JPH05123697A - Method for preventing scaling in equipment for dissolving inorganic bleaching powder - Google Patents

Abstract

PURPOSE:To prevent the formation of calcium scale in an equipment for dissolving inorg. bleaching powder attached to an equipment for treating water. CONSTITUTION:A polyphosphoric acid compd. is added to water in which inorg. bleaching powder is dissolved. By this addition, the formation of scale in an equipment for dissolving inorg. bleaching powder is prevented, scale removing work is considerably relieved and the maintenance and control of an equipment for treating water are facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scale prevention method for an inorganic bleaching powder melting facility, and more specifically, for producing a calcium scale in an inorganic bleaching powder melting tank of an inorganic bleaching powder melting facility and a pipe thereafter. A method for preventing adhesion.

The present invention is preferably applied to inorganic bleaching powder dissolving equipment such as sterilizing and disinfecting equipment and bleaching equipment using an aqueous solution of calcium hypochlorite in which inorganic bleaching powder is dissolved in water.

[0003]

2. Description of the Related Art Conventionally, chlorine or hypochlorite has been used for water treatment such as tap water, pool water, wastewater treatment facilities and human waste treatment facilities, sterilization of cooling water of machinery and slime control. A method of injecting an aqueous solution of an acid salt is adopted, and as one method, an inorganic bleaching powder dissolving equipment is attached to a water treatment equipment, and the inorganic bleaching powder is dissolved in water to produce an aqueous solution of calcium hypochlorite. , A method of injecting into a water treatment facility is known.

[0004]

In the above-mentioned inorganic bleaching powder dissolution equipment, the high concentration of calcium in the aqueous solution of calcium hypochlorite obtained by dissolving the inorganic bleaching powder in water causes the inside of the dissolution tank and the hypochlorite to become high. In the discharge pipe of the calcium acid aqueous solution, calcium scale containing calcium carbonate as a main component was generated and adhered, which deteriorated the flow of the calcium hypochlorite aqueous solution and seriously caused obstacles such as clogging of the pipe.

As a countermeasure against these obstacles, a method of regularly dissolving and removing the calcium scale generated in the inorganic bleaching powder dissolving tank or in the discharge pipe of the aqueous solution of calcium hypochlorite by using hydrochloric acid has been adopted. However, there are problems to be solved, such as generation of highly toxic chlorine gas due to the reaction between calcium hypochlorite remaining in the calcium scale and hydrochloric acid, and corrosion of the device by hydrochloric acid.

The present invention, as a means for solving the above-mentioned problems of the apparatus for dissolving inorganic bleaching powder, prevents the generation and adhesion of calcium scale inside the tank for bleaching inorganic bleaching powder and the discharge pipe of calcium hypochlorite aqueous solution. The purpose is to provide a method.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that the dissolution of inorganic bleaching powder in water containing a polyphosphate compound suppresses the formation of calcium scale. Further, they have found that the produced calcium scale hardly adheres to the dissolution tank, piping, etc., and have completed the present invention.

The present invention is a method for preventing scale in an inorganic bleaching powder dissolving facility, which comprises dissolving an inorganic bleaching powder preparation with water containing a polyphosphoric acid compound.

The present invention will be described in detail below.

In the present invention, the equipment for dissolving inorganic bleaching powder is filled with an inorganic bleaching powder formulation inside, dissolving the inorganic bleaching powder formulation by introducing water, and discharging the aqueous solution of calcium hypochlorite. Any equipment may be used as long as it has a tank as the center of its constitution, and there are no particular restrictions on the detailed structure of the dissolution tank, the dissolution process, the water treatment equipment attached with this equipment, and the like.

(Inorganic Bleaching Powder Formulation) An inorganic bleaching powder formulation is a tablet, granule, or tablet of a composition containing calcium hypochlorite as a main component.
It is a preparation of any dosage form such as a powder. Normally, advanced bleaching powder (calcium hypochlorite / anhydrous salt, dihydrate, trihydrate), 60%
Various dosage forms of advanced bleaching powder and their blended compositions are commercially available, and any of them can be used. Further, two or more kinds having different dosage forms may be used in combination.

(Polyphosphoric acid compound) Polyphosphoric acid compounds include tripolyphosphoric acid, hexametaphosphoric acid, metaphosphoric acid,
Metal salts such as pyrophosphoric acid, triphosphoric acid, trimetaphosphoric acid and tetrametaphosphoric acid, preferably sodium salts or potassium salts. The water containing a polyphosphoric acid compound contains at least one kind of the polyphosphoric acid compound, and polyphosphoric acid having any dosage form such as tablets, granules and powders containing at least one kind of the polyphosphoric acid compound as a main component. It is obtained by injecting an aqueous solution of a polyphosphoric acid compound in which an acid compound preparation is dissolved in water into the water introduced into the tank for dissolving inorganic bleaching powder.

(Polyphosphoric acid compound preparation) As the polyphosphoric acid compound preparation, a polyphosphoric acid compound alone or a mixture system of a polyphosphoric acid compound and an excipient such as a dissolution rate adjusting agent, a binder and a lubricant is used. It Examples of the dissolution rate adjusting agent that is an excipient of the mixture-based preparation include metal stearates such as calcium stearate, magnesium stearate, and sodium stearate, stearic acid, fine powder of silicic acid, and fine powder of calcium silicate. Water-soluble polymers such as polyethylene glycol and polyvinylpyrrolidone, carboxymethyl cellulose, sodium alginate, boric acid and the like are used as binders, and calcium stearate, magnesium stearate, talc and the like are used as lubricants.

A method for dissolving a polyphosphate compound preparation in water,
There is no particular limitation on the method of injecting the polyphosphoric acid compound aqueous solution into the introduced water of the inorganic bleaching powder dissolving tank, and the water is introduced into the container filled with the polyphosphoric acid compound formulation to dissolve the resulting polyphosphoric acid compound aqueous solution. It is possible to employ a very general method of injecting into the introduction water pipe of the inorganic bleaching powder dissolving tank by utilizing a pump or a head difference.

The amount of the polyphosphoric acid compound introduced into the inorganic bleaching powder dissolution tank is 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, relative to 100 parts by weight of the inorganic bleaching powder preparation dissolved in the inorganic bleaching powder dissolution tank. Is the range. If the amount of polyphosphoric acid compound introduced into the inorganic bleaching powder dissolution tank is too small, the scale prevention effect will be insufficient, and if it is too large, the water introduced into the inorganic bleaching powder dissolution tank will be acidic and in the wastewater. It is not preferable because the phosphorus concentration of is increased.

[0016]

[Operation] As described above, the scale prevention method of the inorganic bleaching powder dissolution equipment of the present invention dissolves the inorganic bleaching powder preparation when the inorganic bleaching powder preparation is dissolved in water to produce a calcium hypochlorite aqueous solution. Therefore, the polyphosphoric acid compound is contained in the water introduced into the tank for dissolving the inorganic bleaching powder.

In the present invention, by dissolving the inorganic bleaching powder formulation with water containing a polyphosphoric acid compound, the surface potential of the calcium compound fine particles present in the obtained calcium hypochlorite aqueous solution is lowered, Of calcium compounds that cause scale formation such as calcium carbonate,
Adhesion to the inorganic bleaching powder solution dissolution tank and the subsequent calcium hypochlorite aqueous solution discharge pipe is prevented.

[0018]

[Examples] The present invention will be described in more detail with reference to Examples and Comparative Examples. However, the scope of the present invention is not limited by the following examples.

(1) Test Inorganic Bleaching Powder Dissolving Equipment The test inorganic bleaching powder dissolving equipment used in the examples (see attached FIGS. 1 and 2) is a 3 liter vinyl chloride inorganic bleaching powder dissolving tank: 1 liter polyvinyl chloride aqueous solution tank of polyphosphoric acid compound (Fig. 1) or polyphosphoric acid compound preparation dissolving tank (Fig. 2): 2, water injection pipe for introducing water into inorganic bleaching agent dissolution tank: 3, inorganic bleaching powder Outflow pipe for discharging the calcium hypochlorite aqueous solution from the preparation dissolution tank: 4, a perforated partition plate for holding the preparation in the dissolution tank: 5,
It consists of a connecting pipe: 6 for injecting the polyphosphoric acid compound aqueous solution into the water injection pipe.

(2) Samples of inorganic bleaching powder formulation: HC-1 to HC-3 The following inorganic bleaching powder formulations were used in Examples and Comparative Examples. HC-1: Nisso Hyklon 20g tablets (effective chlorine concentration 70% or more, manufactured by Nippon Soda Co., Ltd.) HC-2: Nisso Hyklon granules (effective chlorine concentration 70% or more, manufactured by Nippon Soda Co., Ltd.) HC- 3: 60% advanced bleaching powder (effective chlorine concentration of 60% or more, manufactured by Nippon Soda Co., Ltd.)

(3) Polyphosphoric acid compound preparation samples: PP-1 to PP-5 The following polyphosphoric acid compound preparations were used in the examples. PP-1: 20 g tablet obtained by compression-molding a mixture consisting of 100 parts by weight of sodium hexametaphosphate and 30 parts by weight of sodium alginate PP-2: 20 parts by weight of 10% polyvinylpyrrolidone aqueous solution was added to 100 parts by weight of sodium tripolyphosphate and kneaded. Granules obtained by extrusion granulation and drying were compression molded 20g Tablet PP-3: 40 parts by weight sodium hexametaphosphate, boric acid
20 g tablet obtained by compression-molding a mixture of 58 parts by weight and 2 parts by weight of calcium stearate PP-4: sodium hexametaphosphate granules PP-5: sodium tripolyphosphate powder

(4) Dissolution test (a) Test method-A The polyphosphoric acid compound aqueous solution tank of the test inorganic bleaching powder dissolution equipment (FIG. 1): 2 was filled with a polyphosphoric acid compound aqueous solution prepared by dissolving the polyphosphoric acid compound preparation in water. On the other hand, inorganic bleaching powder dissolution tank: 1
To the inorganic bleaching powder formulation and injecting water into the water injection pipe: 3 while injecting the prepared polyphosphoric acid compound aqueous solution through the connecting pipe: 6 to dissolve the inorganic bleaching powder formulation and to discharge the calcium hypochlorite aqueous solution outflow pipe. : 4 over the test piece: 7 continuously. Inorganic bleaching powder preparation dissolution tank: 1 and polyphosphoric acid compound aqueous solution tank: When the holding amount of the preparation or the aqueous solution to 2 was halved, the inorganic bleaching powder preparation was dissolved while supplementing each to the initial value. .. In addition, as a comparison, the inorganic bleaching powder preparation was dissolved under the same conditions except that the injection of the polyphosphoric acid compound aqueous solution was not performed. After the continuous test for 6 days, the state of adhesion of calcium scale to the inorganic bleaching powder dissolving tank: 1 and the outflow tube: 4, and the upper surface of the test piece: 7 was visually observed. Table 1 shows the test conditions and the results of visual observation.

(B) Test Method-B The polyphosphoric acid compound preparation dissolution tank of the above-mentioned test inorganic bleaching dissolution equipment (FIG. 2): 2 is filled with the polyphosphoric acid compound preparation and dissolved while introducing water to obtain polyphosphoric acid. A compound aqueous solution was continuously prepared. On the other hand, the inorganic bleaching powder dissolving tank: 1 is filled with the inorganic bleaching powder formulation, and the water injection pipe: 3 is injected while injecting the prepared polyphosphoric acid compound aqueous solution through the connecting pipe: 6 to dissolve the inorganic bleaching powder formulation, An aqueous solution of calcium hypochlorite was continuously made to flow down on the test piece: 7 through the outflow tube: 4. Four
After the continuous test for 8 hours, the state of adhesion of the calcium scale to the inside of the inorganic bleaching powder dissolving tank: 1 and the outflow tube: 4, and the upper surface of the test piece: 7 was visually observed. Table 1 shows the test conditions and observation results.

[0024]

[Table 1]

In Table 1, the feeding rate of the polyphosphate compound is
The value which calculated the supply rate of the polyphosphoric acid compound pure component from the supply rate of an aqueous solution is shown. In addition, the scale adhesion status indicates the following. ◯: Almost no scale is recognized. Δ: Slight peeling is observed, but peeling is easy. X: A large amount of scale is fixed, and peeling is difficult.

As shown in Table 1, when the inorganic bleaching powder preparation was dissolved in water containing a polyphosphoric acid compound, almost no scale was observed and a small scale was observed (Examples 3, 6 and 7), the generated scale was in a deposited state and could be easily removed with running water or the like. On the other hand, when the inorganic bleaching powder is dissolved using only water (see Comparative Example), a large amount of scale is produced, and the container,
It adhered to pipes, test pieces, etc., and was difficult to peel off by a mechanical method.

[0027]

INDUSTRIAL APPLICABILITY In the present invention, as described in detail above, by dissolving an inorganic bleaching powder preparation with water containing a polyphosphoric acid compound, scale adhesion to the inorganic bleaching powder preparation dissolving equipment is prevented. That is, by simply adding a facility capable of adding a polyphosphoric acid compound to the water injection pipe of the conventional inorganic bleaching powder formulation dissolution tank to the inorganic bleaching powder formulation dissolution tank, the frequent scale removal work becomes unnecessary. Or 1-2 years
It is reduced to about once. Therefore, it becomes extremely easy to maintain and manage the facilities such as the water treatment facility and the bleaching facility, which are equipped with the facility for dissolving the inorganic bleached powder formulation.

The present invention provides a scale prevention method for an inorganic bleaching powder melting facility, which facilitates the maintenance of various facilities attached to the inorganic bleaching powder melting facility, and its industrial, particularly water treatment field. Is extremely significant.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of the inorganic bleaching powder dissolution equipment used in the test method-A of the example.

FIG. 2 is a conceptual diagram of an inorganic bleaching powder dissolution equipment used in the test method-B of the example.

[Explanation of symbols]

1: Inorganic bleaching powder preparation dissolving tank, 2: Polyphosphoric acid compound aqueous solution tank or polyphosphoric acid compound preparation dissolving tank, 3: Water injection pipe,
4: Outflow pipe of calcium hypochlorite aqueous solution, 5: Perforated partition plate provided in the tank for dissolving inorganic bleaching powder formulation, 6: Connection pipe for sending polyphosphoric acid aqueous solution into the water injection pipe, 7: Test piece

Claims (5)

[Claims] 1. A method for preventing scale in an inorganic bleaching powder dissolution facility, which comprises dissolving an inorganic bleaching powder formulation with water containing a polyphosphate compound. 2. The inorganic bleaching powder dissolving equipment according to claim 1, wherein the content of the polyphosphoric acid compound in the polyphosphoric acid compound-containing water is 0.1 to 20 parts by weight per 100 parts by weight of the dissolved amount of the inorganic bleaching powder preparation. Scale prevention method 3. The method for preventing scale of an inorganic bleaching powder dissolving facility according to claim 1, wherein the inorganic bleaching powder formulation is a tablet, a granule and / or a powder. 4. The method for preventing scale of an inorganic bleaching powder dissolution facility according to claim 1, wherein the polyphosphoric acid compound formulation is dissolved in water and added to the water introduced into the inorganic bleaching powder formulation dissolution tank. 5. The method of preventing scale of an inorganic bleaching-dissolving facility according to claim 4, wherein the polyphosphate compound preparation is a tablet, granule and / or powder containing a polyphosphate compound as a main component.