A water treatment system for a PEM electrolyser

Abstract

This utility model relates to the field of hydrogen production by water electrolysis, and discloses a water treatment system for a PEM electrolyzer, comprising: a first buffer tank, an electro-desalination EDI unit, a polishing resin tank, a second buffer tank, and a concentrate treatment unit; the first buffer tank, the electro-desalination EDI unit, and the polishing resin tank are connected in sequence; the second buffer tank is connected to the concentrate output terminal of the EDI unit and is connected to the first buffer tank through the concentrate treatment unit; the hydrogen-side drainage from the PEM electrolyzer and the concentrate output from the EDI unit enter the second buffer tank, and after treatment by the concentrate treatment unit, enter the first buffer tank; the oxygen-side drainage from the PEM electrolyzer and the fresh makeup water enter the first buffer tank, and the water in the first buffer tank is treated sequentially by the EDI unit and the polishing resin tank to obtain pure water for supplying the PEM electrolyzer. This system can solve the problems of easy saturation of polishing resin and high system operating costs in existing PEM electrolysis hydrogen production systems when directly treating trace ions and particulate matter impurities in the electrolytic internal circulation water with polishing resin.

Description

Technical Field

[0001] This utility model relates to the field of hydrogen production by water electrolysis, and in particular to a water treatment system for a PEM electrolyzer. Background Technology

[0002] In PEM (proton exchange membrane) water electrolysis hydrogen production systems, the accompanying pure water treatment system has a crucial impact on the stability and efficiency of the electrolysis process. As one of the mainstream technologies for green hydrogen production, PEM water electrolysis has strict requirements on the quality of the water entering the electrolyzer. During actual operation, the water quality may deteriorate due to factors such as metal component corrosion, particulate matter shedding, or impurities introduced by the makeup water, leading to increased concentrations of trace ions and accumulation of solid particles in the circulating water. To maintain the high performance and long-term stability of the electrolyzer, continuous purification of the circulating water is essential.

[0003] In existing technologies, ion exchange resins (such as polishing resins) are commonly used to treat circulating water and makeup water to remove impurities such as cations, anions, and suspended particles. However, this treatment method has significant drawbacks: impurity ions in the water can quickly saturate the resin, reducing its exchange capacity and requiring frequent replacement or regeneration; furthermore, polishing resins are expensive and become hazardous waste after failure, making the treatment process complex and costly. In practical engineering applications, the internal circulation system of electrolyzed water maintains stable water quality through hydrogen-side water discharge. However, because this water is of poor quality, it is entirely discharged into the wastewater system, resulting in high water consumption and loss of pressure energy carried by the water during discharge. This significantly increases the operating cost of the entire water treatment system, hindering the large-scale promotion and application of PEM water electrolysis technology. Utility Model Content

[0004] The purpose of this invention is to provide a water treatment system for a PEM electrolyzer, which solves the problems of easy saturation of polishing resin and high system operating costs when the existing PEM electrolysis hydrogen production system directly treats trace ions and particulate matter impurities in the electrolytic internal circulation water through polishing resin.

[0005] To solve the above-mentioned technical problems, the present invention provides a water treatment system for a PEM electrolyzer, comprising: a first buffer tank, an electro-desalination EDI unit, a polishing resin tank, a second buffer tank, and a concentrate treatment unit; the first buffer tank, the electro-desalination EDI unit, and the polishing resin tank are connected in sequence; the second buffer tank is connected to the concentrate output terminal of the EDI unit and is connected to the first buffer tank through the concentrate treatment unit; the hydrogen-side drainage from the PEM electrolyzer and the concentrate output from the EDI unit enter the second buffer tank, and after being treated by the concentrate treatment unit, enter the first buffer tank; the oxygen-side drainage from the PEM electrolyzer and the fresh makeup water enter the first buffer tank, and the water in the first buffer tank is sequentially treated by the EDI unit and the polishing resin tank to obtain pure water for supplying the PEM electrolyzer.

[0006] In this embodiment of the invention, the concentrate treatment unit includes a reverse osmosis unit and a neutralization tank. The water in the second buffer tank is processed sequentially by the neutralization tank and the reverse osmosis unit before entering the first buffer tank.

[0007] In this embodiment of the present invention, the water treatment system further includes an intermediate water tank and a first pressure boosting pump. The intermediate water tank is connected to the EDI unit and is connected to the polishing resin tank through the first pressure boosting pump. The water in the first buffer tank enters the intermediate water tank after being treated by the EDI unit, and the water in the intermediate water tank enters the polishing resin tank after being pressurized by the first pressure boosting pump.

[0008] In this embodiment of the invention, the intermediate water tank is also connected to the drain outlet of the oxygen-side drainage, wherein a portion of the oxygen-side drainage enters the first buffer tank and another portion enters the intermediate water tank.

[0009] In this embodiment of the invention, the water treatment system further includes a filter; the filter is respectively installed on the water inlet pipe of the EDI unit, the water inlet pipe of the polishing resin tank, and the water outlet pipe of the polishing resin tank, and the filter is used to intercept particulate impurities.

[0010] In this embodiment of the invention, the water treatment system further includes an oxygen-side circulating water branch and a hydrogen-side circulating water branch. The oxygen-side circulating water branch is equipped with a first energy recovery device, which depressurizes the high-pressure oxygen-side drainage output from the PEM electrolyzer and discharges it into a first buffer tank, and pressurizes the pure water at atmospheric pressure and sends it back to the PEM electrolyzer, thus transferring the pressure of the oxygen-side drainage to the pure water. The hydrogen-side circulating water branch is equipped with a second energy recovery device, which depressurizes the high-pressure hydrogen-side drainage output from the PEM electrolyzer and discharges it into a second buffer tank, and pressurizes the pure water at atmospheric pressure and sends it back to the PEM electrolyzer, thus transferring the pressure of the hydrogen-side drainage to the pure water.

[0011] In this embodiment of the invention, the first energy recovery unit and the second energy recovery unit send the pure water back to the PEM electrolyzer through the same return path. A pressure boosting pump is provided on the return path to pressurize the pure water to meet the working requirements of the PEM electrolyzer.

[0012] In this embodiment of the present invention, the oxygen-side circulating water branch further includes a gas-liquid separator. The gas-liquid separator is used to separate the gas-water mixture output from the oxygen side of the PEM electrolyzer, and to divide the separated aqueous phase into two water streams. One water stream is output as oxygen-side drainage to the first energy recovery unit, and the other water stream is returned to the PEM electrolyzer as oxygen-side return water.

[0013] In this embodiment of the invention, the gas-liquid separator is equipped with a water flow regulating valve to control the ratio of oxygen-side drainage to oxygen-side return water.

[0014] In this embodiment of the invention, the water treatment system further includes one or more water quality detectors, which are installed on the water flow path to monitor and report water quality data.

[0015] Compared with the prior art, the above embodiments of this utility model can have at least one or more of the following beneficial effects: By sequentially connecting a first buffer tank, an electro-deionization (EDI) unit, and a polishing resin tank, pure water is obtained from the oxygen-side drainage and fresh makeup water of the PEM electrolyzer to supply the PEM electrolyzer. A second buffer tank is connected to the concentrate output of the EDI unit, and a concentrate treatment unit is connected to the second buffer tank. The hydrogen-side drainage and concentrate output from the EDI unit are treated and mixed with the oxygen-side drainage and fresh makeup water. Thus, during the PEM electrolysis hydrogen production process, ionic and particulate impurities in the circulating water are removed through a low-cost EDI unit and concentrate treatment unit, avoiding damage to the polishing resin tank for subsequent fine treatment, extending equipment life, and reducing water treatment costs. Attached Figure Description

[0016] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0017] Figure 1 This is a schematic diagram of the structure of a PEM electrolyzer water treatment system provided in an embodiment of this utility model. Detailed Implementation

[0018] Proton exchange membrane (PEM) water electrolysis is an advanced process for producing high-purity hydrogen using pure water electrolysis. Its core principle involves using a proton exchange membrane as a solid electrolyte to decompose water molecules into hydrogen and oxygen under direct current. Compared to traditional alkaline electrolysis, PEM electrolysis offers advantages such as high efficiency, high hydrogen purity (>99.99%), fast dynamic response, and compact size. It is particularly suitable for coupling with renewable energy sources (such as wind and solar power) and is one of the key technologies for green hydrogen industrial production. However, PEM electrolyzers have stringent environmental requirements, especially the quality of the circulating water inside the electrolyzer, which directly affects electrolysis efficiency, membrane electrode lifespan, and system stability.

[0019] During the operation of the PEM electrolysis system, the conductivity of the makeup water must be below 0.1 μS / cm. Electrolyzed water (demineralized water) continuously flows inside the electrolyzer via a circulation pump to maintain the humidity balance required for proton conduction and to remove the gases generated in the reaction and the heat produced by electrolysis. However, with prolonged operation, the quality of the circulating water gradually deteriorates, and trace metal ions (such as Fe) become present. 3+ Ni 2+ Impurities can leach from bipolar plates or pipeline corrosion, leading to decreased ion conductivity of the membrane electrode assembly (MEA) and the generation of reactive oxygen species during water decomposition, accelerating the chemical degradation of the MEA and producing organic debris. Deteriorating water quality significantly reduces electrolysis efficiency, accelerates MEA aging, and can even cause localized hot spots leading to membrane perforation. Therefore, continuous treatment of electrolyzed water through a circulating water purification system is necessary to remove impurities, dissolved gases, and ionic contaminants. However, using polishing resin tanks or other methods to directly contact the electrolyzed water for impurity removal easily damages and discards the polishing resin, resulting in high water treatment costs. Therefore, a low-cost system architecture for removing impurities from PEM electrolyzed water needs to be designed.

[0020] To make the objectives, technical solutions, and advantages of this utility model clearer, the various embodiments of this utility model will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the various embodiments of this utility model to facilitate a better understanding of this application. However, the technical solutions claimed in the claims of this utility model can be implemented even without these technical details and with various variations and modifications based on the following embodiments.

[0021] like Figure 1 As shown, this utility model embodiment relates to a water treatment system for a PEM electrolyzer, comprising: a first buffer tank (i.e., buffer tank 1), an electro-desalination EDI unit, a polishing resin tank, a second buffer tank (i.e., buffer tank 2), and a concentrate treatment unit. The first buffer tank, the electro-desalination EDI unit, and the polishing resin tank are connected in sequence. The second buffer tank is connected to the concentrate output terminal of the EDI unit and is connected to the first buffer tank through the concentrate treatment unit. The hydrogen-side drainage from the PEM electrolyzer and the concentrate output from the EDI unit enter the second buffer tank, and after being treated by the concentrate treatment unit, they enter the first buffer tank. The oxygen-side drainage from the PEM electrolyzer and the fresh makeup water enter the first buffer tank, and the water in the first buffer tank is treated sequentially by the EDI unit and the polishing resin tank to obtain pure water for supplying the PEM electrolyzer.

[0022] Compared to traditional PEM electrolysis hydrogen production systems that directly treat trace ions, particulate matter, and other impurities in circulating water through polishing resin, the water treatment system for the PEM electrolyzer proposed in this embodiment uses an electro-desalination (EDI) unit and a polishing resin tank to treat the oxygen-side drainage and fresh makeup water from the PEM electrolyzer to obtain pure water for supplying the PEM electrolyzer. A concentrate treatment unit treats the hydrogen-side drainage and the concentrate output from the EDI unit, mixing them with the oxygen-side drainage and fresh makeup water. This allows for the removal of ionic and particulate impurities from the circulating water during PEM electrolysis hydrogen production through a low-cost EDI unit and concentrate treatment unit, preventing damage to the polishing resin tank during subsequent fine treatment, extending equipment lifespan, and reducing water treatment costs.

[0023] The following is a detailed description of the implementation details of the water treatment system of the PEM electrolyzer according to an embodiment of this utility model. The following content is only for the convenience of understanding and is not necessary for implementing this solution.

[0024] In one embodiment of this utility model, the concentrate treatment unit includes a reverse osmosis unit, which is used to perform high-precision filtration on the concentrate discharged from the EDI unit and the hydrogen side loop to remove most of the dissolved salts, heavy metals, bacteria, viruses, organic matter, etc. in the water.

[0025] In one embodiment of this invention, the concentrated water treatment unit further includes a neutralization tank. Water in the second buffer tank is treated sequentially by the neutralization tank and the reverse osmosis unit before entering the first buffer tank. Specifically, the neutralization tank adjusts the pH value of the effluent from the second buffer tank to a preset range, completing pretreatment before entering the reverse osmosis unit. This avoids acidic hydrolysis damaging the membrane of the reverse osmosis unit, or alkaline water causing scaling and membrane blockage, as well as the risk of amplified residual chlorine.

[0026] In one embodiment of this utility model, the water treatment system further includes an intermediate water tank and a first pressure boosting pump. The intermediate water tank is connected to the EDI unit and is connected to the polishing resin tank via the first pressure boosting pump. Water in the first buffer tank is processed by the EDI unit and then stored in the intermediate water tank. Water in the intermediate water tank is pressurized by the first pressure boosting pump and then enters the polishing resin tank for fine treatment to remove any remaining trace particles, thus obtaining pure water that meets the required quality standards.

[0027] In one embodiment of this invention, the intermediate water tank is also connected to the outlet of the oxygen-side drainage. A portion of the oxygen-side drainage enters the first buffer tank, and the other portion enters the intermediate water tank. The intermediate water tank is used to collect the EDI unit's permeate water and a portion of the oxygen-side drainage. The ratio of the two entering the intermediate water tank can be determined based on the water quality; better water quality indicates a better ratio entering the intermediate water tank.

[0028] In one embodiment of the present invention, the water treatment system further includes filters, and the filters are respectively installed on the water inlet pipe of the EDI unit, the water inlet pipe of the polishing resin tank and the water outlet pipe of the polishing resin tank. The filters are used to intercept particulate impurities.

[0029] In one embodiment of this invention, the water treatment system further includes an oxygen-side circulating water branch and a hydrogen-side circulating water branch. The oxygen-side circulating water branch is equipped with a first energy recovery unit. This unit depressurizes the high-pressure oxygen-side wastewater output from the PEM electrolyzer and discharges it into a first buffer tank, while pressurizing the pure water at atmospheric pressure and returning it to the PEM electrolyzer. The pressure energy of the oxygen-side wastewater is transferred to the pure water. The hydrogen-side circulating water branch is equipped with a second energy recovery unit. This unit depressurizes the high-pressure hydrogen-side wastewater output from the PEM electrolyzer and discharges it into a second buffer tank, while pressurizing the pure water at atmospheric pressure and returning it to the PEM electrolyzer. The pressure energy of the hydrogen-side wastewater is transferred to the pure water. In this way, by recovering the mechanical energy carried by the circulating water through the energy recovery unit, the system's energy consumption is effectively reduced.

[0030] In one embodiment of this utility model, the first energy recovery unit and the second energy recovery unit send pure water back to the PEM electrolyzer through the same return path. A pressure boosting pump is provided on the return path to pressurize the pure water to meet the working requirements of the PEM electrolyzer.

[0031] In one embodiment of this invention, the oxygen-side circulating water branch further includes a gas-liquid separator (i.e., an oxygen separator). The gas-liquid separator separates the gas-water mixture output from the oxygen side of the PEM electrolyzer. The gaseous portion is vented after passing through a demister, and the separated aqueous phase is divided into two streams. One stream is output as oxygen-side drainage to the first energy recovery unit (i.e., energy recovery unit 1), and the other stream is returned to the PEM electrolyzer as oxygen-side return water. This reduces circulating water discharge and pure water input consumption. A heat exchanger is also installed between the oxygen separator and energy recovery unit 1 on the oxygen-side drainage path to cool the high-pressure drainage.

[0032] In one embodiment of this invention, the hydrogen-side circulation loop includes a hydrogen separator and a hydrogen-side drainage path. A heat exchanger and an energy recovery unit 2 are sequentially arranged on the hydrogen-side drainage path. The hydrogen separator is used to separate the gas-water mixture output from the hydrogen side of the PEM electrolyzer, and the separated aqueous phase is used as high-pressure drainage from the hydrogen side. After being cooled by the heat exchanger, it is discharged through the hydrogen-side drainage path. A flash tank is also provided between the heat exchanger and the energy recovery unit 2 on the hydrogen-side drainage path to reduce the pressure of the hydrogen-side drainage and further separate the hydrogen gas within it.

[0033] In one embodiment of this invention, the gas-liquid separator is equipped with a water flow regulating valve to control the ratio of oxygen-side drainage and oxygen-side return water. In this way, the water flow ratio of oxygen-side drainage and oxygen-side return water can be dynamically adjusted via the water flow regulating valve to control the number of water circulation cycles, the inflow of makeup water, and the outflow of wastewater.

[0034] In one embodiment of this utility model, the water treatment system further includes one or more water quality detectors, which are installed on the water flow path to monitor and report water quality data so as to adjust the water flow ratio of the oxygen-side drainage and oxygen-side return water in real time according to the water quality data.

[0035] It should be noted that the examples mentioned in the above embodiments of this utility model can be freely combined, and any combination can be understood as an embodiment. The terms "embodiment" or "example" appearing in various locations in the specification do not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand that the embodiments described herein can be combined with other embodiments.

[0036] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention and are not intended to limit the present invention. In practical applications, various changes, equivalent substitutions and improvements can be made to them in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A water treatment system using a PEM electrolyzer, characterized in that, include: First buffer tank, EDI unit for electro-deionization, polishing resin tank, second buffer tank, concentrated water treatment unit; The first buffer tank, the electro-deionization EDI unit, and the polishing resin tank are connected in sequence; the second buffer tank is connected to the concentrate output terminal of the EDI unit and is connected to the first buffer tank through the concentrate treatment unit. The hydrogen-side drainage from the PEM electrolyzer and the concentrated water output from the EDI unit enter the second buffer tank, and after being treated by the concentrated water treatment unit, they enter the first buffer tank. The oxygen-side drainage and fresh makeup water from the PEM electrolyzer enter the first buffer tank. The water in the first buffer tank is then processed sequentially through the EDI unit and the polishing resin tank to obtain pure water for supplying the PEM electrolyzer.

2. The water treatment system of the PEM electrolyzer according to claim 1, characterized in that, The concentrate treatment unit includes a reverse osmosis unit and a neutralization tank. The water in the second buffer tank is processed sequentially through the neutralization tank and the reverse osmosis unit before entering the first buffer tank.

3. The water treatment system of the PEM electrolyzer according to claim 1 or 2, characterized in that, The water treatment system also includes an intermediate water tank and a first pressure boosting pump. The intermediate water tank is connected to the EDI unit and is connected to the polishing resin tank through the first pressure boosting pump. The water in the first buffer tank is processed by the EDI unit and then enters the intermediate water tank. The water in the intermediate water tank is pressurized by the first pressure boosting pump and then enters the polishing resin tank.

4. The water treatment system of the PEM electrolyzer according to claim 3, wherein the intermediate water tank is further connected to the drain outlet of the oxygen-side drainage, wherein, A portion of the oxygen-side drainage enters the first buffer tank, and the other portion enters the intermediate water tank.

5. The water treatment system of the PEM electrolyzer according to any one of claims 1 to 3, characterized in that, The water treatment system also includes a filter; The EDI unit's inlet pipe, the polishing resin tank's inlet pipe, and the polishing resin tank's outlet pipe are each equipped with a filter, which is used to trap particulate impurities.

6. The water treatment system of the PEM electrolyzer according to any one of claims 1 to 3, characterized in that, The water treatment system also includes an oxygen-side circulating water branch and a hydrogen-side circulating water branch; The oxygen-side circulating water branch is equipped with a first energy recovery device. The first energy recovery device is used to depressurize the oxygen-side drainage under high pressure output from the PEM electrolyzer and discharge it into the first buffer tank, and to pressurize the pure water under normal pressure and send it back to the PEM electrolyzer. The pressure of the oxygen-side drainage can be transferred to the pure water. The hydrogen-side circulating water branch is equipped with a second energy recovery device. The second energy recovery device depressurizes the hydrogen-side drainage output from the PEM electrolyzer at high pressure and discharges it into the second buffer tank. It also pressurizes the pure water at normal pressure and sends it back to the PEM electrolyzer. The pressure of the hydrogen-side drainage can be transferred to the pure water.

7. The water treatment system of the PEM electrolyzer according to claim 6, characterized in that, The first energy recovery unit and the second energy recovery unit send the pure water back to the PEM electrolyzer through the same return path. A second pressure boosting pump is provided on the return path to pressurize the pure water to meet the working requirements of the PEM electrolyzer.

8. The water treatment system of the PEM electrolyzer according to claim 6, characterized in that, The oxygen-side circulating water branch also includes a gas-liquid separator, which is used to separate the gas-water mixture output from the oxygen side of the PEM electrolyzer. The separated aqueous phase is divided into two water streams, one of which is output as oxygen-side drainage to the first energy recovery unit, and the other is returned to the PEM electrolyzer as oxygen-side return water.

9. The water treatment system of the PEM electrolyzer according to claim 8, characterized in that, The gas-liquid separator is equipped with a water flow regulating valve to control the ratio of oxygen-side drainage to oxygen-side return water.

10. The water treatment system of the PEM electrolyzer according to claim 1, characterized in that, The water treatment system also includes one or more water quality detectors, which are installed along the water flow path to monitor and report water quality data.

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