) of cracked gas/syngas; - a cracking assembly disposed inside the cracking chamber (7) configured to preheat the gas to be cracked and to crack the preheated gas generating syngas, said cracking assembly comprising at least an outer tube (6) to which an inner tube (5) is concentric, wherein the gases from the inlet (1) circulate on the outside of the outer tube (6), wherein the gases to be cracked circulate through a space between the outer tube (6) and the inner tube (5) for cracking at a temperature of at least 1200°C sustained for at least 2 seconds, and wherein a combustion gas circulates through the inside of the inner tube (5) to crack the gas circulating in the space between the outer tube (6) and the inner tube (5), and wherein the gases moving on the outside of the outer tube (6) exchange heat with the gas moving through the space between the outer tube (6) and the inner tube (5); and where the gases moving on the outside of the outer tube (6) are directed towards the space between the outer tube (6) and the inner tube (5); and - at least one burner (4) configured to heat the inner tube (5), where a fraction of the inlet gas (1) is selectively distributed to said burner (4). 2. Cracking device according to the preceding claim comprising deflector plates (8) arranged at intervals inside the cracking chamber (7), wherein said deflector plates (8) support the cracking assembly forming a circuit through which the gases from the inlet (1) move around the outer tube (6). 3. Device according to the preceding claim comprising a manifold connected to the burner (4) configured to direct the gas to be burned towards said burner (4) and a pressurization chamber provided to introduce air towards the burner (4). 4. Device according to any of the preceding claims comprising a regulating valve controlled by the temperature of the gas to be cracked, configured to divide the gas into a combustion stream directed to the burner (4) and a cracking gas stream directed to the cracking chamber (7); 5. Device according to any of the preceding claims wherein the cracking assembly comprises a plurality of concentric outer tube (6) and inner tube (5) arrangements with a burner (4) associated with each inner tube (5). 6. Process for obtaining hydrogen gas and pyrolytic oils from reject material characterized in that it comprises the following stages: a) selective pyrolysis of the biogenic fraction of the reject material at less than 350 °C, where partially pyrolyzed reject material and a mixture of permanent gases and condensable compounds are obtained; b) selective pyrolysis of the synthetic fraction of the partially pyrolyzed reject material resulting from the previous stage at high temperature between 400-520 °C where synthetic carbon and pyrogas are obtained; c) indirect thermal cracking of the mixture obtained in step a) between 700 and 1200 °C, where syngas is obtained, and where the thermal cracking takes place in a cracking device according to any of claims 1 to 5; d) gasification of the coal generated in step b) at temperatures between 800 and 1200 °C by means of air and/or steam currents; e) condensation of the synthetic pyrogas generated in the high-temperature pyrolysis stage to obtain pyrolytic oils; f) catalytic water displacement reaction from the syngas obtained in step c); g) separation of the hydrogen gas resulting from the previous stage. where steps a) to d) are performed in separate reactors. 7. The process for obtaining hydrogen from reject material according to the preceding claim, wherein the process comprises prior to step a) pretreatment of the reject material comprising drying, crushing, removal of inert materials and/or removal of metals. 8. The process for obtaining hydrogen from waste material according to any of the preceding claims 6-7, wherein the first stage of selective pyrolysis of the biogenic fraction is carried out at a temperature between 280°C and 350°C, and the second stage of selective pyrolysis of the synthetic fraction is carried out at a temperature between 500°C and 520°C. 9. The process for obtaining hydrogen from reject material according to any of the preceding claims 6-8, wherein the feeding stage of the second pyrolysis stage is carried out at a temperature between 280°C and 350°C. 10. The process for obtaining hydrogen from reject material according to any of the preceding claims 6-9, wherein the residence time of the reject material in the first pyrolysis reactor is between 1 and 3 hours. 11. The process for obtaining hydrogen from reject material according to any of the preceding claims 6-10, wherein the residence time of the partially pyrolyzed reject material in the second pyrolysis reactor is between 1 and 3 hours. 12. The process for obtaining hydrogen from reject material according to any of the preceding claims 6-11, wherein the residence time of the pyrogas resulting from selective pyrolysis of the biogenic fraction in the indirect cracker is between 1 and 5 seconds, preferably approximately 2 seconds. 13. The process for obtaining hydrogen from waste material according to any of claims 6-12 above, wherein the synthetic pyrogas resulting from step b) passes through the steps of: - cleaning of synthetic pyrotechnics at a temperature between 450°C and 520°C; and - condensation in a condensation unit, configured to separate at least a liquid fraction, and at least a permanent synthetic gas fraction. 14. The process for obtaining hydrogen from waste material according to any of the preceding claims 6-13, characterized in that it comprises a stage of storing hydrogen gas from stage g) in a gas tank. 15. The process for obtaining hydrogen from waste material according to any of the preceding claims 6-14, wherein the permanent gases resulting from steps e) and f) are used as fuel in a cogeneration system for the production of thermal and electrical energy.