Title of Invention

A COAL FLOTATION PROCESS THROUGH PRE WATER TREATMENT OF RECYCLE WATER FROM COAL BENEFICIATION THICKNER AND INSTALLATION THEREOF

Abstract This invention relates to a coal flotation process through pre water treatment of recycle water from coal beneficiation thickener and feeling the treated water into flotation cell comprising the steps of passing first the recycle to a unit for oil removal; feeding the said oil removed water to a unit provided with active carbon filter for removing suspended inorganics of the water; the resultant water next being treated in an unit provided with iron filter for removal of iron; followed by treating said resultant water in a sodium ion exchange process to remove dissolved inorganic and organic compounds of the resultant water to obtain softened water, which is fed into a flotation cell provided with an impeller for proper mixing of the slurry formed on wetting coal sample and transferred into the flotation cell; additional water is added to the cell; high speed diesel oil as a collector being added into the slurry and conditioned to which conditioned slurry, requisite amount of frother is added and is conditioned; the cell is then filled with water to the marked level of the cell and air inlet valve is then opened to supply air in the cell through a compressor; froth floatation samples are collected and analysed to achieve improved yield of 5-11% at same ash level for untreated water, treated water and tap water when added in the flotation cell on maintaining reduced conductivity, turbidity and hardness of the treated water in the flotation cell. The invention relates also to an installation of coal flotation to carry out the process as narrated above.
Full Text FIELD OF THE INVENTION
The present invention relates to the froth flotation process of finely-divided coal
particles for separation of the ash from carbon and more particularly to a new
flotation feed water treatment process for improving the water quality, which
enhances coal selectivity and recovery in the froth flotation.
BACKGROUND OF THE INVENTION
The separation of fine particles (less than ½ mm) of coal contained in coal slurry
through the use of froth flotation process is well known. Froth flotation processes
involve introducing air into the coal slurry. The hydrophobic particles of coal are
contacted with finely disseminated air bubbles such that the air bubbles become
adhered to the hydrophobic coal 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 hydrophilic particles of impurities
which don't adhere to the air bubbles and which remain suspended in the slurry.
Mining companies often view water quality as an environmental issue. The
importance of water quality as a production related issue in mineral beneficiation
is greatly underestimated at many minerals processing operations. While most
mine sites have comprehensive water balance data for water quantity, the


information regarding the quality of water supplies available on site is limited, inadequate or
non-existent. The seasonal variations in process water quality and changes in the composition
various water streams are not known. Despite the fact that water represent about 80 to 90
percent of the volume of mineral pulp processed in a flotation plant, the influence of process
water composition on flotation performance is often poorly understood.
The process water used at mineral processing operations is made up from a number of available
water sources, which can be classified as recycled water streams or make-up waters. The
cycled water streams are commonly the tailings and concentrate thickener overflows, filtrate
from the concentrate filtration plant and trailing dam return water. Make-up waters can
originate from a variety of sources; surface water (rivers, lakes reservoirs, dams), ground water
(wells and springs), mains water (potable water), treated and untreated sewage waters and
industrial effluents.
Minerals processing plants are increasingly recycling water to reduce demand for fresh water
and minimize the discharge of waste water to the environment. However increasing water
recycling can have adverse effects on process quality and ultimately on the performance of
mineral separation process. The main reason for reduced plant performance due to water
recycling are the accumulation of organic and inorganic compounds in the process water
and increased microbiological activities. Other detrimental effects of water recycling is
cue to increased reagent consumption and inefficient dewatering of tailings and


concentrates. Recycling of water also tend to accumulate very fine suspended particles,
txcessive amounts of slime in the process water also have an adverse effect on mineral
beneficiation processes. The main constituents of process water are dissolved gasses (oxygen,
nitrogen, carbondioxide), colloidal and suspended solids of inorganic and organic nature
(including microorganism: dead or alive), dissolved organics (natural organic matter, residual
reagents, reaction and decomposition by-product of chemical reagents, impurities in the
reagents, metabolites originating form microbiological activities) and inorganic compounds
(acids, alkalis, inorganic salts, metal ions, anion and heavy metals. Input to the chemical
composition of process water are: dissolution of soluble mineral phases present in the ore,
surface oxidation followed by dissolution of mineral particles during grinding and mineral
processing, the chemical composition of various make-up waters and recycled water streams,
and reagent addition during mineral processing.
The beneficial or detrimental impact of process water quality on flotation performance depends
on a number of sub-process attributes: adsorption and / or precipitation of inorganic and
organic species present in the process water onto the surface mineral particles, chemical
reaction between process water constituents and the chemical species present on the surface of
mineral particles and interaction between the chemical and microbiological species
present in the process water and the various reagent species added in solution
during mineral processing. Dissolved chemical species such as calcium, magnesium, iron,
copper, lead zinc, nickel, aluminium, sulfates, phosphates and carbonates also


have a strong effect on the electro kinetic properties of oxide and sulfide minerals, at certain pH
ranges. Several reactions occur at the solid liquid interface which plays an important role in
determining surface adsorption of reagents. Solid-liquid interfacial properties of mineral
particles is significantly effected by the conformation of adsorbed and precipitated reagent
layers, which in turn is determined by solution chemistry. The chemical and microbiological
constituents of process water play a significant role on liquid gas interfacial properties and have
a strong influence on forth height, strength and stability during flotation.
Water chemistry also play an important role in determining the interaction between minerals
present in the ore and the chemical reagent added in the mineral processing plant by altering
the reagent-solution and mineral-solution equilibria. These interactions can include dissolution,
mjcellisation and precipitation of reagents, dissolution of minerals contained in the ore followed
by hydrolysis, complexation, adsorption and precipitation of dissolved chemical species and
reactions between dissolved ions and various reagent species present in the solution. All of the
above mentioned sub process factors ultimately have a significant effects on the efficiency of
mineral processing operations.
In summary, the notability of coal is affected by the presence of dissolved inorganics
and organic in the system. It is observed that the adsorption of Ca increases
slightly with pH up to 8 and then sharply above that value, while Al exhibits a
sharp increase around pH 3-5. The sharp uptake of these metal ions is


governed by the formation of CaOH+ and AIOH+2. These results show that the adsorption of
multivalent species drastically effects the hydrophobicicty of coal and depress the flotation due
to such surface precipitation. Depression of flotation is caused by surface modification due to
such surface precipitation.
i nis invented water treatment circuit reduces dissolved and suspended inorganic impurities
which are represent in different water quality indices like conductivity, total hardness, turbidity
etc. It resulted in improvement in process water quality on removing difficulties of prior state of
art as herein-narrated and therefore achieve enhancement in flotation performance efficiency.
DESCRIPTION OF THE INVENTION
The present invention describes a water treatment process between thickener and flotation
circuit. Process recycle water from thickener passes through the proposed water treatment
circuit for removal or reduction of dissolved impurities from water and feeds into flotation circuit.
The water treatment process reduces the process water total hardness, conductivity and
turbidity. It results in increase in flotation yield about 5-10 % at same ash level.
The present invention will be better understood from the following description with reference to
the accompanying drawings in which
Figure 1 represents in block diagram the water treatment process of the present invention.
Figure 2 represents graphically comparison of coal flotation performance for three different
types of water.

The block diagram of the present water treatment circuit is shown in Figure 1. It comprises oil /
phenol removal, activated carbon filter (ACF), iron removal and sodium exchange softening
steps.

The present invention optionally include many additional detailed features which shall be further
described below.


DETAILED DESCRIPTION OF THE INVENTION
The invention will become more readily apparent with reference to the following
representative example.
In this example, three different type of water named laboratory tap water,
process untreated water, process treated water after passing the treatment
process are employed to study the effect of water chemistry on flotation
performance.
Process untreated water means recycle water of coal beneficiation. This water
passes through laboratory scale water treatment process of the proposed
development, which is explained in Fig. 1. It is described here as process treated
after softening. Water quality of all three water is shown in Table 1.



-
It reflects that dissolved impurities and suspended impurities of process
untreated water is improved after passing through the improved water treatment
process. Conductivity and total dissolved solid (TDS) is reduced by more than
50%. Overall process treated water after softening is better than process
untreated water in terms of water chemistry. Laboratory tap water is having very
less conductivity and turbidity. It is used for benchmarking the water quality
indices and respective flotation performance.
A flotation cell of Denver D-12, 2.5-lit capacity (not shown) 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 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 (litre per minute) with a least
interval of 1 Ipm. The cell has an automatic pulp level controller through make
up water tank and a froth removal system.
For each batch flotation, 250 gms of coal sample are allowed to wet for 1 hour in
a known volume of water. It is transferred in to the 2.5-litre 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 to 5 minutes at the impeller speed of 850
rpm. Then high speed diesel oil (collector) is added and conditioned for 3 to 5
minutes. After conditioning, requisite amount of frother is added. It is again
conditioned for another 3 to 5 minutes. Conditioning of diesel oil and frother
molecules means providing sufficient time for these molecules to adsorb on coal
particle surface before introducing air into the cell. The cell is filled with water up
to the marked height; air inlet valve is opened and kept at 2 Ipm. 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) are dried, weighed and
analyzed for their ash content.
A representative minus 0.5 mm size semi bituminous flotation feed coal sample is
taken in this investigation. The said 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 31 % ash. Size-wise weight and ash distribution 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, methyl isobutyl carbinol (MIBC), and R&D developed
frother are used separately to compare the flotation performance for three
different water. Other variables of flotation process are kept constant.


This frother does not have any chemical reaction with any compound. It adsorb
on the coal surface for altering the surface properties.
Laboratory coal flotation yield % at different ash level for three different type of
water is shown in Table 3.




It clearly shows that on improving the water quality (means reducing the
conductivity and turbidity) coal flotation yield improves drastically for each ash
level and frother. It is observed that laboratory tap water giving maximum yield
at each ash level. Therefore there is 5-10% yield improvement at 11-12% clean
coal ash level on improving the process water quality through invented water
process. So on reducing further conductivity and turbidity of water it is possible
to achieve the flotation performance like with tap water. The same achievement
is shown by graphical representation of improvement in flotation performance by
improving the plant process water quality through invented water treatment
process as shown in Fig.2.
The proposed invention as narrated herein with an embodiment and examples
should not be read and construed in a restricted manner as various modifications
of installation and water treatment step, alterations of parameters and process
conditions and adaptations, are possible within the ambit and scope of the
invention as defined in the appended claims.


WE CLAIM
1. A coal flotation process through pre-water treatment of recycle water from coal
beneficiation thickener and filling the treated water into flotation cell comprising the steps
of passing first the recycle to a unit for oil removal; feeding the said oil removed water to
a unit provided with active carbon filter for removing suspended inorganics of the water;
the resultant water next being treated in an unit provided with iron filter for removal of
iron; followed by treating said resultant water in a sodium ion exchange process to
remove dissolved inorganic and organic compounds of the resultant water to obtain
softened water, which is fed into a flotation cell proved with an impeller for proper mixing
of the slurry formed on wetting coal sample and transferred into the flotation cell;
additional water is added to the cell; high speed diesel oil as a collector being added into
the slurry and conditioned to which conditioned slurry, requisite amount of frother is
added and is conditioned; the cell is then filled with water to the marked level of the cell
and air inlet valve is then opened to supply air in the cell through a compressor; froth
flotation samples are collected and analysed to achieve improved yield of 5-11 % at
same ash level for untreated water, treated water and tap water when added in the
flotation cell on maintaining reduced conductivity, turbidity and hardness of the treated
water in the flotation cell.
2. The coal flotation process as claimed in claim 1, wherein the said 5-11 % yield
improvement is achieved at 11-12 % clean coal ash level on 50 % reduction of total
dissolved solids, total suspended solids, turbidity and conductivity of the untreated water.


3. The coal flotation process as claimed in claim 1 wherein the total hardness
of the process water is reduced through reduction of total dissolved solids
and suspended solids from treated waters by removal of oil and titrations
in active carbon unit iron filter and sodium exchange unit.
4. The coal flotation process as claimed in claim 1 wherein for floatation
treatment of treated water a flotation cell of Denver D-12 of 2.5 litre
capacity is employed for flotation test carried with as a test example on
wetting 250 gms of coal sample having 31% ash for 1 hour in a know
volume of water and then transferred to the flotation cell added with
additional water to maintains required pulp density of 10-14 % solid
content, the slurry so formed being allowed to wet for 3 to 5 mts at an
impeller speed of 850 rpm, adding high speed diesel oil (collector) and
conditioned for 3 to 5 mts, adding requisite amount of R & D developed
frother and conditioned for 3 to 5 mts, the flotation cell then being filled
with water upto the marked height of the cell, thereafter providing air
supply at 2 Ipm via a compressor through inlet pipe to the cell, collecting
froth samples after 30, 60, 120 and 240 seconds of flotation, the froth
products and the tailings remained inside the cell are finally dried,
weighed and analysed for their ash contents according to ASTM D 3174-
73 standard.
5. The coal flotation process as claimed in the preceding claims wherein the
flotation performance is characterize evaluated with three different type of
water namely laboratory tap water, process untreated water, process


treated water on passing through water treatment cycle on evaluation of pH,
conductivity, total dissolved solids and suspended solids, turbidity, M-alkanity
and oil before being fed into the flotation on evaluation of coal flotation yield
% at different ash level for the said three typed water corresponding to
maintaining material characters of treated water in the flotation cell of
conductivity and turbidity and applying a developed frother in the flotation
cell on comparison of the flotation yield of treated water and process water
with tap water, which gives maximum yield at each ash level and evaluating
flotation yield achievement for process treated and untreated water.
6. The flotation process as claimed in the preceding claims where in the
developed frother is in combination of 2,6- Dimethyl-4-Heptanone,
Tetrahydro furfuryl acetate, 1,2 epoxydodecane and water.
7. The flotation process as claimed in claim 5 wherein the process untreated
water means recycle water of coal beneficiation and process treated water
means the resulted softened water on treating the said recycle water of
coal beneficiation through the water treatment cycle.
8. The flotation process as claimed in the preceding claims wherein the
conductivity and turbidity and corresponding flotation yield on treated
waters in flotation cell is evaluated by using conventional methyl isobutyl
carbinol (MIBC) frother and developed frother separately and are
maintained as 220,1 and 40; 390, 1.5 and 32; and 1400, 20 and 13 for

tap water, treated water and process water respectively when conventional
frother MIBC is used and the same is maintained as 220, 1 and 40; 390, 1.5
and 41; and 1400,20 and 30 respectively for the said three types of water
when treated with developed frother.
9. An installation for coal flotation through prewater treatment of recycle
water from coal beneficiation thickner and feeding the pretreated water
into a flotation cell to carry out the floation process as claimed in claim 1
comprising a water treatment process recycle plant of oil removal unit,
activated carbon filter (ACF) unit, iron removal unit and sodium exchange
process unit through which the recycle water is treated and fed into a
flotation cell of Denover D-12 of 2.5 litre capacity comprising of a baffle
arrangement at bottom to avoid swirling of the slurry within the cell; an
impeller with a speed regulator for proper mixing of slurry; a compressor
to supply air to the cell in the range of 0-20 Ipm in an interval of 1 Ipm, an
automatic pulp level controller through make up water tank and a froth
removal system.


This invention relates to a coal flotation process through pre water treatment of
recycle water from coal beneficiation thickener and feeling the treated water into
flotation cell comprising the steps of passing first the recycle to a unit for oil
removal; feeding the said oil removed water to a unit provided with active
carbon filter for removing suspended inorganics of the water; the resultant water
next being treated in an unit provided with iron filter for removal of iron;
followed by treating said resultant water in a sodium ion exchange process to
remove dissolved inorganic and organic compounds of the resultant water to
obtain softened water, which is fed into a flotation cell provided with an impeller
for proper mixing of the slurry formed on wetting coal sample and transferred
into the flotation cell; additional water is added to the cell; high speed diesel oil
as a collector being added into the slurry and conditioned to which conditioned
slurry, requisite amount of frother is added and is conditioned; the cell is then
filled with water to the marked level of the cell and air inlet valve is then opened
to supply air in the cell through a compressor; froth floatation samples are
collected and analysed to achieve improved yield of 5-11% at same ash level for
untreated water, treated water and tap water when added in the flotation cell on
maintaining reduced conductivity, turbidity and hardness of the treated water in
the flotation cell.
The invention relates also to an installation of coal flotation to carry out the
process as narrated above.

Documents:

00151-kol-2008-abstract.pdf

00151-kol-2008-claims.pdf

00151-kol-2008-correspondence others.pdf

00151-kol-2008-description complete.pdf

00151-kol-2008-drawings.pdf

00151-kol-2008-form 1.pdf

00151-kol-2008-form 2.pdf

00151-kol-2008-form 3.pdf

00151-kol-2008-gpa.pdf

151-KOL-2008-AMENDEND CLAIMS.pdf

151-KOL-2008-CORRESPONDENCE.pdf

151-KOL-2008-DESCRIPTION (COMPLETE)-1.1.pdf

151-KOL-2008-EXAMINATION REPORT REPLY RECIEVED.pdf

151-KOL-2008-EXAMINATION REPORT.pdf

151-KOL-2008-FORM 1-1.1.pdf

151-KOL-2008-FORM 13.pdf

151-kol-2008-form 18.pdf

151-KOL-2008-FORM 2-1.1.pdf

151-KOL-2008-FORM 3.pdf

151-KOL-2008-GPA.pdf

151-KOL-2008-GRANTED-ABSTRACT.pdf

151-KOL-2008-GRANTED-CLAIMS.pdf

151-KOL-2008-GRANTED-DESCRIPTION (COMPLETE).pdf

151-KOL-2008-GRANTED-DRAWINGS.pdf

151-KOL-2008-GRANTED-FORM 1.pdf

151-KOL-2008-GRANTED-FORM 2.pdf

151-KOL-2008-GRANTED-SPECIFICATION.pdf

151-KOL-2008-OTHERS-1.1.pdf

151-KOL-2008-REPLY TO EXAMINATION REPORT.pdf

abstract-00151-kol-2008.jpg


Patent Number 249688
Indian Patent Application Number 151/KOL/2008
PG Journal Number 44/2011
Publication Date 04-Nov-2011
Grant Date 02-Nov-2011
Date of Filing 25-Jan-2008
Name of Patentee TATA STEEL LIMITED
Applicant Address JAMSHEDPUR
Inventors:
# Inventor's Name Inventor's Address
1 ASHIWANI KUMAR GUPTA C/O TATA STEEL LIMITED, JAMSHEDPUR - 831 001
2 P. K. BANERJEE C/O TATA STEEL LIMITED, JAMSHEDPUR 831 001
PCT International Classification Number B03D1/00; B03D1/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA