Fluid, formulation, and method for dust control and dewatering of particulate materials

An aqueous dust suspression and dewatering fluid comprising one or more surfactants and at least one high terpene-containing natural oil. The fluid can be used in a formulation of water dosed with the aqueous dust suspression and dewatering fluid for the abatement of dust and dewatering of particulate material. Methods are described for the abatement of dust and dewatering of particulate material using the formulation.

BACKGROUND OF THE INVENTION 
The invention relates to aqueous dust suppression fluid and formulations 
for the abatement of coal dust containing water dosed with dust 
suppression fluids. Furthermore, the invention relates to methods for the 
abatement of coal dust. 
Dust suppression is the reduction of the extent to which finely divided 
solid particulate material becomes suspended in the air. A variety of 
materials such as coal, sulfur, phosphate, clay, and other finely divided 
ores and minerals, generate dust in transfer and handling operations 
during mining, transportation, storage, and use. 
Dust is a particularly severe safety and health hazard in coal mining, 
handling, and storage operations. Coal often chips into small fragments by 
the action of wind and rain, frictional movement due to motion in transit, 
and abrasion in handling. Respirable coal dust has a particle size of less 
than about 10 microns and its inhalation can lead to pneumoconiosis, i.e., 
"black lung disease". Also, dust explosions due to spontaneous combustion 
may occur when the dust is confined to a small air space such as in coal 
mining operations. 
It is known to suppress coal dust in mines by spraying with various aqueous 
systems containing chemical additives to improve working conditions and 
reduce the toxicological risks and explosion hazards. For example, U.S. 
Pat. No. 4,425,252 describes a method to abate coal dust using an anionic 
surfactant, preferably sodium dodecyclbenzene sulphonate and a nonionic 
surfactant, preferably a polyethoxylated nonylphenol, in an aqueous 
formulation. The method comprises spraying the coal dusty area with a 
formulation comprising water containing up to 0.1% by weight of the 
mixture of the anionic surfactant, i.e., a water soluble salt of an alkyl 
aryl sulfonic acid and nonionic surfactant having an HLB of from 10 to 16. 
Optimally, the mixture contains one or more cosolvents generally of the 
class of alkylene glycol monoalkyl ethers, C.sub.2 to C.sub.5 alkanols and 
mixtures thereof. 
Furthermore, several techniques have been developed utilizing foamable 
compositions for suppressing coal dust. For example, U.S. Pat. No. 
4,551,261 describes a foam comprising water, a foaming agent, and an 
elastomeric water insoluble polymer. A variety of anionic and nonionic 
surfactants and detergent wetting agents are described as useful foaming 
agents, and a variety of elastomeric and water insoluble synthetic organic 
polymer binders are described as useful elastomeric water insoluble 
polymers. 
U.S. Pat. No. 4,971,720 relates to a method for suppressing dust process 
emissions. The method utilizes a foaming agent which may be a low salt 
tolerant surfactant selected from salts of fatty acids, alkyl sulphates, 
and alkyl aryl sulphonates. 
U.S. Pat. No. 4,561,905 describes a coal dust suppression mixture of oil, 
water and a surfactant in the form of an emulsion that is diluted and 
foamed. The foam is then sprayed into a falling mass of coal. The oils 
suitable for use are described as heavy process oils and include asphalt 
dissolved in a moderately heavy oil, residual flush oils or relatively 
high viscosity fuel oil. The preferred oils have a viscosity in the range 
of from approximately 600 to 7,000 SUS at 38.degree. C., a pour point in 
the range of approximately -18 to 21 .degree. C., a molecular weight of at 
least 300 and a boiling point of at least 204.degree. C. 
U.S. Pat. No. 4,944,892 teaches an aqueous composition which comprises a 
linear primary alcohol ethoxylate surfactant, a suitable scenting oil such 
as pine oil or lemon oil and water among other adjuvants. 
U.S. Pat. No. 4,929,278 discloses an aqueous bath preparation which 
comprises essential oils such as orange peel oil, orange oil, lemon oil or 
the like. Further, the bath preparation comprises a soap or surfactant 
which may include straight chain alkyl benzenesuflonates, alkyl sulfuric 
acid ester, alkyl ether sulfuric acid ester and the like. 
U.S. Pat. No. 3,367,878 shows a composition which comprises 20.2% by weight 
water, 1.0% by weight pine oil, 1.8% by weight sodium xylene sulphonate 
surfactant. 
U.S. Pat. No. 4,175,062 teaches an aqueous composition which comprises 7.5% 
by weight of sodium dodecylbenzene sulfonate, 0.8% by weight of pine oil 
and other adjuvants. 
Japanese Patent 44,495 discloses an aqueous composition which comprises 20% 
by weight of sodium lauryl benzene sulfonate and 1% by weight of 
D-limonene along with other adjuvants. 
Additional examples of the prior are are found in U.S. Pat. No. 1,995,598; 
U.S. Pat. No. 1,995,603; U.S. Pat. No. Re 29,649; U.S. Pat. No. 4,362,638; 
U.S. Pat. No. 4,620,937; U.S. Pat. No. 4,761,159; U.S. Pat. No. 4,859,359; 
U.S. Pat. No. 5,146,938; U.S. Pat. No. 5,152,928 and U.S. Pat. No. 
5,182,105. 
Thus, various techniques have been developed to suppress coal dust, and 
many of the techniques are effective for reducing that dust. However, 
there is still a need for improvement in coal dust suppression, and many 
of the prior techniques were developed without a need to address problems 
associated with modern coal mining practices. 
SUMMARY OF THE INVENTION 
Accordingly, it is the primary object of the invention to provide an 
effective, novel coal dust suppression fluid, which also effectively 
addresses certain problems associated with modern coal mining practices. 
For example, most modern, state-of-the-art, continuous coal mines utilize 
scrubbers which tend to clog. Thus, there is a need for a material which 
not only effectively reduces airborne dust, but also effectively assists 
in keeping spray nozzles and scrubber screens clean and unclogged. In 
addition, coal suppression fluids often have secondary uses and are 
frequently circulated through mine equipment underground as a heat 
exchange fluid. However, water jackets on that equipment tend to 
accumulate mineral deposits such as calcium deposits, drastically reducing 
cooling efficiency. Hence, it is a further object of the invention to 
provide a coal dust suppression fluid which increases cooling efficiency 
when used as a heat exchange fluid by maintaining the water jackets on the 
equipment underground free of mineral deposits such as calcium deposits. 
Many of the chemical additives used in coal dust suppression fluids are 
also very expensive. It is therefore another object of the invention to 
provide a coal dust suppression fluid which reduces the need for costly 
chemical additives. Furthermore, many of the chemicals used in coal dust 
suppression are themselves toxic to humans to some degree, and destructive 
of the environment. Thus, another object of the invention is to provide a 
coal dust suppressing fluid which is less toxic to humans and is 
environmentally acceptable thereby reducing process water contamination; 
water which ultimately will find its way to local streams, rivers and 
lakes. 
Another problem associated with the prior art is the vast amount of process 
water which is necessary for coal dust suppression. While process water is 
dosed with various aqueous solutions containing chemical additives to 
assist in dust reduction, the amount of actual process water used remains 
very high. it is thus even another object of the invention to provide a 
coal dust suppression fluid which actually reduces the amount of process 
water needed for dust suppression. 
The aforementioned and other objects of the invention can be obtained by 
the invention. The invention provides a novel, aqueous, coal dust 
suppression fluid comprising one or more surfactants and at least one high 
terpene-containing natural oil. Another aspect of the invention relates to 
a formulation for the abatement of coal dust comprising water dosed with 
the aforementioned aqueous dust suppression fluid. Even another aspect of 
the invention relates to a method for the abatement coal dust using the 
formulation. 
The novel coal dust suppression fluid of the invention is very effective 
for suppressing airborne dust when used in a formulation for the abatement 
of coal dust. Furthermore, the fluid can effectively assist in keeping 
spray nozzles and scrubber screens clean and unclogged. In addition, the 
coal dust suppression fluid can increase cooling efficiency when used as a 
heat exchange fluid by continuously clearing mineral deposits such as 
calcium deposits from water jackets on the underground equipment. Also, 
the coal dust suppression fluid can reduce the need for costly chemical 
additives, and can provide a coal dust suppression fluid which is less 
toxic to humans and is environmentally acceptable. When process water is 
dosed with the coal dust suppression fluid of the invention, it has also 
been found that the fluid can actually reduce the amount of process water 
needed for coal dust suppression.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As noted above, the invention relates to an aqueous dust suppression fluid 
comprising one or more surfactants and at least one high 
terpene-containing natural oil. Process water can be dosed with the fluid 
to provide a dust suppression formulation. Dust is contacted with the 
formulation for the abatement of dust. Another aspect of the present 
invention is the use of the fluid and formulation to dewater particulate 
material. 
High terpene-containing natural oil as used herein is defined as those 
natural oils having a terpene content of at least 50%. It is preferable 
that the high terpene-containing natural oil contain at least 90% 
terpenes. 
Suitable high terpene-containing natural oils include pine oil and citrus 
peel oils, preferably orange oil, grapefruit oil and lemon oil. Of these, 
orange oil is the most preferred generally containing about 90% to 94% 
terpenes. 
The aqueous dust suppression fluid contains from about 1% to about 15% by 
weight high terpene-containing natural oils, preferably from about 2% to 
about 10% by weight, and more preferably from about 2% to about 8% by 
weight. Naturally, the amount of high terpene-containing natural oils will 
depend upon the amount of terpenes in the oil. For example, in the case of 
the preferred embodiment, orange oil, the oil can be added in an amount of 
from about 1% to about 15% by weight, although it is preferably added in 
an amount of about 2% to about 8% by weight. 
While not wishing to be bound by theory, it is believed that the terpenes 
in the natural oils provide the mechanism for obtaining many of the 
objects of the invention. For example, the terpenes are believed to break 
up oily (fatty) deposits on the coal that tend to clog spray nozzles and 
scrubber screens. Furthermore, the terpenes are believed to break up fatty 
layers on coal particles allowing the water droplets to better wet the 
coal particles. 
In addition, because the high terpene content oils are natural oils, 
environmentally acceptable products are being used to dose the process 
water, thereby reducing process water contamination. With respect to at 
least orange oil, it is also believed that this oil in combination with 
cleaned coal particles act as a liquid ionizer. This is seen from a 
reduction in total dissolved solids and suspended solids which remain in 
the process water. 
The aqueous dust suppression fluid of the present invention also contains 
at least one surfactant. Generally, conventional surfactants used in dust 
abatement can be used such as anionic and nonionic surfactants. Preferred 
are anionic surfactants such as salts of fatty acids, alkyl sulphates, 
alkyl ether sulphonates, and alkyl aryl sulphonates. Examples of preferred 
surfactants include sodium dodecylbenzene sulphonate, sodium lauryl ether 
sulphate, sodium olefin sulfonate and salts such as sodium salts of 
secondary alkane sulphonates (e.g., Hostapur SAS 60 marketed by Hoechst). 
The aqueous dust suppression fluid may further include a linear alcohol 
ethoxylate and urea. 
Generally, a large portion of the aqueous dust suppression fluid will 
comprise surfactants. For example, the fluid can contain up to about 40% 
by weight surfactant(s), preferably from about 15% to about 25% by weight 
surfactant(s), and more preferably from about 20% to about 22% by weight. 
The aqueous coal dust suppression fluid of the invention may contain a 
variety of additives such as antioxidants and preservatives. An example of 
a suitable antioxidant is BHT (2,6-di-tert-butyl-para-cresol). The 
antioxidant(s) may be added to the composition in an amount of from about 
0.01% to about 1% by weight, preferably from about 0.08% to about 0.12% by 
weight. Examples of suitable preservatives include formaldehyde, 
methylparaben, propylparaben, borax and mixtures thereof. The 
preservatives may be added to the composition in an amount of from about 
0.4% to about 5% by weight, preferably from about 0.4% to about 1.0% by 
weight. 
Since the dust suppression fluid is an aqueous composition, the balance of 
the composition will be water. Typically, the fluid will contain from 
about 66% to about 70% of water by weight. 
An example of an effective aqueous dust suppression fluid comprises about 
12% sodium dodecyl benzene sulphonate, about 7.2% sodium lauryl ether 
sulphate, about 9% linear alcohol ethoxylate, about 0.9% urea; about 2.25% 
cold pressed orange oil, about 0.1% butylated hydroxy toluene and about 
0.6% Phenonip with the balance being water (all percentages are by 
weight). 
In operation, process water will be dosed with the aqueous dust suppression 
fluid to provide a dust abatement formulation. Typically, process water 
can be dosed with the fluid at a weight ratio of about 500:1 up to about 
15000:1 (water/fluid) to provide an effective formulation for the 
reduction in airborne dust. More preferably, process water can be dosed 
with the fluid at a weight ratio of about 3000:1 up to about 7000:1. 
The aqueous dust suppression fluid can be injected into a main column of 
process water pumped into the coal mine. The process water can be pumped 
by an electronically controlled pump. The metering pump can be controlled 
by a flow meter and control box measuring the amount of flow. The dosed 
process water can then be directed as needed, to various parts of the mine 
for dust suppression. 
Another aspect of the invention provides a mechanism for dewatering 
particulate material such as coal. Once coal has been mined, coal is 
typically sent to a preparation plant. In preparation plants, coal is 
sorted by various methods, such as by changing the specific gravity of 
fluids in which the coal is dumped. By raising or lowering of the specific 
gravity of those fluids, various qualities of coal can be sorted by the 
coal specific gravity. After the coal has been sorted, it is washed. 
Among other things, process water is also removed from the coal in the 
preparation plants. The removal of water from the coal product in the 
preparation plant is one of the most economically significant steps in 
coal cleaning. That is, efficient dewatering is critical to ensure 
contract compliance, minimize transportation costs, and reduce coal 
handling problems, especially with respect to water freezing in storage 
vessels and rail cars. 
There have been many mechanical techniques such as filtration and 
centrifugation which have been used to remove process water in preparation 
plants. Also, chemical techniques have been used to dewater coal. For 
example, surface active agents have been used to reduce water surface 
tension and enhance water removal from coal products. 
The present invention unexpectedly provides a novel composition which can 
enhance water removal from mined coal products. As a chemical technique 
for removing water from coal at a preparation plant, the composition can 
be used, for example, in disc or drum filtration applications by feeding 
the composition directly to a slurry entering a filter vat. Or, a solution 
of the composition can be sprayed directly on a filter cake. Centrifugal 
dryer feed can be readily treated by spraying a solution of the 
composition onto the coal as it discharges from dewatering screens and the 
like. 
An effective dewatering fluid comprises about 12% sodium dodecyl benzene 
sulphonate, about 7.2% sodium lauryl ether sulphate, about 9% linear 
alcohol ethoxylate, about 0.9% urea; about 2.25% cold pressed orange oil, 
about 0.1% butylated hydroxy toluene and about 0.6% Phenonip with the 
balance being water (all percentages are by weight). 
In another and preferred embodiment of the invention, the composition can 
be added to the wash water. As the wash water will then have a 
substantially reduced surface tension, less will remain with the coal 
after washing. For example, by using this technique 96%, instead of 94% 
coal per ton of freight could be obtained for larger sizes, and 88% coal 
rather than 84% coal for fine coal. In a broad sense, by dosing wash water 
by about 7 grams to about 50 grams per metric ton of coal to be washed 
with the composition according to the invention about 30% to about 70% 
reduction in water content can be acheived. 
As a particularly effective embodiment of the invention, the composition 
can be used both in a preparation plant for dewatering applications, and 
for coal dust suppression. For example, dust abatement water dosed with 
the dust suppression fluid of the invention can also be used in 
preparation plant dewatering if run-off water is used. 
While the invention has been described above with respect to certain 
particular embodiments thereof, numerous other forms and modifications 
will be apparent to those skilled in the art. The appended claims and the 
invention generally should be construed as covering all such obvious forms 
and modifications which are within the true spirit and scope of the 
invention.