Note: Descriptions are shown in the official language in which they were submitted.
114V880
Background of the Invention
There exists in the United States a large quantity of
coal which cannot be economically used as a fuel because of its
high sulfur content. Environmental laws are such that it is
economically unfeasible to burn a high sulfur content coal
because of the expensive antipollution equipment required.
High sulfur coal, i.e., about 3%, exists in unmined
form and also in the form of already mined coal that has been
discarded, i.e., refuse coal. Refuse coal usually consists of
fines which result from the processing of coal. More particu-
larly, when coal is mined it is normally crushed and washed and
the washings are generally dumped and used as land fill or
dumped into a lake or stream. In the latter case, over a period
of time, the pond or stream becomes almost completely filled with
the finely powdered coal. Not only is this a significant waste
of coal but it is injurious to the lakes and streams. Many lakes
have become "dead" lakes due to this disposal of waste coal. The
ash content of such refuse coal, i.e., above 20% by weight, also
makes it economically unattractive to attempt to utilize it.
There also exist in the United States substantial
deposits of unmined or virgin coal having a high sulfur content.
In order to burn such coal in industry it would be necessary to
spend substantial amounts of money for air pollution equipment.
Therefore, this high sulfur content coal is not being mined.
The need to effectively utilize energy while at the
same time protecting our environment faces many other industries
as well, the steel industry being another example. The disposal
of waste materials from steel making processes in an economically
feasible, environmentally suitable manner is frequently a
significant problem. For example, in the processing of steel an
~ 11~880
acid solution (pickle liquor) is used to treat the product. The
resultant solution consisting of acid, iron compounds, contami-
nants, etc. (collectively referred to hereinafter as spent pickle
liquor) must be disposed of.
Summary of the Invention
The present invention is applicable to high sulfur,
high ash refuse or virgin coal. In one form of the present
process, coal, crushed to about 1/4 by 0 size is first treated
with spent pic~le liquor. Thereafter it is subjected to a strong
acidic oxidizing agent. More particularly, the acidified coal
mixture is treated with a mixture of chlorine gas dissolved in
water. Thereafter coal and ash are separated through the use of
water and gravity. Following this, the acid solution remaining
is treated with lime and the precipitate which contains ~arious
sulfur compounds is discarded. These sulfur compounds exist in
such a state that they are not injurious to our environment when
discarded and in fact have a beneficial effect on dead lakes.
In an alternative form of the present invention only a minor
amount of water is added to the pulverized coal, preferably in
the form of steam, and the mixture is treated with chlorine gas.
Description of the Preferred Embodiment
The process of this invention can be effectively
practiced on any high sulfur content coal. In its most useful
application it is practiced on refuse coal that at the present
time has no utility. After treatment the refuse coal contains
less than about 1% sulfur, has about 5-6~ ash, has about 14,000-
14,500 btu per pound, and is processed into easily handled
pellets. In contrast, before processing the refuse coal
typically contains 2-3% sulfur, 25-30% ash and has a btu content
of only 7,500.
~ 11~880
Refuse coal is produced as the result of normal coal
mining operatlons and exists as a result of coal being crushed
and washed. Typically it is 1/4 by 0, that is 1/4 inch down to
325 mesh in size. Typically it is discarded as land fill or
thrown into a pond, lake or stream. In some instances as much
as 20~ by weight of the mined coal ends up in the form of hereto-
fore unusable refuse coal.
Various areas of the United States contain large
deposits of coal which are basically unusable because of the high
sulfur content of the coal. The present process is applicable
also to such coal. The only modification required is to
pulverize the coal so that it is about 1/4 by 0 as in the case of
refuse coal.
In the practice of the process the pulverized coal is
first mixed with spent pickle liquor. In the manufacture of iron
or steel it is customary to use a pickling acid to remove scale,
rust, etc. Most frequently 60 Be' sulfuric acid is employed and
this is the preferred form for use in the present invention
although other acid pickle liquors may be employed. After use,
the spent pickle liquor comprising the acid and various iron
compounds such as Fe2(SO4)3, FeSO4 7H2O and other contaminants
must be disposed of. Obviously, the disposal of such a li~uid
poses a significant problem from an environmental standpoint.
For some unknown reason the use of spent pickle liquor
produces superior results than if the acid itself is used. While
it is not completely understood, it is believed that the iron
salts present in the spent pickle liquor have a significant
effect on the reaction rate.
If only uncontaminated H2SO4 is used, the final results
in many cases in terms of sulfur removal are inferior and the
:J~14~880
speed of the reaction is decreased. Moreover, the ability to
convert a material that poses such a~ environmental risk to a
safe, useful material able to benefit the environment is an
advantage not to be taken lightly. While it is preferred to use
spent pickle liquor the acid in unused form may be utilized
recognizing, of course, that under some conditions inferior
results may be obtained.
The amount of spent pickle liquor mixed with the
pulverized coal is somewhat dependent on the sulfur content of
the coal. Usually though 2% pickle liquor based on the weight
of the coal is sufficient.
It is important to allow the pickle liquor to contact
the coal for a brief period of time prior to further processing.
In practice 5-10 minutes has been found to be satisfactory.
Thereafter, the mixture is introduced into any suitable type of
reactor mixer and mixed with about 20~ by weight of water.
Preferably the water temperature and temperature of the mixture
is 80-90 F. This may require suitable heating or cooling means
of conventional design. Into the reactor mixer is introduced
chlorine gas. The amount of chlorine required is an amount
sufficient to provide a mixture having a pH of about 3 or less.
When mixed with the water the chlorine gas provides hydrochloric
acid, hypochlorous acid and nascent oxygen.
While it is not completely understood, it is believed
that the iron disulphide (iron pyrite) which is present in the
coal and which forms the major sulfur containing material is con-
verted into the following iron and sulfur compounds through the
followin~ reactions:
FeS2 + 2HOCl ~ FeS + 2HCl + SO2
FeS + 2HCl + FeC12 + H2S
114(~880
H2S + 2HOCl ~ S2 + 2HCl
S2 + H2 ~ H2 S03
H~SO3 + HOCl ~ H2SO4 + HCl
After the reaction is essentially complete, the ash and coal that
are present can be mechanically separated from each other and
from the acid solution. One convenient way for doing so consists
of introducing the entire mixture into a conically shaped
separator of conventional design, where provision is made at the
bottom for introducing water. At the top a wier is provided such
}0 that material at the surface of the mixture will be transferred
out of the separator and into a discharge conduit. The denser,
heavier coal particles fall to the bottom and are discharged
through an outlet. The coal is then dried and preferably
pelletized.
~_ To the liquid and water material overflowing the
separation is added a sufficient amount of lime to precipitate
most of the sulfur as calcium salts, i.e., CaSO3, CaS, CaSO4 or
other salts of calcium containing sulfur. The amount of lime
re~uired is that amount which is required to provide a neutral
or nearly neutral pH. Such precipitated salts are thereafter
separated and preferably used as fill in coal slurry ponds. If
the ponds are not totally filled but if a sufficient amount of
the precipitate is added over a relatively short period of time
the pond is once again capable of supporting life.
The coal so recovered has less than 6~ ash, less than
1% sulfur and a btu content of about 14,000 per pound. The
economics of the process are such that refuse coal may be
economically reclaimed to provide an excellent energy source.
In the alternative form of the present invention, to
the pulverized coal is added a minor amount of water, preferably
~ ` I ~14~880
in the form of steam. The water added is preferably an amount
equal to about 10-20~ by weight of the coal. Thereafter, to
the mixture is added chlorine gas. Unlike the previous embodiment
the chlorine gas is not dissolved in water nor is pickle liquor
added to the mixture. Also, the amount of water required is
reduced. As in the previous embodiment, the mixture after treat-
ment with the chlorine gas is subjected to the separation step
and thereafter to the neutralization step.
Having thus described my invention, I claim:
. . ; . ~ . ,
