JPH11325796A - Manufacture of low potential reduced water and method for removing scale - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively remove a scale adhering to a heat exchanger, a boiler, a steam generator, a strainer, an equipment or the like and a rust by using a reduced water containing a pure water as a base and exhibiting specific values of a conductivity and an oxidation-reduction potential containing no heavy noble metal. SOLUTION: A pure water having a conductivity of 1 μS/cm or less is filled in a tank 8, and an electrolyte (hydrazine) is added to set a water quality of pH of the water to 8 to 9 by an operation of an AC high frequency electrolytic unit 3. To approach the water to an initial low potential and to remove a dissolved oxygen, a hydrogen or a nitrogen is injected by a bubbling unit 6. Thus, a water having an oxidation-reduction potential of (-) 400 mV or less is obtained. Further, it is lowered to a low potential oxidation-reduction potential of (-) 700 to 800 mV by the unit 3 and a specific electrode 4 to make the water cluster. The thus prepared pure water is passed through a heat exchanger, a boiler, a strainer or the like to effectively remove a scale adhered to them or rust or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention does not reduce the oxidation-reduction potential of general industrial water and removes rust and the like, but pure water widely used in steam generators such as equipment, heat exchangers and electric power. Based on the above, the scale (magnetite, hematite) of the equipment of the steam generator treated with water is maintained at an oxidation-reduction potential (-) of 400 mV or less, and p is circulated or immersed.
The scale is removed at H8 to H9. The present invention also relates to a method of holding alkaline water in addition to the generation and holding of these optimum low potentials.

[0002]

2. Description of the Related Art Conventionally, scale attached to a heater, a boiler, a steam generator, or the like has been removed by a dissolution treatment using an acidic solution or a physical method using ultra-high pressure water.

[0003] Removal by an acidic solution has a high scale removal capability, but causes dissolution of the base material by an acid.

[0004] Generally, in order to prevent corrosion by acid, an alkali cleaning or neutralization cleaning step is used. If the washing and removal of the acid after the acid treatment is incomplete, a small amount of the remaining acid enters the gap and the like, is locally concentrated, and local corrosion of the portion occurs.

Further, the water treatment after the treatment contains many substances using an organic acid, and a large-scale wastewater treatment is required.

[0006] Physical removal by high-pressure water is most suitable for removal of relatively soft scale, but cleaning of small-cavity equipment such as a thin tube such as a steam generator or a strainer requires partial removal. Except in many places where high-pressure water cannot be applied, it is difficult to completely remove the scale of the target equipment.

[0007]

SUMMARY OF THE INVENTION Scale (magnetite, hematite) generated by water treatment based on pure water
This is a method of removing scale by using only water without acid mixing with chemicals, high pressure, washing and mechanical removal.

[0008] General industrial water that uses the potential of water at normal temperature and normal pressure without using chemicals even with water alone has (+) 300.
~ 600mV, and if it is pure water, (+) 150mV ~
In the range of 250 mV.

Using general industrial water, low potential (-) 4
The voltage can be reduced to 00 mV or less, and the material for the electrode for lowering the potential is not limited, and rust can be removed.

Pure water is used to remove heat exchangers and steam generators whose water quality is controlled by pure water-based equipment, and scales of strainer piping and the like attached thereto. The scale is removed at a potential (-) of 400 mV or less.

Equipment using pure water requires a corrosion-resistant electrode made of a material that does not elute impurities or heavy noble metals. In this method, a low potential is generated and maintained in alkaline water, and scale is removed by continuous circulation or the like.

[0012]

In order to solve the above-mentioned problems, in the invention of the present application, means for lowering the reduction potential and circulation of low-potential pure water, the amount of the pure water is kept constant, ,
Circulate through equipment to remove scale (magnetite, hematite) (see figure).

Further, in order to prevent corrosion of equipment and the like, pure water is maintained in an alkaline state of pH 8 to 9 and continuously operated for a long time (4 to 10 days depending on the scale) while maintaining a reduction potential. Remove scale.

In order to reduce the oxidation-reduction potential to (-) 400 mV or less, an AC reducer is used rather than a DC reducer, and the electrode has a low potential by combining diamonds (special dimensions) or plates having a special structure. ((-) 700 to 800 mV) and could be maintained for a long time.

Further, platinum, inconel, and SUS materials which can be reduced to pure water at a low potential were used as materials from which heavy noble metals are hardly eluted even when the potential is lowered.

Pure water has a conductivity of 1 μS / cm or less, and is used for bubbling with hydrogen gas or nitrogen gas at a constant flow rate to rapidly reduce the concentration of dissolved oxygen. At this time, use an AC reduction device at the same time
A power of 00 W to 400 W is supplied to make the reduction a continuous operation.

The circulation of the pure water is performed in the range of 1,200 liters to 3,600 liters / H per electrode, and the dissolved oxygen concentration is desirably set to 2 ppm or less.

Next, a very small amount of electrolyte is added (in the demonstration test, pure water and hydrazine are used to prevent equipment corrosion), and the conductivity is increased to about 2 μS / cm.

At this point, the pure water is in an alkaline state, and by continuously operating the AC high-frequency reduction device, the pH becomes 7 to 7.
8. The reduction potential (-) can be maintained at 400 to 500 mV, and the continuous circulation flow rate can be maintained.

Further, in order to produce scale-controlled water with pure water in order to produce water having a low redox potential suitable for the purpose, the amount of electrolyte to be added is increased, and energy is added by AC high-frequency reduction. Circulate water.

In the demonstration test, a scale equivalent to that of a supercritical boiler or a steam generator was used. Low redox potential (-) 700 to (-) 800 mV
I was able to.

In this state, it was confirmed that scale (magnetite, hematite) and general rust were also removed.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Water quality based on pure water pH 8 to
In order to make the water to which the electrolyte (hydrazine) was added to 9 the initial low potential, hydrogen bubbling or nitrogen bubbling was performed to remove dissolved oxygen. As a result,
Water with an oxidation-reduction potential (-) of 400 mV or less can be obtained in a short time. Further, the pure water is made into clusters by lowering the low potential oxidation-reduction potential to (−) 700 to 800 mV by the AC high-frequency electrolysis device and the special electrode. In this state, the scale can be removed.

[0024] Descaling is all possible if it is carried out with acidic water, but it is also possible to neutralize acid pickling and possibly corrode the metal. Therefore, as a feature of this, low potential, reduced water (−) 700 to 80 while maintaining an alkaline state of pH 8 to 9
Scale can be removed from 0 mV and water by the cluster state.

The traffic high-frequency reduction device uses a power supply of 100 V, the volume of water and the amount of water circulation are 0 to 3,600 liters / H / electrode, and the pH, low-potential reduction current and voltage are set. Another feature is that low potential reduction can be maintained.

[0026]

EXAMPLE The following shows the results of the production of alkaline low-potential reduced water and the accompanying high-grade removal of magnetite and hematite by using pure water with the apparatus and equipment described above.

Pure water having a conductivity of 1 μS / cm or less is
The circulation volume is set in the range of 2,000 liters to 3,000 liters / H with a circulation pump in a water tank of 1 to 300 liters.

Using an AC high-frequency electrolyzer, the electrodes are T
A special structure using i and Pt materials is used, and 100 W to 200 W is used for the above water circulation amount.

Since even pure water contains dissolved oxygen, hydrogen gas or nitrogen gas is added to a porous tube at 0.1.
Bubble in the range of 1 to 0.5 liter / min.
It is desirable to keep the dissolved oxygen concentration at 2 ppm or less.

Next, a very small amount of electrolyte (in this case, hydrazine was used to make alkaline water) was added, and the pH was adjusted to pH 8-9.
In this range, we tried to prevent corrosion of equipment. <Reference> In the case of water modified by acid (patent applied), descaling can be performed in a short time by adding nitric acid or citric acid to make it acidic.

According to the above-mentioned procedure, the potential is lowered to the oxidation-reduction potential of about -400 mV. In order to cluster the lower reduction potential and pure water into clusters, the AC high-frequency electrolyzer is operated to lower the reduction potential to a reduction potential suitable for the purpose of use. For example, for the purpose of not increasing dissolved oxygen,
By adding 0 ppm, the efficiency of AC high-frequency reduction increases (however, it is confirmed that the circulation amount of pure water is continuous and the pH is not changed to 8 to 9).

Thus, the oxidation-reduction potential (−) is 600 mV
The following low-potential water could be prepared.

The water is circulated while holding a sample of magnetite and hematite, such as a supercritical pressure boiler / water tube scale and a scale generated in water quality control, and general equipment such as water. In this state, pH 8-9 potential (-) 700
By maintaining mV or more, removal of scale was confirmed in several tens of hours.

The drainage of water, which is another characteristic, depends on impurities due to scale removal, but since water is pure water and does not use any chemicals, drainage treatment is easy and handling is easy.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing an example of equipment used for implementing the present invention.

FIG. 2 is a system configuration diagram showing another example of equipment.

[Reference Numerals] descaling equipment such as a pump (if the self-pressure variable in one pump) electrolyzer special electrode bomb bubbler meter, redox potential meter, pH meter, O ₂ meter, conductivity meter, thermometer Aquarium

Claims (3)

[Claims] 1. An oxidation-reduction potential not containing heavy precious metals under the condition of a conductivity of about 1 μS / cm based on pure water from industrial water (including distilled water, reverse osmosis membrane, and water) having a value of (−) 40.
A method for removing rust from scales attached to heat exchangers, boilers, steam generators, strainers, equipment, etc. using reduced water of 0 mV or less. 2. A method of reducing low-potential reduced water (-400 mV or less) for removing scale as described above. 3. The scale is removed in a reducing atmosphere in which pure water is made alkaline (pH 8 to 9).