Structure and method for improving hydrogen production by alkaline electrolyzed water

Abstract

The invention discloses a structure for improving hydrogen production by alkaline electrolysis of water. The section of an electrode plate is of an oval structure, electric heating wires are evenly distributed in the electrode plate in the full-length direction of the electrode plate, and propeller blades for driving electrolyte to be in a turbulent flow state are further arranged on the inner bottom face, located at the bottom of the electrode plate, of an electrolytic bath. The electrode plate of the elliptical structure is adopted, the contact area between the electrode and the catalyst on the surface of the electrode and alkaline water is increased, the area is increased, full contact with liquid is facilitated, and bubble separation is facilitated. The thin electric heating wire is arranged in the electrode, so that the effect of forming relative high temperature on the catalyst layer on the surface of the electrode to promote the electrolytic efficiency is realized, and alkali liquor and bubbles generated on the surface of the electrode are quickly discharged. The propeller blade structure promotes alkali liquor to form a turbulent flow state, heat exchange is improved, alkali liquor flowing is promoted, generated bubbles are promoted to be rapidly separated, the contact time of an electrode and liquid is prolonged, the hydrogen production efficiency and yield are overall improved, and energy consumption is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial hydrogen production, and in particular to a structure and method for improving hydrogen production by alkaline water electrolysis. Background Art

[0002] Industrial hydrogen production is a technology that uses non-hydride energy to produce hydrogen for use in industry through physical, chemical or biological reactions. It includes optimizing fossil fuel hydrogen production, industrial byproduct hydrogen production, water electrolysis hydrogen production, methanol and other hydrogen production methods. Water electrolysis hydrogen production has no pollution emissions, high energy conversion rate, good flexibility and wide applicability, and is widely used in the field of industrial hydrogen production.

[0003] At present, the efficiency of hydrogen production in water electrolysis plants has the potential to be improved, but it is difficult. For example, the volume of 1 mol of hydrogen atom is 11.2L, and the charge is 96500C / mol; the charge of 1Nm3 hydrogen = 96500 / 11.2*1000 = 8616071C = 2393A·h. Theoretical minimum power consumption:

[0004] W=QU=2393*1.23=2943.4W·h=2.94kWh;

[0005] Thermal neutral power consumption:

[0006] W=QU=2393*1.48=2943.4W·h=3.54kWh.

[0007] At present, LONGi (LONGi Green Energy Technology Co., Ltd.) product data shows that 1 cubic meter of hydrogen produced by electrolyzing water consumes 4.0kWh. Compared with the theoretical 3.54KWh, there is still room for improvement. The main problems that need to be solved in this process are:

[0008] 1) The bubbles of hydrogen and oxygen generated on the electrode prevent the electrode from contacting with water.

[0009] As the instruction manual Figure 1 As shown, there is a catalyst coating on the electrode plate. The electrode is activated by the catalyst to achieve electrolytic hydrogen production and oxygen production. In the specific reaction process, the alkaline solution on the surface of the plate produces small bubbles under the action of the catalyst and current, which gradually expand into large bubbles until the buoyancy of the bubbles increases and detaches from the plate and overcomes the rising water pressure to achieve gas-liquid separation. In this process, the electrode contacts the alkaline solution to produce hydrogen, but when the bubbles contact the electrode and multiple bubbles contact each other, it will affect the electrode contact with the alkaline solution, which will reduce the rate and production capacity of electrolysis.

[0010] At present, on the one hand, the bubbles can be gradually enlarged to detach, and on the other hand, the bubbles can be accelerated to detach by vibration or ultrasound. However, these methods require increased energy consumption, and the effect of ultrasound applied outside the electrolytic cell is not high.

[0011] 2) The surface area of ​​the planar electrode substrate is difficult to further increase and the contact area with water is limited

[0012] like Figure 1 As shown in the figure, the planar electrode substrate is a common electrolysis device. The planar characteristics limit the contact area with the alkali solution. At the same time, the flow rate of the alkali solution between the flat electrode and the same flat diaphragm needs to be precisely adjusted. When it is laminar flow, it is difficult for the alkali solution to fully contact the substrate. Only the alkali solution close to the substrate participates in the reaction. During the reaction, gas is also generated on the substrate, which further limits the area of ​​the plate participating in the reaction and the area in contact with the alkali solution. When it is turbulent, the fluid can contact the plate, and the turbulence can promote the discharge of the generated gas as soon as possible, which is convenient for the generation of new gas between the plate and the alkali solution. However, the flow state between the flat plate and the flat diaphragm needs to adjust the flow rate, and turbulence cannot be directly produced.

[0013] 3) The reaction rate of hydrogen production by water electrolysis is greatly affected by heating start-up

[0014] Alkaline water electrolysis requires a reaction temperature of about 90-95°C for hydrogen production. During the start-up process of water electrolysis, the alkaline water at room temperature needs to be heated to the reaction temperature through electric heating before the reaction can begin, resulting in slow hydrogen production and low efficiency. If there is fluctuation in renewable energy power generation during the process, it will cause unstable heating, accompanied by unstable power supply, which will affect the efficiency and rate of hydrogen production.

[0015] 4) Insufficient technical space to increase the overall temperature of alkaline water

[0016] The Arrhenius equation reveals the quantitative relationship between the reaction rate constant and temperature. When the temperature rises, the reaction rate constant increases; and when the temperature decreases, the reaction rate constant decreases. This shows that temperature has a greater effect on the rate constant of reactions with large activation energy, and has a smaller effect on the rate constant of reactions with small activation energy. In the low temperature range, the temperature has a greater effect on the reaction rate coefficient; while in the high temperature range, the temperature has a smaller effect on the reaction rate coefficient. Summary of the invention

[0017] In view of the above-mentioned problems, the present invention aims to provide a structure and method for improving hydrogen production by alkaline water electrolysis, through which the contact area between the electrode plate and the alkaline solution can be increased; the function of promoting the flow of the alkaline solution and the rapid detachment of the generated bubbles can be achieved, thereby increasing the production of hydrogen and oxygen.

[0018] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: a structure for improving hydrogen production by alkaline water electrolysis, including an electrolytic cell and an electrode plate, characterized in that a surface enlargement structure is provided on the electrode plate, and a self-heating structure is also provided on the electrode plate, and the heating mechanism accelerates the discharge of bubbles generated on the surface of the electrode plate.

[0019] Preferably, the surface enlarging mechanism is to configure the electrode plate to have an elliptical cross-section.

[0020] Preferably, the heating mechanism is an electric heating component uniformly arranged inside the electrode plate and along its entire length.

[0021] Preferably, the heating temperature of the electrode plate by the electric heating component increases gradually from bottom to top.

[0022] Preferably, a driving mechanism for driving the electrolyte into a turbulent state is also provided on the inner bottom surface of the electrolytic cell located at the bottom of the electrode plate.

[0023] A method for improving hydrogen production by alkaline water electrolysis comprises the following steps:

[0024] S1. While heating the electrolyte in the electrolytic cell, the electrode plate is simultaneously preheated and heated by the electric heating component in the electrode plate;

[0025] S2, after the electrolyte and the electrode plate are heated to the electrolysis temperature, the electrode plate is heated by the electric heating component simultaneously, so that the temperature of the electrode plate gradually increases from bottom to top;

[0026] S3. After the electrolysis starts, the electrolyte in the electrolytic cell is driven by a driving mechanism to form a turbulent flow from the bottom upward.

[0027] Preferably, in step S2, after the electrolyte and the upper end of the electrode plate are heated to 50°C simultaneously, the upper surface temperature of the electrode plate is heated to 150°C and the lower surface temperature is heated to 100°C by the electric heating component.

[0028] The beneficial effects of the present invention are: using an elliptical (double arc surface) structure electrode plate to increase the contact area between the electrode and the catalyst on the electrode surface and alkaline water, thereby increasing the area, facilitating full contact with the liquid, and facilitating the separation of bubbles.

[0029] A thin electric heating wire is built into the electrode. The heating temperature of the electric heating wire is higher than the temperature of the alkaline water, which improves the catalytic effect of the catalyst on the electrode surface and accelerates the efficiency of water electrolysis on the electrode surface. The density of the electric heating wire decreases from top to bottom in the vertical direction. The effect is that after power is turned on and heated, the temperature of the electrode surface decreases from top to bottom, forming a relatively high temperature in the catalyst layer on the electrode surface to promote the electrolysis efficiency, and facilitates the rapid discharge of bubbles generated by the alkaline solution and the electrode surface.

[0030] The (low-speed) propeller blade structure is used to promote the formation of turbulent flow of the alkali solution, thereby improving heat exchange, promoting the flow of the alkali solution, promoting the rapid separation of the generated bubbles, and increasing the contact time between the electrode and the liquid.

[0031] In terms of reaction heat, the method of electric heating of the internal temperature of the electrolyzer has been optimized, and internal heating of the electrode is used to ensure that the electrode surface reaches the reaction heat, that is, it does not rely on the overall electrolyte temperature to reach the design operating conditions. Hydrogen and oxygen can be produced as long as the electrode surface reaches the design temperature, which helps to produce more hydrogen and oxygen when the system is started and is about to shut down. At the same time, when the electrolyzer heats the electrolyte, the electrode plate is heated first, so that the electrolysis operation can be carried out first through the self-heating of the electrode plate while the electrolyte is heated to the electrolysis temperature. This can extend the duration and amount of hydrogen production by electrolysis, while reducing the energy consumption of hydrogen production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a diagram of the current hydrogen production by electrolysis.

[0033] Figure 2 This is a top view of the electrolysis plate of the water electrolysis hydrogen production structure of the present invention.

[0034] Figure 3 It is a schematic diagram of the electrolytic cell structure of the present invention.

[0035] Figure 4 It is a diagrammatic illustration of the electric heating wire structure in the hydrogen production structure of the present invention.

[0036] Figure 5 This is an overall diagram of the current electrolytic hydrogen production electrolyzer.

[0037] In the figure: 1-electrode plate with catalyst (surface); 2-positive and negative electrode separators; 3-electric heating wire; 4-electric heating isolation layer; 5-connecting reinforcement ribs; 6-electrolytic cell; 7-cathode; 8-anode; 9-diaphragm; 10-propeller blades. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0039] See attached Figures 1 to 4 The structure shown is for improving hydrogen production by alkaline water electrolysis, comprising an electrolytic cell 6 and an electrode plate 1, wherein the electrode plate 1 is provided with a surface enlargement structure. (Because the placement space of the electrode plate 1 in the electrolytic cell 6 is usually limited, and the electrode plate 1 is a flat plate structure, the electrolysis area is rated.) By increasing the surface area of ​​the electrode plate 1 through the surface enlargement structure, it helps the electrode plate 1 to fully contact with the electrolyzed alkaline liquid, thereby improving the electrolysis efficiency. At the same time, after the electrolysis area is increased, the bubbles generated by the electrolysis are diffused on the electrode plate 1, thereby solving the problem of bubble accumulation on the electrode plate 1 with a smaller area and difficulty in achieving gas-liquid separation. Furthermore, by increasing the surface area of ​​the electrode plate 1, it also helps the bubbles to separate.

[0040] In order to improve the electrolysis efficiency of the electrode plate 1, the present application also provides a self-heating structure on the electrode plate 1. Through the heating mechanism, the electrode plate 1 is not affected by the transmission loss of the electrolyte temperature under high-temperature electrolysis. By heating the inside of the electrode plate 1, a relatively high temperature is formed in the catalyst layer on the surface of the electrode plate 1, which can effectively promote the improvement of the electrolysis efficiency.

[0041] By heating the electrode plate 1, after the electrolysis efficiency is improved, the electrolysis bubbles increase, driving the electrolysis bubbles to quickly detach from the electrode plate 1, so that the heating mechanism can also accelerate the discharge of bubbles generated on the surface of the electrode plate 1, further improving the electrolysis efficiency.

[0042] Specifically, Figure 2 As shown, the surface enlargement mechanism is to set the electrode plate 1 to have an elliptical (double arc surface) cross-section. Compared with a planar structure, the electrode plate 1 of this structure can fully increase the circumferential area of ​​the electrode plate 1 and the surface electrolysis area in the electrolytic cell 6 of effective width, and the arc surface structure has a good contact effect with the liquid surface, and it is also convenient for hydrogen to be separated after hydrogen or oxygen is generated, thereby improving the electrolysis efficiency.

[0043] To realize the self-heating effect of the electrode plate 1, Figure 2 As shown, specifically, the heating mechanism is an electric heating component uniformly arranged inside the electrode plate 1 and along its length direction. The electric heating component is preferably an electric heating wire 3, which can heat the electrode plate 1 separately while heating the electrolyte, thereby solving the current problem of heat transfer loss of the electrode plate 1 to the electrolyte during electrolysis, accelerating the generation and release of electrolytic bubbles on the surface of the electrode plate 1, thereby improving the electrolysis efficiency.

[0044] The present application adopts internal heating of the electrode to ensure that the electrode surface reaches the heat of reaction, that is, it does not rely on the overall electrolyte temperature to reach the design operating conditions. It only needs the electrode surface to reach the design temperature to produce hydrogen and oxygen, which helps to produce more hydrogen and oxygen when the system is started and close to shutdown. At the same time, when the electrolyzer 6 heats the electrolyte, by preferentially heating the electrode plate 1, the self-heating of the electrode plate 1 can be used to preferentially perform the electrolysis operation while the electrolyte is heated to the electrolysis temperature. This can extend the duration and amount of hydrogen production by electrolysis, while reducing the energy consumption of hydrogen production.

[0045] Furthermore, the heating temperature of the electrode plate 1 by the electric heating component gradually increases from bottom to top, that is, the density of the electric heating wire decreases from top to bottom in the vertical direction, and the effect is that after the electric heating, the surface temperature of the electrode decreases from top to bottom, which facilitates the rapid discharge of bubbles generated by the alkali solution and the surface of the electrode plate 1, forms a temperature gradient difference in the vertical direction of the electrode plate 1, and promotes the separation of hydrogen and oxygen generated by electrolysis as soon as possible. The heating temperature of the electric heating wire is higher than the temperature of the alkali water, which improves the catalytic effect of the catalyst on the electrode surface and accelerates the efficiency of water electrolysis on the electrode surface.

[0046] In order to further quickly separate the bubbles generated by electrolysis on the electrode plate 1, Figure 3 As shown, a driving mechanism for driving the electrolyte to be in a turbulent state is also provided on the inner bottom surface of the electrolytic cell 6 located at the bottom of the electrode plate 1. The driving mechanism is preferably a propeller blade 10. During the electrolysis process, the propeller slurry promotes the contact between the alkaline electrolyte and the electrode, and promotes the alkali solution to be in a turbulent flow state, promotes heat balance, and promotes the hydrogen generated by electrolysis to leave the electrode plate 1 as soon as possible, thereby improving the electrolysis efficiency.

[0047] The overall structure of the electrode plate 1 is as follows Figure 2 As shown, it also includes positive and negative electrode separators 2, an electric heating isolation layer 4, and connecting reinforcing ribs 5. The connecting reinforcing ribs 5 can connect adjacent electrode plates 1 into an integral structure, making full use of the space in the electrolytic cell to expand the contact area and increase the hydrogen output.

[0048] The present application also provides a method for improving hydrogen production by alkaline water electrolysis, comprising the following steps:

[0049] S1. While heating the electrolyte in the electrolytic cell 6, the electrode plate 1 is simultaneously preheated and heated by the electric heating component in the electrode plate 1.

[0050] Due to the direct power supply mode, there will be a large power consumption in industrial hydrogen production. Therefore, in order to increase the application scope of the hydrogen production mechanism, when the photovoltaic power supply mode is adopted, the starting conditions are specifically as follows: before the sunrise stage of photovoltaic power generation in the morning, battery energy storage is used to start heating the electrolyte in the electrolytic cell 6.

[0051] The operating conditions are as follows: the power supply for electrolysis water is stepped down and converted into direct current by a transformer, and then enters the energy storage battery, the energy storage capacitor, and the electrolyzer 6. When the photovoltaic new energy generates less electricity in the early morning, the battery and photovoltaic are connected in parallel. As the photovoltaic power generation increases, the battery gradually builds up less power output and starts charging; when the photovoltaic or wind power generation is unstable due to environmental influences, the short-term power fluctuation is compensated by the capacitor discharge, and the long-term is compensated by the energy storage battery. At night, when the photovoltaic is attenuated by the reduced sunlight, the energy storage battery is first filled, and then the hydrogen production is gradually stopped. In the initial stage of hydrogen production, that is, the electrolyte heating stage, the electrolytic plate is heated first by the electric heating wire to make the water near it reach the temperature that can be electrolyzed (such as about 90-95°C), and the water near the electrode plate can be electrolyzed to produce hydrogen, saving the long period of electrolyte heating, thereby increasing the hydrogen production. After the electrolyte is heated to the electrolysis temperature, the normal hydrogen production condition can be achieved.

[0052] Photovoltaic power generation is affected by short-term cloud fluctuations and longer-term clouds and cloudy days. Capacitors are used to compensate for short time sequences, while batteries are used to compensate for long time sequences, which helps to ensure the stability of the power supply side.

[0053] When the wind power supply mode is adopted, the specific starting conditions are as follows: Since wind power is different from photovoltaic power generation day and night, it is mainly affected by the hourly changes of the environmental wind field. Therefore, when the wind power mode is used for power supply, the main function of the energy storage on the side of the electrolyzer 6 is to adjust the output fluctuation of wind power generation. Before the electrolyzer 6 is started, the wind power generation first fills the energy storage battery (providing a basic stable power supply), and after the battery is full, the wind power generation heats the electrolyte.

[0054] The operating conditions of wind power supply are: after the wind power is reduced in voltage and converted to DC, one path goes into the energy storage battery and the other path is directly connected to the electrolyzer 6 (considering that the fluctuations of wind power generation and photovoltaic power generation are different, the short-time compensation of capacitor is not set for wind power generation). When the wind power generation fluctuates, the parallel energy storage battery compensates the power supply to maintain stable electrolysis.

[0055] When the electrode plate 1 with built-in electric heating wire 3 is used, the electric heating wire 3 in the electrode plate 1 is powered on for preheating (to prevent deformation due to rapid heating), and after the alkaline electrolyte is heated to 50°C, the upper end of the electrode is heated to 50°C.

[0056] S2. After the electrolyte and the electrode plate 1 are heated to the electrolysis temperature, the electrode plate 1 is heated synchronously by the electric heating component, and the temperature gradually increases from bottom to top. Specifically, when the alkaline electrolyte is heated to 50°C and the upper end of the electrode is heated to 50°C, the electric heating inside the electrode can increase the power so that the upper surface temperature of the electrode reaches 150°C and the lower temperature reaches 100°C. At this time, the alkaline water will not boil under the system working pressure, and the high temperature is only on the electrode surface, which cooperates with the catalyst to reduce the activation energy of the electrolysis reaction. The working pressure of the electrolyzer 6 (such as the ALK Hi1 series electrolyzer of Longi Company) is mostly 1.6MPa, and the boiling temperature of water is 201°C, and the boiling temperature of water is 150°C at 1.0MPa. Therefore, the upper part of the electrode plate 1 is heated at 150°C, and the lower part is heated at 100°C, forming a temperature gradient difference in the vertical direction of the electrode, which promotes the separation of hydrogen and oxygen produced by electrolysis as soon as possible.

[0057] In order to further realize the hydrogen production operation more quickly in the initial stage of the entire hydrogen production system startup, preferably, Figure 4As shown, the electric heating wire 3 in the electrode plate 1 is set to a conical structure with a larger upper part and a smaller lower part. The electric heating wire 3 on the upper side of the structure is closer to the outer wall of the electrode plate 1 (the wall thickness of the electrode plate 1 increases from top to bottom), and with the high-density arrangement structure, the outer wall of the upper side of the electrode plate 1 can achieve faster heating and temperature rise (heat conduction); while the lower side is relatively far away from the outer surface of the electrode plate 1, thereby achieving a slower heating process after heating, and on the basis of realizing the upper and lower gradient temperature difference, further accelerating the faster heating of the upper side of the electrode plate 1, that is, hydrogen production can be quickly achieved in the initial stage of hydrogen production, solving the problem of heating and long waiting time; and the slightly lower temperature on the lower side of the electrode plate 1 is also easy to control through the gradient change of the wall thickness of the electrode plate 1, avoiding the problem that the electric heating wire of the upper and lower integrated structure cannot accurately control (distinguish) the temperature difference between the upper and lower sides due to heat transfer, and then through this structure, on the basis of realizing rapid hydrogen production, the precise control (distinguishment) of the upper and lower temperatures of the electrode plate 1 is simultaneously achieved.

[0058] S3. After the electrolysis starts, the electrolyte in the electrolytic cell 6 is driven by the driving mechanism to form a turbulent flow state from the bottom to the top.

[0059] The principle of the present invention is: the electrode plate 1 is set to have an elliptical (double-arc) cross-section structure, and electric heating wires 3 are evenly distributed inside the electrode plate 1 and along its length, the density of the electric heating wires 3 decreases from top to bottom in the vertical direction, and propeller blades 10 are also provided on the bottom surface of the electrolytic cell 6 located at the bottom of the electrode plate 1 to drive the electrolyte into a turbulent state.

[0060] During the process of hydrogen production by electrolysis, the electrolyte in the electrolytic cell 6 is first heated, and the electrode plate 1 is simultaneously preheated and heated by the electric heating component in the electrode plate 1. The electrolytic plate is heated first by the electric heating wire, so that the water body near the electrode plate reaches a temperature that can be electrolyzed (such as about 90-95°C), and then the water body near the electrode plate can be electrolyzed to produce hydrogen. After the electrolyte is heated to the electrolysis temperature, the normal hydrogen production condition can be achieved.

[0061] During the hydrogen production process, the upper part of the electrode plate 1 is heated to 150°C and the lower part is heated to 100°C by the electric heating wire 3, forming a temperature gradient difference in the vertical direction of the electrode to promote the separation of hydrogen and oxygen produced by electrolysis as soon as possible.

[0062] S3. After the electrolysis starts, the electrolyte in the electrolytic cell 6 is driven by the driving mechanism to form a turbulent flow state from the bottom to the top.

[0063] The above shows and describes the basic principle, main features and advantages of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention claimed.

Claims

1. A structure for improving hydrogen production by alkaline water electrolysis, comprising an electrolytic cell and an electrode plate, characterized in that: The electrode plate is provided with a surface enlargement structure, and a self-heating structure is also provided on the electrode plate. The heating mechanism accelerates the discharge of bubbles generated on the surface of the electrode plate.

2. The hydrogen production structure according to claim 1, characterized in that: The surface enlargement mechanism is to set the electrode plate to have an elliptical cross-section structure.

3. The hydrogen production structure according to claim 2, characterized in that: The heating mechanism is an electric heating component uniformly arranged inside the electrode plate and along the length direction thereof.

4. The hydrogen production structure according to claim 3, characterized in that: The heating temperature of the electrode plate by the electric heating component increases gradually from bottom to top.

5. The hydrogen production structure according to claim 4, characterized in that: A driving mechanism for driving the electrolyte to be in a turbulent state is also arranged on the inner bottom surface of the electrolytic cell located at the bottom of the electrode plate.

6. A method for improving hydrogen production by alkaline water electrolysis, characterized in that: The following steps are involved: S1. While heating the electrolyte in the electrolytic cell, the electrode plate is simultaneously preheated and heated by the electric heating component in the electrode plate; S2, after the electrolyte and the electrode plate are heated to the electrolysis temperature, the electrode plate is heated by the electric heating component simultaneously, so that the temperature of the electrode plate gradually increases from bottom to top; S3. After the electrolysis starts, the electrolyte in the electrolytic cell is driven by a driving mechanism to form a turbulent flow from the bottom upward.

7. The method for producing hydrogen according to claim 6, characterized in that: In step S2, after the electrolyte and the upper end of the electrode plate are heated to 50°C simultaneously, the upper surface temperature of the electrode plate is heated to 150°C and the lower surface temperature is heated to 100°C by the electric heating component.

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