111111111111111111111111111111111111111111111111111111111111111111111111111
US006231627Bl
(12) United States Patent
Reeves et al.
(10) Patent No.:
(45) Date of Patent:
US 6,231,627 Bl
May 15,2001
(54) METHOD TO REDUCE OXIDATIVE
DETERIORATION OF BULK MATERIALS
(75) Inventors: Robert A. Reeves, Arvada; Charlie W.
Kenney, Littleton; Mark H. Berggren,
Golden, all of CO (US)
(73) Assignee: Hazen Research, Inc., Golden, CO
(US)
4,957,596
5,087,269
5,124,162
5,435,813
5,609,458
5,795,856
5,919,277 *
5,968,891
9/1990 Ukita et al. . 201/20
2/1992 Cha et al. 44/501
6/1992 Boskovic et al. 426/96
7/1995 Evans 44/620
3/1997 Hanaoka et al. 414/173
8/1998 Hatano et al. 510/444
7/1999 Reeves 44/501
10/1999 Mallari et al. 510/444
OTHER PUBLICATIONS
Related U.S. Application Data
(56) References Cited
U.S. PATENT DOCUMENTS
(21) Appl. No.: 09/220,271
(22) Filed: Dec. 22, 1998
(63) Continuation-in-part of application No. 08/995,710, filed on
Dec. 22, 1997, which is a continuation-in-part of application
No. 08/667,637, filed on Jul. 8, 1996, now Pat. No. 5,725,
613.
(51) Int. Cl? CIOL 5/00
(52) U.S. Cl. 44/620; 44/501; 44/591;
44/592
(58) Field of Search 44/501, 591, 592,
44/620
Standish et aI., "Optimization of Coal Grind for Maximum
Bulk Density," Powder Technology, vol. 68, 1991, pp.
175-186.
Furnas, c.c., "Flow of Gases Through Beds of Broken
Solids," United States Department of Commerce, Bureau of
Mines, Bulletin 307, pp. 74-83, 1929.
Furnas, c.c., "Grading Aggregates-Mathematical Relations
for Beds of Broken Solids of Maximum Density,"
Industrial and Engineering Chemistry, vol. 23, No.9, pp.
1052-1058, 1931.
Edwards, 1995, Catalysis Today, 23: 59-66.
Keirn, "Industrial Uses of CarbonDioxide", in Carbonoxide
as a Source of Carbon, M. Aresta and G. Forti, eds., D.
Reidel Publidhing Co., 1987, 23-31.
Rigsby et aI., "Coal Self-Heating Promblems and Solutions",
pp. 102-106.
Riley et aI., J. Coal Quality, Apr. 1987, pp. 64-67.
Ripp. "Understanding Coal Pile Hydrology can help BTU
loss in stored coal", pp. 146-150.
Sapienze et aI., "Carbon DioxidelWater for Coal Beneficiation",
in Mineral Matter and Ash in Coal, 1986 American
Chemical Society, pp. 500-512.
Subject to any disclaimer, the term of this
patent is extended or adjusted under 35
U.S.c. 154(b) by 0 days.
( *) Notice:
42 Claims, No Drawings
* cited by examiner
Primary Examiner-Margaret Medley
Assistant Examiner-Cephia D. Toomer
(74) Attorney, Agent, or Firm---8heridan Ross Pc.
A method and composition are disclosed to reduce the
oxidative deterioration of bulk materials. Preferred embodiments
of bulk materials include solid fuel materials, such as
coal, and bulk food products. The method includes sizing a
bulk material so that it has a porosity of 40% or less. This
relatively low porosity reduces the surface area of the bulk
material available to the ambient environment for oxidation.
The method of sizing the bulk material may be combined
with the step of contacting the bulk material with an inert gas
or a heat transfer medium.
(57) ABSTRACT
Re. 33,788 1/1992 Clay 149/1
3,243,889 4/1966 Ellman et al. 34/9
3,957,456 5/1976 Verschuur 44/10 E
3,969,124 7/1976 Stewart 106/56
4,083,940 4/1978 Das 44/620
4,170,456 10/1979 Smith 44/1
4,186,054 1/1980 Brayton et al. 201/6
4,257,848 3/1981 Brayton et al. 202/82
4,304,636 12/1981 Kestner et al. 201/20
4,396,394 8/1983 Li et al. 44/1
4,401,436 8/1983 Bonnecaze 44/1
4,450,046 5/1984 Rice et al. 201/20
4,511,363 4/1985 Nakamura et al. 44/501
4,599,250 7/1986 Cargle et al. 427/220
4,613,429 9/1986 Chiang et al. 209/5
4,650,495 3/1987 Yan 44/1
4,759,772 * 7/1988 Rogers et al. 44/501
4,778,482 * 10/1988 Bixel et al. 44/501
4,797,136 1/1989 Siddoway et al. 44/501
4,828,575 5/1989 Bellow, Jr. et al. 44/501
4,828,576 5/1989 Bixel et al. 44/501
US 6,231,627 B1
2
fuel materials, bulk food products, sulfide ores and carboncontaining
materials such as activated carbon and carbon
black. In further preferred embodiments, the solid fuel
material can be coal, upgraded coal products, oil shale, solid
5 biomass materials, refuse derived (including municipal and
reclaimed refuse) fuels, coke, char, petroleum coke,
gilsonite, distillation byproducts, wood byproduct waste,
shredded tires, peat and waste pond coal fines.
The method includes preparing a first amount of the bulk
10 material in a first size, and preparing a second amount of the
bulk material in a second size. These two size fractions are
then combined. The proportions in which the first and
second sizes are combined is controlled so that the resulting
porosity of the combination of the bulk material is about
40% or less. By reducing the porosity from what might
15 otherwise be present after the preparation of the bulk
material, the surface area of the bulk material in contact with
the ambient environment is reduced. This then reduces the
amount of bulk material available to the ambient environment
for oxidation. In addition to the reduced surface area,
20 the reduced porosity provided by this method inhibits the
rate at which gas may flow through the bulk material. This
reduced gas flow also limits the oxidative deterioration of
the bulk material by reducing the amount of oxygen available
to the bulk material for oxidation. A further benefit of
25 the disclosed method is that the reduction in porosity also
results in an increase in the density of the bulk material,
thereby reducing the volume of the bulk material that must
be handled and stored for a given tonnage of the bulk
material.
The steps of preparing amounts of the bulk material in two
different sizes may be accomplished through a variety of
methods. Such methods may include crushing or grinding or
pelletizing the bulk material. In a preferred embodiment of
the present invention, the bulk material is crushed to a
particle size of 2 inches or less. A first fraction of the crushed
35 material, ranging in particle size from about Y2 inch to about
2 inches particle size, is recovered. Separately, a second
fraction of less than 4 mesh particle size is recovered, as is
a third fraction of about Y2 inch to about 4 mesh particle size.
The first and second fractions are reserved while the third
40 size fraction is further crushed to about less than 4 mesh
particle size. The first, second and third size fractions are
then combined, resulting in a bulk material having a porosity
of 40% or less.
In a further embodiment of the present invention, a bulk
45 material having a porosity of 40% or less is prepared as
described in the above-mentioned embodiments. This bulk
material is then aggregated into a storage pile until the bulk
material is ready for use. This method of storing a bulk
material results in lower rates of oxidative deterioration than
50 might otherwise be achieved.
In addition, the present invention includes a bulk material
that may be produced as described in the disclosed method.
Such material will have a porosity of 40% or less, gained by
the bi-modal particle size distribution achieved by the
55 described method. In further embodiments, the method may
include contacting the prepared bulk material with an inert
gas or heat transfer medium. When the bulk material is
aggregated into a storage pile, contacting the bulk material
with an inert gas or heat transfer medium may include the
60 step of adjusting the density of the gas or heat transfer
medium, so that the gas or heat transfer medium remains in
contact with the bulk material in the storage pile for the
maximum amount of time.
RELATED APPLICATIONS
FIELD OF THE INVENTION
SUMMARY OF THE INVENTION
BACKGROUND OF THE INVENTION
1
METHOD TO REDUCE OXIDATIVE
DETERIORATION OF BULK MATERIALS
When bulk materials contact the ambient environment,
they are subject to oxidative deterioration because of contact
with oxygen and air. Such oxidative deterioration can have
many negative effects. For example, when a solid fuel
material, such as coal, is being transported from a mine to a
utility or is in storage at a utility, it is subject to oxidation.
One negative aspect of such oxidative deterioration is a loss
in the thermal value of the coal. Depending upon the type of
coal and its water content, among other factors, between 1%
and 5% of the thermal value of coal can be lost from the time
it is mined until the time at which it is consumed. These 30
losses are sizeable in the domestic United States utility
industry, which consumes about 800 million tons of coal per
year. Such losses are particularly significant for low rank
coals such as lignite and sub-bituminous coals, especially
for such materials which have been upgraded by thermal
treatment to reduce moisture. Moreover, low level oxidation
of coal generates heat. As a result, there is a significant risk
of certain coal materials self-igniting, resulting in a risk to
property and life.
Most efforts to reduce oxidative deterioration have
focused on reducing the risk of self-heating and thereby
self-ignition of coals. The problem has been addressed by a
variety of approaches. One such approach is by compacting
coal as it is transported or stored. By compacting coal, the
surface area of the coal that is in contact with the ambient
environment can be reduced. Such a reduction of surface
area contact reduces the amount of coal available for oxidation
by the ambient environment. Another approach has
been to flatten and trim coal piles to decrease the ability of
the coal pile to hold heat and therefore generate enough heat
through self-heating to self-ignite. In addition, contacting
coal materials with various fluids, such as hydrocarbon
based materials, has been used.
While the more chronic problem of loss of economic
value of bulk materials, such as the loss of heating values in
coal, has been recognized and studied, adequate widespread
use of strategies for significantly reducing economic losses
from this problem have not been achieved. Therefore, a need
exists for reducing the oxidative deterioration of bulk materials.
The present invention relates to a method and composition
for reducing the oxidative deterioration of bulk materials.
In particular, the invention relates to the reduction of
oxidative deterioration of solid fuel materials, such as coal.
This application is a continuation-in-part application of
U.S. patent application Ser. No. 08/995,710 filed on Dec. 22,
1997, which is a continuation-in-part of U.S. patent application
Ser. No. 08/667,637 filed on Jul. 8, 1996, now U.S.
patent application Ser. No. 5,725,613, both of which are
incorporated herein by reference.
The present invention includes a method to reduce oxidative
deterioration of bulk materials, particularly including 65
oxidizable and highly reactive bulk materials. In preferred
embodiments, the bulk materials in question include solid
DETAILED DESCRIPTION
The present invention concerns a method to reduce oxidative
deterioration of bulk materials, and bulk materials
US 6,231,627 B1
3 4
bulk material is to be burned, the energy available for use is
reduced by the presence of water because of the large
amount of energy consumed in vaporizing the water.
In addition to the tendency of bulk materials such as coal,
5 lignite, and other organic materials to oxidize while held in
storage, a feature of such materials is that aggregate amounts
contain voids through which air may pass. This is because
bulk materials consist of individual particles of various sizes
surrounded by interstitial void spaces. Air infiltrates the bulk
10 material from the surrounding atmosphere through these
interstitial void spaces. Air provides the oxygen necessary
for the oxidation process to proceed.
Reducing the volume of the void space and making the
paths through the interstitial void spaces more tortuous
15 increases the resistance to flow, thus reducing the flow rate.
This in turn reduces the amount of oxygen available for
contact with the bulk material, reducing the rate of oxidation.
Beneficial reductions in the volume of the void space
and increases in the tortuousness of the pathways between
20 individual particles of the bulk material may be gained
through careful control of the particle size distribution of the
bulk material.
The particle size distribution is the relative percentage of
fine and coarse particles in the bulk material. An ideal
25 particle size distribution provides sufficient quantity of fine
particles to fill the void spaces surrounding coarse particles.
Therefore, the remaining void space is reduced when compared
with, for example, bulk material having a uniform
particle size, and the tortuousness of the pathways formed in
30
the void space is increased. The quantity of fine particles
necessary to fill the void spaces depends on the particle
shape and the degree to which the particles nest together.
Many materials produced by standard crushing, grinding
35 or pulverization processes do not generate advantageous
ratios of fine particles to coarse particles so as to minimize
the void space and air flow rate through the material.
However, specific size classification and size reduction
processes can be employed to generate a bulk material with
40 an advantageous particle size distribution that results in a
bulk material that is more resistant to air infiltration.
The method and composition disclosed herein describe
advantageous amounts of void space as a percent of the total
volume of the bulk material ("porosity"), and discloses
45 means by which such advantageous characteristics can easily
and economically be attained. In describing advantageous
particle size distributions, it is convenient to make
reference to a bi-modal particle size distribution. A bi-modal
size distribution is characterized by material having two
50 discontinuous particle size ranges. Thus, for example, a bulk
material having a bi-modal particle size distribution might
have a first particle size range of minus 4 mesh, and a second
particle size range of Y2 inch by 2 inches. Another way to
describe a bi-modal size distribution is with reference to a
55 graph plotting the total weight of particles having a certain
particle size against the particle size. Where the particle size
distribution is bi-modal, such a graph will be characterized
by two discrete areas under a curve, each generally having
a gaussian shape.
The present method includes sizing a first amount of the
bulk material to a first size fraction and sizing a second
amount of the bulk material to a second size fraction. The
prepared first and second size fractions are then combined in
proportion such that the resulting porosity of the bulk
65 material is about 40% or less. Porosity, as used herein,
generally refers to the void space within the volume of bulk
material. Therefore, a volume of material having a porosity
prepared according to the disclosed method. The term "bulk
materials" refers to any solid materials which are produced,
shipped and/or stored in quantities that are generally measured
on a tonnage basis, and preferably includes oxidizable
and highly reactive materials. Bulk materials can include
solid fuel materials, bulk food products, sulfide ores and
carbon containing materials, such as activated carbon and
carbon black.
Solid fuel material, as used herein, generally refers to any
solid material that is combusted for some useful purpose.
More particularly, solid fuel materials can include coal,
upgraded coal products, and other solid fuels. The term
"coal" includes anthracite, bituminous coal, sub-bituminous
coal and lignite. The present invention is particularly suited
for bituminous coal, sub-bituminous coal and lignite. The
term "upgraded coal products" includes thermally upgraded
coal products, coal products produced by beneficiation
based upon specific gravity separation, mechanically
cleaned coal products, and coal products such as stoker,
breeze, slack and fines. The present invention is particularly
suited for thermally upgraded coal because of significantly
increased risk of oxidative deterioration and/or self-ignition.
Thermally upgraded products are likely to have a higher rate
of oxidation because of formation of reactive components
which increase the rate of oxidation. In addition, such
materials typically have had water removed to a significant
extent. If such materials are subsequently exposed to humid
environments, the materials will re-wet, thereby generating
heat through the heat of hydration.
Examples of other solid fuels embodied in the present
invention include, but are not limited to, oil shale, solid
biomass materials, refuse derived (including municipal and
reclaimed refuse) fuels, coke, char, petroleum coke,
gilsonite, distillation byproducts, wood byproduct waste,
shredded tires, peat and waste pond coal fines. The term
"solid biomass" can include, for example, wood waste,
agricultural waste, and grass. The term "refuse derived
fuels" can include, for example, landfill material from which
non-combustible materials have been removed.
In an embodiment of the present invention, bulk materials
include bulk food products. Such bulk food products include
food products that tend to deteriorate in storage. Since the
food industry is concentrated on preservation of land food
products such as meats, dairy and vegetables, there remains
a need in the industry for low-cost, effective preservation of
bulk food products such as bulk grains and related byproducts.
According to the present invention, bulk food products
can include bulk grains, animal feed and related byproducts.
Examples of such bulk grains include, but are not limited to,
wheat, corn, soybeans, barley, oats, and any other cereal
grain that deteriorates in storage.
Examples of other oxidizable and highly reactive solid
bulk materials embodied in the present invention include,
but are not limited to, sulfide ores and carbon-containing
materials, such as activated carbon and carbon black.
Oxidative deterioration, as used herein, generally refers to
the undesired and uncontrolled reaction of the bulk material
with oxygen in the ambient environment. This oxidation is
undesirable because it consumes or reduces the energy 60
available in the bulk material. In addition to degrading the
energy potential of the material, the oxidative deterioration
of bulk material raises the temperature of the bulk material,
increasing the risk of spontaneous combustion. Furthermore,
a typical feature of combustion processes such as oxidative
deterioration is the production of water, which is undesirable
because it creates material handling problems. Where the
US 6,231,627 B1
5 6
than 4 mesh size. This bimodal size distribution increases
the packing density of the bulk material, concomitantly
reducing the porosity of the material in aggregate, increasing
the aggregate density of the material, and making the
5 pathways through the interstitial void space in the material
more tortuous.
In another embodiment, the disclosed method includes
contacting the bulk material with an inert gas. Such contact
with an inert gas further reduces the oxidative deterioration
of the bulk material by displacing oxygen that might otherwise
be in contact with the bulk material. The inert gas also
may react with the surface of the bulk material to passivate
the material from oxidation by the ambient air. Therefore, a
preferred embodiment of the present invention is one in
15 which a bulk material has been sized and sorted to attain a
porosity of 40% or less, and then contacted with an inert gas.
Contacting with an inert gas may be accomplished by
introducing the inert gas into the interior of the storage pile,
such as by inserting a pipe or other distribution device into
the storage pile at various points throughout the pile and
injecting an appropriate amount of inert gas.
Another preferred embodiment includes the step of contacting
the bulk material with a heat transfer medium, and
cooling the bulk material to below about 10° C. More
preferably, the step of contacting the bulk material with a
heat transfer medium includes cooling the bulk material to
below about 5° C. In a further preferred embodiment, the
step of contacting the first and second size fractions of the
bulk material with a heat transfer medium includes cooling
the bulk material to between about 0° C. and about 3° C.
With respect to the use of a heat transfer medium in
connection with any of the processes described herein,
reference is made to U.S. Pat. No. 5,725,613 to Reeves et aI.,
which issued on Mar. 10,1998. The disclosure made in U.S.
Pat. No. 5,725,613, which shares the same assignee as does
the present disclosure, is specifically incorporated herein by
reference.
In embodiments of the present invention in which the bulk
material is fuel, an important advantage of the invention is
that reductions in oxidative deterioration of the fuel material
correspond to reductions in the loss of heating value of the
fuel. For example, in an additional preferred embodiment,
where the bulk material in question is a fuel, the bulk fuel
material loses less than about 5% of its heating value over
a period of 9 days, more preferably less than about 3%, and
most preferably less than about 1%.
In one embodiment of the present method, bulk material
prepared according to the method described above is aggregated
into a pile for storage until the bulk material is ready
for use. Bulk material so prepared is advantageous when
stored as compared to bulk material prepared using standard
methods, because the reduced porosity of the bulk material
reduces the oxidative deterioration of the bulk material. In
addition, the reduced porosity results in a reduced overall
volume of the bulk material, reducing the amount of storage
space required.
As noted above, material prepared in accordance with the
above-described method may comprise coal, and in
60 particular, bituminous coal, sub-bituminous coal or lignite.
Where the bulk fuel material is lignite, the density of the
bulk fuel material after processing according to the present
method will preferably be approximately 40 lbs./fe of
material or greater, more preferably about 50 lbs./feor
greater, and most preferably about 55 lbs./fe or greater.
The present invention also includes reducing the oxidative
deterioration of a bulk material by aggregating an amount of
of 40% or less is comprised of the bulk material in an
amount of 60% or more of the total volume, and a void or
open space of 40% or less. In preferred embodiments, the
resulting porosity is about 30% or less, and most preferably
about 20% or less.
In one embodiment of the method of the present
invention, the steps of sizing the bulk material may be
achieved through crushing or grinding the material. Such
crushing or grinding may preferably be performed at the site
where the bulk material is produced, e.g., at a mine. In a 10
further preferred embodiment, the bulk material may consist
of coal, upgraded coal products, oil shale, solid biomass
materials, refuse derived fuels, coke, char, petroleum coke,
gilsonite, distillation byproducts, wood byproduct wastes,
shredded tires, peat and waste pond coal fines.
In another embodiment, the step of preparing a first size
fraction of the bulk material comprises preparing a first size
fraction of from about Y2 inch to about 2 inch particle size,
and preparing a second size fraction of less than about 4
mesh particle size. For example, the bulk material, such as 20
a bulk fuel material, may be recovered such that the size of
its particles are less than about 2 inches, or crushed such that
the size of its particles is less than about 2 inches. From this
bulk material, a first fraction of from about Y2 inch to about
2 inch particle size is recovered. A second fraction of about 25
less than 4 mesh particle size is also recovered. Finally, a
third fraction of from about Y2 inch to about 4 mesh particle
size is recovered. Then, the third recovered fraction is
crushed to a particle size of less than 4 mesh. The resulting
first, second and third fractions of material are then 30
combined, resulting in a bulk fuel material preferably having
a porosity of 40% or less, more preferably having a porosity
of 30% or less, and most preferably having a porosity of
20% or less.
35
The above-described steps of recovering first, second and
third size fractions may be performed using screens to size
the bulk fuel material. An example of such a sorting technique
is as follows: Coal is recovered from a deposit and
crushed to a particle size of about 2 inches or less. The coal 40
is then passed over a first screen or mesh that allows
particles of less than about 2 inches to pass through the
screen or mesh, and directs particles of larger than about 2
inches to a storage container. The material that is less than
2 inches in particle size is then passed over a second screen 45
having a size of 4 mesh. This second screen thus allows
material having a particle size of less than about 4 mesh to
pass through. The material that passes through the second
screen is then combined with the material rejected by the
first screen having a particle size of greater than about 2 50
inches.
The material of size greater than about 4 mesh that is
rejected by the second screen is crushed a second time to a
size of less than about 4 mesh. The bulk fuel material from
the second crushing step is then combined with the previ- 55
ously sorted material having a particle size of greater than
about 2 inches and that having a particle size of less than
about 4 mesh. The resulting aggregate of bulk material
preferably has a porosity of about 40% or less, more
preferably 30% or less, and most preferably 20% or less.
In addition to the porosity of 40% or less achieved by the
described method, the bulk material so produced is further
characterized by having a bi-modal size distribution. This
bi-modal size distribution features a first amount of bulk
material having a relatively large number of particles of 65
about 2 inches in size, and a second amount of bulk material
having a relatively large number of particles of about less
US 6,231,627 B1
7 8
3.6
9.1
13.5
Modified Product
4.5
lOA
15.0
TABLE 2
Standard Product
2
5
10
Air Pressure,
inches water column
Airflow Through Standard and Modified Lignite (Liters per Minute)
through the samples was measured and recorded. Results,
summarized in Table 2, show that the modified product is
more resistant to airflow than the standard product. The
difference becomes even greater at higher pressures.
65
60
While various embodiments of the present invention have
been described in detail, it is apparent that modifications and
adaptations of those embodiments will occur to those skilled
in the art. It is to be expressly understood, however, that such
modifications and adaptations are within the scope of the
present invention, as set forth in the following claims.
What is claimed is:
1. A method to reduce oxidative deterioration of a bulk
fuel material, the method comprising the steps of:
sizing a first amount of the bulk fuel material to a first size
fraction;
sizing a second amount of the bulk fuel material to a
second size fraction;
sizing a third amount of the bulk fuel material to a third
size fraction;
reducing a particle size of said third size fraction to said
second size fraction; and
combining the first second and third amounts of the bulk
fuel material to attain a resulting porosity of the bulk
fuel material of about 40% or less.
2. A method, as claimed in claim 1, wherein the sizing
steps comprise crushing the bulk fuel material.
3. A method, as claimed in claim 1, wherein the sizing
steps are performed at the place where the bulk fuel material
is produced.
4. A method, as claimed in claim 1, wherein the bulk fuel
material is selected from the group consisting of coal,
upgraded coal products, oil shale, solid biomass materials,
refuse-derived fuels, coke, char, petroleum coke, gilsonite,
distillation by-products, wood by-product wastes, shredded
45 tires, peat and waste pond coal fines.
5. A method, as claimed in claim 1, wherein the first size
fraction has a particle size of from about Y2 inch to about 2
inch, and wherein the second size fraction has a particle size
of less than about 4 mesh.
6. A method, as claimed in claim 1, further comprising the
step of:
contacting the combined first and second amounts with an
inert gas.
7. A method, as claimed in claim 1, further comprising the
55 step of: contacting the combined first and second amounts
with a heat transfer medium to cool the bulk fuel material to
below about 10° C.
8. A method, as claimed in claim 1, further comprising the
step of:
contacting the combined first and second amounts with a
heat transfer medium to cool the bulk fuel material to
below about 5° C.
9. A method, as claimed in claim 1, further comprising the
step of:
contacting the combined first and second amounts with a
heat transfer medium to cool the bulk fuel material to
between about 0° C. and about 3° C.
33%
25%
42%
Modified Product
52%
25%
23%
TABLE 1
EXAMPLES
Size Fraction Standard Product
25mmx6mm
6mmx2mm
2mmxOmm
Size Distribution of Minus 25-mm Lignite Samples Direct Weight Percent
Example 1
This example evaluates the resistance to airflow that is
achieved using varying particle size distributions of lignite.
An experiment was conducted to demonstrate how lignite,
a common bulk material susceptible to oxidation, can be
made more resistant to airflow by modifying the particle size 50
distribution. The experiment compared air flow rate through
a volume of lignite crushed by standard methods with lignite
processed by special size classification and size reduction
methods. The size distribution of the standard and modified
lignite samples is summarized in Table 1.
The standard and modified products were placed in a
chamber pressurized with air. The flow rate of air moving
the bulk material into a pile, and introducing a combination
of at least two inert gases into the pile, wherein the proportion
of the inert gases provides a density to maintain a stable
mass of the composition within the pile. In order to ensure
such a stable mass, the mass per unit volume of the selected 5
inert gases should preferably differ, allowing the density of
the resulting combination of inert gases to be adjusted by
providing the inert gases in varying proportions. Thus,
where the temperature of the pile is higher than that of the
ambient air, the relative proportion of the heavier inert gas 10
or gases is advantageously increased, to prevent the inert gas
combination from flowing out the top of the pile. Where the
temperature of the pile is less than that of the ambient air, the
relative proportion of the lighter inert gas or gases is
advantageously increased, to prevent the inert gas combi- 15
nation from flowing out the bottom of the pile. In particular
embodiments of this method, the inert gases may be selected
from the group consisting of flue gas, carbon dioxide, carbon
monoxide, nitrogen and argon.
In another embodiment, the present invention also 20
includes a method to reduce oxidative deterioration of a bulk
material comprising aggregating an amount of the bulk
material into a pile. The ambient air temperature and the
temperature of the bulk material is then determined, and a
composition is prepared that comprises at least two inert 25
gases having a density at the temperature of the bulk
material that approximates the density of the air at the
ambient air temperature. This composition of inert gases is
then introduced into the pile. This method ensures that the
inert gas will remain in contact with the bulk material for an 30
effective period of time, reducing oxidation of the material
in the pile. The inert gases may be introduced into the pile
by, for example, inserting a pipe or other distribution device
into various points throughout the storage pile and injecting
an appropriate amount of the composition of inert gases. In
one embodiment of the present invention, the inert gases are 35
selected from the group consisting of flue gas, carbon
dioxide, carbon monoxide, nitrogen and argon. In another
embodiment of the invention, the inert gases comprise flue
gas, carbon dioxide and nitrogen.
The following example is provided for purposes of illus- 40
tration only and is not intended to limit the scope of the
invention.
US 6,231,627 B1
9 10
55
23. A method as claimed in claim 22, wherein said step of
providing a bulk fuel material having a particle size distribution
to achieve a porosity of the bulk fuel material of
about 40% or less comprises the steps of:
sizing a first amount of the bulk fuel material to a first size
fraction;
sizing a second amount of the bulk fuel material to a
second size fraction; and
combining the first and second amounts of the bulk fuel
material to attain said porosity of the bulk fuel material
of about 40% or less.
24. A method as claimed in claim 23, wherein the sizing
steps comprise crushing the bulk fuel material.
25. A method as claimed in claim 23, wherein the sizing
15 steps are performed at the place where the bulk fuel material
is produced.
26. A method as claimed in claim 22, wherein the bulk
fuel material is selected from the group consisting of coal,
upgraded coal products, oil shale, solid biomass materials,
20 refuse-derived fuels, coke, char, petroleum coke, gilsonite,
distillation by-products, wood by-product wastes, shredded
tires, peat and waste pond coal fines.
27. A method, as claimed in claim 23, wherein the first
size fraction has a particle size of from about Y2 inch to about
25 2 inch, and wherein the second size fraction has a particle
size of about -4 mesh.
28. A method, as claimed in claim 22, further comprising
the step of:
contacting the bulk fuel material with an inert gas.
29. A method, as claimed in claim further comprising the
step of:
contacting bulk fuel material with a heat transfer medium
to cool the bulk fuel material to below about 10° C.
30. A method, as claimed in claim 22, further comprising
35 the step of:
contacting the bulk fuel material with a heat transfer
medium to cool the bulk fuel material to below about
5° C.
31. A method, as claimed in claim 22, further comprising
40 the step of:
contacting the bulk fuel material with a heat transfer
medium to cool the bulk fuel material to between about
0° C. and about 3° C.
32. A method, as claimed in claim 22, wherein the bulk
45 fuel material is a fuel material and loses less than about 3%
of its heating value over a period of 9 days.
33. A method, as claimed in claim 22, wherein the bulk
fuel material comprises coal, and wherein the coal is
selected from the group consisting of bituminous coal,
50 sub-bituminous coal and lignite.
34. A bulk fuel material having a bi-modal particle size
distribution to achieve a porosity of the bulk fuel material of
about 40% or less and having a density of about 40 pounds
per cubic foot or greater.
35. A bulk fuel material, as claimed in claim 34, wherein
said bi-modal particle size distribution can include material
that can be divided into three particle size fractions wherein
each of the largest and smallest of the size fractions constitutes
a greater weight percentage of the total bulk fuel
60 material than the intermediate size fractions.
36. A bulk fuel material, as claimed in claim 34, wherein
a graph having an x-axis representing particle size and a
y-axis representing weight percent of said bulk fuel material
is characterized by having two local maxima.
37. A bulk fuel material, as claimed in claim 34, wherein
the bulk fuel material comprises lignite and wherein the bulk
fuel material has a density of 40 Ib/ft3 or greater.
10. A method, as claimed in claim 1, wherein the bulk fuel
material loses less than about 3% of its heating value over
a period of 9 days.
11. A method, as claimed in claim 1, wherein the bulk fuel
material comprises coal, and wherein the coal is selected 5
from the group consisting of bituminous coal, subbituminous
coal and lignite.
12. A method to reduce oxidative deterioration of a bulk
fuel material having a particle size of less than about 2
inches, the method comprising the steps of: 10
recovering a first fraction of the bulk fuel material having
a particle size of about Y2 inch to about 2 inch;
recovering a second fraction of the bulk fuel material
having a particle size of less than about 4 mesh;
recovering a third fraction of the bulk fuel material having
a particle size of about Y2 inch to about 4 mesh;
crushing the third fraction to a particle size of less than
about 4 mesh;
combining the first, second and third fractions.
13. A method, as claimed in claim 12, further comprising
the step of aggregating the bulk fuel material into a storage
pile.
14. A method as claimed in claim 12, wherein the bulk
fuel material comprises lignite and the combined first,
second and third fractions of the lignite have a density of
greater than 40 pounds per cubic foot.
15. A method as claimed in claim 12, wherein the bulk
fuel material comprises coal, and wherein the coal is
selected from the group consisting of bituminous coal,
sub-bituminous coal and lignite.
16. A method, as claimed in claim 12, wherein the bulk 30
fuel material is selected from the group consisting of coal
upgraded coal products, oil shale, solid biomass materials,
refuse-derived fuels, coke, char, petroleum coke, gilsonite,
distillation by-products, wood by-product wastes, shredded
tires, peat and waste pond coal fines.
17. A method, as claimed in claim 12, further comprising
the step of:
contacting the combined first, second and third fractions
with an inert gas.
18. A method, as claimed in claim 12, further comprising
the step of:
contacting the combined first, second and third fractions
with a heat transfer medium to cool the bulk fuel
material to below about 10° C.
19. A method, as claimed in claim 12, further comprising
the step of:
contacting the combined first, second and third fractions
with a heat transfer medium to cool the bulk fuel
material to below about 5° C.
20. A method, as claimed in claim 12, further comprising
the step of:
contacting the combined first, second and third fractions
with a heat transfer medium to cool the bulk fuel
material to between about 0° C. and about 3° C.
21. A method, as claimed in claim 12, wherein the bulk
fuel material loses less than about 3% of its heating value
over a period of 9 days.
22. A method to reduce oxidative deterioration of a bulk
fuel material, the method comprising the steps of:
providing a bulk fuel material having a bi-modal particle
size distribution to achieve a porosity of the bulk fuel
material of about 40% or less; and
aggregating the bulk fuel material having a porosity of
40% or less into a storage pile, wherein said bulk fuel 65
material has a density of 40 pounds per cubic foot or
greater.
US 6,231,627 B1
11 12
* * * * *
a porosity of 40% or less, wherein said bulk fuel material has
a density of about 55 pounds per cubic foot or greater.
41. A composition of a bulk fuel material, as claimed in
claim 40, wherein the bulk fuel material is coal.
S
42. A composition of a bulk fuel material, as claimed in
claim 41, wherein the coal is selected from the group
consisting of bituminous coal, sub-bituminous coal and
lignite.
38. A bulk fuel material, as claimed in claim 34, wherein
the bulk fuel material is coal.
39. A bulk fuel material, as claimed in claim 38, wherein
the coal is selected from the group consisting of bituminous
coal, sub-bituminous coal and lignite.
40. A composition of a bulk fuel material, comprising a
first amount of the bulk fuel material having a first particle
size range combined with a second amount of the bulk fuel
material having a second particle size range, wherein the
first and second particle size ranges are discontinuous and 10
wherein the combination of the first and second amounts has
PATENT NO.
DATED
INVENTOR(S)
UNITED STATES PATENT AND TRADEMARK OFFICE
CERTIFICATE OF CORRECTION
: 6,231,627 Bl
: May 15, 2001
: Reeves, et al.
Page 1 of 1
It is certified that error appears in the above-identified patent and that said Letters Patent is
hereby corrected as shown below:
Claim 29,
Line 1, following "claim", please insert -- 22 --.
Signed and Sealed this
Fourth Day of December, 200I
Attest:
Attesting Officer
NICHOLAS P. GOOleI
Acting Director ofthe United States Patent and Trademark Office