A method for improving the anti-deposition performance of an electrochemical device

Abstract

The application discloses a method for improving the anti-deposition performance of an electrochemical device, and belongs to the field of electrochemical technology. The method comprises the following steps: adding a certain amount of one or both of an alkaline substance and a fine particulate substance in an electrolyte in advance, so that small-particle suspensions are generated in the electrolyte, the suspensions provide deposition sites for magnesium and calcium deposition, and thus the deposition of magnesium and calcium on the inner wall of the electrochemical device or the surface of an electrode is reduced. The method solves the problem that when a water source containing magnesium, calcium and other impurity ions such as seawater and lake water is used as an electrolyte, the electrochemical device is prone to depositing magnesium and calcium hydroxide, magnesium and calcium oxide or magnesium and calcium carbonate on the inner surface or the electrode due to the change of pH, the method is simple to implement, requires little equipment modification or additional requirements, and is a high-efficiency method for solving the deposition of magnesium and calcium impurities in the electrochemical device.

Description

Technical Field

[0001] This invention belongs to the field of applied electrochemical technology, specifically relating to a method for reducing the deposition of magnesium and calcium in electrolytes on the inner wall of an electrochemical device and the corresponding electrode surface. This method can be applied to fields such as direct electrolysis of seawater / saline water to produce hydrogen, direct electrolysis of seawater / saline water to produce chlorine, and metal / seawater batteries. Background Technology

[0002] Because seawater, lake water, river water, and groundwater contain high levels of magnesium and calcium ions, when these waters are used as electrolytes in electrolytic cells or batteries, changes in the electrolyte pH due to electrode reactions, or the accumulation of these ions leading to a continuous increase in their concentration, can easily cause magnesium and calcium deposits to form inside the device. For example, in direct seawater electrolysis for hydrogen and chlorine production, and in metal-seawater batteries, the hydrogen evolution electrode generates hydroxide ions along with hydrogen gas, significantly increasing the pH at the electrode surface and causing magnesium and calcium ions in the electrolyte to deposit on the electrode surface. These deposits impede mass transfer at the electrode surface, increasing electrode polarization and degrading device performance; the detachment of lumpy deposits can also clog the device's pipes, posing a threat. Therefore, minimizing the impact of magnesium and calcium ion deposits on the device is crucial for the direct utilization of natural water.

[0003] Existing technologies include installing ultrasonic equipment in electrolytic cells for in-situ cleaning (CN215440699U), but this has significant drawbacks. The effect of ultrasonic equipment is not obvious, and it increases the complexity and cost of the device. Therefore, finding a more cost-effective and convenient solution to address magnesium and calcium deposition on the inner walls of the device or the electrode surfaces is crucial. Summary of the Invention

[0004] This invention addresses the problem that when water containing magnesium and calcium ions is used as the electrolyte, magnesium and calcium hydroxides, oxides, or carbonates easily deposit on the inner or electrode surfaces of electrochemical devices. The invention provides a method to improve the anti-deposition performance of electrochemical devices by pre-adding alkaline or fine particulate matter to the electrolyte. This creates small particulate suspensions in the electrolyte, which provide deposition sites for magnesium and calcium, thereby reducing their deposition on the inner walls or electrode surfaces and increasing the device's lifespan.

[0005] This invention provides the following technical solution:

[0006] This invention provides a method for improving the anti-deposition performance of an electrochemical device. By adding a certain amount of alkaline substance or one or two fine particulate substances to the electrolyte in advance, small particulate suspensions are generated in the electrolyte. The suspensions provide deposition sites for magnesium and calcium deposition, thereby reducing the deposition of magnesium and calcium on the inner wall or electrode surface of the electrochemical device.

[0007] Based on the above technical solution, further, the alkaline or fine particulate matter accounts for 0.05%-5% of the mass of the electrolyte.

[0008] Based on the above technical solution, the alkaline substance is one or more hydroxides, oxides, or mixtures of hydroxides and oxides selected from alkali metals Li, Na, K and alkaline earth metals Mg, Ca.

[0009] Based on the above technical solution, the fine particulate matter is further defined as a spherical, rod-shaped, sheet-like, or complexly shaped particulate matter with dimensions at the micrometer or nanometer level.

[0010] Based on the above technical solution, the fine particulate matter further includes oxides, hydroxides, sulfides, silicates, phosphates, carbonates, and other sparingly soluble substances such as oxides, hydroxides, sulfides, silicates, phosphates, and carbonates of Mg, Ca, Ti, Mn, Fe, Co, Ni, Cu, Zn, Si, and Al. The particulate matter has good hydrophilicity and excellent dispersibility in aqueous solution; preferably, it is one or a combination of two or more of calcium carbonate, calcium phosphate, calcium magnesium phosphate, zinc oxide, silicon oxide, and aluminum oxide.

[0011] Based on the above technical solution, the electrochemical device further includes a metal seawater battery and an electrolytic hydrogen / chlorine production device.

[0012] Based on the above technical solution, further, for metal-seawater batteries, the electrolyte is not circulated. One or two alkaline substances or fine particulate substances are directly mixed evenly with the electrolyte and then added to the electrochemical device for discharge; or one or two alkaline substances or fine particulate substances are placed in advance inside the electrochemical device and then the electrolyte is added for discharge.

[0013] Based on the above technical solution, further, for the electrolytic hydrogen / chlorine production device, one or two of the alkaline substances or fine particulate substances are directly mixed evenly with the electrolyte and then added into the hydrogen / chlorine production device. One end of the hydrogen / chlorine production device is provided with an electrolyte inlet, and the other end is provided with a reactant outlet. The outlet is connected to a gas-solid-liquid-solid separator. Through the separator, part of the electrolyte containing solids is circulated back to the electrolyte inlet, so that the electrolyte entering the hydrogen / chlorine production device is turbid; or by controlling the electrolyte flow rate, it is possible to continuously maintain small particulate suspension in the hydrogen / chlorine production device.

[0014] The advantages of this invention over the prior art are as follows:

[0015] This invention adds alkaline or fine particulate matter to an electrolyte containing magnesium and calcium beforehand, resulting in the formation of small particulate suspensions in the electrolyte. These suspensions provide deposition sites for magnesium and calcium deposition. Compared to an electrolyte without added alkaline or fine particulate matter, the addition of alkaline or fine particulate matter significantly reduces deposits on the inner wall and electrode surface of the electrochemical device, thus increasing the device's lifespan. Attached Figure Description

[0016] To more clearly illustrate the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below.

[0017] Figure 1 This is a schematic diagram of the electrochemical device corresponding to the method for improving the anti-deposition performance of the electrochemical device according to the present invention; in the figure, 1 is the electrolyte inlet, 2 is the electrochemical device, 3 is the reactant outlet, 4 is the gas-liquid-solid separator, 5 is the gas outlet, 6 is the liquid outlet, 7 is the solid outlet and part of the solid-liquid circulation device, and 8 is the solid-liquid circulation inlet to the electrochemical device. Detailed Implementation

[0018] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0019] The test conditions in this example are as follows:

[0020] In the magnesium-seawater battery test, the electrolyte was seawater with a volume of 800 mL. The hydrogen evolution electrode was a nickel-foamed electrode, and the metal electrode was a magnesium alloy with an electrode area of ​​16 cm². 2 The electrode spacing is 0.5 cm, and the current density is 5 mA / cm². -2 The discharge time is 20 hours, and the battery casing is made of plastic. The amount of deposits on the inner wall of the battery casing and the electrode surface is categorized into five levels: very little, somewhat little, quite a lot, very much, and extremely much. "Very little" corresponds to <0.5 mg / cm³. -2 Less likely to correspond to 0.5-2mg cm -2 Most correspond to 2-10mg cm -2 Many correspond to 10-100mg cm -2 Many correspond to >100mg cm -2 .

[0021] In the seawater electrolysis hydrogen production device, the electrode size is 6cm×10cm, with 3 hydrogen evolution electrodes and 2 oxygen / chlorine evolution electrodes. The internal volume of the electrolysis cell is 2L, the current is 10A, and the time is 50h. The amount of deposits on the inner wall of the electrolysis cell shell and the electrode surface is the same as that of the battery.

[0022] Example 1

[0023] The electrochemical device was a magnesium-seawater battery, and the alkaline particulate matter was Mg(OH)2. First, 0.8 g of Mg(OH)2 was mixed thoroughly with 800 g of seawater. Then, the thoroughly mixed electrolyte was poured into the magnesium-seawater battery, and the battery was discharged within 20 minutes. After discharge, the deposition amount per unit area was calculated based on the mass difference between the battery casing and the electrodes.

[0024] Example 2

[0025] The electrochemical device is a magnesium-seawater battery, and the alkaline particulate matter is NaOH. First, 0.5g of NaOH is placed in the battery, and then 800g of seawater is poured into the battery. The seawater and alkali will automatically mix to form a relatively uniform turbid liquid. The battery will discharge within 60 minutes.

[0026] Example 3

[0027] The electrochemical device is a magnesium-seawater battery, and the fine particulate matter is CaCO3. First, 2g of CaCO3 is mixed evenly with 800g of seawater. Then, the mixed electrolyte is poured into the magnesium-seawater battery, and the battery is discharged within 20 minutes.

[0028] Example 4

[0029] The electrochemical device is a magnesium-seawater battery. The particulate matter is a mixture of Mg(OH)2 and CaCO3. First, 0.8g of Mg(OH)2 and 2g of CaCO3 are mixed evenly with 800g of seawater. Then, the evenly mixed electrolyte is poured into the magnesium-seawater battery, and the battery is discharged within 20 minutes.

[0030] Comparative Example 1

[0031] The electrochemical device is a magnesium-seawater battery, which uses seawater directly as the electrolyte, and other conditions are the same as in Example 1.

[0032] Example 5

[0033] The electrochemical device is a seawater electrolysis hydrogen production unit (see...) Figure 1 The alkaline particulate matter is Ca(OH)2. First, 20g of Ca(OH)2 is mixed evenly with 8kg of seawater. The evenly mixed electrolyte is then injected into electrochemical device 2 and separator 4 to start circulation. After the device is circulating normally, electrolysis begins. During electrolysis, the influent 1 is replaced with seawater, and the rate is controlled at 50mL / min. The circulation rate of the solid-liquid mixture into the inlet 8 of the electrochemical device is controlled at 10mL / min, and the amount of solids in the circulation is controlled at 0.2%-0.3%.

[0034] Example 6

[0035] The electrochemical device is a seawater electrolysis hydrogen production device. The alkaline particulate matter is NaOH. First, 10g of NaOH is mixed evenly with 8kg of seawater. Other conditions are the same as in Example 5.

[0036] Example 7

[0037] The electrochemical device is a seawater electrolysis hydrogen production device. The fine particulate matter is CaCO3. First, 20g of CaCO3 is mixed evenly with 8kg of seawater. Except for not circulating, the other conditions are the same as in Example 5.

[0038] Comparative Example 2

[0039] The electrochemical device is a seawater electrolysis hydrogen production device, which uses seawater as the electrolyte for direct electrolysis without adding alkaline substances or fine particulate matter. Other conditions are the same as in Example 7.

[0040] Table 1. Results of anti-deposition performance in Examples 1-7 and Comparative Examples 1-2

[0041]

[0042]

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the anti-deposition performance of an electrochemical device, characterized in that, By adding a certain amount of alkaline substances or one or two fine particulate substances to the electrolyte in advance, small particulate suspensions are generated in the electrolyte. The suspensions provide deposition sites for magnesium and calcium, thereby reducing the deposition of magnesium and calcium on the inner wall or electrode surface of the electrochemical device. The electrochemical device includes a metal seawater battery and an electrolytic hydrogen / chlorine production unit.

2. The method according to claim 1, characterized in that, The alkaline substance or fine particulate matter accounts for 0.05%-5% of the mass of the electrolyte.

3. The method according to claim 2, characterized in that, The alkaline substance is one or more hydroxides, oxides, or mixtures of hydroxides and oxides from alkali metals Li, Na, K and alkaline earth metals Mg, Ca.

4. The method according to claim 2, characterized in that, The fine particulate matter is a sparingly soluble particulate matter with dimensions in the micrometer or nanometer range, and can be spherical, rod-shaped, sheet-like, or composed of complex shapes.

5. The method according to claim 4, characterized in that, The fine particulate matter includes oxides, hydroxides, sulfides, silicates, phosphates, and carbonates of Mg, Ca, Ti, Mn, Fe, Co, Ni, Cu, Zn, Si, and Al.

6. The method according to claim 5, characterized in that, The fine particulate matter is one or a combination of two or more of the following: calcium carbonate, calcium phosphate, calcium magnesium phosphate, zinc oxide, silicon oxide, and aluminum oxide.

7. The method according to claim 6, characterized in that, For metal-seawater batteries, the electrolyte is not circulated. One or two alkaline substances or fine particulate substances are directly mixed with the electrolyte and then added to the electrochemical device for discharge. Alternatively, one or two alkaline substances or fine particulate substances are placed inside the electrochemical device beforehand and then the electrolyte is added for discharge.

8. The method according to claim 6, characterized in that, For electrolytic hydrogen / chlorine production devices, one or two alkaline substances or fine particulate substances are directly mixed evenly with the electrolyte and then added into the hydrogen / chlorine production device. One end of the hydrogen / chlorine production device is equipped with an electrolyte inlet and the other end is equipped with a reactant outlet. By controlling the electrolyte flow rate, small particulate matter can be continuously maintained in the hydrogen / chlorine production device.

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