Note: Descriptions are shown in the official language in which they were submitted.
I
.
APPARATUS FOR THE BENEFIT RATION OF COAL
l This application is a divisional of Application Serial
No. 399,826, filed March 30, 1982.
This invention relates to the beneficiation of
coal and more particularly to an improved apparatus for the
5 beneficiation of coal and separation of impurities there-
from and the formation of stable beneficiated coal mixtures,
such as coal oil mixtures.
Known resources of coal and other solid carbon-
assess fuel materials in the world are far greater than
10 the known resources of petroleum and natural gas combined.
Despite this enormous abundance of coal and related solid
carbonaceous materials, reliance on these resources,
particularly coal, as primary sources of energy, has been
for the most part discouraged. The availability of cheaper,
cleaner burning, more easily retrievable and transportable
fuels, such as petroleum and natural gas, has in the past,
cast coal to a largely supporting role in the energy field.
Current world events, however, have forced a new
awareness of global energy requirements and of the avail-
ablate of those resources which will adequately meet thousands. The realization that reserves of petroleum and
natural gas are being rapidly depleted in conjunction with
skyrocketing petroleum and natural gas prices and the unrest
in the regions of the world which contain the largest
25quantities of these resources, has sparked a new interest in
the utilization of solid carbonaceous materials, particularly
coal, as primary energy sources.
As a result, enormous efforts are being extended
to make coal and related solid carbonaceous materials
equivalent or better sources of energy, than petroleum or
natural gas. In the case of coal, for example, much of
3 lo t
this effort is directed to overcoming the environmental
problems associated with its production, transportation
and combustion. For example, health and safety hazards
associated with coal mining have been significantly reduced
with the onset of new legislation governing coal mining.
Furthermore, numerous techniques have been explored and
developed to make coal cleaner burning, more suitable for
burning and more readily transportable.
Gasification and liquefaction of coal are two
swish known techniques. Detailed descriptions of various
coal gasifaction and liquefaction processes may be found,
for example, in the Encyclopedia of Chemical Technology,
Kirk-Othmer, Third Edition (1980) Volume 11, pages 410-422
and 449-473. Typically, these techniques, however, require
15high energy input, as well as the utilization of hush
temperature and high pressure equipment, thereby reducing
their widespread feasibility and value.
Processes to make coal more readily liquefiable
have also been developed. One such process is disclosed
inn US. Patent No. 4,033,852 (Horowitz, et at.). This
process involves chemically modifying a portion of the
surface of the coal in a solvent media, the effect of which
renders the coal more readily liquefiable in a solvent than
natural forms of coal, thereby permitting recovery Go
25~ liquefiable viscous product by extraction.
In addition to gasification and liquefaction,
other methods for converting coal to more convenient forms
for burning and transporting are also known. For example,
the preparation of coal-oil and coal-aqueous mixtures are
30 described in the literature. Such liquid coal mixtures
offer considerable advantages. In addition to being more
I
1 readily transportable than dry solid coal, they are more
easily storable, and less subject to the risks of explosion
by spontaneous ignition. Moreover, providing coal in a
fluid form makes it feasible for burning in conventional
5 apparatus used for burning fuel oil. Such a capability
can greatly facilitate the transition from fuel oil to
coal as a primary energy source. Typical coal-oil and coal-
aqueous mixtures and their preparation are disclosed in
US. Patent No. 3,762,887, US. Patent No. 3,617,095,
10 US. Patent No. 4,217,109, US. Patent No. 4,101,293 and
British Patent No. 1,523,193.
Regardless, however, of the form in which the coal
is ultimately employed, the coal or coal combustion products
must be cleaned because they contain substantial amounts of
Selfware, nitrogen compounds and mineral matter, including
significant quantities of metal impurities. During come
bastion these materials enter the environment as sulfur
; dioxides, nitrogen oxides and compounds of metal impurities.
If coal is to be accepted as a primary energy source, it
must be cleaned to prevent pollution of the environment
either by cleaning the combustion products of the coal or
the coal prior to burning.
Accordingly, physical as well as chemical coal
cleaning (beneficiation) processes have been explored.
inn general, physical coal cleaning processes involve
pulverizing the coal to release the impurities, wherein
the fineness of the coal generally governs the degree
to which the impurities are released. However, because
the posts of preparing the coal rise exponentially
Wyeth the amount of fines to be treated, there is an economic
optimum in size reduction. Moreover, grinding coal even to
extremely fine sizes may not be effective in removing all
I
1 the-impurities. Based on the physical properties that
effect the separation of the coal prom the impurities,
physical coal cleaning methods are generally divided into
four categories: gravity, flotation, magnetic and electric
5 eel methods. In contrast to physical coal cleaning, chemical coal cleaning techniques are in a very early stave of
development. Known chemical coal cleaning techniques
include, for example, oxidative desulfurizatioh of coal
(sulfur is converted to a water-soluble form by air oxidation),
10 ferris salt leaching (oxidation of portico sulfur with
ferris sulfate), and hydrogen peroxide-sulfuric acid leaching.
Other methods are also disclosed in the above-noted refer-
once to the Encyclopedia of Chemical Technology, Volume 6,
pages 314-322.
While it is obvious from the foregoing that
enormous efforts have been made to make coal a more
utilizable source of energy, further work and improvements
are still necessary and desirable before coal, coal mixtures
and other solid carbonaceous fuel sources are accepted on
20 a wide scale as primary sources of energy.
Thus, the present invention relates to a process
which comprises contacting Callahan an aqueous medium with --
a surface treating mixture comprising a polymerizable
monomer, a polymerization catalyst and a liquid organic
25 carrier, thereby providing a hydrophobic and oleophilic
coal product adapted to the removal of further ash and
sulfur by water separation techniques. The resultant pro-
duct is highly suitable for the formation of beneficiated
coal slurries and/or cleaned particulate coal.
Moreover, in a further embodiment of the present
invention an improved process for beneficiating coal is
--5
1 provided which comprises chemically surface treating coal
in an aqueous medium to render said coal hydrophobic and
oleophilic, thereafter separating the hydrophobic and
oleophilic coal phase from the ash containing water phase
5 and recovering the hydrophobic and oleophilic coal phase,
the particular improvement comprising subjecting the chum-
icily surface treated hydrophobic and oleopnilic coal to
high shear intermixing with an aqueous wash medium whereby
additional ash and other hydrophilic impurities are
10 released into the aqueous medium and a hydrophobic coal
phase floats upon and separates from a water phase.
In the accompanying figures, Fig. 1 is a flow
diagram illustrating the process of the present invention
whereby solid carbonaceous material, such as coal, is
15 beneficiated.
Fist 2 is a flow diagram illustrating a preferred
manner by which solid carbonaceous materials, such as
coal, are beneficiated according to the present invention.
Fig. 3 is a further flow diagram depicting another
20 preferred mode by which the present invention is performed.
Fig. 4 is an illustration of a typical vessel
which may be utilized in the practice of the present invention..
In accordance with the present invention, a
highly beneficiated coal product is produced by a process
25 which involves surface treating particles of coal in an
aqueous medium with a surface treating admixture come
prosing a polymerizable monomer, a polymerization catalyst
and a liquid organic carrier, thereby rendering said coal
particles hydrophobic and oleophilic. Thus, the process
30 of this invention provides a highly beneficiated coal product
of relatively low water content which can be even further
dehydrated (dried) to a remarkable degree without the use
1 of thermal energy. The ash content of the coal prepared
by the present process is reduced to low levels and mineral
sulfur compounds present are also removed. Moreover, the final
coal product has enhanced BTU content and can be burned
was a solid or combined with fuel oil or water to produce
highly desirable beneficiated coal mixtures or slurries
which are readily transportable and cleanly burned.
As used herein, the term "beneficiation" is intended
to include methods for cleaning or otherwise removing impurities
LO from a substrate, such as coal and to the recovery of coal from
coal streams, such as, for example, the recovery of coal from
waste streams in coal processing operations and the con-
cent ration or detouring of coal streams or slurries such as,
for example, by the removal of water in, for example, coal
slur pipelines.
In one embodiment for carrying out the present
invention, wherein raw-mined coal is employed as
the feed stock, it is initially preferred to reduce raw
mined coal or other solid carbonaceous material to a fine
20 diameter size and to remove unwanted rock, heavy ash and
the like materials collected in the mining operation.
Thus, the coal is pulverized and initially cleaned, usually
in the presence of water, wherein the coal is suspended
and/or sufficiently wetted to permit fluid flow The coal
issue pulverized employing conventional equipment such as,
for example, ball or rod mills, breakers and the like.
It is generally desirable, although not necessary
to the present process, to employ certain water conditioning
(treating) additives in the pulverization operation. Such
30 additives assist in rendering the ash more hydrophilic,
which facilitates the separation thereof in a manner
that will be discussed hereinafter. Typical additives
kick are useful for purposes of this invention include
conventional inorganic and organic dispersants, surfactants,
5 and/or wetting agents. Preferred additives 'or this purpose
include sodium carbonate, sodium pyrophosphate, and the like.
The koalas slurry formed in the pulverization
operation is typically one having a coal to water ratio of
from about 0.5:1 to about 1:5 and preferably about 1:3
lo parts by weight, respectively. If utilized, the water
treating additives, herein before described, are employed
in small amounts, usually, for example, from about 0.25 to
about 5%, based on the weight of dry coal. While it is
generally recognized that more impurities are liberated as the
15 size of the coal is reduced, the law of diminishing returns
applies in that there is an economic optimum which governs
the degree of pulverization. In any event, for the purposes
of this invention, it is generally desirable to crush
the coal to a particle size of from about 48 to about less
20 than 325 mesh, preferably about 80% of the particles being
of about a 200 mesh size (Tyler Standard Screen Size).
Any type coal can be employed in the process of
the present invention. Typically, these include, for example,
bituminous coal, sub-bituminous coal, anthracite, lignite
25 and the like. Other solid carbonaceous fuel materials,
such as oil shale, tar sands, coke, graphite, mine tailings,
coal from refuse piles, coal processing fines, coal fines
from mine ponds or tailings, carbonaceous local matter
and the like are also contemplated for treatment by the
prowesses herein. Thus, for the purposes of this invention,
the term "coal" is also intended to include these kinds of
other solid carbonaceous fuel materials or streams.
l In carrying out the beneficiation process herein,
the coal-aqueous slurry, containing the pulverized coal,
is contacted and admixed with a surface treating mixture
comprised of a polymerizable monomer, polymerization catalyst
5 and a small amount of a liquid organic carrier, such as fuel
oil.
Any polymerizable monomer can be employed in the sun-
face treating polymerization reaction medium. While it is more
convenient utilize monomers which are liquid at ambient them-
; lo portray and pressure, gaseous monomers which contain olefinicunsaturation permitting polymerization with the same or dip-
fervent molecules can also be used. Thus, monomers intended
to be employed herein may be characterized by the formula
XHC=CHX' wherein X and X' each may be hydrogen or any of a
15 wide variety of organic radicals or inorganic substituents.
Illustratively, such monomers include ethylene, propylene,
battalion, tetrapropylene, isoprene, butadiene, such as 1,4-
butadiene, pentadiene, dicyclopentadiene, octadiene, olefinic
petroleum fractions, styrenes vinyltoluene, vinyl chloride,
20 acrylonitrile, methacrylonitrile, acrylamide, methacrylamide,
N-methylolacrylamide, acrolein, malefic acid, malefic android,
fumaric acid, abietic acid and the like.
A preferred class of monomers for the purposes of
the present invention are unsaturated carboxylic acids, esters,
25 androids or salts thereof, particularly those included
within the formula I wherein R is an olefinically
RC-OR'
unsaturated organic radical, preferably containing from about
2 to about 30 carbon atoms, and R' is hydrogen, a salt-
30 forming cation such as alkali metal, alkaline earth mottler ammonium cation, or a saturated or ethylenically us-
I
1 saturated hydrocarbyl radical, preferably containing from to about 30 carbon atoms, either unsubstituted or sub-
stituted with one or more halogen atoms, carboxylic acid
groups and/or hydroxyl groups in which the hydroxyl hydrogen
5 may be replaced with saturated and/or unsaturated azalea groups,
the latter preferably containing from about 8 to about 30
carbon atoms. Specific monomers conforming to the fore-
going structural formula include unsaturated fatty acids
such as oleic acid, linoleic acid, linolenic, ricinoleic,
10 moo-, dip and triglycerides, and other esters of unset-
unrated fatty acids, acrylic acid, methacrylic acid, methyl-
acrylate, ethyacrylate, ethylhexylacrylate, tertiarybutyl-
acrylate, oleylacrylate, methylmethacrylate, oleylmeth-
acrylate, stearylacrylate, stearylmethacrylate, laurylmeth-
acrylate, vinyl acetate, vinylstearate, vinylmyristate,
vinyllaurate, unsaturated vegetable seed oil, soybean oil,
rosin acids, dehydrated castor oil, linseed oil, olive oil,
peanut oil, tall oil, corn oil and the like. For the
purposes of this invention, tall oil and corn oil have
20 been found to provide particularly advantageous results. Corn
oil is especially preferred. Moreover, it is to be clearly
understood that compositions containing compounds within the
foregoing formula and in addition containing, for example,
saturated fatty acids such as palmitic, Starkey, etc. are
25 also contemplated herein. Also contemplated herein as
monomers are aliphatic anger polymeric petroleum materials.
` The amount of polymerizable monomer will vary
depending upon the degree of surface treatment desired. In
general, however, monomer amounts of from about 0.005 to about
30 0.1%, by weight, of-the- dry coal are used.
-10--
The catalysts employed in the coal surface treater.
beneficiation reaction of the present invention are any such
materials commonly used in polymerization reactions. these
include, for example, anionic cat ionic or free radical catalysts.
5 Free radical catalysts or catalyst systems also referred to
as addition polymerization catalysts, vinyl polymerization
catalysts or polymerization initiators are preferred heroin.
Thus, illustratively, free radical catalysts contemplated herein
include, for example, inorganic and organic peroxides such as
bouncily peroxide, methyl ethyl kitten peroxide, tert-butyl-
hyaroperoxide, hydrogen peroxide, ammonium per sulfate, Detroit-
butylperoxide, tert-butyl-perbenzoate, parasitic acid and in-
cludin~ such non-peroxy free-radical initiators as the dyes
compounds such as 1,1'-bisazoisobutyronitrile and the like.
Typically, for the purposes of this invention ! any
catalytic amount (e.g. 1 pound per ton of dry coal feel of
the foregoing described catalysts can be used.
Moreover, free radical polymerization systems
commonly employ free radical initiators which function
20 to help initiate the free radical reaction. For the purposes
herein, any of those disclosed in the prior art, such as
those disclosed, for example, in US. Patent No. 4,033,852,
may be used. Specifically
some of these initiators include, for example, water
25 soluble salts, such as sodium per chlorate and perorate, sodium
per sulfate, potassium per sulfate, ammonium per sulfate, silver
nitrate, water soluble salts of noble metals such as platinum
and gold, sulfites, nitrites and other compounds containing the
like oxidizing anions, and water soluble salts of iron, nickel
30 chromium, copper, mercury, aluminum, cobalt, manganese,
zinc, arsenic, antimony, tin, cadmium, and the like.
1 Particularly preferred initiators herein are the water
soluble copper salts, i.e. cuprous and cupric salts, such
as copper acetate, copper sulfate and copper nitrate. Most
advantageous results have been obtained herein with cupric
5 nitrate, Queen. Further initiators contemplated herein
include metal salts of organic mottles, typically
metal salts of organic acids or compositions containing
lo organic acids, such as naphthenates, twilights, octanoates,
etc. and other organic soluble metal salts, said metals
including co per, chromium, mercury, aluminum, antimony,
arsenic, cobalt, manganese, nickel tin, lead, zinc, rare
earths, mixed rare earths, and mixtures thereof and double
15 salts of such metals. The combination of copper and cobalt
silts, particularly cut fig nitrate and cobalt naphthenate,
have been found to provide particularly good and synergistic
results.
The amounts of free radical initiator contemplated
20 herein are any catalytic amount and generally are within the
range of from about 10-1000 Pam (parts per million) of the
metal portion of the initiator, preferably 10-200 ppm,based
on the amount of dry coal.
- The surface treating reaction mixture of the
25 present invention also includes a liquid organic carrier.
This liquid organic carrier is utilized to facilitate
contact of the surface of the coal particles with the
polymerization reaction medium. Thus, liquid organic
carriers included within the scope of this invention are,
Jo for example, fuel oil, such as No. 2 or No. 6 fuel oils,
non-fuel oil liquid organic carriers, such as hydra-
carbons including, for example, Bunsen, Tulane,
I 3
-12-
1 zillion, hydrocarbons fractions, such as naphtha and medium
boiling petroleum fractions (boiling point 100-180C);
dimethylformamide, tetrahydrofuran, tetrahydrofurfuryl
alcohol, dimethylsulfoxide, methanol, ethanol, isopropyl
5 alcohol, acetone, methyl ethyl kitten, ethyl acetate and
the like and mixtures thereof.
The amounts of liquid organic carrier, such as fuel
oil, utilized in the surface treatment reaction herein are
generally in the range of from Abbott to about 5% by
lo weight based on the weight of dry coal.
The surface treatment reaction of the present
process is carried out in an aqueous medium. The amount
of water employed for this purpose is generally from about
65% to about 95~, by weight, based on the weight of coal
15 slurry.
The surface treating reaction conditions will,
of course, vary, depending upon the specific reactants
employed and results desired. Generally, however, any
polymerization conditions which result in the formation
20 of a hydrophobic or oleophilic surface on the coal can
be utilized. More specifically, typical reaction conditions
include, for example, temperatures in the range of from
about 10C to about 90C, atmospheric to nearly atmospheric
pressure conditions and a contact time, i.e. reaction time,
25 of from about 1 second to about 30 minutes, preferably
from about l second to about 3 minutes. Preferably, the
surface treatment reaction is carried out at a temperature
of from about 15C to about 80C and atmospheric pressure
for about 2 minutes. In general, however, the longer the
JO reaction time, the more enhanced are the results.
-13-
1 In the practice of the present invention, the
coal can ye contacted with the surface treating ingredients
by employing various techniques. For example, one technique
is to feed the aqueous pulverized coal slurry through a
5 spraying means, e.g. nozzle, and add the surface treating
ingredients, i.e. polymerizable monomer, polymerization
catalyst, initiator and liquid organic carrier to the
aqueous coal spray. The resultant total spray mixture is
then introduced to an aqueous medium contained in a
10 beneficiation vessel. In a preferred embodiment when this
technique is used, the surface treated aqueous coal mixture
now in the vessel is recycled to the same vessel by
refeeding the mixture to the vessel through at least one of
said spraying means.
In a second technique, the aqueous coal slurry and
surface treating ingredients, i.e. polymerizable monomer,
polymerization catalyst, initiator and liquid organic
carrier, are admixed in a premix tank and the resultant
admixture is sprayed, e.g. through a nozzle, into an
awakes medium contained in a beneficiation vessel. In
another and third technique, the resultant surface
treated aqueous coal mixture, formed in the beneficiation
vessel in accordance with the foregoing described second
technique, is recycled to the same vessel by refeeding
Thea mixture to the vessel through at least one of said
spraying means.
As the surface treating reaction is completed,
the hydrophobic and oleophilic beneficiated coal particles
float to the surface of the liquid mass. The ash, still
30 remaining hydrophilic, tends to settle and is removed to
the water phase. Thus, the coal which results from react
1 Shea with the herein before described polymerizable surface treating mixture is extremely hydrophobic and oleophilic
and consequently readily floats and separates from the
aqueous phase, providing a ready water washing and for high
5 recoveries of coal. The floating hydrophobic coal is also
readily seperablefrom the aqueous phase (for example, a skim-
mint screen may be used for the separation), which contains
ash, sulfur and other impurities which have been removed from
the coal While it is not completely understood and while
not wishing to be bound to any theory, it is believed that
the surface treatment polymerization reaction involves the
formation of a polymeric organic coating on the surface of
the coal by molecular grafting of polymeric side chains on
the coal molecules.
In the practice of the present invention, the
surface treated coal is preferably subjected to at least
one further wash step wherein the coal phase or phases are
redispersed, with good agitation, e.g. employing high speed
mixers, as a slurry in fresh wash water. Preferably,
20 the initially surface treated coal is added to the wash
water under atomizing pressure through a spray nozzle thus
forming minute-droplets in air which-are--directed-wi-th
force onto and into the surface of the fresh water mass.
In this manner, some air is incorporated into the system.
By spraying, the wash water and the treated coal
phase are intimately admixed under high speed agitation
and/or shear produced by the spray nozzle under super
atmospheric pressures. In this manner, the hydrophobic
coal particles are jetted into intimate contact with
30 the wash water through one or more orifices of the spray
nozzle thereby inducing air inclusion, both in the passage
through the nozzle as well as upon impingement upon and
into the air-water interface of the wash water bath.
-15-
3~6~J~
l US. Pa-tents 4,3~7,126 and ~,3~7,127
both issued on August 31, 1982, describe and claim
a particularly effective method and apparatus for sepal
rating the treated coal particles from unwanted ash and
5 sulfur in the water phase utilizing an aeration spray
technique, wherein a coal froth phase is formed by spraying
or injecting the treated coal-water slurry into the surface
of the cleaning water. Briefly, according to the method
and apparatus there described, the coal slurry is injected
lo through at least one selected spray nozzle, preferably
of the hollow cone type, at pressures, for example, at from
about 15-20 prig, at a spaced-apart distance above the
water surface, into the water surface producing aeration
and a frothing or foaming of the coal particles, causing
15 these particles to float to the water surface for skimming
of.
The foregoing described washings may be carried
out with the treated coal slurry in the presence of simply
water at temperatures of, for example, about 10 to about
20 90C, preferably about 30C, employing from about 99 to about
65 weight percent water based on the weight of dry coal
feed. Alternatively, additional amounts of any or all of the
heretofore described surface treating ingredients i.e. polyp
merizable monomer, catalyst, initiator, liquid organic
25 carrier, may also be added to the wash water. Moreover, the
washing conditions e.g. temperature, contact time, etc.,
utilized when these ingredients are employed can be the
same as if only water is present or the washing conditions
can be the same as those described heretofore with respect
30 to surface treatment of the coal with the surface treating
mixture. Of course, water conditioning additives may
also be utilized during the washing steps, if desired.
-16
I
1 After washing and/or additional surface treatment,
the beneficiated coal may be dried to low water levels serenely
by mechanical means, such as by centrifugation, pressure or
vacuum filtration etch, thus avoiding the necessity for
costly thermal energy to remove residual water. The
beneficiated coal prepared by the process of this invention,
as herein before described, generally contains from about 0.5%
to about 10. 06 by weight ash based on the weight of dry
coal. Moreover, the sulfur content is from about 0.1~ to
10 about 4% by weight, preferably about 0.3 to about buzzed
on the weight of dry coal and the water content is from
about 2% to about 25%, preferably from about 2% to about 15%,
by weight, based on the weight of dry coal.
At this point, the beneficiated coal can be used as
15 a high energy content, ash and sulfur reduced, fuel product.
This beneficiated fuel product can be utilized in a direct
firing burner apparatus. Alternatively, the beneficiated
particulate coal can be blended with a carrier such as oil
to provide a highly stable and beneficiated coal slurry,sucn
20 as a coal-oil mixture (COY). Oil, preferably fuel oil, such
as No. 2, or No. 6, is blended with the beneficiated coal at
; any desired ratio. These ratios typically include from
about 0.5 to about 1.5 parts by weight coal to 1 part oil.
Preferably a 1:1 weight ratio is employed.
-It is also to be understood herein that the solid
beneficiated coal product of the present invention can also
be redispersed in aqueous systems for pumping through pipe-
lines. If desired, to provide improved stability, selected
metal ions, by way of their hydroxide or oxide, can be added
Jo to the aqueous dispersion to preferably adjust the pi of
the slurry to above 7. Thus, for this purpose, alkali
and/or alkaline earth metals, each as, sodium, potassium,
calcium, magnesium, etc., hydroxide or oxide scan be used.
-lo-
3 lo
1 Sodium hydroxide is preferred.
It has also been discovered herein that a stabile
iced keelhaul mixture can be provided by the presence therein
of the alkali or alkaline earth metaled (sodium, poles-
5 slum, calcium, magnesium, etc.) salt of a fatty acid of the
formula wherein R" is a saturated or an olefinically
R"C-OH
unsaturated organic radical. Thus, the herein before
described unsaturated fatty acids, i.e., O , wherein
RCOR'
R' is hydrogen and R is as defined before, are also intended
for use herein. the presence of these fatty acid salts in the
beneficiated coal-oil mixtures of this invention permits the
ready dispersion of the coal in the fuel oil to produce
15 a gel or other structure which retards settling almost
indefinitely. Other metal ions, in addition to alkali
or alkaline earth metals are also useful to form stabilizing
fatty acid salts. These other metals include, for example,
iron, zinc, aluminum and the like.
Generally, the amount of fatty acid utilized in
forming the stable coal-oil mixture will be from 3.0 to 0.5%
by weight, based on the total weight of the mixture.-- The
amount of alkali or alkaline earth containing compound utile
iced to form the gel will be sufficient to neutralize a sub-
staunchly portion of the fatty acid and thus generally varies from about 0.1 to 1.0% and usually 0.1% to 0.6% by weight,
based on the total weight of the coal-oil mixture. Preferably
for a 50:50 coal-oil mixture, 1.5~ by weight acid and 0.3~
by weight of neutralizing compound are added to the mixture.
3 An alternative practice herein to form stable
coal-oil mixtures is to subject the coal-oil mixture to an
-18-
additional surface -treating reaction where additional amounts
of polymerizable monomer and polymerization catalyst are added
to a mixture of the beneficiated coal in oil. In this case,
the polymerizable monomer is again an unsaturated carboxylic
acid as described above, preferably tall oil, used in amounts
of 3.0 to 0.5% by weight, preferably 1.5%, based on the total
weight of the mixture. The polymerization catalyst can be
any of those described herein before and is preferably cupric
nitrate, used in amounts of 2.0 to lo Pam (parts per million),
lo preferably 5 Pam, based on the total weight of the mixture.
The polymerizable monomer and polymerization catalyst are added
to the coal-oil mixture with stirring. Thereafter, alkali
or alkaline earth metal compound, such as sodium hydroxide,
in an amount of 0.6 to 0.1~, by weight, preferably 0.3~, based
on the total weight of the mixture is added to the mixture.
The resulting product is a preferred stabilized coal-oil
mixture.
Another process which is suitable herein for proper-
in stable beneficiated coal-oil mixtures involves admixing
beneficiated coal with a fatty acid ester, such as triglyceride,
preferably tallow, and a base, such a sodium hydroxide. A
further process is described and claimed in US. Patent
4,306,883 granted December 22, 1981, which describes a process
for forming stabilized coal-oil mixtures by initially admixing,
under low shear conditions and at an elevated temperature,
- coal, oil, polymerizable monomer and polymerization catalyst,
and immediately thereafter subjecting the mixture to a condo-
lion of high shear agitation at the same elevated temperature.
The resultant coal-oil
-- 1 9 -
3~6~
1 mixture is then treated with a golfing agent, such as
a hydroxide, like sodium hydroxide, to form a stable bone-
ficiated coal-oil mixture which is in the form of a gel or
thixotropic mixture.
The coal fuel oil products, i.e. coal-oil
mixtures, of the present invention have unique properties.
For example, the present coal-oil mixtures are thixotropic,
have increased energy content, can utilize coal having
low ash, low sulfur and low moisture content and a wide
,
10 variety of coals and can provide the potential for a widely
expanded market for coal as a fluid fuel thereby assisting
in the conservation of petroleum.
With specific reference to the drawings herein,
and particularly to Fig. 1, the process of this invention
15 is illustratively carried out, for example, by initially
pulverizing raw mined coal in pulverization zone 10 in the
presence of water, and if desired, water conditioning additives,
to form an aqueous coal slurry. This aqueous coal slurry
is mixed in line 6 with surface treating reagents and/or
20 additives, fed to line 6 from tanks 1, 2, 3, and 4 via
line 5, and the thusly treated coal-slurry is introduced
to beneficiation zone 12, as shown. Tanks 1, 2, 3 and 4 con-
lain, for example, polymerizable monomer, free radical cat-
alyst, free radical initiator and liquid organic carrier,
25 respectively. Raw mined coal is fed to zone 10 through line
23; water is fed through line 21 and water conditioning
additives may be introduced via line 25. Unwanted materials,
such as rock, are removed via line 27.
Water is generally the principal ingredient
3 in beneficiation zone 12. Thus, the treated coal-slurry
-20-
being fed to zone 12 via line 6 is now hydrophobic and
oleophilic and after admixture with the wash water in zone 12,
for example, by high speed mixer or spray atomizer,
readily floats on the surface of the water, thereby
forming a coal froth phase and an aqueous phase in zone 12.
The coal froth phase in zone 12 is readily removed from
zone 12 (for example, by skimming) through line 47 to provide
a beneficiated, i.e. clean, coal product according to the
present invention having a reduced ash, sulfur and water
LO content If desired, the clean coal from line 47 may be
further dried to remove additional water. The aqueous
phase, remaining in zone 12, contains ash, sulfur and other
hydrophilic impurities and can be removed therefrom
through line 11.
Alternatively, in carrying out the process of the
present invention, in accordance with Fig. 1, the surface
treating reagents and/or additives may be admixed with the
aqueous coal slurry directly in beneficiation zone 12. Thus,
these reagents and/or additives can be introduced to zone 12
20 via line 31 (monomer), 33 (free radical catalyst), 35 (free
radical initiator) 37 (water), 39 (liquid organic carrier).
The coal-slurry is fed to zone 12 through line 6 and-thusly
admixed with-the reagents in zone 12. In another manner, as
described herein before, the surface treating additives can
byway added to the coal spray coming from line 6.
With specific reference to Pig. 2, the process of
this invention is illustratively continuously carried out
beginning with raw mined coal and ending with a coal-oil
mixture, although as indicated above other feedstocXs and
prosecutes, such as beneficiated particulate coal and coal-water
mixtures are also contemplated herein. Thus, referring to
Pig. 2, raw coal is initially pulverized in pulverization
zone lo in the presence of water and, if desired, water
conditioning additives, to form an aqueous coal slurry. This
~21-
~.,23~68~
1 aqueous coal slurry is fed to mix zone 11, through line 9,
and admixed in zone 11 with surface treating reagents/
additives transported prom reagent and/or additive tanks
lay PA and PA and PA, via line 8. Tanks lay PA, PA and
5 PA contain, for example, polymerizable monomer, free radical
catalyst, free radical initiator and liquid organic carrier,
respectively. Raw mined coal is fed to zone lo through
line AYE; water is fed through line AYE and water condo-
toning additives may be introduced to zone lo via line
10 AYE. The resultant admixture in mix zone 11 which contains
the initial chemically treated hydrophobic and oleophilic
coal, is then introduced to a first beneficiation zone
AYE through line 29.
Alternatively, surface treating additives (or add-
15 tonal surface treating additives) i.e., polymerizable monomer,
polymerization catalyst, liquid organic carrier, herein before
described, may be added directly to zone AYE (or zones 14 and
16~, for example, through line AYE (monomer), AYE (free
radical catalyst), AYE (free radical initiator), Atari),
20 AYE (liquid organic carrier), or they can be admixed before-
hand along with the pulverized coal slurry in lines leading
to the beneficiation zones or vessels in the zones. In the
case where the surface treating reagents/additives are added
directly to zone AYE, the coal slurry from zone lo may be
25 added directly to zone AYE via lines PA and 29. In addition,
as described before the coal slurry in the benefication vessel
can be recycled within each particular vessel to achieve
greater mixing and separation.
The coal in zone AYE is extremely hydrophobic and
3 oleophilic and after good agitation with, for example, a high
-22-
~3~q3
1 speed mixer or spray atomizer, a coal froth phase ensues
which is recovered. A screen ma be advantageously used
for the separation and recovery of the flocculated coal.
If desired, the recovered coal can be introduced, via lines
5 47 and 49 to a further sequence of wash steps, (e.g. zones
14 and 16) wherein with further agitation of the recovered
hydrophobic coal froth from zone AYE, provided by high
speed mixers, or other means, such as a spray atomizer,
additional ash is released to the water phase.
The water-wet~ed ash suspension phase, which is also
formed in zone AYE, can be recovered and can be sent to waste
and water recovery, after which the water can be recycled for
reuse in the process as shown in Fig. 2.
Alternatively, as indicated above, additional ash
15 and sulfur is removed from the beneficated coal froth phase
by a series of counter-current water-wash steps, i.e.
the water phase in the wash zones 14 and 16 can be recycled
to a previous wash zone, as also illustrated in Fig. 2.
As indicated herein before, in addition to water, zones AYE,
20 14 and 16 may also contain any or all of the foregoing
chemical surface treatment additives. The finally washed
and surface treated coal exiting zone 16 via line 57 can
be dried to a very low water level by, for example, centric
fugation. The water which is taken off in the centrifuge
25 may also be recycled in the process as shown. The recovered
dry beneficiated coal product can be used directly as such
as a solid fuel or can be blended with a carrier to form a
highly desirable beneficiated coal slurry such as a coal-
oil-liquid fuel mixture. :
In the preparation of the coal-oil mixture, Fig.
--23-
I
1 illustrates that the dry beneficiated surface treated coal is
fed to a keelhaul dispersion mixer, wherein, preferably
herein before identified O acid, such as tall oil
R"C-OH
5 or naphthenic acid, may be added along with alkali metal
hydroxide, such as sodium or calcium hydroxide, to form a
stable dispersion. If desired, further surface treatment
of the coal may be carried out in the coal-oil dispersion
mixer by adding a polymerizable monomer and polymerization gala-
10 lust to the admixture, as described above, with or without sub-
sequent addition of alkali or alkaline earth hydroxide.
Illustratively, coal-fuel dispersion can be carried out,
either continuously or bushes, in, for example, con-
ventional paint grinding equipment, wherein heavy, small
15 grinding media are used to shear the dispersion into a non-
settling plowable coal-fuel product of thixotropic nature.
It is to be understood herein that while the coal-
oil admixture process illustrated herein utilizes coals
beneficiated as described herein, any coal, e.g. raw coal,
20 coal beneficiated by processes not herein described and the
like, can also be employed to form stable coal-oil mixtures in
accordance with the process of the present invention.
Fig. 3 illustrates a further preferred mode by
which the present invention may be performed. with specific
25 reference thereto, raw mined coal is introduced to pulverization
; zone 70, through line 103 and pulverized therein in the
presence of water which is added via line 101. The water
preferably continuously conditioning or treating additive such
as an inorganic or organic surfactant, wetting agent, disk
30 peasant or the like which enhances the effectiveness of the
water. Typical organic surfactants (such as Briton X-100)
* Trade mark
I
l include anionic, cat ionic and non ionic materials. Sodium
pyrophosphate is a preferred additive for the purposes of
this invention. Conditioning ingredients can be fed to zone
70 through line 105, for example. The aqueous coal slurry
5 in zone 70 is sent to mix zone 82 via line Al and admixed
therein with reagents/additives from tanks is, us, us and
4B containing polymerizable monomer, free radical catalyst,
free radical initiator and liquid organic carrier, respectively,
for example.
lo The aqueous chemically treated hydrophobic and
oleophilic coal slurry admixture formed in zone 82 is fed
to a first water wash zone 72 through line 107 and through
high shear nozzle D, whereby the velocity of the stream
and the shearing forces are believed to break up the coal
15 phase stream into fine droplets which in turn can pass
through an air interface within wash zone 72 and impinge
downwardly upon and forcefully jet into the mass of the
continuous water in, e.g. a tank or tanks, contained therein.
If desired, further surface treating reagents, and/or add-
20 lives, herein before identified, may be added to zone Andre zones 74 and 76), for example, through lines 109
(polymerizable monomer),--lll (free radical catalyst), 113
(tree radical initiator), 115 (water), 117 (liquid organic
carrier). The hydrophobic and oleophilic coal phase, which
25 ensues in zone 72, is then preferably, as shown, fed to a
further sequence of wash zones, via line 47.
Without intending to be limited to any theory
or reaction mechanism, it is believed to be helpful to discuss
the phenomena thought to provide some of the advantageous
30 results achieved by the process herein. Thus, the high shear-
in forces created inmi~ing,.such as in nozzle D, are believed
-25-
I I
1 to assist in breaking up the coal-oil water floes as the disk
pursed particles forcefully enter the surface of the water
in the tank, thereby water-wetting and releasing ash and
other impurities from the interstices between the coal blocs.
5 The coal floes are thereby broken up so that the trapped
ash and other impurities are freed and introduced to the aqueous
phase and thus separated from the coal particles. The finery
divided coal particles, whose surfaces are now believed
surrounded by polymer and liquid organic carrier, SEIKO 25
10 fuel oil, also now contain (occluded) air sorbed in the
atomized particles as a result of the shearing effects
of the nozzle. The combination of surface treatment and
sorbed air causes the flocculated coal to decrease in
apparent density and to float on the surface of the water,
15 as a distinct coal froth phase. Thus, the coal particles
assume a density less than water, repel water by virtue
of their increased hydrophobicity and quickly float to the
surface of the water.
By the foregoing technique, not only is ash
20 substantially removed from the treated coal product, but
the entrapped air and the more hydrophobic and oleophilic
coal surfaces provide for a marked increase in the yield of
total beneficiated treated coal, which is ultimately recovered.
The still hydrophilic ash remains in the bulk
25 aqueous phase and tends to settle downward in the tank by
gravity and is withdrawn from zone 72 in an ashtray stream
119 from the base of the vessel. Some small amount of fine
coal which may not be separated completely can be transferred
with the aqueous phase (withdrawn ash-water stream) to a fine
Jo coal recovery zone 121, as shown in jig. 3. Recovered goal
-26-
I
lines can be recycled via line 123 to the aqueous coal slurry
in zone 70.
The wash process carried out in zone 72 can be
repeated, employing a counter-current wash system, whereby the
coal progresses to a cleaner state through sequential intro
diction to beneficiation zones 74 and 76, via lines 47
and 49, as illustrated in Fig. 3. Concomitantly, clean assay
water becomes progressively loaded with water soluble and
water wetted solid impurities extracted by the wash water.
As described before, the intimately admixed
ash-water suspension coming from zone 72, containing some
small amounts of particulate coal, is forwarded to fine
coal recovery zone 121 where high ash-low water solids are
recovered and expelled for removal from the process and
15 the fine coal is recycled, as shown. The wash water can
be further treated at Tao control the condition of the
recovered water prior to recycle. The cleaned water is
recycled to the original aqueous coal slurry or such other
make-up as the overall process may require to balance material
20 flow.
As shown in Fig. 3, the coal froth phases resulting
in zones 72 and 74 can be introduced for further washings via
nozzles E and F, respectively. In this manner, the coal
particles are again atomized. The velocity and high shear
25 created by nozzles E and F once again permit wash water
contact with any ash still retained in the interstices of the
coal floes, thereby assisting, in each wash step, to release
ash to the aqueous phase. The aqueous phases in zones 72,
74 and 76 float the flocculated coal-oil-air mass to the
Jo top of the respective tanks.
The final coal froth phase in zone 76 is fed to a
centrifuge, via line 57, for drying. The beneficiated, clean
-27-
I I
1 coal phase is thereby remarkably dried without the necessity
for thermal energy, which it believed due to the reduced
attraction for water between the large coal-oil surfaces and
the water physically occluded there between in the flocculated
5 dry coal recovered from the mechanical drying step.
The dry hydrophobic cleaned coal can be used
advantageously at this point as a higher energy content, ash
and sulfur reduced solid fuel, which is referred to herein as
Product I. '-'hi solid fuel can be utilized in direct firing
10 or to forln ~eneficiated coal slurries as described above.
As indicated above in another embodiment of this
invention, a liquid fuel mixture, which is easily pumped
as a liquid, but which is of such theological quality as to
form a thixotropic liquid, can also be provided. A
15 thixotropic liquid is one that has "structure" or tends to
become viscous and gel-like upon standing quiescently,
but which loses viscosity and the "structure" or gel decreases
markedly and rapidly upon subjecting the thixotropic liquid
to shearing stresses, as by agitation through mixing and
20 pumping processes or by heating.
In the practice of this invention, as illustrated
by Fig. 3, the dry, beneficiated coal Product I is mixed
with a quantity of fuel oil (illustratively 1:1 by weight
and preferably heated to reduce viscosity especially in
25 instances wherein the fuel oil is of a heavy viscosity grade)
in a mix tank to provide a pump able fluid mixture.
Alternatively, the fuel-oil coal mixture in the
mix zone may be subjected to an additional surface
treatment step, in line with the general reaction procedure
Jo employed in the initial surface treatment beneficiation,
herein before described. For this purpose any of the herein-
-28~
''3
1 beware identified polymerizable monomers, such as tall oil,
corn oil, and the like may be used and added to the mix
zone along with any of the herein before identified polymer-
ization catalysts and/or initiators. Moreover, the saturated
5 carboxylic acids herein before described may be used alone
or in combination with the unsaturated acids, if desired.
In the case wherein saturated acids are used alone, initiators
and catalysts need not be employed. Naphthenic acids are
illustrative of saturated acids which may be used.
- The admixture of surface treated coal, fuel oil
and carboxylic acid can then be substantially neutralized,
with a water soluble alkali metal, such as from a hydroxide,
like sodium hydroxide, calcium hydroxide or mixtures thereof
as indicated above to Norm a stable coal-oil mixture. A
15 liquid gleam coal-oil fuel mixture (Product II), having no
tendency to settle out, is storable recovered to provide a
plowable high energy source for a wide variety of end uses.
Alternatively, the beneficiated coal product I can
be slurred with water to provide coal-aqueous slurries or
20 mixtures.
Fig. 4 illustrates a unit 55 which is suitable as
a froth flotation vessel useful in any of the wash and/or
beneficiation zones employed in the present process. In
this unit, the aqueous coal slurry i.e. admixture of coal,
25 water and preferably surface treating reagents/additives,
is sprayed into the vessel through lines 29 and through
spray nozzles 61. Additional surface treating reagents/
additives or any other desired ingredients may also be
added via lines 31, 33, 35, 37 and 39. In this vessel the
30 coal froth is skimmed off from the main portion of the
I
vessel into a collector compartment and can be introduced
to the next zone via line 147, for example. The aqueous-ash
phase in the main portion of the vessel is removed through
line 41, for example.
It is to be understood herein that any of the zones
illustrated in Figllres 1 3 may comprise a single vessel or zone
or any number of vessels or zones arranged in a manner suitable
and in accordance with carrying out the invention as described
herein.
In order that those skilled in the art may better
understand how the present invention may be practiced, the
following examples are given by way of illustration and not
by way of limitation.
-30-
EXAMPLE 1
200 grams of Pittsburgh seam coal having an
initial ash content of 6.2% and initial sulfur content of 1.5%
is pulverized in the presence of 400 grams of water to a
5 200 mesh size using a Hall mill grinding unit. The coal is
transferred to a mixing vessel. unto this vessel containing
the coal is also introduced 0.05 grams of corn oil, 2.0
grams of #2 fuel oil, lucks. of a 5.0% solution of hydrogen
peroxide in water and 2.0cc. of a cupric nitrate Swahili
10 lion in waxer. The mixture is stirred and heated to about
30 DC for about 2 minutes. The resultant mixture is sprayed
into a vessel containing clean water and a frothing ensues.
The coal, in the coal froth phase, is skimmed from the water
surface. The water phase containing large amounts of hydra-
15 Philip ash and sulfur is discarded.
The cleaning procedure is repeated two further times using clean water and skimming the frothed coal from
the water surface. The particulate coal is then dried to a
water content of buzzed on the weight of dry coal,
20 using a laboratory Buchner funnel. The ash content of the
final particulate product is reduced to 1.5% and the sulfur
content is reduced to 0.8%.
-31~
'1 23~.~;k.3
1 EXAMPLE 2
-
The procedure of Example 1 is repeated using
equivalent amounts of (a) coyer gasoline; (b) oleic acid;
and (c) tall oil, each substituted for the corn oil. A
5 cleaned coal particulate product it produced having an ash
content of about I and a moisture content of about 15~,
based on the weight of the dry coal.
I
-32-
I
EXAMPLE 3
__
The process of Example l is repeated using (a)
Captaining seam coal; (b) Illinois #6 seam coal; and (c1
lower E`reeport seam coal in lieu of the Pittsburgh seam
5 coal. A cleaned coal product having an ash content of
about 3.0% and a moisture concentration of 15~, based on
the weight of the dry koalas provided.
Jo
-33~
I
EXAMPLE 4
200 grams, Illinois #6 coal reduced to about 1/4"
size lumps and having an ash content of 19.9~, is crushed
5 to a particle size of about 28 mesh and then pulverized to
200 mesh in a laboratory ball mill in the presence of water
to form a coal-aqueous liquid slurry. The liquid phase of
the slurry contains about 65% water based on the total
weight of the slurry.
50 my. tall oil, 10 gyms. of fuel oil, 250 milligrams
sodium pryrophosphate, 100 milligrams of cupric nitrate and
1.0 gyms. HOWE to% solution in water) are added to the above
coal-aqueous slurry at about 30-40C. The hydrophobic, sun-
face treated coal phase which ensues is recovered by removing
15 it from the surface of the aqueous phase on which it floats.
The aqueous phase contains the hydrophilic ash and is disk
carded.
Subsequent to several re-dispersions in clean soft
water, containing sodium pyrophosphate, at about 3CC, the
20 surface treated coal is recovered. After filtering through
a Buchner funnel, the water content of the coal is about
15%. (Conventionally processed coal, i.e., without chemical
surface treatment, customarily retains from about 20-50%
water when ground to the same mesh size).
The recovered, mechanically dried, treated,
beneficiated coal is admixed with 160 grams of fuel
oil and an additional 5.0 gyms. of tall oil is added
thereto. after thorough admixing at 85C, caustic
soda, equivalent to the acid value of the admixture,
30 is added thereto and further admixed therewith.
After standing for several months, no settling
of the coal-liquid fuel mixture is observed.
~39-
~,23~
1 EXAMPLE 5
The process of Example 4 is repeated, except that
gram equivalent amounts of the following polymerizable moo-
5 mews are substituted for the tall oil used in Example 4:
(a) coyer gasoline and (b) oleic acid.
The surface of the pulverized coal is similarly
altered to result in strongly hydrophobic coal particles
which are processed similar to Example 4. In each case,
10 the same amount of tall oil is admixed with the recovered
beneficiated coal, after drying. Acidity is neutralized with
caustic and similar coal-oil liquid suspensions are prepared,
which all exhibit thixotropic quality depending upon the metal
ion selected to displace the sodium ion of the sodium hydroxide
15 originally added. No settling is observed over several weeks
observation, independent of the monomer used in the surface
treatment reaction.
-35-
I
1 EXAMPLE 6
The process of Example 4 is repeated except that
2 grams ox bouncily peroxide are used in place of the hydrogen
peroxide. Moreover, 2 grams of Triton-X-100 surfactant
5 and 25 grams of sodium pyrophosphate are present in the
original slurry water. The ash in the resulting aqueous
phase is filtered out after treating with lime. The ash con-
tent of the treated coal is reduced from about 19.9% to about
4.7~ after five separate washings, wherein the water also
10 contains Triton-X-100 and sodium pyrophosphate. The tall
oil used in the surface treatment reaction and the tall oil
employed in the formation of the stable coal-oil
mixture, is neutralized first with caustic soda and sub-
sequently treated with an equivalent amount of calcium
15 hydroxide. The viscosity of the coal-oil mixture is of a
thixotropic gel-like nature, indicating no settling is to be
expected upon extended standing.
Jo
-36-
1 EXAMPLE 7
.
235 grams of beneficiated coal having a 15%
moisture content prepared in accordance with Example
5 1 is placed in a vessel in which a stabilized coal-fuel
oil mixture is formed by the addition to said coal of
200 gyms of #2 fuel oil, 6.0 gyms. tall oil, 1.0 gyms. of
a 0.1% solution of HOWE ( or bouncily peroxide) in water
(Tulane), and 2.0 gyms. of a 0.1% aqueous solution of
10 cupric nitrate. The mixture is stirred for about 1.0
minute at about 85C. 1.5 gyms. of sodium hydroxide is
added thereto and stirred for 5.0 minutes at about 65~C.
The resultant coal-oil mixture is a stabilized gel and
remains so indefinitely.
-37-
3.~16~
1 Obviously, other modifications and variations of
the present invention are possible in the light of the above
teachings. It is, therefore, to be understood that changes
may be made in the particular embodiments of this invention
swish are within the full intended scope of the invention
as defined by the appended claims.
