RU2780578C2 - Method for production of hydrogen-containing synthesis gas - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: inventions relate to the production of hydrogen-containing synthesis gas. A method for the production of hydrogen-containing synthesis gas is described, including the production of hydrogen-containing synthesis gas by conversion of hydrocarbon raw materials and heat supply from the combustion of several technological fuel streams, which include at least one fuel stream of ammonia, the combustion of which is carried out without the use of a catalyst in at least one device with fire heating. A method is described for upgrading a plant for ammonia synthesis from hydrocarbon raw materials, including a head section containing a reforming section for conversion of hydrocarbon raw materials into crude synthesis gas containing hydrogen, CO, and CO₂, and a purification section producing purified synthesis gas containing hydrogen and nitrogen in the required molar ratio of 3:1, and a synthesis section for conversion of purified synthesis gas into an ammonia product, wherein, when implementing the method, a part of the ammonia product is separated, and this part of the ammonia product is recirculated into the head section for using ammonia as fuel in at least one device with fire heating, which is part of the plant, in which ammonia fuel is burned without using a catalyst to implement the above-described method. A method for starting of a chemical plant for ammonia synthesis is described, including non-catalytic combustion of ammonia in at least one device with fire heating, which is part of the plant, during starting of the plant for the implementation of the above-described methods.

EFFECT: reduction in CO₂ emissions into the atmosphere.

20 cl, 2 dwg, 1 tbl, 1 ex

Description

Technical field

The present invention relates to a process for producing hydrogen-containing synthesis gas from a hydrocarbon feedstock. In particular, the invention relates to a process for producing hydrogen-containing synthesis gas, characterized by low emissions of CO ₂ into the atmosphere.

State of the art

To obtain hydrogen-containing synthesis gas from hydrocarbon feedstocks, a combined reforming process is usually used, in which the primary reformer reactor (reformer) is supplied with desulfurized hydrocarbons and steam, and the secondary reformer is supplied with gas from the primary reformer, partially reformed, and a stream of a suitable oxidizer (for example, air or oxygen). To obtain hydrogen-containing synthesis gas from hydrocarbon feedstocks, autothermal reforming (ATR) in a suitable reformer can also be used, with preheating in a furnace of the material supplied for processing, i.e., gaseous hydrocarbon feedstock.

The reformed (converted) gas is then typically passed through successive processing steps to produce a gaseous product, such as hydrogen or synthesis gas, the composition of which is suitable for the production of ammonia (i.e., containing H ₂ and N ₂ in the desired ratio of about 3:1), or to obtain methanol (ie, containing oxides of carbon and hydrogen with a stoichiometric number SN≥2, where SN=(H ₂ -CO ₂ )/(CO+CO ₂ )).

To obtain hydrogen-containing synthesis gas requires the combustion of at least the first amount of fuel to release the heat of reforming; a second amount of fuel is also typically consumed to generate steam and operate steam turbines that drive machinery such as pumps and compressors.

For this purpose, a portion of the hydrocarbon feedstock is usually used as fuel. This, however, is accompanied by significant emissions of CO ₂ into the atmosphere. One of the main sources of CO ₂ emissions is flue gas from the primary reformer and other fired furnaces, when used, such as booster heaters.

To protect the environment, CO ₂ emissions from the flue gas must be reduced.

Existing methods for reducing CO ₂ emissions include flue gas cleaning processes that capture CO ₂ from the flue gas, such as by washing with suitable solvents (eg Mitsubishi's KS-1™ solvent). These solvents, however, are expensive and the associated installations are expensive and energy intensive.

CO ₂ emissions also create problems during the start-up period of a chemical plant, which can last days or weeks and be accompanied by significant CO ₂ emissions.

Known methods for extracting CO ₂ from flue gases include absorption in a solvent (eg amine); temperature swing adsorption (TSA), pressure swing adsorption (PSA), vacuum swing adsorption (VSA) and separation on membranes. These methods require heat input, for example for regeneration in a TSA system, and/or mechanical energy input, for example for compressing the feed gas in a PSA system, or for vacuum removal of CO ₂ in a VSA system. During normal operation, this input of heat or mechanical energy can be recovered in the system, for example from waste heat. However, during start-up, there is no recovery of heat or mechanical energy because the plant is not yet in operation. Generation of the required heat by an additional device, such as a fuel-fired auxiliary steam generator, would be accompanied by emissions of carbon dioxide. Getting from an external source, for example, getting electricity from the grid, is usually too expensive.

Accordingly, the task of reducing CO ₂ emissions during the start-up of a chemical plant, in particular an ammonia synthesis plant, still remains unresolved. Generally speaking, the same problem can occur in transient mode when there is no internal heat and/or mechanical energy recovery needed for the CO ₂ removal system.

US 2011/0206594 describes the state of the art of a system and method for producing synthesis gas.

US 4,728,506 describes a start-up process for an ammonia plant that uses ammonia as a start-up medium by introducing ammonia into a reformer to form a start-up synthesis gas containing ammonia, and heating and recirculating this gas until the plant is brought up to operating temperature. . However, this does not solve the problem of CO ₂ emissions from the fired device during the start-up phase.

US 4,668,494 discloses a method of using solar energy in a chemical synthesis process, in which, as a heat source, catalytic oxidation of ammonia in an ammonia heater without fire supply of heat can be used, in which ammonia is oxidized on a catalytic grid to form nitrogen oxides for the subsequent synthesis of nitric acid.

Disclosure of invention

The objective of the present invention is to provide a method for producing hydrogen-containing synthesis gas from hydrocarbon feedstock, in which CO ₂ emissions into the atmosphere are significantly reduced compared to the prior art. Another object of the invention is to reduce CO ₂ emissions in transient conditions, in particular during plant start-up.

This problem is solved by the method in accordance with paragraph 1 of the claims.

The method according to the invention has a heat gain (heat input) provided by the combustion of several process fuel streams, and is characterized in that at least one of them is an ammonia fuel stream, and in that the combustion of this at least one ammonia fuel stream is carried out without the use of a catalyst in at least one device (equipment) with fire heating.

The combustion of said at least one ammonia fuel stream is carried out without the use of a catalyst (ie, in the absence of any catalyst to promote the oxidation of ammonia). The term "device/equipment with fire heating" means that combustion is carried out with the formation of a flame.

Non-catalytic flame combustion of ammonia converts ammonia into molecular nitrogen N ₂ and water, with minor amounts of nitrogen oxides. Accordingly, the combustion products consist predominantly of N ₂ and water. Typically, the nitrogen oxides produced in the described non-catalytic combustion of ammonia are less than 1000 ppmv (parts per million of flue gas) and preferably less than 100 ppmv.

Since burning ammonia produces N ₂ and H ₂ O, no CO ₂ is released into the atmosphere when the ammonia fuel stream is burned.

The ammonia fuel stream is also referred to as ammonia fuel.

At least one fire heating device is, for example, a flame heater. This at least one fired apparatus may be, for example, a reforming section, a partial oxidation section, or a purification section.

Non-catalytic combustion of ammonia can be carried out in conventional gas burners not specifically designed for combustion of ammonia.

The at least one ammonia fuel stream is preferably substantially pure ammonia. In some embodiments, the at least one ammonia fuel stream preferably contains at least 90% ammonia, more preferably at least 95%.

The combustion of the ammonia fuel stream can be carried out directly or after mixing with another gas. In some embodiments, the ammonia fuel stream, or multiple ammonia fuel streams, are mixed with another gas prior to combustion to form a blended fuel. This other gas may be, for example, hydrogen. Some embodiments may, for example, include mixing an ammonia stream with a hydrogen stream to produce a fuel stream comprising ammonia and hydrogen in a suitable ratio, such as 50% each.

Preferably, the hydrocarbon feed is natural gas. References hereinafter to natural gas are non-limiting.

The conversion of the gaseous hydrocarbon feed may include the reforming or partial oxidation of natural gas to converted gas or partially oxidized gas, respectively. Preferably, this conversion of the hydrocarbon feedstock includes a reforming step comprising at least one of: fired primary reforming, gas heated reforming (GHR), fired secondary reforming in an air or oxygen atmosphere, and autothermal reforming (ATR).

The reforming step is carried out in a reforming section. According to various embodiments, the reformer section includes at least one of a primary fired steam reformer and a gas heated (GHR) reformer and, in some cases (optionally), a secondary reformer supplied with air, oxygen or enriched air . According to other embodiments, the reforming section includes an autothermal reformer (ATR). In any of the embodiments mentioned above, a pre-reformer reactor may also be included. In addition, a preheater may be installed to preheat the pre-reformer or autothermal reformer feed.

Heat input may include process heat, such as from a primary reformer or process feed preheater heat, and/or heat to generate steam to drive steam turbines for compressors, pumps, etc.

Accordingly, the input heat is supplied to at least one of the following devices/equipment: a fired primary reformer, a hydrocarbon-steam mixture charge heater, an auxiliary steam generator, a desulfurization heater, a superheater, a heat recovery steam generator (HRSG). generator), the cooling exhaust of a gas turbine, a gas turbine (to generate power or to drive machinery such as a compressor). These fuel-burning devices are referred to as "fired heaters".

Combustion of at least one ammonia fuel stream preferably generates up to 50% of the total heat input to the process, preferably up to 30%, more preferably up to 15%. These percentages can be expressed as the product of flow rate (kg/s or mol/s) and calorific value (J/kg or J/mol).

Preferably, at least one ammonia fuel stream is supplied in the form of a gas stream or a vapor stream to the one or more combusted combustion heaters. This has the advantage of being able to use gas burners; in addition, combustion of gaseous or vapor fuels provides higher flame temperatures than combustion of liquid fuels.

Preferably, the at least one ammonia fuel stream is preheated before being fed to the combustion heater(s). The advantage of this method is that additional heat can be obtained during combustion. In addition, preheated ammonia can be supplied as a gas to the combustion heater(s) at a pressure of more than 1 atm.

In a preferred embodiment, the at least one ammonia fuel stream is vaporized prior to being fed to the combustion heater(s). In another preferred embodiment, the ammonia is evaporated by cooling another stream, during which frigoria (cold units corresponding to calories) are taken from the ammonia. For example, ammonia evaporates, cooling the compressor suction stage flow, thereby reducing the energy consumption of the compressor itself.

According to a preferred embodiment, the above-mentioned multiple process fuel streams comprise a low carbon, hydrogen rich fuel stream in addition to at least one ammonia fuel stream.

Combustion of the hydrogen-rich stream preferably produces at least 50% of the total heat input to the process, preferably at least 70%, more preferably at least 85%. These percentages can be expressed as the product of flow rate (kg/s or mol/s) and calorific value (J/kg or J/mol).

Ammonia can be stored at minus 33°C in a refrigerated tank at atmospheric pressure, or at low pressure and ambient temperature (for example, 15 bar at 30°C), having a high volumetric energy density of about 3 Gcal/m ³ calculated as the product of mass density and net calorific value (NTC).

According to a preferred embodiment, these multiple process fuel streams include at least one ammonia fuel stream derived from a storage tank. If the process involves the production of ammonia, part of the commercial ammonia can be stored in the tank as fuel according to the invention. According to a preferred embodiment, the ammonia fuel stream from the ammonia reservoir is fed as a control fuel to the flame heaters mentioned above.

The term "regulating fuel" refers to fuel supplied specifically for the rapid control of heat generation, allowing the fired heaters to be quickly controlled and operate at maximum efficiency. Preferably, the control fuel accounts for no more than 15%, more preferably no more than 10%, of the total heat of combustion in the process. Control fuel can be supplied via a separate fuel line.

The advantage of supplying control fuel from a storage tank is that this fuel is independent of the process. This is particularly desirable during transient operation, such as during start-up, as it allows fast fuel delivery.

The control ammonia fuel supplied from the storage tank may be all of the fuel used in the process, or only a portion of it.

The advantage of supplying ammonia control fuel is due to the ability to control the fire load of combustion heaters without emitting CO ₂ to the atmosphere, regardless of the process. This is critical, especially during transients such as start-ups, to ensure that carbon emissions are virtually eliminated without adversely affecting plant performance. For example, during operation of the plant, the flow rate of the control fuel can be controlled by increasing or decreasing it to compensate for changes in the flow rate of the hydrogen-rich fuel stream.

According to a preferred embodiment, the combustion of the control fuel provides the full heat input required for the transient, for example when starting up the plant.

Part of the ammonia from the control fuel is preferably decomposed or split into its constituents, namely nitrogen (N ₂ ) and hydrogen (H ₂ ), according to the following reaction:

2 NH ₃ ↔ N ₂ + 3 H ₂ .

This has the additional benefit of simplifying the combustion of the start-up fuel stream, since hydrogen (H ₂ ) is superior in combustion kinetics to ammonia and acts as a combustion activator for ammonia. The Applicant has found that hydrogen assists in the combustion of the ammonia fuel stream and provides better flame stability.

The decomposition reaction is endothermic and equilibrium limited, and requires high temperatures to achieve a conversion of over 50%. Preferably, the portion of the ammonia fuel stream that has undergone decomposition reaction does not exceed 50% of the total stream, more preferably not more than 30%. As a result, a small amount of energy is required to decompose such a portion of the ammonia at low temperatures. Electricity can be used to carry out the ammonia decomposition reaction.

Ammonia has a storage advantage over other fuels such as hydrogen. Storing a hydrogen-rich stream for use as a control fuel is impractical because hydrogen liquefies at a very low temperature (approximately minus 253°C) and liquefaction requires high energy costs. Storing hydrogen in a compressed form is also impractical due to the high pressure required to obtain a high energy density. At a pressure of 200 bar, gaseous hydrogen has a specific energy content of only 0.4 Gcal/m ³ .

In a particular embodiment of the invention, the conversion of the hydrocarbon feed produces a crude gaseous product containing hydrogen, CO and CO ₂ and this crude product is subjected to purification by removal of CO ₂ to obtain, as a result, depleted in CO ₂ synthesis gas. Preferably, the removal of CO ₂ is carried out after a shift reaction in which carbon monoxide (CO) is converted to carbon dioxide. Preferably, the aforementioned hydrogen-rich fuel stream contains or consists of said part of the CO ₂ depleted synthesis gas, the remainder of this CO ₂ depleted gas being directed to a particular use, for example, for ammonia synthesis.

The use of at least one ammonia fuel stream together with a hydrogen rich fuel stream has the following advantages: reduced ammonia consumption and reduced overall energy consumption while maintaining low CO ₂ emissions to the atmosphere. Another advantage is the simplification of combustion of the ammonia fuel stream; this is due to the fact that the kinetics of hydrogen combustion corresponds to a higher combustion rate, the combustion of hydrogen acts as an activator of the combustion of ammonia, the combustion kinetics of which corresponds to a lower combustion rate.

A preferred application of the present invention includes an ammonia production process. In accordance with the present invention, the hydrogen-containing synthesis gas contains hydrogen (H ₂ ) and nitrogen (N ₂ ) in a molar ratio of about 3:1, which react in the presence of a catalyst in a high pressure synthesis loop to produce an ammonia product.

Preferably, a portion of the ammonia produced is returned to the process as an ammonia fuel stream. More preferably, the other ammonia fuel stream is supplied as a control fuel from the storage tank. The advantage of using this regulating fuel is the ease of controlling the fire load, without interfering with the production process.

The ammonia product is obtained as a liquid under high pressure of about 100-200 bar. Separating said at least one ammonia fuel stream from the ammonia product has several advantages. First, liquid ammonia can be heated by reclaimed waste heat from the process; accordingly, more heat can be released during combustion. In addition, the at least one ammonia fuel stream may be expanded in the mechanism to combustion pressure, with energy recovery.

In addition to the ammonia product, a purge gas is obtained in the synthesis loop, which is further processed in a special unit to extract the hydrogen it contains. This hydrogen recovery unit generates a hydrogen-rich gas stream and tail gas. In some embodiments, these multiple process fuel streams may also include any of: at least a portion of the tail gas; at least a portion of the hydrogen-rich gas; at least a portion of the purge gas before extracting hydrogen therefrom. These streams may be added to at least one ammonia fuel stream. In some embodiments, the additional fuel stream also contains a portion of the previously mentioned CO ₂ depleted gas.

Another application of the invention includes a process for the production of methanol. According to the present invention, synthesis gas, which is a mixture of oxides of carbon and hydrogen, is subjected to a catalytic reaction in the synthesis loop to produce methanol.

A purge stream containing unreacted synthesis gas is also continuously removed from the methanol synthesis loop. In accordance with some embodiments of the invention, hydrogen can be recovered from this purge stream in a suitable hydrogen recovery unit (HRU) to produce hydrogen-rich gas and tail gas. The purge stream, as well as the hydrogen-rich gas and/or tail gas from the HRU, may form one or more fuel streams in some embodiments.

Preferably, said series of process fuel streams also includes a hydrogen-rich fuel stream that contains or consists of a portion of the purge stream. Preferably, at least a portion of the purge stream is previously subjected to the removal of at least a portion of the carbonaceous compounds. These carbonaceous compounds may include CO ₂ and compounds that form CO ₂ when burned, eg CO, CH ₄ , methanol.

According to a preferred embodiment, at least one ammonia fuel stream is co-produced with methanol so as to avoid drawing in an ammonia fuel stream from outside.

Another application of the invention includes a process for producing hydrogen. Preferably, at least one ammonia fuel stream is co-produced with hydrogen.

However, combustion of ammonia produces NOx (eg NO, NO ₂ ), which are known pollutants whose emissions are regulated by strict regulations. The vented gas may require very low NOx limits, such as a maximum of 100 parts per million (ppm) or even less.

The process according to the invention preferably comprises the step of reducing the concentration using selective catalytic reduction (SCR) to reduce NOx emissions. Preferably, the SCR comprises catalytic NOx reduction using an ammonia stream as a reducing agent. Preferably, this ammonia stream is separated from at least one ammonia fuel stream. Thus, there is no need to separately develop or use ammonia as a reducing agent.

In another aspect of the present invention, a method is provided for upgrading (refurbishing) an ammonia synthesis plant, in accordance with the attached formula. In the process according to the invention, part of the ammonia produced is used for combustion in at least one fired device (eg primary reformer) of the plant.

The ammonia fuel may be sent directly to at least one fired apparatus, or more preferably may be stored in a suitable ammonia fuel tank. The retrofit method may thus include the installation of such an ammonia fuel tank.

The ammonia plant can be upgraded to increase its capacity so that the additional capacity produces the required ammonia fuel, i.e., ammonia for use as fuel in at least one fired device.

Another feature of the invention includes the use of at least one ammonia fuel stream during the transient or startup phase. The term "transient mode" means a state in which the operating parameters deviate from the parameters of standard operating conditions and, therefore, internal energy recovery for input into the carbon reduction system (for example, recovered heat for the TSA emission reduction system) is temporarily not available.

Ammonia fuel for use in the transition phase or start-up phase may be stored in a suitable tank.

In this aspect of the invention, a method for starting up a chemical plant is provided, comprising using ammonia as a fuel for at least one fired device included in the plant, during the start-up phase of this plant.

This start-up method may be applicable to an ammonia synthesis plant or other chemical plant such as a methanol synthesis plant. In the case of an ammonia synthesis plant, the ammonia fuel burned during start-up may be part of the ammonia produced within the plant. The ammonia fuel is preferably stored in a dedicated ammonia fuel tank.

In all embodiments, the ammonia fuel is burned to form a flame without the use of a catalyst.

The advantages of the invention will be more fully presented by considering the following description of the preferred embodiments, which are not of a restrictive nature.

Brief description of the drawings

Below the invention is discussed in more detail with reference to the accompanying drawings, in which:

figure 1 shows the first embodiment of the invention;

figure 2 shows the second embodiment of the invention.

Detailed description of the invention

Figure 1 shows a block diagram of the plant 100 for the synthesis of ammonia, containing mainly section 1 reforming section 2 cleaning, multi-stage compressor 3, section 4 synthesis and node 5 extraction of hydrogen. Reforming section 1 and refining section 2 are part of head section 6.

The natural gas stream 10 is fed to a reformer 1 where it is converted in the presence of stream 11 and an oxidant 12 (e.g. air or enriched air) to form crude synthesis gas 13, mainly composed of hydrogen and containing small amounts of other components, including, for example, carbon monoxide, carbon dioxide, water, methane.

Raw synthesis gas 13 is fed to purification section 2 where carbon monoxide is converted to carbon dioxide to produce a shift gas that undergoes a carbon dioxide removal reaction to produce a purified gas 14 containing predominantly hydrogen and a tail gas stream 15 containing CO ₂ . For example, a carbon dioxide removal process is a pressure swing adsorption (PSA) process using molecular sieves.

If necessary, the purified gas 14 is mixed with nitrogen 16 from the air separation section (not shown) to produce ammonia make-up gas 17. The make-up gas 17 is further compressed in a multi-stage compressor 3 to the pressure of the synthesis section 4.

The gas 17 thus obtained, together with the hydrogen stream 18 regenerated from the hydrogen extraction unit 5, is fed into the synthesis section 4. The synthesis section produces ammonia 19 and a purge gas stream 20 which is processed in block 5 to regenerate its hydrogen content.

The ammonia 19 is separated into a first part 21 and a second part 22. The first part is used, together with the tail gas 23 exiting the hydrogen recovery unit 5, as fuel for one or more furnaces of the reformer section 1, for example in the burners of the primary reformer and/or in heater (not shown) of the material supplied for processing. The second part 22 is withdrawn from the plant. In some cases, the required small amount of natural gas 24 can also be used as fuel in the reformer section 1, however, to reduce CO ₂ emissions, it is desirable not to use this option.

Figure 2 shows a block diagram of the installation 100, in accordance with another embodiment of the invention. In this example, the purified gas portion 14a, predominantly containing hydrogen, is mixed with the tail gas 23 of the hydrogen recovery unit 5, and thus used as fuel in the reforming section 1.

Example

Table 1 below refers to the ammonia production process carried out in the head section and the synthesis section. Inside the head section, natural gas is converted to synthesis gas and CO ₂ is separated from the synthesis gas. The synthesis section produces salable ammonia and a purge stream, which is regenerated for use as fuel in the head section. The head section requires additional fuel from other sources, as shown in the examples below.

Table 1 compares total natural gas consumption, fuel consumption patterns, and ammonia production rates for the following processes where:

1.1 The need for fuel is mainly met by natural gas (state of the art);

1.2 The need for fuel is mainly satisfied by ammonia obtained in the ammonia production process (an embodiment according to figure 1 of the invention);

1.3 The fuel demand is mainly met by ammonia and low CO ₂ synthesis gas, which are obtained from the ammonia production process (an embodiment according to figure 2 of the invention).

In the methods in accordance with the embodiments of the invention (namely, 1.2 and 1.3), the use of natural gas as a fuel is excluded. Accordingly, flue gas emissions from the combustion of fuel in the form of natural gas are excluded.

All processes 1.1, 1.2 and 1.3 have the same ammonia output of 83 t/h. However, in the processes according to the invention (methods 1.2 and 1.3) an excess of ammonia is produced for use as a fuel. In particular, process 1.2 produces about 32% more ammonia than process 1.1, and process 1.3 produces 12% more ammonia than process 1.1.

The consumption of natural gas in the processes according to the invention (1.2 and 1.3) surprisingly turned out to be only marginally higher than in the prior art, despite the low flue gas emissions and the increased productivity of ammonia production. In particular, process 1.2 has GHG consumption more by 11%, and process 1.3 by 7%.

The use of ammonia fuel in combination with the CO ₂ depleted synthesis gas according to process 1.3 proves to be preferable, both in terms of total gas consumption and in terms of total ammonia production requirement. Accordingly, method 1.3 consumes less gas and requires a smaller (ie, less material intensive) plant than method 1.2.

Claims (23)

1. A method for producing hydrogen-containing synthesis gas, including obtaining hydrogen-containing synthesis gas by converting hydrocarbon feedstock (10) and supplying heat from the combustion of several process fuel streams (21, 23, 24), characterized in that these several process fuel streams (21, 23, 24) comprise at least one ammonia fuel stream (21) which is combusted without the use of a catalyst in at least one combustion device (1). 2. Process according to claim 1, wherein up to 50% of the total process heat input is generated by burning at least one ammonia fuel stream (21), preferably up to 30%, more preferably up to 15%. 3. Method according to claim 1 or 2, wherein said at least one ammonia fuel stream (21) is in a gaseous or vaporous state. 4. A method according to any one of the preceding claims, wherein said plurality of process fuel streams (21, 23, 24) comprise at least one ammonia fuel stream (21) supplied from a storage tank as a process control fuel that provides at most 15% of the total process heat from combustion, preferably not more than 10%. 5. A process according to any one of the preceding claims, wherein said plurality of fuel streams (21, 23, 24) also comprise a hydrogen-rich fuel stream (14a). 6. Process according to claim 5, wherein combustion of the hydrogen-rich fuel stream (14a) produces at least 50% of the total process heat input, preferably at least 70%, more preferably at least 85%. 7. The method according to claim 5 or 6, in which the conversion of the hydrocarbon feedstock (10) produces a crude gaseous product (13) containing hydrogen, CO and CO ₂ , which is subjected to purification by at least separation of CO ₂ , optionally after shift reaction that converts CO to CO ₂ , thereby producing CO ₂ depleted synthesis gas (14), wherein the hydrogen-rich fuel stream (14a) contains a portion of this CO ₂ depleted synthesis gas (14) or consists of her. 8. Process according to any one of the preceding claims, wherein the hydrogen-containing synthesis gas contains hydrogen (H ₂ ) and nitrogen (N ₂ ) and undergoes a catalytic reaction in the synthesis loop (4) to produce ammonia (19), wherein said several process fuel streams (21, 23, 24) contain part (21) of the ammonia thus obtained (19). 9. The method according to claim 8, in which said several process fuel streams (21, 23, 24) additionally include at least one ammonia fuel stream (21) supplied from a storage tank, which is preferably filled with ammonia (19) synthesized when implementing the method. 10. The method according to claim 8 or 9, in which the synthesis loop (4) also releases a purge stream (20) containing unreacted synthesis gas, and these several process fuel streams (21, 23, 24) include at least one of : purge stream or part thereof; a hydrogen-rich gas obtained after the removal of hydrogen from the purge stream; tail gas (23) obtained after the extraction of hydrogen from the purge stream (20). 11. The method according to any one of paragraphs. 1-6, in which the hydrogen-containing synthesis gas is a mixture of hydrogen and carbon oxides, and this synthesis gas is subjected to a catalytic reaction in the synthesis loop to produce methanol. 12. The method of claim. 11, in which the synthesis loop also produces a purge stream containing unreacted synthesis gas, and these several process fuel streams also include a hydrogen-rich fuel stream containing at least a portion of the specified purge stream or consisting of it, and preferably, at least a portion of the carbonaceous compounds are removed from at least a portion of the purge stream. 13. The method according to any one of paragraphs. 1-7, which is a method for producing hydrogen. 14. The method according to any of the preceding paragraphs, in which the conversion of hydrocarbon feedstock (10) includes a reforming stage (1) or partial oxidation, and the reforming stage (1) includes at least one of the following: primary reforming with fire heating; reforming with gas heating; secondary reforming with fire heating in an atmosphere of air or oxygen; autothermal reforming. 15. The method according to any of the preceding paragraphs, in which at least one device with fire heating, which burns ammonia fuel, includes at least one of the following: primary reformer; raw material heater; auxiliary steam generator; desulfurization heater; superheater; steam generator-recuperator; gas turbine. 16. A process according to any one of the preceding claims, wherein a portion of said at least one ammonia fuel stream is decomposed into nitrogen (N ₂ ) and hydrogen (H ₂ ), the resulting hydrogen acting as a combustion activator for burning the ammonia. 17. The method of claim 16, wherein the fraction decomposed into nitrogen and hydrogen does not exceed 50% of the total ammonia fuel stream, preferably not more than 30%. 18. A method according to any one of the preceding claims, comprising using said at least one ammonia fuel stream (21) in at least one fired device during a transient or start-up phase. 19. A method for upgrading the plant for the synthesis of ammonia from hydrocarbons, including: a head section containing a reforming section for converting hydrocarbon feedstock into crude synthesis gas containing hydrogen, CO and CO ₂ , and a purification section producing purified synthesis gas containing hydrogen and nitrogen in the required molar ratio of 3:1, and synthesis section for converting purified synthesis gas into an ammonia product, moreover, during the implementation of the method, a part of the ammonia product is separated and this part of the ammonia product is recycled to the head section for using ammonia as a fuel in at least one device with fire heating, which is part of the plant, in which ammonia fuel is burned without using a catalyst for implementing the method according to any one of paragraphs. 1-18. 20. A method for starting up a chemical plant for the synthesis of ammonia, including non-catalytic combustion of ammonia in at least one device with fire heating, which is part of the plant, during the start-up of the plant for implementing the method according to any one of paragraphs. 1-18.

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