JPS6029320B2 - Dust collection method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a dust collection method.

More specifically, dust collection water is used in dust collectors for exhaust gas discharged from blast furnaces, converters, freezing furnaces, etc., and in environmental dust collectors used for environmental purification in workplaces where dust and various reactive gases are present. The present invention relates to a dust collection method aimed at improving the performance of. It is economically undesirable to discharge the collected water used in exhaust gas dust collectors after one use, so it is normally used for circulation. However, if it is used for circulation as it is, scale will adhere to it and cause damage to pumps, piping, dust collectors, etc. This has the disadvantage of being blocked.

In order to eliminate such adverse effects, a thickener is installed in the circulation path of the collected dust water to coagulate and precipitate suspended substances in the collected dust water, and polyphosphates and relatively low molecular weight substances are added to the collected dust water. Attempts have been made to prevent scale adhesion by adding polyacrylic acid or its salts.

However, although polyphosphates are effective in preventing and dispersing scale precipitation, they are hydrolyzed during use to form orthophosphates and rapidly lose their effectiveness.

Moreover, the generated orthophosphate reacts with metal ions such as calcium ions, magnesium ions, and zinc ions dissolved in the dust collection water to form water-insoluble phosphates (calcium phosphate, magnesium phosphate, zinc phosphate, etc.). This forms and precipitates as crystal particles, which in turn promotes the formation of sludge and scale. In addition, polyphosphates can cause red glue to form in the ocean if dust water containing them is released. On the other hand, when polyacrylic acid or its salts are used, there are various factors such as the fact that they do not contain phosphorus, and that they are more effective than poly-IJ phosphates in preventing and dispersing scale precipitation in cooling water systems. Advantages are recognized. However, although a considerable amount of metal compounds are removed from the exhaust gas dust collection water through coagulation and precipitation treatment, when the dust collection water is treated with alkali, the iron and zinc hydroxides produced by the alkali treatment are Therefore, it does not settle sufficiently in the thickener and remains in the dust collection water.

In addition, the compounds formed by the reaction between carbon dioxide contained in the exhaust gas and metal ions in the dust collection water when they come into contact with the exhaust gas have considerable solubility in water, so they cannot be completely compensated for by coagulation and precipitation. can't be caught. If the dust collection water contains metal compounds such as hydroxides and carbonates, the polyphosphates, polyacrylic acids, or their salts that have been used so far do not always have a sufficient scale suppression effect. do not have. Therefore, there is currently a demand for the development of effective scale inhibitors in this field. In view of the current situation, the present inventors have conducted intensive research to develop a scale inhibitor that is effective in preventing and dispersing scale in collected dust water containing metal compounds. The inventors have found that this has particularly excellent effects, and have completed the present invention.

Therefore, an object of the present invention is to provide a dust collection method that causes very little scale adhesion even when the dust collection water contains metal compounds. That is, in the dust collection method of the present invention, the circulating water used in the dust collection device has a general formula (where n is an integer from 5 to 100).

) and the general formula (where R represents hydrogen or a methyl group, X represents hydrogen,
Represents a monovalent metal, a divalent metal, an ammonium group, or an organic amine group.

) and the repeating structural unit 'B}, in which the total amount of ■ and the total amount of legs are within the range of 5:95 to 60:40 by weight, and the block copolymer is added and recycled for use. It is characterized by:

The block copolymer used in the present invention has, for example, a general formula (where n is an integer of 5 to 100).

), and the general formula (wherein R represents hydrogen or a methyl group, and X represents hydrogen, a monovalent metal, a divalent metal, an ammonium group, or an organic amine), and represents a group.

) is polymerized using a polymerization initiator and further neutralized with an alkaline substance if necessary.

Polyethylene glycolyl monoallyl ether (1) is represented by the above general formula, and has an added mole number n of ethylene oxide of 5 to 100. Number of moles added n
When the number is less than 5, the effect of preventing scale precipitation and dispersing scale of the obtained block copolymer is not fully satisfied. On the other hand, when it exceeds 100, the copolymerization reactivity of such polyethylene glycoyl monoallyl ether is low, and a block copolymer that is effective in preventing scale precipitation and dispersing scale cannot be obtained. Polyethylene glycol monoallyl ether (1) can be synthesized by a known method of directly adding ethylene oxide to allyl alcohol using an alkali such as KOH or NaOH as a catalyst.

The (meth)acrylic acid monomer m) is represented by the above general formula, and specifically includes acrylic acid, methacrylic acid, and their -valent metal salts, divalent metal salts, ammonium salts, and Organic amine salts may be mentioned.

One or more of these can be used. The block copolymer used in the dust generation method of the present invention is
It is necessary that the weight ratio of the total amount of the repeating structural unit (1) to the total amount of the repeating structural unit (2) be within the range of 5:95 to 60:40.

Therefore, when producing a block copolymer, the charging ratio of polyethylene glycol monoallyl ether (1) and (meth)acrylic acid monomer (0) is determined by the repeating structural unit in the resulting block copolymer. The total amount of (2) and the total amount of the repeating structural unit [B} must be within the above ratio range. If the ratio is outside of this range, excellent performance cannot be achieved. In order to produce the block copolymer used in the present invention from polyethylene glycoyl monoallyl ether (1) and (meth)acrylic acid monomer m), it is sufficient to carry out copolymerization using a polymerization initiator.

Copolymerization can be carried out by methods such as polymerization in a solvent or bulk polymerization. Polymerization in a solvent can be carried out either batchwise or continuously, and the solvents used in this case include water,
Examples include lower alcohols, mixed solvents of water and lower alcohols, aromatic hydrocarbons, aliphatic hydrocarbons, ketone compounds, and ethyl acetate.

As the polymerization catalyst, various water-soluble polymerization initiators, peroxides, hydroperoxides, combinations of these and polymerization promoters, or azo compounds are used as solvents. The polymerization temperature is appropriately determined depending on the solvent and polymerization initiator used, but it is usually carried out within the range of 0 to 120 degrees. When water is used as a solvent, sodium hydrogen sulfite-oxygen may be used as a polymerization catalyst.

In this case, the polymerization is carried out by blowing oxygen gas or a mixed gas of oxygen and an inert gas into the solvent while adding sodium hydrogen sulfite to the solvent containing the raw material monomer, and adding 5 to 80 q.
This can be carried out by proceeding the polymerization reaction within the temperature range of C. The bulk polymerization is carried out within a temperature range of 50 to 150° C. using peroxide, hydroperoxide, an azo compound, or the like as a polymerization initiator.

When producing a block copolymer in this way,
Polyethylene glycol monoallyl ether (1) and (
The molecular weight of the block copolymer obtained depends on the charging ratio of the meth)acrylic acid monomer (m), the star of the polymerization initiator used, the polymerization temperature, the type and amount of the solvent in the case of polymerization in a solvent, etc. The molecular weight of the block copolymer used in the dust collection method of the present invention is not particularly limited, and a wide range of molecular weights can be used, but among them, those in the range of 500 to 50,000 are The effect is excellent.The block copolymer thus obtained can be used as it is in the dust collection method of the present invention, but it may be further neutralized with an alkaline substance if necessary.

Preferred examples of such alkaline substances include hydroxides, chlorides, and carbonates of monovalent metals and divalent metals, ammonia, and organic amines. Although the block copolymer used in the mulberry dust method of the present invention is sufficiently effective when used alone, it can also be used in combination with other known scale inhibitors, such as polyphosphates, if necessary.

Furthermore, it can also be used in combination with ordinary water treatment agents such as decontamination agents and slime control agents. In order to use the block copolymer in the dust collection method of the present invention, the block copolymer may be added continuously or at appropriate times to the dust collection water, and there are no particular restrictions on the method or timing of addition.

The dust collector, piping equipment, dust collecting water supply circulation method, etc. can be performed using known devices and methods. As an example of the dust collection method of the present invention, the following method can be mentioned.

However, the scope of the present invention is not limited by such examples. For example, when treating blast furnace exhaust gas, the blast furnace exhaust gas discharged from the top of the blast furnace is guided to a dust collector such as a venturi scrubber, where the exhaust gas and dust collection water are brought into contact and the dust in the exhaust gas is captured by the dust collection water. This collected water is led to a thickener, where the suspended matter is separated by precipitation, a block copolymer is added to the separated treated water, and the water is recycled again as dust collected water. The block copolymer used in the bonito collection method of the present invention is preferably added to a predetermined concentration from any position in the pipe that circulates the treated water precipitated and separated in the thickener to the dust collector. The amount added cannot be absolutely determined depending on the use, purpose, etc., but it is usually in the range of 0.1 to 10 times the amount of dust collected. According to the dust collection method of the present invention, even when the dust collection water contains metal compounds such as calcium, magnesium, iron, zinc, etc. or when the pH value of the dust collection water is high, the block copolymer works to pump the dust collection method. , can effectively prevent scale precipitation and scale dispersion in piping, dust collectors, etc.
Therefore, long-term operation is possible by circulating the collected dust water.

Additionally, due to long-term operation, dissolved metal compounds may condense and some scale may precipitate, but even in that case, the precipitated scale is soft due to the action of the block copolymer. , can be easily removed by a stream of water. Although it is not clear why the block copolymer used in the dust collection method of the present invention has such an excellent effect, the block copolymer is an anionic block having a carboxyl group and/or a salt thereof. It has two types of blocks with different properties in one molecule: a nonionic and hydrophilic block consisting of a polyethylene glycol chain, and it exhibits excellent performance due to the interaction of these two types of blocks. considered to be a thing.

However, the scope of the present invention is not limited by this reason. In addition, this block copolymer has a polyethylene glycol chain, which is a nonionic and hydrophilic block, and is bonded to an anionic block, which is the primary mirror of the copolymer, through an ether bond, so it can be used under high temperature or boiling water. Alternatively, even when used for a long period of time in a high pH range, no hydrolysis occurs at all, and excellent performance can be maintained for a long period of time. Furthermore, since the block copolymer is a synthetic product, it has the advantage that it can be stably supplied with a constant quality compared to natural products. The present invention will be described below with reference to Reference Examples and Examples, but the present invention is not limited to these Examples.

In addition, unless otherwise specified in the examples, all parts are parts by weight.
All percentages are by weight. The viscosities of block copolymer aqueous solutions in the examples were all measured using a Bismetron viscometer (manufactured by Seiki Kogyo Kenkyujo) under conditions of 2yo and 6 pm.

Furthermore, the molecular weight was measured using gel permeation chromatography (Model 24, manufactured by Waters).
Reference Example 1 Polyethylene glycol monoallyl ether (containing an average of 1 solid ethylene oxide unit per molecule) was placed in a glass reaction vessel equipped with a thermometer, a rope strainer, a dropping funnel, a gas inlet pipe, and a reflux condenser. ) 30 parts and water 47
After charging 5 parts, the inside of the reaction vessel was purged with nitrogen under a vacuum, and heated to 9yo in a nitrogen atmosphere.

Then powder% sodium acrylate aqueous solution 447 parts and 5%
Four parts of an aqueous ammonium persulfate solution were added at one time each. After the addition was complete, 8 parts of a 5% ammonium persulfate aqueous solution was added at 2 parts. After the addition of the monomer-aqueous solution was completed, the temperature was maintained at 95 CO for 12 minutes to complete the polymerization reaction, and an aqueous solution of Copolymer 1 was obtained. The viscosity and molecular weight of this aqueous solution of Copolymer 1 were as shown in Table 1.

Reference Example 2 Into the same reaction vessel as in Reference Example 1, 70 parts of polyethylene glycol monoallyl ether (containing 1M solid ethylene oxide units per molecule on average) and 54 parts of water were charged,
The inside of the reaction vessel was purged with nitrogen under a rope sieve, and heated to 95 qo.

Then 342 parts of 38% sodium acrylate aqueous solution and 5
% ammonium persulfate aqueous solution 4 parts and 120 parts each
After the addition was completed, 8 parts of a 5% ammonium persulfate aqueous solution was added every 2 minutes. After the addition of the monomers was completed, the temperature was maintained at 9,500 ℃ for 120 minutes to complete the polymerization reaction, and an aqueous solution of copolymer 2 was obtained. The pH, viscosity, and molecular weight of this aqueous solution of Copolymer 2 were as shown in Table 1. Reference Example 3 Into the same reaction vessel as in Reference Example 1, 80 parts of polyethylene glycol monoallyl ether (containing an average of 2 solid ethylene oxide units per molecule) and 46 parts of water were charged,
The interior of the reaction vessel was purged with nitrogen under condensation, and heated to the boiling point in a nitrogen atmosphere.

Then 316 parts of 38% sodium acrylate aqueous solution and 5
% ammonium persulfate aqueous solution 12% and 12% each
It was added at the anchorage, and after the addition was completed, 24 parts of a 5% weekly ammonium sulfate aqueous solution was added in two portions. After the addition of the monomer aqueous solution was completed, the temperature was maintained at the boiling point for 120 minutes to complete the polymerization reaction, and an aqueous solution of copolymer 3 was obtained. This copolymer 3
The pH, viscosity, and molecular weight of the aqueous solution were as shown in Table 1. Reference Example 4 In the same reaction bath vessel as in Reference Example 1, 60 parts of polyethylene glycol monoallyl ether (containing an average of 3 solid ethylene oxide units per molecule) and 524 parts of water were charged, and the reaction was carried out under a rope pestle. The inside of the container was replaced with nitrogen and heated to 9yo.

Then, 1 part each of 368 parts of 38% sodium methacrylate aqueous solution and 40 parts of 5% ammonium persulfate aqueous solution was added.
After the addition was completed, 8 parts of a 5% aqueous ammonium persulfate solution was added over a period of 20 minutes. After the addition of the monomers was completed, the temperature was maintained at 980 °C for 12 minutes to complete the polymerization reaction, and an aqueous solution of copolymer 4 was obtained. The pH, viscosity, and molecular weight of this aqueous solution of Copolymer 4 were as shown in Table 1. Reference Example 5 Into the same reaction vessel as in Reference Example 1, 54 parts of polyethylene glycol monoallyl ether (containing an average of two ethylene oxide units per molecule) and 126 parts of inpropyl alcohol (hereinafter abbreviated as IPA) were charged. The inside of the reaction vessel was purged with nitrogen under the key, and heated to the boiling point in a nitrogen atmosphere.

Then 126 parts of acrylic acid, 2 parts of penzoyl peroxide
and 294 parts of IPA were added over 120 minutes, and after the addition was complete, an additional 0.4 parts of penzoyl peroxide was added at mA of
A mixture of 7 and 6 parts was added in two portions every 30 minutes. After the addition of the monomers was completed, the temperature was maintained at the boiling point of 12 mm to complete the polymerization reaction. Thereafter, complete neutralization was performed with an aqueous solution of caustic soda, and IPA was distilled off to obtain an aqueous solution of copolymer 5. The pH of this aqueous solution of copolymer 5,
The viscosity and molecular weight were as shown in Table 1. Reference Example 6 In the same reaction vessel as in Reference Example 1, 36 parts of polyethylene glycol monoallyl ether (containing an average of 2 ethylene oxide units per molecule) and 82 parts of a 20% aqueous sodium acrylate solution were added. 20% of the body mixed aqueous solution
and 2 of 12 5% ammonium persulfate aqueous solutions.
0% and 0% respectively, the inside of the reaction vessel was purged with nitrogen under the ocean, and heated to 95o0.

Thereafter, the remainder of the single island mixed aqueous solution and the catalyst solution were added in 12 parts each, and after the addition was completed, an additional 24 parts of 5%
Aqueous ammonium persulfate solution was added over 20 minutes. After the addition of the monomer mixed aqueous solution was completed, the temperature was maintained at 9530 °C for 120 minutes to complete the polymerization reaction, and an aqueous solution of copolymer 6 was obtained.
The pH, viscosity and molecular weight of this aqueous solution of copolymer 6 were
Shown in the table. Reference example 7 Add water 3 to the same reaction vessel as reference example 1.
00 parts was charged, the inside of the reaction vessel was imitated with nitrogen under the rope, and 95
heated to ℃.

Then, a monomer mixed aqueous solution of 4 parts of polyethylene glycol monoallyl ether (containing an average of 13 ethylene oxide units per molecule) and 516 parts of a 31% aqueous sodium acrylate solution and a 5% aqueous ammonium persulfate solution. Each of the 12 samples was added in 120 minutes. After the addition was complete, 24 parts of a 5% ammonium persulfate aqueous solution was further added over 20 minutes. After completing the addition of the monomer mixed aqueous solution, the temperature was maintained at 95 qo for 120 minutes to complete the polymerization reaction, and an aqueous solution of copolymer 7 was obtained. The pH, viscosity and molecular weight of this aqueous solution of Copolymer 7 are shown in Table 1. Table 1 (Note 1) The viscosity of a copolymer aqueous solution with a concentration of 40* (measured with a B-type viscometer, 25q○ 60 rpm) However, copolymer (
Only 51 was measured with a 45 shot concentration aqueous solution.

(Note 2) Measured using gel permeation chromatography.

Example 1 In a beaker, add 750 g of deionized water and 0.0 g of calcium chloride.
% aqueous solution of 50%, and 20% of the polymer 1 obtained in Reference Example 1.
Mix 50% of an aqueous solution containing QG on the table and 50% of a 0.44% aqueous solution of sodium hydrogen carbonate under the
．． After adjusting the pH to 8.5 with a 01N aqueous sodium hydroxide solution, deionized water was added to bring the total volume to 1,000 mL to prepare a 5-fold supersaturated aqueous solution of calcium carbonate at 2,500 mL.

This 5-times supersaturated aqueous solution was divided into four equal parts, each placed in a glass pin, the cap tightly closed, and the mixture was stirred at 60 qo.

The test liquid was taken out after 5 hours, after 2 hours, after 4 hours, and after cooling to 25 qo, the test liquid was poured into a quantitative furnace paper made by Toyo Paper Co., Ltd. Pass the furnace with strings and pray for atomic absorption (4
22.7 nm) to measure the concentration of calcium ions remaining in the test solution, and calculate the amount of precipitated calcium carbonate. The results are shown in Table 2. Examples 2 to 7 In Example 1, Reference Examples 2 to 7 were used instead of Copolymer 1.
The test was conducted in the same manner as in Example 1 except that Copolymers 2 to 7 obtained in Example 1 were used.

The results are shown in Table 2. Comparative Example 1 Example 1 except that commercially available polyacrylic soda (molecular weight 5000) was used instead of Copolymer 1.
In the same manner as above, the amount of precipitated calcium carbonate was investigated.

The results are shown in Table 2. Comparative Example 2 In Example 1, the amount of precipitated calcium carbonate was investigated in the case where English Polymer 1 was not used.

The results are shown in Table 2. Table 2 As is clear from the results shown in Table 2, the block copolymer used in the dust collection method of the present invention has an excellent effect on preventing scale precipitation of calcium carbonate.

Example 8 Put 180 μl of deionized water into a glass bottle, and add the copolymer 1 obtained in Reference Example 1 to the deionized water for 2 ps while stirring.
Then, 2.8' of a 5% aqueous sodium bicarbonate solution and 2.16' of a 1% aqueous zinc chloride solution were added, and further deionized water was added to bring the total volume to 2,002.

After standing still for 2 hours, transfer this test solution to Toyo Roshi Quantitative Furnace N.
o. The solution was heated in a heated oven, and the concentration of zinc ions remaining in the test solution was measured by atomic absorption spectrometry (21 points. m), and the amount of precipitated zinc compounds was calculated.

At the same time, the appearance was also observed. The results are shown in Table 3.
Examples 9 to 14 In Example 8, Reference Examples 2 to 7 were used instead of Copolymer 1.
A test was conducted in the same manner as in Example 8, except that Copolymers 2 to 7 obtained in Example 8 were used, respectively.

The results are shown in Table 3. Comparative Example 3 The amount of the precipitated zinc compound was investigated in the same manner as in Example 8, except that commercially available sodium polyacrylate (molecular weight 5000) was used instead of Copolymer 1.

The results are shown in Table 3. Comparative Example 4 In Example 8, the amount of zinc compound precipitated was investigated in the case where Copolymer 1 was not used.

The results are shown in Table 3. Table 3 As is clear from the results shown in Table 3, the block copolymer used in the dust collection method of the present invention has an excellent effect on preventing scale precipitation of zinc compounds.

Example 15 In the circulating water system for blast furnace exhaust gas dust collection water, a test short pipe (3/8 inch diameter, 15 mm length) was installed in the middle of circulating thickener treated water to the dust collector, and the same sample obtained in Reference Example 2 was installed. Polymer 2
0 for circulating water. The weight of the scale adhering to the test tube and its adhesion speed were measured by continuous operation for 30 days while adding the scale at the thickener outlet so as to obtain the concentration on the wall side.

The test conditions were as follows. The results are shown in Table 4.
Water temperature: 35-40COFlow rate: 1.5m/secPH
7-8 (No particular adjustment) Comparative example 5 Example 15 except that commercially available sodium polyacrylate (molecular weight 5000) was used instead of copolymer 2.
In the same manner as above, the weight of scale adhering to the short test tube and its adhesion rate were measured. The results are shown in Table 4.
Comparative Example 6 In Example 15, continuous operation was performed for 15 days in the case where English Polymer 2 was not added, and the amount and rate of scale adhesion were measured.

The results are shown in Table 4. Table 4 As is clear from the results shown in Table 4, the block copolymer used in the dust collection method of the present invention has an excellent effect on preventing scale precipitation in collected dust water during continuous operation.

Claims (1)

[Claims] 1. A repeating structural unit represented by the general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, in the formula, n is an integer from 5 to 100.) (A) and the general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, in the formula, R represents hydrogen or a methyl group, and X represents hydrogen, a monovalent metal, a divalent metal, an ammonium group, or an organic amine group. ) and the repeating structural unit (B) shown in (A
) and (B) in a weight ratio of 5:95 to 60:
A dust collection method characterized in that a block copolymer having a particle size within the range of 40 is added and recycled.