Use of mixed hydroxyethers as auxiliaries for the dehydration of

Details Use of mixed hydroxyethers as auxiliaries for the dehydration of Use of mixed hydroxyethers as auxiliaries for the dehydration of

1991-12-04

1993-06-01

Hruskoci, Peter

Liquid purification or separation

Processes

Making an insoluble substance or accreting suspended...

209 5, 210732, 210778, C02F 1114

Patent

active

052156699

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to the use of mixed hydroxyethers of the general formula I
R.sup.1 denotes an alkyl group having 1 to 10 carbon atoms,
R.sup.2 denotes an alkyl group having 8 to 20 carbon atoms and x denotes a number in the range from 1 to 20 as auxiliaries for the dehydration of water-containing finely divided solids.
2. Discussion of Related Art
In many branches of industry, e.g. in mining or in sewage treatment plants, large amounts of finely divided solids having high water contents, which have to be dehydrated before further processing of the solids or their disposal, are formed. Thus, for example, the dehydration of water-containing coal or coke is a central process in the processing of fuels based on coal. The maximum allowable values for the water content of these materials demanded by the market can often be adhered to only with difficulty, since, for example, the coal supplied is produced in very fine particles due to the extensive mechanization of the underground coal mining. Currently, about 38% of the run-of-mine coal is fines having a particle diameter in the range from 0.5 to 10 mm; a further 14% is duff having a particle diameter below that.
It is known to use surfactants as dehydration auxiliaries for the dehydration of water-containing finely divided solids, in particular coals, which make it possible to reduce the residual moisture of fines and duff. This is explained by the property of the surfactant to reduce the surface tension and the capillary pressure of water in the material to be extracted. At the same time, this reduces the adhesive energy which must be supplied to remove the surface water. This leads to improved dehydration, when surfactants are used, while the amount of energy remains unchanged.
Dialkyl sulfosuccinates (U.S. Pat. No. 2,266,954) and nonionic surfactants of the type of alkylphenol polyglycol ethers [Erzmetall 30, 292 (1977)] have been described as surfactant-based dehydrating auxiliaries of the above-mentioned types. However, these surfactants have the disadvantage of showing excessive foaming, which leads to considerable problems in the processing plants, in particular in the recirculation of the water which is usually employed.


DESCRIPTION OF THE INVENTION

Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term "about".
The invention is based on the finding that nonionic surfactants of the general formula I increase the dehydration rate without foaming and reduce the residual moisture of the dehydrated solids when employed in water/solid systems.
The group R.sup.1 of the mixed hydroxyethers to be used according to the invention of the general formula I is a straight-chain or branched or cyclic alkyl group having 1 to 10 carbon atoms, for example a methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl or decyl group. Alkyl groups of the above list having 1 to 4 carbon atoms are preferred. The group R.sup.2 in the general formula I is an alkyl group having 8 to 20 carbon atoms, for example an octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl or eicosyl group, in particular an alkyl group from the above list having 12 to 16 carbon atoms, straight-chain radicals R.sup.2 being particularly preferred. x in the general formula I is a number in the range from 1 to 20, the range from 2 to 15 being preferred.
In accordance with their use according to the invention, the mixed hydroxyethers of the general formula I have to be water-soluble. It may occur that the water solubility is not quite sufficient, if the mixed hydroxyethers of the general formula I have low values of x and long-chain radicals R.sup.1 and/or R.sup.2 where the chain lengths are within the abovementioned limits; however, the required water solubility can be obtained by increasing the value for x within the

REFERENCES:
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patent: 4385903 (1983-05-01), Moriyama et al.
patent: 4559143 (1985-12-01), Asada et al.
patent: 4925587 (1990-05-01), Schenker et al.
patent: 4990264 (1991-02-01), Fuller et al.

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