FIELD OF INVeNTION
The present invention relates to an economic process to produce low ash clean
coal from high ash coals adaptable to metallurgical applications.
BACKGRQUND OF THE INVENTION
The current process operation involves chemical beneficiation of coal by
dissolving organic matter of coal in various organic solvents. As coal is
heterogeneous mixture of organic and inorganic constituents, solvolysis of coal
varies with its constituents, maturity and structural characteristics. Main
advantage of this process are i) ease of recovery of solvent in the main process
stream, ii) solvolytic efficiency of recovered solvents as that of fresh solvent, III)
95-98% recovery of the solvent, iV) improved coking properties of clean coal,
and v) availability of industrial organic solvents. However, the operating cost of
this process is high because of high cost of solvents and energy requirement in
the process. Now an attempt has been tried to develop a new process called
techno-economic process by reducing the cost of solvent recovery.
Organo-refining or, solvent-refining, or, solvent extractin of coal is a well-
established technology. Abundant literature is available on the subject. However,
the primary objective in most of those cases is to provide a process to produce
ultra clean coal or super clean coal with ash contains less than 4%. The ash
content of this parent coal (Run of Mine) is 25%. Exploratory study revealed that
it is possible to extract 50% of parent coal through this process of extraction of
coal under reflux conditions at atmospheric pressure. The coal contains almost
4% ash.

The yield and the ash content of super clean coal are satisfactory and it
encourages us for up scaling the process to bench scale set up. In bench scale
set up the main concerning factor apart from yield is the economic viability of the
process. The process consumes significant amount of heat for extraction. Again
recovery of the solvent has been achieved by the consumption of large amount
of heat. Combination of the above two heat inputs drives the process towards
infeasibility. Now if the two heat consumptions are arranged in priority basis then
heat consumption for extraction has come forth as the extraction process is
solely depends upon the extraction temperature, this is why it is often called as
thermal extraction. So only the heat requirement for solvent recovery has left for
minimization. Effective or optimize design of solvent recovery helps us to
established the process feasibility. In present invention approach a process has
been developed in such a way that minimizes the heat requirement for solvent
recovery and thus establishes the process economy.
QBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an economic process to
produce low ash clean coal which eliminates the disadvantages of prior art.
Another object of the present invention is to propose an economic process to
produce low ash clean which maintains the process with low cost.
A further object of the present invention is to propose an economic process to
produce low ash clean which is very flexible to produce clean coal of desire ash
level (0.1 to 10%).

A still further object of the present invention is to propose an economic process
to produce low ash clean which is less fire hazardous as there is provision for
Nitrogen flashing in the reactor.
An yet further object of the present invention is to propose an economic process
to produce low ash clean which consumes less energy.
5UMMARY OF THE INVENTION
According to the innovative process, coal, solvent and co-solvent are mixed
thoroughly to produce coal slurry. The coal slurry is extracted with a
predetermined ratio of coal-solvent mixture. In extraction unit a sufficient high
temperature is maintained to facilitate the extraction at high temperature. A high
pressure is required to elevate the boiling point of the liqUid. The temperature
and pressure range of variation is around (200°C to 300°C) and (1.5 atm. to 5
atm.). Due to thermal impact coal structure relaxed and extraction process is
enhanced. Now keeping the pressure and temperature inside the reactor
constant a sufficient time is given to settle down the heavy mineral matter. After
settling of mineral matter 80% of coal extract is taking out from the top keeping
the constant pressure and temperature. Coal extract is then released in a flasher
unit at atmospheric pressure. Due to the pressure drop 30% of the solvent will
flash out leaving a 70% of liqUid at the bottom of flash chamber, which is then
sent to the evaporator. In evaporator a further recovery of solvent is done and
the concentrate heavy material is then discharged into the precipitation tank.
The combination of evaporator and flash unit gives almost 90% of solvent
recovery. The rest of the solvent, which is still 7-8% in amount, can be
recovered from distillation unit. This new process approach gives the desired
yield with minimum energy consumption.

BRIEF PESCRIPTION OE TUE ACCOMPANYING DRAWING
Fig A- shows the block diagram of the process
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THe
INVENTION
Coall solvent like N-methyl pyrollidone and co-solvent like Ethyl diamine are
mIxed thoroughly in coal in feed preparation zone (1). Coal slurry is then
pumped to the reactor (2). In reactor a temperature around 200°C to 300°C is
maintained by circulating hot thermic fluid. The high pressure is maintained by
inducing high pressure about 3 to 4 atm. inside the reactor. High pressure
elevates the boiling point of the solvent. Residence time in the reactor may vary
from 1hr to 1.5 hrs and i.e. dictated by the techno economics of the process and
its specific requirement. Extracted coal-solvent mixture is then settled in the
reactor. In settler after some specified time all mineral matters are settled. Coal
extract are being collected from the top of the settler and send to the flasher
unit (3). In flasher due to the sudden pressure drop 30% of the solvent will be
boiled off as the temperature of the solvent is much more than the atmospheric
boiling point of the solvent. 30% of the solvent are recovered without
introducing any external heat source. Actually high pressure and temperature are
employed in the reactor for flashing. The heavy material with some coal extracts
is then fed to the evaporator. Bottom part of the flasher also contains some
amount of coal extract which is again discharged into the evaporator (4). The
residue (5) is taken off and stored for later use. The filtrate contains little but
coal extracts which is fed to the evaporator (4). In evaporator (4) the "coal
extract' is concentrated by boiling of most of the solvent. With the help of
evaporation a further 60% of solvent recovery is possible. This way almost 90%

of the solvent is recovery is possible by the combination of flasher (3) and
evaporation unit (4). In precipitating tank (6) coal is getting precipitated as water
acts as an anti-solvent. This slurry becomes filtered by another rotary drum filter
and the super clean coal is collected as residue. The filtrate contains water and
organic mixture which is fed to the distillation unit (7) and water and organic is
being separated. In distillation (7) the remaining 7 to 8% of solvent is recovered.
The proposed process helps to recover 98% of the solvent by combination of
flash unit (3), evaporation unit (4) and distillation unit (7) with minimum energy
consumption, produce clean coal of desire ash level (0.1 to 10%) with
satisfactory yield (9).

WE CLAIM
1. A developed techno-economic process for organo-refining of coal to
produce low ash clean coal comprises:
- mixing of coal, solvent N-methyl pyrollidone and co-solvent Ethyl diamine
thoroughly to produce coal slurry in feed preparation zone (1);
- feeding the slurry to a reactor (2) by pumping;
- the reactor (2) maintaining a temperature 200°C to 300°C and a pressure
of 1.5 atm. to 5 atm.;
- extracting coal-solvent mixture being settled in the reactor;
- extracting coal from the top of the reactor and fed to the flasher unit (3);
- extracting 30% of the solvent from the flashing unit (3);
- the heavy material with some coal extracts are fed to a evaporator (4);
- extracting 60% of solvent from the evaporator (4);
- filtering the slurry in a rotary drum;
- collecting the super clean coal as residue containing 0.1 to 10% ash;
- filterate contains water and organic mixture which is fed to the distillation
unit (7);
- separation of water and organic in distillation unit (7) and 7 to 8% of
solvent are recovered;

2. The process as claimed in claim 1, wherein coal slurry mixture is kept in
the reactor for 1hr to 1.5 hrs.
3. The process as claimed in claim 1, wherein coal slurry mixture contains
coal:solvent:co-solvent in the proportion of 1 : 17: 1.

4. The process as claimed in claim 1, wherein organic chemical N-methyl
pyrollidone and Ethyl diamine are used as solvent for extraction.