Combustion of off-gas from electrolysis processes using enriched air.

Abstract

A chemical plant is provided in which an electrolysis section is configured to receive at least a portion of a first steam feed and electrolyze it to provide a hydrogen stream and an oxygen-enriched stream. A first heat exchanger is configured to receive at least a portion of the oxygen-enriched stream and a combustion air stream and to transfer heat from the oxygen-enriched stream to the combustion air stream. At least a portion of the heated combustion air stream and off-gas stream are configured to be combusted in at least one burner to provide a combustion gas stream. A first heat exchanger is configured to receive at least a portion of the combustion gas stream and the water stream. The first heat exchanger is configured to transfer heat from at least a portion of the combustion gas stream to the water stream to provide a cooled combustion gas stream and a steam stream. A method for producing a steam stream using a combustible off-gas stream of a chemical plant is also provided.

Description

[Technical Field]

[0001] Technical Field The present invention relates to a chemical plant and method for producing a steam stream using a combustible off-gas stream. [Background technology]

[0002] background When chemical plants produce ammonia, methanol, etc., a purge of combustible gas is discharged from the synthesis loop (the "purge stream" or "off-gas stream"). In conventional natural gas plants, these purge streams are typically used as fuel for reformers or fired heaters.

[0003] In electrolysis-based chemical plants, where firing heaters may not be available, these purge streams are currently waste / export streams. It is desirable to utilize these purge streams in chemical plants, thereby increasing plant efficiency and utilizing what could otherwise be a waste stream. Summary of the Invention [Problem to be solved by the invention]

[0004] overview The present invention utilizes the heating value of the purge stream by combusting the stream in a duct burner with enriched air from the electrolysis process, thereby improving plant efficiency and utilizing a stream that would otherwise be treated as a waste stream. [Means for solving the problem]

[0005] Thus, in a first aspect, the present invention relates to a chemical plant, said plant comprising: - flammable off-gas streams, - electrolysis section, - a first steam feed; - at least one burner, - a first heat exchanger, - water flow, wherein the electrolysis section is configured to receive and electrolyze at least a portion of the first steam feed to provide a hydrogen stream and an oxygen-enriched stream; wherein at least a portion of the oxygen-enriched stream and at least a portion of the off-gas stream are arranged to be combusted in the at least one burner to provide a combustion gas stream; wherein the first heat exchanger is positioned to receive at least a portion of the combustion gas flow and the water flow, and the first heat exchanger is positioned to transfer heat from at least a portion of the combustion gas flow to the water flow to provide cooled combustion gas and steam flows; wherein the plant comprises a steam drum arranged to receive at least a portion of the steam stream from the first heat exchanger and to supply a portion of the steam stream to the electrolysis section as at least a portion of the first steam feed.

[0006] In another aspect, there is provided a method for producing a steam stream using a combustible off-gas stream in a chemical plant as described herein, said method comprising the steps of: - providing a plant as described herein; - feeding at least a first portion of the first steam feed to the electrolysis section and electrolyzing the first portion to provide a hydrogen stream and an oxygen-enriched stream; - supplying at least a portion of the oxygen-enriched stream and at least a portion of the off-gas stream to at least one burner to provide a combustion gas stream; - supplying at least a portion of the combustion gas stream and the water stream to the first heat exchanger to transfer heat from at least a portion of the combustion gas stream to the water stream to provide a cooled combustion gas stream and a cooled steam stream; and - feeding at least a portion of the steam stream from the first heat exchanger to the steam drum and feeding a portion of the steam stream to the electrolysis section as at least a portion of the first steam feed.

[0007] Further aspects of the present invention are set forth in the following description, figures and appended claims.

[0008] Legend This technique is illustrated by the following schematic diagram: [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 shows a simple layout of one embodiment of the system of the present invention. [Figure 2] FIG. 2 shows a more advanced layout of the system of the present invention. [Figure 3] FIG. 3 shows a layout of a further developed system of the present invention. [Figure 4] FIG. 4 shows a layout of a further developed system of the present invention. [Figure 5] FIG. 5 shows a layout of a further developed system of the present invention. [Figure 6] FIG. 6 shows a layout of a further developed system of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Detailed Disclosure Gas content percentages are by volume unless otherwise specified. All feeds are preheated as needed.

[0011] A "stage" consists of one or more "units" that perform a change in the chemical composition of the feed, and may also consist of elements such as heat exchangers, mixers, or compressors that do not change the chemical composition of the feed or stream.

[0012] The term "synthesis gas" (abbreviated as "syngas") means a gas that contains hydrogen, carbon monoxide, carbon dioxide, and small amounts of other gases, such as argon, nitrogen, methane, and steam.

[0013] In a first aspect, there is provided a chemical plant comprising: - flammable off-gas streams, - electrolysis section, - a first steam feed; - at least one burner, - a first heat exchanger, - Water flow, and - Steam drum.

[0014] Flammable Off-Gas Stream A flammable off-gas stream refers to an off-gas stream containing at least one flammable component, the off-gas stream being generated within the chemical plant, such as a purge gas stream or a waste gas stream from a refinery section. A typical flammable off-gas stream composition can include, for example, CO, CO2, H2, CH4, and inert gases (N2, Ar, etc.). Optionally, the off-gas stream can contain olefins or alkenes (C n H 2n ; n≧2). The specific composition of the combustible off-gas stream may vary depending on the production objectives of the chemical plant.

[0015] In one embodiment, the combustible off-gas stream comprises 15 to 70 mol%, e.g., 20 to 70 mol%, H2. In one embodiment, the combustible off-gas stream may comprise less than 25 mol% CO. In one embodiment, the combustible off-gas stream may comprise 0 to 25 mol%, e.g., 0.1 to 5 mol%, or 10 to 25 mol% CO. In one embodiment, the combustible off-gas stream may comprise less than 35 mol% CH4. In one embodiment, the combustible off-gas stream may comprise 0 to 35 mol%, e.g., 0.1 to 5 mol%, or 10 to 25 mol% CH4. In one embodiment, the combustible off-gas stream may comprise less than 20 mol% NH3. In one embodiment, the combustible off-gas stream may comprise 0 to 20 mol% NH3, e.g., 0.1 to 10 mol%. The combustible off-gas stream can contain one or more of these combustible components in any combination, so long as the total amount of these combustible components is less than or equal to 100% of the total combustible off-gas stream. Thus, the total amount of these combustible components can be 40-100 mol %, e.g., 50-90 mol %, or 50-80 mol % of the total combustible off-gas stream. Other components, such as CO2, argon, and / or N2, may also be present.

[0016] In one aspect, the chemical plant further comprises a synthesis gas stream and a synthesis section configured to receive and convert the synthesis gas stream into a product stream and an off-gas stream, the synthesis section configured to supply at least a portion of the off-gas stream to the burner.

[0017] In one embodiment, the synthesis section (also referred to as a synthesis loop) is configured to supply at least a portion of an off-gas stream to the burner, the off-gas stream being a purge gas stream. In this embodiment, the synthesis section partially converts the synthesis gas stream into a product stream and a recycle stream, the recycle stream receiving a second synthesis gas vapor (referred to as a makeup synthesis gas stream), and the recycle stream is then recycled to re-enter the synthesis section, such as a synthesis reactor. To control the content of by-products and inert gases that may accumulate with the recycle stream, at least a portion of the recycle stream is supplied as an off-gas stream to the burner, preferably before adding makeup synthesis gas. In this way, the off-gas stream can include unconverted synthesis gas, by-products produced in the synthesis section, and inert gases.

[0018] In one aspect, a chemical plant comprises a synthesis gas stream, a synthesis section, and a purification section, wherein the synthesis section is arranged to receive the synthesis gas stream and convert it into a product stream and an off-gas stream, the purification section is arranged to receive the product stream and convert it into a purified product stream and a further off-gas stream, and the purification section is arranged to supply at least a portion of the further off-gas stream to the burner.

[0019] In these embodiments, at least a portion of the off-gas stream configured to be combusted in the at least one burner can be provided from any of i) only one or more synthesis section(s), ii) only one or more purification section(s), or iii) a combination of off-gas streams from the synthesis section(s) and purification section(s), or iv) combined with one or more alternative streams. Thus, the specific composition will depend on conditions including: a) the composition of the provided feed, e.g., the synthesis gas stream; b) the type and combination of stages / sections / reactors, particularly the specifications of the synthesis section and therefore any applied catalyst; c) the location of any purification section, including units such as capture and / or separation sections, or CO2 capture units; and d) the process conditions applicable throughout the chemical plant, such as temperature and pressure.

[0020] In one embodiment, the chemical plant includes a synthesis gas stream. The synthesis gas stream may be a gas stream containing primarily hydrogen (H) and nitrogen (N). Alternatively, the synthesis gas stream may be a gas stream containing hydrogen, carbon monoxide, carbon dioxide, and small amounts of other gases, such as argon, nitrogen, methane, and steam. The synthesis gas stream may be provided as a feed to the synthesis section.

[0021] In one embodiment, the chemical plant comprises a synthesis section, wherein the synthesis section is an ammonia synthesis section, a methanol synthesis section, a methanol-to-olefins synthesis section, a methanol-to-gasoline (TIGAS) synthesis section, a methanation section, or a Fischer-Tropsch (FT) synthesis section.

[0022] In one embodiment, the chemical plant includes an ammonia synthesis section. In this embodiment, the chemical plant includes a synthesis gas stream containing primarily H2 and N2. An electrolysis section may provide the H2, or the H2 may be provided from a production plant where it is produced from natural gas or fossil fuels. An air fractionation unit may provide the N2. The ammonia synthesis section receives the synthesis gas and provides an off-gas stream that is provided to a burner.

[0023] In other embodiments, the chemical plant includes a methanol synthesis section, a methanol-to-olefin synthesis section, a methanol-to-gasoline (TIGAS) synthesis section, a methanation section, or a Fischer-Tropsch (FT) synthesis section. In such embodiments, the synthesis gas stream supplied to the synthesis can include H and CO. The H is supplied from an electrolysis section or from a chemical plant where H is produced from natural gas or fossil fuels. Typically, the CO is recovered from flue gas from the combustion of fossil fuels or non-fossil biomass. The synthesis section receives the synthesis gas and provides an off-gas stream that is supplied to the burner.

[0024] In embodiments where the chemical plant includes a refinery section, the refinery section may include a CO2 capture unit.

[0025] Electrolysis Section The electrolysis section is positioned to receive and electrolyze at least a portion of the first steam feed to provide a hydrogen stream and an oxygen-enriched stream.

[0026] A first steam feed is required as the feed for the electrolysis section. Preferably, the first steam feed is a high-purity dry steam feed. To obtain a high-purity steam feed, it is commonly known to subject the water stream to some form of water treatment before use in industrial systems (sometimes referred to as process steam). Untreated water contains impurities that can cause damage and wear to the system. Such impurities can lead to the formation of scale, corrosion, deposits, etc. Additionally, oxygen may be unnecessary for process steam, as it can cause corrosion of piping, heat exchangers, etc. Furthermore, due to the high concentration of impurities in boiler water, entrainment is not required.

[0027] One way to obtain a high-purity steam feed is to first treat raw water in an ion exchanger to remove minerals. The demineralized water is then passed through a deaerator, resulting in deaerated water, which is sent to a boiler equipped with a steam drum, where dry steam is produced for use as process steam. The deaerator removes oxygen from the water, which is collected in a surge vessel. In the boiler, the deaerated water is heated in a heat exchanger, and the heated water-steam mixture is separated in a steam drum to produce dry steam for use as feed.

[0028] The electrolysis section may consist of solid oxide electrolysis cell (SOEC) electrodes, such that the decomposition of HO occurs within the SOEC. Multiple cells can be combined into an SOEC stack, and multiple stacks can be combined into an SOEC plant. A solid oxide cell (SOEC) is an electrochemical conversion device with two compartments (anode and cathode) separated by an electrolyte material made of solid oxide or ceramic electrolyte. Such cells are fully reversible, for example, for the composition HO<->H.

[0029] The first steam feed enters the process side of the SOEC, where it is (partially) converted to a fuel stream, a hydrogen stream, and an oxygen-enriched stream. The oxygen produced in the fuel-side conversion travels through an electrochemical cell to the oxygen side of the SOEC, where it is recombined as gaseous oxygen. The oxygen is typically removed from the SOEC via a flashing stream.

[0030] In one embodiment, the plant includes a flushing stream configured to be supplied to the anode of the electrolysis section as a flushing stream for flushing oxygen, thereby providing an oxygen-enriched stream. In one embodiment, the flushing stream is air, a nitrogen-enriched stream, or a CO2-enriched stream.

[0031] In one embodiment, at least a portion of the hydrogen stream provided by the electrolysis section is arranged to be supplied as feed to the synthesis section, optionally in admixture with a synthesis gas stream.

[0032] burner At least a portion of the oxygen-enriched stream and at least a portion of the off-gas stream are arranged to be combusted in the at least one burner to provide a combustion gas stream. In one embodiment, the at least one burner is a duct burner arranged in an enriched air duct of the electrolysis section.

[0033] Off-gases with a high heating value can be combusted alone. Off-gases with a low heating value may therefore require additional supplemental fuel, which may be H2 and / or syngas. If necessary, an additional fuel stream, preferably a portion of the hydrogen stream or a portion of the syngas stream, can be arranged to feed at least one burner.

[0034] If the flushing stream is air, or if no stream is used, additional air is not required. If the flushing stream does not contain oxygen, additional oxygen may be required. In one embodiment, therefore, at least one burner is positioned to receive an additional oxygen-containing stream.

[0035] heat exchanger A first heat exchanger is positioned to receive at least a portion of the combustion gas flow and the water flow, and is positioned to transfer heat from at least a portion of the combustion gas flow to the water flow to provide cooled combustion gas and steam flows.

[0036] In one embodiment, at least a portion of said steam stream is fed to the electrolysis section as at least a portion of said first steam feed to the electrolysis section.

[0037] Steam drum and additional heat exchanger The plant includes a steam drum positioned to receive at least a portion of the steam stream from the first heat exchanger and to supply the portion of the steam stream to the electrolysis section as at least a portion of the first steam feed.

[0038] In one embodiment, the plant further comprises a second heat exchanger configured to heat a second water stream to produce a second steam stream and supply the second steam stream to the steam drum, thereby providing the remaining heat required to produce the steam stream.

[0039] In one embodiment, the steam drum is positioned to receive a first water stream, and the steam drum is positioned to supply the water stream to at least a first heat exchanger and / or supply the second water stream to a second heat exchanger.

[0040] In some embodiments, the second heat exchanger comprises multiple heat exchanger units. Typically, the multiple heat exchangers are arranged in parallel. In one embodiment, the second heat exchanger is heated by an electric heater, a steam-fired heater, heat recovery from a hot stream, and / or heat recovery using one or more heat pumps. Each heat exchanger unit can have multiple different heat sources, in sequence or in combination.

[0041] A steam drum is a standard feature of water-tube boilers. It is a water and steam reservoir located at the top end of the water tubes. The drum stores the steam generated in the water tubes and acts as a phase separator for the steam-water mixture.

[0042] Method for producing a steam stream In a second aspect, there is also provided a method for producing a steam stream using a combustible off-gas stream of a chemical plant, said method comprising the steps of: - providing a plant as described herein; - feeding at least a first portion of the first steam feed to the electrolysis section and electrolyzing the first portion to provide a hydrogen stream and an oxygen-enriched stream; - supplying at least a portion of the oxygen-enriched stream and at least a portion of the off-gas stream to at least one burner to provide a combustion gas stream; - supplying at least a portion of the combustion gas stream and the water stream to the first heat exchanger to transfer heat from at least a portion of the combustion gas stream to the water stream to provide a cooled combustion gas stream and a cooled steam stream; and the method further comprises the steps of supplying at least a portion of the steam stream from the first heat exchanger to the steam drum and supplying a portion of the steam stream to the electrolysis section as at least a portion of the first steam feed.

[0043] In one aspect, the method further comprises supplying at least a portion of the steam stream from the first heat exchanger to the electrolysis section as at least a portion of the first steam feed to the electrolysis section.

[0044] In one embodiment, the method further includes providing a first water stream to the steam drum to provide the water stream to at least a first heat exchanger.

[0045] In one aspect, the plant further comprises a second heat exchanger, and the method includes enabling heat transfer from the second heat exchanger to a second water stream provided from the steam drum to produce a second steam stream, and providing the second steam stream to the steam drum.

[0046] In one embodiment, the method further comprises supplying a flashing stream, such as air or a CO2-enriched stream, to the anode of the electrolysis section and flashing oxygen with the flashing stream to provide an oxygen-enriched stream. In a more particular embodiment, the flashing stream is oxygen-poor and the process further comprises supplying a separate oxygen-containing stream to at least one burner.

[0047] In one aspect, the chemical plant further comprises the synthesis gas stream and the synthesis section, and the method further comprises supplying synthesis gas to the synthesis section to provide a product stream and an off-gas stream, at least a portion of the off-gas stream being supplied as a feed to the burner.

[0048] In one aspect, the chemical plant further comprises a synthesis gas stream, a synthesis section, and a purification section, and the method includes supplying the synthesis gas to the synthesis section and providing a product stream and an off-gas stream, and supplying the product stream to the purification section and providing a purified product stream and an off-gas stream, wherein at least a portion of the off-gas stream provided from the purification section is provided as a feed to the burner.

[0049] In one embodiment, the method further comprises supplying at least a portion of the hydrogen stream, optionally mixed with a syngas stream, from the electrolysis section to the synthesis section. In another embodiment, the method further comprises supplying an additional fuel stream, preferably a portion of the hydrogen stream or a portion of the syngas stream, to at least one burner.

[0050] In one embodiment, the plant further comprises a synthesis section, and the method further comprises feeding at least a portion of the vapor stream to the synthesis section for use in a distillation process. The synthesis section may be a methanol synthesis section or other conventional synthesis section.

[0051] In a further aspect, the plant comprises the purification section including a CO2 capture unit, and the method comprises supplying at least a portion of the vapor stream to the purification section for regeneration of the CO2 capture unit.

[0052] Specific Embodiments In the chemical plant (100) shown in FIG. 1, an electrolysis section (20) receives at least a portion of a first steam feed (5) and electrolyzes it to provide a hydrogen stream (22) and an oxygen-enriched stream (21). The chemical plant (100) also provides a combustible off-gas stream (12). At least one burner (30) receives at least a portion of the oxygen-enriched stream (21) and at least a portion of the combustible off-gas stream (12), which can be combusted in the at least one burner (30) to provide a combustion gas stream (31). A first heat exchanger (40) receives at least a portion of the combustion gas stream (31) and a water stream (51) and enables heat transfer from at least a portion of the combustion gas stream (31) to the water stream (51). The first heat exchanger (40) thus provides a cooled combustion gas stream (42) and a steam stream (52). Optionally, the electrolysis section (20) receives a portion (52a) of said steam stream (52) in admixture with said first steam feed (5).

[0053] In one embodiment shown in FIG. 2, the chemical plant (100) is further developed. A first addition to the configuration described in the first specific embodiment includes the electrolysis section (20) receiving a flashing stream (6), the anode of the electrolysis section (20) receiving the flashing stream (6) for flashing oxygen, and the electrolysis section (20) thereby providing an oxygen-enriched stream (21). A second addition to the configuration described in the first specific embodiment includes the combustible off-gas stream (12) being supplied from a synthesis section (10), where the synthesis section (10) receives a synthesis gas stream (1) and supplies a product gas stream (11) and a combustible off-gas stream (12). A third addition to the configuration described in the first specific embodiment includes the chemical plant (100) further comprising a steam drum (50) and a second heat exchanger (60). In this embodiment, the second heat exchanger (60) receives and heats the first water stream (51b) to produce a second steam stream (52c). The steam drum (50) receives at least a portion (52b) of the steam stream (52) and at least a portion of the second steam stream (52c) to produce a steam stream (52). Optionally, the electrolysis section (20) receives a portion (52a) of the steam stream (52) in admixture with the first steam feed (5).

[0054] In one embodiment shown in FIG. 3, the chemical plant (100) is arranged such that the steam drum (50) receives a first water stream (51b) and supplies said water stream (51) to at least a first heat exchanger (40) and supplies said second water stream (51c) to a second heat exchanger (60).

[0055] In one embodiment shown in FIG. 4, the chemical plant (100) is further developed. A first addition to the configuration described in the specific embodiment includes that the chemical plant (100) further comprises a purification section (15). The purification section (15) receives a product stream (11) from the synthesis section (10) and converts it into a purified product stream (16) and an off-gas stream (12b). Thus, the at least one burner (30) can receive combustible off-gases (12, 12b) from the synthesis section (10), from the purification section (15), or from both the synthesis section (10) and the purification section (15), the latter optionally as a mixed stream. A second addition to the configuration described in the specific embodiment includes that at least a portion (22a) of the hydrogen stream (22) from the electrolysis section (20), optionally mixed with the synthesis gas stream (1), can be supplied to the synthesis section (10) as additional synthesis gas. A third addition to the configuration described in the specific embodiment above includes at least one burner (30) receiving a separate oxygen-containing stream (7), which may be preferred if the flashing stream (6) is oxygen-poor.

[0056] In one embodiment shown in Figure 5, at least one burner (30) receives an additional fuel stream (8), which is preferably a portion of the hydrogen stream (22b) from the electrolysis section (20) or a portion of the synthesis gas stream (1a).

[0057] In one embodiment shown in Figure 6, the chemical plant (100) includes a synthesis section (10) that receives at least a portion (52d) of the vapor stream (52) for use in a distillation process. Also shown in Figure 6, the chemical plant (100) includes a purification section (15) that includes a CO2 capture unit (15a) that receives at least a portion (52d) of the vapor stream (52) for regeneration of the CO2 capture unit (15a). [Example]

[0058] example The first example, shown in Figure 3, is a simulation of a method implemented in connection with ammonia synthesis. The duty (energy transfer) in heat exchanger (40) of oxygen-enriched stream (31) increases from 3.46 to 4.32 MW (25%) when burner 30 is added to the system and stream 12 is fed to burner 30. The power required to generate the steam needed for process (52a) in electrolysis section (20) is reduced from 3.3 MW to 2.4 MW (part of 60), which corresponds to 26.5%.

[0059] Used range: Offgas [NH3] [mol%] Range Typical Examples N2: 15-60 23 H2: 20-70 66 CH4:0-25 0 Ar: 5-15 10 NH3:0-2 1 Other:<1 <1

[0060] The second example, shown in Figure 3, is a simulation of a process implemented in connection with methanol synthesis. The duty (energy transfer) in the heat exchanger (40) of the oxygen-enriched stream (31) increases from 1.8 MW to 2.3 MW (27.7%). The power required to generate the steam needed for the process (52a) in the electrolysis section (20) is reduced from 7.0 MW to 6.5 MW (part of 60), which corresponds to 7.3%.

[0061] Offgas (MeOH) [mol %] Range Typical Examples H2: 40-60 50 CO2: 35-55 45 CO: 0-2 1 CH4: 0-5 2 MeOH:0-6 3 Other: 0-5 <1 Conclusion: Utilizing waste streams can reduce the electricity consumption of chemical plants.

[0062] The third example, shown in Figure 3, is a simulation of a process implemented in connection with a Fischer-Tropsch synthesis. The duty (energy transfer) in the heat exchanger (40) for the oxygen-enriched stream (31) increases from 1.96 MW to 2.62 MW (33.2%). The power required to generate the steam needed for the process (52a) in the electrolysis section (20) is reduced from 7.0 MW to 6.35 MW (part of 60), which corresponds to 9.3%.

[0063] Offgas (FT) [mol%] Range Typical Examples H2 15-25 17 CO2 20-50 33 CO 10-25 15 CH4 10-35 32 N2 0-5 1 C2+ XX-XX 0-5 2 Conclusion: Utilizing waste streams can reduce the electricity consumption of chemical plants.

[0064] While the present invention has been described with reference to numerous embodiments and aspects, the overall scope of the invention is defined in the appended claims. Those skilled in the art can combine embodiments and aspects as needed within the scope of the invention. All documents mentioned herein are incorporated by reference.

Claims

1. A chemical plant (100), said plant (100) comprising: - flammable off-gas stream (12) - electrolysis section (20) - first steam feed (5) - at least one burner (30) - a first heat exchanger (40) - Water flow (51) the electrolysis section (20) is arranged to receive at least a portion of the first steam feed (5) and electrolyze it to provide a hydrogen stream (22) and an oxygen-enriched stream (21); at least a portion of said oxygen-enriched stream (21) and at least a portion of said off-gas stream (12) are arranged to be combusted in said at least one burner (30) to provide a combustion gas stream (31); the first heat exchanger (40) is arranged to receive at least a portion of the combustion gas flow (31) and the water flow (51), and the first heat exchanger (40) is arranged to transfer heat from at least a portion of the combustion gas flow (31) to the water flow (51) to provide a cooled combustion gas flow (42) and a steam flow (52); The plant comprises a steam drum (50) arranged to receive at least a portion of the steam stream (52b) from the first heat exchanger (40) and to provide a portion of the steam stream (52a) to the electrolysis section (20) as at least a portion of the first steam feed (5).

2. 2. The chemical plant of claim 1, wherein the plant comprises a second heat exchanger (60) arranged to heat a second water stream (51 c) to produce a second steam stream (52 ​​c) and to supply the second steam stream (52 ​​c) to the steam drum (50).

3. 3. The chemical plant according to claim 1, wherein the steam drum (50) is arranged to receive a first water flow (51b), and the steam drum (50) is arranged to provide the water flow (51) to at least a first heat exchanger (40) and / or to provide the second water flow (51c) to a second heat exchanger (60).

4. The chemical plant of claim 3, wherein the second heat exchanger (60) comprises a plurality of heat exchanger units.

5. 5. The chemical plant of claim 3 or 4, wherein the second heat exchanger (60) is heated by an electric heater, a steam-fired heater, heat recovery from a high temperature stream, and / or heat recovery using one or more heat pumps.

6. 6. A chemical plant according to any one of claims 1 to 5, wherein the plant comprises a flushing stream (6) arranged to be supplied to the anode of the electrolysis section (20) as a flushing stream for flushing oxygen, thereby providing an oxygen-enriched stream (21).

7. The flushing stream (6) may be air, a nitrogen-enriched stream or a CO ２ 7. The chemical plant of claim 6, wherein the enriched stream is

8. Chemical plant according to any one of the preceding claims, wherein at least one burner (30) is arranged to receive an additional oxygen-containing stream (7).

9. 9. The chemical plant of claim 1, further comprising a synthesis gas stream (1) and a synthesis section (10), the synthesis section (10) being arranged to receive the synthesis gas stream (1) and convert it into a product stream (11) and an off-gas stream (12), and the synthesis section (10) being arranged to provide at least a portion of the off-gas stream (12) to the burner (30).

10. 10. The chemical plant according to any one of claims 1 to 9, comprising a synthesis gas stream (1), a synthesis section (10), and a purification section (15), wherein the synthesis section (10) is arranged to receive the synthesis gas stream (1) and convert it into a product stream (11) and an off-gas stream (12), and wherein the purification section (15) is arranged to receive the product stream (11) and convert it into a purified product stream (16) and a further off-gas stream (12b), and wherein the purification section (15) is arranged to provide at least a portion of the further off-gas stream (12b) to the burner (30).

11. 11. The chemical plant according to claim 9, wherein the synthesis section is an ammonia synthesis section, a methanol synthesis section, a methanol-to-olefin synthesis section, a methanol-to-gasoline (TIGAS) synthesis section, a methanation section or a Fischer-Tropsch (FT) synthesis section.

12. The chemical plant according to any one of claims 1 to 11, wherein the at least one burner (30) is a duct burner arranged in an enrichment air duct of the electrolysis section (20).

13. 13. A chemical plant according to any one of claims 9 to 12, arranged so that at least a portion of the hydrogen stream (22a) provided by the electrolysis section (20) is supplied as feed to the synthesis section (10), optionally in admixture with the synthesis gas stream (1).

14. 14. A chemical plant according to any one of the preceding claims, arranged to provide an additional fuel stream (8), preferably part of the hydrogen stream (22b) or part of the synthesis gas stream (1a), to at least one burner (30).

15. A method for producing a steam stream (52) using a combustible off-gas stream (12) in a chemical plant (100) according to any one of claims 1 to 14, comprising: The method comprises the following steps: - providing a plant according to any one of claims 1 to 14; - feeding at least a first portion of said first steam feed (5) to said electrolysis section (20) and electrolyzing said first portion to provide a hydrogen stream (22) and an oxygen-enriched stream (21); - feeding at least a portion of said oxygen-enriched stream (21) and at least a portion of said off-gas stream (12) to at least one burner (30) to provide a combustion gas stream (31); - feeding at least a portion of said combustion gas stream (31) and said water stream (51) to said first heat exchanger (40) for heat transfer from at least a portion of said combustion gas stream (31) to said water stream (51) to provide a cooled combustion gas stream (42) and steam stream (52); and - feeding at least a portion of said steam stream (52b) from said first heat exchanger (40) to said steam drum (50) and providing a portion of said steam stream (52a) as at least a portion of said first steam feed (5) to said electrolysis section (20).

16. 16. The method of claim 15, wherein the method includes supplying a first water flow (51b) to the steam drum (50) to provide the water flow (51) for at least the first heat exchanger (40).

17. 17. The method according to claim 15, wherein the plant comprises a second heat exchanger (60), and the method comprises enabling heat transfer from the second heat exchanger (60) to a second water stream (51c) provided from the steam drum (50) to generate a second steam stream (52c), and supplying the second steam stream (52c) to the steam drum (50).

18. The method further comprises the step of: ２ 18. The method of any one of claims 15 to 17, comprising supplying an enriched stream to the anode of the electrolysis section (20) and flashing oxygen with the flashing stream (6) to provide an oxygen-enriched stream (21).

19. 19. The method of claim 18, wherein the flashing stream (6) is oxygen-depleted, the method further comprising supplying a separate oxygen-containing stream (7) to at least one burner (30).

20. 20. The method of any one of claims 15 to 19, wherein the chemical plant comprises the synthesis gas stream (1) and the synthesis section (10), the method comprising feeding a synthesis gas (1) to the synthesis section (10) to provide a product stream (11) and an off-gas stream (12), and at least a portion of the off-gas stream is supplied as feed to the burner (30).

21. 21. The method of any one of claims 15 to 20, wherein the chemical plant comprises a synthesis gas stream (1), a synthesis section (10) and a purification section (15), the method comprising: supplying the synthesis gas (1) to the synthesis section (10) to provide a product stream (11) and an off-gas stream (12); and supplying the product stream (11) to the purification section (15) to provide a purified product stream (16) and an off-gas stream (12b), wherein at least a portion of the off-gas stream (12b) provided from the purification section (15) is supplied as feed to the burner (30).

22. The off-gas stream is 15 to 70 mole % hydrogen (H ２ ), less than 25 mole percent carbon monoxide (CO) and less than 35 mole percent methane (CH ４ 22. The method according to any one of claims 15 to 21, comprising:

23. 23. The method according to any one of claims 20 to 22, wherein the method comprises feeding at least a portion of the hydrogen stream (22a) from the electrolysis section (20) to the synthesis section (10), optionally in admixture with a synthesis gas stream (1).

24. 24. The method according to any one of claims 20 to 23, wherein the method comprises supplying an additional fuel stream (8), preferably part of the hydrogen stream (22b) or part of the synthesis gas stream (1 a), to at least one burner (30).

25. 25. The method of any one of claims 20 to 24, wherein the plant comprises a synthesis section (10), and the method comprises feeding at least a portion (52d) of the vapor stream (52) to the synthesis section (10) for use in a distillation process.

26. The plant is ２ The purification section (15) comprises a recovery unit (15a), and the method comprises feeding at least a portion (52d) of the vapor stream (52) to the purification section (15), ２ A method according to any one of claims 20 to 25, comprising regenerating the recovery unit (15a).

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