A water treatment system for producing oxygen-deficient dry steam and a method for manufacturing the same

Abstract

The present invention relates to an improved water treatment system and method for producing oxygen-deficient dry process steam suitable for use in high-temperature solid oxide electrolysis. This system and method are simplified compared to prior art systems and processes.

Description

Technical Field

[0001] Field The present invention relates to an improved water treatment system and method for producing oxygen-deficient dry process steam suitable for use in high-temperature solid oxide electrolysis.

Background Art

[0002] Background Due to climate change, the global shift from fossil fuels to renewable energy is accelerating. Usually, renewable energy is from wind power generation or solar power generation. The problem with renewable energy is its intermittent nature.

[0003] Power-to-X (PtX) is a term used for the power conversion, energy storage, and reconversion pathways that use electricity. Power-to-X conversion technologies have the ability to decouple electricity from the power sector and enable its use in other sectors (such as transportation and chemicals), thus solving the problem of variable renewable energy generation.

[0004] Currently, electrolysis is the core technology of the PtX method, and X is typically hydrogen, syngas, chemicals, or synthetic fuels. Combining electrolysis with renewable electricity can decouple the production of fuels and chemicals from fossil resources.

[0005] Solid oxide electrolysis (SOE) technology is particularly attractive because of its higher conversion efficiency than low-temperature electrolysis - due to the favorable thermodynamics and kinetics at higher operating temperatures.

[0006] SOEC can be used to directly electrochemically convert steam (H2O), carbon dioxide (CO2), or both into hydrogen (H2), carbon monoxide (CO), and syngas (H2 + CO), respectively.

[0007] The SOEC can be thermally integrated with various chemical syntheses and recycle the recovered CO2 and H2O into synthetic natural gas, gasoline, methanol, and ammonia.

[0008] The decomposition of H2O or CO2 takes place at the solid oxide electrolysis cell (SOEC) electrodes. Multiple cells are grouped into an SOEC stack, and multiple stacks are grouped into an SOEC plant.

[0009] The fuel stream (H2O and / or CO2) enters the process side of the SOEC, where it is (partially) converted into the product (H2, CO, or syngas). The oxygen generated by the conversion on the fuel side moves through the electrochemical cell to the oxygen side of the SOEC, where it recombines as gaseous oxygen. Oxygen is typically transported from the SOEC with a purge 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 a solid oxide or ceramic electrolyte. It can be used either as a solid oxide electrolysis cell (SOEC) or as a solid oxide fuel cell (SOFC). Such cells are completely reversible for components such as H2O <-> H2 and CO2 <-> CO and their mixtures.

[0011] When operating in the SOEC mode, the aim is to produce H2, CO, or a mixture of H2 and CO (also called syngas), and the quality of the conversion gas, also called the product gas (or product fluid stream), is important for downstream applications. Therefore, in order to obtain a high-purity product fluid stream, it is desirable to minimize the presence of unwanted components (such as air) in the product fluid stream.

[0012] An SOEC plant generally consists of multiple stacks connected in parallel and / or in series in an amount sufficient to meet the required production volume. In the SOEC mode, the cathode side is also called the fuel side, and the anode side is also called the oxygen side or the purge side.

[0013] Much focus has been placed on optimizing the performance of SOEC technology by increasing the efficiency of the electrolysis stack. However, optimizing the process equipment that supports the SOEC stack is equally important. Optimizing the design of an SOEC-based plant involves balancing the complexity of the process, the energy consumption per unit of product gas, and the equipment manufacturing cost.

[0014] In some applications of SOEC, steam is required as one of the feeds. Generally, it is known that the water stream is subjected to some water treatment (sometimes called process steam) before being used in an industrial system. Untreated water contains impurities that can cause damage and wear to the system. Such impurities can cause the formation of scales, corrosion, deposits, etc. Also, oxygen can cause corrosion in pipes, heat exchangers, etc., and may not be required in process steam. Further, due to the high concentration of impurities in boiler water, droplets and entrainment are also not desirable. This is the case, for example, in applications with SOEC. Generally, 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. This deaerated water is then passed through a boiler equipped with a steam drum, where dry steam is produced and can be used as process steam. In the deaerator, oxygen is removed from the water, and the removed water is collected in a surge vessel. In the boiler, the deaerated water is heated in a heat exchanger, and the mixture of heated water and steam is separated in the steam drum to produce dry steam for use as a feed. Such a typical prior art water treatment system is shown in FIGS. 6 and 7. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0015] However, there remains a need to optimize the performance of SOEC plants in order to improve the industrial applicability and profitability of SOEC plants that produce hydrogen, carbon monoxide, and syngas. MEANS FOR SOLVING THE PROBLEMS

[0016] Summary of the Invention Here, the inventors have developed a simplified water treatment system that treats water or desalinated water to produce, for example, oxygen-depleted dry process steam suitable for use in solid oxide electrolysis.

[0017] In one aspect of the present invention, there is provided a water treatment system for preparing oxygen-depleted dry process steam (35), the water treatment system comprising: - a stripper (21) for removing oxygen from water; - a liquid collection container for collecting oxygen-depleted liquid water from the stripper; - a fluid separation container for collecting a liquid purified water-steam mixture and separating water from the steam; - a heating device for evaporating the liquid water into steam, wherein the fluid collection container and the fluid separation container are provided as a composite container (22) for collecting oxygen-depleted liquid water from the stripper (21) and separating water and steam; and wherein the stripper (21) is disposed above the composite container (22) and is in direct fluid communication with the composite container (22); and wherein the heating device is disposed to supply steam to the lower part of the composite container (22).

[0018] The heating device includes a heating element disposed below the composite container (22) and capable of being in direct fluid communication with the composite container (22), and / or the heating element is disposed within the composite container (22) and can be disposed at the lower part of the composite container (22).

[0019] In one aspect of the present invention, there is provided a method of water treatment for producing oxygen-depleted dry process steam, comprising the following steps: - passing a desalinated water stream through a packed bed and passing oxygen stripping steam in a countercurrent direction to remove oxygen from the desalinated water stream and produce oxygen-depleted water; - Collecting oxygen-deficient water in a composite container to obtain an oxygen-deficient water-vapor mixture in the composite container; - Indirectly heating the liquid portion of the water-vapor mixture to generate wet steam; - Bubbling the wet steam into the liquid portion of the water-vapor mixture to remove water droplets from the wet steam and produce dry steam; Here, the oxygen-deficient water-vapor mixture in the composite container supplies oxygen stripping steam to the stripper, buffers fluctuations in the desalinated water flow per unit of dry steam produced, absorbs the pressure difference between the upstream and downstream of the composite container, and serves to remove water droplets from the wet steam; Producing process steam that has been dried by removing oxygen.

[0020] In one aspect, the use of the device according to the present invention is provided in a plant that uses steam as a feed.

[0021] In one aspect, a method for producing hydrogen is provided that includes the following; - Producing oxygen-deficient dry process steam according to the water treatment method for producing oxygen-deficient dry process steam according to the present invention; - Supplying the oxygen-deficient and dried process steam to a solid oxide electrolysis cell and performing high-temperature electrolysis therein to produce a hydrogen-rich product gas.

[0022] The water treatment system according to the present invention simplifies the plant setup for operating a high-temperature solid oxide electrolysis plant for producing, for example, hydrogen gas or a composite gas of hydrogen and carbon monoxide. In particular, according to the present invention, the construction cost of the system can be reduced. Since two containers are combined into one composite container, less metal is required for the reactor, and fewer devices are required for operating control of the system. Combining the surge container of the degassing device and the steam drum of the boiler into one container is particularly advantageous when operating the electrolysis system at a moderate pressure such that the pressure fluctuations in a typical operating high-temperature electrolysis plant do not become too large.

Brief Description of the Drawings

[0023] Legend of the Figures Figure 1 shows an embodiment of the water treatment system according to the present invention. Figure 2 shows an embodiment of the water treatment system according to the present invention. Figure 3 shows an embodiment of the water treatment system according to the present invention. Figure 4 shows an embodiment of the water treatment system according to the present invention. Figure 5 shows an embodiment of the water treatment system according to the present invention. Figure 6 shows a prior art water treatment system. Figure 7 shows a prior art water treatment system.

Mode for Carrying Out the Invention

[0024] Detailed Description of the Invention What is disclosed in this specification is the water treatment system defined above. The inventors have surprisingly found that in high-temperature solid oxide electrolysis, it is possible to simplify a water treatment system for producing process steam as compared with prior art water treatment systems. In particular, instead of first passing demineralized water through a deaerator including a stripper and a surge vessel and then through a boiler including a steam drum and a heating device, it has been found that the functions of the surge vessel and the steam drum can be combined into a composite vessel. Thus, by connecting the stripper to the upper part of the composite vessel and the heating device to the lower part of the composite vessel, during operation, the liquid phase (boiler water) in the composite vessel is heated by the heating device to generate steam at the bottom of the composite vessel, and thus, the steam that rises through the boiler water in the composite vessel and removes the water droplets entrained from the steam can be used not only as the steam supply to the stripper but also as the dry process steam exiting from the upper part of the composite vessel. It has also been found that there are many advantages to such simplification. For example, the entire vessel can be omitted. This not only reduces the amount of metal used in plant construction, but also reduces piping requirements, process control requirements, heating requirements, etc.

[0025] When referring to the lower part or bottom of the composite container, this means the part of the container occupied by the liquid phase during operation. When referring to the upper part or top of the composite container, this means the part of the container occupied by the vapor phase during operation. The exact height of this liquid level may vary somewhat during the operation of the system.

[0026] In this specification, process steam is called dry steam, which means that the water droplets contained in the steam have been removed. In practice, such dry steam is called "dry" steam. Water droplets may be harmful because they may contain high concentrations of impurities accumulated in the liquid phase of the liquid drum.

[0027] In the prior art, it has been understood that water treatment for producing process steam is carried out by first removing minerals with a desalination device, then removing oxygen with a deaeration device, and finally producing dry steam with a boiler. The deaeration device usually consists of a stripper and a surge vessel for recovering the deaerated liquid and absorbing the sudden increase in pressure. The boiler usually includes a heating element and a steam drum for separating water droplets from the steam and absorbing the sudden increase in pressure.

[0028] Therefore, a "surge vessel" is a fluid recovery container, and in this specification, it is understood as a container arranged to include a buffer volume (buffer solution) of a fluid (liquid water in this specification). The buffer volume serves to cover the fluctuations in the supply flow to the container and the fluctuations in the product flow from the container. The buffer volume preferably serves to cover the flow rate fluctuations caused by the slow action of the liquid level in the container on the process control, while allowing the difference in operating pressure and providing a buffer volume that prevents the fluctuations in the operating pressures upstream and downstream of the surge vessel, enabling the safe operation of the process. In other words, the surge vessel serves as a water buffer and absorbs the pressure surges upstream or downstream of the surge vessel. A stripper with a packed bed is integrated with the surge vessel and may also be called a "deaeration device".

[0029] The "steam drum" is a fluid separation vessel, which in this specification is understood as a vessel arranged to store steam and separate dry (i.e., saturated) steam from a steam - water mixture. The steam - water mixture is in fluid communication with a heating device that performs indirect heating to generate steam. Generally, the heating device includes a heating element in the form of a heat exchanger, although the heating element can also be composed of heating coils within the steam drum that impart heat to water. The steam generated by the heating device passes through a buffer volume of fluid (liquid water in this specification) contained within the steam drum. This buffer volume serves to condense the liquid droplets present in the generated steam to produce dry steam and also covers fluctuations in the supply flow rate to the vessel and the product flow rate from the vessel. The buffer volume preferably covers flow rate fluctuations due to the slow operation of liquid level control within the vessel, prevents fluctuations in the operating pressures upstream and downstream of the steam drum, provides a liquid volume that allows a difference in operating pressures, and enables the safe operation of the process. The buffer volume must also be sufficient to ensure that the hot surface of the heating device is always covered with water during start - up and shut - down of the system (such as water shortage). Due to the density difference between hot water and cold water, "hotter" water and dry steam accumulate at the upper part of the steam drum, and cold water sinks to the lower part of the vessel. That is, the steam drum separates water droplets and steam, serves as a water buffer to cover flow rate fluctuations, reliably covers the heating surface, absorbs rapid pressure increases, and stores the generated steam.

[0030] Stripper In the context of water treatment, the purpose of a stripper is generally to remove oxygen from a liquid water supply (liquid phase). The removal (stripping) can be achieved by passing steam (vapor phase) upward through the stripper while the liquid water supply passes downward through the stripper, thereby passing oxygen from the liquid phase to the vapor phase. As is known to those skilled in the art, it is desirable to arrange the internals of the stripper to obtain a large liquid surface area. Also, as is known to those skilled in the art, it is desirable to extend the stripper upward to ensure an appropriate contact time between the liquid phase and the vapor phase.

[0031] Generally, the stripper (21) includes a packed bed, baffles and / or other internals to remove oxygen from the liquid water within the stripper (21). Generally, the stripper (21) includes a liquid water inlet disposed at the upper part of the stripper. Generally, the stripper (21) includes a vapor outlet disposed at the upper part of the stripper.

[0032] Composite container During operation, the composite vessel includes a liquid phase at the lower part of the composite vessel and a vapor phase at the upper part of the composite vessel. The liquid phase forms a liquid buffer volume and also serves to remove water droplets entrained in the vapor as bubbles pass through and agitate the liquid phase. It is necessary to remove the water droplets from the vapor before use in high-temperature solid oxide electrolysis. The liquid moisture contained in the vapor may cause corrosion of the solid oxide electrolysis cell unit. Further, impurities present in the raw water supply and not captured by the desalination device accumulate in the liquid phase (boiler water, BW) of the composite vessel, and such impurities may also have an adverse effect on the solid oxide electrolysis cell unit. The vapor phase above the liquid phase contains dry vapor, a part of which is led to the stripper and a part exits the composite vessel to form dry process steam useful for various processes, particularly high-temperature solid oxide electrolysis.

[0033] In one embodiment of the water treatment system according to the present invention, the composite vessel includes a process steam outlet disposed at the upper part of the composite vessel (22). The composite vessel (22) can further include a demister (36) disposed above the composite vessel (22) and in fluid communication with the process steam outlet. A demister is a device often attached to a vapor-liquid separator to facilitate the removal of droplets entrained in the product vapor.

[0034] Impurities present in the raw water supply and not captured by the desalination device accumulate in the liquid phase (boiler water, BW) of the composite vessel. Therefore, it may be necessary to repeatedly or continuously discard a small part of the liquid phase within the composite vessel. In one embodiment of the water treatment system according to the present invention, the composite vessel (22) includes a purge outlet (37) at the lower part of the vessel.

[0035] In one embodiment of the water treatment system according to the present invention, the direct fluid communication between the composite vessel and the stripper provides for the recirculation (23, 24) of fluid between the composite vessel (22) and the stripper (21).

[0036] In one embodiment of the water treatment system according to the present invention, the heating device is disposed below the composite vessel (22) for indirect heat transfer to any fluid flowing between it and the heat exchanger (32), and includes the heat exchanger (32) in direct fluid communication with the composite vessel (22). In one embodiment of the water treatment system according to the present invention, the heating device includes a heating coil (44) disposed within and at the lower part of the composite vessel (22) for indirect heat transfer to any fluid within the composite vessel (22). The heating device can include both a heating element in the form of a heat exchanger disposed below the composite vessel and in direct fluid communication (33, 34) with the composite vessel, and a heating element in the form of a heating coil disposed inside and at the lower part of the composite vessel (22).

[0037] The composite vessel can be arranged vertically or horizontally as required.

[0038] Desalination device In relation to water treatment, generally, the first step is to pass the raw water supply stream through a desalination device to remove minerals and other impurities from the raw water supply and produce demineralized water (sometimes called DMW). The desalination device generally comprises one or more ion exchange columns and removes impurities by ion exchange. However, other methods of removing ions are also conceivable. In one embodiment of the water treatment system according to the present invention, the system further comprises a desalination device (11) in fluid communication with the stripper (21) upstream of the stripper (21).

[0039] Process control device In one embodiment of the water treatment system according to the present invention, the system further comprises a process control device for controlling the operation of the water treatment system. In order for the system to operate with good results, it is preferable that the system includes means for controlling various flows, pressures and temperatures within the system. The process control device can also include a computer program for acquiring the operating parameters of the water treatment system, comparing them with preset values, and adjusting the actual settings according to the computer program.

[0040] Method Disclosed herein is the method of water treatment as defined above.

[0041] In one embodiment of the method of water treatment according to the present invention, the operating pressure within the composite vessel is in the range of 0.7 to 10 bar abs, for example 0.9 to 8, or 1 to 7 bar abs.

[0042] In one embodiment of the method of water treatment according to the present invention, in one embodiment of the water treatment system according to the present invention, the oxygen-depleted drying process vapor is then subjected to a subsequent devaporation step.

[0043] In one embodiment of the method of water treatment according to the present invention, additional oxygen-depleted vapor from an external source is added to the liquid portion of the liquid-vapor mixture within the composite vessel. If the additional oxygen-depleted vapor from the external source is of high purity, it can be added directly into the composite vessel. If not, it can be indirectly heated by passing through a heating coil.

[0044] Use of water treatment system In one embodiment, the water treatment system according to the present invention is used in a plant that uses steam as a feed.

[0045] In one embodiment, a method for producing hydrogen is provided that includes: Producing oxygen-depleted drying process vapor according to the present invention; Supply oxygen-deficient dry process steam to a solid oxide electrolysis cell, perform high-temperature electrolysis in the cell, and generate a hydrogen-rich product gas.

[0046] In addition to oxygen-deficient dry process steam, a feed containing carbon dioxide and / or carbon monoxide can be supplied to the solid oxide electrolysis cell for high-temperature electrolysis.

[0047] In Figure 1, raw water stream (1) is desalted by an ion exchanger (11) to obtain demineralized water (12) with a very low mineral content. The demineralized water may be abbreviated as DMW. The demineralized water may still contain oxygen and is sent to a vertically arranged stripper (21) including a packed bed, where oxygen is removed from the water using steam (23). Oxygen and steam are discharged from the upper (27) container, and oxygen-deficient water is discharged from the bottom container below the packed bed (24). The desalted oxygen-deficient water is collected in a composite container (22) arranged horizontally below the packed bed. The desalted oxygen-deficient water collected in the composite container may be called boiler water (BW). The boiler water is circulated (34) to a heat exchanger (32) arranged below the composite container (22), where steam is generated, and a mixture of steam and water is recycled (33) to the composite container (22). The boiler water forms at least a liquid phase covering the bottom of the composite container (22) and the heating surface of the heat exchanger (32). The recycled steam-water mixture is bubbled through the liquid phase in the composite container to separate water from the steam-water mixture and generate a dry steam phase above the liquid phase in the composite container (22). The dry steam is supplied to a demister (36) arranged above the stripper (21) and the composite container (22) (23). The demister reduces the carryover of liquid water droplets into the steam, and the desalted and oxygen-deficient dry steam (35) is recovered from the demister (36), and this dry steam can be used in any process that requires desalted and oxygen-deficient dry steam, such as in an SOEC system.

[0048] To avoid the accumulation of residual salts in the boiler water of the composite container (22), a small flow rate (37) is purged from the liquid phase of the boiler water. This purge is called blowdown.

[0049] The composite vessel (22) is operated at a pressure in the range of 1 to 8 bar abs, and the flow of raw water to the water treatment system (1), the flow of dry oxygen-depleted steam from the water treatment system, and the heat supplied to the heat exchanger are controlled such that the boiler water forms a liquid phase covering at least the bottom of the composite vessel and the heating surface of the heat exchanger.

[0050] In FIG. 2, a water treatment system similar to that of FIG. 1 is shown, except that the demister (36) is arranged in a separate vessel placed on top of the surge vessel.

[0051] In FIG. 3, a water treatment system similar to that of FIG. 2 is shown, except that the steam generated by the external process (41) is supplied to the liquid phase of the boiler water in the composite vessel (22).

[0052] In FIG. 4, a water treatment system similar to that of FIG. 2 is shown, except that a high-temperature process gas such as steam from the external process (42) is passed through the heating coil in the liquid phase of the boiler water in the composite vessel (22), and heat is transferred from the high-temperature process gas to the boiler water by indirect heat transfer.

[0053] In FIG. 5, a water treatment system similar to that of FIG. 2 is shown, except that the purge (37) from the composite vessel (22) is supplied to the external boiler (43), and the generated steam is reused in the liquid phase of the boiler water in the composite vessel (22).

[0054] In Figure 6, a typical prior art water treatment system is shown. The raw water stream (1) is desalted in an ion exchanger (11), and the purified water with a very low mineral content is called demineralized water DMW (12). The desalted water may still contain oxygen and is sent to a stripper (21) equipped with a packed bed, where oxygen is removed from the water using steam (23). The oxygen and steam exit from the upper container, and the desalted water with reduced oxygen exits from the bottom of the stripper (21) under the packed bed (24). Here, the oxygen-deficient desalted water called boiler feed water BFW is collected in a surge vessel (28) under the packed bed. The main purpose of the surge vessel is to accommodate the buffer volume of BFW. Heat is directly applied to the surge vessel by injecting steam from an external source (26) into the surge vessel (28) to keep the BFW at the boiling point in the surge vessel (28) and generate the steam (23) required for the stripper 21. Alternatively, the steam (23) can be applied indirectly by heat exchange with a coil in the surge vessel.

[0055] The stripper (21) with a packed bed is integrated with the surge vessel in this embodiment and may be called a "deaerator". The deaerator operates at a pressure in the range of 1 bar abs to 5 bar abs.

[0056] BFW (25) is pumped from the surge vessel (28) to the boiler. The boiler includes a heat exchanger (32) where steam is generated and a container for separating the steam and water mixture sent from the heat exchanger, which is called a "steam drum" (31). The steam drum (31) is connected to the heat exchanger by a water pipe (34) and a steam / water mixture pipe (33). Alternatively, the steam drum and the heat exchanger can be integrated or a combination of the two options can be used. A demister (36) is arranged at the upper part of the steam drum (31) to reduce the carry-over of water droplets to the steam discharged from the steam drum, and this can be supplied to the consumer.

[0057] To avoid the accumulation of residual salts in the boiler water in the steam drum (31) and the heat exchanger (32), a small flow rate (37) is purged from the liquid phase of the steam drum (31).

[0058] In FIG. 7, a typical prior art water treatment system similar to that of FIG. 6 is shown. Except for the high-temperature process gas such as steam from the external process (42), the liquid phase of the boiler water in the composite vessel (22) is passed through the heating coil, and heat is transferred from the high-temperature process gas to the boiler water by indirect heat transfer.

Example

[0059] Example 1: High-temperature solid oxide electrolysis system by a water treatment system including a composite container An embodiment of the present invention is shown in FIG. 2. The raw water flow (1) of 21.8 m 3 per hour is desalted by an ion exchanger (11) containing acidic and alkaline ion exchange resins. The demineralized water DMW (12) is supplied to a stripper (vertical vessel) containing a packed bed (21) of 25 mm IMTP random packing, and oxygen is removed from the water using the steam (23) supplied below the packed bed. 100 kg / h of oxygen and steam are discharged from the upper part of the stripper (27) from the vessel, and the generated oxygen-deficient water is discharged from the lower part of the packed bed (24) of the vessel. The oxygen-deficient water is collected in a composite vessel (22) under the packed bed. The composite vessel serves to contain a buffer volume of oxygen-deficient water called boiler water. The boiler water is kept at the boiling point in the composite vessel (22) by indirectly supplying heat from a heat exchanger (32) installed below the composite vessel. The colder and heavier water sinks to the bottom of the composite vessel and reaches the heat exchanger through the opening (34). The heat exchanger supplies 11.5 MW of heat to the boiler water. The steam generated in the heat exchanger (32) is sent from the opening (33) to the composite vessel. The composite vessel supplies steam to the bottom of the stripper and serves to remove the liquid water droplets trapped in the steam by a demister (36) arranged at the upper part of the composite vessel. From the demister (35), oxygen-deficient dry process steam is taken out at a rate of 21.5 tons / hour, and 20,000 Nm 3 / h of H2 is generated.

[0060] To avoid the accumulation of residual salts in the composite vessel, a flow rate of 200 kg / h is purged from the liquid phase (37). The oxygen-depleted dry process steam is supplied to an SOEC stack operating at 2 bar g and 750 °C.

[0061] Such a system has the advantage of being able to reduce the construction cost of the system because it can construct a simplified system for producing H2 from steam. Less metal is required for the reactor, and less equipment is needed to control the operation of the system.

Claims

1. A water treatment system for preparing oxygen-deficient dry process steam (35), comprising: - A stripper (21) for removing oxygen from water; - A liquid recovery container for recovering oxygen-deficient liquid water from the stripper; - A fluid separation container for recovering a liquid purified water-steam mixture and separating water from the steam; - A heating device for evaporating liquid water into steam ; wherein the fluid recovery container and the fluid separation container are provided as a composite container (22) for recovering oxygen-deficient liquid water from the stripper (21) and separating water and steam; and the stripper (21) is disposed above the composite container (22) and in direct fluid communication with the composite container (22); and the heating device is disposed to supply steam to the lower part of the composite container (22). The water treatment system.

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

3. The water treatment system according to any one of claims 1 or 2, wherein the heating device includes a heating element disposed inside and at the lower part of the composite container (22).

4. The water treatment system according to any one of claims 1 to 3, wherein the composite container is provided with a process steam outlet disposed at the upper part of the composite container (22).

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

6. The water treatment system according to any one of claims 1 to 5, wherein the composite container (22) is provided with a purge outlet (37) at the lower part of the container.

7. The water treatment system according to any one of claims 1 to 6, wherein the direct fluid communication between the composite container and the stripper provides a fluid recirculation (23, 24) between the composite container (22) and the stripper (21).

8. The water treatment system according to any one of claims 1 to 7, wherein the stripper (21) is provided with a packed bed, baffles and other internal fittings for removing oxygen from the liquid water in the stripper (21).

9. The water treatment system according to any one of claims 1 to 8, wherein the stripper (21) further comprises a liquid water inlet disposed at an upper portion of the stripper.

10. The water treatment system according to any one of claims 1 to 9, wherein the stripper (21) further comprises a vapor outlet disposed at an upper portion of the stripper.

11. The heating device comprises a heat exchanger (32), and the heat exchanger (32) is disposed below the composite container (22) and in direct fluid communication (33, 34) with the composite container (22) for indirectly transferring heat to any fluid flowing into and out of the heat exchanger (32). The water treatment system according to any one of claims 1 to 10.

12. The heating device comprises a heating coil (44) disposed within and at a lower portion of the composite container (22) for indirectly transferring heat to any fluid within the composite container (22). The water treatment system according to any one of claims 1 to 11.

13. Boiler water is circulated (34) to a heat exchanger (32) disposed below the composite container (22), steam is generated in the heat exchanger (32), and a steam-water mixture is recirculated (33) to the composite container (22). The water treatment system according to any one of claims 1 to 12.

14. The water treatment system according to any one of claims 1 to 13, further comprising a desalination device (11) upstream of the stripper (21) and in fluid communication with the stripper (21).

15. The water treatment system according to any one of claims 1 to 14, further comprising a process control device for controlling the operation of the water treatment system.

16. A water treatment method for producing oxygen-depleted dry process steam, comprising: - Passing a desalinated water stream over a packed bed and passing oxygen stripping steam in a countercurrent direction to remove oxygen from the desalinated water stream to produce oxygen-depleted water; - Collecting the oxygen-depleted water in a composite container to obtain an oxygen-depleted water-steam mixture within the composite container; - Indirectly heating a liquid portion of the water-steam mixture to generate wet steam; - Bubbling the wet steam through the liquid portion of the water-steam mixture to remove water droplets from the wet steam to produce dry steam; Including - The oxygen-deficient water-steam mixture in the composite vessel supplies the oxygen-stripping steam to the stripper, buffers fluctuations in the desalinated water flow per unit of dry steam produced, absorbs the pressure difference between the upstream and downstream of the composite vessel, and removes water droplets from the wet steam. The method.

17. The method according to claim 16, wherein the operating pressure in the composite vessel is in the range of 0.7 to 10 bar abs, for example, 0.9 to 8, or 1 to 7 bar abs.

18. The method according to any one of claims 16 to 17, wherein the oxygen-deficient dry process steam is then exposed to a step of devaporization.

19. The method according to any one of claims 16 to 18, wherein oxygen-deficient steam from an external source is added to the liquid portion of the water-steam mixture in the composite vessel.

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

21. - Producing oxygen-deficient dry process steam according to any one of claims 16 to 19; - Supplying the oxygen-deficient dry process steam to a solid oxide electrolysis cell and performing high-temperature electrolysis in the cell to produce a hydrogen-rich product gas; A method for producing hydrogen, comprising the above steps.

22. The method according to claim 21, wherein, in addition to the oxygen-deficient dry process steam, a feed containing carbon dioxide and / or carbon monoxide is supplied to the solid oxide electrolysis cell performing the high-temperature electrolysis.

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