Water treatment system for producing oxygen-deficient and dry steam and process for producing steam

Abstract

The present invention relates to an improved water treatment system and a water treatment process for producing oxygen-deficient and dry process steam suitable for high temperature solid oxide electrolysis. Compared with systems and processes of the prior art, the system and the process are simplified.

Description

Technical Field

[0001] The present invention relates to an improved water treatment system and water treatment process for producing oxygen-depleted and dry process steam suitable for high temperature solid oxide electrolysis. Background Art

[0002] Climate change has accelerated the global shift from fossil fuels to renewable energy. Typically, renewable energy comes from wind and solar power generation. The challenge with renewable energy is its intermittent nature.

[0003] Power-to-X (PtX) is a term used to describe pathways that use electrical energy for power conversion, energy storage and reconversion. Power-to-X conversion technologies allow electricity to be decoupled from the electricity sector for use in other sectors (e.g. transport or chemicals) and can eliminate the problems associated with fluctuations in renewable energy generation.

[0004] Currently, electrolysis is the core technology for PtX solutions, where X is usually hydrogen, syngas, chemicals or synthetic fuels. When electrolysis is combined with renewable electricity, the production of fuels and chemicals can no longer rely on fossil resources.

[0005] Solid oxide electrolysis (SOE) technology is particularly attractive because it has higher conversion efficiencies than low-temperature electrolysis - due to the thermodynamic and kinetic benefits of higher operating temperatures.

[0006] SOEC can be used to convert steam (H 2 O), carbon dioxide (CO 2 ) or both are directly converted into hydrogen (H 2 ), carbon monoxide (CO) or synthesis gas (H 2 +CO).

[0007] SOEC can be thermally integrated with a range of chemical syntheses to convert captured CO 2 and H 2 O recycling to synthetic natural gas, gasoline, methanol or ammonia can further improve efficiency compared to low-temperature electrolysis technology.

[0008] H 2 O or CO 2 The decomposition of O takes place at the electrodes of a solid oxide electrolysis cell (SOEC). Multiple cells are combined into a SOEC stack, and multiple stacks are combined into a SOEC device.

[0009] Fuel (H 2 O and / or CO 2 ) enters the process side of the SOEC, where it is (partially) converted into the product (H 2, CO or synthesis gas). The oxygen produced by the fuel side reforming is transferred via an electrochemical cell to the oxygen side of the SOEC where it is recombined into gaseous oxygen. It is usually transported away from the SOEC using a flushing fluid.

[0010] A solid oxide cell (SOC) is an electrochemical conversion device with two compartments (anode side and cathode side) separated by an electrolyte material made of solid oxide or ceramic electrolyte. It can be used as a solid oxide electrolyzer (SOEC) or a solid oxide fuel cell (SOFC). Such a cell is used, for example, for H 2 O<->H 2 Conversion between CO 2 The conversion between <-> CO and their mixtures is completely reversible.

[0011] When operating in SOEC mode, the goal is to produce H 2 , CO or H 2 The quality of the mixture of CO and CO (also called syngas) - and the converted gas (also called product gas (or product fluid)) can be critical to downstream applications. Therefore, it is desirable to minimize the presence of undesirable components (such as air) in the product fluid to obtain a high purity product fluid.

[0012] A SOEC device typically includes multiple stacks connected in parallel and / or in series, the number of which can meet the required production needs. In the SOEC mode, the cathode side can also be called the fuel side, and the anode side can also be called the oxygen side or flushing side.

[0013] Much attention has been paid to optimizing the performance of SOEC technology by improving the efficiency of the electrolysis stack. However, optimizing the process equipment that supports the SOEC stack is equally important. Optimizing the design of SOEC-based equipment is a balance between process complexity, energy consumption per unit of product gas, and production equipment cost.

[0014] For some uses of SOEC, steam is one of the necessary feeds. As is well known, before a water stream is used in an industrial system, it is usually necessary to perform some kind of water treatment on the water stream (the treated water may be referred to as process steam). Untreated water may contain impurities, which may cause damage or wear to the system. These impurities may cause the formation of scale, corrosion, deposits, etc. In addition, oxygen may not be needed in the process steam because it may cause corrosion, such as in pipes and heat exchangers. In addition, due to the high concentration of impurities in boiler water, droplets / entrainment are undesirable. For example, this is the case for the use in SOEC. Typically, raw water is first treated in an ion exchanger to remove minerals. The demineralized water is then passed through a deaerator to produce deaerated water, which is then sent to a boiler with a steam drum, where dry steam is produced, which can then be used as process steam. In the deaerator, oxygen is stripped from the water, and the stripped water is collected in a surge vessel. In the boiler, the deaerated water is heated in a heat exchanger and the heated water and steam mixture is separated in a steam drum to produce dry steam for feed. This representative prior art water treatment system has been Figure 6 and Figure 7 Shown in.

[0015] There remains a need to optimize the performance of SOEC devices to increase their industrial applicability and economic viability for the production of hydrogen, carbon monoxide, and synthesis gas. Summary of the invention

[0016] The present inventors have now developed a simplified water treatment system for treating or demineralizing water to produce oxygen-depleted and dry process steam suitable for use in, for example, solid oxide electrolysis.

[0017] In one aspect of the present invention, there is provided a water treatment system for producing oxygen-depleted and dry process steam (35), comprising:

[0018] A stripping tower (21) for stripping oxygen from water;

[0019] A fluid collector vessel for collecting oxygen-depleted liquid water from the stripping column;

[0020] A fluid separator vessel for collecting the liquid water-steam mixture and separating the water from the steam;

[0021] a heating device for evaporating liquid water into steam; and

[0022] wherein the fluid collector and the fluid separator are provided as a combined vessel (22) to collect oxygen-depleted liquid water from the stripping column (21) and separate the water from the steam; and

[0023] wherein the stripping tower (21) is arranged above the combined container (22) and is in direct fluid communication with the combined container (22); and

[0024] The heating device is arranged to provide steam to the lower part of the combined container (22).

[0025] The heating device comprises a heating element, which can be arranged below the combination container (22) and directly fluidically connected to the combination container (22), and / or the heating element can be arranged inside the combination container (22) and located at the lower part of the combination container (22).

[0026] One aspect of the present invention provides a water treatment process for producing oxygen-depleted and dry process steam, comprising the following steps:

[0027] - stripping oxygen from a demineralized water stream by passing the demineralized water stream through a packed bed and stripping oxygen therefrom, and passing oxygen stripping steam in a countercurrent direction to produce oxygen-depleted water;

[0028] - collecting the oxygen-depleted water in a combined container to obtain an oxygen-depleted water-steam mixture in the combined container;

[0029] - indirectly heating the liquid part of the water-steam mixture to produce wet steam;

[0030] - removing water droplets from wet steam by bubbling steam through the liquid portion of a water-steam mixture to produce dry steam;

[0031] The oxygen-depleted water-steam mixture in the combined container is used to supply oxygen stripping steam to the stripping tower to buffer the change in the demineralized water flow rate corresponding to each amount of dry steam produced, absorb the pressure difference between the upstream and downstream of the combined container, and remove water droplets from the wet steam;

[0032] To produce oxygen-depleted and dry process steam.

[0033] In one aspect, there is provided the use of the device according to the invention in a plant using steam as feed.

[0034] In one aspect, there is provided a method of producing hydrogen, comprising:

[0035] Producing oxygen-depleted and dry process steam according to the water treatment process for producing oxygen-depleted and dry process steam according to the present invention;

[0036] The oxygen-depleted and dry process steam is fed into a solid oxide electrolysis cell and subjected to high temperature electrolysis in the electrolysis cell to produce a hydrogen-rich product gas.

[0037] The water treatment system according to the invention simplifies the arrangement of equipment for operating a high temperature solid oxide electrolysis plant to produce, for example, hydrogen or a mixture of hydrogen and carbon monoxide. In particular, the invention enables the construction costs of the system to be reduced. Since the two vessels are combined into a single combined vessel, less metal is required for the reactor and less instrumentation is required for the operation of the control system. If the electrolysis system is operated at moderate pressures, so that any pressure fluctuations during the operation of the high temperature electrolysis plant are generally not too large, it is particularly convenient to combine the surge vessel of the deaerator with the steam drum of the boiler into one combined vessel.

[0038] BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 One embodiment of a water treatment system according to the present invention is shown.

[0040] Figure 2 One embodiment of a water treatment system according to the present invention is shown.

[0041] Figure 3 One embodiment of a water treatment system according to the present invention is shown.

[0042] Figure 4 One embodiment of a water treatment system according to the present invention is shown.

[0043] Figure 5 One embodiment of a water treatment system according to the present invention is shown.

[0044] Figure 6 A prior art water treatment system is shown.

[0045] Figure 7 A prior art water treatment system is shown. DETAILED DESCRIPTION OF THE INVENTION

[0047] Disclosed herein is a water treatment system as defined above.

[0048] The inventors unexpectedly discovered that in high temperature solid oxide electrolysis, the water treatment system for producing process steam can be simplified compared to the water treatment system of the prior art. Specifically, they found that instead of first passing the demineralized water through a deaerator including a stripping tower and a surge vessel, and then through a boiler including a steam drum and a heating device, the function of the surge vessel can be combined with the function of the steam drum in a combined vessel. Therefore, they found that the stripping tower can be connected to the upper part of the combined vessel, and the heating device can be connected to the lower part of the combined vessel, so that during operation, the liquid phase (boiler water) in the combined vessel can be heated by the heating device to produce steam to the bottom of the combined vessel, and the steam thus rising passes through the boiler water in the combined vessel to remove the water droplets carried from the steam, which can be used as a steam supply for the stripping tower, and as a dry process steam discharged from the upper part of the combined vessel. They also found that this simplification has many benefits. For example, the entire container can be omitted. This not only reduces the amount of metal used to build the equipment, but also reduces the pipeline requirements, process control requirements, heating requirements, etc.

[0049] When referring to the lower portion or bottom of a combined vessel, this refers to the portion of the vessel occupied by the liquid phase during operation. When referring to the upper portion or top of a combined vessel, this refers to the portion of the vessel occupied by the gas phase during operation. The exact height of the liquid surface may vary slightly while the system is operating.

[0050] In this article, process steam is referred to as dry steam, which means that the liquid water droplets carried in the steam have been removed. In practice, this dry steam is called "dry" steam. The water droplets are potentially harmful because they may contain high concentrations of impurities that accumulate in the liquid phase of the liquid drum.

[0051] In the prior art, it is understood that water treatment to produce process steam is performed by first removing minerals through a demineralizer, then removing oxygen in a deaerator, and finally producing dry steam in a boiler. The deaerator usually includes a stripping column and a surge vessel to collect the deaerated liquid and absorb pressure fluctuations. The boiler usually includes heating elements and a steam drum to separate water droplets from the steam and absorb pressure fluctuations.

[0052] A "surge vessel" is therefore a fluid collector vessel which, in the present context, is understood to be a container arranged to contain a buffer capacity of a fluid, in the present context liquid water. The function of the buffer capacity is to compensate for variations in the feed flow rate into the vessel and the product flow rate out of the vessel. The buffer capacity is preferably used both to compensate for flow variations due to slow level control reactions in the vessel and to provide liquid capacity to accommodate differences in operating pressures and to prevent any fluctuations in operating pressures between upstream and downstream of the surge vessel, thereby ensuring safe operation of the process. In other words, the surge vessel functions as a buffer water body and absorbs pressure fluctuations upstream or downstream of the surge vessel. A stripping column equipped with a packed bed can be integrated with a surge vessel and can then be referred to as a "degasser".

[0053] A "steam drum" is a fluid separator vessel, which in the present context is understood to be a vessel arranged to store steam and to separate dry (i.e. saturated) steam from a steam-water mixture. The steam-water mixture is fluidly connected to a heating device which provides indirect heating to produce steam. Typically, the heating device comprises a heating element in the form of a heat exchanger, but the heating element may also comprise a heating coil within the steam drum, providing heat to the water. The steam produced by the heating device passes through a fluid buffer capacity (in the present context, liquid water) contained in the steam drum, the function of which is to condense liquid water droplets present in the produced steam, thereby producing dry steam, and also to compensate for variations in the feed flow rate into the vessel and the product flow rate out of the vessel. The buffer capacity should preferably be used both to compensate for flow variations due to slow level control reactions in the vessel, and to provide liquid capacity to accommodate differences in operating pressures, as well as to prevent any fluctuations in operating pressures between upstream and downstream of the steam drum, thereby ensuring safe operation of the process. The buffer capacity should also be sufficient to ensure that the hot surfaces of the heating device are always covered with water during system startup and shutdown (e.g. due to insufficient water supply). The density difference between the hotter and cooler water helps the "hotter" water and dry steam accumulate at the top of the steam drum, while the cooler water sinks to the bottom of the vessel. In other words, the steam drum acts to separate the water droplets from the steam, it acts as a buffer to compensate for flow changes, ensures that the heating surface is covered, and it also serves to absorb pressure surges and store the generated steam.

[0054] Stripping tower

[0055] In the context of water treatment, the purpose of a stripping column is generally to strip oxygen from a liquid water feed (liquid phase). Stripping can be achieved by passing steam (gas phase) upward through the stripping column while the liquid water feed passes downward through the stripping column, which allows oxygen to transfer from the liquid phase to the gas phase. As known to those skilled in the art, it is desirable to arrange the internal components of the stripping column to obtain a larger liquid surface. As known to those skilled in the art, it is also desirable to extend the stripping column upward to allow a reasonable contact time between the liquid phase and the gas phase.

[0056] Typically, the stripping tower (21) comprises a packed bed, baffles and / or other internals to allow oxygen to be stripped from liquid water within the stripping tower (21). Typically, the stripping tower (21) comprises a liquid water inlet arranged at an upper portion of the stripping tower. Typically, the stripping tower (21) comprises a steam outlet arranged at an upper portion of the stripping tower.

[0057] Composite Container

[0058] In operation, the combined vessel will include a liquid phase in the lower part of the combined vessel and a gas phase in the upper part of the combined vessel. The liquid phase will form a buffer capacity for the liquid and also has the function of removing water droplets entrained in the steam as the steam bubbles through the liquid phase. Before using the steam for high-temperature solid oxide electrolysis, the water droplets need to be removed from the steam. Any liquid water entrained in the steam may cause corrosion to the solid oxide electrolysis cell unit. In addition, any impurities present in the raw water feed that are not captured by the demineralizer will accumulate in the liquid phase of the combined vessel (boiler water, BW), and such impurities may also be harmful to the solid oxide electrolysis cell unit. The gas phase above the liquid phase will include dry steam, a portion of which will be directed to the stripping tower and a portion will leave the combined vessel to form dry process steam suitable for various processes, and is particularly suitable for high-temperature solid oxide electrolysis.

[0059] In one embodiment of the water treatment system of the present invention, the combined container includes a process steam outlet disposed at the upper portion of the combined container (22). The combined container (22) may further include a demister (36) disposed above the combined container (22) and in fluid communication with the process steam outlet. The demister is a device generally mounted on a vapor-liquid separator vessel for enhancing the removal of entrained liquid droplets from the product vapor.

[0060] Any impurities present in the raw water feed that are not captured by the demineralizer will accumulate in the liquid phase (boiler water, BW) of the combined vessel. Therefore, it may be necessary to repeatedly or continuously discharge a small portion of the liquid phase within the combined vessel. In one embodiment of the water treatment system according to the present invention, the combined vessel (22) includes a purge outlet (37) in the lower part of the vessel.

[0061] In one embodiment of the water treatment system according to the invention, direct fluid communication between the combining vessel and the stripping column allows recirculation (23, 24) of fluid between the combining vessel (22) and the stripping column (21).

[0062] In one embodiment of the water treatment system of the present invention, the heating device comprises a heat exchanger (32) arranged below the combined container (22) and in direct fluid communication (33, 34) with the combined container (22) for indirect heat transfer to any fluid flowing to and from the heat exchanger (32). In one embodiment of the water treatment system of the present invention, the heating device comprises a heating coil (44) arranged inside and below the combined container (22) for indirect heat transfer to any fluid in the combined container (22). The heating device may include a heating element in the form of a heat exchanger arranged below the combined container and in direct fluid communication (33, 34) with the combined container, and a heating element in the form of a heating coil arranged inside and below the combined container (22).

[0063] The combined containers can be arranged vertically or horizontally as required.

[0064] Demineralizer

[0065] In the context of water treatment, the first step is usually to pass the raw water feed stream through a mineralizer to remove minerals and other impurities from the raw water feed, thereby producing demineralized water (which may be referred to as DMW). The demineralizer typically includes one or more ion exchange columns to remove impurities by ion exchange. However, other methods of removing ions are contemplated. In one embodiment of the water treatment system according to the present invention, the system also includes a demineralizer (11) located upstream of the stripping column (21) and in fluid communication with the stripping column (21).

[0066] Process control device

[0067] In one embodiment of the water treatment system according to the present invention, the system also includes a process control device for controlling the operation of the water treatment system. In order to make the system run well, the system preferably includes a device for controlling various flows, pressures and temperatures within the system. The process control device may also include a computer program for obtaining operating parameters of the water treatment system, comparing them with preset values, and adjusting the actual settings according to the computer program.

[0068] Technology

[0069] Disclosed herein is a water treatment process as defined above.

[0070] In one embodiment of the water treatment process according to the present invention, the operating pressure in the combined vessel is in the range of 0.7-10 bar absolute pressure, such as 0.9-8 bar, or 1-7 bar absolute pressure.

[0071] In one embodiment of the water treatment process according to the invention, in one embodiment of the water treatment system according to the invention, the oxygen-depleted and dry process steam is subjected to a subsequent demisting step.

[0072] In one embodiment of the water treatment method according to the present invention, additional oxygen-depleted steam is added from an external source to the liquid portion of the water-steam mixture in the combination vessel. If the additional oxygen-depleted steam from the external source is of high purity, it can be added directly to the combination vessel. Otherwise, it can be passed through a heating coil to provide indirect heating.

[0073] Purpose of water treatment system

[0074] In one embodiment, the water treatment system according to the present invention is used in an apparatus using steam as feed.

[0075] In one embodiment, there is provided a method for producing hydrogen, comprising:

[0076] Production of oxygen-depleted and dry process steam according to the invention;

[0077] The oxygen-depleted and dry process steam is fed into a solid oxide electrolysis cell and subjected to high temperature electrolysis in the electrolysis cell to produce a hydrogen-rich product gas.

[0078] In addition to oxygen-depleted and dry process steam, a feed comprising carbon dioxide and / or carbon monoxide may be fed to the solid oxide electrolysis cell for high temperature electrolysis.

[0079] exist Figure 1In the process, a raw water stream (1) is demineralized in an ion exchanger (11) to obtain demineralized water (12) having a very low mineral content. Demineralized water may be abbreviated as DMW. The demineralized water may still contain some oxygen and is sent to a vertically arranged stripping column (21) comprising a packed bed in which oxygen is stripped from the water using steam (23). Oxygen and steam leave the container from the top (27), while oxygen-depleted water leaves the container from the bottom of the container, below the packed bed (24). The demineralized oxygen-depleted water is collected in a horizontally arranged combination container (22) below the packed bed. The demineralized oxygen-depleted water collected in the combination container may be referred to as boiler water (BW). The boiler water circulates (34) to a heat exchanger (32) located below the combination container (22), in which steam is generated, and the steam-water mixture is recirculated (33) to the combination container (22). The boiler water forms a liquid phase which covers at least the bottom of the combined vessel (22) and the heating surface of the heat exchanger (32). The recirculated steam-water mixture is bubbled through the liquid phase in the combined vessel, separating water from the steam-water mixture, and producing a dry steam phase above the liquid phase in the combined vessel (22). The dry steam is supplied (23) to the stripping column (21) and a demister (36) arranged at the top of the combined vessel (22). The demister reduces the carryover of liquid water droplets to the steam, and demineralized oxygen-depleted and dry steam (35) is collected from the demister (36) and can be used in any process requiring demineralized oxygen-depleted and dry steam, such as a SOEC system.

[0080] In order to avoid the accumulation of residual salt in the boiler water in the combined vessel (22), it is necessary to purge a small portion of the stream (37) from the liquid phase of the boiler water. This purge may be called blowdown.

[0081] The combined vessel (22) operates within a pressure range of 1-8 bar absolute and controls the flow of raw water to the water treatment system (1), the flow of dry and oxygen-depleted steam from the water treatment system and the heat supplied to the heat exchanger so that the boiler water forms a liquid phase that at least covers the bottom of the combined vessel and the heating surface of the heat exchanger.

[0082] exist Figure 2 In the figure, it is shown that Figure 1 A similar water treatment system, except that the demister (36) is arranged in a separate vessel on top of the surge vessel.

[0083] exist Figure 3 In the figure, it is shown that Figure 2 A similar water treatment system, except that steam produced by an external process (41) is introduced into the liquid phase of the boiler water within the combined vessel (22).

[0084] exist Figure 4 In the figure, it is shown that Figure 2A similar water treatment system, except that hot process gas (e.g., steam) from an external process (42) is passed through heating coils in the liquid phase of boiler water within the combination vessel (22), thereby transferring heat from the hot process gas to the boiler water by indirect heat transfer.

[0085] exist Figure 5 In the figure, it is shown that Figure 2 A similar water treatment system, except that the purge stream (37) from the combination vessel (22) is sent to an external boiler (43) and the steam generated is recycled into the liquid phase of the boiler water within the combination vessel (22).

[0086] exist Figure 6 In FIG, a representative prior art water treatment system is shown, in which a raw water stream (1) is demineralized in an ion exchanger (11), and the purified water with a very low mineral content can be referred to as demineralized water DMW (12). The demineralized water may still contain some oxygen and is sent to a stripping column (21) with a packed bed, where steam (23) is used to strip oxygen from the water. The oxygen and steam leave from the top of the container, while the demineralized and oxygen-depleted water leaves from the bottom of the stripping column (21), below the packed bed (24). The oxygen-depleted and demineralized water, now called boiler feed water BFW, is collected in a surge container (28) below the packed bed. The main purpose of the surge container is to contain the buffer capacity of the BFW. In order to keep the BFW in the surge container (28) at boiling point and generate the required steam (23) for the stripping column 21, heat is then added directly to the surge container by injecting steam from an external source (26) into the surge container (28). Alternatively, steam may be added indirectly by heat exchange with coils within the surge vessel (23).

[0087] In this embodiment, the stripping column (21) equipped with a packed bed is integrated with a surge vessel, which may be referred to as a "degasser". The degasser operates in the pressure range of 1 bar to 5 bar absolute.

[0088] The BFW (25) is pumped from the surge vessel (28) to the boiler. The boiler comprises a heat exchanger (32) in which steam is produced, and a vessel for separating the steam and water mixture from the heat exchanger, which vessel is referred to as a "steam drum" (31). The steam drum (31) is connected to the heat exchanger by a water conduit (34) and a steam / water mixture conduit (33). Alternatively, the steam drum and heat exchanger may be integrated together, or some combination of the two approaches may be employed. A demister (36) is arranged at the top of the steam drum (31) to reduce the amount of liquid water droplets that are carried over into the steam leaving the steam drum, which steam may be supplied to consumers.

[0089] In order to avoid the accumulation of residual salts in the boiler water in the steam drum (31) and the heat exchanger (32), it is necessary to purge a small portion of the stream (37) from the liquid phase of the steam drum (31).

[0090] exist Figure 7 In the figure, it is shown that Figure 6 A similar representative prior art water treatment system is described except that hot process gas (e.g., steam) (42) from an external process is passed through a heating coil in the liquid phase of boiler water within the combination vessel (22) thereby transferring heat from the hot process gas to the boiler water by indirect heat transfer. Example

[0091] Example 1: High temperature solid oxide electrolysis system, the water treatment system of which includes a combined container

[0092] exist Figure 2 An embodiment of the invention is described in . In an ion exchanger (11) comprising acidic and basic ion exchange resins, 21.8 m / h 3 The raw water stream (1) is demineralized. The demineralized water DMW (12) is fed into a stripping column (vertical vessel) comprising a packed bed (21) filled with 25 mm IMTP random packing, wherein oxygen is stripped from the water by means of steam (23) delivered below the packed bed. 100 kg / h of oxygen and steam leave the vessel from the top (27) of the stripping column and the resulting oxygen-depleted water leaves the vessel from the bottom below the packed bed (24). The oxygen-depleted water is collected in a combined vessel (22) below the packed bed. The combined vessel is used to hold a buffer capacity of oxygen-depleted water, which may be referred to as boiler water. The boiler water is maintained at boiling point in the combined vessel (22) by providing indirect heat from a heat exchanger (32) located below the combined vessel. The cooler and heavier water sinks to the bottom of the combined vessel and is delivered to the heat exchanger through an opening (34). The heat exchanger transfers heat to the boiler water at a rate of 11.5 MW. The steam generated in the heat exchanger (32) is transferred through an opening (33) to a combined vessel. The combined vessel is used to transfer the steam to the bottom of the stripping column and remove the liquid water droplets trapped in the steam through a demister (36) arranged above the combined vessel. Oxygen-depleted and dry process steam (35) is taken out from the demister at a rate of 21.5 t / h to produce 20,000 Nm 3 / hH 2 .

[0093] To avoid the accumulation of residual salts in the combined vessel, a purge at a rate of 200 kg / h is required from the liquid phase (37). Oxygen-depleted and dry process steam is fed to the SOEC stack operating at 2 barg and 750°C.

[0094] The advantage of such a system is that it can simplify the construction of the steam hydrogen production system, thereby reducing the construction cost of the system. Less metal is required for the reactor and less equipment is required to control the operation of the control system.

Claims

1. A water treatment system for producing oxygen-depleted and dry process steam (35), comprising: A stripping tower (21) for stripping oxygen from water; A fluid collector vessel for collecting oxygen-depleted liquid water from the stripping column; A fluid separator vessel for collecting the liquid water-steam mixture and separating the water from the steam; a heating device for evaporating liquid water into steam; and wherein the fluid collector and the fluid separator are provided as a combined vessel (22) to collect oxygen-depleted liquid water from the stripping column (21) and separate the water from the steam; and wherein the stripping tower (21) is arranged above the combined container (22) and is in direct fluid communication with the combined container (22); and The heating device is arranged to provide steam to the lower part of the combined container (22).

2. The water treatment system according to claim 1, wherein the heating device comprises a heating element, which is arranged below the combination container (22) and is in direct fluid communication with the combination container (22).

3. The water treatment system according to any one of claims 1 or 2, wherein the heating device comprises a heating element, which is arranged inside the combination container (22) and located at the lower part of the combination container (22).

4. The water treatment system according to any one of the preceding claims, wherein the combined container comprises a process steam outlet arranged at an upper part of the combined container (22).

5. The water treatment system according to claim 4, wherein the combined container (22) further comprises a demister (36) arranged above the combined container (22) and in fluid communication with the process steam outlet.

6. A water treatment system according to any one of the preceding claims, wherein the combined container (22) comprises a purge outlet (37) in a lower part of the container.

7. A water treatment system according to any one of the preceding claims, wherein direct fluid communication between the combining vessel and the stripping column allows recirculation (23, 24) of fluid between the combining vessel (22) and the stripping column (21).

8. A water treatment system according to any one of the preceding claims, wherein the stripping column (21) comprises a packed bed, baffles and other internals to allow stripping of oxygen from liquid water within the stripping column (21).

9. The water treatment system according to any one of the preceding claims, wherein the stripping tower (21) further comprises a liquid water inlet arranged at an upper portion of the stripping tower.

10. The water treatment system according to any one of the preceding claims, wherein the stripping tower (21) further comprises a steam outlet arranged at an upper portion of the stripping tower.

11. A water treatment system according to any one of the preceding claims, wherein the heating device comprises a heat exchanger (32) arranged below the combined container (22) and in direct fluid communication (33, 34) with the combined container (22) to indirectly transfer heat to any fluid flowing to and from the heat exchanger (32).

12. A water treatment system according to any one of the preceding claims, wherein the heating device comprises a heating coil (44), which is arranged inside the combination container (22) and located at the lower part of the combination container (22) to indirectly transfer heat to any fluid in the combination container (22).

13. A water treatment system according to any of the preceding claims, wherein boiler water is circulated (34) to a heat exchanger (32) arranged below the combination vessel (22), steam is generated in the heat exchanger, and the steam-water mixture is recirculated (33) to the combination vessel (22).

14. The water treatment system according to any one of the preceding claims, further comprising a demineralizer (11) located upstream of the stripping column (21) and in fluid communication with the stripping column (21).

15. A water treatment system according to any one of the preceding claims, further comprising process control means for controlling the operation of the water treatment system.

16. A water treatment process for producing oxygen-depleted and dry process steam comprising the following steps: - stripping oxygen from a demineralized water stream by passing the demineralized water stream through a packed bed and passing oxygen stripping steam in a countercurrent direction to produce oxygen-depleted water; - collecting the oxygen-depleted water in a combined container to obtain an oxygen-depleted water-steam mixture in said combined container; - indirectly heating the liquid part of the water-steam mixture to produce wet steam; - removing water droplets from wet steam by bubbling steam through the liquid portion of a water-steam mixture to produce dry steam; - wherein the oxygen-depleted water-steam mixture in the combined vessel is used to supply oxygen stripping steam to the stripping column to buffer the change in the demineralized water flow rate corresponding to each amount of dry steam produced, absorb the pressure difference between the upstream and downstream of the combined vessel, and remove water droplets from the wet steam; To produce oxygen-depleted and dry process steam.

17. A process according to claim 16, wherein the operating pressure in the combined vessel is in the range of 0.7-10 bar absolute, such as 0.9-8 bar, or 1-7 bar absolute.

18. A process according to any one of claims 16-17, wherein the oxygen-depleted and dry process vapour is subjected to a subsequent demisting step.

19. A process according to any one of claims 16 to 18, wherein oxygen-depleted steam is added from an external source to the liquid portion of the water-steam mixture in the combining vessel.

20. Use of the device according to any one of claims 1 to 15 in a plant using steam as feed.

21. A method for producing hydrogen, comprising: · production of oxygen-depleted and dry process steam according to any one of claims 16 to 19; The oxygen-depleted and dry process steam is fed into a solid oxide electrolysis cell and subjected to high temperature electrolysis in the electrolysis cell to produce a hydrogen-rich product gas.

22. A process according to claim 21, wherein in addition to oxygen-depleted and dry process steam, a feed comprising carbon dioxide and / or carbon monoxide is fed to the solid oxide electrolysis cell for high temperature electrolysis.

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