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.

Description

TECHNICAL FIELD

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

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.

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).

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).

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).

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.

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.

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).

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

To understand the present invention, it will now be described by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a flowchart of an aspect of the present invention;

FIG. 2 is a flowchart of an aspect of the present invention;

FIG. 3 is a flowchart of an aspect of the present invention; and

FIG. 4 is a flowchart of an aspect of the present invention.

DETAILED DESCRIPTION

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.

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.

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.

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.

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.

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.

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.

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

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° 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 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

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.

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

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 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

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.

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 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%

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

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° 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° 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 4
Temperature of Stacked-Out Treated Coal
	Treated coal	Comparison ambient
	temperature	temperature
	Day 1	27.9° C.	6.7° C.
	Day 2	22.0° C.	6.4° C.
	Day 3	17.7° C.	13.1° C.
	Day 4	18.0° C.	16.9° C.
	Day 5	18.0° C.	16.7° C.

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 5
Untreated Coal after Stack-Out
		Untreated
	Untreated Coal	Comparison ambient
	temperature	temperature
	Day 1	20.5° C.	10.3° C.
	Day 2	22.2° C.	12.5° C.
	Day 3	25.6° C.	13.6° C.
	Day 4	29.9° C.	16.9° C.

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.

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.

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)