JPH01225786A - Method for electrolyzing iron - Google Patents

Abstract

PURPOSE:To prevent the clogging between electrodes and a decrease in the current density by stopping electrolysis for specified hours in the method wherein the electrolytic current density on the electrode is enhanced, and the polarity of the electrodes is changed at regular time intervals to generate iron ion in seawater. CONSTITUTION:Seawater is introduced into an electrolytic cell 5 from a seawater inlet 7, and discharged from a seawater outlet 7. The parallel electrodes 3 and 4 are vertically set at some distance in the cell 5, and connected to a power source through conductive rods 1 and 2. The density of the current flowing through the electrodes 3 and 4 is controlled to a high current density of >=4A/dm<2>, the polarity of the electrodes 3 and 4 is changed at regular time intervals, and electrolysis is stopped for a surplus time spent for holding a high current density. Iron ion is generated in the seawater in the cell 5, discharged from an outlet 6, and utilized for preventing the corrosion of the condenser tubes, etc., of a thermal power plant. The deposition of scales on the electrode is prevented by this method, and the cell can be operated under low- load conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a low-load iron electrolysis method in which iron ions are injected into cooling seawater for corrosion prevention of condenser tubes and the like in thermal power plants.

[Conventional technology]

In the conventional iron electrolysis method, iron anodes and iron cathodes are placed in seawater and electrolysis is performed to generate iron ions in seawater.

[Problem to be solved by the invention]

In the conventional iron electrolysis method described above, electrolysis was performed without switching the polarity of the electrode, so z F e OO
H2M? (OH) and other scales adhered to the surface, causing a decrease in current efficiency for Fe ions over time, and clogging between electrodes, which could result in incomplete corrosion protection of the condenser tube. .

Therefore, prior to the present invention, Japanese Patent Application No. 62-206222 proposed an iron electrolysis method in which iron ions are generated in seawater by electrolysis using an iron positive electrode and an iron negative electrode placed in the sea, and the electrolytic current density was 4A/drr? The above, and
In the above-mentioned invention, which proposes an "iron electrolysis method characterized by switching the polarity of the electrode at regular intervals," the electrolytic current density at the electrode is set to 4A/drr? By using the above high current density and changing the polarity of the electrode at regular intervals, scales such as Fe and M-f compounds attached to the electrode surface are peeled off when it becomes an anode, and the scales are removed from the electrode surface. Scale build-up is reduced. For this reason, it has become possible to prevent a decrease in the current efficiency of iron electrolysis and blockage between electrodes due to scale, but it is also possible to reduce the accumulation of scale on the electrode surface and improve the current efficiency of iron electrolysis. There is a need for an iron electrolysis method that allows for low-load operation. Therefore.

If the current density is lowered to reduce the load, scale will adhere to the electrodes and electrolysis will stop.

[Failure to solve the problem]

In order to prevent scale from being deposited on the surface of the iron electrode, the present invention performs electrolysis at an electrolytic current density of 4 A/d or higher, switches the polarity of the anode and cathode at fixed intervals, and stops electrolysis for a fixed period of time. I decided to do so.

[For production]

By switching the polarity of the picture electrode and stopping electrolysis for an extra certain period of time due to maintaining the current density at a high current density, scale adhesion to the electrodes was prevented and low-load operation became possible.

〔Example〕

1 of the electrolyzer used when carrying out the method of the present invention
An example is shown in FIG.

The electrolytic cell 5 is provided with a seawater lower part at the top and a seawater outlet 6 at the lower part, and seawater enters the electrolytic cell 5 from the seawater lower part and flows out from the seawater outlet 6 as shown by the arrow in the figure.

Reference numerals 3 and 4 denote iron electrodes vertically provided in the electrolytic cell 5 in parallel with each other at intervals, and two current-carrying rods 1 and 2 are connected to each other.
Connected to power via.

In the case shown in the figure, electrode 3 is a positive electrode and electrode 4 is a negative electrode, but a switching device (not shown) makes it possible to switch between two electrodes 3 and 4.
By switching the polarity of 4 at regular intervals and maintaining the high current density, electrolysis can be stopped for an extra period of time.

In this device, iron ions are generated in the seawater in the electrolytic cell 5 by electrolysis, flowed out from the seawater outlet, and used for corrosion protection of condenser tubes, etc. of thermal power plants.

In the present invention, when iron ions are generated using the electrolytic device as described above, the current density flowing through the electrodes 3 and 4 is reduced to 4 A.
The current density was set at a high current density of /d m2 or more, the polarity of the electrodes 3 and 4 was changed at regular intervals, and the electrolysis was stopped only for the extra time when the current density was maintained at the high current density.

Table 1 shows the results of a test conducted using the apparatus shown in FIG. 1 in order to confirm the effects of the present invention.

The conditions under which this test was conducted are shown in Table 1.
The electrode area was 50 mm x 300 mm.

In the table, (1) to (3) are the conventional methods that do not switch the polarity of the electrodes, (4) and (5) are the previously invented methods that switch the electrodes, and (6) to (10) are the methods of the present invention. Invention method, (
11)' changes the polarity of the electrode and increases the current density by 3.
．． Comparative examples with 5A/d- are shown.

Table 1 The tatami indicates the electrolysis stop time (h).

As is clear from Table 1, according to the method of the present invention, the amount of scale deposited after one month is 1/10 that of the conventional method.
It was found that the current efficiency of iron electrolysis was significantly increased and could be maintained at 90% or higher.

In addition, for the comparative example (old), the current density was 3.5 A/d as described above.
The amount of scale deposited after one month is approximately 1.06 times that of the method of the present invention at a current density of 4 A/di, and when the current density is 4 A/dy or more, In some cases, it has been found that the amount of scale deposits is further reduced.

Further, according to the above test results, it was found that although sufficient effects can be achieved by stopping the electrolysis for about 1 hour, even better results can be obtained by stopping the electrolysis for 3 hours or more.

〔Effect of the invention〕

As described above, the present invention sets the electrolytic current density to 4 A/d- or more, changes the polarity of the iron electrode at regular intervals, and further stops electrolysis for an extra period of time while maintaining the high current density. Fe attached to the electrode surface when it becomes an anode
Scales such as and M1 compounds are effectively removed, and the amount of scale attached after one month is 1/10 compared to the conventional method.
The current efficiency of iron electrolysis is also 90%.
can be maintained above.

Therefore, in the present invention, it is possible to prevent the blockage between the electrodes, and the current efficiency of iron electrolysis can also be prevented from decreasing.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an example of an electrolytic device used in carrying out the present invention. 1.2... Current-carrying rod, 3, 4... Iron electrode, 5... Electrolytic tank, 6... Seawater outlet, 7... Seawater inlet.

Claims (1)

[Claims] In the iron electrolysis method, in which iron ions are generated in seawater by electrolysis using iron positive electrodes and iron negative electrodes placed underwater, the electrolytic current density is set to 4A/dm^2 or more, and the electrodes are removed at regular intervals. An iron electrolysis method characterized by switching the polarity of the iron and stopping electrolysis for a certain period of time.