Search

EP-4739818-A1 - WATER RECIRCULATION LOOP FOR A HYDROGEN PRODUCING ELECTROLYSIS PLANT

EP4739818A1EP 4739818 A1EP4739818 A1EP 4739818A1EP-4739818-A1

Abstract

The invention relates to a water recirculation loop (30) for a hydrogen producing electrolysis plant (30) that comprises an electrolysis stack (10). The water recirculation loop (30) comprises: at least one, preferably one, circulation pump (6); a water inlet section (9) connectable to the electrolysis stack (10), wherein the water inlet section (9) can be supplied with water by the pump (6); a water feed section (91) leading to the water inlet section (9);a water outlet section (11) connectable to the electrolysis stack (10), wherein the water at the outlet section (11) being pressurized within the electrolysis stack (10) and/or in the water feed section (91) leading to the water inlet section (9); at least one energy recovery device (8) for transferring water pressure and/or flow energy from the water outlet section (11) to said water feed section (91); and a recirculating section (31) connecting an output of the energy recovery device (8, 28) with an input port of the pump (6).

Inventors

  • TÆKKER MADSEN, Henrik
  • ØRSTED, Peter
  • ELKJÆR LAUSTSEN, Michael
  • ARORA, ARUN

Assignees

  • Grundfos Holding A/S

Dates

Publication Date
20260513
Application Date
20240916

Claims (20)

  1. 1. A water recirculation loop (30) for a hydrogen producing electrolysis plant (30) that comprises an electrolysis stack (10) , the water recirculation loop (30) comprising: at least one, preferably one, circulation pump (6) , a water inlet section (9) connectable to the electrolysis stack (10) , wherein the water inlet section (9) can be supplied with water by the pump (6) , a water feed section (91) leading to the water inlet section (9) , a water outlet section (11) connectable to the electrolysis stack (10) , wherein the water at the outlet section (11) being pressurized within the electrolysis stack (10) and/or in the water feed section (91) leading to the water inlet section (9) , at least one energy recovery device (8, 28) for transferring water pressure and/or flow energy from the water outlet section (11) to said water feed section (91) , and a recirculating section (31) connecting an output of the energy recovery device (8, 28) with an input port of the pump (6) .
  2. 2. The loop (30) of claim 1, wherein the water flow rate at the outlet section (11) is at least 85%, preferably at least 90%, more preferred at least 95% or even 98% of the water flow rate at the water inlet section (9) .
  3. 3. The loop (30) of any of the preceding claims, wherein the water pressure at the water outlet section (11) is at least 30 bar, preferably at least 50 bar, more preferred at least 70 bar or even 100 bar.
  4. 4. The loop (30) of any of the preceding claims, wherein the water flow rate downstream the pump (6) is at least 20m 3 /hour per MW electrolysis, preferably at least 100m 3 /hour per MW electrolysis, more preferred more than 200m 3 /hour per MW electrolysis .
  5. 5. The loop (30) of any of the preceding claims, wherein the pump (6) is designed to not leak substances detrimental to a proton exchange membrane (PEM) electrolysis stack (10) , such as substances detrimental to a proton transfer membrane, and/or wherein the energy recovery device (8, 28) is designed to not leak electrode detrimental substances detrimental to a proton exchange membrane (PEM) electrolysis stack, wherein the detrimental substances are preferably one, more or all of: metal cations, CO2, organics.
  6. 6. The loop (30) of any of the preceding claims, wherein the pump (6) is designed to not leak substances detrimental to an alkaline electrolysis (AEL) stack, wherein the detrimental substances preferably are one, more or all of: multivalent cations, chloride, CO2, organics.
  7. 7. The loop (30) of any of the preceding claims, wherein the pump (6) is designed such that water pumped by the pump (6) can have ASTM Type I quality at both an upstream side and a downstream side of the pump (6) and/or to leak only substances that are not detrimental to ASTM Type I quality of water .
  8. 8. The loop (30) of any of the preceding claims, wherein the energy recovery device (8, 28) is designed to not leak substances detrimental to an electrolysis stack (10) , such as substances detrimental to an electrode, a separator between electrodes, or a filter such as a lye filter, and/or wherein the energy recovery device (8, 28) is designed such that water traversing the energy recovery device (8, 28) can have ASTM Type I quality at both an upstream side and a downstream side of the energy recovery device (8, 28) and/or to leak only substances that are not detrimental to ASTM Type I quality of water .
  9. 9. The loop (30) of any of the preceding claims, which is void of a pressure control valve, such as a pressure relief valve, downstream the water outlet section (11) , and/or which is void of turbines downstream the water outlet section (11) •
  10. 10. The loop (30) of any of the preceding claims, wherein a number of parallelly arranged energy recovery devices is higher than the number of pumps.
  11. 11. The loop (30) of any of the preceding claims, comprising a further pump (61) , wherein, preferably, the water inlet section (9) and/or the water feed section (91) comprises the further pump (61) .
  12. 12. The loop (30) of any of the preceding claims, wherein the energy recovery device (8, 28) comprises a pressure exchange unit (8) and/or a turbo charger (28) .
  13. 13. The loop (30) of any of the preceding claims, comprising a high pressure pump (62) .
  14. 14. The loop (30) of claim 13, comprising a further water inlet section (63) connectable to the electrolysis stack (10) , wherein the further water inlet section (63) can be supplied with water by the pump (6) and is arranged to bypass the energy recovery device (8, 28) , and wherein the further water inlet section (63) comprises said high pressure pump ( 62 ) .
  15. 15. The loop (30) of any of the preceding claims, comprising an air lift pump (70) preferably in its water feed section ( 91 ) .
  16. 16. The loop (30) of claim 15, wherein the air lift pump (70) comprises a gas supply port connectable to an oxygen output (81) configured to discharge oxygen formed in the electrolysis stack (10) .
  17. 17. The loop (30) of any of claims 15 to 16, wherein the air lift pump (70) comprises a water supply port connectable to a further water outlet section (16) configured to discharge water drained from the electrolysis stack (10) and preferably separated, by a hydrogen separator (14) , from hydrogen .
  18. 18. The loop (30) of any of the preceding claims, comprising an oxygen separator (80) connectable to the electrolysis stack (10) , wherein the oxygen separator (80) preferably comprises an oxygen output (81) configured to discharge oxygen formed in the electrolysis stack (10) , furthermore preferably comprising a pressure relief valve (90) connected to the oxygen separator (80) .
  19. 19. The loop (30) of claim 18, wherein the gas supply port of the air lift pump (70) is connected to the oxygen output (81) .
  20. 20. The loop (30) of any of claims 18 to 19, wherein the oxygen separator (80) comprises a water output (82) configured to discharge water drained from the electrolysis stack (10) , wherein the water output (82) is connected to the water outlet section (11) .

Description

WATER RECIRCULATION LOOP FOR A HYDROGEN PRODUCING ELECTROLYSIS PLANT TECHNICAL FIELD OF THE INVENTION The invention relates to a water recirculation loop for a hydrogen producing electrolysis plant. BACKGROUND OF THE INVENTION In the electrolysis of water, an electrolysis stack is used to split (ultrapure) water into oxygen and hydrogen gas by electrolysis. The hydrogen gas can then be used as hydrogen fuel. The electrolysis stack may be powered by renewable electricity. There are two commercial electrolyser technologies, alkaline and proton exchange membrane (PEM) , as well as two developmental electrolyser technologies, solid oxide electrolyzer cell (SOEC) and anion exchange membrane (AEM) . For alkaline, PEM and AEM the water is liquid when it undergoes electrolysis, while it is steam for SOEC. During the process huge amounts of heat are generated (200-250 kW per MW electrolyser rating) . To avoid a large temperature increase across the electrolysis (electrolyser) stack, a large flow rate is used, such as 50-100 m3/h per MW. The water is pumped to the electrolysis stack and then to a heat exchanger for cooling before being returned to the electrolysis stack. In the case of PEM and AEM there may be a side stream loop in which an ion exchange polisher is placed. This polisher ensures that the water is continuously kept clean, so as to maintain the expected life time of the electrolysis stack. Without this, lifetime would fall, ruining the efficiency of the hydrogen plant, which is not economic. After being produced, the hydrogen is compressed in a compressor. To better handle fluctuating power inputs (such as from wind and solar) and to save costs, the hydrogen production plant may operate with the electrolysis process under pressure. This allows the hydrogen to be produced with a high pressure, which will eliminate or minimize the need for a compressor. However, this requires that the circulation pump and the rest of the process equipment, including the polisher, must be able to handle and withstand the high pressure. Designing the components (pump, polisher, etc. ) to operate under such a high pressure (e.g. >40 bar) is complex. In particular, providing components dedicated to the higher pressure ratings is expensive and difficult. Thus, it is an objective to simplify the production of hydrogen. SUMMARY OF THE INVENTION The object of the present invention is achieved by the solution provided in the enclosed independent claims . Advantageous implementations of the present invention are further defined in the dependent claims . According to a first aspect, the invention relates to a water recirculation loop for a hydrogen producing electrolysis plant that comprises an electrolysis stack, wherein the water recirculation loop comprises: at least one, preferably one, circulation pump; a water inlet section connectable to the electrolysis stack, wherein the water inlet section can be supplied with water by the pump; a water feed section leading to the water inlet section; a water outlet section connectable to the electrolysis stack, wherein the water at the outlet section being pressurized within the electrolysis stack and/or in the water feed section leading to the water inlet section; at least one energy recovery device (such as e.g. a pressure exchange unit) for transferring water pressure and/or flow energy from the water outlet section to said water feed section; and a recirculating section connecting an output of the energy recovery device with an input port of the pump. This achieves the advantage that the energy recovery device is placed to isolate certain parts, such as with respect to high pressure and/or high flow energy. Thus, by the water recirculation loop, the benefits of a high pressure and/or flow configuration and of a low pressure and/or flow configuration may be combined with one another. For example, the high pressure configuration allows for a lower need for compression, while the low pressure configuration allows the use of parts that do not require to withstand a high pressure. Thereby, in particular simpler (such as less durable, less rigid, less complex and/or cheaper) components can be used and/or a pressure and/or flow rate can be increased while retaining at least parts of the system designed for lower pressures and/or lower flow rates, such as a pump and/or a device for polishing water. Thus, hydrogen production can be simplified. In the context of the present invention, "water" is to be understood as also encompassing alkaline or acidic solutions. For example, "water" in the context of the present invention may include water (H2O) with 30wt% or more of an alkaline substance, such as potassium hydroxide (KOH) . In an embodiment, the water flow rate at the outlet section is at least 85%, preferably at least 90%, more preferred at least 95% or even 98% of the water flow rate at the water inlet section. In an embodiment, the water pressure at the water outlet section is at leas