FIELD OF THE INVENTION
The present invention relates generally to methods and systems for production of vitrinite
rich hydrocarbons, clean coals and or other such products from various coals by using
combination of float & sink and solvent extraction treatment method which selectively
separate the vitrinite rich content suitable for coke making.
BACKGROUND OF THE INVENTION
Coal structure and composition
Coal is a fossil fuel created from the remains of plants that lived and died millions of years
ago when parts of the earth were covered with huge swampy forests. Millions of years ago,
dead plant matter fell into the swampy water and over the years, a thick layer of dead plants
lay decaying at the bottom of the swamps. Over time, the surface and climate of the earth
changed, and more water and dirt washed in, halting the decay process. The weight of the top
layers of water and dirt packed down the lower layers of plant matter. Under heat and
pressure, this plant matter underwent chemical and physical changes, pushing out oxygen and
leaving rich hydrocarbon deposits. What once had been plants gradually turned into coal.Coal
is a sedimentary rock composed of two categories of substances: organic carbonaceous
matter, termed macerals, inorganic minerals. Appliedto coal, the term mineral matter is an
inclusive term that refers to the mineralogicalphases as well as to all other inorganic elements
in the coal; that is, theelements that are bonded in various ways to the organic (C,H,O,N,S)
components.Macerals are the various organic components that make up coal and control its
overall behaviour. Under the microscope the macerals fall in to three major groups: liptinite,
vitrinite, and inertinite. The liptinite groupis derived from the waxy and resinous parts of
plants and mainlyconsists of sporinite, resinite, and cutinite derived respectivelyfrom plants
pores, resins, and cuticles. The vitrinite group isderived from coalified woody tissue and is
the dominant group inmost coals. The inertinite group is derivedfrom woody tissue that has
been altered by fire or biochemicalcharring.

Concentration of maceral groups by different methods
Maceral separation by hand picking was reported by Stach, E. (in "Textbook of Coal
Petrology" 3rd Ed; Stach, E. Ed.; GebruderBorntraeger: Berlin, 1982; p. 172) and Murchison
et al. (Fuel 1963, 42, 141).Maceral separation using sink-float methods were described and
reported by Kroger et al. (Gluckauf 1957, 93, 122), Van Krevelen et al. (Fuel 1957, 36, 321)
and Fenton and Smith (Gas World 1959, 54, 81) in a paper. Their efforts resulted in
concentrations enriched in the three main maceral groups. However,these enrichments were
not good enough to give definitivecharacterization data.Sink-float techniques have had only
limited success in separating single macerals. Some researchers Dyrkacz and others (Sep. Sci
and Tech. 1981, 16, No. 10, 157l-1588; Fuel 1982, 61, 3-12; Fuel 1984, 63, 1367-73) tried
density gradient centrifugation technique for maceral separation. In this process, micron size
coal sample was demineralized with HF and HCl and then put the sample in centrifuge. After
centrifugation, sample is filtered, weighed and dried. They plotted the density and weight of
each fraction, which shows maceral composition of the sample. A U.S. patent No. 2497790,
issued on Feb. 14, 1950, Pauvrasseau et al. talked about sink and float process for the
separation of coal from its impurities.
In U.S. patent No. 0287828, issued on Nov. 10, 2010;Flemming et al. disclosed a commercial
scale process for extracting reactive macerals from the communited coal as froth from the top
of a deep column flotation cell and, dewatering the extracted macerals. In another U.S. patent
No. 4377473, issued on Mar. 22, 1983, Laros et al. mentioned a method for separating the
exinite group macerals from the total coal by froth flotation in the presence of at least one
short chain alcohol forthing agent and at least one methyl polyglycol type frothing agent. In
another U.S. patent No. 4388181, issued on Jun. 14, 1983,Rainis et al. disclosed a method for
the production of metallurgical grade coal and low ash coal by the combination of flotation
and selective agglomeration. In another U.S. patent No. 5705139, issued on Jan. 6, 1998,
Stiller et al. disclosed a method of producing high quality, high purity, isotropic graphite
from the solid extracts obtained by the non-destructive solvent treatment of coal. In our U.S.
patent No. US8262751, issued on Sep 11, 2012, Biswas et al. disclosed a solvent extraction
process in which low ash coal can be produced from high ash coal. Moothi et al. (Carbon
2012, 50, 2679-90) presented that the most successful components in terms of yield and

purity of carbon nanotube (CNT) production were found to be the vitrinite and liptinite group
macerals. So, production of CNT from extracted/separated vitrinite will increase its purity
and yield.
In all these patents and papers, they have used sink-float, column flotation, density gradient
centrifugation, solvent extraction and leaching techniques for maceral separation and coal
beneficiation. A shortcoming of these techniques is; products obtained from these processes
are mixture of different types of macerals, which needed further treatment to separate them
out. Also, these techniques were used mostly in isolation. Hence, there is a need to use
combination of different techniques for better separation. Here, we used combination of sink-
float and solvent extraction method to get pure maceral e.g., vitrinite.
OBJECT OF THE INVENTION
An object of the present invention is to produce vitrinite rich coal or hydrocarbons from the
treatment of coals using combination of sink-float and solvent extraction method.
Another objective of the invention is to imrove the liberation properties of coal.
SUMMARY OF THE INVENTION
The invention is a process for separation of vitrinite from coal, comprising the steps of
grinding coal to particle size less than 500 micron, separating the coal from its impurities as
float by sink-float test and extracting vitrinite reach content from the float by solvent
extraction.
The process is designed to liberate and recover the vitrinite from the coal. This provides a
usable end product having good coking properties from high ash coking and non-coking coal.
The grinding process preferably includes only dry grinding stages. The target is to reduce the
particles size less than 500 micron before commencing the sink-float test. The grinding
process includes grinding in the mill and then sieving. The fine coal sample undergoes sink-
float test. Sink-float test conducted using various liquid mixtures of different densities from

1.3 to 2. The float at each density was dried and weighed. The weight fraction was noted
against each density. Each float sample was sent for petrography test, wherein
microphotographs were captured. The maceral composition was determined by these
microphotographs. Further, same float sample was subjected to solvent extraction
experiments. In the extraction step, coal sample of each float fraction along with solvent
mixture of N-Methyl-2-pyrollidone (NMP) and Ethylenediamine (EDA) put into round
bottom flask and heated upto boiling point of the mixture. After completion of extraction,
dissolved coal in solvent and un-dissolved coal was separated using wire mesh. The dissolved
coal and solvent wereput into water for precipitation of dissolved coal. The dissolved and un-
dissolved samples were washed with water and dried in the oven. Dried dissolved coal
sample was sent for petrography test, wherein different microphotographs of macerals were
taken. These microphotographs were compared with microphotographs of float sample. The
Free Swelling Index (FSI) test was also performed on dried dissolved coal sample to see the
coking potential of the same.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1- Block diagram of the process
Fig. 2- Petrography image of raw coal
Fig.3- Petrography image of float 1.5
Fig. 4- Petrography image of extracted vitrinte of 1.5 float
Fig.5- Petrography image of reject from 1.5 float extraction.
Here, the process flow is shown which depicts extraction of vitrinite from coal using different
unit operations.
DETAILED DESCRIPTION OF THE INVENTION
A process is developed for separation of vitrinite and inertinite from the coal. The coal may
be used as ROM or washed. Coal in either ROM or washed condition is subsequently
processed in the same manner. The coal is stored in container. The raw coal is consists of
different macerals such as vitrinite, exinite and inertinite. The stored coal is crushed and/or
grinded depending on the size of the coal using the crushing and/or grinding mills. The
grinded coal is sieved to the desired particles size and stored for further processing. Desir

amount of coal sample is taken out from the sieved coal. The said coal is treated using sink-
float technique, wherein different density liquids are prepared for the coal treatment. At each
density, a float and a sink can be separated out. The sink sample is treated in next density cut.
Each float sample is dried, weighed and stored for further processing. Float sample mostly
contains vitrinite and inertinite as macerals distribution. The float sample is thentreated with
solvents using solvent extraction techniques. Amine based solvents are used. The coal is
mixed with solvents and heated to its boiling point. Once the extraction is over, the extracted
(vitrinite rich) material is separated out from residue (inertinite rich) using filters, evaporator,
precipitator and distillation. The extracted material is sent for petrography and coking test.
The extracted material mainly consists of vitrinite while the residue mostly contains
inertinite. FSI test shows the coking potential of the vitrinite rich material.
Referring to Fig. 1 a process flow is explained in which vitrinite was extracted from the coal.
Coal sample in run-of-mine (ROM) condition is taken for the test. The coal sample is grinded
in ball mill and sieved to less than 500 micron size particles. Representative sample is drawn
from bulk grind sample by coning and quartering method. The mass of the sample required
depends on the size of the coal. The sink-float test is performed on 500 g of this sample. For
the sink-float test, different densities liquid is prepared. For liquid density 1.3 to 1.6, the
mixture of Benzene and Tetra chloro-ethylene is used. For liquid density 1.7 to 2.0, the
mixture of Tetra chloro ethylene and bromoform is used. The liquid density is measured by
hydrometer. High density liquid was prepared of different densities starting from 1.3 to 2.0
by adding the chemicals in certain ratio. Take 1.3 density of heavy liquid into a clean glass
container and slowly add known quantity of sample, in this case it is 500g. Mix the solution
with clean glass rod. Quantity of sample and settling time depend upon the size of sample
material.Allow the particles to settle down completely and wait until a clear demarcation
between the float and sink products is seen. Separate the float product using a wire mesh
spoon and/or filtering on filter paper by pouring the float product liquid through a funnelfitted
with filter paper to a beaker, by slow decantation. Then separate the sink material and the
liquid by filtering on filter paper. Wash the collected sink-float products with benzene and
filter the benzene and use for subsequent washing. Dry the float and sink on hot plate and
weigh it. Add sink material to higher density liquid than previous liquid (say 1.4, 1.5 and so
on) and repeat the process. At the end of process, the liquids used need to be kept in clean

bottles and can be reused after checking its gravity. The dry float sample of each density is
weigh and sent for petrography test.
Vitrinite is extracted from each float sample by solvent extraction method. For each
extraction test, 10 g of coal sample was placed in a 250 mL round bottom flask (RBF) fitted
with a reflux condenser and containing 5 mL Ethylenediamine (EDA) and 95 mL of N-
Methyl-2-Pyrrolidone (NMP). Extraction was done for 1 h. After the extraction, the refluxed
mix was allowed to cool for couple of minutes. RBF was taken out and filtered in a conical
flask-funnel arrangement. 500 BS mesh stainless steel wire sheet was used for filtration.
Filtration separates the refluxed mix in two parts (i) residue and (ii) filtrate (vitrinite rich
extracted material with solvents). Residue is washed thoroughly with an anti-solvent for the
removal of the solvents from the residue. After drying and weighing, these residues are
subjected to ash analysis.
The filtrate is actually extract containing very low ash coal. This extract is taken in a RBF
and fitted with the plane wall condenser through distilling adopter. The other end of the
condenser is fitted with a RBF through a receiving adopter. Around 75-80% of solvent is
recovered in distillation. The remaining concentrated vitrinite rich material is taken for
precipitation.
For precipitation an anti solvent (water) was taken in a 500 mL beaker. Concentrated vitrinite
rich extract was then added in to the water. It resulted in precipitation of solid coal particles.
Thus, precipitated vitrinite rich material was then separated from solvent-water solution
through filtration. This step was carried out in a conical flask-funnel arrangement with
standard 500 BS mesh. The residue of this filtration was the vitrinite rich extracted material;
filtrate consists of water and the solvents. After drying and weighing, the vitrinite rich
materials were subjected to chemical and petro graphical analysis.
‘Maceral composition of coal’ and ‘textural changes in the solvent treated coals’ has been
done through Oil immersion Microscopic analysis. ‘Determination of Maceral composition of
coal’ has been done as per standard (ASTM D2799-05a) and Textural analysis of solvent
extracted coals has been done through image analysis using Leica Qwin software. Coal
moulds were prepared from –1mm size of representative coal samples using cold setting

compound. These moulds were ground with silicon carbide paper of different size and
polished well with Levigated Polishing Alumina in water suspension form (Grade III,
average micron size 0.024) to prepare pellets for petrographic studies as per ASTM
D2797/2797M 11a. Pellets were studied under 50X oil immersion lens and 10X objective
lens using Leica DM6000M, an advanced reflected light microscope. Point counting method
(500 counts per mould) was used to quantify different maceral groups in coal. Macerals, the
organic building blocks of coal, are broadly classified as Vitrinite, Liptinite and Inertinite
Group of macerals, identified on the basis of their reflectance and morphological features.
Alteration in coal after treatment with organic solvent has been studies through image
analysis.
Maceral distributions of raw coal, 1.5 float, it’s extracted and reject sample are presented in
Table 1. Vitrinite was extracted from the 1.5 float. Vitrinite content was 45.6% and 98.4% for
1.5 float and1.5 extract respectively. Interinite content was 47.9% and 0.8% for 1.5 float
and1.5 extract respectively. This shows the extraction of vitrinite by solvent extraction
method.

The petrography images of raw coal, 1.5 float, 1.5 extract and its reject are presented in Fig 1,
2, 3 and 4. Raw coal image (Fig. 1) shows abundance of disseminated minerals into macerals.
Fig. 3, float of 1.5 is having vitrinite and inertinite in almost similar proportion. Fig.
4,suggests vitrinite maceral is acted upon by the solvent selectively and extracted from the
whole coal. In the residue large grains of inertinite were observed (Fig. 5). This means,
vitrinite and inertinite can be separated simultaneously by combination of sink-float and
solvent extraction method.

The extracted vitrinte sample was tested further for Free Swelling Index (FSI) test. Higher
value of FSI is an indicator of better coking properties. The coal is heated and shape of the
coke button produced is compare against a standard set of profiles. Here, results of three
samples are presented. Raw coal (ROM) FSI was 2.5. FSI of 1.5 float sample was 5 and 1.5
extracted sample was 7. This shows that extracted vitrinite sample is having good coking
property, which can be used in coal blend for coke making. The other application of extracted
vitrinite could be in synthesis of good quality carbon nanotubes (CNT) as reported by Moothi
et al.

We Claim:
1. A process for producing vitrinite rich coal, the process comprising of:
grinding coal to a pre-determined size;
separating coal and mineral matter by sink-float method using pre-determined high
gravity liquid chemicals;
extracting vitrinite from each float as extracted part by solvent extraction method; and
dewatering the extracted vitrinite.
2. The process as claimed in claim 1, wherein the pre-determined size is less than 500
micron being achieved through dry grinding process.
3. The process as claimed in claim 1, wherein sink-float method to separates the coal as
a float and mineral rich particles as sink.
4. The process as claimed in claim 1, wherein the solvent used inthe extracting step
comprises Ethylenediamine (EDA) and N-Methyl-2-Pyrrolidone (NMP).
5. The process as claimed in claim 1, wherein vitrinite and inertinite are separated out
simultaneously.
6. The process as claimed in claim 1, whereinvitrinite rich material is suitable for coke
making and carbon nanotubes.
7. The process as claimed in claim 1, wherein extract after the solvent extraction has at
least 95% fraction of vitrinite.