CA1162728A - Freeze modification agent - Google Patents

Abstract

The strength of ice is reduced by dissolving in water prior to freezing a composition of (A) a water-soluble polyhydroxy compound or monoalkylether thereof and (B) a nonionic surfactant in an amount to provide an effective amount of (A) plus (B). The method is especially useful for application to particulate solids, such as coal and mineral ores, which are shipped and stored in masses exposed to freezing temperatures. Any ice that is formed is physically weak and will not deter the unloading of the thusly con-ditioned particulate solids.

Description

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FREEZE MODIFICATION AGENT
-Background of the Invention .
1. Field of the Invention When the surface moisture on particulate solids freezes, the ice acts as a powerful adhesive holding the particles together in a mass. The adhesivity is influenced by both the particle size of the svlids and the moisture content as shown later. For example, coal with as little as 4 percent moisture will, when frozen, cohere so strongly as to require special handling to break up the frozen mass. It thus becomes difficult to unload or dump railway cars, trucks and other conveyances used to transport coal, mineral ores and other finely-divided solids. It also makes difficult the movement of coal out of outdoor coal storage piles in a condition for fuel or other use. Unloading frozen coal from railroad cars is time consuming, can result in blocked dump chutes and can often leave as much as five tons of coal in the car. All of these factors point to the definite need of developing an economic method of treating coal, ores and other divided solids to overcome the problems of transport of those solids.

2. Description of the Prior Art Various approaches have been used with limited degrees of success. Sodium chloride and calcium chloride salts have been added to moist coal as it is being loaded with some degree of success toward reducing the freezing problem.
However, such salts contribute to the corrosion of all equip-ment with which the solids come in contact and are detrimental ' _l _ to the coking process when used with coking coal. Oil has been used to freeze-proof coal with questionable effectiveness.
Oil-soluble surfactants have been added to the oil but with questionable results. Ethylene glycol has been employed, but although successful, the cost of treatment has been very high.
Prior Patents U.S. 4,117,214 discloses reducing the strength of ice by dissolving in water, prior to freezing, a composition of (A) a water-soluble polyhydroxy compound or monoalkylether thereof, and (B) a water-soluble organic non-volatile compound having a hydrophilic group such as amine, carboxyl, or carboxylate groups.
U.S. 2,973,254 relates to preventing formation of ice-coke masses during shipment of coke in railroad cars by applying a wetting agent to the top surface only of a bulk mass of considerable depth of normally free~flowing coke pieces contained or located in an open-top railroad car. The theory of this patent is that the wetting agent causes the water, which may contact the top surface of the mass, to pass into the pores in the interior of the coke pieces and freeze substantially harmlessly therein whereby the coke pieces are not frozen together.
U.S. 3,350,314 relates to foamable compositions for deicing/defrosting surfaces, for example, external surfaces of aircraft on the ground. The composition comprises ethylene glycol and ethoxylated tertiary amine surfactants.

U.S. 3,794,472 relates to prevention of freezing together of particles of coal by coating the coal particles with a thin film of an em~lsified hydrocarbon liquid. The emulsifier is a surfactant.
U.S. 3,298,804 relates to surface treatment of coal particles to prevent water-wetted surfaces from freezing together. The composition of this patent employs a surface-active compound with a liquid hydrocarbon.
U.S. 2,373,727 relates to compounds for applica-tion to aerofoils and like surfaces subject to ice-forming conditions. The composition includes a dispersing agent, preferably soap, glycols such as ethylene glycol, along with gelatin~ and oil.
Summary of the Invention The present invention is directed to a method for treating water such that when frozen, the resulting mass is physically weak and is not dificult to break apart. The invention is especially adapted to the treatment of moist particulate solids such that, when the moisture is frozen, the mass is easily broken apart. This is done by spraying the particles with a composition of (A) a water-soluble poly-hydroxy compound or monoalkylether thereof and (B) a low-foaming nonionic surface-active agent.
Thus the present invention generally provides a method for reducing the strength of ice wherein an e~fective amount of a strength reducing composition is dissolved in the water prior to freezing, said composition comprising (A) a water-soluble polyhydroxy compound or monoalky-lether thereof and (B) a low Eoaming nonionic surfactant.

- 3 -, The presen-t invention in particular provides a method for treating particulate solids having surface moisture to redu-ce the cohesive strength of masses of said solids when frozen, said method consisting of coating such solids with an effec-tive amount of a fluid composition comprising (A) a water-soluble polyhydroxy compound or monoal-kylether thereof and (B) a low foaming nonionic surfactant.
Description of the Preferred Embodiments This invention is useful with water itself and with most forms of divided moist solids, other than very finely- di-vided solids, e.g., 0-3 mm, which themselves are neither water soluble nor water swellable. Typical of such materials _, - 3 a -are coal and mineral ores such as iron and copper ore. Such solids are usually stored in piles exposed to the atmosphere and transported in railroad cars or trucks open to the environment. They thus are exposed to the rain and the other elements where they collect significant amounts of surface moisture. When the temperature drops below freezing, the particles are bound to~ether by the ice formed at the surfaces and require mechanical and thermal means to break up the mass before loading or unloading operations.
One of the ingredients useful in the compositions employed in the present method is a water-soluble polyhydroxy compound. A preferred group is the polyhydroxyalkanes.
Typical members of that class are ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, glycerine, sugar, and various mixtures thereof. The monoalkyl ethers, such as the monobutylether of ethylene glycol, are also useful.
The second material to be used in the treating of the finely~divided particles is a low-foaming nonionic surface-active agent. Examples of such agents which have been found to be particularly effective, are the mixtures of compounds represented by the following formula:

R--O(A)H

wherein R is an essentially linear alkyl group having from 10 to 18 carbon atoms, with the proviso that at least 70 weight ~ ~ercent of said compounds in said mixture have an R of from 12 :, - .

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to 16 carbon atoms~ and A is a mixture of oxypropylene and oxyethylene groups, said oxypropylene and oxyethylene groups being from 55 percent to 80 percent of the total weight of the compounds, the oxypropylene to oxyethylene ratio of said total weight being from 0.85:1 to 2.75:1. The properties and preparation of these compounds are set forth in UOS. Patent No. 3,504,041 granted March 31, 1970 to Eugene A. Weipert~

Conjugated polyoxypropylene-polyoxyethylene com-pounds having the following formula are also suitable:

Y[(C3H6O)y(c2Hgo)zH]x where Y is the residue of a low molecular weight (6 carbon atoms per molecule or less) organic compound containing therein x hydrogen atoms capable of reacting with 1,2-propylene oxide, x is an integer greater than 1, y has a value such that the molecular weight of the compound exclusive of the oxy-ethylene groups is at least 900, and z has a value such that the oxyethylene groups constitute about 2 to 90 percent of the total weight of the compound. Low-foaming surface-active agent of this type generally contain about 2 to 20 percent by weight oxyethylene groups. The properties and the preparation of these conjugated polyoxypropylene-polyoxyethylene compounds are set forth in U.S. Patent No. 2,674,619, granted April 6, 1954, to Lester G. Lundsted.

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Additional surface-active agents which may be employed are commercially available under the names "Antarox*
BL225, LF330 and LF344", "Igepal*CO210", Triton*"CF10, CF21, CF32, DFl2 and DF20".
The amount of the material incorporated in the water and the ratio of the hydroxy compound to the surface-active agent may be varied within wide limits. The amount used should be that minimum needed to lower the strength of the frozen mass such that it can be easily broken. The actual amount will depend in large measure on the particle size, the amount of moisture, the condition of exposure of the particles and to some extent on the choice of materials. As a general rule, a concentration of about 0.5 weight percent of combined materials based on the moisture will suffice to achieve the objectives of the invention, although lesser amounts may also suffice in some instances. In very severe exposure conditions, somewhat more may be desired. The upper limit is determined principally by economic factors.
The ratio of surface-active agent to the hydro~y compound will depend on a number of factors. As a general rule, the combination of ingredients will contain about 0.0005 to about 0.05 part by weight of the surface-active agent for each part of polyhydroxy compound or monoalkylether thereof. Optimum selection wil be readily made with simple routine experiments.
The compositions used in the treatment may also include other materials such as dyes and colorants to indicate the progress of the treatment, stabilizers and anti-oxidants, : ' * Trade Mark.

~, organic non-volatile compounds such as described in U.S.
Patent No~ 4,117,214, alkali metal carbonates and conven-tionally added materials. In all cases, such additive must be water soluble.
The compositions of this invention may be admixed with moist particulates using conventional techniques. One convenient method is to locate a spray bar above the discharge end of a loading end of a loading conveyor and another spray bar below. As the particles tumble off the conveyor, the possibility that moisture present on the particles will come into intimate contact with the spray applied composition is improved.
The invention will be illustrated with the following examples wherein all parts and percentages are by weight unless otherwise indicated.

Examples 1-8 Coal for the eight examples was crushed and sized to 3/8 inch by 1/16 inch to obtain the approximate size distri-bution for a 3 inch diameter container. The coal samples were placed in a colander and immersed in water and drained until the free water was removed.
All the coal samples were spread in a thin layer on a plastic sheet for spraying with composition #1 using an artist's air brush. Composition #l is a still bottom waste product from the production of ethylene glycol having the following typical analysis:
Composition ~1 Component Weight Percent Ethylene glycol 22.8 Diethylene glycol 15.0 Triethylene glycol 44.2 Tetraethylene glycol 8.5 Water 10.8 Ash 0.4 Two equal size samples, each representing one-eighth of the crushed and sized coal, were sprayed with a sufficient amount of the above composition to give four pints per ton of coal. A second pair of equal size samples also representing an eighth of the coal was sprayed at a rate to give eight pints per ton of coal. A third pair of samples was sprayed with composition #2 at a rate to give four pints per ton of coal and a fourth pair of samples was sprayed with composition #2 at a rate of eight pints per ton of coal. Composition #2 is the same as composition #1 with the addition of one percent by weight nonionic surfactant. ~he nonionic surfactant is a mixture of compounds, having an average molecular weigh~ o~
about 800, represented by the ~ollowing formula:

R--OIA)H

wherein R is an essentially linear alkyl group having from 12 to 15 carbon atoms, and A is a mixture of oxypropylene and oxyethylene groups, the oxypropylene to oxyethylene ratio being about 2:1. Each coal sample was mi~ed by hand and placed in a cylindrical cardboard container having a 3 inch diameter, a height of 6 inches and open at one end. The vertical side of the cylinder was cut to facilitate sample removal, rubber bands being employed to hold the cylindrical shape. The container wall was lined with plastic film to aid in removal of the sample and the container bottom was per-forated to allow drainage of excess water.
Each of the eight containers, containing the coal samples, was placed in a deep-freeze at -10F for at least 24 ` 20 hours. After the initial freeze, water was sprayed on top of the coal in each cylinder in an amount to equal 1/2 inch of rainfall and the container returned to the freezer. To facilitate the uniform application of pressure to the top of the coal sample, an ice cap is formed on top of the coal by inverting the container in a jar cap containing water and lined with a thin plastic film. The unit was then returned to 2~

the free~er where it remained for a time sufficient to give a total freeze time of 16 days. Each sample was then removed from the container and tested in compression in an Instron*
Universal Test Machine, Model No. TTCM at a cross-head speed of 0.5 centimeters per minute using hydraulic pressure. The Instron strip chart shows the pressure against time on the compression test, the results of which are set forth in the table below. In the table, the cohesion index value is the pressure reading at the initial fracture of the coal sample while the relative energy index is the area under the chart curve of pressure against time. A description of the breakup for each sample is shown under comments in the table below.
From the table, it can be seen that the addition of 1~ by weight of the surfactant improves both the cohesion index and the relative energy units.

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Claims (10)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for reducing the strength of ice wherein an effective amount of a strength reducing composition is dissolved in the water prior to freezing, said composition comprising (A) a water-soluble polyhydroxy compound or mono-alkylether thereof and (B) a low foaming nonionic surfactant.

2. The method of claim 1 wherein said polyhydroxy compound (A) is selected from the alkylene glycols and mixtures thereof.

3. The method of claim 2 wherein said strength reduction composition contains about 0.0005 to 0.05 part by weight of (B) nonionic surfactant per part of compound (A).

4. A method for treating particulate solids having surface-moisture to reduce the cohesive strength of masses of said solids when frozen, said method consisting of coating such solids with an effective amount of a fluid composition comprising (A) a water-soluble polyhydroxy compound or mono-alkylether thereof and (B) a low foaming nonionic surfactant.

5. The method of claim 4 wherein said solids are coated with said fluid composition by spraying said fluid composition onto said solids.

6. The method of claim 5 wherein said component (A) is selected from the alkylene glycols and mixtures thereof.

7. The method of claim 6 wherein said fluid compo-sition comprises 0.0005 to 0.05 part by weight of (B), the nonionic surfactant per part of compound (A).

8. The method of claim 7 wherein said nonionic surfactant is a mixture of compounds represented by the following formula:

R--O(A)H

wherein R is an essentially linear alkyl group having from 10 to 18 carbon atoms, with the proviso that at least 70 weight percent of said compounds in said mixture have an R of from 12 to 16 carbon atoms, and A is a mixture of oxypropylene and oxyethylene groups, said oxypropylene and oxyethylene groups being from 55 percent to 80 percent of the total weight of the compounds, the oxypropylene to oxyethylene ratio of said total weight being from 0.85:1 to 2.75:1.

9. The method of claim 7 wherein said particulate solids are coal particles and said composition is applied to said solids in amount of at least 0.5 weight percent of (A) plus (B) based on the surface moisture on the solids.

10. The method of claim 9 wherein component (A) is a mixture of alkylene glycols and said component (B) is a mixture of compounds represented by the following formula:

R--O(A)H

wherein R is an essentially linear alkyl group having from 10 to 18 carbon atoms, with the proviso that at least 70 weight percent of said compounds in said mixture have an R of from 12 to 16 carbon atoms, and A is a mixture of oxypropylene and oxyethylene groups, said oxypropylene and oxyethylene groups being from 55 percent to 80 percent of the total weight of the compounds, the oxypropylene to oxyethylene ratio of said total weight being from 0.85:1 to 2.75:1.