U.S. patent application number 14/384570 was filed with the patent office on 2015-02-05 for inhibition of spontaneous combustion in low-rank coals.
The applicant listed for this patent is Benetech, Inc.. Invention is credited to Christopher F. Blazek, Michael T. Such, Andrew R. Wolff.
Application Number | 20150033619 14/384570 |
Document ID | / |
Family ID | 49161861 |
Filed Date | 2015-02-05 |
United States Patent
Application |
20150033619 |
Kind Code |
A1 |
Wolff; Andrew R. ; et
al. |
February 5, 2015 |
Inhibition of Spontaneous Combustion in Low-Rank Coals
Abstract
A method for treating coal to reduce spontaneous combustion by
reducing an exothermic heat of adsorption after the coal has begun
to dry and when the coal is subsequently exposed to a liquid water
is described. A source of a fluid pressure of a diluted hydrocarbon
mixture is provided. A hydrocarbon in the mixture is a hydrocarbon
emulsion of mineral when the coal is subsequently exposed to a
liquid water oil, fuel oil, asphalt, or coal tar emulsions. A
volume of the diluted hydrocarbon mixture is applied to a stream of
freshly-mined and undried coal to provide a water-proofing of the
coal to prevent water uptake after exposure to precipitation or
flooding during transport and storage of the coal. The treated coal
is loaded into a bulk pile. A temperature change trend in the bulk
pile is reversed wherein a temperature of the bulk pile trends
towards an ambient temperature rather than trending to a
temperature higher than the ambient temperature.
Inventors: |
Wolff; Andrew R.; (Darien,
IL) ; Blazek; Christopher F.; (Oswego, IL) ;
Such; Michael T.; (Woodridge, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Benetech, Inc. |
Aurora |
IL |
US |
|
|
Family ID: |
49161861 |
Appl. No.: |
14/384570 |
Filed: |
March 15, 2013 |
PCT Filed: |
March 15, 2013 |
PCT NO: |
PCT/US13/32227 |
371 Date: |
September 11, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61611213 |
Mar 15, 2012 |
|
|
|
Current U.S.
Class: |
44/620 |
Current CPC
Class: |
C10L 2290/18 20130101;
C10L 2250/08 20130101; C10L 9/10 20130101; C10L 2290/20 20130101;
C10L 2230/08 20130101; C10L 2200/0438 20130101; C10L 5/04 20130101;
C10L 2230/14 20130101; C10L 2200/0272 20130101; C10L 10/02
20130101; C10L 2290/08 20130101 |
Class at
Publication: |
44/620 |
International
Class: |
C10L 5/04 20060101
C10L005/04; C10L 10/02 20060101 C10L010/02 |
Claims
1. A method for treating coal to reduce spontaneous combustion by
reducing an exothermic heat of adsorption after the coal has begun
to dry and when the coal is subsequently exposed to a liquid water
comprising the steps of: providing a source of a fluid pressure of
a hydrocarbon; and applying the hydrocarbon to a stream of
coal.
2. The method of claim 1 wherein the hydrocarbon is a hydrocarbon
emulsion.
3. The method of claim 2 wherein a low-level amount of the
hydrocarbon emulsion is applied to the coal as a percentage of a
weight of the coal.
4. The method of claim 3 wherein the hydrocarbon emulsion is
selected from the group consisting of: mineral oil, fuel oil,
asphalt, and coal tar emulsions.
5. The method of claim 4 wherein the coal is freshly-mined and
un-dried.
6. The method of claim 5 wherein the hydrocarbon emulsion reduces
self-heating of the coal caused by exothermic heat of
absorption.
7. A method for treating coal to reduce spontaneous combustion by
reducing an exothermic heat of adsorption after the coal has begun
to dry and when the coal is subsequently exposed to a liquid water
comprising the steps of: providing a source of a fluid pressure of
a silicone; and applying the silicone to a stream of coal.
8. The method of claim 7 wherein the silicone is a silicone
emulsion.
9. The method of claim 8 wherein a low-level amount of the silicone
emulsion is applied to the coal as a percentage of a weight of the
coal.
10. A method for treating coal to reduce spontaneous combustion by
reducing an exothermic heat of adsorption after the coal has begun
to dry and when the coal is subsequently exposed to a liquid water
comprising the steps of: providing a source of a fluid pressure of
a silane; and applying the silane to a stream of coal.
11. The method of claim 10 wherein a low-level amount of the silane
is applied to the coal as a percentage of a weight of the coal.
12. A method for treating coal to reduce spontaneous combustion by
reducing an exothermic heat of adsorption after the coal has begun
to dry and when the coal is subsequently exposed to a liquid water
comprising the step of waterproofing a freshly-mined coal to
prevent water uptake after exposure to precipitation or flooding
during transport and storage of the freshly-mined coal.
13. The method of claim 12 further comprising the steps of:
providing a source of a fluid pressure of a hydrocarbon; and
applying the hydrocarbon to a stream of freshly-mined and undried
coal.
14. The method of claim 13 wherein the applying step includes
application of a low-level amount of the hydrocarbon as a
percentage of the weight of the coal.
15. The method of claim 14 wherein the hydrocarbon is a hydrocarbon
emulsion.
16. The method of claim 15 wherein the low-level amount of the
hydrocarbon emulsion is not more than 2 lb (0.9 kg) per ton of the
coal.
17. The method of claim 16 wherein the hydrocarbon emulsion is
diluted in liquid water prior to the applying step.
18. The method of claim 17 wherein a diluted mixture of the
hydrocarbon emulsion and the liquid water contains less than 80
parts liquid water.
19. The method of claim 18 wherein the diluted mixture contains
between 19 and 79 parts liquid water.
20. The method of claim 19 wherein an application rate of the
diluted mixture is 2.5 to 10 gallons of diluted mixture per ton of
freshly-mined and undried coal.
21. The method of claim 20 wherein the hydrocarbon emulsion is
selected from the group consisting of: mineral oil, fuel oil,
asphalt, and coal tar emulsions.
22. The method of claim 21 further comprising the step of:
developing a water repellency of the freshly-mined and undried coal
by allowing the coal to dry under ambient conditions.
23. The method of claim 21 further comprising the steps of: loading
the freshly-mined and undried coal into a bulk pile subsequent to
the applying step; and reversing a temperature change trend in the
bulk pile wherein a temperature of the bulk pile trends towards an
ambient temperature rather than trending to a temperature higher
than the ambient temperature.
24.-36. (canceled)
Description
TECHNICAL FIELD
[0001] The invention relates to coal mining as well as transport
and storage of coal, and more particularly, the invention relates
to a method for treating coal to reduce or prevent spontaneous
combustion by reducing the exothermic heat of adsorption after the
coal has begun to dry and when the coal is subsequently exposed to
liquid water.
BACKGROUND OF THE INVENTION
[0002] The spontaneous combustion of coal is a serious problem for
utilities, both during transport and on-site handling. In addition
to the loss of fuel, attempting to handle ignited coal can initiate
combustion events that lead to the detonation of coal dust, forcing
utilities to shut down for weeks to months with losses from
electricity generating revenue and additional costs from
construction to replace the destroyed infrastructure.
[0003] The problem of spontaneous combustion has been recognized
for many decades. U.S. Pat. No. 2,184,621 (Marmaduke, 1938) cites
coal's ability to spontaneously ignite and proposes a remedy of
encapsulating the coal in a plasticized wax treatment. More
recently, the issue has been addressed by encapsulating the coal in
layers of silicon dioxide (Kindig et al., U.S. Pat. No. 3,961,914),
high molecular weight polyethylene glycol (Burns, U.S. Pat. No.
4,331,445), latex (Matthews, U.S. Pat. No. 4,421,520),
pre-oxidizing the coal with a chemical oxidizer (Rogers et al.,
U.S. Pat. No. 4,759,772), or, more recently, treating the coal with
a polymeric cationic surfactant (Roe, U.S. Pat. No. 5,576,056).
[0004] In addition to attempting to treat the coal surface, the
problem of spontaneous combustion has been approached by attempting
to inert the coal surface with carbon dioxide (Smith, U.S. Pat. No.
4,199,325), by drying and partially oxidizing then hydrating the
coal (Seitzer, U.S. Pat. No. 3,723,079), by drying the coal and
briquetting it (Kubota et al., U.S. Pat. No. 4,645,513), by drying
and then sealing the coal with a hydrocarbon oil or wax (Johnson,
U.S. Pat. No. 3,985,517; Bixel et al., U.S. Pat. No. 4,783,199 and
4,828,576), by pulverizing and drying the coal while removing the
ash and then binding the particles with coal tar (Knudson et al.,
U.S. Pat. No. 5,162,050), and by pulverizing, drying, and sealing
the coal particles with mineral oil (Dunlop et al., U.S. Pat. No.
6,162,265) or a mixture of oil and molasses (Rahm et al., U.S. Pat.
No. 6,086,647).
[0005] Finally, two patents have taught that management of the coal
pile itself to decrease air penetration reduce the likelihood of
spontaneous combustion (Behringer, U.S. Pat. No. 4,472,102 and
Reeves et al., U.S. Pat. No. 6,231,627).
[0006] The conventional wisdom is that spontaneous combustion of
low-rank coal is an oxidation process. Indeed, at higher
temperatures it is exactly that. However, at or near room
temperature the rate of oxidation of coal is very slow.
Interestingly, spontaneous combustion of coal piles occurs most
frequently during wet weather, especially wet weather following a
dry spell. In the 1990's, significant research was carried out on
the role water played in the initial heating of coal. A thorough
review was published in 2001: "The Influence of Moisture on the
Spontaneous Combustion of Coal" Christopher Blazek, Benetech
Report. The report highlighted several additional sources of heat
that can occur in a coal pile. Among them, the heat of condensation
and the heat of adsorption provide significant thermal energy to
the coal particle. Of course, the reverse of these processes would
provide an equal amount of thermal cooling, provided the particle
remains unchanged. In the case of sub-bituminous and lignite coals
this is not the case. Sub-bituminous coal can contain up to 30%
moisture incorporated into the coal body. As such, it is an
integral structural component of the coal particle. Drying the
coal, whether through natural or artificial processes, causes the
coal's structure to break down. It is this phenomena that accounts
for the notorious dustiness of Powder River Basin (PRB) and other
sub-bituminous coals. In the process of breaking down, an
irreversible change occurs to the coal. It fragments. As it
fragments, its surface area increases.
[0007] To illustrate this consider a cube of freshly-mined
sub-bituminous coal. Its initial surface area is 6 units, that is,
it is a cube of unit length, width, and depth. As it dries it loses
water and eventually fragments. Let us say that it has now split
evenly into eight pieces, that is, it is now eight cubes of half
unit length, width, and depth, and each will now have a surface
area of 1.5 units, for a total surface area of 12 units. Its water
content has dropped to 15%. Its mass is now 0.85 kg. Suppose now
that the 150 grams of water is returned to the coal. The
endothermic heat of evaporation and the exothermic heat of
condensation will offset each other. However, the heat of
desorption and the heat of adsorption are proportional to the
surface area of the coal and that has changed. The heat of
adsorption will now be approximately twice as great as the heat of
desorption. The net effect will be heating of the coal particles.
This low-temperature heating of the coal via the heat of
adsorption, also called the heat of wetting or the heat of
immersion, can heat the coal from a temperature where the rate of
oxidation is too low to support a self-sustaining reaction to a
temperature where oxidation can become self-sustaining. In other
words, this heat of adsorption can act as the match to light a coal
pile fire.
[0008] It is therefore important to understand the previous work on
waterproofing treatments for coal. Notably, in addition to the
teachings in the Johnson, Bixel, Knudson, and Dunlop patents that
were used to waterproof dried, pulverized coal, sodium silicate and
sugar were used to produce hard waterproof briquettes of bituminous
coal powder as taught by Miller (Miller, U.S. Pat. No. 1,670,865),
a mixture of residual fuel oil (decant oil) and asphalt was applied
to lignite, and specifically dried lignite (Anderson, U.S. Pat. No.
4,201,657), in a two-step process as-mined coal is treated with a
pile-sealing coating of wetting agent and asphalt (Shaw et al.,
U.S. Pat. No. 4,264,333), dried coal was treated with petroleum
resin cut with a variety of oils for use as a dust control formula
(Wajer et al., U.S. Pat. No. 5,192,337), and finally a pulverized
coal slurry was treated with mineral oil emulsions to agglomerate
and reduce dusting (Roe, U.S. Pat. No. 5,256,169).
[0009] To summarize the prior art, spontaneous combustion
inhibition for un-dried coal was claimed for treatments composed of
a variety of oil, coal tar, latex, high molecular weight
polyethylene glycols, and asphalt compositions applied neat at a
minimum rate of 0.5 gallons (about 4 pounds) per ton. The
literature draws a sharp distinction between fresh-mined coal and
the more reactive dried low-grade coal. Comparatively little
attention has been given to preventing spontaneous combustion
during handling and transport of fresh-mined coal. In addition,
coal producers are sensitive to the price of coal treatments and
even half a gallon of pure mineral oil, fuel oil, or coal tar per
ton would represent a significant economic consideration to a mine
that produces millions of tons of coal per year.
[0010] The present invention is provided to solve the problems
discussed above and other problems, and to provide advantages and
aspects not provided by prior methods of inhibiting the spontaneous
combustion of low-rank coals. A full discussion of the features and
advantages of the present invention is deferred to the following
detailed description, which proceeds with reference to the
accompanying drawings.
SUMMARY OF THE INVENTION
[0011] A first aspect of the present invention is directed to a
method for treating coal to reduce spontaneous combustion by
reducing an exothermic heat of adsorption after the coal has begun
to dry and when the coal is subsequently exposed to a liquid water.
The method comprises the steps of: providing a source of a fluid
pressure of a hydrocarbon; and applying the hydrocarbon to a stream
of coal.
[0012] This aspect of the present invention may include one or more
of the following features, alone or in any reasonable combination.
The hydrocarbon may be a hydrocarbon emulsion. A low-level amount
of the hydrocarbon emulsion may be applied to the coal as a
percentage of a weight of the coal. The hydrocarbon emulsion may be
selected from the group consisting of: mineral oil, fuel oil,
asphalt, and coal tar emulsions. The coal may be fresh-mined and
un-dried. The hydrocarbon emulsion may reduce self-heating of the
coal caused by exothermic heat of absorption.
[0013] A second aspect of the present invention is directed to a
method for treating coal to reduce spontaneous combustion by
reducing an exothermic heat of adsorption after the coal has begun
to dry and when the coal is subsequently exposed to a liquid water.
The method comprises the steps of: providing a source of a fluid
pressure of a silicone; and applying the silicone to a stream of
coal.
[0014] This aspect of the present invention may include one or more
of the following features, alone or in any reasonable combination.
The silicone may be a silicone emulsion. A low-level amount of the
silicone emulsion may be applied to the coal as a percentage of a
weight of the coal.
[0015] A third aspect of the present invention is directed to a
method for treating coal to reduce spontaneous combustion by
reducing an exothermic heat of adsorption after the coal has begun
to dry and when the coal is subsequently exposed to a liquid water.
The method comprises the steps of: providing a source of a fluid
pressure of a silane; and applying the silane to a stream of
coal.
[0016] This aspect of the present invention may include one or more
of the following features, alone or in any reasonable combination.
A low-level amount of the silane may be applied to the coal as a
percentage of a weight of the coal.
[0017] A fourth aspect of the present invention is directed to a
method for treating coal to reduce spontaneous combustion by
reducing an exothermic heat of adsorption after the coal has begun
to dry and when the coal is subsequently exposed to a liquid water
comprising the step of waterproofing a freshly-mined coal to
prevent water uptake after exposure to precipitation or flooding
during transport and storage of the freshly-mined coal.
[0018] This aspect of the present invention may include one or more
of the following features, alone or in any reasonable combination.
The method may further comprise the steps of: providing a source of
a fluid pressure of a hydrocarbon; and applying the hydrocarbon to
a stream of freshly-mined and undried coal. The applying step may
include application of a low-level amount of the hydrocarbon as a
percentage of the weight of the coal. The hydrocarbon may be a
hydrocarbon emulsion. The low-level amount of the hydrocarbon
emulsion may be not more than 2 lb (0.9 kg) per ton of the coal
prior to dilution with water. The hydrocarbon emulsion may be
diluted in liquid water prior to the applying step. A diluted
mixture of the hydrocarbon emulsion and the liquid water may
contain less than 80 parts liquid water. The mixture may contain up
to 100 parts water. The diluted mixture may contain between 19 and
79 parts liquid water. An application rate of the diluted mixture
may be 2.5 to 10 gallons of diluted mixture per ton of
freshly-mined and undried coal. An application rate of the diluted
mixture may be as low as 0.5 gallons of diluted mixture per ton of
freshly-mined and undried coal. The applying step may be
accomplished using a pump and spray manifold on either side of the
stream of freshly-mined and undried coal. The hydrocarbon emulsion
may be selected from the group consisting of: mineral oil, fuel
oil, asphalt, and coal tar emulsions. The method may further
comprise the step of: developing a water repellency of the
freshly-mined and undried coal by allowing the coal to dry under
ambient conditions. The method may further comprise the steps of:
loading the freshly-mined and undried coal into a bulk pile
subsequent to the applying step; and reversing a temperature change
trend in the bulk pile wherein a temperature of the bulk pile
trends towards an ambient temperature rather than trending to a
temperature higher than the ambient temperature.
[0019] A fifth aspect of the present invention is directed to a
method for treating coal to reduce spontaneous combustion by
reducing an exothermic heat of adsorption after the coal has begun
to dry and when the coal is subsequently exposed to a liquid water.
The method comprises the steps of: providing a source of a fluid
pressure of a diluted hydrocarbon mixture wherein a hydrocarbon in
the diluted hydrocarbon mixture is a hydrocarbon emulsion chosen
from the group consisting of mineral oil, fuel oil, asphalt, and
coal tar emulsions, and the hydrocarbon emulsion; applying a volume
of the diluted hydrocarbon mixture to a stream of freshly-mined and
undried coal to provide a waterproofing of the freshly-mined and
undried coal to prevent water uptake after exposure to
precipitation or flooding during transport and storage of the
freshly-mined coal; loading the freshly-mined and undried coal into
a bulk pile subsequent to the applying step; and reversing a
temperature change trend in the bulk pile wherein a temperature of
the bulk pile trends towards an ambient temperature rather than
trending to a temperature higher than the ambient temperature.
[0020] This aspect of the present invention may include one or more
of the following features, alone or in any reasonable combination.
The hydrocarbon may be diluted with water such that the diluted
hydrocarbon mixture contains between 19 and 79 parts liquid water
by volume prior to the applying step. An application rate of the
diluted hydrocarbon mixture may be 2.5 to 10 gallons of diluted
hydrocarbon mixture per ton of freshly-mined and undried coal. A
low-level amount of the hydrocarbon may be applied to the
freshly-mined and undried coal in an amount no greater than 1 lb
(0.45 kg) per ton of the freshly-mined and undried coal.
[0021] A sixth aspect of the present invention is directed to a
method of improving the net energy content of a fuel exposed to
rain or flooding. This method comprises the step of: waterproofing
a fuel to prevent water uptake after exposure to precipitation or
flooding during transport and storage of the fuel.
[0022] This aspect of the present invention may include one or more
of the following features, alone or in any reasonable combination.
The method may further comprise the steps of: providing a source of
a fluid of a waterproofing agent, wherein the waterproofing agent
is selected from the group consisting of a hydrocarbon, a
hydrocarbon emulsion, a silicone, and a silane; and applying the
waterproofing agent to the fuel. A low-level amount of the
waterproofing agent may be applied to the fuel as a percentage of a
weight of the fuel. The hydrocarbon emulsion may be selected from
the group consisting of: mineral oil, fuel oil, asphalt, and coal
tar emulsions. The hydrocarbon emulsion may reduce self-heating of
the coal caused by exothermic heat of absorption. The fuel may be a
coal. The coal may be freshly-mined. The coal may be undried. The
fuel may be low-rank, sub-bituminous or lignite coal.
[0023] Other features and advantages of the invention will be
apparent from the following specification taken in conjunction with
the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] To understand the present invention, it will now be
described by way of example, with reference to the accompanying
drawings in which:
[0025] FIG. 1 is a flowchart of an aspect of the present
invention;
[0026] FIG. 2 is a flowchart of an aspect of the present
invention;
[0027] FIG. 3 is a flowchart of an aspect of the present invention;
and
[0028] FIG. 4 is a flowchart of an aspect of the present
invention.
DETAILED DESCRIPTION
[0029] While this invention is susceptible of embodiments in many
different forms, there is shown in the drawings and will herein be
described in detail preferred embodiments of the invention with the
understanding that the present disclosure is to be considered as an
exemplification of the principles of the invention and is not
intended to limit the broad aspect of the invention to the
embodiments illustrated.
[0030] Our invention is directed to a method for treating to reduce
or eliminate the likelihood spontaneous combustion. Treatment can
occur any time before the coal is subjected to spontaneous
combustion; however, in a preferred method fresh-mined and
specifically un-dried coal is treated to reduce or prevent
spontaneous combustion by reducing or preventing the exothermic
heat of adsorption after the coal has begun to dry and when the
coal is subsequently exposed to liquid water. This is accomplished
by treating the coal with a waterproofing agent such that when
exposed to water the water runs off and fails to adsorb onto or
into the coal particles, thus waterproofing the coal. Freshly-mined
in this context is coal that has not substantially lost its initial
water content.
[0031] The composition generally requires a water-proofing material
selected from polysiloxanes, silazanes, mineral oil, fuel oil, coal
tar, asphalt, petrolatum, vegetable-derived oils, animal-derived
oils, creosotes, tall oil pitch, petroleum pitch, petroleum resins,
and emulsions thereof. Other water-proofing compositions will be
apparent to those skilled in the art. The effective application
rate of these materials is considerably below the levels reported
in previous patents. For example, in one embodiment a mineral oil
emulsion was applied at 0.425 lbs (0.05 gallons) of mineral oil per
ton of coal and gave near-complete water-proofing of the coal. In
another case, a coal tar emulsion was applied at about 0.8 pounds
per ton of coal and gave coal that shed water and showed no
tendency to self-heat. The inventors contemplate that less than 2
lbs of an emulsion per ton of coal as described herein can be used
to treat a bulk load or pile of coal to arrive at suitable
reduction in spontaneous combustion of the coal under the
circumstances or chemical processes described herein. And, in an
example described herein, less than 1 lb per ton of the coal tar
itself can be used to treat the coal.
[0032] The waterproofing compositions of interest are, where
possible, aqueous emulsions of the above-mentioned water-proofing
materials. This is not to say that application of the pure
waterproofing product will not work. It is simply that emulsions
have several advantages over the pure material. First, being able
to be diluted in water allows effective coating of the coal surface
at a much lower application rate. Second, aqueous emulsions are not
combustible. Combustibility is an important consideration at any
mine of coal-handling facility as coal fires are a hazard and
storing a combustible material on site is not desirable.
[0033] It should be noted that water reduction in fuel subjected to
rain or flooding can also have significant benefits. Every kilogram
of water that goes into a boiler on the fuel costs about 2.3
megajoules in unrecoverable thermal energy. Thus, a 3% reduction in
moisture on a 19.5 MJ/kg (8400 BTU/lb) fuel will result in a
thermal energy gain of about 138 MJ/MT. Assuming a total plant
thermal to electrical energy conversion efficiency of about 35%,
that would be about another 13 kWh/MT of fuel. Thus, the teaching
of this invention may be applied to a method of improving the net
energy content of a fuel exposed to rain or flooding. The fuel is
preferably a low-rank, sub-bituminous or lignite coal.
[0034] These emulsions 10 are diluted with water and applied as a
spray 12 to a coal stream 14, usually at a transfer point where
both sides of the coal stream can be treated for thorough coverage.
Typically the emulsion is diluted 1 part emulsion to 19 parts water
to 1 part emulsion to 79 parts moisture and a diluted mixture is
then applied at a rate of twenty to eighty pounds (2.5 to 10
gallons) per ton of coal. The application is generally accomplished
using a pump and spray manifolds on either side of the coal stream.
The application of the waterproofing agents disclosed herein can
also be applied as a foam.
[0035] The coal is then allowed to dry, usually on a coal pile,
barge, or in a railcar, developing water repellency as it does so.
Generally, depending on ambient temperature, solar insolation, and
relative humidity, this can take as little as an hour or as long as
several hours.
[0036] The effect of waterproofing is long-lasting. In experiments
designed to determine the longevity of the treatment,
water-shedding was undiminished after twenty-eight days.
Example 1
Heat of Wetting
[0037] To examine the heat of water adsorption and determine
whether a surface treatment could affect this, freshly-produced
coal particles were sieved, and a fraction between 18 and 60 mesh
was isolated. The coal was treated with a variety of agents and
then dried at 40.degree. C. overnight, or, in some cases, for
several days. A one liter vacuum dewar flask calorimeter containing
a magnetic stir bar, thermocouple, and 100 grams of deionized water
was assembled and allowed to come to equilibrium. The thermocouple
was attached to a data recorder sampling at one data point per
second. Twenty grams of the treated coal was then added to the
calorimeter with stirring and the thermocouple was used to
vigorously mix the coal into the water insuring complete wetting
over a period of five to ten seconds. The temperature of the water
and coal mixture was monitored and after between five and twenty
minutes the temperature was extrapolated back to the point at which
the coal was added. The heat of adsorption was then calculated and
Table 1 was generated.
TABLE-US-00001 TABLE 1 Heat of Adsorption for Treated Coal Average
Heat of Treatment (scaled for adsorption, sub-2'' coal) J/g Test 1
Test 2 Test 3 Tap water 44.6 J/g 52.50878 43.99085 44.87238 Mineral
oil emulsion 46.0 J/g 56.59566 40.03123 41.28364 @ 196 g
emulsion/MT Silicone emulsion @ 45.4 J/g 51.10731 43.45505 41.69884
72.2 g emulsion/MT Latex emulsion @ 46.9 J/g 51.04161 44.54425
45.12869 87.0 g emulsion/MT Mineral oil emulsion 45.5 J/g 46.74927
44.75394 44.89994 @ 392 g emulsion/MT Silicone emulsion @ 43.6 J/g
45.57953 42.3645 42.89594 144.4 g emulsion/MT Latex emulsion@ 41.6
J/g 41.8583 42.69309 40.19634 174 g emulsion/MT
[0038] The treatment rate listed was scaled to account for the
particle size difference between 18-60 mesh and sub-5.08 cm fresh
coal. In other words, because of the difference in surface area the
18-60 mesh, coal was treated at a higher rate to achieve the same
treatment per surface area as would be the case for treating
sub-5.08 cm coal.
[0039] As can be seen, the treatment of coal in this experiment had
no effect (P<0.05) on the heat of adsorption when it was forced
to wet.
Example 2
Perk Tests
[0040] Approximately 30 kg of <5.08 cm coal was treated with the
indicated treatment (see Table 2), divided into three approximately
equal portions and allowed to dry for four days. All treatments
added a total of approximately 4% by weight of water solution to
the coal. The portions were divided in four and each portion in
four parts was loaded into a separate tared 15.25 cm diameter
translucent schedule 40 PVC tube that was closed at one end with a
cotton cloth. The combined sample plus tube was re-weighed and the
weight recorded. The coal filled the tube to a depth of 61 to 66
cm. Approximately 8.8 kg of water were poured into the top of the
tube and the time it took to run out was recorded. The tube was
then re-weighed and the coal was poured out of the tube and
examined. In spite of the large amount of water that was poured
through the coal sample, the majority of the mineral oil emulsion
treated coal was still dry. The experiment was repeated five days
later, that is, after the coal had been treated and allowed to
stand for four days and then tested and allowed to stand for
another five days the same samples were re-tested. The tests were
repeated a week later on the sixteen day old coal. The treatment
and observations are summarized in Table 2.
TABLE-US-00002 TABLE 2 Perk Tests on <5.08 cm Coal Water on
Percent Water on Percent Water on Percent the coal, Drain time, dry
coal, the coal, Drain time, dry coal, the coal, Drain time, dry
coal, 4 day 4 day 4 day 9 day 9 day 9 day 16 day 16 day 16 day
Treatment old coal old coal old coal old coal old coal old coal old
coal old coal old coal Water 1.7 kg 77.56 min 1% 2.6 kg columns 0%
1.7 kg columns 0% plugged plugged Oil 0.7 kg 15.00 min 90% 0.9 kg
7.37 min 96% 1 kg 5.833 min 93% emulsion @ 351 g/MT SBR Latex 2.1
kg 71.47 min 2% N/A N/A N/A N/A N/A N/A emulsion @ 252 g/MT
[0041] As can be seen, small amounts of mineral oil emulsion have a
profound impact on the wetting of treated coal, rendering the coal
effectively waterproof even after protracted periods and even after
exposure to significant quantities of liquid water. Surprisingly,
the SBR Latex treated coal was not rendered waterproof.
[0042] It was also noted after 9 and 16 days that the treated aged
coal in the test of this example had a much lower water content. In
each case the water content was measured on an Ohaus moisture
balance before each sample was loaded into the column. Thus the
water reported herein was water that was original to the coal plus
water that it had picked up during the previous perk tests on days
4 and 9 respectively. Table 3 illustrates these observations:
TABLE-US-00003 TABLE 3 Moisture Content of Coal Day 16 coal
moisture Day 9 coal moisture content content (prior Treatment
(prior to perk test) to perk test) Water 30.68% 42.81% Oil emulsion
@ 351 g/MT 24.51% 21.79%
[0043] We attribute this to the mineral oil inhibiting re-uptake of
liquid water, a logical consequence of waterproofing and then
adding roughly 8.8 kg (89% by weight) water to the coal during the
perk test. Lower water content is desirable in coal as that results
in a higher energy content per unit mass.
Example 3
Large-Scale Test
[0044] Approximately 75,000 short tons of freshly mined Powder
River Basin (PRB) coal were treated at an average rate of 0.8 lbs
of coal tar per ton (330 grams per metric ton) using a coal tar
emulsion. During the application, and subsequent to it, the coal
was subjected to 43-63 cm of rain as it was treated then
transported via open barge to an ocean freighter. On loading the
average coal temperature was 33.degree. C. During transport across
the Atlantic Ocean, the ship's captain pumped off 700 short tons of
water from the hold, indicating that the treated coal was shedding
surface water. This was an unusual occurrence--generally coal will
not shed water during transport. Upon unloading the average coal
temperature was 31.degree. C. It was clear that in addition to
shedding water the coal had not experienced self-heating. The coal
was stacked out at the receiving dock and the temperature was
monitored for five days:
TABLE-US-00004 TABLE 4 Temperature of Stacked-Out Treated Coal
Treated coal Comparison ambient temperature temperature Day 1
27.9.degree. C. 6.7.degree. C. Day 2 22.0.degree. C. 6.4.degree. C.
Day 3 17.7.degree. C. 13.1.degree. C. Day 4 18.0.degree. C.
16.9.degree. C. Day 5 18.0.degree. C. 16.7.degree. C.
[0045] In contrast to this, another approximately equal amount of
coal with the same transportation history but not treated with the
coal tar emulsion experienced significant self-heating after being
stacked out.
TABLE-US-00005 TABLE 5 Untreated Coal after Stack-Out Untreated
Untreated Coal Comparison ambient temperature temperature Day 1
20.5.degree. C. 10.3.degree. C. Day 2 22.2.degree. C. 12.5.degree.
C. Day 3 25.6.degree. C. 13.6.degree. C. Day 4 29.9.degree. C.
16.9.degree. C.
[0046] From the above data it is clear that the addition of a
waterproofing agent to freshly mined low-rank coal will interfere
with one of the basic mechanisms of low temperature self-heating
for that coal. A comparison of the data in Table 4 to the data in
Table 5 shows that a temperature change trend in a bulk pile of the
coal can be reversed using the treatment of the present invention.
A temperature of the bulk pile of treated coal in Table 4 trends
towards an ambient temperature rather than trending to a
temperature higher than the ambient temperature as experienced by
the untreated bulk pile of coal data presented in Table 5.
[0047] While the specific embodiments have been illustrated and
described, numerous modifications come to mind without
significantly departing from the spirit of the invention, and the
scope of protection is only limited by the scope of the
accompanying Claims.
* * * * *