Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1133
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FREEZE MODIFICATION AGENT
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Background of the Invention
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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
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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.
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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.
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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
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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
:,
--4--
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~L6~B
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,
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* Trade Mark.
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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
--8--
#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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* Trade Mark.
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