-2-FIELD OF THE INVENTION
The present Invention relates to the froth flotation of finely divided
coal particles for separation of ash from carbon. Particularly, the
present Invention relates to an improved frothing agent adaptable to
forth flotation process to enhance efficiency of the froth flotation
process and coal selectivity.
BACK GROUND OF THE INVENTION
In the coal Industry, various types of shale and clay are produced as
a mixture with the coal. To increase the heating value of the coal and
to reduce the hauling costs, a complex process of coal washing is
normally used to reduce the total ash content In this process the
coal is graded to a certain size, usually less than 15 mm and greater
than 1/2 mm, and then fed Into a dense medium cyclone.
The usual practice for separation of fine particles (less than 1/2 mm)
of coal contained In coat slurry through the use of froth flotation
processes is well known. Froth flotation processes Involve introducing
air into the coal slurry. The hydropnoble particles of coal are

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contacted with finely disseminated air bubbles such that the fine air
bubbles become adhered to the hydrophobic coat particles. The
particles carrying bubbles are then permitted to rise, forming froth on
the surface of the slurry. The froth, containing the hydrophobic
particles of coal, is skimmed from the surface of the coal slurry and
collected, while rejecting any hydrophllic particles of impurities which
don't adhere to the air bubbles and which remain suspended In the
slurry.
Flotation of coal fines has become increasingly important as a
separation and cleaning process where there is lowering In both the
particle size and grade of the coal being recovered from mining
operation. The ability to remove the coal fines from coal washery or
tailings is also advantageous in order to recover coal fines missed by
other techniques of coal recovery.
In order to Improve the selectivity and recovery of the flotation
process and enhance floating of the coal fines, various types of
reagent have been developed for addition to the slurry. Frothers and
collectors are two types of reagents which are commonly used in coal

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flotation. A frothing agent is utilized to provide stable flotation froth
persistent enough to facilitate the coal separation but not so
persistent that It cannot be broken to allow subsequent handling.
The use of froth flotation to effect a separation of ash particles from
coal can be achieved only if liberation of these unwanted particles
form the coal has taken place. Most high-grade coals are floatable
naturally due to their hydrophobic surface and typically only require a
frothing agent for effecting flotation. A frothing agent Imparts
elasticity to the air bubbles, enhances particle-attachment so that the
coal is buoyed to the surface of the slurry.
Conventional frothers can be essentially divided into for groups. The
first group consists of aromatic alcohols such as a- creasol and 2,3-
xylenol. A second group is the alkoxy types such as triethoxy butane
(TEB). The third group consists of aliphatic alcohol such as 2-ethyl
hexanol, dlacetone and methyl Isobutyl carblnol (MIBC). In recent
years, a fourth group of synthetic frothers consisting of PEO
(polyethylene oxide), PPO (polypropylene oxide) and PBO
(polybutyiene oxide) types have been Introduced Into the market
These chemicals may be presented by the general equation; R
(X)nOH where R=H or CnH2n+1 and X=EO,PO or BO.

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General problems associated with the conventional frothing agents
and recent developed farther are I) Not effective for both coarse and
ultraflne particles for wide size distributed flotation feed (0.5 X 0.0
mm). It is due to some frothers are effective for coarse particles and
others are good for floating ultra fine fractions, II) Incapability of
producing low ash content clean coal form highly ash mineral particle
disseminated and difficult to float type of coal like Indian coal.
Examples of patents directed at improved frothers include U.S. Pat
No. 4, 582, 596 issued Apr. 15, 1986, U.S. Pat No. 4, 915, 825 Issued
Apr. 10, 1990, U.S. Pat No. 4, 272, 364 issued June 09, 1981, U.S.
Pat No. 4, 504, 385 issued March 12, 1985, U.S. Pat No. 5, 304, 317
issued Apr. 19, 1994, U.S. Pat No. 3, 710, 939 issued Jan. 16, 1973,
U.S. Pat No. 4, 606,818 issued Aug. 19, 1986, US. Pat No. 4, 761,
223 issued Aug. 02, 1988, U.S. Pat. No. 4, 925, 559 issued May 15,
1990. Therefore, the present inventors have developed a farther
which comprises ketone and ester functional group with a small
quantity of conditioning agent. This novel farther overcomes the
many disadvantages of the aforementioned conventional and earlier
Invented frothers, as well as provide the following advantages:
increased clean coat recovery with better selectivity, a farther having
both farther and collector properties when used in coal flotation
processes.

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OBJECTS OF THE PRESENT INVENTION
It Is therefore, an object of the present Invention to propose an
improved frothing agent adaptable to froth flotation process to
enhance the efficiency of forth floation process and coal selectivity
which eliminates the disadvantages of prior art
Another object of the present invention is to propose an improved
frothing agent adaptable to froth flotation process to enhance the
efficiency of forth floation process and coal selectivity which increases
the efficiency of the froth flotation process.
A further object of the present invention is to propose an improved
frothing agent adaptable to froth flotation process to enhance the
efficiency of forth floation process and coal selectivity which is
capable to separate very fine particles of coal.
A still further object of the present invention is to propose an
improved frothing agent adaptable to froth flotation process to
enhance the efficiency of forth floation process and coal selectivity
which performs dual function I.e. frothers and collectors.

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selected from the group consisting of fuel oils, polymers and esters.
These additional collectors are used in a dosage ranging from
between about 0.175 to about 0.350 kg/ton of coal.
The present invention has additional detailed features which shall be
further described below.
The improved frothing agent of the present invention is preferably
used in the following composition as shown in Table 1.
Table 1.
Chemicals - Wt% in mixed frother
2,6-Dimethyl-4- Heptanone - 85-89%
Tetrahydrofurfuryi acetate - 10-12%
1,2, epoxydodecane - 0.25-.30%
Water - 4.75-5.25%
A flotation cell of Denver D-12, 2.5-lit capacity is used for flotation
test This unit has a baffle arrangement at bottom to avoid swirling of
the slurry within the cell and an impeller is provided for proper mixing

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of slurry, the speed of which can be controlled by a speed regulator.
A compressor is also provided to supply air to the cell in the range of
0-20 ipm in an interval of 1 ipm. The cell has an automatic pulp level
controller through make up water tank and froth removal system.
For each batch flotation, 250 gms of coal sample are allowed to wet
for 1 hour in known volume of water. It is transferred into the 2.5-
liter capacity Denver cell. Additional water is added to maintain
required pulp density i.e. 10-14% solid content Slurry is allowed to
wet for 3 minutes at the impeller speed of 850 rpm. Then high speed
diesel oil (collector) is added and conditioned for 3 minutes. After
conditioning, requisite amount of frother is added. It is again
conditioned for another 3 minutes. The cell is filled with water up to
the marked height; air inlet valve is opened and kept at 2 1pm. The
froth samples are collected after 30, 60, 120, and 240 seconds of
flotation. After the final froth sample is collected, the machine is
stopped. The froth products and the tailings (the part that remained
Inside the machine) is dried, weighed and analyzed for their ash
content
EXAMPLE
A representative minus 0.5 mm size semi bituminous flotation feed

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coal sample is taken in this Investigation. Nature of coal sample is
difficult to float Ash analysis is carried out according to ASTM D
3174-73 standard shows that the sample contains 24.5% ash. Size-
wise weight and ash distribution analysis Is conducted with a
representative sample of the flotation feed. The flotation feed
contains high percentage (20%) of oversize fraction, namely -1+0.5
mm, having 23.5% ash, Ultra size fraction of - 0.075 mm is having
maximum weight contribution in flotation feed content approx 50%.
The conventional frother used for purposes of comparison is methyl
teobutyl carblnol (MIBC). The aforementioned improved frothing
agent of the present invention is compared against MIBC. Flotation
yield for different dean coal is shown in Fig. 1. The results for each
frother are given in the optimum frother and collector dosage with
experimental variation.
TEST RESULT
FIg. 1 shows the Improved frother is capable to produce low ash
content (8%) clean coal compare to MIBC. It reflects that at each
clean coal ash content, Improved frother Is producing higher clean
coal yield compare to MIBC.
Fig. 2 is showing the size wise clean coal ash% for different particle

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size fraction of froth product It reflects that for all size fractions
(from coarse to ultrafine fraction) improved frother of the present
invention is produce clean coal with better selectivity compare to
MIBC.
Fig. 3 shows the chemical structure of Table 1.

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WE CLAIM
1. An Improved Frothing agent adaptable to froth flotation process to
enhance coal selectivity for separation and efficiency of the forth
floatation process comprtses:-
A blended mixture of
Ketone (2,6 Dimethl-4-Heptanone) - 85-89% (Wt%)
Ester molecule (Tetrahydrofurfuryl acetate) - 10-12% (Wt%)
Epoxide conditioner (1,2-Epoxydodecane) - 0.25-0.30% (Wt%)
Water - 4.75-5.25%.(Wt%)
2. The frothing agent as claimed in claim 1, wherein solid coal
particles are selectively separated under coal froth flotation
condition as a froth phase from remaining solid feed particles as
an aqueous phase in the presence of Improved frother.
3. The frothing agent as claimed in claim 1 wherein the said frother
is used in a dosage ranging between about 0.10 to about
0.2kg/ton of coal.
4. The frothing agent as claimed in claim 1 wherein improvement of
clean coal yield is 5-7% at low ash level as compare to commercial
frother.
5. The Improved frothing agent adaptable to forth flotation process
as substantially describes and Illustrated herein alongwlth
accompanying flaures.

The present invention is directed to a froth flotation process for
beneficiating coal wherein solid coal particles are selectively
separated under coal froth flotation conditions as a froth phase from
remaining solid feed particles as an aqueous phase in the presence of
a frother. The improvement in such process is characterized by a
frother comprising a blended mixture of ester, ketone molecules and
epoxide conditioner.
According to the process of the present invention the frother thereof
is used in a dosage ranging from between about 0.1 to about 0.2
kg/t of fine coal of less than 1/2 mm size.
A further object of the present invention is that the frother may be
added to froth flotation process together with additional collectors,
promoters and/of other frothers. The additional collectors are selected from the group consisting of fuel oils, polymers and esbers. These additional collectors are used in a dosage ranging from between about 0.175 to about to about 0.350 kg/ton of coal.
The present invention has additional detailed features which shall be further described below.