5,919,277
*Jul. 6, 1999
[11]
[45]
111111111111111111111111111111111111111111111111111111111111111111111111111
US005919277A
Patent Number:
Date of Patent:
United States Patent [19]
Reeves et al.
Related U.S. Application Data
[73] Assignee: Hazen Research, Inc., Golden, Colo.
[54] METHOD TO REDUCE OXIDATIVE
DETERIORATION OF BULK MATERIALS
[56] References Cited
U.S. PATENT DOCUMENTS
ABSTRACT
1/1989 Siddoway et al. 44/501
5/1989 Bellow, Jr. et al. 44/501
5/1989 Bixel et al. 44/501
2/1992 Cha et al. 44/501
3/1998 Reeves et al. 44/501
4,797,136
4,828,575
4,828,576
5,087,269
5,725,613
[57]
OTHER PUBLICATIONS
Edwards, 1995, Catalysis Today, 23:59-66.
Keirn, "Industrial Uses of Carbon Dioxide", in Carbon
Dioxide as a Source o/Carbon, M.Aresta and G. Forti, eds.,
D. Reidel Publishing Co., 1987, 23-31.
Rigsby et aI., "Coal self-heating: problems 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.
Primary Examiner-Ellen M. McAvoy
Attorney, Agent, or Firm---8heridan Ross P.e.
33 Claims, No Drawings
Disclosed is a method to reduce oxidative deterioration of
bulk materials. Preferred embodiments of bulk materials
include solid fuel materials, such as coal, and bulk food
products. The method includes contacting a bulk material
with a heat transfer medium to reduce the temperature of the
bulk material below ambient temperature, and preferably
below about 10° e. In this manner, the rate of oxidation is
sufficiently low so that significant losses, such as the loss of
thermal values in of fuel material, are avoided. The heat
transfer medium can be solid or fluid and in a preferred
embodiment is liquid carbon dioxide or liquid nitrogen.
This patent is subject to a terminal disclaimer.
4/1966 Ellman et al. 34/9
4/1978 Das 44/620
10/1979 Smith 44/1
8/1983 Li et al. .. 44/1
8/1983 Bonnecaze .. 44/1
4/1985 Nakamura et al. 44/501
7/1986 Cargle et al. 427/220
9/1986 Chiang et al. 209/5
3/1987 Yan 44/1
3,243,889
4,083,940
4,170,456
4,396,394
4,401,436
4,511,363
4,599,250
4,613,429
4,650,495
[ *] Notice:
[75] Inventors: Robert A. Reeves, Arvada; Charlie W.
Kenney, Littleton; Mark H. Berggren,
Golden, all of Colo.
[63] Continuation-in-part of application No. 08/677,637, Jul. 8,
1996, Pat. No. 5,725,613.
[51] Int. CI.6 C10L 9/00
[52] U.S. CI. 44/501; 44/591; 44/592;
44/620
[58] Field of Search 44/501
[21] AppI. No.: 08/995,710
[22] Filed: Dec. 22, 1997
5,919,277
2
DETAILED DESCRIPTION
The present invention concerns a method to reduce oxidative
deterioration of bulk materials. The term "bulk materials"
refers to any solid materials which are produced,
shipped and/or stored in quantities measured on a tonnage
basis, and preferably includes oxidizable and highly reactive
60 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 which is combusted for some useful purpose.
65 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
55
gilsonite, distillation by-products, wood by-product wastes,
shredded tires, peat and waste pond coal fines.
The method includes directly contacting the bulk material
with a heat transfer medium to reduce the temperature of the
bulk material below an ambient temperature. In a preferred
embodiment, the temperature of the bulk material is reduced
to below about 10° C. In this manner, significant oxidative
deterioration of the bulk material is avoided. In the instance
of a solid fuel material, for example, loss of the thermal
10 value of the solid fuel material is reduced because the rate
of oxidative deterioration significantly slows with cooler
temperatures. Significant reductions in the rate of loss of
heating value can be attained for solid fuel material. For
example, fuel materials treated with the method of the
15 present invention can have a rate of loss of heating value of
less than about 0.5% per month.
The heat transfer medium can be solid, liquid or gas and
is substantially inert to the bulk material. In preferred
embodiments, the heat transfer medium can be carbon
dioxide, carbon monoxide, helium, nitrogen, argon or air. In
20 preferred embodiments, the heat transfer medium is carbon
dioxide or nitrogen, in particular, liquid and solid carbon
dioxide and liquid nitrogen.
The present invention includes conducting the process of
contacting a bulk material with a heat transfer medium at a
25 variety of times throughout the product life of the bulk
material. For example, the process can be conducted during
time periods when the bulk material is subject to a high
degree of mixing such as during size reduction steps and/or
loading or unloading of the bulk material. In an alternative
30 embodiment, the step of contacting the bulk material with
the heat transfer medium can be conducted while the bulk
material is in a static state, such as in a storage pile.
In another embodiment of the present invention, the
method to reduce oxidative deterioration of solid fuel mate-
35 rial includes forming a storage mass of the solid fuel
material. The storage mass has an exterior surface and an
interior volume located below the exterior surface. At least
a portion of the interior volume of the storage mass is
contacted with a heat transfer medium to reduce the tem-
40 perature or cool the interior volume below about 10° C.
In yet another embodiment, the method includes introducing
the solid fuel material into a vessel in which a
gaseous heat transfer medium is caused to flow through the
solid fuel material. In this manner, the solid fuel material is
45 fluidized in the flow of gaseous heat transfer medium, and at
least a portion of the solid fuel material is reduced to a
temperature below about 10° C.
Further embodiments of the present invention include
compositions which have been produced by conducting the
50 method of the present invention. Such compositions, for
example, include bulk materials in direct contact with a heat
transfer medium having temperatures within ranges according
to the method of the present invention.
RELATED APPLICATIONS
FIELD OF THE INVENTION
SUMMARY OF THE INVENTION
BACKGROUND OF THE INVENTION
1
METHOD TO REDUCE OXIDATIVE
DETERIORATION OF BULK MATERIALS
The present invention includes a method to reduce oxidative
deterioration of bulk materials, particularly including
oxidizable and highly reactive bulk materials. In preferred
embodiments, the bulk materials in question include solid
fuel materials, bulk food products, sulfide ores and carbon
containing 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
biomass materials, refuse-derived (including municipal and
reclaimed refuse) fuels, coke, char, petroleum coke,
The present invention relates to a method and composition
for reducing the oxidative deterioration of bulk materials.
In particular, the invention relates to reduction of
oxidative deterioration of solid fuel materials, such as coal.
When bulk materials contact the ambient environment,
they are subject to oxidative deterioration because of contact
with oxygen in 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 on 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
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 and as such a reaction progresses,
there is a significant risk of certain coal materials selfigniting,
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,
significant reductions in coal surface area which contact the
ambient environment can be attained. 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 hydrocarbonbased
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.
5 This application is a continuation-in-part application of
U.S. patent application Ser. No. 08/677,637 filed on Jul. 8,
1996, now U.S. Pat. No. 5,725,613.
5,919,277
3 4
rate of oxidation of the bulk material at various
temperatures, the cost of the heat transfer medium, and the
effects of extraneous factors on the product such as material
handling protocols.
The heat transfer medium of the present invention can be
solid or fluid (i.e., liquid or gas). The heat transfer medium
is essentially non-oxidizing to the bulk material. It should be
noted that when considering whether the heat transfer
medium is non-oxidizing with regard to the bulk material,
the temperature of the heat transfer medium must be considered.
For example, warm air may be overly reactive with
some bulk materials, such as coal, but if the heat transfer
medium is cold air (e.g., 4° C.), the degree of reactivity with
the coal may be acceptably low to be considered nonoxidizing.
Preferably, to be considered non-oxidizing, the
15 heat transfer medium of the present invention should not
oxidize the product or cause the product to become more
reactive to oxygen at a time subsequent to treatment with the
heat transfer medium. In a further embodiment, the heat
transfer medium can be inert (i.e., non-reactive) to the bulk
material.
The heat transfer medium needs to be sufficiently cold so
that the temperature of the bulk material, prior to contact
with the heat transfer medium, can be reduced to within the
appropriate temperature range after contact. In a preferred
25 embodiment, the temperature of the heat transfer medium
prior to contact with the bulk material medium is less than
about _30° c., more preferably less than about _50° C. and
most preferably less than about -70° C.
The heat transfer medium can comprise carbon dioxide,
carbon monoxide, helium, nitrogen, argon, or air. More
preferably, the heat transfer medium can comprise carbon
dioxide, carbon monoxide, nitrogen or argon. In a preferred
embodiment, the heat transfer medium can comprise either
nitrogen or carbon dioxide. In a further preferred
embodiment, the heat transfer medium can comprise liquid
or solid carbon dioxide or liquid nitrogen. It will be recognized
that for a liquid or solid heat transfer medium which
is a gas at ambient temperatures of the bulk material, as the
heat transfer medium heats up, it will change phase to
become a gas. Such an evolution of gas over time, such as
40 the evolution of carbon dioxide gas from solid carbon
dioxide, has the benefit of excluding oxygen from contacting
the bulk material.
It will be appreciated that in the instance of a solid heat
transfer medium, smaller particle sizes will allow more
uniform cooling than for larger particle sizes. In the instance
of a solid heat transfer medium, the particle size of the
medium is preferably less than about 5 millimeter, more
preferably less than about 3 millimeter and most preferably
less than about 0.5 millimeter.
The step of contacting includes bringing the heat transfer
medium and the bulk material into sufficiently intimate
contact such that the bulk material is cooled to the desired
temperature. For example, as discussed in more detail below,
the heat transfer medium may be introduced into the interior
portion of a storage mass of bulk material and directly
contacted with the bulk material. By contacting the bulk
material directly with the heat transfer medium, the heat
transfer which occurs to cool the bulk material is more
efficient than through an indirect heat transfer. Since the heat
transfer medium is not confined within, for example, tubes
60 of a heat exchanger, a more complete, effective and uniform
cooling of the bulk material can be achieved. Specific
preferred methods for contacting the heat transfer medium
with the bulk material are described in detail below.
It will be understood that the amount of heat transfer
medium needed to cool a given amount of bulk material will
depend on various factors, including the relative temperatures
of each. However, in a preferred embodiment, the
and lignite. The present invention is particularly suited for
bituminous coal, sub-bituminous coal and lignite. The term
upgraded coal product includes thermally-upgraded coal
products, coal products produced by beneficiation based
upon specific gravity separation, mechanically cleaned coal 5
products, and sized 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 10
which increases 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 rewet, 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 by-products, wood by-product wastes, 20
shredded tires, peat and waste pond coal fines. The term
solid biomass can include, for example, wood wastes, agricultural
wastes, and grass. The term refuse-derived fuels can
include, for example, landfill material from which noncombustible
materials have been removed.
In one 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 has concentrated on preservation of
high-end food products such as meats, dairy and vegetables, 30
there remains a need in the industry for low cost, effective
preservation of bulk food products such as bulk grains and
related by-products. According to the present invention, bulk
food products can include bulk grains, animal feed and
related by-products. Examples of such bulk grains include,
but are not limited to wheat, corn, soybeans, barley, oats, and 35
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.
The present method includes directly contacting the bulk
material with a heat transfer medium to reduce the temperature
of the bulk material below ambient temperature. The
term ambient can refer to the temperature of the environment
in which the bulk material is produced, shipped and/or 45
stored. Alternatively, such term can include the temperature
at which the material existed prior to production. For
example, the temperature of coal in the earth is relatively
constant and will vary between about 10° C. and about 16°
C. In a preferred embodiment, the method of the present 50
invention includes reducing the temperature of the bulk
material with a heat transfer medium to below about 10° c.,
preferably below about 5° c., more preferably below about
3° c., and even more preferably between about O°c. and
about 3° C. According to the present invention, reference to
the temperature of the bulk material can include the tem- 55
perature of an interior, such as the core of the material,
and/or a surface portion of the material. More particularly,
the temperature of the bulk material can refer to the temperature
of a portion of the material which is or can be in
contact with air or oxygen.
The appropriate temperature for cooling a bulk material
by contact with a heat transfer medium pursuant to the
present invention is selected such that unacceptable levels of
oxidative deterioration and/or self-heating are avoided. The
determination of the appropriate temperature may depend on 65
a variety of factors, including the nature of the bulk material,
the available time until consumption (i.e. storage time), the
5,919,277
5 6
effectiveness of reducing oxidative deterioration can be
employed. For example, a reduction in the concentration of
micro-organisms on grain could be used as a measurement
of the effectiveness of reducing oxidative deterioration in the
5 grain. The effectiveness of reducing oxidative deterioration
in a bulk food product could also be measured as a percentage
of spoilage of the food product over a given period of
time.
In a further preferred embodiment of the present invention
10 where the heat transfer medium is not air, the step of
contacting the bulk material with a heat transfer medium
displaces ambient air from contact with the bulk material. In
this manner, the available oxygen for oxidation of the bulk
material is reduced.
In a further preferred embodiment of the present
invention, the heat transfer medium reacts with the surface
of the solid fuel material to passivate the solid fuel material
from oxidation by ambient air. Such a heat transfer medium
can, for instance, form new compounds on the surface of the
20 solid fuel material such that the surface is inactive, or less
reactive to oxidation by ambient air.
Methods of the present invention, including contacting a
bulk material with a heat transfer medium, can be conducted
25 at any time in the product life of the bulk material in question
to reduce oxidative deterioration in the future. For example,
in the case of solid fuel material such as coal, the step of
contacting can be conducted at any time from when the fuel
is removed from the ground or otherwise produced, until it
30 is ultimately consumed at a utility.
The method of contacting a bulk material with a heat
transfer medium can be is preferably conducted at a point in
the product life of the bulk material when the bulk material
is subject to a high degree of mixing or agitation for some
35 other purpose. In this manner, efficient contact of the bulk
material with the heat transfer medium can occur without the
added requirement of inducing substantial mixing or agitation
solely for the purpose of contact with the heat transfer
medium. In one embodiment, the step of contacting can
40 occur when the particle size of a bulk material is being
reduced. For example, in the instance of a solid fuel material
such as coal, the step of contacting can be conducted at the
mine at which the coal is recovered. Such a step of contacting
is advantageously conducted when run-of-mine coal is
45 initially crushed. As the run-of-mine coal is introduced into
a crusher, a stream of fluid heat transfer medium, preferably
liquid carbon dioxide or liquid nitrogen, can be introduced
at the same time. In this manner because the crusher induces
vigorous mixing of coal particles, intimate contact and
50 mixing of the heat transfer medium with the coal is also
achieved. In addition, or alternatively, a solid heat transfer
medium such as solid carbon dioxide can be introduced at a
mine location such as during a crushing step or subsequent
to the crushing as coal is loaded into a transport vehicle (i.e.,
55 rail car or barge).
Alternatively, the bulk material may be contacted with the
heat transfer medium in a vessel, in which a gaseous heat
transfer medium is caused to flow through the bulk material.
Thereby, the bulk material is fluidized or entrained in the
60 flow of the gaseous heat transfer medium. This contact of the
heat transfer medium and the bulk material reduces the
temperature of the bulk material in accordance with the
present invention. In this aspect of the invention, particle
size is important because smaller particles are more easily
65 entrained than larger sized particles. More particularly, particles
below about 0.5 millimeter are preferred. It should
also be noted that the vessel may be enclosed to capture the
amount of heat transfer medium to be contacted with a bulk
material will be between about 0.5 and about 10 weight
percent, more preferably between about 1 and about 5
weight percent, and even more preferably between about 1
and about 2 weight percent based on the weight of the bulk
material.
The step of contacting a bulk material with a heat transfer
medium of the present invention is preferably conducted
substantially in the absence of water. It will be recognized
that many bulk materials and heat transfer media contain
some naturally occurring water. Reference to conducting the
present process in the absence of water refers to no water
being introduced in addition to any moisture naturally
occurring in the bulk material or heat transfer media.
A preferred embodiment of the present invention further 15
includes maintaining the bulk material at a cooled temperature
as described above for a time of at least about one day,
more preferably at least about one month and more preferably
at least about six months. For example, by maintaining
such temperatures for such time periods, oxidative deterioration
can be reduced during processing, transport and
storage of bulk materials.
The method of the present invention which includes
contacting a bulk material with a heat transfer medium to
effectively reduce the temperature, can be used in combination
with other techniques for reducing oxidative deterioration
and/or self-heating. For example, methods of the
present invention can further include sizing the bulk material
by removing small particles therefrom. In this manner, the
effective surface area of the bulk material available as an
oxidative surface is decreased. More particularly, this step
can include removing particles of the bulk material having
a particle size of less than about 5 millimeter.
In addition, methods of the present invention can also
include the step of compacting the bulk material. In this
manner, the available surface area for contact with ambient
air is reduced. More particularly, the step can include
compacting the bulk material to a bulk density of greater
than about 700 kg/m3
, and more preferably to a bulk density
of greater than about 1000 kg/m3
.
Methods of the present invention will reduce the oxidative
deterioration of the bulk material in question. In the instance
where the bulk material is a solid fuel material, one measure
of the effectiveness of reducing oxidative deterioration is
measuring the rate of loss of the heating value of the fuel
material. For example, thermal loss can be measured by
comparing the moisture-ash-free heating value (MAP heating
value) of coal before and after storage. The MAP heating
value is computed by subtracting the dilution effects of
non-combustible ash and moisture from a heating value
measured on whole material by a laboratory calorimeter. The
MAP heating value is primarily a component of the hydrogen
and carbon in the coal. These two components are
oxidized to water vapor and carbon dioxide during storage.
Oxidation of hydrogen and carbon through low temperature
oxidation will reduce the MAP heating value.
In a preferred embodiment of methods of the present
invention, solid fuel material treated by methods of the
present invention has a rate of loss of heating value of less
than about 0.5% per month when stored at 2° C. in air, and
in a more preferred embodiment, the solid fuel material has
a rate of loss of heating value of less than about 0.1% per
month, and in a more preferred embodiment the solid fuel
material has a rate of loss of heating value of less than about
0.05% per month.
In the instance where the bulk material is a bulk food
product, such as bulk grain, other means of measuring the
5,919,277
7 8
TABLE 1
EXAMPLES
Rate of Oxygen Adsorption, k, for
24° C. and 0° C. Raw and Dried PRB Coal
Percent reduction
Sample 24° C. 0° C. by cooling
Raw PRB Coal 0.0081 0.0034 -58%
Dried PRB Coal 0.0138 0.0021 -85%
It will be noted that a reduction in the rate of oxygen
adsorption of 85% was achieved by cooling the dried coal
Example 1
This example evaluates the rate of oxygen adsorption of
coal at different temperatures as a model to evaluate the
effect of cooling on oxidative deterioration of fuel materials.
Four 100-gram samples of%-inch coal was obtained from
the Powder River Basin in Wyoming, U.S.A. Two of the
samples were dried for 16 hours under a warm inert nitrogen
atmosphere to reduce the moisture content of the coal from
approximately 27% to 6.27%. The remaining two samples
were not thermally treated. The samples contained, on a dry
basis, 7% ash, 44% volatile matter, 71% carbon, 4.8%
hydrogen, 0.6% sulfur and 11,820 BTU/lb.
Each of the four samples of coal was placed in an airtight,
I-liter capacity, stainless steel test vessel. Each vessel was
fitted with an electronic solid-state pressure gauge capable
of measuring internal air pressure to within 0.015 psi, and a
septum fitting to allow air to be admitted to the vessel by
syringe. Two of the vessels were placed in a circulating
water bath maintained at 24°C. The other two vessels were
placed in an ice chest filled with ice and liquid water to
maintain the contents at 0° C. One of the dried samples was
placed in a 24°C. vessel and one in a 0° C. vessel. One
untreated sample was placed in a 24°C vessel and in a 0°
C. vessel. The initial pressures within each vessel were
adjusted to 760 mm Hg (1 atmosphere at sea level). Air
pressure readings were read twice a day for 72 hours. Air
pressure decreases were reflective of oxygen adsorption by
the coal. Thus, air pressure decreases simulated the tendency
of coal to oxidize and therefore, the loss of thermal heating
value. The rates of oxygen adsorption are shown below in
Table 1.
65
heat transfer medium is liquid and/or solid carbon dioxide.
In this embodiment, carbon dioxide is recovered from the
flue gases at a utility by conventional stripping technology.
The carbon dioxide is then liquefied or frozen solid and then
5 used, as described above, for contacting with coal or
upgraded coal product supplies which are incoming during
unloading from a transport vehicle or which are already in
storage.
Further embodiments of the present invention include
10 compositions which are produced by the processes of the
present invention. Such compositions include any of the
various bulk materials, as described above, which have been
contacted with an appropriate heat transfer medium, as
generally disclosed above, and cooled to a temperature
15 within the ranges as described above to reduce the oxidative
deterioration of the bulk material.
The following examples are provided for purposes of
illustration only and are not intended to limit the scope of the
invention.
heat transfer medium to be recirculated through the vessel.
Before recirculation, the heat transfer medium may need to
be cooled to a temperature to allow for adequate cooling of
the bulk material to a desired temperature.
In a further preferred embodiment, the heat transfer
medium can be contacted with a bulk material when the bulk
material is subject to any material handling or processing
operation, such as when being transferred from one storage
or transport apparatus to another, such as during loading or
unloading from or to a transport vehicle or a storage facility.
For example, in the case of coal, which is transported by rail
or barge, when it arrives at a utility the coal is either
immediately consumed or sent to short- or long-term storage.
In any event, as the coal is unloaded from the rail or
barge vehicle, it is typically unloaded in such a manner that
the solid particulate coal becomes temporarily dispersed. At
this point in the unloading process, it is an advantageous
time for contacting with the heat transfer medium because of
the high degree of mixing available to achieve intimate
contact and efficient cooling. Thus, a fluid and/or solid heat 20
transfer medium, such as liquid or solid carbon dioxide or
liquid nitrogen, can be introduced at this point in a material
transfer process. For example, coal is typically unloaded
from a barge by scraping the coal from the cargo hold by a
bucket elevator or clamshell and is loaded onto a conveyor. 25
At a transfer point, e.g., between two conveyors downstream
of the unloading process, a heat transfer medium such as
liquid carbon dioxide or liquid nitrogen can be added to the
coal before the coal is placed in storage.
In addition to conducting the method of the present 30
invention when the bulk material is subject to a high degree
of mixing or agitation, the step of contacting can be conducted
when the bulk material is static. For example, in the
instance of a solid fuel material, such as coal, which is in a
storage pile, the method of the present invention can include 35
contacting the heat transfer medium with the coal while it is
in storage or otherwise in a static condition. When a solid
fuel material is in a storage pile, it constitutes a storage mass
having an exterior surface and an interior volume. Thus, the
interior volume is the internal portion of the storage mass 40
which is below the exterior surface of the mass. Such a step
of contacting can be achieved, for example, by inserting a
pipe or other distribution device into the interior volume of
the storage mass at various points throughout a storage mass
pile and injecting an appropriate amount of, for example, 45
liquid carbon dioxide or other heat transfer medium into the
interior volume of the storage mass until appropriate cooling
of the fuel material coal pile is attained. In addition, it should
be noted that other mechanisms for achieving contact
between a heat transfer medium and a static fuel material 50
storage mass can be used. For example, a fixed distribution
system, such as a network of pipes with nozzles or other
similar system can be constructed so that a storage mass can
be formed on top of the distribution system. For example, as
bulk material is unloaded from a transport vessel, it can be 55
unloaded onto such a fixed distribution system. At an
appropriate time, heat transfer medium can be released
through the distribution system to cool the storage mass.
In the case wherein the bulk material is a bulk food
product, addition of a heat transfer medium is ideally 60
performed such that the food product is not crushed or
damaged. Therefore, the heat transfer medium can be contacted
with the bulk food product by adding such heat
transfer medium at a material handling transfer point during
the shipping and unloading of the food product.
In a further preferred embodiment, in the instance of solid
fuel materials, such as coal or upgraded coal products, the
5,919,277
9 10
* * * * *
25
17. A method, as claimed in claim 1, wherein said step of
contacting said heat transfer medium displaces ambient air
from contact with said solid fuel material.
18. A method, as claimed in claim 1, wherein said heat
transfer medium reacts with the surface of said solid fuel
material to passivate said solid fuel material from oxidation
by ambient air.
19. A method, as claimed in claim 1, wherein said step of
contacting said heat transfer medium reduces condensation
10 on said exterior surface of said storage mass.
20. A method, as claimed in claim 1, wherein said step of
forming comprises placing said solid fuel material around a
fluid outlet such that said fluid outlet is within said interior
volume and wherein said step of contacting comprises
flowing said heat transfer medium through said fluid outlet.
21. A method, as claimed in claim 1, wherein said fluid
outlet comprises multiple openings.
22. A method, as claimed in claim 1, wherein said step of
contacting comprises inserting a fluid outlet through said
exterior surface and into said interior volume and flowing
said heat transfer medium through said fluid outlet.
23. A method to reduce the oxidative deterioration of
particulate solid fuel material, said method comprising the
steps of:
introducing said solid fuel material into a vessel;
flowing a gaseous heat transfer medium through said solid
fuel material to fluidize said solid fuel material and to
reduce a temperature of at least a portion of said solid
fuel material below about 10° C.
24. A method as claimed in claim 23, wherein the temperature
of at least a portion of said solid fuel material is
reduced to below about 5° C.
25. A method, as claimed in claim 23, wherein the
35 temperature of at least a portion of said solid fuel material
is reduced to be between about 0° C. and about 3° C.
26. A method, as claimed in claim 23, wherein said solid
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.
27. A method, as claimed in claim 23, wherein said solid
fuel material comprises coal and wherein said coal is
selected from the group consisting of bituminous coal,
sub-bituminous coal and lignite.
28. A method, as claimed in claim 23, wherein said solid
fuel material is an upgraded coal product and wherein said
upgraded coal product is selected from the group consisting
of thermally upgraded products, products beneficiated by
specific gravity separation, mechanically cleaned coal products
and sized coal products.
29. A method, as claimed in claim 23, wherein said
gaseous heat transfer medium is selected from the group
consisting of carbon dioxide, carbon monoxide, helium,
nitrogen, argon and air.
30. A method, as claimed in claim 23, wherein said
gaseous heat transfer medium comprises nitrogen.
31. A method, as claimed in claim 23, wherein said solid
fuel material has a rate of loss of heating value of less than
about O.5%/month.
32. A method, as claimed in claim 23, wherein said solid
fuel material has a rate of loss of heating value of less than
about 0.1%/month.
33. A method, as claimed in claim 23, wherein said solid
fuel material has a rate of loss of heating value of less than
about 0.05%/month.
from 24° C. to 0° C. Similarly, a 58% reduction was seen
with the untreated raw coal. This example illustrates that
significant reductions in oxidative deterioration of fuel materials
can be achieved by practice of the present invention.
While various embodiments of the present invention have 5
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 solid fuel
material, said method comprising the steps of:
forming a storage mass comprising said solid fuel
material, said storage mass having an exterior surface
and an interior volume located below said exterior 15
surface;
contacting said interior volume of said storage mass with
a heat transfer medium to cool at least a portion of said
interior volume to below about 10° C.
2. A method as claimed in claim 1, wherein the tempera- 20
ture of at least a portion of said interior volume is cooled to
below about 5° C.
3. A method, as claimed in claim 1, wherein the temperature
of at least a portion of said interior volume is cooled to
between about 0° C. and about 3° C.
4. A method, as claimed in claim 1, wherein said solid 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 30
tires, peat and waste pond coal fines.
5. A method, as claimed in claim 1, wherein said solid fuel
material comprises coal and wherein said coal is selected
from the group consisting of bituminous coal, subbituminous
coal and lignite.
6. A method, as claimed in claim 1, wherein said solid fuel
material is an upgraded coal product and wherein said
upgraded coal product is selected from the group consisting
of thermally upgraded products, products beneficiated by
specific gravity separation, mechanically cleaned coal products
and sized coal products. 40
7. A method, as claimed in claim 1, wherein said heat
transfer medium is selected from the group consisting of
carbon dioxide, carbon monoxide, helium, nitrogen, argon
and air.
8. A method, as claimed in claim 1, wherein said heat 45
transfer medium is selected from the group consisting of
carbon dioxide, carbon monoxide, nitrogen and argon.
9. A method, as claimed in claim 1, wherein said heat
transfer medium comprises carbon dioxide.
10. A method, as claimed in claim 1, wherein said heat 50
transfer medium comprises liquid carbon dioxide.
11. A method, as claimed in claim 1, wherein said heat
transfer medium comprises solid carbon dioxide.
12. A method, as claimed in claim 1, wherein said heat
transfer medium comprises liquid nitrogen. 55
13. A method, as claimed in claim 1, further comprising
removing particles of said solid fuel material having a
particle size of less than about 5 millimeters before said step
of forming.
14. A method, as claimed in claim 1, wherein said solid
fuel material has a rate of loss of heating value of less than 60
about O.5%/month.
15. A method, as claimed in claim 1, wherein said solid
fuel material has a rate of loss of heating value of less than
about 0.1%/month.
16. A method, as claimed in claim 1, wherein said solid 65
fuel material has a rate of loss of heating value of less than
about 0.05%/month.