CHARACTERIZATION AND WASHABILITY STUDIES OF RAW COAL OF BALUCHISTAN

International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163
Issue 08, Volume 5 (August 2018) www.ijirae.com
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CHARACTERIZATION AND WASHABILITY STUDIES
OF RAW COAL OF BALUCHISTAN
Khurum Shehzad Buzdar*
Pakistan Council of Scientific & Industrial Research Lab, Quetta, Pakistan
the_buzdar96@yahoo.com
Huma Ayub
chemist.huma@gmail.com
Zaheer ud din
zaheer_pcsirqta@yahoo.com
Hibba Ammanat ali
hibaali909@gmail.com
Javeria Ayub
The Balochistan University of Information Technology, Quetta, Pakistan
Javeria.ayub@buitms.edu.pk
Engr.jalil zafar
Pakistan Standard and Quality Control Authority, Karachi, Pakistan
zafar@yahoo.com
Manuscript History
Number: IJIRAE/RS/Vol.05/Issue08/AUAE10080
Received: 11, August 2018
Final Correction: 21, August 2018
Final Accepted: 25, August 2018
Published: August 2018
Citation: Buzdar, Ayub, Zaheer, Hibba, Javeria & zafar (2018). Characterization and Washability studies of Raw
Coal of Baluchistan. International Journal of Innovative Research in Advanced Engineering, Volume V, 256-293.
doi://10.26562/IJIRAE.2018.AUAE10080
Editor: Dr.A.Arul L.S, Chief Editor, IJIRAE, AM Publications, India
Copyright: ©2018 This is an open access article distributed under the terms of the Creative Commons Attribution
License, Which Permits unrestricted use, distribution, and reproduction in any medium, provided the original author
and source are credited
Abstract— Five mesh sizes of -1/2 +3/8,-3/8+4,-1+3/4,-3/4+1/2 and -4+10. The four specific gravity solutions
were prepared for carrying out the wash ability studies of Degari Coal of Balochistan by ZnCl2 which are as
followed 1.25, 1.3, 1.35, 1.4 respectively. The wash ability studies of Degari Coal have been completed. The results
showed that the Calorific Value of Degari Coal have been up-graded to 13565 btu/lb which was earlier 9875
btu/lb and the ash content is reduced from 50% down to 30% with an increase in Fixed Carbon up to 4%. The
maximum recovery of 90% was obtained during the float sink of -3/4”+1/2” on 1.40 specific gravity solution. The
results which were obtained 2.39, 5.62, 48.15, 46.25, 13565 and 3.36 were moisture, ash, volatile matter, fixed
carbon, Calorific value and Sulphur respectively. The weight recovery on the specific gravity solution is 90% with
the maximum calorific value of 13565 btu/lb.
Keywords— Dense medium separation; float and sink method; Calorific value; Specific gravity;
I. INTRODUCTION
The process in which the contaminant is removed from coal and its quality is upgraded for the suitable application
of end users. Coal is used either as a chemical agent and energy sources. This processing is known as coal washing
/cleaning of coal. It is a pre-combustion process in that some of impurities are removed before burning of coal.

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The coal cleaning technology is based on that the coal is lighter than its associated rocks and impurities. Coal
cleaning method can be physical or chemical. Pyritic sulphur of about 30 to 50% and approximately 60% of ash
forming mineral can be removed. As a result of washing, SO2 emission can be decreased about 50% after washing
in an ideal condition.
In Baluchistan, there are mainly six mining areas which produce coal and coal mining is in progress. These are
Khost, Harnai, Pir Ismail, Duki, shahrig, Sor Rang and Ziarat. Recently mining areas are Mach and chamalang.
Experimental coal is from degari coal field. Environmental pollution is caused due to the impurities of coal. It
contains Sulphates, Calcite, Pyrite, Ca2CO3, Oxides which combine with silica to form complexes. It tends to form
coal ash. Clinkering temperature is decreased because of the presence of sulphate in the coal. In proximate
analysis of coal of Degari the Ash, Moisture, Volatile matter, Fixed Carbon, Calorific value and Sulphur was done.
Fig 1 Raw coal and coal after wash ability by float and sink method.
TABLE 1- PROXIMATE ANALYSIS OF THE RAW COAL SAMPLE.
S.No Test Result
01 Moisture 2.58%
02 Ash 10.18%
03 Volatile Matter 47.25%
04 Fixed Carbon 42.57%
05 Calorific Value 9875 btu/lb
06 Sulfur 3.37%
proximate analysis of raw coal was done in which the following test have been done moisture, ash, volatile
matter, fixed carbon, calorific value and sulphur. The wash ability of coal was shown by the graph showing the
result of series of float and sink tests [9]. The coal washing process depends on the physical property variations i.e.
it depends on the specific gravity and wetting characteristics of coal which make it easy to wash or difficult to
wash. After millions of years passed the coal which is derived from vegetable debris is firm sedimentary, brittle,
combustible rock. The quality of coal varies with the rank from peat to lignite, from lignite to bituminous, from
bituminous to semi–anthracite and from semi-anthracite to anthracite. About 63.26% of coal is utilized for
electricity production in Pakistan.
The coal when comes from mining consist of many impurities like magnesium sulphate, sulphur in form of pyrites,
slate and fire clay. These materials have higher specific gravity than the pure coal which is 1.28 or 1.30. The coal is
purchased on different specification like Ash content, Sulphur and size. Therefore the coal must be screened to
size. The International Energy agency (IEA) reported that about 60% of demand will grow to next 30 years in the
developing countries [1].
Environment is polluted by the burning of low grade coal which contains silica, pyrite, calcite, sulphate, oxide
which form complexes upon reacting with the other minerals. It tends to form coal ash, known as high ash content
which is difficult to clean [6]. As energy demand is increasing day by day, so there is a need for cleaner energy
without pollution to maintain environmental sustainability. The coal industry recognizes when it meet the
challenges of environmental sustainability and reduce the Greenhouse gases. The coal is basically plant debris. It
is difficult to wash the coal contain thin bans of coal rather contain the proportion of bright coal. Finely divided
plant degradation products have the fine ash then the bright coal. This ash is basically the structurally part of coal
itself and cannot be separated by mechanical means.

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The ash forming content can be removing in laboratory by float and sink method. Coal from mines have all type of
densities present, it can be divided into the lightest fragments of bright coal to the heaviest coal particles of shale
and pyrite. The coal differs due to material present there. This factor determines in large degree of responsibility
of coal beneficiation by washing. The ordinary coal washing processes effect the separation between coal and its
impurities on the basis of their specific gravities. The possibilities of coal washing is to separate the raw coal
mixture into coal and impurity by immersing it in a solution with specific gravity intermediate between that coal
and impurity. The portion of coal divided into floats and sink portions. The portion of the sample with specific
gravity less than that of solution is floats portion. The sink portion with the specific gravity more than that of
specific gravity of solution. The coal separation take place in number of portion depends on different specific
gravity, each made up of particles of restricted range of differences in specific gravity. Such separation has been
found most useful in coal washing and known as specific –gravity analysis [2].
The float and sink separation method into specific gravity fraction entirely depends upon the differences in
specific gravity of particles. Settling and stratification inhibition in coal washing depends on the important factor
of shape. Float and Sink method is an ideal and perfect separation method that can be approached as a limit in
practice by coal washing machines [3].
The moisture content of sample affects the float and sink operation because of its dependence on specific gravities.
The apparent specific gravity of coal depends on the moisture and air held within the coal sample. Specific gravity
varies with the moisture content. It also influence the results obtained by float and sink test. Therefore the sample
is completely air dried before the float and sink test [4].
The ordinary coal-washing processes effects the separation between coal and impurity because of the difference
in specific gravities of these components. In studying the possibilities of improving the coal by washing, it has
therefore long been common practice to separate the raw coal mixture into coal and impurity by immersing it in a
solution with specific gravity intermediate between that coal and impurity. The portion of the sample with specific
gravity less than that of the solution floats and the portion with the specific gravity more than that of the solution
sink. By the use of series of such solutions, each of successively higher specific gravity, a sample of coal may be
separated into a number of portions, each made up of particles of restricted range of differences in specific gravity.
Such a separation has been found most useful in coal-washing and has been called “specific-gravity analysis” [6].
The ordinary coal –washing process effects the separation between coal and impurity because of the difference in
specific gravities of these components. The portion of the sample with specific gravity less than that of the
solution that float and the portion with the specific gravity more than that of the solution is sink. Combustible can
be separated by the best crushing of the coal which results in the liberation of large amount of combustibles [7].
II. MATERIALS AND METHODS
Wash ability first steps comprised of desired specific gravity solution preparation by dissolving ZnCl2 in different
ratios (Iqbal, Ehsan et al. 2011).
A. Sample Collection
Coal samples were collected from different coal mines of district dagari. Crushing was done because the sample
was in form of lumps. The samples were crushed by jaw crusher and then passed through the disc mill to obtain a
powder of different mesh sizes. Five screens of sizes -1/2 +3/8,-3/8+4,-1+3/4,-3/4+1/2 and -4+10 respectively
were used for screening of the samples.
B. Float-And-Sink Test
Several testing methods have been used for treating raw coal to separate coal and dirt particles present in
particular sample, more or less analogous to the separation made by washing with the object of finding an
approximate measure of the wash ability of coal by an inexpensive measure. It contains the minerals matter which
was associated with underground and some other materials getting mined up during handling. Cleaning of coal
depends upon the shape and size of particles. The specific gravity of raw coal varies directly which depends on ash
content, the higher ash material will be concentrated in the part that sinks and the clean coal will gather in the
part that floats [8].
Cleaning process generally depends upon differences in the density of clean coal and its impurities. They suitably
remove the free dirt but not the inherent dirt present in coal particles. The extent of removal of free dirt
associated with a coal to improvement in quality is more commonly known as the “wash ability” of coal and is
more commonly indicated by the “float and sink” analysis of coal samples.

_________________________________________________________________________________________________
C. Experimental Procedure
About 1000g coal sample of 5 different sizes were accurately weighed by a digital balance. Solution having
different specific gravity varying from 1.25 to 1.4 is prepared by using ZnCl2. The prepared solution was taken in
beakers and arranged in the order of increasing specific gravities (1.25, 1.3, 1.35, 1.40). The sample is first placed
in the lowest specific gravity liquid. The fraction higher than the liquid floats and heavier ore sinks. The portion
which floats on a particular specific gravity known as float fraction and the portion which sinks are known as sink
fraction. In this way, the float and sink fractions of different specific gravities are collected and weighed, taking
care that no coal particles are lost. For determination of the ash content, ASTM methods were implied. The results
were tabulated for analysing the wash ability characteristic of the coal samples. The wash ability curves were
plotted taking total floats vs. ash, total sinks vs. ash [8]. When the coal sample is heated under specified conditions,
then it classifies the tests into four groups: moisture; volatile matter, fixed carbon; Ash, the inorganic residue
remaining after combustion; Calorific Values. ASTM methods were followed for testing of coal. Calorific Value was
calculated by using bomb calorie meter.
III.RESULTS AND DISCUSSION
Weight recovery of coal on different mesh sizes and solution with different specific gravities are as follows. 90 %
of weight recovery was done which have maximum calorific value 13565 Btu at mesh size of -3/4+1/2.
TABLE II- RESULTS OF COAL AFTER FLOAT AND SINK METHOD BY WEIGHT RECOVERY ON DIFFERENT SIZES
Specific gravities -1+3/4 -3/4+1/2 -1/2+3/8 -3/8+4 -4+10
Float Sink Float Sink Float Sink Float Sink Float Sink
1.25 88 904 80 915 106 876 114 880 150 822
1.30 456 540 602 396 584 410 681 269 610 360
1.35 790 208 800 195 782 212 793 182 785 195
1.40 895 100 900 100 870 126 838 137 847 123
1) Sample 1:
TABLE III- CHEMICAL ANALYSIS OF SINK AND FLOAT COAL OF SIZE -1+3/4
Size -1+3/4 Specific
gravity
Moisture
%
Ash % Volatile
Matter%
Fixed
Carbon%
Calorific value
BTU
F 1.25 2.50 10.35 48.46 40.96 11162
S 2.59 10.58 49.11 40.54 10949
F 1.3 2.41 6.14 50.03 43.83 11993
S 2.58 16.20 44.60 39.20 9678
F 1.35 2.48 5.61 48.65 45.74 12720
S 2.49 32.24 38.50 29.26 6472
F 1.4 2.64 5.98 49.62 44.40 12765
S 2.51 35.80 36.90 27.30 5613
Fig 2 Wash ability plot of coal size -1+3/4

_________________________________________________________________________________________________
At mesh size of -1+3/4 the range of moisture, Ash, V.M, F.C is about 2.41-2.64%, 5.61-35.80 %, 36.90-50.03%,
27.30-45.75% at 1.3 specific gravity of solution respectively. Quality of coal was determined by the fixed carbon
and volatile matter percentage. Coal having maximum calorific value shows is 12765.
2) Sample 2:
TABLE IV- CHEMICAL ANALYSIS OF SINK AND FLOAT COAL OF SIZE -3/4+1/2
Size-3/4+1/2 Specific
gravity
Moisture
%
Ash % Volatile
Matter%
Fixed
Carbon%
Calorific value
BTU
F 1.25 2.52 10.21 49.67 40.12 11218
S 2.65 10.87 48.2 40.92 11647
F 1.3 2.56 4.94 50.92 44.14 12173
S 2.61 15.02 44.81 40.17 10786
F 1.35 2.50 5.08 49.06 45.86 12502
S 2.48 41.81 34.58 23.61 6017
F 1.4 2.39 5.62 48.15 46.23 13565
S 2.44 41.48 35.90 22.62 5163
Fig.3 Wash ability plot of coal size ¾+1/2
Coal size of -3/4+1/2 with moisture, Ash , V.M, F.C, 2.39-2.65% ,4.94-41.48%,34.58-50.92% ,22.62-46.23% at the
specific gravity solution of 1.25 respectively and having maximum calorific value of 13565btu.
Fig4 Coal product after Wash ability of coal

_________________________________________________________________________________________________
3) Sample 3:
TABLE V- CHEMICAL ANALYSIS OF SINK AND FLOAT COAL OF SIZE -1/2+3/8
Size -1/2+3/8 Specific
gravity
Moisture
%
Ash % Volatile
Matter%
Fixed
Carbon%
Calorific value
BTU
F 1.25 2.58 10.79 48.72 40.49 11028
S 2.51 9.98 49.12 40.90 10928
F 1.3 2.44 4.51 50.13 45.18 12473
S 2.32 14.29 46.41 39.30 10876
F 1.35 2.28 5.58 49.82 44.60 12521`
S 2.48 28.62 38.44 32.94 8723
F 1.4 2.46 5.35 50.52 44.13 12838
S 2.40 25.60 43.02 31.38 8565
Fig 5 Wash ability plot of coal size -1/2+3/8
4) Sample 4:
Coal size of -1/2+3/4 have moisture, Ash, V.M ,F.C 2.28-2.58%, 4.51-28.62%, 38.44-50.52%, 31.38-45.18% at
different specific gravity solution. Ash value is maximum at specific gravity of 1.3 is 28.62%. At specific gravity of
1.4 the float coal has maximum V.M of 50.52% and minimum value of 38.44% at specific gravity of 1.35 sink coal.
Maximum fixed carbon value 45.18% at specific gravity of 1.30.Calorific value at specific gravity of 1.4 is 12838
with 2.40%, 25.60%, 43.02% and 31.38% of moisture, ash, V.M and F.C respectively.
TABLE VI - CHEMICAL ANALYSIS OF SINK AND FLOAT COAL OF SIZE -3/8+4
At mesh size of -3/8+4 have moisture in range of 2.14-2.34%.maximum 2.34% and minimum 2.14 %moisture
were at specific gravity of 1.25and 1.30 respectively. Sink coal obtained at specific gravity of 1.35 have maximum
ash content 36.24%. Volatile matter of coal range from 33.53-47.64%. Maximum value of V.M is 47.64% at specific
gravity of 1.35 of float coal. F.C is between 28.42-48.53%. Maximum calorific value is 13168 at specific gravity of
1.4.
Size -3/8+4 Specific
gravity
Moisture
%
Ash % Volatile
Matter%
Fixed
Carbon%
Calorific value
BTU
F 1.25 2.34 0.96 46.85 43.74 12285
S 2.26 10.11 46.68 43.21 10131
F 1.3 2.25 6.08 46.98 46.94 11867
S 2.14 17.85 39.41 42.74 9178
F 1.35 2.28 5.81 47.64 46.55 12021
S 2.05 36.24 35.34 28.42 5855
F 1.4 2.08 5.86 45.61 48.53 13168
S 2.15 33.14 33.53 33.33 6214

_________________________________________________________________________________________________
Fig 6 Wash ability plot of coal size -3/8+4
5) Sample 5:
TABLE VII- CHEMICAL ANALYSIS OF SINK AND FLOAT COAL OF SIZE -4+10
Size -4+10 Specific
gravity
Moisture
%
Ash % Volatile
Matter%
Fixed
Carbon%
Calorific value
BTU
F 1.25 2.08 9.90 44.88 45.22 11342
S 2.19 11.40 43.21 45.33 10765
F 1.3 2.30 5.27 47.49 47.24 10290
S 2.32 18.07 40.12 41.81 9504
F 1.35 2.40 8.22 47.34 44.44 10837
S 2.35 31.70 37.31 30.99 7281
F 1.4 2.29 5.59 47.06 47.35 12690
S 2.38 38.02 32.69 29.29 6319
Fig 7 Wash ability plot of coal size -4+10
The moisture, ash, V.M, F.C having range of 2.08-2.40%, 5.27-38.02%, 32.69-47.49% and 29.29-47.49%
respectively. The maximum calorific value which is obtained is 12690 btu.
IV. CONCLUSIONS
Five mesh sizes of -1/2 +3/8,-3/8+4,-1+3/4,-3/4+1/2 and -4+10 have been prepared after screen testing. The
four specific gravity solutions were prepared for carrying out the wash ability studies of Degari Coal of
Baluchistan by ZnCl2 which were as follows 1.25, 1.3, 1.35, and 1.4 respectively. The washability studies of Degari
Coal have been completed.

_________________________________________________________________________________________________
The results showed that the Calorific Value of Degari Coal have been up-graded to 13565 btu/lb which was earlier
9875btu/lb and the Ash content is reduced from 50% down to 30% with an increase in Fixed Carbon about up to
4%. The maximum recovery of 90% was obtained during the float sink of -3/4”+1/2” on 1.40 specific gravity
solution. The results which were obtained 2.39, 5.62, 48.15, 46.25,13565 and 3.36 were moisture, ash, volatile
matter, fixed carbon, Calorific value and Sulphur respectively. The weight recovery on the specific gravity solution
is 90% with the maximum calorific value of 13565.
ACKNOWLEDGMENT
All authors are thankful to ministry of science and technology PCSIR laboratories Quetta for providing all facilities
to complete the project and for providing all support during the completion of project.
REFERENCES
1. Sarkar, S. (1989). Fuels and Combustion, Orient Blackswan.
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Geology 75(1): 40-48.
3. Nimaje, D. and D. Tripathy (2016). "Characterization of some Indian coals to assess their liability to
spontaneous combustion." Fuel 163: 139-147
4. Huggins, F. E. (2002). "Overview of analytical methods for inorganic constituents in coal." International Journal
of Coal Geology 50(1): 169-214.
5. Iqbal, A., et al. (2011). "Analysis of Dense Medium Beneficiation of Dandot Coal for Use in Cement Industry in
Pakistan." Journal of Quality and Technology Management 7(1): 115-130.
6. Jha, G., et al. (2010). Washability studies and characterization of cleans of coking coal sample from BCCL, CIL,
India. Proceedings of the XI International Seminar on Mineral Processing Technology (MPT-2010), Allied
Publishers, New Delhi.
7. Latif, A., et al. (1999). "Advances in Coal Cleaning." Paper of American Patent 3: 1-2.
8. Mishra, A. (2009). Assessment of coal quality of some Indian coals.
9. Wurst, H. B., et al. (2013). Washability Monitor for Coal Utilizing Optical and X-Ray Analysis Techniques.
International Coal Preparation Conference, Istanbul.

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