Method for converting waste materials into valuable materials and system for implementing the same

Abstract

The present invention relates to the material valorization of waste by thermochemical processing to obtain high value added products such as hydrogen and hydrocarbons or alcohols, and to a system for carrying out the same.

Description

Detailed Description of the Invention

[0001] OBJECTS OF THEINVENTION The present invention relates to material recovery of waste materials by thermochemical processing to obtain high added value products.

[0002] BACKGROUND OF THEINVENTION Currently, a large amount of waste generated by human activities is piled up in landfill sites. Due to the socio-economic and environmental damage caused by waste, it is desirable to develop waste recycling technologies to reduce the amount of waste that has no useful purpose.

[0003] Recovery routes include, inter alia, energetic routes, such as incinerating the waste to generate electricity, and material routes, such as converting the waste into different chemicals, such as hydrogen, hydrocarbons or alcohols.

[0004] An example of energy recovery is described in patent publication number EP2318157, which proposes a system and method for the pyrolytic treatment of municipal and domestic waste. The waste passes through a sorting unit, a crushing unit, a drying unit and an accumulation unit in sequence, and is sent to a pyrolysis reactor for pyrolytic treatment. The synthesis gas produced in the pyrolysis is used as the working medium of a power generation unit after a series of cleaning steps. Carbon dioxide is also recovered in the process as a result of the synthesis gas purification process. The purpose of this recovery is to obtain energy and carbon dioxide.

[0005] The patent with publication number US10280377 describes a system comprising a pyrolysis chamber and a steam cracking unit to obtain synthesis gas for use in the cogeneration of energy and / or steam.

[0006] In the technical literature, waste valorization is energetic and material. In the present invention, a method has been developed that produces hydrogen, hydrogen and hydrocarbons, or hydrogen and alcohols, and is exclusively material valorization with maximum efficiency in terms of the products obtained.

[0007] Description of the Invention Due to growing environmental concerns and increasingly stringent regulations, efficient management of municipal, industrial and agricultural solid wastes has become an increasingly important issue.

[0008] The objective of valorization is to convert waste materials into higher value added products or into feedstocks for other uses and processes, thereby providing environmental and economic benefits by preventing the accumulation of waste in landfills.

[0009] The present invention describes a method and system based on the thermal treatment of waste materials to produce a variety of value-added products such as hydrogen, hydrocarbons or alcohols. Furthermore, hydrogen production can be enhanced when co-produced with hydrocarbons or alcohols by integrating process streams.

[0010] The method of the present invention comprises a pyrolysis reaction, in which the starting waste is decomposed under a reducing atmosphere by external heating of the reactor. The solid phase obtained from the pyrolysis product can be optionally separated. After pyrolysis, the method comprises a step of cracking the pyrolysis product, in which the pyrolysis product is reacted in the presence of oxygen and steam to obtain synthesis gas. At the outlet of the cracking step, the raw synthesis gas obtained is cooled and purified.

[0011] A portion of this gas is mixed with steam and reacted in the presence of a catalyst to obtain a hydrogen-rich syngas, a portion of which is treated to extract hydrogen as a product, and the remainder is mixed with a previously unused fraction of the purified syngas and reacted in the presence of a second catalyst to obtain a second product derived from the syngas.

[0012] In this way, due to the co-production of hydrogen and a second product (hydrocarbon or alcohol), synergies arise in the integration of the process, which allows a better productivity than in processes producing hydrogen as the only product. Thus, starting from the same amount of feedstock, more hydrogen is obtained by co-production than if hydrogen were the only product, in addition to a significant amount of a second product with high added value.

[0013] Thus, a first aspect of the present invention relates to a method for the valorization of waste for the co-production of hydrogen and hydrocarbons or alcohols, comprising the steps of: a) subjecting the starting waste to pyrolysis under external heating and a reducing atmosphere to obtain a pyrolysis product; b) optionally separating a solid fraction from said pyrolysis product; c) cracking the product obtained in the pyrolysis step a) or the product obtained in step b) after separating the solid fraction in the presence of oxygen and a first steam stream to obtain a raw synthesis gas; d) cooling the raw synthesis gas obtained in c); e) purifying the raw synthesis gas obtained in d) to obtain a purified synthesis gas; f) converting the mixture of the first preheated fraction of said gas obtained in e) with a second vapor stream in the presence of a catalyst to obtain a hydrogen-enriched synthesis gas; g) separating hydrogen from the first fraction of the hydrogen-enriched syngas to obtain hydrogen and a tail gas from the separation of said hydrogen; h) synthesizing a product selected from a hydrocarbon or an alcohol from the preheated mixture of the second gas fraction obtained in e) and the second fraction of the hydrogen-enriched synthesis gas obtained in f); i) fractionating and / or purifying the product obtained in h) to obtain different streams of hydrocarbons or alcohols, a process water stream, and said process tail gas stream. Here, steps f) to g) and steps h) to i) are parallel in time.

[0014] The invention also relates to a hydrogen production method that integrates different process streams to obtain hydrogen as the only product, said method comprising the same steps a) to g) described in the previous paragraph. To improve the efficiency of hydrogen production, the external heating in step a) is carried out by combustion of a stream selected from a part of the tail gas from step g) and / or a part of the purified synthesis gas from step e), mixed with a preheated air stream, thereby generating an exhaust gas stream that releases heat for said external heating of step a) and, after said pyrolysis step, to a stream and / or fraction selected from: a water stream for generating the steam required for steps c) and / or f), and / or an air stream for obtaining said preheated air stream, and / or a purified synthesis gas fraction treated in step f). The invention therefore relates to a waste material valorization method for hydrogen production, comprising the following steps: a) subjecting the starting waste to pyrolysis under external heating and a reducing atmosphere to obtain a pyrolysis product; b) optionally separating a solid fraction from said pyrolysis product; c) cracking the product obtained in step a) of said pyrolysis or the product obtained in step b) after separation of the solid fraction in the presence of oxygen and a first steam stream to obtain a raw synthesis gas; d) cooling the raw synthesis gas obtained in c); e) purifying the raw synthesis gas obtained in d) to obtain a purified synthesis gas; f) converting the mixture of the first preheated fraction of said gas obtained in e) with a second vapor stream in the presence of a catalyst to obtain a hydrogen-enriched synthesis gas; g) separating the hydrogen-rich synthesis gas to obtain hydrogen and a tail gas from the hydrogen separation; The method further comprises a step of mixing and combusting a fuel stream selected from a portion of the tail gas from step g) and / or a portion of the purified synthesis gas from step e) with a preheated air stream; thereby generating an exhaust gas stream which releases heat to the external heating of step a) and, after the pyrolysis step, to at least one stream and / or fraction selected from: a water stream for generating the steam required for steps c) and f), and / or an air stream for obtaining the preheated air stream, and / or a first fraction of the gas obtained in e) preheated in f).

[0015] The term "material valorization" refers to the utilization of waste materials to obtain raw material products that can be used in socio-economic activities.

[0016] The term "waste" in this specification relates to materials discarded from other processes and capable of undergoing chemical decomposition by heating to produce at least combustible gases, examples of which include solid municipal waste, waste from industrial activities or biomass waste.

[0017] The term "pyrolysis" refers to pyrolysis under a reducing atmosphere.

[0018] The term "external heating" relates to indirect heating, i.e. heat is supplied from outside by electrical heating, external combustion or other means.

[0019] The term "cracking" in the present invention relates to the thermochemical conversion of tar into lower molecular weight molecules, optionally in the presence of a catalyst.

[0020] The term "tar" in the present invention relates to organic compounds with a molecular weight higher than methane that exit the pyrolysis reactor.

[0021] The term "synthesis gas" refers to a gas containing primarily hydrogen and carbon monoxide, and may also contain small amounts of carbon dioxide, methane, water, nitrogen and tars.

[0022] The term "hydrocarbon" includes straight or branched chain compounds of the alkane or alkene type having from 5 to 50 carbon atoms.

[0023] The term "alcohol" relates to linear or branched monoalcohols having 1 to 5 carbon atoms.

[0024] Another aspect of the invention is a system for carrying out the first method of the invention, for co-producing hydrogen and hydrocarbons or alcohols, said system comprising at least: Pyrolysis unit, Cracking unit, Refining unit, Syngas conversion unit, Hydrogen separation unit, a hydrocarbon or alcohol synthesis unit, and Hydrocarbon or alcohol fractionation and / or purification units.

[0025] Finally, the present invention relates to a system for the production of hydrogen, comprising at least: Pyrolysis unit, Cracking unit, Refining unit, Syngas conversion unit, A hydrogen separation unit, and A unit for recovering residual heat from exhaust gases.

[0026] The cracking unit in both systems comprises a cracking reactor and a cooling unit for the resulting raw synthesis gas.

[0027] Description of the drawings In order to supplement the description which follows and to better understand the characteristics of the invention, according to preferred examples of its practical embodiments, a set of drawings is attached as an integral part of the above description, in which are represented the following figures, which are of an illustrative and non-limiting nature: FIG. 1 shows a scheme of one embodiment of the present invention referring to the co-production of hydrogen with hydrocarbons or alcohols.

[0028] FIG. 2 shows a schematic diagram of one embodiment of the present invention referring to the production of hydrogen.

[0029] [Preferred embodiment of the present invention] As shown in a first aspect of the present invention, the present invention relates to a method for valorizing a waste material for co-production of hydrogen and a hydrocarbon or alcohol, the method comprising the steps of: a) subjecting the starting waste (1) to pyrolysis under external heating and a reducing atmosphere to obtain a pyrolysis product (2); b) optionally separating a solid fraction from said pyrolysis product; c) cracking the product obtained in the pyrolysis step a) or the product obtained in step b) after separation of the solid fraction in the presence of oxygen (3) and a first vapor stream (19.1) to obtain a raw synthesis gas (4); d) cooling the raw synthesis gas (4) obtained in c); e) purifying the raw synthesis gas (4) obtained in d) to obtain a purified synthesis gas (5); f) converting a mixture (6) of the first preheated fraction (5.1) of said gas obtained in e) with a second vapor stream (19.2) in the presence of a catalyst to obtain a hydrogen-enriched synthesis gas (7); g) separating hydrogen from the first fraction (7.1) of the hydrogen-rich synthesis gas to obtain hydrogen (8) and a tail gas (9) from the separation of said hydrogen; h) synthesizing a product (11) selected from a hydrocarbon or an alcohol from a preheated mixture (10) of the second fraction (5.2) of the gas obtained in e) and the second fraction (7.2) of the hydrogen-enriched synthesis gas obtained in f); i) fractionating and / or purifying the product obtained in h) to obtain different streams of hydrocarbons or alcohols (12), a process water stream and a tail gas stream (13) from the process; Steps f) to g) and h) to i) are parallel in time.

[0030] Preferably, the method of the invention integrates the heating and cooling energy needs of the different process streams so that the system can operate without the need for external thermal energy, e.g. fossil fuels. The indirect heating of said pyrolysis step a) makes it possible to obtain high quality pyrolysis gases (free from dilution by inert compounds) while allowing the gases generated for heating the pyrolyzers, the tail gases (16) and (17), to be used for heating the remaining process streams, maximizing their efficiency.

[0031] Thus, preferably, the above-mentioned method comprises a step of combusting a fuel stream selected from a portion of the tail gas (9) from step g) and / or a portion of said tail gas (13) from step i) together with a preheated air stream (15) to generate an exhaust gas stream (16) which gives off heat in said external heating of step a) and after said pyrolysis step, an exhaust gas stream (17) from the pyrolyzer outlet gives off heat to preheat at least streams and / or fractions selected from: a water stream (18) for generating the steam (19) required for steps c) and f), and an air stream (14) for obtaining said preheated air stream (15), and / or a first fraction (5.1) of said gas from step f), and / or said mixture from step h). In another possible embodiment, the process stream itself is not used to generate the energy necessary for pyrolysis, as detailed in the previous paragraph, but the tail gas stream (16) releases heat to preheat at least one stream and / or fraction selected from: a water stream (18) to generate the steam (19) necessary for steps c) and f), and / or an air stream (14) to obtain a preheated air stream (15), and / or a first fraction (5.1) of the gases from step f), and / or the mixture from step h). From the heat release step, a tail gas stream (29) from heat exchange is obtained.

[0032] Preferably, in step h) hydrocarbons are synthesised by a Fischer-Tropsch reaction and in step i) said hydrocarbons are fractionated into desired products, optionally naphtha, distillate and paraffinic wax streams.

[0033] Preferably, said cracking step c) is carried out in the presence of a catalyst.

[0034] Preferably, in step h), an alcohol is synthesized, more preferably methanol.

[0035] Preferably, some or all of the process water stream from step i) is recycled along with the feed water (18).

[0036] In one aspect of the invention, the different streams are integrated to produce hydrogen as the only product. In this embodiment, the waste to valorization process for hydrogen production comprises the following steps: a) subjecting the starting waste (1) to pyrolysis under external heating and a reducing atmosphere to obtain a pyrolysis product (2); b) optionally separating a solid fraction from said pyrolysis product; c) cracking the product obtained in the pyrolysis step a) or the product obtained in step b) after separation of the solid fraction in the presence of oxygen (3) and a first vapor stream (19.1) to obtain a raw synthesis gas (4); d) cooling the raw synthesis gas (4) obtained in c); e) purifying the raw synthesis gas (4) obtained in d) to obtain a purified synthesis gas (5); f) converting a mixture (6) of the first preheated fraction (5.1) of said gas obtained in e) with a second vapor stream (19.2) in the presence of a catalyst to obtain a hydrogen-enriched synthesis gas (7); g) separating the hydrogen-rich synthesis gas (7) to obtain hydrogen (8) and a tail gas (9) from the separation of the hydrogen; It further comprises the step of mixing and combusting a fuel stream selected from a portion of the tail gas (9) from step g) and / or a portion of the purified synthesis gas (5.2) with a preheated air stream (15); thereby generating an exhaust gas stream (16) which gives off heat in the external heating of step a) and after the pyrolysis step to at least one stream and / or fraction selected from: a water stream (18) for generating the steam (19) required for steps c) and f), and / or an air stream (14) for obtaining the preheated air stream (15), and / or said fraction (5.1) prior to step f).

[0037] In the process for the co-production of hydrogen with hydrocarbons or alcohols as well as in the process for producing hydrogen, the following preferred embodiments are conceivable.

[0038] Preferably, the starting waste (1) is selected from solid municipal waste, waste generated by commercial and industrial activities, and / or biomass, among other possible wastes.

[0039] The starting waste (1) is preferably treated prior to step a) to make it compatible with the requirements of the process. More preferably, the starting waste (1) is size-selected through a sieve and / or crushed and / or crushed and / or dried. In particular, the particle size of the starting waste should be less than 10 mm in its largest dimension.

[0040] Preferably, in step b) a solid fraction is separated from the pyrolysis products, which can be used as a fuel or can be used to recover metals present in this fraction.

[0041] The advantage of the present invention is that it stages the thermochemical processing of waste materials and optimizes the means for obtaining the temperatures required for the different conversion reactions, thus obtaining synthesis gas with minimal amounts of impurities and inerts in a system that minimizes the thermal requirements at high temperatures, thereby resulting in high efficiency.

[0042] Preferably, the pyrolysis step a) is carried out at a temperature range between 400°C and 650°C, and the cracking step c) is carried out at a temperature between 800°C and 1300°C to maximize the hydrogen and carbon monoxide content and minimize the tar content in the synthesis gas.

[0043] Preferably, the cooling step d) is carried out using the heat of the raw synthesis gas (4) to generate steam. Preferably, the temperature of the cooled raw synthesis gas is between 250°C and 350°C.

[0044] This raw synthesis gas (4) may contain different contaminants, both solid and gaseous. Preferably, said purification involves one or more steps selected from separation of solids, absorption into a liquid and / or adsorption onto a solid.

[0045] Another advantage of these two methods, hydrogen and hydrocarbon or alcohol co-production and hydrogen production, is that the water stream condensed in the process can be recovered and utilized in the same manner.

[0046] Thus, in a preferred embodiment, after the conversion step f), a portion of the unreacted steam is condensed from the hydrogen-rich gas (7) and a portion of the condensed water is recycled together with the feed water (18).

[0047] In another preferred embodiment, after the shifting step f), the hydrogen-enriched synthesis gas (7) is cooled by a stream of water which is subsequently heated to form steam (19.1) from the cracking step and / or steam (19.2) from the shifting step.

[0048] As has been described above, the system for carrying out the first method of the invention, i.e. for the co-production of hydrogen and hydrocarbons or alcohols, comprises at least: A pyrolysis unit (20), Cracking unit (21), A purification unit (23), A synthesis gas conversion unit (24); A hydrogen separation unit (25), A hydrocarbon or alcohol synthesis unit (26); and A unit (27) for fractionation and / or purification of hydrocarbons or alcohols.

[0049] Preferably, the system comprises an oxygen generation unit (22) for generating oxygen for the cracking step. Preferably, the pyrolysis unit comprises a pyrolyzer (20.1) and at least one burner (20.2) for generating the heat required for the pyrolysis. Furthermore, preferably, the system for implementing a waste recovery method for the production of hydrogen and hydrocarbons or alcohols comprises a section (28) for recovering residual heat from the exhaust gas. More preferably, the section (28) for recovering residual heat from the exhaust gas comprises a burner.

[0050] (Example 1. Hydrogen Production Example) The crushed municipal solid waste was fed through a hopper equipped with a bulk removal mesh, from which it was fed into the pyrolyzer, avoiding the ingress of air into the reactor. In the pyrolyzer, the waste was subjected to a temperature of 450°C under a reducing atmosphere and partially decomposed. The pyrolysis product was then fed into a cracking reactor, where it was thermally converted to synthesis gas at 1200°C in the presence of steam and oxygen. The raw synthesis gas was cooled to 330°C. The cooled raw synthesis gas was then sent to a purification unit consisting of an absorption unit and an adsorption unit to remove pollutants. A part of the purified synthesis gas was led to the burner for providing heat to the pyrolyzer, while the rest was preheated in a unit for recovering residual heat from the exhaust gas and mixed with steam before being fed to the synthesis gas conversion reactor. Here, CO reacts with steam to produce H2 and CO2 over a catalyst bed. The hydrogen-enriched synthesis gas was fed to a hydrogen separation unit by pressure swing adsorption (PSA), from which H2 and a tail gas stream were obtained, which were used to provide heat to the pyrolyzer.

[0051] In this way, 133 kg of hydrogen was obtained per ton of waste.

[0052] Example 2. Example of hydrogen and hydrocarbon co-production The steps of pyrolyzer feed, pyrolysis, thermal conversion, raw syngas cooling, and syngas purification were carried out as in Example 1. As in Example 1, a portion of the purified syngas was preheated in a unit for recovering residual heat from the exhaust gas and mixed with steam before being introduced into the syngas shift reactor to produce a hydrogen-enriched syngas. A portion of this stream was fed to a purification unit to obtain hydrogen.

[0053] A mixture of the second fraction of the purified synthesis gas and a portion of the hydrogen-enriched synthesis gas, preheated in the heat recovery unit, was conducted to a hydrocarbon synthesis unit, the products of which were separated into final product streams.

[0054] In this way, 144 kg of hydrogen and 64 kg of hydrocarbons were obtained per ton of waste.

[0055] Example 3. Example of co-production of hydrogen and methanol Example 3 was carried out in the same manner as Example 2, except that the mixture of the second fraction of the purified synthesis gas and a portion of the hydrogen-enriched synthesis gas was led to a methanol synthesis unit, and the product was purified to obtain the final product.

[0056] In this way, 148 kg of hydrogen and 121 kg of methanol were obtained per ton of waste.

[0057] The examples of the present invention show that, as shown in Example 3, more hydrogen can be obtained per ton of waste starting from the same amount and composition of waste when co-produced with a hydrocarbon or alcohol, namely methanol. [Brief description of the drawings]

[0058] [Figure 1] FIG. 1 shows a scheme of one embodiment of the present invention referring to the co-production of hydrogen with hydrocarbons or alcohols. [Diagram 2] FIG. 2 shows a schematic diagram of one embodiment of the present invention referring to the production of hydrogen.

Claims

1. It includes the following steps: a) subjecting the starting waste (1) to pyrolysis under external heating and a reducing atmosphere to obtain a pyrolysis product (2); b) optionally separating a solid fraction from said pyrolysis product; c) cracking the product obtained in the pyrolysis step a) or the product obtained in step b) after separation of the solid fraction in the presence of oxygen (3) and a first vapor stream (19.1) to obtain a raw synthesis gas (4); d) cooling the raw synthesis gas (4) obtained in c); e) purifying the raw synthesis gas (4) obtained in d) to obtain a purified synthesis gas (5); f) converting the mixture (6) of the first preheated fraction (5.1) of said gas obtained in e) with a second vapor stream (19.2) in the presence of a catalyst to obtain a hydrogen-enriched synthesis gas (7); g) separating hydrogen from the first fraction (7.1) of said hydrogen-rich synthesis gas to obtain hydrogen (8) and a tail gas (9) from said hydrogen separation; h) synthesizing a product (11) selected from a hydrocarbon or an alcohol from a preheated mixture (10) of the second fraction (5.2) of the gas obtained in e) and the second fraction (7.2) of the hydrogen-enriched synthesis gas obtained in f); i) fractionating and / or purifying the product obtained in h) to obtain different streams of hydrocarbons or alcohols (12), a process water stream and a tail gas stream (13) from the process; Steps f) to g) and h) to i) are parallel in time. A method for material valorization of waste for the co-production of hydrogen and hydrocarbons or alcohols.

2. 2. The method according to claim 1, characterized in that it comprises a step of combusting a fuel stream selected from a portion of the tail gas (9) from step g) and / or a portion of the tail gas (13) from step i) together with a preheated air stream (15) to generate an exhaust gas stream (16) which gives off heat in the external heating of step a) and which, after the pyrolysis step, gives off heat to at least one stream and / or fraction selected from a water stream (18) for generating the steam (19) required for steps c) and f) and / or an air stream (14) for obtaining the preheated air stream (15) and / or a first fraction (5.1) of the gases of step f) and / or the mixture of step h) in order to preheat them.

3. 2. A method according to claim 1, characterized by the step of mixing and burning a fuel stream selected from a portion of the tail gas (9) from step g) and / or a portion of the tail gas (13) from step i) with a preheated air stream (15) to generate an exhaust gas stream (16) which gives off heat to and preheats at least one stream and / or fraction selected from a water stream (18) for generating the steam (19) required for steps c) and f) and / or an air stream (14) for obtaining said preheated air stream (15) and / or the first gas fraction (5.1) of step f) and / or said mixture of step h).

4. 4. The method according to any one of claims 1 to 3, characterized in that after the conversion step f), the hydrogen-enriched synthesis gas (7) is cooled by a stream of water which is subsequently heated to form steam (19.1) for the cracking step and / or steam (19.2) for the conversion step.

5. 5. The method according to claim 1, characterized in that after the conversion step f), the unreacted vapour fraction of the hydrogen-rich gas (7) is condensed and a part of the condensed water is recycled together with the feed water (18).

6. 6. The method according to any one of claims 1 to 5, wherein part or all of the process water stream from step i) is recycled together with the feed water (18).

7. 7. The method according to any one of claims 1 to 6, characterized in that the pyrolysis step a) is carried out at a temperature range between 400°C and 650°C and the temperature of the cracking step c) is in the range between 800°C and 1300°C.

8. 8. The process according to claim 1, characterized in that in step c) the cracking is carried out in the presence of a catalyst.

9. 9. The method according to claim 1, wherein in step h) methanol is synthesized.

10. 10. The method according to any one of claims 1 to 9, characterized in that the purification step e) comprises at least one step selected from separation of a solid, absorption in a liquid and / or adsorption on a solid.

11. It includes the following steps: a) subjecting the starting waste (1) to pyrolysis under external heating and a reducing atmosphere to obtain a pyrolysis product (2); b) optionally separating a solid fraction from said pyrolysis product; c) cracking the product obtained in the pyrolysis step a) or the product obtained in step b) after separation of the solid fraction in the presence of oxygen (3) and a first vapor stream (19.1) to obtain a raw synthesis gas (4); d) cooling the raw synthesis gas (4) obtained in c); e) purifying the raw synthesis gas (4) obtained in d) to obtain a purified synthesis gas (5); f) converting the mixture (6) of the first preheated fraction (5.1) of said gas obtained in e) with a second vapor stream (19.2) in the presence of a catalyst to obtain a hydrogen-enriched synthesis gas (7); g) separating the hydrogen-rich synthesis gas (7) to obtain hydrogen (8) and a tail gas (9) from the separation of said hydrogen; It also comprises a step of mixing and combusting a fuel stream selected from a portion of the tail gas (9) from step g) and / or a portion of the purified synthesis gas (5.2) with a preheated air stream (15) to generate an exhaust gas stream (16) which gives off heat in the external heating of step a) and after the pyrolysis step gives off heat to at least one stream and / or fraction selected from a water stream (18) for producing the steam (19) required for steps c) and f) and / or an air stream (14) for obtaining the preheated air stream (15) and / or the fraction (5.1) prior to step f).

12. 12. The method according to claim 11, characterized in that the pyrolysis step a) is carried out at a temperature range between 400°C and 650°C and the temperature of the cracking step b) is in the range between 800°C and 1300°C.

13. 13. The method according to claim 11 or 12, characterized in that after the conversion step f), the hydrogen-enriched synthesis gas (7) is cooled by a stream of water which is subsequently heated to form steam (19.1) for the cracking step and / or water steam (19.2) for the conversion step.

14. 14. The method according to any one of claims 11 to 13, characterized in that after the conversion step f), the unreacted water vapor fraction of the hydrogen-enriched synthesis gas is condensed and the condensed water is recycled together with the feed water (18).

15. A system for implementing the method of claims 1 to 10, characterized in that it comprises at least: A pyrolysis unit (20), Cracking unit (21), A purification unit (23), A synthesis gas conversion unit (24), A hydrogen separation unit (25), A synthesis unit (26) for hydrocarbons or alcohols, and A unit (27) for fractionation and / or purification of hydrocarbons or alcohols, The cracking unit includes a cracking reactor and a unit for cooling the raw synthesis gas. system.

16. A system for implementing the method of claims 11 to 14, comprising at least: A pyrolysis unit (20), Cracking unit (21), A purification unit (23), A synthesis gas conversion unit (24), A hydrogen separation unit (25), and a section (28) for recovering residual heat from the exhaust gases, The cracking unit includes a cracking reactor and a unit for cooling the raw synthesis gas. system.

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