Pressure gradient passivation of carbonaceous material normally susceptible to spontaneous combustion

This invention is a process for the passivation or deactivation with resp to oxygen of a carbonaceous material by the exposure of the carbonaceous material to an oxygenated gas in which the oxygenated gas pressure is increased from a first pressure to a second pressure and then the pressure is changed to a third pressure. Preferably a cyclic process which comprises exposing the carbonaceous material to the gas at low pressure and increasing the pressure to a second higher pressure and then returning the pressure to a lower pressure is used. The cycle is repeated at least twice wherein the higher pressure may be increased after a selected number of cycles.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to coal processing and handling. More 
particularly, this invention relates to deactivation or passivation of 
coal or solid carbonaceous fuels to reduce the tendency of the material to 
spontaneously combust. 
2. Description of Related Art 
Solid carbonaceous materials, in particular solid carbon-based fuels, may 
autoignite or spontaneously combust under the proper conditions. 
Carbonaceous material may include coal, low-rank coal, dried coal, peat, 
char, or other porous solid fuel. For example, certain coals, such as 
sub-bituminous, lignite and brown coal, subsequent to mining can 
spontaneously combust due to chemical reactions between the coal, moisture 
and oxygen present in the air. This reaction can occur due to water 
combining with other components in the coal to generate a sufficient 
amount of heat to raise the temperature of the coal to the ignition point. 
Further, materials present in the coal may oxidize upon exposure to air, 
which in turn generates a sufficient amount of heat for the coal to reach 
ignition temperature. The components being oxidized within the coal may be 
non-carbonaceous matter or unsaturated carbon compounds within the coal. 
Certain coals, which are normally stable with respect to autoignition 
after mining, may be brought into proper conditions for autoignition after 
subsequent processing. For example, many low-rank coals contain 
significant amounts of free moisture. After drying to remove excess 
moisture these coals present a significant autoignition hazard. 
Low-rank coals, such as sub-bituminous coal or lignite may contain more 
than about 10% moisture and typically 15-50 weight percent moisture. Some 
low-rank coals may contain as much as 60 weight percent moisture. Such wet 
low-rank coals cannot be shipped economically over great distances due to 
the cost of transporting a significant fraction of unusable material in 
the form of water. Further, these low-rank coals cannot be burned 
efficiently due to the energy required to vaporize the water. Due to the 
lowered heating value and high cost of shipping unusable material, it is 
advantageous to remove all or part of the water from the low-rank coals 
prior to shipment and/or storage. However, drying such fuels usually leads 
to activation of the low-rank coals or chars. The reactive coals or chars 
may be hazardous due to the potential for damage to property or life due 
to the reaction of the coal or char with atmospheric oxygen and moisture 
and consequential heating of the coal, which makes it subject to 
spontaneous ignition during either shipment or storage. 
Indicators of the propensity of coals or chars to spontaneously combust 
include the uptake of oxygen as measured in terms of torr of oxygen per 
gram of material. Methods for testing this indicator are listed in U.S. 
Bureau of Mines "Report of Investigation 9330" by Miron, Smith, and 
Lazzara. The terms "oxygen uptake" and "oxygen demand" refer to the test 
methods of the "Report of Investigation 9330" or related test methods when 
used in this document. 
In the past, wet low-rank coals such as those from the western United 
States have been dried by methods such as, but not limited to, thermal 
drying using process heat, waste heat, microwaves, pressurized water, 
steam, hot oil, molten metals, and other supplies of high temperatures. 
The heated coals release the free moisture trapped in the pores, water 
molecules associated with hydrated molecules or associated in other ways 
with the coal, producing dried coals or chars. Other methods of drying may 
include mechanical drying (such as centrifugal separation), the use of dry 
gases, or the use of desiccants or absorbents. Once dried, coals or chars 
can become more active and are known to spontaneously combust. 
One approach to reduce the potential for the spontaneous combustion of the 
carbonaceous material, such as dried low-rank active coal or char (those 
susceptible to spontaneous combustion), is to seal the exterior surface of 
the char by using oils, polymers, waxes or other materials to coat the 
surface of the coal. Examples of such coating processes are U.S. Patent 
Numbers 3,985,516 and 3,985,517 to Johnson, which disclose heating and 
intimate mixing of coal with heavy oils to coat the particles. Such 
coating procedures are rather effective in preventing reabsorption of 
moisture by the char, however, such coatings are expensive due to the cost 
of the hydrocarbon materials added and thus are unattractive. It would be 
advantageous to dry wet coals and process them in such a manner that the 
dried coal or char particles are made less reactive after moisture 
removal, so as to prevent the reaction of the carbonaceous material with 
oxygen without the need for externally supplied coating materials. An 
alternate method to reduce spontaneous combustion is the prolonged 
exposure of the coal to air. Another method includes the use of oxidizing 
agents sprayed on coal. 
Another method to treat the carbonaceous material is the use of 
high-temperature water under pressure. The coatings perform their work by 
covering the pores and limiting the access of active components of the air 
to active sites in the material (dried coal in this instance). U.S. Pat. 
No. 1,632,829 to Fleissner discloses a process for drying wet coal by 
steam heating it using a procedure wherein steam provided above the coal 
is maintained at high partial pressure such that moisture will not escape 
during coal heat up, then reducing the steam pressure to permit the escape 
of moisture and rapid drying of the coal. Also, U.S. Patent Number 
4,052,169 to Koppelman discloses a process for upgrading lignitic coal, 
comprising heating it in an autoclave at about 750.degree. F. temperature 
and 1000 psig or more pressure to effect thermal restructuring, followed 
by cooling and depositing condensible organic material on the lignite to 
provide a stabilization of the upgraded product and render it 
non-hygroscopic and more resistant to weathering and oxidation during 
shipment and storage. The use of high temperature water is reported to 
drive off carboxylic acid groups and thereby remove those sites from 
future activity with the active components of the fluid. 
BRIEF SUMMARY OF THE INVENTION 
An object of this invention is to provide a process to reduce the ability 
of carbonaceous material such as low-rank coal, dried coal, char or peat 
to spontaneously combust thereby rendering such carbonaceous materials 
amenable to normal transport and handling procedures. 
Another object of this invention is to provide a means for stabilizing 
low-rank coals to improve the safety and economics for using such coals. 
These and other objectives of the invention, which will become apparent 
from the following description, have been achieved by a novel process for 
deactivation of a porous carbonaceous material by; providing an oxygenated 
gas; increasing the pressure on the carbonaceous material with the 
oxygenated gas from a first pressure to a second pressure; and reducing 
the pressure to a third pressure, wherein the third pressure is less than 
the second pressure. 
The increase in pressure of the oxygenated gas on the carbonaceous material 
can be achieved through a number of process routes, such as, the 
continuous steady increases of pressure to a peak pressure, increasing 
pressure in steps wherein the pressure is maintained and then momentarily 
reduced prior to further increases, or step-wise increases in pressure 
wherein the pressure is held constant for a period of time before 
increasing to the next constant pressure step. 
Preferably, the process for the deactivation of a porous carbonaceous 
material is achieved by; first, providing an oxygenated fluid; then 
exposing the carbonaceous material to the oxygenated fluid at a second 
pressure for a period of time sufficient to oxygenate the porous 
carbonaceous material; reducing the pressure of the oxygenated gas to a 
third pressure wherein the third pressure is less than the second 
pressure. 
The process may include additional steps of: exposing the carbonaceous 
material to the oxygenated gas at a fourth pressure for a period of time 
sufficient to further oxygenate the porous carbonaceous material and then 
reducing the pressure of the oxygenated gas to a fifth pressure wherein 
the fifth pressure is less than the fourth pressure. 
Alternatively, the process for deactivation of a porous carbonaceous 
material may comprise exposing the porous carbonaceous material to an 
oxygenated gas at a first pressure; providing an oxygenated gas; 
increasing the pressure of the oxygenated gas on the porous carbonaceous 
material to a second pressure; maintaining the pressure on the porous 
carbonaceous material for a period of time at the second pressure; 
increasing the pressure of the oxygenated gas to a third pressure wherein 
the third pressure is greater than the second pressure; and reducing the 
pressure of the oxygenated gas to a final pressure. The process may 
further comprise increasing the pressure of the oxygenated gas from the 
third pressure to a fourth pressure; maintaining the pressure on the 
porous carbonaceous material at the fourth pressure for a period of time 
prior to reducing the pressure of the oxygenated gas. The process may also 
comprise increasing the pressure of the oxygenated gas from the first 
pressure to a maximum pressure in a greater number of steps than described 
here. 
The process may take place at a temperature from about -25.degree. C. to 
about 750.degree. C. Preferably, the process takes place at a temperature 
from about 15.degree. C. to about 100.degree. C. The first pressure may be 
less than atmospheric pressure to about atmospheric pressure. The second 
pressure may range from about atmospheric pressure to about 1500 psig. 
Preferably, the second pressure is 500 psig. The third pressure may range 
from about atmospheric pressure to less than about 1000 psig. Preferably, 
the third pressure is atmospheric pressure. The fourth pressure may vary 
from about atmospheric pressure to about 1500 psig. Preferably the fourth 
pressure is from about atmospheric pressure to about 1000 psig. The fifth 
pressure may vary from about atmospheric pressure to less than about 1500 
psig. The second, third, fourth, and fifth pressure may vary from about 
atmospheric to less than about 2000 psig. Where additional pressure cycles 
or steps are needed these pressures may be up to a maximum of about 2000 
psig. 
Carbonaceous material may include, but is not limited to coal, low-rank 
coal, dried coal, peat, char, or other porous solid fuel. Preferably, the 
carbonaceous material is sub-bituminous coal or lignitic coal or char. The 
carbonaceous material may contain from about 0.1 weight percent to about 
20 weight percent of moisture. Preferably, the carbonaceous material may 
contain from about 1 weight percent to about 20 weight percent of 
moisture. 
The oxygenated gas contains from about 1 volume percent to about 35 volume 
percent oxygen. Preferably, the oxygenated gas contains from 10 to 25 
volume percent oxygen. Preferably, the oxygenated gas is air.

The invention is not limited in its application to the details and 
construction and arrangement of parts illustrated in the accompanying 
drawings since the invention is capable of other embodiments that are 
being practiced or carried out in various ways. Also, the phraseology and 
terminology employed herein are for the purpose of description and not of 
limitation. 
DETAILED DESCRIPTION OF THE INVENTION 
Description of the Preferred Embodiment(s) 
As shown in FIG. 1, a hypothetical example of the process of the invention 
is shown generally in graphical form at 10. Generally the process of this 
invention is the deactivation of a porous carbonaceous material with 
respect to spontaneous combustion by exposing the carbonaceous material to 
an oxygenated gas at increasing pressures. The carbonaceous material 
passivated/deactivated is permitted to stabilize at a first pressure 12 
for a period of time 14. The pressure on the carbonaceous material is 
increased 16 with an oxygenated gas to a second pressure 18. The actual 
rate of increase to the second pressure 18 is dependent on the actual 
process used and the material being treated. Reaction between oxygen and 
the carbonaceous material, takes place while the pressure is ramped up. 
The pressure is maintained at the second pressure for a period of time 20 
sufficient to permit further reaction between the carbonaceous material 
and the oxygenated gas. The time for which the material is maintained at 
the second pressure should also be sufficient for the oxygenated gas to 
react within the interstices of the material. The pressure on the material 
is then reduced to a third pressure 22 that is less than the second 
pressure 18. 
Preferably, the present invention is used to passivate dried low-rank coal 
(hereinafter DLRC) or char, however, other carbonaceous materials as 
discussed hereinabove can be used with the process of this invention. DLRC 
can be produced from any number of processes such as; U.S. Pat. No. 
5,601,692--Tek-Kol process, Char forming and atmospheric pressure air for 
passivation; U.S. Pat. No. 5,547,549--Vibrating bed pyrolysis system; U.S. 
Pat. No. 5,503,646--drying coal and mixing it with heavy oil to improve 
both; U.S. Pat. No. 5,322,530--WRI process: Fluidized bed, char forming 
and pitch-like coating for passivation (from the process EnCoal); U.S. 
Pat. No. 4,800,015--drying coal in hot oil to form a stable dried coal 
with an oil coating; U.S. Pat. No. 4,769,042--fluidized bed drying and 
then cooling with water then treating with steam at ambient pressure; U.S. 
Pat. No. 4,750,913--drying and mixing with wet coal; and U.S. Pat. No. 
4,645,513--drying and then oxidation with air at ambient pressure. 
The DLRC is placed in an appropriate pressure vessel, such as an autoclave. 
The DLRC may be agitated by appropriate means such as stirring blades or 
paddles, however, such agitation means are not required to accomplish the 
objectives of this process. The preferred process steps are illustrated in 
FIG. 2 and 2a. The DLRC is permitted to stabilize for some period of time 
24 at a first pressure 26. The stabilization period for the experimental 
tests was on the order of two to ten minutes. Industrial scale process may 
require a longer stabilization period. The first pressure may be a 
moderate vacuum or a pressure about atmospheric pressure. Low pressure on 
the order of one to two atmospheres may be used when process parameters so 
indicate. Also, the initial stabilization period may be done with an 
oxygen-free or low oxygen gas. Alternatively an inert gas such as nitrogen 
or argon may be used. The DLRC is then exposed to an oxygenated gas and 
the pressure is raised to a second pressure 28. The DLRC is maintained at 
the second pressure 28 for a period of time 30 sufficient for the 
carbonaceous material to stabilize. The pressure on the system and the 
DLRC is then reduced to a third pressure 32 that is less than the second 
pressure. This cycle may be repeated as many times as needed to passivate 
the DLRC. For example the DLRC may be pressurized in the passivation gas 
to a fourth pressure 34 and maintained at the fourth pressure until the 
DLRC has stabilized 36, wherein the fourth pressure may be greater than 
the second pressure. The system including the DLRC is then reduced to a 
fifth pressure 38 which is less than the fourth pressure 34. 
A third possible embodiment is to increase the pressure of the oxygenated 
gas stepwise without decreasing the pressure between cycles as shown in 
FIG. 3. In this embodiment of the invention the carbonaceous material is 
stabilized at a first pressure 40. The pressure of the oxygenated gas is 
increased to a second pressure 42 and maintained at that pressure for a 
period of time 44. The pressure is then increased from the second pressure 
42 to a third pressure 46 without first reducing the pressure. The 
pressure may be held at the third pressure 46 for a period of time 48 
before increasing the pressure to a fourth pressure 50. The pressure may 
then be reduced to a lower pressure after being maintained at the fourth 
pressure 50 for a period of time. 
The first pressure is about atmospheric pressure. The second pressure may 
range from about atmospheric pressure to about 500 psig. The third 
pressure may range from about atmospheric pressure to less than about 1000 
psig. The fourth pressure may vary from about atmospheric pressure to 
about 1500 psig. Alternatively, more steps may be used with smaller 
pressure increases at each step. Alternatively, fewer steps may be used 
with a greater pressure increase at each step. The second, third, fourth, 
and each additional pressure may vary from approximately atmospheric 
pressure to approximately 2000 psig. 
The oxygenated gas for use with the process of the invention may contain 
from about 1 volume percent oxygen to about 35 volume percent oxygen. 
Preferably, the oxygenated gas contains from about 10 volume percent to 
about 25 volume percent oxygen. An oxygenated gas containing a lower level 
of oxygen may be used for the first stage of pressurization, then a gas 
containing a higher level of oxygen may be used in subsequent cycles. For 
example, a gas containing from about one to about five volume percent 
oxygen may be used to pressurize the carbonaceous material up to the 
second pressure. Subsequent pressurization steps may be done with a gas 
that contains from about five to about 21 volume percent oxygen. The 
preferred oxygenated gas for use with this invention is air. 
EXPERIMENTAL RESULTS 
Samples of a sub-bituminous western US coal sized to minus 1/4 inch were 
prepared for the deactivation test by high-temperature dehydration similar 
to the methods used in commercial dehydration practices such as the 
SynCoal process. Each sample was approximately 245 grams. Each sample was 
then packaged under a nitrogen atmosphere in a sealed container for 
shipment and handling prior to testing. Once ready for testing, to provide 
a control comparison between test samples, each sample was split into 
representative test samples of approximately 50 grams by coning and 
quartering, while still under a relatively inert nitrogen atmosphere, 
which contained a small fraction of oxygen (approximately 30 ppm-60 ppm 
oxygen). After splitting, each sample was stored in a tight plastic 
container in a nitrogen filled glove box (oxygen content less than 60 ppm) 
until tested. Testing consisted of placing a split sample into an 
autoclave (while still in the glove box) and then moving the sealed 
autoclave to the test area for processing. Nitrogen atmosphere is not a 
part of the process, instead, it prevents reaction of the carbonaceous 
material with oxygen outside of the processing time for experimental 
control. 
As shown in FIG. 4, a standard commercial autoclave 52 similar to those 
available from commercial vendors was used. The volume of the autoclave 
used in these experiments was more than was needed for the volume of 
sample being tested. A rigid plastic sleeve was used in the autoclave as a 
spacer to reduce the effective volume of the autoclave so that excessive 
gas was not used during the experiment. The spacer is not integral to the 
process. Instead it served to reduce the cost of the experiments by 
reducing the amount of treatment gas used. 
The autoclave was then attached to standard cylinders 54 of treating gas 
such as commercially available compressed dry air or commercially 
available oxygen/nitrogen mixtures. For those tests in which the treating 
gas was saturated with water vapor the incoming gas stream was bubbled 
through water in another autoclave 56, as shown in FIG. 5. A porous baffle 
material contained within water trap 57 was used to prevent entrainment of 
water droplets in the gas stream ensuring that only water vapor was 
carried onto the sample in the gas stream. Other methods for ensuring that 
water vapor enters the process, may be used. 
A commercial vacuum pump 58 was attached to the outgoing gas stream to 
allow evacuation of the apparatus. In the case of vacuum treatment 
experiments there was a cold-trap 59 installed in the outgoing gas stream 
to remove any water vapor before the gas entered the vacuum pump. The cold 
trap was designed to protect the vacuum pump from the water vapor, and is 
not necessary to the process. 
To pressurize the apparatus, the exhaust valve 60 was closed and an inlet 
valve 62 connecting the high-pressure cylinders 54 of gas through a 
standard pressure regulating valve 63 was opened. The regulating valve 
allowed the gas to flow through until the designated regulating pressure 
was reached. The pressure was reached quickly (10 seconds to 20 seconds) 
in this particular apparatus and the sample was allowed to equilibrate at 
the high-pressure (500 psi, 1,000 psi, or 1,500 psi) for a total of seven 
minutes. The choice of seven minutes is not meant to indicate an optimal 
time. Instead, it is a time that was chosen for these particular tests for 
this particular carbonaceous material and it is expected that this time 
will vary depending on the material being passivated and the process 
conditions. As an example, as shown in FIG. 3, for stepped experiments the 
pressure was increased in increments first to 500 psi and held there for 
70 minutes, then to 1,000 psi and held there for 70 minutes, and finally 
to 1,500 psi and held there for 70 minutes before finally being exhausted. 
This is an example of a modified process that uses the same principles of 
pressure differential without cycling. In that case the times are 
considerably longer at each pressure. The pressures of 500 psi, 1,000 psi, 
and 1,500 psi are not optimized and were chosen for these experiments 
only. It is expected that other pressures will be applicable depending on 
the material being passivated and the process conditions. These pressures 
were used in these experiments. 
For evacuation of the apparatus, the incoming gas valve 62 to the autoclave 
52 was shut off to isolate the autoclave from the high-pressure gas. An 
exhaust valve 60 was opened to exhaust the autoclave 52 to atmospheric 
pressure. As the autoclave 52 approached atmospheric pressure the exhaust 
valve 60 was closed, a vacuum pump 58 was started, a (vacuum) pump valve 
64 was opened, and a pressure gauge was observed until the pressure in the 
autoclave 52 reached 5-7 torr absolute. The exhausting and evacuation of 
this particular experimental apparatus took approximately 15-30 seconds. 
The vacuum pump continued to operate for a total of 150 seconds after the 
start of the exhausting of the autoclave. At the end of 150 seconds the 
vacuum pump valve 64 was closed, the vacuum pump was turned off, and high 
pressure gas was introduced into the apparatus. The choice of 150 seconds 
is not considered to indicate an optimal time. Instead, it, is should be 
considered as a time that was chosen for this particular set of 
experiments for this particular carbonaceous material and it is expected 
that this time will vary depending on the material being treated and the 
process conditions. 
For exhaust of the apparatus without evacuation, the inlet gas valve 62 is 
shut and the exhaust valve 60 is then opened, allowing the high-pressure 
to bleed off into the atmosphere. This exhaust process takes from 10 
seconds to 30 seconds for this apparatus. 
For cycling experiments without vacuum, the autoclave 52 with the sample in 
it was started at atmospheric pressure and the treatment gas was allowed 
to flow through the autoclave to remove the nitrogen atmosphere that the 
autoclave initially has from the glove box. The autoclave was then 
pressurized in accordance with the procedure above. The length of these 
pressure cycles was set at 7 minutes for these experiments. At the end of 
the 7 minutes the autoclave was exhausted in accordance with the procedure 
above and for these experiments stabilized at atmospheric pressure for a 
total of 2 minutes. This procedure was repeated for the number of cycles 
designated for each sample at each of the designated high pressure levels. 
For cycling experiments with vacuum, the autoclave with the sample in it 
was started at atmospheric pressure and the treatment gas was allowed to 
flow through the autoclave to remove the nitrogen atmosphere that the 
autoclave initially has from the glove box. The autoclave was then 
pressurized in accordance with the procedure above. The length of these 
pressure cycles was set at 7 minutes for these experiments. At the end of 
the 7 minutes the autoclave was evacuated in accordance with the procedure 
above and for these experiments stabilized at low pressure for a total of 
150 seconds. This procedure was repeated for the number of cycles 
designated for each sample at each of the designated high pressure levels. 
At the end of the cycles the autoclave was again evacuated prior to moving 
the sample back to the glove box. 
The following tables present the test results for each of the different 
test runs. A synopsis of each experiment follows the Tables. Samples 
labeled "none" under the Graphing Category were not used in the 
statistical analysis of the different process embodiments. All other data 
(except where indicated) were used for statistical analysis and the 
preparation of FIG. 6. 
TABLE I 
______________________________________ 
Residual Oxygen 
Change 
Demand Average 
(% of 
Split (torr/g, 2500 minutes) 
pre-test Graphing 
Number Treatment Pre-test Post-test 
value) Category 
______________________________________ 
ME3681-5 
Glove box 28.2 27.0 4.26 A 
ME3691-5 
Glove box 33.1 26.0 21.45 
ME3689-5 
Glove box* 
33.1 19.5 41.24 
ME3683-5 
Glove box 31.2 31.1 0.16 
ME3703-4 
Glove box 28.9 24.7 14.53 
ME3707-5 
Glove box 27.8 21.7 21.94 
ME3737-5 
Glove box* 
25.7 13.5 47.67 
______________________________________ 
Glove box. These splits from TABLE I were stored in the glove box under 
nitrogen atmosphere for the total amount of time that other splits from 
the same sample were being stored, handled and tested. 
TABLE II 
______________________________________ 
Residual Oxygen 
Change 
Demand Average 
(% of 
Split (torr/g, 2500 minutes) 
pre-test Graphing 
Number Treatment Pre-test Post-test 
value) Category 
______________________________________ 
ME3681-3 
Atm 90 28.2 26.9 4.61 None 
ME3681-4 
Atm 180 28.2 27.6 2.13 None 
ME3690-1 
Atm 270* 32.4 22.5 30.56 B 
ME3691-1 
Atm 270 33.1 23.7 28.40 
ME3684-1 
Atm 270 30.5 27.9 8.63 
ME3683-1 
Atm 270 31.2 28.6 8.35 
ME3689-1 
Atm 270* 33.1 15.0 54.68 
ME3681-2 
Atm 270 28.2 27.4 3.01 
ME3681-1 
Atm 270 28.2 22.4 20.69 
ME3682-1 
Atm 270 28.2 24.0 14.89 
ME3692-1 
Atm 270 30.7 25.3 17.75 
______________________________________ 
Atm X. These splits were exposed to atmosphericpressure dry air flowing 
slowly over the split for a total of the specified number of minutes. 
TABLE III 
______________________________________ 
Residual Oxygen 
Change 
Demand Average 
(% of 
Split (torr/g, 2500 minutes) 
pre-test 
Graphing 
Number Treatment Pre-test Post-test 
value) 
Category 
______________________________________ 
ME3683-3 
Step 0/70/0 
31.2 22.3 28.41 None 
ME3683-4 
Step 7/7/70 
31.2 24.4 21.67 None 
ME3683-2 
Step 70/0/0 
31.2 25.0 19.74 None 
ME3682-5 
Step 70/70/70 
28.2 18.3 35.02 C 
ME3682-4 
Step 70/70/70 
28.2 19.4 31.38 
ME3736-1 
Step 70/70/70 
31.4 11.6 63.22 
______________________________________ 
Step X/Y/Z. These splits for TABLE III were exposed to pressurized dry ai 
at 500 psi for X minutes, then pressurized to 1000 psi for Y minutes, and 
finally, pressurized to 1500 psi for Z minutes before reducing the 
pressure to atmospheric. 
TABLE IV 
______________________________________ 
Residual Oxygen 
Change 
Demand Average 
(% of 
Split (torr/g, 2500 minutes) 
pre-test 
Graphing 
Number Treatment Pre-test Post-test 
value) 
Category 
______________________________________ 
ME3684-4 
Cyc 0/10/0 30.5 24.1 20.98 None 
ME3684-5 
Cyc 1/1/10 30.5 22.3 27.05 None 
ME3684-2 
Cyc 10/0/0 30.5 23.5 22.95 None 
ME3702-4 
Cyc 10/10/10 
26.0 13.1 49.62 D 
ME3682-3 
Cyc 10/10/10 
28.2 18.1 35.99 
ME3692-2 
Cyc 10/10/10 
30.7 16.4 46.74 
ME3691-2 
Cyc 10/10/10 
33.1 14.4 56.65 
ME3682-2 
Cyc 10/10/10 
28.2 18.8 33.33 
ME3684-3 
Cyc 10/10/10 
30.5 21.7 29.02 
______________________________________ 
Cyc X/Y/Z. These splits were cycled between atmospheric pressure and the 
higher pressure, first X times to 500 psi for 7 minutes, then Y times to 
1000 psi for 7 minutes, and finally Z times to 1500 psi for seven minutes 
using dry air. The time at atmospheric pressure was 2 minutes for each 
cycle (See FIG. 2). 
TABLE V 
______________________________________ 
Residual Oxygen 
Change 
Demand Average 
(% of 
Split (torr/g, 2500 minutes) 
pre-test Graphing 
Number Treatment Pre-test Post-test 
value) Category 
______________________________________ 
ME3689-2 
Vac cyc 33.1 15.1 54.38 None 
10/0/0 
ME3690-2 
Vac cyc 32.4 14.0 56.79 E 
10/10/10* 
ME3689-4 
Vac cyc 33.1 14.3 56.80 
10/10/10* 
ME3689-3 
Vac cyc 33.1 16.5 50.30 
10/10/10* 
ME3692-4 
Vac cyc 30.7 15.4 50.00 
10/10/10 
ME3691-4 
Vac cyc 33.1 15.2 54.23 
10/10/10 
ME3690-5 
Vac cyc 32.4 12.4 61.73 
10/10/10* 
ME3706-5 
Vac cyc 29.4 15.0 49.15 
10/10/10 
ME3736-5 
Vac cyc 31.4 13.4 57.48 
10/10/10 
______________________________________ 
Vac cyc X/Y/Z. These splits for TABLE V were cycled between a vacuum and 
the higher pressure, first X times to 500 psi for 7 minutes, then Y times 
to 1000 psi for 7 minutes, and finally Z times to 1500 psi for seven 
minutes using dry air. The time under vacuum totaled 2.5 minutes for each 
cycle. 
TABLE VI 
______________________________________ 
Residual Oxygen 
Change 
Demand Average 
(% of 
Split (torr/g, 2500 minutes) 
pre-test Graphing 
Number Treatment Pre-test Post-test 
value) Category 
______________________________________ 
ME3692-3 
Wet cyc 30.7 14.8 51.79 F 
10/10/10 
ME3691-3 
Wet cyc 33.1 14.7 55.59 
10/10/10 
ME3690-3 
Wet cyc 32.4 12.8 60.49 
10/10/10* 
ME3690-4 
Wet cyc 32.4 12.7 60.80 
10/10/10* 
ME3706-3 
Wet cyc 29.4 10.4 64.80 
10/10/10 
ME3737-3 
Wet cyc 25.7 7.0 72.96 
10/10/10* 
______________________________________ 
Wet cyc X/Y/Z. These splits for TABLE VI were cycled between atmospheric 
pressure and the higher pressure, first X times to 500 psi for 7 minutes, 
then Y times to 1000 psi for 7 minutes, and finally Z times to 1500 psi 
for seven minutes using humid air. The time at atmospheric pressure was 2 
minutes for each cycle. 
TABLE VII 
______________________________________ 
Residual Oxygen 
Change 
Demand Average 
(% of 
Split (torr/g, 2500 minutes) 
pre-test Graphing 
Number Treatment Pre-test Post-test 
value) Category 
______________________________________ 
ME3703-1 
Vac cyc 28.9 14.8 48.79 G 
1/1/40 
ME3707-1 
Vac cyc 27.8 9.8 64.93 
1/1/40 
ME3702-1 
Vac cyc 26.0 12.0 53.85 
1/1/40 
ME3706-1 
Vac cyc 29.4 11.0 62.76 
1/1/40 
ME3737-1 
Vac cyc 25.7 8.0 69.07 
1/1/40* 
______________________________________ 
Vac cyc X/Y/Z. These splits for TABLE VII were cycled between a vacuum an 
the higher pressure, first X times to 500 psi for 7 minutes, then Y times 
to 1000 psi for 7 minutes, and finally Z times to 1500 psi for seven 
minutes using dry air. The time under vacuum totaled 2.5 minutes for each 
cycle. 
TABLE VIII 
______________________________________ 
Residual Oxygen 
Change 
Demand Average 
(% of 
Split (torr/g, 2500 minutes) 
pre-test Graphing 
Number Treatment Pre-test Post-test 
value) Category 
______________________________________ 
ME3707-2 
Wet cyc-vac 
27.8 9.2 66.91 H 
10/10/10 
ME3703-2 
Wet cyc-vac 
28.9 14.4 50.17 
10/10/10 
ME3706-2 
Wet cyc-vac 
29.4 12.2 58.39 
10/10/10* 
ME3702-2 
Wet cyc-vac 
26.0 11.8 54.81 
10/10/10 
ME3736-3 
Wet cyc-vac 
31.4 13.5 57.01 
10/10/10 
______________________________________ 
Wet cycvac X/Y/Z. These splits for TABLE VIII were cycled between a vacuu 
and the higher pressure, first X times to 500 psi for 7 minutes, then Y 
times to 1000 psi for 7 minutes, and finally Z times to 1500 psi for seve 
minutes using humid air. The time at the low vacuum totaled 2.5 minutes 
for each cycle. 
TABLE IX 
______________________________________ 
Residual Oxygen 
Change 
Demand Average 
(% of 
Split (torr/g, 2500 minutes) 
pre-test Graphing 
Number Treatment Pre-test Post-test 
value) Category 
______________________________________ 
ME3702-3 
Fast wet 26.0 14.1 45.77 I 
cyc-vac 
90/0/0 
ME3703-3 
Fast wet 28.9 18.1 37.37 
cyc-vac 
90/0/0 
______________________________________ 
Fast wet cyc vac X/Y/Z. These splits were cycled similarly to the Vac cyc 
X/Y/Z samples (See Table V), except that humid air was used as the 
treating gas, and the times at high pressure and vacuum were reduced to 1 
minute each. 
TABLE X 
______________________________________ 
Residual Oxygen 
Change 
Demand Average 
(% of 
Split (torr/g, 2500 minutes) 
pre-test Graphing 
Number Treatment Pre-test Post-test 
value) Category 
______________________________________ 
ME3706-4 
Wet cyc-vac 
29.4 9.5 67.86 J 
1/1/40 
ME3736-4 
Wet cyc-vac 
31.4 10.3 67.36 
1/1/40 
ME3737-4 
Wet cyc-vac 
25.7 6.3 75.68 
1/1/40* 
______________________________________ 
Wet cycvac X/Y/Z. These splits for TABLE X were cycled between a vacuum 
and the higher pressure, first X times to 500 psi for 7 minutes, then Y 
times to 1000 psi for 7 minutes, and finally Z times to 1500 psi for seve 
minutes using humid air. The time under vacuum totaled 2.5 minutes for 
each cycle. 
TABLE XI 
______________________________________ 
Residual Oxygen 
Change 
Demand Average 
(% of 
Split (torr/g, 2500 minutes) 
pre-test Graphing 
Number Treatment Pre-test Post-test 
value) Category 
______________________________________ 
ME3692-5 
Moist atm 30.7 22.8 25.90 None 
270 
______________________________________ 
Moist atm X. These splits from TABLE XI were exposed to 
atmosphericpressure humid air flowing slowly over the split for X minutes 
TABLE XII 
______________________________________ 
Residual Oxygen 
Change 
Demand Average 
(% of 
Split (torr/g, 2500 minutes) 
pre-test 
Graphing 
Number Treatment Pre-test Post-test 
value) 
Category 
______________________________________ 
ME3736-2 
Cyc-vac (30%) 
31.4 11.4 63.85 None 
1/1/10 + 30 
ME3737-2 
Cyc-vac (30%) 
25.7 6.9 73.15 None 
1/1/10 + 30* 
______________________________________ 
Cyc-vac (30%) X/Y/Z + AA. These splits for TABLE XII were cycled between 
vacuum and the higher pressure, first X times to 500 psi for 7 minutes, 
then Y times to 1000 psi for 7 minutes, then Z times to 1500 psi for seve 
minutes using dry air, and finally, AA times to 1500 psi using a dry gas 
composed of 30% oxygen and 70% nitrogen. Tbe time under vacuum totaled 2. 
minutes for each cycle. 
*Rows with this designation are tests and data that are deemed unreliable 
due to contamination by air during transport or storage. 
FIG. 6 illustrates the Residual Oxygen Demand for each of the graphing 
categories. In all pressure treatment presented the oxygen demand of the 
coal was significantly reduced in the process. 
It should be clear to those skilled in the art that there are many possible 
variations and combinations of these examples and that this process can be 
used on many materials for treatment of many different properties. One 
important aspect of this invention is the use of the pressure to force the 
oxygenated fluid into intimate contact with an active material, increasing 
the partial pressure of oxygen and through accelerated reaction changing 
the activity of the material. 
Thus, in accordance with the invention, there has been provided a process 
to reduce the ability of carbonaceous material such as low-rank coal, 
dried coal, char or peat to spontaneously combust thereby rendering such 
carbonaceous materials amenable to normal transport and handling 
procedures. There has also been provided a means for stabilizing low-rank 
coals to improve the safety and economics for using such coals. 
With this description of the invention in detail, those skilled in the art 
will appreciate that modification may be made to the invention without 
departing from the spirit thereof. Therefore, it is not intended that the 
scope of the invention be limited to the specific embodiments that have 
been illustrated and described. Rather, it is intended that the scope to 
the invention be determined by the scope of the appended claims.