Waste appreciation process and system for co-production of hydrogen and hydrocarbons or alcohols

Abstract

The invention relates to the appreciation of waste material by thermochemical treatment in order to obtain high value added products, such as hydrogen and hydrocarbons or alcohols, and to a system for carrying out the appreciation of such waste material.

Description

Technical Field

[0001] The present invention relates to valorization of waste materials by thermochemical treatment to obtain high value-added products. Background Art

[0002] Currently, a large amount of waste generated by human activities is deposited in landfills. The socio-economic and environmental damage caused by this waste makes it necessary to develop waste valorization technologies to reduce the amount of waste that has no use.

[0003] The recycling pathway can be either energy recovery (i.e. obtaining electricity by incinerating the waste) or material recovery (i.e. converting the waste into different compounds such as hydrogen, hydrocarbons or alcohols).

[0004] An example of energy recovery is described in the patent with publication number EP2318157, in which a system and method for the pyrolysis treatment of municipal and household waste are proposed. The waste passes through a classification unit, a grinding unit, a drying unit and a collection unit in sequence and is sent to a pyrolysis reactor for pyrolysis treatment. The synthesis gas produced by pyrolysis undergoes a series of cleaning steps and is then used as the working medium of the power generation unit. As a result of the synthesis gas purification process, carbon dioxide is also obtained in the process. The purpose of this recovery is to obtain energy and carbon dioxide.

[0005] Patent publication number US10280377 describes a system comprising a pyrolysis chamber and a steam cracking unit to obtain synthesis gas for thermal and electrical co-production of energy and / or steam.

[0006] In the literature of the prior art, waste valorization includes both energy and matter. In the present invention, a process has been developed in which the valorization is only matter, producing hydrogen, hydrogen and hydrocarbons, or hydrogen and alcohols, with the highest efficiency relative to the products obtained. Summary of the invention

[0007] Due to growing concerns about the environment and increasingly stringent regulations, the efficient management of municipal, industrial and agricultural solid wastes is an issue of increasing importance.

[0008] The goal of valorization is to transform waste materials into high value-added products or into raw materials for other uses and processes, thus providing environmental and economic benefits by preventing their deposition in landfills.

[0009] The invention describes a method and system based on thermal treatment of waste materials, which produces different products with high added value (such as hydrogen, hydrocarbons or alcohols). In addition, the production of hydrogen is increased by integrating process streams and when hydrogen is co-produced with hydrocarbons or alcohols.

[0010] The method of the invention comprises a pyrolysis reaction, wherein the starting waste material is decomposed by external heating of a reactor under a reducing atmosphere. From the products obtained in the pyrolysis, the solid phase obtained can optionally be separated. After the pyrolysis, the method comprises a step of cracking the pyrolysis products, wherein they react 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 synthesis gas. A portion of this hydrogen-rich gas is treated to extract hydrogen as a product, while the remainder is mixed with a previously unused portion of the purified synthesis gas and reacted in the presence of a second catalyst to obtain a second product derived from the synthesis gas.

[0012] This method, in which hydrogen and a second product (hydrocarbon or alcohol) are co-produced, creates a synergistic effect in the process integration and allows better productivity compared to processes where hydrogen is produced as the only product. By this method, starting from the same amount of raw materials, in addition to a large amount of high-value-added second product, a greater amount of hydrogen is obtained through their co-production than when hydrogen is the only product.

[0013] Therefore, a first aspect of the present invention relates to a waste valorization process for the combined production of hydrogen and hydrocarbons or alcohols, the process comprising the following steps:

[0014] a) pyrolyzing the starting waste material by external heating under a reducing atmosphere to obtain a pyrolysis product;

[0015] b) optionally, separating a solid portion from the pyrolysis product;

[0016] c) cracking the product obtained in pyrolysis step a) or in step b) after separation of the solid fraction in the presence of oxygen and a first steam stream to obtain a crude synthesis gas;

[0017] d) cooling the raw synthesis gas obtained in c);

[0018] e) purifying the crude synthesis gas obtained in d) to obtain purified synthesis gas;

[0019] f) converting a mixture of the first preheated portion of the gas obtained in e) and the second steam stream into a hydrogen-rich synthesis gas in the presence of a catalyst;

[0020] g) separating hydrogen from the first portion of the hydrogen-rich synthesis gas to obtain hydrogen and obtaining a tail gas from the separation of the hydrogen;

[0021] h) synthesizing a product selected from hydrocarbons or alcohols from the preheated mixture of the second gas portion obtained in e) and the second portion of the hydrogen-rich synthesis gas obtained in f);

[0022] i) fractionating and / or purifying the product obtained in h) to obtain different hydrocarbon or alcohol streams, a process water stream and a process tail gas stream,

[0023] Therein, steps f) to g) and h) to i) are carried out in parallel in time.

[0024] The present invention also relates to a method for producing hydrogen, wherein different process streams are integrated to obtain hydrogen as the only product. The method comprises the same steps as steps a) to g) described in the previous paragraph. In order to increase the efficiency of hydrogen production, the external heating in step a) is carried out by burning a stream selected from a portion of the tail gas of step g) and / or a portion of the purified synthesis gas of step e) mixed with a preheated air stream, thereby producing a flue gas stream, which releases heat for the external heating of step a) and, after the pyrolysis step, releases heat to the following streams and / or parts: a water stream for producing the steam required for steps c) and / or f) and / or an air stream for obtaining a preheated air stream and / or a portion of the purified synthesis gas treated in step f). Therefore, the present invention relates to a waste value-added method for the production of hydrogen, which comprises the following steps:

[0025] a) pyrolyzing the starting waste material by external heating under a reducing atmosphere to obtain a pyrolysis product;

[0026] b) optionally, separating a solid portion from the pyrolysis product;

[0027] c) cracking the product obtained in the pyrolysis step a) or in step b) after separation of the solid fraction in the presence of oxygen and a first steam stream to obtain a crude synthesis gas;

[0028] d) cooling the raw synthesis gas obtained in c);

[0029] e) purifying the crude synthesis gas obtained in d) to obtain purified synthesis gas;

[0030] f) converting a mixture of the first preheated portion of the gas obtained in e) and the second steam stream into a hydrogen-rich synthesis gas in the presence of a catalyst;

[0031] g) separating the hydrogen-rich synthesis gas to obtain hydrogen and tail gas generated by hydrogen separation;

[0032] In addition, it also comprises a portion of the tail gas selected from step g) and / or step e)

[0033] a step of mixing a fuel stream of a portion of the purified synthesis gas in step a) with a preheated air stream and combusting them together, thereby producing a flue gas stream which releases heat for the external heating of step a), and after the pyrolysis step, to at least one stream and / or portion selected from the group consisting of:

[0034] A water stream for producing the steam required for steps c) and f) and / or an air stream for obtaining a preheated air stream and / or

[0035] Alternatively, the first part of the gas obtained in e) is preheated in f).

[0036] The term “material valorization” involves the use of waste materials to obtain material products that can be used in socio-economic activities.

[0037] The term "waste" in this specification relates to material discarded from other processes which can be chemically decomposed at least by heating to produce combustible gases. Examples of such waste include: solid municipal waste, waste from industrial activities or biomass waste.

[0038] The term "pyrolysis" relates to thermal decomposition under a reducing atmosphere.

[0039] The term "external heating" relates to indirect heating, ie heat is provided from the outside by electrical heating, external combustion or other means.

[0040] The term "cracking" in the context of the present invention relates to the thermochemical conversion of tar into molecules of lower molecular weight, optionally in the presence of a catalyst.

[0041] The term "tar" in the present invention relates to organic compounds with a molecular weight higher than methane from the pyrolysis reactor.

[0042] The term "synthesis gas" relates to a gas consisting essentially of hydrogen and carbon monoxide and possibly containing smaller amounts of carbon dioxide, methane, water, nitrogen and tars.

[0043] The term "hydrocarbon" includes linear or branched compounds of the alkane or alkene type having from 5 to 50 carbon atoms.

[0044] The term "alcohol" relates to straight-chain or branched monoalcohols having 1 to 5 carbon atoms.

[0045] Another aspect of the present invention is a system for implementing the first method of the present invention, a system for co-producing hydrogen and hydrocarbons or alcohols, comprising at least:

[0046] Pyrolysis unit,

[0047] Cracking unit,

[0048] Purification unit,

[0049] Synthesis gas conversion unit,

[0050] Hydrogen separation unit,

[0051] a hydrocarbon or alcohol synthesis unit, and

[0052] Unit for fractionating and / or purifying hydrocarbons or alcohols.

[0053] Finally, the present invention relates to a system for producing hydrogen, comprising at least:

[0054] Pyrolysis unit,

[0055] Cracking unit,

[0056] Purification unit,

[0057] Synthesis gas conversion unit,

[0058] a hydrogen separation unit, and

[0059] A unit for recovering waste heat from flue gases.

[0060] The cracking unit in both systems includes a cracking reactor for obtaining a raw synthesis gas and a cooling unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to supplement the ongoing description and to better understand the characteristics of the invention, a set of drawings is attached as an integral part of said description, according to a preferred example of a practical embodiment of the invention, in which the following are represented in an illustrative and non-limiting manner:

[0062] Figure 1 A schematic diagram showing an embodiment of the invention relating to the combined production of hydrogen and hydrocarbons or alcohols is shown.

[0063] Figure 2 A schematic diagram showing an embodiment of the present invention relating to hydrogen production is shown. DETAILED DESCRIPTION

[0064] As described in the first aspect of the present invention, the present invention relates to a waste material valorization method for the combined production of hydrogen and hydrocarbons or alcohols, the method comprising the following steps:

[0065] a) pyrolyzing the starting waste material (1) by external heating under a reducing atmosphere to obtain a pyrolysis product (2);

[0066] b) optionally, separating a solid portion from the pyrolysis product;

[0067] c) cracking the product obtained in the pyrolysis step a) or in step b) after separation of the solid fraction in the presence of oxygen (3) and a first steam stream (19.1) to obtain a crude synthesis gas (4);

[0068] d) cooling the raw synthesis gas (4) obtained in c);

[0069] e) purifying the crude synthesis gas (4) obtained in d) to obtain a purified synthesis gas (5);

[0070] f) converting a mixture (6) of the first preheated part (5.1) of the gas obtained in e) and a second steam stream (19.2) into a hydrogen-rich synthesis gas (7) in the presence of a catalyst;

[0071] g) separating hydrogen from the first part (7.1) of the hydrogen-rich synthesis gas to obtain hydrogen (8) and obtaining tail gas (9) from the separation of the hydrogen;

[0072] h) synthesizing a product (11) selected from hydrocarbons or alcohols from a preheated mixture (10) of the second part (5.2) of the gas obtained in e) and the second preheated part (7.2) of the hydrogen-rich synthesis gas obtained in f);

[0073] i) fractionating and / or purifying the product obtained in h) to obtain different hydrocarbon or alcohol streams (12), a process water stream and an off-gas stream from the process (13),

[0074] Therein, steps f) to g) and h) to i) are carried out in parallel in time.

[0075] Preferably, the process of the invention integrates the energy requirements of heating and cooling of the different process streams, so that the system can be operated without the need for external thermal energy (e.g. fossil fuels). The indirect heating of the pyrolysis step a) allows obtaining high quality pyrolysis gases (without dilution with inert compounds), while the gases produced for heating the pyrolyzer (flue gases (16) and flue gases (17)) can be used to heat the remaining process streams, maximizing their efficiency.

[0076] Therefore, preferably, the above method has a step of burning a fuel stream selected from a portion of the tail gas (9) of step g) and / or a portion of the tail gas (13) of step i) together with the preheated air stream (15), thereby producing a flue gas stream (16), the flue gas stream (16) releases heat in the external heating of step a), and after the pyrolysis step, the flue gas stream (17) from the pyrolyzer outlet releases heat to at least one stream and / or part selected from the following: a water stream (18) for producing the steam (19) required for step c) and step f) and an air stream (14) for obtaining the preheated air stream (15) and / or the first part (5.1) of the gas from step f) and / or from step h) to preheat their mixture. In another possible embodiment, as mentioned above, the process streams themselves are not used to generate the energy required for the pyrolysis, and the flue gas stream (16) releases heat to at least one stream and / or part selected from the group consisting of: a water stream (18) for generating the steam (19) required for step c) and step f) and / or an air stream (14) for obtaining a preheated air stream (15) and / or a first part (5.1) of the gases from step f) and / or from step h) for preheating their mixture. The flue gas stream from the heat exchanger (29) is obtained from the release step.

[0077] Preferably, in step h), the hydrocarbons are synthesized by a Fischer-Tropsch reaction and in step i), the hydrocarbons are fractionated into desired product streams (optionally, naphtha, distillates and paraffins).

[0078] Preferably, the cracking step c) is carried out in the presence of a catalyst.

[0079] Preferably, an alcohol, more preferably methanol, is synthesized in step h).

[0080] Preferably, part or all of the process water stream from step i) is recycled with the feed water (18).

[0081] In one aspect of the invention, the different streams are integrated to produce hydrogen as the only product. In this embodiment, the waste valorization method for producing hydrogen comprises the following steps:

[0082] a) pyrolyzing the starting waste material (1) by external heating under a reducing atmosphere to obtain a pyrolysis product (2);

[0083] b) optionally, separating a solid portion from the pyrolysis product;

[0084] c) cracking the product obtained in the pyrolysis step a) or in step b) after separation of the solid fraction in the presence of oxygen (3) and a first steam stream (19.1) to obtain a crude synthesis gas (4);

[0085] d) cooling the raw synthesis gas (4) obtained in c);

[0086] e) purifying the crude synthesis gas (4) obtained in d) to obtain a purified synthesis gas (5);

[0087] f) converting a mixture (6) of the first preheated part (5.1) of the gas obtained in e) and a second steam stream (19.2) into a hydrogen-rich synthesis gas (7) in the presence of a catalyst;

[0088] g) separating the hydrogen-rich synthesis gas (7) to obtain hydrogen (8) and tail gas (9) produced by hydrogen separation;

[0089] It also includes the step of mixing a fuel stream selected from a portion of the tail gas (9) of step g) and / or a portion of the purified synthesis gas (5.2) with a preheated air stream (15) and burning them together, thereby producing a flue gas stream (16), wherein the flue gas stream (16) releases heat during the external heating of step a) and, after the pyrolysis step, releases heat to at least one stream and / or portion selected from the following: a water stream (18) for producing steam (19) required for steps c) and f) and / or an air stream (14) for obtaining the preheated air stream (15) and / or the portion (5.1) before step f).

[0090] In both the process for the combined production of hydrogen and hydrocarbons or alcohols and the process for the production of hydrogen, the following preferred embodiments are contemplated.

[0091] Preferably, the starting waste material (1) is selected from: solid municipal waste, waste from commercial and industrial activities and / or biomass, and possibly other waste materials.

[0092] Preferably, the starting waste material (1) is treated before step a) to adapt it to the needs of the method. More preferably, the starting waste material (1) is size-selected by passing through a sieve and / or crushed and / or pressed and / or dried. In particular, the maximum particle size of the starting waste material should be less than 10 mm.

[0093] Preferably, in step b), a solid fraction is separated from the pyrolysis product. This product can be used as a fuel or for the recovery of metals present in this fraction.

[0094] One advantage of the invention is that the separation is carried out in the step of thermochemical treatment of the wastes while optimizing the means of obtaining the temperatures required for the different conversion reactions. In this way, a synthesis gas with a minimum content of impurities and inerts is obtained in a system that minimizes the heat demand at high temperatures, thereby increasing efficiency.

[0095] Preferably, the pyrolysis step a) is carried out at a temperature in the range of 400°C to 650°C and the cracking step c) is carried out at a temperature between 800°C and 1300°C to maximize the content of hydrogen and carbon monoxide in the synthesis gas and minimize the content of tar.

[0096] Preferably, the cooling step d) is performed using the heat of the raw synthesis gas (4) to produce steam. Preferably, the temperature of the cooled raw synthesis gas is between 250°C and 350°C.

[0097] This raw synthesis gas (4) may contain various solid and gaseous contaminants and preferably requires purification by one or more of the following steps: solid separation, liquid absorption and / or solid adsorption.

[0098] Another advantage of both processes is that the water stream condensed in the process is recovered and used in the same way, whether it is the co-production of hydrogen and hydrocarbons or alcohols or the hydrogen production process.

[0099] Therefore, in a preferred embodiment, after the conversion step f), the unreacted steam fraction is condensed from the hydrogen-rich gas (7), and part of the condensed water is recycled together with the feed water (18).

[0100] In another preferred embodiment, after the conversion step f), the hydrogen-rich synthesis gas (7) is cooled by a water stream which is subsequently heated to form steam from the cracking step (19.1) and / or steam from the conversion step (19.2).

[0101] As mentioned above, the system for implementing the first method of the present invention, i.e., the system for co-producing hydrogen and hydrocarbons or alcohols, comprises at least:

[0102] a pyrolysis unit (20),

[0103] Cracking unit (21),

[0104] a purification unit (23),

[0105] Synthesis gas conversion unit (24),

[0106] A hydrogen separation unit (25),

[0107] a hydrocarbon or alcohol synthesis unit (26), and

[0108] Unit (27) for fractionating and / or purifying hydrocarbons or alcohols.

[0109] 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.

[0110] Furthermore, preferably, the system for implementing the waste recovery method for the production of hydrogen and hydrocarbons or alcohols comprises means for recovering waste heat from the flue gas (28). More preferably, the means for recovering waste heat from the flue gas (28) comprises a burner.

[0111] Example 1. Hydrogen production example

[0112] The shredded municipal solid waste is fed into the pyrolyzer from its feed position through a hopper with a bulk material rejection screen to avoid air from entering the reactor. In the pyrolyzer, the waste is subjected to a temperature of 450°C in a reducing atmosphere to partially decompose it. The pyrolysis products then enter the cracking reactor and are thermally converted into synthesis gas at 1200°C in the presence of steam and oxygen. The raw synthesis gas is cooled to 330°C. The cooled raw synthesis gas is then sent to a purification unit consisting of an absorption unit and an adsorption unit to remove pollutants. A portion of the purified synthesis gas is directed to the burner to supply heat to the pyrolysis furnace, while the rest is preheated in a unit for recovering waste heat from flue gases and mixed with steam before being sent to the synthesis gas conversion reactor, where CO reacts with steam on a catalytic bed to produce H2 and CO2. The hydrogen-rich synthesis gas is sent to a hydrogen separation unit by pressure swing adsorption (PSA), from which H2 and a tail gas stream for supplying heat to the pyrolyzer are obtained.

[0113] In this method, 133 kg of hydrogen can be obtained per ton of waste.

[0114] Example 2. Example of co-production of hydrogen and hydrocarbons

[0115] The steps of pyrolyzer feeding, pyrolysis, thermal conversion, cooling of the raw syngas and purification of the syngas are carried out in the same manner as in Example 1. As shown in Example 1, a portion of the purified syngas is preheated in a unit for recovering waste heat from flue gases and mixed with steam before being introduced into the syngas conversion reactor, thereby producing a hydrogen-rich syngas. A portion of this stream is sent to a purification unit, in which hydrogen is obtained.

[0116] A mixture of the second portion of the purified synthesis gas preheated in the heat recovery unit and a portion of the hydrogen-rich synthesis gas is introduced into a hydrocarbon synthesis unit, the products of which are separated into final product streams.

[0117] In this process, 144 kg of hydrogen and 64 kg of hydrocarbons are obtained per ton of waste.

[0118] Example 3. Example of combined production of hydrogen and methanol

[0119] Example 3 is carried out in the same manner as Example 2, except that a mixture of the second portion of the purified synthesis gas and a portion of the hydrogen-rich synthesis gas is introduced into a methanol synthesis unit, and the product thereof is purified to obtain a final product.

[0120] In this process, 148 kg of hydrogen and 121 kg of methanol can be obtained per ton of waste.

[0121] The examples of the present invention show that starting from the same amount and composition of waste, more hydrogen can be obtained per ton of waste when co-produced with hydrocarbons or alcohols, methanol, as shown in Example 3.

Claims

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

2. The method according to claim 1, characterized in that The method comprises the step of burning a fuel stream selected from a portion of the tail gas (9) of step g) and / or a portion of the tail gas (13) of step i) together with a preheated air stream (15), thereby producing a flue gas stream (16), said flue gas stream (16) releasing heat in the external heating of step a) and, after the pyrolysis step, releasing heat to at least one stream and / or portion 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 first gas portion (5.1) from step f) and / or a preheated mixture thereof from step h).

3. The method according to claim 1, characterized in that A step of burning a fuel stream selected from a portion of the tail gas (9) of step g) and / or a portion of the tail gas (13) of step i) mixed with a preheated air stream (15) to produce a flue gas stream (16), said flue gas stream releasing heat to at least one stream and / or part selected from the following streams: a water stream (18) for producing the steam (19) required for step c) and step f) and / or an air stream (14) for obtaining said preheated air stream (15) and / or the first gas portion (5.1) from step f) and / or a preheated mixture thereof from step h).

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

5. The method according to any one of claims 1 to 4, characterized in that After said conversion step f), the unreacted steam portion of the hydrogen-rich gas (7) is condensed and part of the condensed water is recycled together with the feed water (18).

6. The method according to any one of claims 1 to 5, characterized in that A portion or all of the process water stream from step i) is recycled with the feed water (18).

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 ranging from 400°C to 650°C, and the temperature of the cracking step c) is ranging from 800°C to 1300°C.

8. The method according to any one of claims 1 to 7, characterized in that In step c), the cracking is carried out in the presence of a catalyst.

9. The method according to any one of claims 1 to 8, characterized in that In step h) methanol is synthesized.

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 the following steps: solid separation, liquid absorption and / or solid adsorption.

11. A waste material value-added method for producing hydrogen, comprising the following steps: a) pyrolyzing the starting waste material (1) by external heating under a reducing atmosphere to obtain a pyrolysis product (2); b) optionally, separating a solid portion from the pyrolysis product; c) cracking the product obtained in the pyrolysis step a) or in step b) after separation of the solid fraction in the presence of oxygen (3) and a first steam stream (19.1) to obtain a crude synthesis gas (4); d) cooling the raw synthesis gas (4) obtained in c); e) purifying the crude synthesis gas (4) obtained in d) to obtain a purified synthesis gas (5); f) converting a mixture (6) of the first preheated part (5.1) of the gas obtained in e) and a second steam stream (19.2) into a hydrogen-rich synthesis gas (7) in the presence of a catalyst; g) separating the hydrogen-rich synthesis gas (7) to obtain hydrogen (8) and tail gas (9) produced by hydrogen separation; It also includes the step of mixing a fuel stream selected from a portion of the tail gas (9) of step g) and / or a portion of the purified synthesis gas (5.2) with a preheated air stream (15) and burning them together to produce a flue gas stream (16), wherein the flue gas stream (16) releases heat during the external heating of step a) and, after the pyrolysis step, releases heat to at least one stream and / or portion selected from the following: a water stream (18) for producing steam (19) required for steps c) and f) and / or an air stream (14) for obtaining the preheated air stream (15) and / or a portion (5.1) before step f).

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

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

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

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

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

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