JPS5923888A - Method for producing chlorine or hypochlorite from sea water - Google Patents

Abstract

PURPOSE:To improve electric current efficiency, by decreasing intermittently or periodically the conduction of electrolytic current in the stage of electrolyzing sea water with an electrolytic cell. CONSTITUTION:An insoluble anode 5 and a soluble cathode 6 are provided in an electrolytic cell 3, and sea water is introduced into the cell 3 through a sea water introducing pipe 1. Electric current is conducted from a power source 7 through current conductors 8, 9 to the electrodes 5, 6 to electrolyze the sea water, whereby chlorine or hypochlorite is produced. The timing when the decrease in the rate of generation of hypochlorous ions begins differs with the temp. of the sea water to be introduced. Thereupon, the pattern of the sea water temp. and electric current efficiency is beforehand stored in a control device 10 for electric current, and the output of the power source 7 is controlled by the output signal from a thermometer 2 provided to the pipe 1 with the conductor 11 to interrupt or decrease once the electrolytic current. The current efficiency is improved by repeating the abovementioned operation.

Description

[Detailed Description of the Invention] To produce acid salts and to produce chlorine or hypochlorite to prevent damage caused by marine organisms breeding on equipment using seawater, such as corrosion of seawater and clogging of seawater channels. Regarding the method.

The temperature of 211 water can drop to several degrees Celsius in winter, when it is below 10 degrees Celsius depending on the region, and this temperature drop can have a significant impact on electrolytic efficiency and electrode wear, especially for electrodes that exhibit high current efficiency at room temperature. have a negative impact.

In addition, the electrochemical equivalent of any substance (1 coulomb or IA
The amount of precipitation per hour) is completely frozen.

For example, for ctt it is 1.3228f/AHr.

Assuming that the actual amount of electrolyzed electricity is xAHr and the amount of chlorine generated is W2, the current efficiency η is expressed by the following equation.

η - (-) X − X 1 0 0 (%)x
1.3228 An example of the effect of seawater temperature on current efficiency is shown in Figure 1. FIG. 2 shows an example of changes in current efficiency over time at low temperatures. FIG. 3 shows the relationship between current efficiency and increase in electrolytic voltage. The examples shown in FIGS. 1 to 3 are cases in which platinum agate electrodes are used.

Electrode materials for anodes include platinum metal oxides, platinum metal profiteers oxides, platinum group metals, iron, manganese, lead oxides, etc. as insoluble materials, but a decrease in temperature causes a decrease in current efficiency and an increase in electrolytic voltage. In addition to the increase in power consumption due to such factors, the rise in voltage causes multiple reactions to occur, causing wear and tear on the electrode phases, making stable operation throughout the year difficult.

The present invention was proposed for the purpose of eliminating the above-mentioned defects, and includes a method for producing chlorine or hypochlorite by electrolytically treating seawater using an electrolytic cell equipped with an insoluble electrode. Provided is a method for producing chlorine, hypochlorite, or chlorate from seawater, characterized by intermittent or periodic reduction of electrolytic current flow during operation.

In the method of the present invention, when operating the electrolytic cell when seawater is at a low temperature, the electrolytic current is reduced intermittently or periodically to prevent a decrease in current efficiency and an increase in electrolytic voltage. In addition to preventing increases in power consumption due to dirt, it also effectively prevents wear and tear on the electrodes due to double reactions caused by increases in electrolytic voltage.

In turn, this enabled stable operation throughout the four seasons.

Note that the present invention can be applied to, for example, a device for preventing the adhesion of marine organisms.

Next, an embodiment of the method of the present invention will be explained based on the drawings.

FIG. 4 shows this embodiment.

In the figure, 1 is a seawater inlet pipe, and 2 is a seawater temperature detector installed at an appropriate location in the seawater inlet pipe 1.

Reference numeral 3 denotes a seawater electrolyzer, to which a seawater inlet pipe 1 and an electrolyzed seawater outlet pipe 4 are connected, and an insoluble anode 5 for electrolysis is installed inside. Insoluble cathode6. and a current conduction line 8.9. In addition, the electrolytic positive 5 is made by coating a titanium base material with a noble metal such as platinum, ruthenium, or radium oxide.

The cathode 6 is made of, for example, iron, stainless steel, STEROY C
(Haynes 5tellite Co, trade name) and other alkaline metals are used. 7 is a DC power source for electrolysis, and current conductors 8 and 9 connect the electrolytic formwork to 5°6.
,! :It is connected. JO is a current control device for controlling the electrolytic current, and 11 is a conductor for transmitting the output signal of the seawater temperature detector 2 to the current control device 10.

In the circuit configuration shown in FIG. 4, seawater is electrolyzed by the electrolytic electrodes 5 and 6 in the electrolytic cell 3, and hypochlorite ions are produced on the surface of the anode 5 by a reaction expressed by the quadratic equation.

Ol+ 011-m-〇jO-+ II++ e...
-(1) Conventionally, the production efficiency of primary chlorite ions (aZO-) is affected by seawater temperature as shown in Figure 1.

Seawater temperatures begin to gradually drop below 15°C.

A detailed study of this decrease in production efficiency shows that the time at which the production efficiency of Ct and O- begins to decrease varies depending on the seawater temperature, as shown in Figure 2.When the seawater temperature is 10℃,
One hour after the start of electrolysis, the current efficiency began to decrease, and 2
Steady state is reached after an hour. When the temperature reaches 8°C, it starts to decrease 20 minutes after the start of electrolysis and reaches a steady state in about 1 hour.

In this case, the current efficiency decreases by as much as 20% or more.

The example shown in Figure 2 is an example of a platinum-plated electrode, but this tendency depends on the electrolytic current density and the type of electrode.

It varies depending on the electrolytic cell structure (distance between electrodes, seawater flow rate, etc.).

Such a tendency is extremely problematic in practical terms.

However, does this phenomenon temporarily stop the electrolytic current?

The present inventors have discovered that this pattern of current efficiency decline can be reproduced by reducing the current density to an extremely low current density (usually less than 1A/dm2) and returning to the normal current again.

Therefore, the patterns of seawater temperature and current efficiency are stored in advance in the control circuit shown in FIG. By controlling the output of 7 and repeating the operation according to a program that once cuts off or lowers the electrolytic current, electrolysis with high current efficiency can be continued.

Focusing on the single-force electrolysis voltage, a decrease in current efficiency causes an increase in the electrolysis voltage, as shown in FIG. This increase in electrolysis voltage is based on the increase in anode potential. This increase in anode potential is determined by the following equation.

ΔE, >-147, cI 11. s (10△EC to E)
EA --(2) Here △l'; A: Increase in anode potential 1 to Ac; Electrolytic sliding voltage I; Electrolytic current n, s; Ohmic resistance between electrodes +>c; Cathode potential △Ec: Electrolytic current (2) The increase in cathode potential based on When the current efficiency is low, a low current efficiency occurs after a certain time, and FIG. 3 shows the relationship between the decrease in current efficiency and the increase in electrolytic voltage at this time. This voltage increase change is detected and compared with a predetermined voltage increase value (reference value). If it becomes larger than this value, the electrolytic current is temporarily cut off or the current is reduced to a low current value, and the specified voltage is returned to the specified value. Restoring current. This/-
Repeat the Kens. At this time, depending on the holding time, the operation of completely cutting off the electrolytic current may temporarily cause a current to flow in the opposite direction between the cathode and the anode, damaging the anode, so the preferred method is within a range where the reverse current does not flow. It is good to maintain the electrolytic voltage at .

In addition, for electrodes that respond sensitively to temperature drops and whose efficiency begins to decline within a few minutes, it is also possible to incorporate a control circuit in which the electrolytic current begins to drop and recover in seawater below a certain temperature. be.

FIG. 5 shows another embodiment of the method of the present invention, in which electrolytic voltage EA (detecting means 32° and electrolytic current detecting means 33 are added to the embodiment explained in FIG. 4) so that equation 2) holds true. Other configurations: seawater inlet pipe 21. seawater temperature detector 22. electrolytic cell 2:3. seawater outflow pipe 24. electrode for electrolysis 25
, 26° 1L Kaikawa DC power supply 27. Current conductors 28, 29.
Current control device; (0, the conducting wire 31 is the same as the device shown in FIG. 4. In such a control circuit, within the electrolysis current control device 30, an electrolysis voltage EAC detection means; . An arithmetic circuit corresponding to the above equation (2) is constructed using the seawater temperature detector 22 as an input signal to detect the increase ΔEA in the anode potential.

Control electrolytic current. The electrolysis DC power supply 27 combined with the electrolysis current control device 3o is of the slideac type, S OI
Existing products such as ＋, type, magnetic saturation reactor, one type, etc. can be applied.

Fig. 6 is a diagram showing an example of operation according to the method of the present invention, in which the electrolytic current is 320 A, 4 anode plates (270 x 8: 30 mm
l An example is shown in which a bipolar electrolytic cell with four cathode plates is operated at a temperature of 0°C.

The current reduction test is when the current is applied for 1 hour and the current is reduced by A for 3 minutes.Compared to the case where this test is not performed (dotted line in the figure), the result is extremely good, and the amount of chlorine generated is 1.
To obtain 35 kg/II, the electrolytic current could be reduced by about 20 coefficients. A decrease in electrolysis current also causes a decrease in electrolysis voltage, which can contribute to a reduction in power consumption.

The temperature dependence of electrolytic efficiency differs depending on the type of electrode, but the current conduction pattern during the current conduction period, decrease or stop period is -
Lee 1--old n7-\"--N- etc. need to be selected appropriately.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of the effect of seawater temperature on current efficiency, Figure 2 is a diagram showing an example of changes over time in current efficiency when seawater temperature is low, and Figure 3 is a diagram showing current efficiency and electrolysis. 4 is a block diagram showing one embodiment of the method of the present invention, FIG. 5 is a block diagram showing another embodiment of the method of the present invention, and FIG. 6 is a diagram showing the relationship with voltage rise. Operation 1 according to the method of the present invention
FIG. 3 is a diagram illustrating an example. 2.22...Seawater temperature detector, 3.2:3 Seawater electrolyzer, 5.25...Anode, 6.26 Cathode, 7゜2
7. DC power supply for electrolysis, 10.30... Current control device,
:32... Electrolysis voltage detection means, 33... Electrolysis current detection means. Increased water λh□18? ('Cn71 Figure 8% A"l (zusu) Left 2 figure 9'i 1,171 7.1'

Claims (1)

[Claims] In a method for producing chlorine or hypochlorite by electrolytically treating seawater using an electrolytic cell equipped with an insoluble electrode, 2. Intermittently or periodically reducing the electrolytic current flow during operation of the electrolytic cell. A method for producing chlorine or hypochlorite from seawater, characterized by: