JPS61143587A - Prevention of marine life sticking to sea water piping - Google Patents

Abstract

PURPOSE:To prevent effectively sticking of the marine life to sea water piping by fixing one end of an electrode body to the inside wall of the sea water piping near an intake part and electrolyzing the sea water to form sodium hypochlorite. CONSTITUTION:One end of the electrode body 1 consisting of a pair of water permeable belt-like electrodes embedded into a water permeable spacer in an intake installation for the sea water is bolted between flanges 5 and 5' of the sea water piping 4 via insulating gaskets 2, 3. The body 1 is further spirally disposed along the inside wall of the sea water piping 4 and is properly adhered and fixed to the inside walls at optional points. Electricity is conducted to a pair of the electrodes of the body 1 to form the sodium hypochlorite by the electrolysis of the sea water in the sea water piping 4. The quantity of the electricity to be impressed to the electrodes is controlled in this stage to maintain the concn. of the sodium hypochloride near the inside wall 4 within the range necessary for preventing the sticking of marine life.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention prevents the adhesion of marine organisms to seawater piping by generating hypochlorite (I-IJ) by direct electrolysis of seawater in seawater piping. Regarding the method.

[Prior art]

Conventionally, a large amount of seawater has been used as cooling water in thermal power plants, nuclear power plants, steel plants, chemical factories, etc., and as a heat medium for LNG vaporization, and the amount used is increasing year by year.

However, when seawater is used as cooling water, it is well known that marine organisms such as shellfish can adhere to seawater piping and heat exchangers, resulting in decreased thermal efficiency, increased pressure loss, etc. Not only does this increase consumption, but it also causes so-called deposit attack, erosion caused by vortex generation, and sulfide ions (
Various types of corrosion problems occur due to the occurrence of S:).

Therefore, in order to prevent the adhesion of marine organisms, (]) a method of blowing chlorine gas into seawater, (2) a method of injecting sodium hypochlorite into seawater, and (3) a seawater electrolysis method have been adopted. was.

Method (1) is the oldest method used,
Hypochlorous acid, which is produced when chlorine gas reacts with water, is said to be effective in removing marine organisms, especially young fish.

However, in addition to being regulated as a high-pressure gas, chlorine gas is highly toxic, so care must be taken to prevent leaks at all stages of storage, transportation, and injection operations. Currently, it is rarely used because the hydrochloric acid produced makes seawater acidic.

Method (2) appeared in place of method (1), but since sodium hypochlorite is usually traded as a 10-15% aqueous solution, the transportation cost per unit of available chlorine is high. Furthermore, there was a problem in that it could not be stored for a long time because it self-decomposed.

Therefore, the method (3) was developed as an improvement to method (2).
) method.

In this method, a portion of the seawater used is diverted, electrolyzed, and chlorine gas generated at the anode reacts with caustic soda generated at the cathode to form seawater containing sodium hypochlorite. This method involves injecting seawater into seawater piping to bring the concentration of sodium hypochlorite to approximately 1 ppm.

This seawater electrolysis method is superior in terms of safety and economy compared to methods (11 and (2)), and is currently widely adopted worldwide.

However, even when sodium hypochlorite is discharged into seawater through the terminal discharge pipe, a concentration of approximately 0.1 ppm of sodium hypochlorite remains, and this has an adverse effect on fish and shellfish in the sea area near the discharge pipe. There were some drawbacks.

In addition, this method requires the installation of separate electrolysis equipment to electrolyze the separated seawater, and the energy consumption associated with this, such as pump power, cannot be ignored, and further improvements have been desired.

[Purpose of the invention]

The present invention further improves the method (3) above, and generates sodium hypochlorite by electrolyzing seawater directly in seawater piping, so there is no need to install electrolysis equipment, and energy consumption is minimized. The present invention provides a method for preventing marine organisms from adhering to seawater piping.

[Structure of the invention]

The present invention achieves the above object by attaching one end of an electrode body consisting of a pair of water-permeable strip electrodes embedded in a water-permeable spacer to a flange of a seawater pipe near the water intake part by tightening bolts. It is characterized in that it is adhered and fixed in a spiral shape along the inner wall of the seawater pipe, and electricity is supplied to the pair of electrodes of the electrode body to generate sodium hypochlorite by electrolysis of seawater.

FIG. 1 shows the installation of the electrode body at least at the flange portion of the seawater piping near the seawater intake portion according to the present invention.

That is, one end of the electrode body 1 is bolted between the flange portions 5.5'' of the seawater pipe 4 via the insulating backings 2 and 3.

Furthermore, the electrode body 1 is arranged in a spiral along the inner wall of the seawater pipe 4, and is appropriately bonded and fixed to the inner wall at arbitrary points.

The length of the electrode body 1 can be arbitrarily determined, and the other end may be free, but it is preferable that it be similarly fixed by bolting at the next flange.

As shown in FIG. 2, the electrode material 1 consists of a pair of opposing band-shaped electrodes 6 and 7- embedded in a spacer.

- Therefore, the distance between electrode 6 and electrode 7 is equal to the thickness of the spacer between these electrodes.

The electrodes 6 and 7 are made of a net-like or woven material and are water-permeable and flexible, and the electrode material may be platinum, but carbon fiber is preferably used from an economic standpoint.

However, carbon fibers with a low degree of graphitization have high electrical resistance and are easily damaged when chlorine gas is generated, so carbon fibers with a degree of graphitization of 80% or more are more preferable, and carbon fibers with a degree of graphitization of 90% or more are more preferable.
% or more of carbon fiber is most preferred.

These electrodes 6 and 7 can be used as either an anode or a cathode, but since the cathode has a low hydrogen generation potential, most ordinary metal materials can be used as the cathode.

Therefore, one of the electrodes constituting the electrode body 1 can be made of a net or woven fabric made of metal fibers.

Regarding the current density at the electrode, if the amount of current per electrode area (current density) is too large, the area of the electrode will be small, but various overvoltages will increase, the voltage between the electrodes will increase, and the electrode will wear out rapidly. , the electrolytic efficiency also decreases.

On the other hand, if the current density is made too low, a large electrode area will be required.

The current density in the present invention is usually 0.1 to 30 A/
Do? It is preferably in the range of 1 to IOA/d resistance.

The spacer 8 is insulating and is usually made of polyethylene.
Synthetic fiber materials that can withstand chlorine gas and sodium hypochlorite, such as polypropylene, polyvinyl chloride, and polytetrafluoroethylene, are used, and like the electrodes, they are mesh-like or woven-fabric-like and have water permeability.

The spacer 8 has the function of preventing contact and short circuit between the electrodes 6 and 7.

Note that the insulating backings 2 and 3 may be made of any material as long as it is insulating.

After bolting the 5.5" flange and fixing the electrode to the flange of the piping, apply sealant near the flange to prevent seawater from entering the flange for waterproofing. is preferable.

Figure 3 shows a case in which the electrode body is fixed at multiple positions in the seawater piping, and each of the electrode bodies shown in Figure 1 is also fixed at multiple flanges at arbitrary distances, including the seawater intake area. The electrode bodies 1.1a, 1b are fixed in the same manner as in the case.

In this case, it is possible to maintain the sodium hypochlorite produced at each electrode at an appropriate concentration near the inner wall of the seawater pipe, and therefore the hypochlorite in the seawater discharged from the terminal discharge pipe can be maintained at an appropriate concentration. It is possible to reduce the concentration of sodium chloride and prevent pollution of nearby sea areas.

In the present invention, the electrolytic reaction when electricity is applied to the pair of electrodes included in the electrode body is similar to the conventional seawater electrolysis method (3).

That is, to explain based on FIG. 1, seawater is introduced in the direction of arrow A, and when electricity is applied to electrodes 6 and 7, hydrogen gas is generated at the cathode according to the following equation (1), while at the anode, ( 2) Chlorine gas is generated according to the formula.

12 H+ 2 e-1--→H2(t)2CIC12+
2e(2) Chlorine gas generated at the anode reacts with caustic soda produced as a by-product at the cathode according to equation (3) below, and sodium hypochlorite (NaC10) is generated.

2NaOH+CI −→ NaC10+NaC1(3
) Note that the cathode side of the electrode body 1 tends to become alkaline due to the generated caustic soda.

In this case, calcium hydroxide and magnesium hydroxide may be generated near the cathode due to calcium and magnesium ions present in the seawater, but in the present invention, the cathode and anode are separated for an appropriate time. By switching, hydroxide near the cathode can be removed.

In addition, although the anode normally consumes more than the cathode,
In order to reduce the current density and prevent anode wear, anode wear can be avoided by using an electrode body in which the anode has a larger area than the cathode, or an electrode body consisting of multiple anodes. .

〔Effect of the invention〕

As described above, according to the present invention, sodium hypochlorite is generated by electrolysis of seawater in seawater piping.
Unlike conventional methods, separate seawater electrolysis equipment for producing thorium hypochlorite is not required, and energy consumption can be significantly reduced.

In addition, water-permeable strip electrodes 1 and 2 facing each other as electrode bodies are provided.
Since a water-permeable spacer is interposed between these electrodes, the reaction of equation (3) above between the chlorine gas generated at the anode and the caustic soda produced as a by-product near the cathode proceeds quickly, and the electrode Extreme pH differences in the vicinity are prevented, and hypochlorous acid produced by seawater is constantly removed.
Jum can be carried out in the direction of seawater flow.

Therefore, an increase in the concentration of sodium hypochlorite near the inner wall of the seawater pipe is prevented, the corrosive environment for the pipe material is made mild, and the overall power efficiency can be kept high.

Also, since the distance between the electrodes is maintained at the thickness of the spacer,
Electrolysis efficiency can be greatly increased.

Additionally, sodium hypochlorite is usually injected to an average concentration of about 1 ppm to prevent marine organisms from adhering to the pipes.

However, according to the present invention, the electrode body is arranged along the inner wall of the seawater pipe, and sodium hypochlorite is formed near the inner wall, so by controlling the amount of electricity applied to the electrode, the hypochlorite near the inner wall is The concentration of sodium chlorate is maintained within the range necessary to prevent the attachment of marine organisms, and the concentration of sodium hypochlorite remaining in the discharged seawater at the end is reduced as much as possible to inhibit the growth of fish and shellfish in the sea area near the discharge pipe. It can be prevented.

〔Example〕

Graphite fiber cloth with a degree of graphitization of 99% and a thickness of 0.
1. Using a 5mm+ polyethylene net. A tape with the configuration shown in Figure 2 was manufactured, and the ends were treated to form an electrode pair.
Closed.

The width of the tape was approximately 1 co+, the length was 30 cm, and the effective electrode area was 3M.

This was attached to the inner surface of a transparent PVC pipe with an inner diameter of 5 CI and 11% and a length of 30 cm (since the pipe diameter was small, it was not wound in a spiral shape, but rather linearly along the inner wall of the pipe), and both ends were fixed with flanges.

Prepare simulated seawater 1i containing about 3% NaC1, and
It was circulated through the piping system in which the above electrode pair was installed at a flow rate of EC.

Terminal voltage at various current densities, NaCl after 1 hour
The current efficiency and power consumption per 101 kg of NaC were estimated and summarized in the table below.

This table shows that according to the method of the present invention, NaC10
It is clear that the occurrence of

(Hereinafter, this page margin) Current density 20 10 5 1 (A/d
n? ) NaC10 concentration after 1 hour (ppm, ) 375 204 10
8 24 terminal voltage 5.7 4.5 3.8
3.2 Power consumption (KWH/Kg, NaCl0) 9.12 6.6
2 5.28 4.03

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing how the electrode body is fixed at the piping flange in the present invention, Fig. 2 is a schematic perspective view showing the structure of the electrode body according to the present invention, and Fig. 3 is a diagram showing another fixing situation of the electrode body. FIG. 1--electrode body, 6.7-electrode, 8.8'--spacer.

Claims (1)

[Claims] One end of an electrode body consisting of a pair of water-permeable strip electrodes embedded in a water-permeable spacer is attached to at least the seawater pipe flange near the water intake section by bolting, and the electrode body is spirally wound along the inner wall of the seawater pipe. 1. A method for preventing the adhesion of marine organisms to seawater piping, comprising: adhering and fixing the electrode body in a shape, and applying electricity to a pair of electrodes of the electrode body to generate sodium hypochlorite by electrolysis of seawater.