KR890006975Y1 - Electrolytic bath for electrolyzing seawater - Google Patents

Abstract

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Description

Electrolyzer for Seawater Direct Electrolysis

1 is an exploded perspective view of the present invention electrolyzer.

FIG. 2 (a) and FIG. 2 (b) are front and side cross-sectional views of the present invention electrolytic cell.

3 is a schematic diagram of a direct electrolysis device.

* Explanation of symbols for main parts of the drawings

1 body 2 anode

3: cathode 3a, 3b: both sides edge of cathode

4,5 Electricity plate 6: Seawater inlet

7: seawater outlet

The present invention relates to an electrolytic cell for seawater direct electrolysis to generate sodium hypochlorite by directly electrolyzing seawater, and in particular, it is necessary to reduce the sedimentation of sediment that is inevitably generated during electrolysis and adheres to the electrode plate of the electrolytic cell. B. It relates to an electrolytic cell that prevented corrosion as much as possible.

Plants such as nuclear power plants, coal-fired power plants, steel mills, or chemical plants use seawater as cooling water. Increasing the resistance of the lowering of the heat exchange efficiency of the cooler, various problems such as to promote the corrosion of the cooling system.

Conventionally, in order to prevent marine organisms from adhering and propagating in the seawater inflow passage, a liquid chlorine treatment method in which a separate liquid chlorine is injected into the seawater inflow passage has been used, but since the liquid chlorine itself is a dangerous substance having strong toxicity, it is transported. And dangerous handling, high corrosiveness at high pressure and high temperature, resulting in leakage accidents caused by corrosion of the cooling system. There was a discontinuance.

On the other hand, the seawater electrolysis apparatus which continuously injects sodium hypochlorite generated by electrolysis of seawater directly into the cooling water intake port of the cooling device, paying attention to the fact that sodium hypochlorite (NaOC ^I ) has the same action as the liquid chlorine described above. (For example, Japanese Utility Model No. 57-4564, Japanese Patent Application No. 59-182982, and Japanese Utility Model No. 61-43266, etc.)

The present invention relates to the improvement of these devices, and in particular, by changing the structure of the electrolytic cell (CELL), which is a key part of the seawater electrolysis device, to increase the production rate of sodium chlorine, and to inevitably generate precipitates as side reactions during electrolysis. The present invention is to provide an electrolytic cell which can prevent the wear and corrosion of the electrode plate and greatly reduce the number of cleaning operations of the electrolytic cell by mitigating the phenomenon attached to the electrode plate in the electrolytic cell as much as possible. It demonstrates in detail by.

1 and 2 illustrate the internal structure of the present invention electrolytic cell, and the anode 2 and the cathode 3 having a plate shape inside the main body 1 are maintained at regular intervals from each other. A plurality of comb teeth are provided. Among them, the anode 2 is fabricated by coating a platinum group oxide after lightly plating platinum on a titanium substrate, and the cathode 3 is made of stainless steel (SUS 316L).

The number of anodes (2) is set to about 10 sheets in consideration of seawater electrolysis efficiency and the number of cathodes (3) is about 11 sheets, where the total area of the effective electrolyte of the cathode (3) is greater than 50% larger than that of the anode (2). Some of the cathodes 3 protrude from the upper and lower ends of the anode 2 so as to protrude.

On the other hand, in order to reduce the fluid resistance in the body 1, the upper end of the cathode 3 is " "In order to shape and to round both corners (3a) and (3b) and to minimize electrical resistance, each electrode (2) (3) and the conduction plate (4) (5) inside the body (1) ) Is welded to each other.

Reference numeral 6 denotes a seawater inlet, 7 seawater outlet, 8 · 8 ', 9 · 9' are insulation packings on the anode and cathode sides, and 1a · 1b · 1c are the upper, middle, and lower portions of the main body 1.

Seawater is a complex solution of various salts and the like, and it is difficult to express it as a simple reaction formula such as salt electrolysis during electrolysis, but since it can be viewed as a saline alkali solution of about 3%, the reaction scheme can be summarized as follows.

(A) Anode Reaction

_{^{2Cl - → Cl 2 + 2e -}} ... … (One)

_{4OH → O 2 + 2H 2 O} + 4e - ... … (2)

(B) Cathode Reaction

2Na ^{+ +} 2e ^- → 2Na ... … (3)

2H ₂ O + 2Na → NaOH + H ₂ . … (4)

In other words, as shown in Equation (1), chlorine ions in seawater are discharged to generate chlorine, which reacts with sodium hydroxide (Na (OH) ₂ ) generated at the cathode to produce sodium hypochlorite as shown in the following equation. .

Cl ₂ + 2NaOH → NaOCl + NaCl + H ₂ O... … (5)

Therefore, the overall reaction can be represented by the following equation.

On the other hand, as a side reaction that occurs essentially during the electrolysis of seawater can be represented by the following equation.

₂ NaOH + MgCl ₂ → Mg (OH) ₂ +2 NaCl. (7)

₂ NaOH + CaCl ₂ → Ca (OH) ₂ +2 NaCl. (8)

^{_{OCl + H 2+ 2e - → Cl}} - + 2OH ... (9)

^{_{2HOCl + OCl → ClO 3 - +}} 2Cl - + 2H + ... 10

2OCl ^- → O ₂₊ 2Cl ^- ... (11)

H ₂ + OCl ⁻ → H ₂ O + Cl... (12)

At this time, magnesium hydroxide (Mg (OH) ₂ ), calcium hydroxide (Ca (OH) ₂ ), and the like, which are colloidal white precipitates produced by the cathode 3, may be formed on the surface of the cathode 3 or the inner wall of the electrolytic cell body 1. It is attached to not only disturb the flow of sea water, but also increase the electrical resistance, causing a decrease in current efficiency, the gap between the poles 2-4m / by inducing the diffusion of deposit deposit area by the cathode (3) structure of the present invention The long period of operation of the electrolyzer is possible by extending the section in which the precipitate is settled between the positive electrode 2 and the negative electrode 3 which are constantly arranged at about m, and prevents the burnout of the electric electrode, thus extending the life of the positive electrode 2. It becomes possible.

That is, since the negative electrode 3 protrudes from the positive electrode 2 toward the seawater inlet 6 and the seawater outlet 7 in the electrolytic cell body 1, the seawater comes into contact with the negative electrode 3 first during electrolysis and thus magnesium hydroxide. Or calcium hydroxide and other cationic precipitates are attached to the protruding portion of the cathode 3, thereby minimizing the adhesion of the precipitate in a portion where the positive current 2 and the negative electrode 3 through which high current flows are uniformly arranged. The seawater outlet 7 of 1) is again connected in series with the seawater inlet of the other electrolyzer body, so that the same effect can be obtained even at the protruding portion of the cathode 3 toward the seawater outlet 7 so that the expensive anode 2 It plays a crucial role in prolonging life.

The theoretical generation amount (Q ₁ ) of sodium hypochlorite generated by the chemical reaction as described above is 1,00 g equivalent of effective combustion in the amount of charge of 96,500 × 2 (Kulm) from Paragraph's law from the above equation (3). Sodium hypochlorite is produced.

Therefore, the generation amount (Q ₁ ) when the current of 1A flows for 1 hour (3,600) is as follows.

Where 95, 500 (coulomb) is the amount of charge of one paradi, and 74.44 "t-3" is the molecular weight of sodium hypochlorite.

However, in actual quantitative analysis of effective chlorine, it is not quantitatively determined as sodium hypochlorite but as effective chlorine.

In other words, Where the atomic weights of Na, Cl and O are 22.9898, 35.453 and 15.999, respectively.

Therefore, the amount of chlorine generated when flowing 1A of current for 1 hour

It becomes

In addition, the theoretical amount of chlorine generated (W ₁ )

Where 1.323 is the chlorine electrochemical equivalent, 1 (A) is the electrolytic current, and n is the number of series electrolyzers.

The actual amount of chlorine generated (W ₂ ) is calculated by the following equation.

In other words,

(Where C is the generated chlorine concentration (PPM) t-1 / m and Q is the seawater capacity (㎥ / hr))

On the other hand, since seawater is electrolyzed to generate chlorine, oxygen and other compounds are generated, resulting in current loss. Also, chlorine generated by reaction of impurities in seawater is also affected by decomposition of organic matter. May be reduced.

Current efficiency It is expressed by the formula, and the actual amount of chlorine generated (W ₂ ) is

It is expressed by the formula

Therefore, when the amount of power (P) required to generate a unit amount of chlorine is referred to as a power source unit, as shown in the following equation, it is possible to save power consumption by lowering the electrolytic voltage and increasing the current efficiency.

Where P is DC power consumption (KWH / chlorine ton), V is electrolytic voltage, Is the current efficiency)

3 shows a system of a seawater direct electrolysis apparatus to which the present invention electrolyzer is applied, and the rectifier 10 is used to generate a DC power required for electrolysis of an input AC power, and varies a DC current suitable for the amount of chlorine generated. The inner wall of each electrolyzer body 1 is hard rubber lining treatment to withstand acid during electrolysis, and the body 1 is upper and middle as shown in FIG. It consists of lower part 1a (1b) (1c).

The seawater intake pump 11 and seawater strainer 12 are respectively installed to intake a certain amount of seawater from the intake port 13 and to prevent damage to the electrode plate inside the electrolytic cell body 1 due to foreign matter inflow. The electrolyte bath 14 and the injection pump 15 are each for removing hydrogen generated during electrolysis and supplying the electrolyte at a constant pressure at each injection point.

On the other hand, precipitates such as magnesium hydroxide adhered to the electrode plates of the electrolytic cell body 1 by electrolysis of seawater as described above cause the efficiency of the electrolytic device or wear of the electrolytic cell plate coatings to increase the voltage between the electrodes. Pickling work to wash the inside of the electrolytic cell body (1) with hydrochloric acid should be done at an appropriate interval.

As described above, the present invention can alleviate the deposition of sediment attached to the electrode plate in the electrolyzer by electrolysis of seawater to the maximum, thereby increasing the generation rate of sodium hypochlorite and improving the efficiency of the electrolytic device, as well as wear of the electrode plate. And to prevent corrosion and to reduce the number of electrolytic cell cleaning operations.

Claims (4)

In the electrolytic cell for seawater direct electrolysis in which a plurality of positive and negative electrodes (2) and negative electrodes (3), which are supplied with power through each current-carrying plate (4) and (5) inside the main body (1), are provided in a comb-tooth form at a predetermined interval from each other, The length of the negative electrode 3 is formed longer than the positive electrode 2 so that the effective electrolyte area is 1.5 times or more, and the upper and lower ends of the negative electrode 3 protrude from the upper and lower end positions of the positive electrode 2, respectively. Electrolyzer for seawater direct electrolysis, characterized in that. 2. The upper end of the cathode 3 according to claim 1, The electrolytic cell for seawater direct electrolysis, characterized in that it is molded into a shape and curved at both edges 3a and 3b thereof. The electrolytic cell for seawater electrolysis according to claim 1, wherein the number of the anodes (2) is 10 and the number of the cathodes (3) is 11. The electrolytic cell for seawater electrolysis according to claim 1, characterized in that the junction between the anode (2) and the cathode (3) and each conducting tube (4) (5) is electrically welded to each other.