NZ623472B2 - A process for pre-treatment of high ash coal to produce clean coal - Google Patents
A process for pre-treatment of high ash coal to produce clean coal Download PDFInfo
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- NZ623472B2 NZ623472B2 NZ623472A NZ62347212A NZ623472B2 NZ 623472 B2 NZ623472 B2 NZ 623472B2 NZ 623472 A NZ623472 A NZ 623472A NZ 62347212 A NZ62347212 A NZ 62347212A NZ 623472 B2 NZ623472 B2 NZ 623472B2
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- coal
- solvent
- concentrated extract
- solution
- water
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 207
- 239000003245 coal Substances 0.000 title claims abstract description 203
- 238000000034 method Methods 0.000 title claims abstract description 65
- 238000004140 cleaning Methods 0.000 title claims description 44
- 238000002203 pretreatment Methods 0.000 title description 6
- 239000000284 extract Substances 0.000 claims abstract description 102
- 239000002904 solvent Substances 0.000 claims abstract description 71
- SECXISVLQFMRJM-UHFFFAOYSA-N n-methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims abstract description 52
- 239000002002 slurry Substances 0.000 claims abstract description 44
- PIICEJLVQHRZGT-UHFFFAOYSA-N 1,2-ethanediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 claims abstract description 39
- HZAXFHJVJLSVMW-UHFFFAOYSA-N ethanolamine Chemical compound NCCO HZAXFHJVJLSVMW-UHFFFAOYSA-N 0.000 claims abstract description 38
- 238000001914 filtration Methods 0.000 claims abstract description 28
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 19
- 238000004821 distillation Methods 0.000 claims abstract description 16
- 239000012296 anti-solvent Substances 0.000 claims abstract description 12
- 239000004744 fabric Substances 0.000 claims abstract description 11
- 238000001704 evaporation Methods 0.000 claims abstract description 10
- 230000001376 precipitating Effects 0.000 claims abstract description 10
- 238000000605 extraction Methods 0.000 claims description 15
- 238000002525 ultrasonication Methods 0.000 claims description 13
- 238000011084 recovery Methods 0.000 claims description 9
- 238000004939 coking Methods 0.000 claims description 2
- 239000002245 particle Substances 0.000 claims description 2
- 239000002041 carbon nanotube Substances 0.000 claims 1
- 229910021393 carbon nanotube Inorganic materials 0.000 claims 1
- 229910052799 carbon Inorganic materials 0.000 abstract description 6
- 239000002956 ash Substances 0.000 description 47
- 238000000638 solvent extraction Methods 0.000 description 19
- 239000006184 cosolvent Substances 0.000 description 16
- 239000010883 coal ash Substances 0.000 description 10
- 239000000463 material Substances 0.000 description 10
- 239000000126 substance Substances 0.000 description 8
- 229910052500 inorganic mineral Inorganic materials 0.000 description 6
- 238000010992 reflux Methods 0.000 description 6
- 238000000926 separation method Methods 0.000 description 6
- 239000011877 solvent mixture Substances 0.000 description 6
- 239000011707 mineral Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 239000011148 porous material Substances 0.000 description 5
- 239000005416 organic matter Substances 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 239000003250 coal slurry Substances 0.000 description 3
- 238000007670 refining Methods 0.000 description 3
- QGJOPFRUJISHPQ-UHFFFAOYSA-N carbon bisulphide Chemical compound S=C=S QGJOPFRUJISHPQ-UHFFFAOYSA-N 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 239000000706 filtrate Substances 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 238000011021 bench scale process Methods 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 230000005587 bubbling Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 231100000078 corrosive Toxicity 0.000 description 1
- 231100001010 corrosive Toxicity 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 150000002222 fluorine compounds Chemical class 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000008241 heterogeneous mixture Substances 0.000 description 1
- 238000002386 leaching Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 239000002516 radical scavenger Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 238000003797 solvolysis reaction Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000009210 therapy by ultrasound Methods 0.000 description 1
- -1 where Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
- B01J19/10—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing sonic or ultrasonic vibrations
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
- B01J19/12—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electromagnetic waves
- B01J19/122—Incoherent waves
- B01J19/126—Microwaves
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
- B01J2219/0873—Materials to be treated
- B01J2219/0879—Solid
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
- B01J2219/12—Processes employing electromagnetic waves
- B01J2219/1203—Incoherent waves
- B01J2219/1206—Microwaves
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L5/00—Solid fuels
- C10L5/02—Solid fuels such as briquettes consisting mainly of carbonaceous materials of mineral or non-mineral origin
- C10L5/26—After-treatment of the shaped fuels, e.g. briquettes
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L9/00—Treating solid fuels to improve their combustion
- C10L9/02—Treating solid fuels to improve their combustion by chemical means
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L9/00—Treating solid fuels to improve their combustion
- C10L9/08—Treating solid fuels to improve their combustion by heat treatments, e.g. calcining
Abstract
process for treating coal to obtain lower ash content coal comprises (i) pretreating high ash coal in a pretreatment unit with ultrasonic waves or with microwaves, (ii) forming a slurry of coal fines comprising pretreated coal in a solvent solution comprising N-Methyl-2-pyrrolidone (NMP) and one of Ethylenediamine (EDA) or Monoethanolamine (MEA) with a NMP to EDA or a NMP to MEA ratio is 1:1 to 20:1, the slurry containing about 10 to 25 ml of solution per g of coal, (iii) maintaining the slurry in a refluxed condition at a temperature of about 170-190°C or at room temperature for a period of about 15 minutes to 2 hours, (iv) separating the refluxed slurry in two parts consisting of extract and residue by coarse filtration with a 0.025 mm filter cloth, (v) recovering up to 85% of the solvent solution by evaporation of the extract to form a concentrated extract, (vi) precipitating the coal by adding an anti-solvent or water to the concentrated extract to form an anti-solvent-concentrated extract solution or a water-concentrated extract solution, (vii) separating the coal from the anti-solvent-concentrated extract solution or the water-concentrated extract solution by filtration, the coal having a reduced ash content and (viii) recovering the rest of the solvent by distillation of the anti-solvent-concentrated extract solution or the water-concentrated extract solution. A process for treating coal to obtain lower ash content coal comprises (i)) forming a slurry of coal fines comprising pretreated coal in a solvent solution comprising N-Methyl-2-pyrrolidone (NMP) and one of Ethylenediamine (EDA) or Monoethanolamine (MEA) with a NMP to EDA or a NMP to MEA ratio is 1:1 to 20:1, the slurry containing about 10 to 25 ml of solution per g of coal, (ii) maintaining the slurry in a refluxed condition at a temperature of about 170-190°C for a period of about 15 minutes to 2 hours, (iii) separating the refluxed slurry in two parts consisting of extract and residue by coarse filtration with a 0.025 mm filter cloth, (iv) recovering up to 85% of the solvent solution by evaporation of the extract to form a concentrated extract, (v) precipitating the coal by adding an anti-solvent or water to the concentrated extract to form an anti-solvent-concentrated extract solution or a water-concentrated extract solution, (vi) separating the coal from the anti-solvent-concentrated extract solution or the water-concentrated extract solution by filtration, the coal having a reduced ash content and (vii) recovering the rest of the solvent by distillation of the anti-solvent-concentrated extract solution or the water-concentrated extract solution. f Ethylenediamine (EDA) or Monoethanolamine (MEA) with a NMP to EDA or a NMP to MEA ratio is 1:1 to 20:1, the slurry containing about 10 to 25 ml of solution per g of coal, (iii) maintaining the slurry in a refluxed condition at a temperature of about 170-190°C or at room temperature for a period of about 15 minutes to 2 hours, (iv) separating the refluxed slurry in two parts consisting of extract and residue by coarse filtration with a 0.025 mm filter cloth, (v) recovering up to 85% of the solvent solution by evaporation of the extract to form a concentrated extract, (vi) precipitating the coal by adding an anti-solvent or water to the concentrated extract to form an anti-solvent-concentrated extract solution or a water-concentrated extract solution, (vii) separating the coal from the anti-solvent-concentrated extract solution or the water-concentrated extract solution by filtration, the coal having a reduced ash content and (viii) recovering the rest of the solvent by distillation of the anti-solvent-concentrated extract solution or the water-concentrated extract solution. A process for treating coal to obtain lower ash content coal comprises (i)) forming a slurry of coal fines comprising pretreated coal in a solvent solution comprising N-Methyl-2-pyrrolidone (NMP) and one of Ethylenediamine (EDA) or Monoethanolamine (MEA) with a NMP to EDA or a NMP to MEA ratio is 1:1 to 20:1, the slurry containing about 10 to 25 ml of solution per g of coal, (ii) maintaining the slurry in a refluxed condition at a temperature of about 170-190°C for a period of about 15 minutes to 2 hours, (iii) separating the refluxed slurry in two parts consisting of extract and residue by coarse filtration with a 0.025 mm filter cloth, (iv) recovering up to 85% of the solvent solution by evaporation of the extract to form a concentrated extract, (v) precipitating the coal by adding an anti-solvent or water to the concentrated extract to form an anti-solvent-concentrated extract solution or a water-concentrated extract solution, (vi) separating the coal from the anti-solvent-concentrated extract solution or the water-concentrated extract solution by filtration, the coal having a reduced ash content and (vii) recovering the rest of the solvent by distillation of the anti-solvent-concentrated extract solution or the water-concentrated extract solution.
Description
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TITLE: A PROCESS FOR PRE-TREATMENT OF HIGH ASH COAL TO PRODUCE
CLEAN COAL
FIELD OF THE INVENTION
The present invention relates to a process to produce low ash clean coal from high ash coal for
various metallurgical applications by pretreatment of high ash coal with microwave and ultra
sonic treatment followed by solvent extraction.
BACKGROUND OF THE INVENTION
The concept and practice of chemical beneficiation process comes from the limitation of
physical beneficiation processes. Broadly, a chemical beneficiation process is possible by
chemical leaching of mineral matter present in coal or, 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 composition, maturity, and structural
characteristics. Since the mineral matter (non-combustible) available in specific
geographical locations is very finely disseminated in the organic mass, it is really very
difficult to remove the non-combustible mineral matter by conventional physical coal
washing techniques. Presence of high percentage of near gravity material in such type of
coal makes the scope of implementing a gravity separation process limited. This indicates
that chemical treatment may be the right approach to overcome the limitation of physical
beneficiation methods. A plurality of technical literature is available on chemical
beneficiation techniques that employ highly corrosive chemicals (mostly acids and
alkalis). Recovery or regeneration of these chemicals is very important to make this
technology viable. A parallel approach towards lowering ash could be through recovering
the premium organic matter from coal by solvent refining. Literature reveals that most of
the research work on this subject was carried out with an objective to produce ultra clean
coal or super clear coal with ash content less than 0.2% for high-tech end uses. This
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conventional solvent refining process does not serve the objective of low ash coal
requirement of steel industries mainly, because of low recovery which makes the process
uneconomic especially when such an ultraclean coal is not absolutely desired, and the
cost of the process is too high as entailed by low yields.
The main advantages of the prior art process are i) ease of recovery of solvent in the main
process steam, 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.
According to the existing process, coal, solvent (N-MethylPyrrolidone, NMP) and co-
solvent (Ethylenediamine, EDA or Monoethanolamine, MEA) are mixed thoroughly to
produce coal slurry. The coal slurry is extracted in a known manner which includes coal-
solvent mixture. The mixture is separated in a separation unit to produce a coarser
fraction and a finer fraction. The finer fraction is fed to an evaporator unit to allow 70 to
80% of solvent recovery. The hot concentrated coal-solvent mixture is then flushed in a
precipitation tank to precipitate the coal, where, water as an anti-solvent is being used.
Water separates the solvent from coal and we get water solvent mixture, which is fed to
distillation unit to separate solvent and anti-solvent. And precipitated coal is separated in
a filtration unit.
In the existing processes pretreatment of coal is not being done. It is a solvent extraction
of coal process without any pretreatment of coal. So there is a scope of pretreatment of
coal by microwave and ultrasonication, (1) to open up the pores of coal samples,
facilitation and (2) disrupt the coal (organic matter) and mineral matter
physical (or chemical) association, for enhancement of clean coal
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extraction. Our aim is to have comparative study of solvent extraction with pretreatment
followed by solvent extraction. Also, to study room temperature dissolution as another
attempt to reduce the heat consumption.
JP2001026791 discloses a method for producing an ash-less coal is to bring a raw
material coal in contact with N-methylpyrrolidinone solvent or a mixed solvent of
carbon disulfide with N-methylpyrrolidinone in the presence of a chlorine or fluorine
compound for extracting the ash-less coal.
JP2010023018 describes a pretreatment method and device. Accordingly, scavenger, a
bubbling agent, and air are fed into the slurried coal ash composed of the unburned
carbon-containing coal ash and water so as to produce bubbles, and the unburned carbon
is caught in the bubbles. Before·the slurried coal ash is fed to a floatation apparatus for
separating tail ash having a low unburned carbon content, ultrasonic waves are emitted thereto
by an ultrasonic wave generating apparatus so that the separation efficiency of
the unburned carbon from the coal ash is increased.
WO2010029563 teaches an improved organo-refining process to produce low ash clean
coal from high ash coal, the method comprising the steps of: mixing of coal, solvent and
a co-solvent; feeding the slurry to a reactor by pumping; the reactor maintaining a
temperature about 200 deg. C to 300 deg. C and a pressure of 1.5 atm.; extracting coal-
solvent mixture; feeding the extracted coal to a flasher unit; recovering about 30% of the
solvent from the flashing unit; feeding the remaining heavy material with some coal
extracts to an evaporator; extracting about 60% of solvent from the evaporator;
discharging the residue from the evaporator to a precipitator; filtering the slurry in a rotary
drum; collecting the super clean coal as residue containing 0.1 to 10% ash; feeding the
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filtrate into a distillation unit; separating water and organic material in order to recover at
least 7 to 8% of the remaining solvent.
US2005236403 discloses pre-treatment of multi-phase materials. The material having a
first phase of material and a second phase of material. The method comprises heating the
material electromagnetically, preferably with microwaves, to produce a power density of
at least 10<9>Wm<-3> in a continuous process in which the material moves into and
through an electromagnetic, preferably microwave, treatment area. The material
experiences exposure to microwaves, in the treatment area for a time of the order of 1/2
second or less before the material is passed out of the treatment area for subsequent
operation.
However, the present inventors in course of developing the disclosed invention have
identified that recovery of clean coal and its ash content depend on various operating
parameters and feed characteristics for example, faster and convenient filtration of
refluxed solution at different size, selection of solvent and co-solvent, coal and source
(feed characteristics), particle size, coal-solvent ratio, extraction time, and extraction
temperature.
By way of reference, prior Indian patent application numbers 1336/KOL/2008,
1088/KOL/07 and 1292/KOL/06 are incorporated herein.
Throughout this specification and the claims which follow, unless the context requires
otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be
understood to imply the inclusion of a stated integer or step or group of integers or steps but
not the exclusion of any other integer or step or group of integers or steps.
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The reference in this specification to any prior publication (or information derived from it), or
to any matter which is known, is not, and should not be taken as an acknowledgment or
admission or any form of suggestion that prior publication (or information derived from it) or
known matter forms part of the common general knowledge in the field of endeavour to which
this specification relates.
ASPECTS OF THE INVENTION
It is therefore one aspect of this invention to propose a process to produce low ash clean
coal from high ash coal.
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Another aspect of the invention is to propose a process to produce low ash clean coal
from high ash coal, in which coal is being treated by solvent extraction method.
Another aspect of the invention is to propose a process to produce low ash clean coal
from high ash coal, in which coal is being treated with microwave before solvent
extraction process.
A still another aspect of the invention is to propose a process to produce low ash clean
coal from high ash coal, which exhibits high recovery of solvent.
Yet another aspect of the invention is to propose a process to produce low ash clean coal from
high ash coal, in which coal is being treated with ultra sonic waves before solvent
extraction process.
A further aspect of the invention is to propose a process to produce low ash clean coal
from high ash coal, in which coal pores are being opened before solvent extraction process.
A further aspect of the invention is to propose a process to produce low ash clean coal
from high ash coal, in which solvent and co-solvent are being used for extraction process.
A further aspect of the is to propose a process to produce low ash clean coal from high
ash coal, which reduces consumption of heat energy by using co-solvent which allows
reflux of coal-solvent-co-solvent mixture at lower temperatures than those required when
solvent is used alone.
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A further aspect of the invention is to propose a process to produce low ash clean coal
from high ash coal, which reduces consumption of heat energy by allowing dissolution at
room temperature.
SUMMARY OF THE INVENTION
In one aspect of the present invention provides a process for treating coal to obtain lower ash
content coal comprising (i) pretreating high ash coal in a pretreatment unit with ultrasonic
waves or with microwaves, (ii) forming a slurry of coal fines comprising pretreated coal in a
solvent solution comprising N-Methylpyrrolidone (NMP) and one of Ethylenediamine
(EDA) or Monoethanolamine (MEA), wherein a NMP to EDA or a NMP to MEA ratio is 1:1
to 20:1, said slurry containing about 10 to 25 ml of solution per g of coal, (iii) maintaining said
slurry in refluxed condition at a temperature of about 170-190°C for a period of about 15
minutes to 2 hours, (iv) separating the refluxed slurry in two parts consisting of extract and
residue by coarse filtration with a 0.025 mm filter cloth, (v) recovering up to 85% of the
solvent solution by evaporation of the extract to form a concentrated extract, (vi) precipitating
the coal by adding an anti-solvent or water to the concentrated extract to form an anti-solvent-
concentrated extract solution or a water-concentrated extract solution, (vii) separating the coal
from the anti-solvent-concentrated extract solution or the water-concentrated extract solution
by filtration, said coal having a reduced ash content and (viii) recovering the rest of the solvent
by distillation of the anti-solvent-concentrated extract solution or the water-concentrated
extract solution.
Another aspect of the present invention provides a process for treating coal to obtain lower ash
content coal comprising (i) forming a slurry of coal fines in a solvent solution comprising N-
Methylpyrrolidone (NMP) and one of Ethylenediamine (EDA) or Monoethanolamine
(MEA), wherein a NMP to EDA or a NMP to MEA ratio is 1:1 to 20:1, said slurry containing
about 10 to 25 ml of solution per g of coal, (ii) maintaining said slurry in a refluxed condition
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at a temperature of about 170-190°C for a period of about 15 minutes to 2 hours, (iii)
separating the refluxed slurry in two parts consisting of extract and residue by coarse filtration
with a 0.025 mm filter cloth, (iv) recovering up to 85% of the solvent solution by evaporation
of the extract to form a concentrated extract, (v) precipitating the coal by adding an anti-
solvent or water to the concentrated extract to form an anti-solventconcentrated extract
solution or a water-concentrated extract solution, (vi) separating the coal from the anti-solvent-
concentrated extract solution or the water-concentrated extract solution by filtration, said coal
having a reduced ash content and (vii) recovering the rest of the solvent by distillation of the
anti-solvent-concentrated extract solution or the water-concentrated extract solution.
Another aspect of the present invention provides a process for treating coal to obtain lower ash
content coal comprising (i) pretreating high ash coal in a pretreatment unit with ultrasonic
waves or with microwaves, (ii) forming a slurry of coal fines in a solvent solution comprising
N-Methylpyrrolidone (NMP) and one of Ethylenediamine (EDA) or Monoethanolamine
(MEA), wherein a NMP to EDA or a NMP to MEA ratio is 1:1 to 20:1, said slurry containing
about 10 to 25 ml of solution per g of coal, (iii) maintaining said slurry in a refluxed condition
at room temperature for a period of about 15 minutes to 2 hours, (iv) separating the refluxed
slurry in two parts consisting of extract and residue by coarse filtration with a 0.025 mm filter
cloth, (v) recovering up to 85% of the solvent solution by evaporation of the extract to form a
concentrated extract, (vi) precipitating the coal by adding an anti-solvent or water to the
concentrated extract to form an anti-solvent-concentrated extract solution or a water-
concentrated extract solution, (vii) separating the coal from the anti-solventconcentrated
extract solution or the water-concentrated extract solution by filtration, said coal having a
reduced ash content and (viii) recovering the rest of the solvent by distillation of the
antisolvent-concentrated extract solution or the water-concentrated extract solution.
According to one embodiment of the inventive process; coal, solvent and co-solvent are
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provided in a pre defined ratio. Coal to solvent ratio is varied from 1:6 to 1:20 (wt/vol, g/ml),
coal to solvent are wt/vol and solvent to co-solvent ratios are vol/vol wherever mentioned).
Coal to co-solvent ratio is varied from 1:1 to 1:5 (g/ml), while co-solvent to solvent ratio is
varied from 1:1 to 1:20. The boiling point of EDA, MEA, NMP and water is 117°C, 170°C,
202°C and 100°C respectively. According to one embodiment of the innovative process, coal
is pretreated in ultrasonication equipment for 2 minutes to 10 minutes and then solvent
extraction at room temperature and at reflux condition is being done. In another embodiment
of the innovative process, coal is being pretreated in microwave oven for 30 seconds to 2
minutes and then solvent extraction at reflux condition is carried out. In other innovative
process, coal is treated with solvent (NMP) and co-solvent (EDA or MEA) for 15 minutes to 2
hours only by solvent extraction process no pretreatment is being done. In another
embodiment of the innovative process, coal is dissolute at room temperature with NMP and
EDA.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 Shows a process flow sheet for pre-treatment of high ash coal to produce
clean coal according to the invention.
MARKED-UP COPY
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, high ash coal is treated by solvent extraction process at reflux
conditions for 15 minutes to 2 hours to produce the clean coal. Frequently, solvent cannot
penetrate into the pores of coal. It is known the pores of the coal are opened with
pretreatment to increase the clean coal yield in solvent extraction process. So, the coal is
pretreated in ultrasonication equipment as well as in microwave oven to open up the
pores of the coal before solvent extraction process. Such pre-treatment tend to disrupt the
associative forces between the organic matter of coal and its inorganic mineral matter.
Coal sample along with solvent is treated in ultrasonication equipment for 2 to 10
minutes, while being treated for 30 seconds to 2 minutes in microwave oven. This slurry
(coal solvent slurry) is maintained for room temperature extraction or transfer to an
extraction apparatus, where extraction takes place for 15 minutes to 2 hours. Then the
refluxed mixture is filtered using 500 stainless steel BSS mesh (0.025 mm) cloth. These
steps allow coarser and faster filtration at 0.025 mm size in comparison to that obtained
by using the known Whatman filter paper. Therefore, an increase in yield of clean coal
and simultaneously increase in ash content of the clean coal, can be clearly achieved.
Accordingly, the inventive process is found to be advantageous to produce high yield
clean coal with low ash content (5-10%) through a faster filtration process.
Feed coal ash was in the range of 25-35%. The ratio of NMP and MEA, NMP and EDA
may vary from 1:1 to 20:1 and the coal (g) to solvents (ml) ratio may vary from 1:06 to
1:20. Comparison of the extraction yields when coal to co-solvent ratio is 1:1 obtained
without ultrasonication (45%) with that obtained by ultrasonication
followed by solvent extraction (47%), showed an improvement in the yield.
Clean coal ash was in the range of 8-10%. In case of co-solvent to
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solvent ratio 1:1, extraction yield obtained without ultrasonication (35%) while
ultrasonication followed by solvent extraction (37%). Clean coal ash was in the range of
-12%. Again, it showed improved results with ultrasonication. Extraction yield is about
45% without microwave treatment, while it is about 47% with microwave followed by
solvent extraction. The clean coal ash is in the range of 8-10%. Feed coal sample having
ash around 13%, extraction yield was about 66% without microwave treatment, while it
was about 68% when pretreated in microwave oven followed by solvent extraction.
Pretreatment of coal with ultrasonication or with microwave helps in clean coal yield
improvement. This invention thus enables producing low ash (<12%) clean coal for coke
making purpose with very high yield through a relatively faster filtration. The extraction
yields on dry mineral matter basis will be still higher.
Results obtained without pretreatment of coal is as follows. Feed coal ash was in the
range of 25-35%. The ratio of NMP and MEA, NMP and EDA may vary from 1:1 to 20:1
and the coal (g) to solvents (ml) ratio may vary from 1:06 to 1:20. When coal was treated
with NMP and EDA, clean coal yield was about 45% having 8% ash. When coal was
treated with NMP and MEA, clean coal yield was in the range of 45-50% and clean coal
ash was in the range of 5-8%. Both co-solvents give us similar results. This shows that
we can use EDA as well as MEA as a co-solvent in the solvent extraction of coal process.
A process has been developed for bench scale operation which is shown in figure 1. The
process consists of seven units namely, (i) an ultrasonication or microwave oven (1), (ii)
an Extractor (2), (iii) a first filteration (3) separation size 500 mesh), (iv) an Evaproator
column (4), (v) a Precipitation tank (5), (vi) a second filteration (6) (for complete solid-
liquid separation) and (vii) a Distillation column (7).
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Coal is pretreated in ultrasonication or microwave units before extraction. Residence time
in these units may vary from 30 seconds to 10 minutes. Coal, solvent and co-solvent are
mixed thoroughly in coal-solvent feed tank. If pretreatment is not being done then coal
solvent slurry would be fed direct from feed tank to reactor/extractor. Coal slurry is then
pumped into the extractor (2). A temperature around 170-190°C is achieved in the
extractor (1) slowly. This is about 12-32°C lower than that of the reflux temperature for
the NMP when used without co-solvent. Therefore, the use of co-solvents affords the
conservation of energy and thus saving in heat energy required during refluxing.
Residence time in the extractor (2) may vary from 15 minutes to 2h and i.e. dictated by
the techno economics of the process and its specific requirement. Extracted coal-solvent
mixture is then separated through a first filter (3) or any separation unit which may cut
the mixture in two fractions: coarser fraction (+0.025 mm) and finer fraction (-0.025
mm). Coarser fraction contains high ash and is called as residue. The finer fraction or
filtered extract is then fed to an evaporator unit (4). Maximum 80-85% solvent recovery
may be allowed through evaporator unit (4). The concentrated coal-solvent mixture is
flushed in a precipitation tank (5). As NMP-EDA or NMP-MEA solvents are soluble in
water, extracted coal gets separated from the solution phase and gets precipitated. This
precipitated coal is separated through a second filter (6). Thus obtained clean coal
contains less than 8% ash. The filtrate consists of solvent-water solution and solvent is
recovered through a second distillation unit (7). The secondary product of the distillation
unit (7) is hot water, which may be used as a washing media in a precipitation tank (5). It
is possible to recover around 98-99% of solvent through the evaporator, and distillation
units (4,7).
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THE
Claims (15)
1. A process for treating coal to obtain lower ash content coal comprising (i) pretreating high ash coal in a pretreatment unit with ultrasonic waves or with microwaves, (ii) forming a slurry of coal fines comprising pretreated coal in a solvent solution comprising N-Methylpyrrolidone (NMP) and one of Ethylenediamine (EDA) or Monoethanolamine (MEA), wherein a NMP to EDA or a NMP to MEA ratio is 1:1 to 20:1, said slurry containing about 10 to 25 ml of solution per g of coal, (iii) maintaining said slurry in a refluxed condition at a temperature of about 170-190°C for a period of about 15 minutes to 2 hours, (iv) separating the refluxed slurry in two parts consisting of extract and residue by coarse filtration with a 0.025 mm filter cloth, (v) recovering up to 85% of the solvent solution by evaporation of the extract to form a concentrated extract, (vi) precipitating the coal by adding an anti-solvent or water to the concentrated extract to form an anti-solvent-concentrated extract solution or a water-concentrated extract solution, (vii) separating the coal from the anti-solvent- concentrated extract solution or the water-concentrated extract solution by filtration, said coal having a reduced ash content and (viii) recovering the rest of the solvent by distillation of the anti-solvent-concentrated extract solution or the water-concentrated extract solution.
2. The process as claimed in claim 1, wherein said high ash coal comprises run of mine coal.
3. The process as claimed in claim 1, wherein said high ash coal comprises medium coking coal.
4. The process as claimed in claim 1, wherein said high ash coal comprises clean coal MARKED-UP COPY having ash content of <12% after physical beneficiation.
5. The process as claimed in any one of claims 1 to 4, wherein the coal having a reduced ash content separated in step (vii) is ultra low ash clean coal or super clean coal having an ash content of <l% and is separated using fine filtration of the refluxed solution.
6. The process as claimed in claim 5, wherein said ultra low ash clean coal or super clean coal has an ash content of <0.2%.
7. The process as claimed in any one of claims 1 to 4, wherein the coal having a reduced ash content separated in step (vii) is moderate ash clean coal having an ash content of <12% and is separated using coarse filtration of the refluxed solution.
8. The process as claimed in claim 7, wherein said moderate ash clean coal has an ash content of <8%.
9. The process as claimed in any one of claims 1 to 8, wherein 99% recovery of the solvent is achieved.
10. The process as claimed in claim 1, wherein low ash clean coal having ash <8% is produced by pretreatment of coal with ultrasonication followed by extraction.
11. The process as claimed in claim 1, wherein low ash clean coal having ash <8% is produced by pretreatment of coal with microwave followed by extraction.
12. The process as claimed in claim 2, wherein said coal particle size is 0 to 0.25mm. MARKED-UP COPY
13. The process as claimed in claim 5 or claim 6, wherein said ultra low ash clean coal or super clean coal having ash content <0.2% may be used to produce carbon nanotubes.
14. A process for treating coal to obtain lower ash content coal comprising (i) forming a slurry of coal fines in a solvent solution comprising N-Methylpyrrolidone (NMP) and one of Ethylenediamine (EDA) or Monoethanolamine (MEA), wherein a NMP to EDA or a NMP to MEA ratio is 1:1 to 20:1, said slurry containing about 10 to 25 ml of solution per g of coal, (ii) maintaining said slurry in a refluxed condition at a temperature of about 170-190°C for a period of about 15 minutes to 2 hours, (iii) separating the refluxed slurry in two parts consisting of extract and residue by coarse filtration with a 0.025 mm filter cloth, (iv) recovering up to 85% of the solvent solution by evaporation of the extract to form a concentrated extract, (v) precipitating the coal by adding an anti-solvent or water to the concentrated extract to form an anti- solventconcentrated extract solution or a water-concentrated extract solution, (vi) separating the coal from the anti-solvent-concentrated extract solution or the water- concentrated extract solution by filtration, said coal having a reduced ash content and (vii) recovering the rest of the solvent by distillation of the anti-solvent-concentrated extract solution or the water-concentrated extract solution.
15. A process for treating coal to obtain lower ash content coal comprising (i) pretreating high ash coal in a pretreatment unit with ultrasonic waves or with microwaves, (ii) forming a slurry of coal fines in a solvent solution comprising N-Methylpyrrolidone (NMP) and one of Ethylenediamine (EDA) or Monoethanolamine (MEA), wherein a NMP to EDA or a NMP to MEA ratio is 1:1 to 20:1, said slurry containing about 10 to 25 ml of solution per g of coal, (iii) maintaining said slurry in a refluxed condition at room temperature for a period of about 15 minutes to 2 hours, (iv) separating the refluxed slurry in two parts consisting of extract and residue by coarse filtration with a MARKED-UP COPY 0.025 mm filter cloth, (v) recovering up to 85% of the solvent solution by evaporation of the extract to form a concentrated extract, (vi) precipitating the coal by adding an anti-solvent or water to the concentrated extract to form an anti-solvent-concentrated extract solution or a water-concentrated extract solution, (vii) separating the coal from the anti-solventconcentrated extract solution or the water-concentrated extract solution by filtration, said coal having a reduced ash content and (viii) recovering the rest of the solvent by distillation of the antisolvent-concentrated extract solution or the water-concentrated extract solution.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IN284/KOL/2012 | 2012-03-14 | ||
IN284KO2012 | 2012-03-14 | ||
PCT/IN2012/000577 WO2013136342A1 (en) | 2012-03-14 | 2012-09-04 | A process flow sheet for pre - treatment of high ash coal to produce clean coal |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ623472A NZ623472A (en) | 2016-09-30 |
NZ623472B2 true NZ623472B2 (en) | 2017-01-05 |
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