Method of Preventing Dusts

(1) Field of the Invention

The present invention relates to a method of preventing dusts, such as coal powder, ore powder, fly ash, sand and the like.

(2) Description of the Prior Art

Dusts are apt to be developed during the transportation of coal, ore, fly ash, sand and the like, or at the place of storing these substances to pollute the environment.

In order to prevent dusts, water or an aqueous solution of a surface active agent is spread on the substances which develop dusts. However, water is evaporated with the lapse of time, and dusts develop again.

The inventors have made various investigations in order to prevent dusts and found out a method capable of preventing dusts for a long period of time.

The feature of the present invention consists in a method of preventing dusts, comprising spreading an aqueous solution containing both a nonionic surface active agent and a polyhydric alcohol on the substances which develop dusts.

As the nonionic surface active agent to be used in the present invention, there can be used polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene polyhydric alcohol fatty acid ester, polyoxyethylene alkyl amine, polyoxyethylene fatty acid amide, polyhydric alcohol fatty acid ester and the like. These nonionic surface active agents can be used in combination with anionic surface active agents, such as alkyl aryl sulfonate, dialkyl sulfosuccinate, alkyl methyl taurate, fatty acid salt and the like; cationic surface active agents, such as quaternary ammonium salts, quaternary phosphonium salts and the like; and amphoteric surface active agents, such as alkyl betaine, alkyl glycine and the like.

Among the nonionic surface active agents, polyoxyethylene nonionic surface active agents are effective, and particularly ones obtained by adding 6-20 moles of ethylene oxide to one mole of fatty acid, alcohol, amine or fatty acid amide having 10-22 carbon atoms, and ones obtained by adding 6-20 moles of ethylene oxide to one mole of alkylphenol having an alkyl group having 8-18 carbon atoms are preferable.

As the polyhydric alcohol to be used in the present invention, there can be used water-soluble polyhydric alcohols, such as ethylene glycol, propylene glycol, glycerine, trimethylolpropane, pentaerythritol, sorbitol, sorbitan, polyethylene glycol, polypropylene glycol, polyglycerine, sugar and the like.

These nonionic surface active agents and polyhydric alcohols are spread in the form of an aqueous solution containing 0.001-10% by weight, preferably 0.01-1% by weight, of each of the compounds on the substances which develop dusts.

The nonionic surface active agent and the polyhydric alcohol can be spread in the form of separate aqueous solutions containing each of these compounds, but it is more advantageous and more effective to spread these compounds in the form of an aqueous solution containing both the compounds.

According to the method of the present invention, the nonionic surface active agent and the polyhydric alcohol exhibit their effect for a period of time remarkably longer than that achieved by use of the nonionic surface active agent or the polyhydric alcohol alone, and dusts can be prevented for a long period of time.

According to the method of the present invention, development of dusts is effectively prevented, and therefore the environment of the place which stores coal powder, ore powder, fly ash, sand and the like, and that of the operation site, which handles these substances, can be remarkably improved.

The following examples are given for the purpose of illustration of this invention and are not intended as limitations thereof. In the examples, "%" means % by weight.

Sample aqueous solutions shown in Table 1, below, were produced by the use of various nonionic surface active agents and polyhydric alcohols. The sample aqueous solutions were spread on coal powder and a test for dust prevention was effected in the following manner.

Bituminous coal (Blair Athor Coal) powder containing at least 70% of particles having a size of not larger than 3 mm was stacked in a height of about 20 cm on an aluminum square vat having a side of 45 cm and a depth of 2 cm. Then, 600 ml of the above described sample aqueous solutions were spread on the bituminous coal powder by means of a sprayer. In the above experiments, the amount of the bituminous coal powder was about 17 kg, and the spread amount of the sample aqueous solutions was about 3 l/m.sup.2.

After the above treated bituminous coal powder was left to stand for a given period of days, the coal powder was subjected to a scattering test by blowing air in the following manner.

The vat having the above described bituminous coal powder stacked therein was placed in a wind tunnel, and air was blown into the wind tunnel at a rate of 8 m/sec or 13 m/sec for 3 minutes, and the weight of the scattered coal powder was measured. The obtained results are shown in Table 1. It can be seen from Table 1 that the method of the present invention, wherein nonionic surface active agent is used in combination with polyhydric alcohol, is superior to the use of nonionic surface active agent or polyhydric alcohol alone.

The effect of the present invention on the prevention of dusts during the transportation of coal powder was examined.

On a belt conveyor having a length of 10 m and a width of 50 cm, which had been placed at a height of 2 m, was stacked uniformly 100 kg of the same bituminous coal powder as used in Example 1, and 10 l of each of sample aqueous solutions No. 1-No. 5 of Example 1 was spread on the bituminous coal powder. Then, the belt conveyor was moved at a rate of 10 m per minute to drop the coal powder, and the development of dusts was observed. The obtained results are shown in the following Table 2. It can be seen from Table 2 that the method of the present invention, wherein a nonionic surface active agent is used in combination with polyhydric alcohol, is remarkably effective for preventing dusts.