Attorney, Agent, or Firm-Sheridan, Ross, Fields &
McIntosh
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. [57]
[11]
[45]
ABSTRACf
4,120,665
Oct. 17, 1978
[73]
[21]
[22]
[51]
[52]
[58]
[56]
Assignee: Hazen Research, Inc., Golden, Colo.
Appl. No.: 761,307
Filed: Jan. 21, 1977
Int. Cl.2 CI0L 9/10; CIOB 57/00
U.S. O 44/1 R; 201/17
Field of Search 44/1 R; 201/17
References Cited
U.S. PATENT DOCUMENTS
In a process for improving coal wherein the raw coal is
tr~ated with a metal containing compound in order to
enhance the magnetic susceptibility of certain impurity
components contained in the raw coal permitting their
removal by magnetic separation, the improvement comprising
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:
D ;;; K{50/T-90]'
2,726,148
2,793,172
3,595,965
3,938,966
4,052,170
12/1955
5/1957
7/1971
2/1976
10/1977
McKinley et al. 44/1 R
Smith et aI 201/17 X
Franz et al. 201/17 X
Kindig et al. 44/1 R
Yan 44/1 R
wherein D 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
preferably at least about 25.
Primary Examiner-Carl Dees 42 Oaims, No Drawings
4,120,665
SUMMARY OF THE INVENTION
The process of the present invention entails initially
heating raw coal 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:
D ~ K(50/T-90)J
wherein D 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
preferably at least about 25, and then treating the raw
coal with a metal containing compound in order to
enhance the magnetic susceptibility of certain impurities
contained in the raw coal, thereby permitting their
removal by magnetic means.
2
rite or impurity particles. 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
5 effect a 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
10 susceptibility can be achieved by converting less than
0.1 percent of pyrite in pyritic coal into ferromagnetic
compounds of iron. ("Magnetic Separation of Pyrite
from Coals," Bureau of Mines Report of Investigations
7181, P.l.)
15 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 wherein the raw coal is reacted with substantially
undecomposed iron carbonyl which alters the
apparent 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 ofthe
present application that pretreating coal with heat
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 class 44 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
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 present 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 distance 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 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 specific grav- 50
ity 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 of
pyrite or other impurities from coal which has been 55
ground rme 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 separating 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 pretreatment process for selectively
enhancing the magnetic susceptibility of the pySimilarly
components of ash, such as Fe203' may 60
react with a metal to form a more strongly magnetic
compound, as for example, in accordance with the following
reaction:
DESCRIPTION OF THE PREFERRED
EMBODIMENT
The process ofthe present invention can be applied to
coals ofuniversal origin, as long as the coal contains one 5
or more impurities receptive to the metal treatment.
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 affecting the coal itself, a magnetic separation 10
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 15
of an impurity as used herein is intended to be defmed in
accordance with the following discussion. Every compound
of any type has a specifically defmed magnetic
susceptibility, which refers to the overall attraction of
the compound to a magnetic force. An alteration of the 20
surface characteristics will alter the magnetic susceptibility.
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 25
impurity is not actually changed, but the particle itself is
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 30
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 35
enhanced magnetic susceptibility. Examples of such
impurities include pyrite; ash-forming minerals, such as
clays and shales; and various sulfates, for example, calcium
sulfate and iron sulfate. For purposes of illustration
the discussion hereinafter refers to pyrite, but it is 40
to be understood that other suitable impurities may 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 45
what is termed herein as the "treatment" and/or magnetic
susceptibility enhancement "reaction" depending
upon the metal containing compound or compounds
and the reaction conditions employed. Some metal containing
compounds, with metals more magnetic than the 50
impurities, principally iron, under certain conditions
coat the impurity with the metal, thereby enhancing the
magnetic susceptibility of the impurity. Some metal
containing compounds affect the pyrite by combining
with some of the pyrite sulfur to yield an iron sulfide 55
more magnetic than pyrite. The following reaction
exemplifies this mechanism:
4,120,665
4
pyrite and iron pentacarbonyl present viable techniques
for enhancing the magnetic susceptibilities of impurities.
Other mechanisms undoubtedly also contribute to the
enhancing of the magnetic susceptibility, and again this
is principally determined by the particular metal containing
compound or compounds employed and the
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 compound
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 compounds.
Many organic iron containing compounds possess the
capability of enhancing the magnetic susceptibility of
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 millimeters
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 defmition include ferrocene and its derivatives
and beta-diketone compounds of iron. Specific
examples include ferrocene, dimethyl ferrocenedioate,
1,1'-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 1 grams per liter, more preferably at least
about 10 grams per liter, and most preferably at least
about 50 grams per liter at injection temperature. The
solvent must, of course, possess the above capabilities,
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, molybde-
65
3
In similar fashion, U.S. Pat. No. 3,938,966 and the
reaction mechanisms illustrated therein with respect to
6
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 inordi-
5 nate. Under circumstances when the temperature exceeds
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.
While operating within the above time-temperature
equation it is generally preferred that the pretreatment
essentially comprise heating the coal to a temperature of
at least about 1000 C., more preferably to a temperature
of at least about 1500 C., and most preferably to a temperature
of at least about 1700 C. This heat pretreatment
is preferably for at least about 1hour, and more preferably
for at least about 2 hours.
The heat pretreatment need not be immediately followed
by the magnetic enhancement reaction. Hence
the coal may be permitted to cool down to ambient
temperature, or any other convenient temperature,
prior to conducting the magnetic susceptibility enhancement
reaction.
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 is believed to volatilize various components
which can interfere with the magnetic enhancement
reaction. Hence, 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.
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,
ethane, propane, butane, and other hydrocarbon compounds
in the gaseous state at the pretreatment temperature.
When these additives are employed, it is preferable
that they be employed in an amount ofat least about 1.2,
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 1000 C. to about 3000
C., more preferably from about 1500 C. to about 2500
C., and most preferably from about 1750 C. to about
2250 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
one hour. The amount of water preferably ranges from
about 2% to about 50%, more preferably from about
5% to about 30%, and most preferably from about 10%
to about 25%, based on the weight of the coal being
treated.
One particularly preferred technique for performing
the pretreatment process of the invention is to conduct
the process while the coal is in a fluidized state. Conventional
fluidized bed apparati and processes are suit-
65
4,120,665
D ;;; K(50/T-90)3
wherein D 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
5
num, 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 10
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 15
is heated to a temperature just below its decomposition
temperature under the reaction conditions. Various
types of available 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 20
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 temperature below the temperature of major de- 25
composition of the carbonyl under the reaction conditions
so that there is opportunity for the iron of the
carbonyl to chemically react with the pyrite particles. If
the temperature is allowed to rise above the decomposition
temperature, the selectivity of the process of en- 30
hancing 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 35
temperature of from about 1500 to about 2000 C. and a
carbonyl concentration of from about 4 to about 32
pounds per ton of coal.
For efficient separations of pyrite from coal, the coal
should be crushed to such fmeness that pyrite particles 40
are free, or nearly free, from the coal particles. The
required fmeness 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- 45
cle Association in Steam Coals," Bureau of Mines Report
of Investigation 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-ftred power plants gener- 50
ally requires pulverizing the coal to 60-90 percent
minus 200 mesh before burning.
The improvement to which the process ofthe present
invention is directed comprises pretreating the raw coal
prior to initiating the reaction with the metal containing 55
compound.
This pretreatment essentially comprises heating the
coal in order to· render the coal and impurities more
receptive to the magnetic enhancement reaction. The
temperature and time of heating are interrelated, and 60
essentially higher temperatures require less time. It is
essentially preferred that the temperature and time be
selected in accordance with the following equation:
4,120,665
7
able. This fluidized treatment facilitates thorough pretreatment
of all of the coal.
8
tained a greater reduction ofboth ash and pyritic sulfur.
EXAMPLES Table 2
11.2
2.87
56.9
29.4
3.63
Feed
Pretreated Coal
Clean
Coal
29.2 12.2
3.69 4.48
56.5
Coal,
No Pretreatment
Clean
Feed Coal
Ash (%)
Pyritic Sulfur (%)
EXAMPLE 1 10Yiel-d (-%-) ''-.-:.-----------------
In all the examples given, the chemically treated coal 5
sample was separated in a magnetic separator to give a
non-magnetic clean coal fraction and a magnetic refuse
fraction.
EXAMPLE 3
The treating of 75 grams of Lower Freeport coal
with 16 kilograms per metric ton of iron pentacarboilyl
at 170° C. for one hour with a nitrogen purge of 250
milliliters per minute during heat-up and cool-down
resulted in a product yield of 56.9% containing 22.5%
ash and 1.85% pyritic sulfur. Pretreatment ofthe Lower
Freeport coal with heat and/or steam under various
reaction conditions followed by the same carbonyl
treatment described above resulted in greater reductions
ofboth ash and pyritic sulfur in the clean coal. The
raw coal in all samples was sized to l4-mesh X O. The
25 pretreatment conditions and clean coal analyses are
given in Table 3 below.
Table 3
Pretreated Coal
Clean
Coal,
No Pretreatment
Clean
A sample of Illinois No.6 coal was dry screened and
75 grams of the 14 X 150 mesh material was roasted at
a temperature of 190°-195° C. for 12 minutes and
treated with iron pentacarbonyl in an amount of 7.5
kilograms per metric ton of coal, the carbonyl being 15
carried in a nitrogen atmosphere. A batch of the identical
coal was pre-treated by heating it to 200° C. with
moist air passing through the reactor for 15 minutes
followed by dry air for five minutes, and was then given
an identical iron carbonyl treatment. Both samples were 20
subjected to magnetic separation, resulting in the analyses
set forth in Table 1.
Table 1
Variable Conditions Results
Pretreatment Clean Coal Product
Steam
Sample Water, Temp, Time, Cone., Yield Ash, Pyritic
Number mllmin 'C min % Atmos. Wt.% % S,%
No
Pretreatment 56.9 22.5 1.85
I 190 10 0 54.5 11.2 1.13
2 0.95 190 10 25 52.6 13.1 1.45
3 3.35 190 10 89 55.8 10.6 0.84
4 0 260 10 0 71.4 13.5 1.23
5 0.95 260 10 28 69.7 13.9 1.02
6 3.35 260 10 98 81.2 18.7 0.84
7 0 190 30 0 73.9 15.7 0.59
8 0.95 190 30 25 68.3 12.0 0.53
9 3.35 190 30 89 68.1 11.5 0.37
10 0 260 30 0 65.6 18.6 1.27
II 0.95 260 30 28 75.3 14.8 0.77
12 3.35 260 30 98 78.6 16.4 0.58
Raw Coal 28.1 1.76
EXAMPLE 4
The effects of adding various gases during the preconditioning
steam treatment on the results of the iron
carbonyl process on Lower Freeport coal are presented
in Table 4. The conditions common to each test consisted
of a charge of 75 grams of Lower Freeport coal,
mesh size 14 X 0, heated to 200° C. for 60 minutes
(including heat-up and cool-down in 250 milliliters per
minute of Nz) with water vapor introduced during the
run at 0.46 grams per minute. As indicated in Table 4,
various gases were added during the steam pretreatment.
The carbonyl treatment for all tests was conducted
at a temperature of 170° C. for one hour with 16
kilograms per metric ton of iron pentacarbonyl.
Feed Coal Feed Coal 45
Ash (%) 30.4 15.5 31.4 12.2
Pyritic Sulfur (%) 3.89 3.90 4.03 2.37
Yield (%) 64.0 59.3
EXAMPLE 2 50
A sample of Illinois coal as in Example 1 was treated
at 190°-195° C. for 30 minutes with 7.5 kilograms per
metric ton of iron pentacarbonyl carried in a nitrogen
atmosphere. An identical sample was similarly treated; 55
however, the coal was pretreated at 190°-195° C. for 30
minutes with a gas comprising nitrogen at 200 cubic
meters per hour per. metric ton and water vapor at 21
kilograms per hour per metric ton. As Table 2 indicates,
following magnetic separation, the pretreated coal ob-
Table 4
No
Sample Pretreatment . 2 4 6 7 8
Conditions:
Gas N2 CO N2 CO2 N2 Air N2 NH3 N2 S02 N2 N2 Butane N2
Flow, mllmin 150 50 100 27 123 150 150 50 100 50 100 150 50 100
Time, minutes 1-60 1-60 1-60 1-60 1-60 1-30 31-60 1-60 1-60 1-60 1-60 1-60 1-60 1-60
Yield, Weight %
Clean Coal 56.9 69.6 77.4 72.3 73.9 89.8 61.3 61.2 61.8
Table 4-continued
4,120,665
9
No
Sample Pretreatment 2
Ash, %
Clean Coal 22.5 13.3 17.7
Pyritic S, %
Clean Coal 1.85 0.40 0.52
15.9
0.47
4
15.3
0.42
25.1
1.0
10
6
11.9
0.57
7
15.3
0.44
9.6
0.31
The feed coal contained 29.9% ash and 1.63% pyritic sulfur.
Results
Clean Coal Product
56.9 22.5 1.85
69.6 23.6 1.67
77.8 16.8 0.63
89.2 23.9 0.57
66.3 24.2 I.74
84.3 18.6 0.60
86.7 22.0 0.72
60.\ 19.3 1.39
87.9 20.8 0.56
85.5 16.6 0.59
88.6 23.5 0.68
Yield, Ash Pyritic
Wt.% % S,%
22
2
888
16
16
16
16
Time,
Hours
123
178
225
123
178
225
123
178
180
225
Temp,
'C
Variable Conditions of
Pretreatment
I2
3
4
5
6
7
89
10
11
Sample
Number
EXAMPLE 7
A Lower Freeport bituminous coal from Pennsylvania
was sized to 14 X 0 mesh and samples were treated
for 60 minutes with 16 kilograms of iron pentacarbonyl
per metric ton of coal at a temperature of about 170° C.
Sample I was not initially pretreated; runs 2 through 13
were each 125 gram samples of coal which were dried
at. various temperatures for various times in a large
forced-air oven in 19 X 19 X 4.5 centimeter metal pans.
The dried samples were stored in a nitrogen atmosphere
until carbonyl treated. The temperature and time of
these pretreatments are given in Table 7.
45
10
1.09
0.83
0.93
Pyritic
Sulfur, %
10.8
9.0
10.0
Ash,%
84.6
84.0
86.5
Yield,
Wt.%
EXAMPLE 6
EXAMPLES
Pretreatment
None
Steam (190-195' C)
Steam (250-255' C)
I2
3
Sample
EXAMPLE 8
A sample of Illinois No. 6 coal was wet with water
and then dried in a fluid bed reactor with synthetic flue
gas consisting ofabout 5.5% O2,12.9% CO2, and 81.6%
N2 for 15 minutes at a temperature of 305° C. The sam-
Three identical samples of Pittsburgh coal, 14 X 0 pIe was treated (after a two year interval during which
mesh, containing 17.9% ash and 1.67% pyritic sulfur, 30 it was stored under nitrogen to prevent deterioration)
were treated with 8 kilograms per metric ton of iron for 60 minutes with 16 kilograms per metric ton of iron
pentacarbonyl at a temperature of 190°-195° C. for 60 pentacarbonyl at a temperature of 170° C. Following
minutes. The fIrst, Sample 1, was given no pretreat- magnetic separation, the clean coal represented 78.8%
ment. The second, Sample 2, was pretreated with steam of the starting material, with an ash content of 17.1%
at 95 kilograms per metric ton at a temperature of 35 and a pyritic sulfur content of 1.33%. The feed coal has
190°-195° C. for 60 minutes. The coal in Sample 3 was an ash content of 30.4% and a pyritic sulfur content of
pretreated with steam at 95 kilograms per metric ton at 3.89%, and this coal does not meaningfully respond to
a temperature of 250°-255° C. for 60 minutes. All the iron carbonyl treatment with respect to pyrite removal
samples were given the same iron pentacarbonyl treat- in the absence of a pretreatment.
ment. The coal pretreated with steam obtained greater 40 TABLE 7
reductions in both ash and pyritic sulfur content as
shown in Table 6 below.
Table 6
Both steam (derived from 192 kilograms of water per
metric ton of coal and injected over a one-hour period
into a chamber of coal at 200° C.) and heat (at 130° C.
for 30 minutes with N2 flow at 1.7 liters per minute) 15
pretreated Lower Freeport coal, size 14 X 0 - mesh,
were treated with various organic iron containing compounds
as shown in Table 5. The coal was heated stepwise
to the indicated temperatures and the iron compound,
which was vaporized externally, was injected as 20
vapor into the reaction chamber. The ferric acetylacetonate
was dissolved in acetone and mixed with the
coal, followed by drying in a stream of nitrogen. The
coal was then heated stepwise to operating temperature
with the temperature being increased slowly to the 25
indicated temperatures.
Table 5
Conditions
Maximum
Compound Temp,' C Kg/metric ton
Ferrocene 275 16
275 16.2
Ferrocene carboxylic
acid 275 7.9
275 9.7
Acetylferrocene 275 13
275 16.4
Dimethyl ferrocenedioate
275 15
275 15.6
Ferric acetylacetonate 285 16
285 16.1
Feed (untreated)
Time at
Max.Temp,
hr
I
I
0.33
0.33
Sample
I steamed
2 dried
3 steamed
4 dried
5 steamed
6 dried
7 steamed
8 dried
9 steamed
10 dried
Clean Coal Analysis
Inorganic
Yield, Ash, Sulfur,
Wt% % %
74.1 23.8 1.41
69.5 24.1 1.75
81.0 25.3 1.47
74.0 23.6 1.56
77.2 22.7 1.41
70.5 24.3 1.82
79.1 24.0 1.46
67.8 24.2 1.49
75.1 22.4 1.31
75.3 22.7 1.64
100 28.1 1.76
Variable Conditions of Results
Pretreatment Clean Coal Product
Sample Temp, Time, Yield, Ash Pyritic
Number ·C Hours Wt.% % S,% 5
12 123 48 59.1 16.5 1.04
13 178 48 88.5 22.3 0.63
14 225 48 87.5 23.0 0.72
D ~ K(SO/T_90)3
wherein D is time in hours and T is temperature in
degrees Celsius and is not less than about 950 C.,
and wherein K is at least about 0.5.
29. The process of claim 28 wherein K is at least
about 5.
30. The process of claim 28 wherein K is at least
about 25.
31. The process of claim 28 wherein the pretreatment
is performed at a temperature of at least 1500 C.
32. The process of claim 28 wherein the pretreatment
is performed at a temperature of at least 1700 C.
33. The process of claim 28 wherein the duration of
the pretreatment is at least 1 hour.
34. The process of claim 28 wherein the duration of
the pretreatment is at least 2 hours.
35. The process of claim 28 wherein the pretreatment
is conducted in the presence of one or more gaseous
additives.
12
14. The process of claim 1 wherein the pretreatment
is performed at a temperature of at least 1700 C.
15. The process ofclaim 1 wherein the duration ofthe
pretreatment is at least 1 hour.
16. The process of claim 1 wherein the duration of the
pretreatment is at least 2 hours.
17. The process of claim 1 wherein the pretreatment
is conducted in the presence of one or more gaseous
additives.
18. The process of claim 17 wherein the said gaseous
additives are selected from the group consisting of nitrogen,
steam, carbon monoxide, carbon dioxide, ammonia,
methane, air, ethane, propane, and butane.
19. The process of claim 17 wherein the gaseous
additive is steam.
20. The process of claim 17 wherein the said gaseous
additive is a hydrocarbon compound in the gaseous
state at the pretreatment temperature.
21. The process of claim 17 wherein the said gaseous
additives are employed in an amount ofat least 1.2 cubic
meters per hour per metric ton of coal being processed.
22. The process of claim 2 wherein the said organic
iron containing compound has a solubility of at least
about 1 gram per liter at the pretreatment temperature.
23. The process of claim 22 wherein the said compound
has a solubility of at least 10 grams per liter at
injection temperature.
24. The process of claim 22 wherein the solvent for
the organic iron containing compound is one or more
members selected from the group consisting of acetone,
petroleum ether, naphtha, hexane, and benzene.
25. The process of claim 1 wherein the impurities
comprise pyrite and ash-forming minerals.
26. The process of claim 25 wherein the impurity
comprises ash-forming minerals.
27. The process of claim 25 wherein the impurity
comprises pyrite.
28. In a process for improving coal wherein raw coal
is treated with iron carbonyl in order to enhance the
magnetic susceptibility of one or more impurities,
thereby permitting the removal of these impurities by
magnetic separation, the improvement comprising:
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:
10
4,120,665
11
TABLE 7-continued
D ~ K(50/T_90)3
wherein D is time in hours and T is temperature in 25
degrees Celsius and is not less than about 950 C.,
and wherein K is at least about 0.5.
2. The process of claim 1 wherein the said metal
containing compound is an organic iron containing
compound. 30
3. The process of claim 2 wherein the said 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. 35
4. The process of claim 3 wherein the said organic
iron containing compound is selected from the group
consisting of ferrocene, ferrocene derivatives, and betadiketone
compounds of iron. 40
5. The process of claim 4 wherein the said organic
iron containing compound is one or more members
selected from the group consisting of ferrocene, dimethyl
ferrocenedioate, 1,I'-ferrocenedicarboxylic
acid, ferric acetylacetonate, and ferrous acetylaceton- 45
ate.
6. The process of claim 1 wherein said metal containing
compound is an inorganic iron containing compound.
7. The process of claim 1 wherein said metal contain- 50
ing compound comprises one or more members selected
from the group consisting of iron carbonyl, nickel carbonyl,
cobalt carbonyl, molybdenum carbonyl, tungsten
carbonyl, and chromium carbonyl.
8. The process of claim 1 wherein said metal contain- 55
ing compound comprises iron carbonyl.
9. The process of claim 8 wherein said iron carbonyl
is iron pentacarbonyl.
10. The process of claim 9 wherein the iron pentacarbonyl
treatment is conducted within a temperature 60
range of from about 1500 C. to about 2000 C. for a period
of time of from about one-half to about four hours.
11. The process of claim 1 wherein K is at least about
5.
12. The process of claim 1 wherein K is at least about 65
25.
13. The process of claim 1 wherein the pretreatment
is performed at a temperature of at least 1500 C.
What is claimed is:
1. In a process for improving coal wherein raw coal
is treated with a metal containing compound in order to
enhance the magnetic susceptibility of one or more
impurities susceptible to the metal containing compound
treatment, thereby permitting the removal of 15
these impurities by magnetic separation, the improvement
comprising:
pretreating the coal byheating it to at least a temperature
for at least a period of time sufficient to essentially
meet or exceed a time and temperature rela- 20
tionship expressed as:
4,120,665
10
13
36. The process of claim 35 wherein the said gaseous
additives are selected from the group consisting of nitrogen,
steam, carbon monoxide, carbon dioxide, ammonia,
methane, air, ethane, propane, and butane.
37. The process of claim 35 wherein the gaseous 5
additive is steam.
38. The process of claim 35 wherein the said gaseous
additive is a hydrocarbon compound in the gaseous
state at the pretreatment temperature.
14
39. The process of claim 35 wherein the said gaseous
additives are employed in an amount of at least 1.2 cubic
meters per hour per metric ton of coal being processed.
40. The process of claim 28 wherein the impurities
comprise pyrite and ash-forming minerals.
41. The process of claim 40 wherein the impurity
comprises pyrite.
42. The process of claim 40 wherein the impurity
comprises ash-formin..g m.. in.e.ral.s.. ..
15
20
25
30
35
40
45
50
55
60
65
U NTI'ED STATES PATENT AND TRADEMARK OFFICE
CERTIFICATE OF CORRECTION
PATENT NO. :
DATED
4,120,665
October 17, 1978
INVENTOR(S): James K. Kindig and Ronald L. Turner
It is certified that error appears in the above-identified patent and that said Letters Patent
are hereby corrected as shown below:
3
In the Abstract, paragraph 1, "0 > K(50/T-90) ", should be
::::
--0 ~ K[ T~~OJ 3
Column 2, line 58, "0 ~ K(50/T-90) 3 .. , should be --0 ~ K [T~~O13
--.
Column 3, line 16, "of", should be --or--.
3
[ 50 13
Column 5, line 64, "0 > K(50/T-90) II , should be --0 ~ K T-90 --.
~
3
[ 50 JColumn 11, line 23, "0 --> K(50/T-90) " , should be --0 ~ K T-90 3--. 3
[ 50 03
Column 12, line 49, "0 > K(50/T-90) 'r should be --0 ~ K T-90 --. :;: ,
~igncd and ~calcd this
TIt;";",, Day of J••••,J' 1979
ISEAL!
Attest:
RUTH C MASON
Altes';., Office,
DONALD W. BANNER
Commissio." of P.tr"ts ••11 T,.II,m.,ks