49 Claims, No Drawings
Primary Examiner-Carl Dees
Attorney, Agent, or Firm~Sheridan, Ross, Fields &
McIntosh
In a process for improving coal containing elemental
sulfur wherein the coal is treated with a metal containing
compound in order to enhance the magnetic susceptibility
of various impurities contained within the coal
thereby permitting their removal by magnetic separation,
the improvement comprising removing at least a
portion of the elemental sulfur prior to performing the
magnetic susceptibility enhancement treatment.
United States Patent [19]
Kindig et ale
[54] PROCESS FOR IMPROVING COAL
[75] Inventors: James K. Kindig, Arvada; Ronald L.
Turner, Golden, both of Colo.
[73] Assignee: Hazen Research, Inc., Golden, Colo.
[21] Appl. No.: 764,390
[22] Filed: Jan. 31, 1977
[51] Int. Cl.2 CI0L 9/10; ClOB 57/00
[52] U.S. Cl 44/1 R; 201/17
[58] Field of Search 44/1R; 201/17
[56] References Cited
U.S. PATENT DOCUMENTS
3,938,966 2/1976 Kindig et aI. 44/1 R
4,052,170 10/1977 Yan 44/1 R
[57]
[11]
[45]
ABSTRACT
4,119,410
Oct. 10, 1978
4,119,410
DESCRIPTION OF THE PREFERRED
EMBODIMENT
The process ofthe present invention can be applied to
coals of universal origin, as long as the coal contains one
or more impurities receptive to the metal containing
compound treatment, and contains sufficient elemental
SUMMARY OF THE INVENTION
The process of the present invention entails improving
coal containing elemental sulfur and various impurities
by initially removing at least a portion of the elemental
sulfur, followed by treating the coal with a metal
containing compound under conditions such as to enhance
the magnetic susceptibility of one or more impurities
contained in the raw coal, thereby permitting the
removal of these impurities by magnetic means. The
pretreatment for removing elemental sulfur may be
performed by any suitable means, including, for example,
heat treatment, steam treatment, solvent extraction,
and chemical reaction.
2
other impurity. Coal particles alone are slightly diamagnetic
while pyrite and many other mineral impurities
are weakly paramagnetic; however, their paramagnetism
has not been sufficient to economically effect a
5 separation from coal. However, effective beneficiation
of coals can be made if the magnetic susceptibility of
pyrite or other impurities is increased. For pyrite it has
been estimated that a sufficient increase in susceptibility
can be achieved by converting less than 0.1 percent of
10 pyrite in pyritic coal into ferromagnetic compounds of
iron ("Magnetic Separation of Pyrite from Coals," Bureau
of Mines Report ofInvestigations 7181, p.l).
In discussing the use of heat to enhance the paramagnetism
of pyrite it is stated in the above report (p.l) that
ferromagnetic compounds of iron are not formed in
significant quantities at temperatures below 400° C., and
that such conversion occurs in sufficient quantities to
effect beneficiation only at temperatures greater than
500° C. As this is above the decomposition temperature
of coal, the use of heat to enhance the magnetic susceptibility
of impurities does not appear feasible. Further,
other methods for enhancing the paramagnetism of
pyrite to permit its separation from coal have not been
encouraging.
U.S. Pat. No. 3,938,966 discloses a process for improving
coal whereil1 the raw coal is reacted with substantially
undecomposed iron carbonyl which alters the
magnetic susceptibility of certain impurity components
contained in the raw coal, thereby permitting their
removal by low-intensity magnetic separators. This
process represents a noteworthy advance in the art, as
treating coal in accordance with this process may substantially
remove impurities such as pyrite, a primary
contributor to sulfur dioxide pollution problems. The
process of this patent, however, does not appear to
possess universal applicability with an equal degree of
success in that while many coals are substantially enhanced
by this treatment, certain other coals are not as
receptive. It has been discovered by the inventors of the
present application that pretreating coal to remove at
least a portion of elemental sulfur present under various
conditions as hereinafter presented substantially enhances
the effectiveness of the process of this patent.
The process of the present invention therefore constitutes,
in part, an improvement of the process described
in U.S. Pat. No. 3,938,966, in accordance with the discussion
presented hereinafter.
1
PROCESS FOR IMPROVING COAL
BACKGROUND OF THE INVENTION
1. Field of the Invention
The process of the present invention relates to the
improvement of the properties of coal, and is classified
generally in the class relating to fuels and igniting devices.
2. The Prior Art
With the present world-wide emphasis on the energy
crisis and the rapidly diminishing sources of oil, increased
attention by both government and private organizations
is being given to coal as a source of energy,
especially for the generation of electricity. This country 15
has vast resources of coal for development as other
sources of energy diminish.
Depending upon their origin, coals contain varying
amounts of iron disulfide (iron disulfide is hereinafter
referred to as pyrite· whether crystallized as pyrite or 20
marcasite) from which sulfur dioxide is formed as a
combustion product when coal is burned. This is a tremendous
disadvantage to the use of coal as an energy
source, particularly in view of the current emphasis on
pollution controls as illustrated by present federal emis- 25
sion control standards for sulfur dioxide. Illustrating the
enormity of the sulfur dioxide emission problem is the
fact that large transportation expenses are incurred by
coal users in transporting Western and European coal of
relatively low sulfur content long distances to supplant 30
available high sulfur-containing coals in order to comply
with sulfur dioxide emission standards. At this time
there are no effective means available which are commercially
feasible for absorbing the large amounts of
sulfur dioxide emitted by the combustion of coal to 35
produce heat and electricity. One solution to the problem
is to separate the sulfur-bearing pyrite from the coal
before it is burned.
Coals also contain, depending upon their origin, various
amounts and kinds of minerals which form ash 40
when the coal is burned; The ash also is a disadvantage
to the use of coal as an energy source, since it contributes
no energy value during combustion. The ash causes
a dilution of the calorific value of the coal, and causes a
waste disposal problem and a potential air pollution 45
problem.
The problem of separating pyrite and/or other impurities
from raw coal is not new and a number ofmethods
have been extensively tested over the years. Among
these are methods which employ the difference in spe- 50
cific gravity between coal particles and the impurity
particles or differences in their surface, electrostatic,
chemical, or magnetic properties. For various reasons
difficulties are encountered in making an efficient separation
ofpyrite or other impurities from coal which has 55
been ground fine enough to substantially liberate impurity
particles from coal particles. In water systems this
difficulty is related to the slow settling rate of fine particles,
and in air systems to the large difference in specific
gravity between air and the particles. However, for 60
magnetic separations the magnetic attraction force acting
on small magnetic particles is many times greater
than the opposing force, which is usually a hydraulic
drag and/or gravity force.
For the separation of pyrite or other impurities from 65
raw coal the success of a magnetic process is dependent
upon some effective treatment·· process for selectively
enhancing the magnetic susceptibility of the pyrite or
4,119,410
4
stances, serve as chemical reactants in removing elemental
sulfur.
When these additives are employed, it is preferable
that they be employed in an amount of at least 2, more
preferably at least about 12, and most preferably at least
about 120 cubic meters per hour per metric ton of coal
being processed.
A particularly preferred additive is steam. Heat pretreatment
with steam is preferably conducted within a
temperature range of from about 100· C. to about 3000
C., more preferably from about 1500 C. to about 250·
C., and most preferably from about 1750 C. to about
225 0 C. Preferably the pretreatment should be conducted
for at least about 0.25 hours, more preferably for
at least about 0.5 hours, and most preferably for at least
1 hour. The amount of water preferably ranges from
about 2% to about 50%, more preferably from about
5% to about 30%, and mostpreferably from about 10%
to about 25%, based on the weight of the coal being
treated.
It is generally preferred to maintain the heat pretreatment
temperature at least slightly above the temperature
of the magnetic enhancement reaction. This is not
an imperative requirement; however, improved results
are generally accomplished. The pretreating by heating
the coal volatilizes the elemental sulfur. If the magnetic
enhancement reaction is conducted at a temperature in
excess of the pretreatment temperature, it is possible
that additional volatile components could somewhat
detrimentally affect the magnetic enhancement reaction.
One particularly preferred technique for performing
the heat pretreatment process embodiment of the iilven-
35 tion is to conduct the process while the coal is in a
fluidized state. Conventional fluidized bed apparati and
processes are suitable. This fluidized treatment facilitates
thorough pretreatment of all of the coal.
Alternatively, the coal can be pretreated with a solvent
or a combination of solvents to effect elemental
sulfur removal. Examples of suitable solvents include
carbon tetrachloride, toluene, acetone, ethyl alcohol,
methyl alcohol, ether, liquid ammonia, and other compounds
suitable to dissolve elemental sulfur. Preferred
solvents include carbon tetrachloride, petroleum ether
and hot toluene followed by a warm acetone rinse.
The amount of a particular solvent used will be dependent
on the degree of solubility the elemental sulfur
exhibits in the solvent at the treatment temperature.
Generally, it is preferable that the solvent be employed
in an amount of at least about 500, more preferably at
least about 1,000, and most preferably at least about
2,000 milliliters per kilogram of coal.
The elemental sulfur removal step need not be immediately
followed by the magnetic enhancement reaction.
Hence, the coal may be permitted to be stored for
an indefinite period of time prior to conducting the
magnetic susceptibility enhancement reaction.
The basic process employs a metal treatment in order
to enhance the magnetic susceptibility of an impurity.
By selectively enhancing this property of the impurity,
while not substantially affecting the coal itself, a magnetic
separation may be conventionally accomplished to
remove the impurity from the coal. The coal is therefore
left in a more pure state, rendering it more suitable
for combustion.
"Enhancing the magnetic susceptibility" of a particle
or an impurity as used herein is intended to be defined in
3
sulfur such that the sulfur interferes with the interreaction
of the metal containing compound and the coal.
Generally, the elemental sulfur concentration in raw
coal is at least about 10 parts per million, and often this
concentration exceeds several hundred parts per n:.il- 5
lion.
Concentrations of elemental sulfur in excess of 10
parts per million are such as to hinder the magnetic
susceptibility enhancement reaction. Higher concentrations
of elemental sulfur present greater hindrances. It is 10
therefore to be understood that any removal of elemental
sulfur prior to performing the magnetic susceptibility
enhancement treatment improves this treatment.
Preferably the concentration of elemental sulfur following
treatment for its removal will be less than about 200 15
parts per million, more preferably less than about 50
parts per million, and most preferably less than about 10
parts per million, based on the total weight of the raw
coal being treated.
Essentially any process for removing elemental sulfur 20
from raw coal can be utilized as the pretreatment
means, and examples of suitable processes include heat
treatment, steam treatment, solvent extraction and
chemical reaction.
The heat pretreatment essentially comprises heating 25
the coal in order to remove elemental sulfur, thereby
rendering the coal and impurities more receptive to the
magnetic enhancement reaction. The temperature and
time of heating are interrelated, and essentially higher
temperatures require less time. It is essentially preferred 30
that the temperature and time be selected in accordance
with the following equation:
wherein 0 is time in hours and T is temperature in
degrees Celsius, and wherein K is preferably at least
about 0.5, more preferably at least about 5, and most 40
preferably at least about 25. The equation is not accurate
with respect to temperatures less than about 950 C.
Some improvement may be realized at temperatures
below 950 C., but the time requirement would be inordinate.
Under circumstances when the temperature ex- 45
ceeds the combustion temperature of coal the time must
be very short in order to prevent combustion, and preferably
not substantially exceeding the value of the equation.
Additionally, other precautions known to the art
should be complied with. 50
While operating within the above time-temperature
relationship, it is generally preferred that the pretreatment
essentially comprise heating the coal to a temperature
of at least about 1000 C., and more preferably to a
temperature of at least about 1500 C., and most prefera- 55
bly to a temperature of at least about 170· C. This heat
pretreatment is preferably for at least about 1 hour, and
more preferably for at least about 2 hours, with respect
to temperatures less than the coal combustion temperature.
60
The heat pretreatment step may be conducted in the
presence of one or more gaseous additives, and this is
preferable under many circumstances. Examples of
suitable gaseous additives include nitrogen, steam, carbon
monoxide, carbon dioxide, ammonia, methane, air, 65
ethane, propane, butane, and other hydrocarbon compounds
in the gaseous state at the pretreatment temperature.
Some of the additives, under certain circum45
6
coal impurities, as long as the compound is adaptable so
as to bring the iron in the compound into contact with
the impurity under conditions such as to cause an alteration
of at least a portion of the surface of the impurity.
Organic iron containing compounds capable of exerting
sufficient vapor pressure (with iron as a component in
the vapor) so as to bring the iron into contact with the
impurity at the reaction temperature are suitable, as
well as other organic iron containing compounds which
can. be dissolved and/or "dusted" and brought into
contact with the impurity. .
Preferred compounds within the vapor pressure
group are those which exert a vapor pressure with iron
as a component in the vapor of at least about 10 millime-
15 ters of mercury, more preferably at least about 25 millimeters
of mercury, and most preferably at least about 50
millimeters of mercury at the reaction temperature.
Examples of groupings which fall within this vapor
pressure definition include ferrocene and its derivatives
and j3-diketone compounds of iron. Specific examples
include ferrocene, dimethyl ferrocenedioate, I, I'-ferrocenedicarboxylic
acid, ferric acetylacetonate, and
ferrous acetylacetonate.
Other organic compounds which may be utilized to
enhance the magnetic susceptibility include those
which may be dissolved and brought into contact with
the impurities. These compounds must have sufficient
solubility so as to provide sufficient metal to contact the
surface of the impurity. Preferably the solubility is at
least about 10 grams per liter, and most preferably at
least about 50 grams per liter at the injection temperature.
The solvent must, of course, possess the capability
of dissolving the organic compounds within the above
set forth concentrations, and preferably not create side
reaction problems tending to detract from the effectiveness
of the process. Suitable solvents include, for example,
acetone, petroleum ether, naphtha, hexane, and
benzene. This is, of course, dependent upon the particular
metal compound being employed.
A grouping which falls within this solution definition
includes the carboxylic acid salts of iron; and specific
examples include iron octoate, iron naphthenate and
iron stearate.
Various inorganic compounds are also capable of
producing an enhanced magnetic susceptibility. Preferred
inorganic compounds include metal carbonyls,
including, for example, iron, nickel, cobalt, molybdenum,
tungsten, and chromium carbonyls and derivatives
of these compounds. Iron carbonyl is a preferred carbonyl
for imparting this magnetic susceptibility, particularly
iron pentacarbonyl, iron dodecacarbonyl, and
iron nonacarbonyl.
The most preferred metal containing compound capable
of enhancing the magnetic susceptibility is iron
pentacarbonyl. The process is applied by contacting the
raw coal which is liberated from pyrite or other impurities
with iron carbonyl under conditions such that there
is an insufficient dissociation of carbonyl into metal and
carbon monoxide to cause substantial deposition of
metal on the coal particles. These conditions are determined
by the temperature, the type of carbonyl, pressure,
gas composition, etc. Ordinarily, the carbonyl gas
is heated to a temperature just below its decomposition
temperature under the reaction conditions. Various
types of aVllllable equipment can be used for contacting
the iron carbonyl and coal, such as, a rotating kiln used
as the reaction vessel with iron carbonyl vapors carried
4,119,410
M + 3FeP3 --+ MO + 2FeP4
In similar fashion,' U.S. Pat. No. 3,938,966 and the
reaction mechanisms illustrated therein with respect to
pyrite and iron pentacarbonyl present viable techniques
for enhancing the magnetic susceptibilities of impuri- 50
ties.
Other mechanisms undoubtedly also contribute to the
enhancing of the magnetic susceptibility, and again this
is prinqipally determined by the particular metal containing
compound or compounds employed and the 55
reaction conditions. It is to be understood that in view
of the disclosures herein presented, the selection of a
given metal compound, along with the most desirable
reaction conditions to be employed with the given compound,
cannot be itemized for each and every com- 60
pound due to the number of variables involved. However,
the proper selection will be apparent to one skilled
in the art with but a minimal amount of experimentation,
and it is sufficient to note that the improvement of
the invention herein set forth relates to all of these com- 65
pounds.
Many organic iron containing compounds possess the
capability of enhancing the magnetic susceptibility of
Similarly, ash components, such as Fe203' may react 40
with, a metal to form a more strongly magnetic compound,
as for example, in accordance .with the following
reaction:
5
accordance with the following discussion. Every compound
of any type has a specifically defined magnetic
susceptibility, which refers to the overall attraction of
the compound to a magnetic force. An alteration of the
surface characteristics will alter the magnetic suscepti- 5
bility. The metal treatment of the basic process alters
the surface characteristics of an impurity in order to
enhance the magnetic susceptibility ofthe impurity. It is
to be understood that the magnetic susceptibility of the
impurity is not actually 'changed, but the particle itself is 10
changed, at least at its surface, resulting in a particle
possessing a greater magnetic susceptibility than the
original impurity. For convenience of discussion, this
alteration is termed herein as "enhancing the magnetic
susceptibility" of the particle or impurity itself.
The impurities with which the process of the present
invention may be utilized include those impurities
which react with one or more of the metal compounds
hereinafter described to form a product possessing an
enhanced magnetic susceptibility. Examples of such 20
impurities include pyrite; ash-forming minerals, such as
clays and shales; and various sulfates, for example, calcium
sulfate and iron sulfate. For purposes of illustra-
. tion the discussion hereinafter often refers to pyrite, but
it is to be understood that other suitable impurities may 25
be affected in similar fashion.
Numerous metal containing compounds are suitable
to impart this magnetic susceptibility. A number of
different mechanisms are believed to be involved in
what is termed herein as the magnetic susceptibility 30
enhancement "treatment" and/or "reaction," depending
upon the metal containing compound or compounds
and the reaction conditions employed. Some metal containing
compounds aff~ct the pyrite by combining with
some of the pyrite sulfur to yield an iron sulfide more 35
magnetic than pyrite. The following reaction exemplifies
this mechanism:
Feed Coal Clean Coal
Sample Ash Pyritic S S' Yield Ash Pyritic S
Number (Wt.%) (Wt.%) (ppm) (Wt.%) (Wt.%) (Wt.%)
I 33.0 2.19 156 86.8 28.S 2.44
2 33.0 2.19 <I 79.S 20.4 1.52
EXAMPLE 2
.A Low:r.Freeport bituminous coal from Pennsylvamao
contammg 156 parts per million elemental sulfur
was sized to a minus 14~mesh. Two samples were
treated with 2 kilograms per metric ton iron pentacarbonyl
at a temperature of about 190°-195° C. Sample I
was not pretreated for elemental sulfur removal, while
Sample 2 was treated with hot toluene and rinsed with
warm acetone prior to the carbonyl treatment. The
comparative results are presented in Table 2.
Table 2
1.09
0.90
0.85
0.83
0.93
10.8
9.3
9.4
9.0
Pyritic
Ash, Sulfur,
% %
10.0
Clean Coal Analysis
86.S
84.6
84.0
85.9
84.0
Yield
Wt.%
8
Table I
Run Sulfur Removal S'
No. Technique (ppm)
I None 25
2 Sulfur removed with <I
toluene & acetone
Sulfur removed with <I
petroleum ether
4 Sulfur removed with <I
steam, 95 kg/metric
ton, 190-195' C
5 Sulfur removed with <I
steam, 95 kg/metric
ton, 250-255' C
4,119,410
7
into contact with the tumbling contents of the kiln by a
gas such as nitrogen.
When carbonyl is used as the magnetic susceptibility
enhancement reactant, the process must be carried out
at a ten;t~erature below the temperature of major de- 5
composItIOn of the carbonyl under the reaction conditions
so that there is opportunity for the iron of the
carbonyl to chemically react with the impurity particles.
If the temperature is allowed to rise above the
decomposition temperature, the selectivity of the pro- 10
cess of enhancing the magnetic susceptibility of one or
more impurities without affecting the coal is impaired.
Most preferably the iron pentacarbonyl treatment is
performed by contacting the coal with the carbonyl for
a time of from about one-half to about four hours at a 15
temperature of from about 150° C. to about 200° C. and
a carbonyl concentration of from about 2 to about 16
kilograms per metric ton of coal.
For efficient separations of pyrite from coal, the coal
should be crushed to such fineness that pyrite particles 20
are free, or nearly free, from the coal particles. The
required fineness depends upon the size distribution of
the pyrite in the coal. A thorough treatment of the
subject for power plant coals is given in the article
entitled "Pyrite Size Distribution and Coal-Pyrite Parti- 25
cle Association in Steam Coals," Bureau of Mines Re~
ort o~ Invest~gation 7231. The requirement for pyrite
lIberatIOn applIes to all types of physical separations and
so is not a disadvantage of this invention. Additionally,
present technology for coal-fired power plants gener- 30
ally requires pulverizing the coal to 60-90 percent
minus 200 mesh before burning.
EXAMPLE I
EXAMPLES
In each of the examples, the coal sample was sepa- 35
rated in a magnetic separator following the described
treatment to give a non-magnetic clean coal fraction
and a magnetic refuse fraction. The analytical procedure
used to determine elemental sulfur was adapted
from the method of Bartlett and Skoog, Colorimetric 40
Determination of Elemental Sulfur in Hydrocarbons,
Analytical Chemistry, Volume 26, Number 6, June,
1954.
45
Pittsburgh coal containing 25 parts per million elemental
sulfur, 17.9 weight percent ash and 1.67 weight
percent pyritic sulfur was sized to 14 mesh X 0 and
treated with 8 kilograms per metric ton of iron pentacarbonyl
at a temperature of about 190°-195° C. for 60 50
minutes. A magnetic separation was performed following
the carbonyl treatment. Run I was not initially
treated for elemental sulfur removal, and Runs 2-5 were
treated by the processes described to remove substantially
all of the elemental sulfur prior to the carbonyl 55
reaction. Table I provides for each of these Runs the
clean coal yield based on weight percent of the raw coal
feed, and the clean coal weight percentage of ash and
pyritic sulfur.
EXAMPLE 3
For each ofthe runs presented in Table 3, 75 grams of
raw coal, a lower Freeport bituminous coal from Pennsylvania,
was sized to 14 mesh by zero and treated for
60 minutes with steam at 200° C. at a rate of 0.46 grams
per minute. The initial elemental sulfur concentration
was 178 parts per million, and following the steam treatments
the concentration in each of the runs was less
than 1 part per million. In each of the runs the steam
was injected with the designated additive gases set forth
in Table 3. The carbonyl treatment for all tests was
conducted at a temperature of 170° C. for one hour with
16 kilograms of iron pentacarbonyl per metric ton of
coal.
EXAMPLE 4
An Illinois coal containing 105 parts per million elemental
sulfur was sized to 14 X 150-mesh. Three samples
were treated with 7.5 kilograms per metric ton iron
pentacarbonyl at a temperature of about 175°-195° C.
for 60 minutes. Sample I was not pretreated for elemental
sulfur removal, whereas, Samples 2 and 3 were both
treated with hot toluene and rinsed with warm acetone
prior to the iron carbonyl treatment. The comparative
results are show~ in Table 4. .
TABLE 3
No
Run Number Pretreatment 2 4 6 7
Conditions:
Gas Nz CO Nz COz Nz Air Nz NHJ Nz SOz Nz Butane Nz
Flow, mllmin 150 50 100 27 123 150 150 50 100 50 100 50 100
Time, min 60 60 60 30 30 60 60 60
Yield, Weight %
Clean coal 56.9 69.6 77.4 72.3 73.9 89.8 61.3 61.8
9
4,119,410
10
TABLE 3-continued
No
Run Number Pretreatment I 2 3 4 5 6 7
Refuse 30.4 22.6 27.7 26.1 10.2 38.7 38.2
Ash,%
Clean coal 22.5 13.3 17.7 15.9 15.3 25.1 11.9 9.6
Refuse 66.8 70.6 68.3 70.2 63.1 56.4 60.9
Pyritic Sulfur,%
Clean coal 1.85 0.40 0.52 0.47 0.42 1.00 0.57 0.31
Refuse 4.17 4.48 4.22 4.13 7.15 2.95 3.24
The feed coal contained 29.9% ash and 1.63% pyritic sulfur.
EXAMPLE 7
A 75 gram sample of Illinois #6 coal, sized 14 X
150-mesh, was placed in a rotary reactor. 2.5 kilograms
per metric ton of elemental sulfur was sublimed and
allowed to react with the coal for 30 minutes at about
200· C. with no gas flow. A corresponding 75 gram
sample received no pretreatment. Each sample was then
treated with 7.5 kilograms per metric ton of iron pentacarbonyl
at 190·-195' C. for 30 minutes. Table 7 provides
the relevant feed coal and clean coal analyses for
each sample.
Table 6-continued
Sample S' Yield, Ash,
Number Pretreatment (ppm) WI. % %
Pyritic
S,%
Clean Coal Analysis
74.8 27.0 4.52
64.0 15.5 3.90
Yield, Ash, Pyritic
Wt. % % S, %
4.42
3.89
Table 7
27.1
30.4
Feed Analysis
Ash, Pyritic
% S,%
ton, N2 1700 mll
min at 130-140' C
for 15 minutes
15
Sample
35 Sulfur Treated
No Pretreatment
EXAMPLE 5
EXAMPLE 6
Table 4
Clean Coal Analysis
Temperature of
Sample S' Carbonyl Yield Ash Pyritic
Number (ppm) Treatment (Wt.%) (Wt.%) S, (Wt.%)
1 105 190-195' C 69.6 20.9 3.68
2 <1 175-180' C 74.2 15.2 3.04
3 <1 190-195' C 66.6 12.2 2.96
Feed
Analysis 25.5 3.91
Samples 1-12 presented in Table 5 ofLower Freeport
Coal containing 156 parts per million elemental sulfur 25
were pretreated with heat (including steam, where indicated),
under the conditions given in Table 5. After the
pretreatment each sample (75 grams) waS treated with
16 kilograms per metric ton of iron pentacarbonyl at
170· C. for one hour with a nitrogen purge of 250 milli- 30
liters per minute during the heat up and cool down.
Sample 13 was similarly treated with iron pentacarbonyl,
but was not pretreated for the removal of elemental
sulfur.
Lower Freeport coal sized to 14 X O-mesh was
treated for one hour with 16 kilograms per metric ton of
iron pentacarbonyl at a temperature of about 170' C.
Sample 1 was not pretreated for the removal of elemen- 40
tal sulfur, whereas, Samples 2 and 3 were treated at the
conditions specified in Table 6 to remove a portion of
elemental sulfur as indicated. The results are shown in
Table 6, as is an analysis of the feed coal prior to any
type of treatment. 45
TABLE 5
What is claimed is:
1. In a process for improving coal containing impurities
and elemental sulfur wherein the coal is treated with
a metal containing compound in order to enhance the
magnetic susceptibility of one or more of the impurities
susceptible to the metal containing compound treatment,
thereby permitting the removal of these impurities
by magnetic separation, the improvement compris-
Steam
Sample Water, Temp, Time, Cone, Elemental Yield, Ash, Pyritic
Number mllmin 'C min %Atmos. S,ppm Wt% % S,%
1 0 190 10 0 9 54.5 11.2 1.13
2 0.95 190 10 25 8 52.6 13.1 1.45
3 3.35 190 10 89 7 55.8 10.6 0.84
4 0 260 10 0 3 71.4 13.5 1.23
5 0.95 260 10 28 5 69.7 13.9 1.02
6 3.35 260 10 98 <1 81.2 18.7 0.84
7 0 190 30 0 2 73.9 15.7 0.59
8 0.95 190 30 25 2 68.3 12.0 0.53
9 3.35 190 30 89 2 68.1 11.5 0.37
10 0 260 30 0 3 65.6 18.6 1.27
11 0.95 260 30 28 <I 75.3 14.8 0.77
12 3.35 260 30 98 <1 78.6 16.4 0.58
13 156 56.9 22.5 1.85
Raw Coal 156 28.1 1.76
Table 6 ing:
Sample S' Yield, Ash, Pyritic removing at least a portion of the elemental sulfur
Number Pretreatment (ppm) WI. % % S,% prior to performing the magnetic enhancement
Feed 242 100.0 28.1 1.76 65 treatment.
1 None 242 56.9 22.5 1.85 2. The process of claim 1 wherein the means for re-
2 Heated in air at 51 59.5 17.3 0.98 137' C, 16 hours moving elemental sulfur comprises heating the coal to
Steam 19 kg/metric 160 78.1 21.5 1.58 at least a temperature for at least a period of time suffi4,119,410
12
20. The process of claim 19 wherein the iron compound
is a member selected from the group consisting
of ferrous chloride and ferric chloride.
21. The process of claim 19 wherein the iron com5
pound is an organic iron containing compound.
22. The process of claim 21 wherein the organic iron
containing 'compound is capable of exerting sufficient
vapor pressure, with iron as a component in the vapor,
so as to bring the iron into contact with the impurity at
the reaction temperature.
23. The process of claim 22 wherein the vapor pressure
of the organic iron containing compound is at least
about 10 millimeters of mercury at the reaction temperature.
24. The process of claim 21 wherein said organic iron
containing compound is selected from the group consisting
of ferrocene, ferrocene derivatives, and ,B-diketone
compounds of iron.
25. The process of claim 19 wherein the iron compound
is selected from the group consisting of ferrocene,
dimethyl ferrocenedioate, l,l'-ferrocenedicarboxylic
acid, ferric benzoylacetonate, ferric acetylacetonate,
ferrous acetylacetonate, ferric octoate, ahydroxyethyl
ferrocene, and ferrous formate.
26. The process of claim 19 wherein the iron compound
is an ester of a ferrocene carboxylic acid derivative.
27. The process of claim 26 wherein the ester of a
ferrocene carboxylic acid derivative is dimethyl ferrocenedioate.
28. The process of claim 19 wherein the iron compound
is a simple iron salt of a monobasic or dibasic
organic acid.
29. The process of claim 28 wherein the ·iron salt of a
monobasic organic acid is iron formate.
30. The process of claim 19 wherein the iron compound
is a ,B-diketone.
31. The process of claim 30 wherein the ,B-diketone
iron compound is selected from the group consisting of
ferric benzoylacetonate, ferric acetylacetonate and ferrous
acetylacetonate.
32. The process of claim 19 wherein the iron compound
is an iron salt of a carboxylic acid.
33. The process of claim 32 wherein the iron salt of a
carboxylic acid is a ferric octoate.
34. The process of claim 19 wherein the iron compound
is a hydroxyalkyl derivative of ferrocene.
35. The process of claim 34 wherein the hydroxyalkyl
derivative of ferrocene is a a-hydroxyethyl ferrocene.
36. A process for improving coal containing elemental
sulfur and impurities comprising:
(a) subjecting the coal to a means for removing at
least a portion of the elemental sulfur present;
(b) thereafter contacting the coal with iron carbonyl
under reaction conditions such as to increase the
magnetic susceptibility of one or more impurities
contained within the coal;
thereby permitting the removal of the altered impurities
by magnetic separation.
37. The process of claim 36 wherein the means for
removing at least a portion of the elemental sulfur present
in the coal comprises pretreating the coal by heating
it to at least a temperature for at least a period of time
sufficient to essentially meet or exceed a time and temperature
relationship expressed as:
11
cient to essentially meet or exceed a time and temperature
relationship expressed as:
wherein D is time in hours and T is temperature in
degrees Celsius, and is not less than about 95° C., and
wherein K is preferably at least about 0.5. 10
3. The process of claim 2 wherein K is preferably at
least about 5.0.
4. The process of claim 2 wherein the coal is heated to
a temperature of at least about 100° C. for at least about
one hour. 15
5. The process of claim 2 wherein the heat pretreatment
step is conducted in the presence of a member
selected from the group consisting of nitrogen, steam,
carbon monoxide, carbon dioxide, ammonia, methane, 20
air, ethane, propane, butane, and other hydrocarbon
compounds in the gaseous state at the pretreatment
temperature.
6. The process of claim 1 wherein the means for rem?
ving elemental sulfur comprises pretreating the coal 25
with steam.
7. The process of claim 6 wherein the steam pretreatment
means is conducted within a temperature range of
from about 100° C. to about 300° C. for at least about
0.25 hours with from about 2% to about 50% water 30
based on the weight of the coal being treated.
8. The process of claim 1 wherein the means for removing
elemental sulfur comprises solvent extraction.
9. The process of claim 8 wherein the solvent is selected
from the group consisting of carbon tetrachlo- 35
ride, toluene, acetone, methyl alcohol, ethyl alcohol,
ether, and liquid ammonia.
10. The process of claim 1 wherein the elemental
sulfur concentration ofthe coal following the elemental
sulfur removal step is less than about 200 parts per mil- 40
lion.
11. The process of claim 1 wherein the elemental
sulfur concentration of the coal following the elemental
sulfur removal step is less than about 50 parts per million.
45
12. The process of claim 1 wherein the elemental
sulfur concentration of the coal following the elemental
sulfur removal step is less than about 10 parts per million.
13. The process of claim 1 wherein the impurities 50
enhanced comprise a member selected from the group
consisting of pyrite and ash-forming minerals.
14. The process of claim 13 wherein the impurities
enhanced comprise pyrite.
15. The process of claim 13 wherein the impurities 55
enhanced comprise ash forming minerals.
16. The process of claim 1 wherein the metal containing
compound is a substantially undecomposed carbonyl
selected from the group consisting of iron carbonyl,
nickel carbonyl, cobalt carbonyl, molybdenum 60
carbonyl, tungsten carbonyl, chromium carbonyl, and
derivatives of these carbonyls.
17. The process of claim 16 wherein the metal containing
compound consists essentially of iron carbonyl.
18. The process of claim 17 wherein the iron carbonyl 65
consists essentially of iron pentacarbonyl.
19. The process of claim 1 wherein the metal containing
compound is an iron compound.
5
14
42. The process of claim 41 wherein the solvent is a
member selected from the group consisting of carbon
tetrachloride, toluene, acetone, ethyl alcohol, ether, and
liquid ammonia.
43. The process of claim 41 wherein the solvent is a
combination of hot toluene and warm acetone.
44. The process of claim 41 wherein the solvent is
petroleum ether.
45. The process of claim 36 wherein the elemental
sulfur concentration in the coal following the elemental
removal step is less than about 200 parts per million.
46. The process of claim 36 wherein the elemental
sulfur concentration in the coal following the elemental
sulfur removal step is less than about 50 parts per mil15
lion.
47. The process of claim 36 wherein the elemental
sulfur concentration in the coal following the elemental
sulfur removal step is less than about 10 parts per million.
48. The process of claim 36 wherein the impurities
enhanced comprise pyrite.
49. The process of claim 36 wherein the impurities
enhanced comprise ash forming minerals.
* * * * *
4,119,410
13
wherein D is time in hours and T is temperature in
degrees Celsius, and not less than about 95° C., and
wherein K is at least about 0.5.
38. The process of claim 37 wherein the coal is heated 10
to a temperature of at least about 100° C. for at least
about one hour.
39. The process ofclaim 37 wherein the coal is heated
to a temperature of at least about 170° C. for at least
about one hour.
40. The process of claim 36 wherein the means for
removing at least a portion of the elemental sulfur contained
within the coal comprises a steam pretreatment
within a temperature range of from about 100° C. to
about 300° C. for at least 0.25 hours with from about 2% 20
to about 50% water based on the coal being treated.
41. The process of claim 36 wherein the means for
removing at least a portion of the elemental sulfur contained
within the coal comprises solvent extraction.
25
30
35
40
45
50
55
60
65