Note: Descriptions are shown in the official language in which they were submitted.
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1 The invention relates generally to the coking of coal.
The coking of dry coal, that is, coal which has been
preheated to temperatures of 150 to 250C, for example, provides
the advantage that savings in the heating costs associated with
the production of coke may be realized. Thus, whereas the heat-
ing required for the coking operation is costly, it is possible
to preheat the coal using relatively inexpensive heating means.
Furthermore, the prehating of the coal permits coke of higher
quality to be produced therefr~m and, in particula~,~, permits
coke of larger particle size and greater abrasion resistance to
be obtained than would be possible otherwise. As a result of
this, it is possible to produce a relatively good quality of
coke from coal having relatively poor coking characteristics
by preheating the coal.
It is already known to pneumatically convey preheated
coal from a supply container into the individual chambers of a
coke oven battery via a branched conduit system. with this fll-
ling technique, ignitions and explosions occur in the oven cham
bers. The explanation for this resides in that the coal must be
admitted into the oven chambers with a considerable amount of
force, and accordingly, the blowing of the coal causes the hot
coking coal to be admitted into the individual chambers in the
form of streams so that part of the coal comes into contact with
the hot atmospheres in the chambers, as well as with the hot cham-
ber walls, in the form of a fine dust cloud. The above filling
technique requires a strong blowing of the coking coal into the
chambers in order to achieve a uniform filling of the coal over
the entire lengths of the respective chambers. It is apparent that
the filling technique just described has associated with it the dis-
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1 advan-tage tha~ there exists a particularly s~rong propensity for
the development of dust and, concomitantly, an increased danger
of explosion.
It has been proposed, in order to suppress the danger
of ignition and explosion, to add between 0.5 and 5 percent by
weight of residual oil, or residual oil in admixture with pitch,
to the preheated coal. This proposal was intended to make it
possible to pneumatically admit the hot coal into the coke oven
chambers without danger. E~idently, this proposal contemplates
for the fine dust particles to be ag~lomerated by means of the
residual oil so that these dust particles become harmless as a
cause of dust explosions. The reason for the selection of re-
- sidual oil, in admixture with pitch if desired, from among the
many known oils which are effective for bindiny dust is based on
the fear that the addition of oils of lower boiling point to the
coal might create an additional fire and explosion hazard rather
than suppressing such hazard. With residual oil, in a~mixture
with pitch if desired, such danger should be small since residu-
al oil contains only small amounts of readily volatilizable con-
stituents.
The addition to the coal of residual oil, in admi~ture
with the pitch if desired, does not, however, prevent substan-
tial amounts of coal dust from being carried out of the oven
chambers into the collecting means exteriorly thereof. Thus,
as a rule, an additional formation of dust takes place in the
upper regions of the oven chambers towards the end of the filling
operation. The ~eason for this resides in that the ~ases which ~ -~
de~elop as a result of degasification rise through the coal charge
in the chambers and, for a certain peridd of time, cause the coal
to be in a fluidized state in the upper regions of the chambers.
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1 With the above-described method, the quantity of coal dust car-
ried out of the chambers is between approximately 30 and 50
kilograms per ton of coal.
The coal dust which escapes from the oven chambers
and enters the collecting means is referred to as "carry over"
in the art. This coal dust ~orms a highly viscous mass i~ the
collecting means which is di~icult to remove. Moreover, a por-
tion of the dust is carried into the tar separator by the conden-
sate flowing out of the collecting means. In the ~ar separator,
the dust leads to the formation of an emulsion during the separa
tion of the tar and the water ana, as a result, gives rise to
difficulties in the tar separator.
One object of the invention is to provide a method
which enables the development of dust, when feeding coal into
coke ovens, to be restricted.
Another object of the invention is to provide a method
which enables the quantity of dust carried over from the coke
oven chambers to the collecting means to be greatly reduced from
that observed heretofore.
These objects, as well as others which will become
apparent hereinafter, are achieved in accordance with the inven-
tion. According to one aspect of the invention, there is pro-
vided a method of restricting the development of dust when feed-
ing coal into a coke oven which comprises contacting the coal
with coal tar. The thus-treated coal is admitted into the coke
oven in such a manner that the coal descends into the coke oven
by gravity, ;
The novel~ features which are considered as character-
istic for the invention are set forth in particular in the ap-
pendea claims. The invention itself, however, both as to i~s
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l construction and its method of operation~ together with addi-
tional objects and advantages thereof, will be best understood
from the following description of specific embodiments when
read in connection with the accompanying drawing.
The single FIGURE is a schematic representation of
one form of arrangement which may be used for carrying out a
method according to the invention.
It has now been found that a substantial reduction
in the quantity of dust carried over from the co~e oven cham-
bers into the collecting means during the filling of coal into
coke ovens may be achieved in that the coal is wett~ with coal
tar and the thus-treated coal is permitted to descend into the
ovens by gravity.
A particularly advantageous embodiment of the inven-
tion contemplates feeding preheated coal into a coke oven.
The preheated coal is contacted or wetted with about 0.5 to 3
percent by weight of bituminous coal tar and the thus-treated
coal is introduced into the oven by pouring it through at least -
: ~. two or three filler caps or filler openin~s provided in the roof
20 or ceiling of the oven. :
The invention is based on khe recognition that, when
the coal is introduced into the coke oven by pouring that is, :
when the coal is essentially permitted to slide into the coXe
oven under the influence of its own weight, no ignitions or -
explosions will occur if the hot coal, which is ~enerally
preheated to temperatures between about 150 and 250C, is wetted
with tar. The observation that this is so may be expl.ained, on
the one hand, in that essentially only tapered o~ conical piles
of coal are formed in the oven chamber when using this filling
technique. The coal gradually travels to the chambar walls along
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1 these piles and, by virtue of the gradual appro~ch of the c~al
to the chamber walls, a spontaneous or abrupt heatin~ of the
coal particles impinging the chamber walls does not occur. On
the other hand, the degree to which dust clouds form is in any
event less than that when using pneumatic filling techniques
were large dust clouds are artificially f~med by ~he gas used to
transport ~he coal and where the formation of dust clouds is sub-
stantial despite the addition of residual oil or pitch.
As mentioned above, the coal is advantageously
introduced into the coke oven by pouring it through at least two
or three filler caps or filler openings pro~ided in the roof or
ceiling of the oven. The reason why it is of advantage to admit
the coal through at least two or three openings resides in that
it might not otherwise be possible to obtain a reasonably uni-
form filling of the coke oven with coal. In the prior art, where
the coal is provided with an impetus by the gas used to pneuma-
tically convey the coal into the coke oven, this consideration
is not of particular consequence.
The result achieved in accordance with the invention
is particularly surprising since it would be assumed that tar,
which has a relatively substantial proportion of low boiling
point hydrocarbons, would sooner be capable of leading to ex-
plosions than coal.
Tar has the advantage that it distributes itself
over the coal particularly rapidly and uniformly. This is pro-
bably due to the close relationship between tar and coal and,
for a preferred embodiment of the invention, between bituminous
coal tar and bituminous coal, and also to the proportion of low
boiling point substances contained in the tar. It is apparent
3~ that tar is more strongly and more rapidly absorbed by the coal
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1 than is residual oil. On the basis of this, and on the basis of
the filling techni~ue selected by the invention, it becomes clear
that the "carry o~er" when using the invent~on lies well beneath
that observed when using the prlor art methods.
It is possible to utilize a special mixing de~ice
for the purpose of wetting the coal with the coal tar, preferably
bituminous coal tar, but this is unnecessary.
The good wetting ability of the coal tar is not
affected by water~ In this connection, it may be mentioned that it
is particularly advantageous to use coal tar which has been derived
from the same type of coal as that being fed into the coke oven
and which is contacted with the coal tar. Such coal tar may be
obtained from the collectin~ means located exteriorly of the coking
chamber. The coal tax generated in the collecting means is usually
subjected to a water rinse by the water admitted into the collect-
ing means and is thereafter usually conveyed through a tar sepa-
rator for the purpose of recovering the same for use in wetting
the coal. Although, as a rule~ water from the water rinse adheres
to the crude tar subsequent to its removal from the collecting
means, and also subsequent to its recovery from the tar separator,
this water does not affect the good wetting ability of the coal
tar.
The w~ter content of the tars contemplated by the `
in~ention is generally bet~een about 3 and 7 percent by weight~
It has been found that it is preciseIy this water content which,
in itself, is relatively low~ that sigificantly enhances the dis-
tribution of the crude tar o~er the coal~ Presumably~ the water
content of the tar acts as a wettin~ a~ent between the crude tar
and the preheated coal,
This effect, that is, a wetting agent effect, may be
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1 enhanced by adding surfactants, which are themselves known,
to the water-containing tar. The surfactants contemplated by
the invention are, for the most part, relatively highly soluble
in water and are more effective in water than in organic media.
Water containing crude tar combined with such surfactants thus
provides a particularly effective additive for the binding of
dust to the hot coal. The surfactants may be combined with the
tar in quantities of up to about 1 percent by weight. Exemplary
of the surfactants which may be used are the known sodium and
potassium soaps, sulfonates of fatty alcohols and fatty alcohol-
polyoxyethylene products.
It is advantageous to spray the crude tar onto
the preheated coal immediately after termination of the pre-
heating operation and before the introduction of the preheated
coal into the transporting device which conveys the coal to
the coke oven. In this manner, there is achieved, as a favorable
side effect, the result that the transporting devices are pro-
vided with a certain amount of lubrication and thus operate more
silently. Heretofore, transporting devices such as, for instance,
chain conveyors, emitted very loud and bothersome soundsO It
will be understood that, aside from the reduction in noise level
achieved by virtue of the lubricating effect, the wear to which -
the transporting devices are subjected is reduced.
The coal may be preheated by forming a fluidized
bed of the coal. When the coal is heated in a fluidized bed, a
portion of the finely divided coal i9 carried away by the gase-
ous medium which is used for bhe fluidization and which may ~ ;
also serve as a heating agent. This portivn of the coal may be
recovered from the fluidizing medium in one or more cyclones.
It is particularly advantageous, as regards the ~ffectiveness
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1 of the tar addition r for the total requisite quantity of tar
to be mixed only with the finely divided coal recovered from
the cyclone or cyclones and to then combine the thus-wetted
finely divided coal with the remainder or bulk of the preheated
coal.
It is to be understood, however, that it is possible
to add the tar to the pxeheated coal at plural locations of the
path along which the coal is transported to the coke oven, that
is, it is possible to add a portion of the total requisite quan-
tity of ~ar to the preheated coal at each of a plurality of lo~
cations of the path along which the coal is transported.
As mentioned previously, the coal tar distributes~itself over the heated coal with substantially greater rapidity
and uniformity than residual oil, and this is especially so when -
the coal tar has been derived from the same type of coal as that
being coked, e.g., bituminous coal tar when coking bituminous
coal. Presumably, this difference between coal tar and residual
oil is due to a certain structural relationship between the coal
and the tar derived therefrom as well as a broader boiling pro-
- 20 gression for the tar. The structure of a particular type of coal
such as, for instance, bituminous coal, varies considerably from
mine to mine, however. Therefore, it is understandable that the
best results with respect to a rapid and homogeneous wetting are
obtained with that tar which is derived from the same sort of
coal as that to be contacted or sprayed with the tar, that is,
the best results are obtained with tar derived from coal coming
from the same source as that to be contacted with the tar. Ac- -
cordlngly, it is advantageous to always use the tar generated in
the apparatus in which the preheated coal is coked.
The invention will now be further described with
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1 reference to the single FIGURE.
Coking coal which, in general, has a particle size
of 0.06 to 6 millimeters, is obtained from a supply container l.
From the container 1, the coal is fed into the bottom of a first
pneumatic conveying dryer via a conduit 2. The coal travels up-
wardly through the dryer 3 and, concomitantly~ is subjected to
a first drying and preheating stage.
The coal leaves the dxyer 3 through a conduit 4
and, from the latter, is introduced into a cyclone 5 where it is
removed from the gas which entrained it and carried it through
the dryer 3. From the cyclone 5, the coal slides to the bottom
of a second pneumatic conveying dryer 7 via a conduit 6~ The
coal travels upwardly through the dryer 7 and, simultaneously, is
subjected to a second drying and preheating stage.
The coal l~aves the dryer 7 through the top thereof
and enters a conduit 8 from which it is introduced into a cyclone
9. In the cyclone 9, the coal is removed from the gas which en~
trained it and carried it through the dryer 7. ~rom the cyclone
9, the coal is forwarded to a storage and feed container ll via
a screw conveyor 10.
The gases in the cyclone 5 containing the fin~
portions of the coal are withdrawn from the cyclone 5 via a con-
duit 19. The thus-withdrawn combustion gases are then admitted
into cyclones 12 and 13 wherein they are freed from the fine por-
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tions of the coal, that is, the coal dust. The thus-recovered
fine coal is forwarded to the screw conveyor 10 through conduits
14 and 15.
The heating and conveying of the coking coal is
effected with gases obtained from a combustion chamber 16. The
hot gases produced therein, for instance, by the combustion of
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1 oil, initially flow through a conduit 17 into the dryer 7. After
passing through the dryer 7, the hot combustion gases then pass
through the conduit 8 into the cyclone 9 together with the coal
which has been preheated in the dryer 7. From the cyclone 9, the
hot combustion gases flow through a conduit 18 into the dryer 3.
In the dryer 3, the hot combustion gases convey
the initially moist coal to and through the conduit 4 and into
the cyclone 5. From the cyclone 5, the hot gases flow through the
conduit 19 into the cyclones 12 and 13 mentioned earlier. The
hot gases leave the cyclones 12 and 13 via conduits 20 and 21
and thereafter are conveyed into a conduit 22. The conduit 22
opens into a wet washer 23 and a desired portion of the hot gases
flowing through the conduit 22 may enter the washer 23. The gases
entering the washer 23 leave the apparatus as purified gases via
a conduit 24.
A conduit 22a branches off from the conduit 22 and
leads to the combustion chamber 16 and~all or a portion, as de-
sired, of the hot, water-containing gases flowing through the
conduit 22 may be branched off through the conduit 22a. The hot
gases flowin~ through the conduit 22 contain water since they
; have been used for drying of the initially moist coal. The hot,
water-containing gases (vapors) withdrawn from the conduit 22
via the conduit 22a ~e returned to the combustion chamber 16.
Prior to entry of the coal into the storage and feed
container 11, the preheated coal is sprayed with crude tar at the
locations indicated by the arrows marked 25. Particularly favor-
ably, the preheated coal is sprayed with crude tar in the screw
conveyor 10 at or adjacent the inlet provided for coal of dust- ; ;
like form. The gases released may escape from the screw conveyor
; 30 10 into the vapor line 22a Via a conduit lOa. ~;
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l When the coal stored in the container 11 is to be
coked, the coal slides out of the container 11 into a chain con-
veyor 26. The conveyor 26 conveys the coal to~conduits 27 and 28
through which the coal is fed into a coke oven 29. It is possible
to spray crude tar into the conveyor 26 also as indicated by the
arrow 25a.
An uptake 30 is connected to the coke oven 29. The
reference numeral 31 identifies a collecting means in which the
respective "carry over" is determined.
The following Example is intended to further illus-
trate the invention and is not to be considered as limiting the
same in any manner.
EX~MPLE
A mixture of bituminous coals obtained from the
Alpheus and Corkn mines of the United States has a volatile com-
ponents content of 28 percent. The coal is heated to 190C by
; pneumatic conveying techniques and is then charged into an en-
closed mixing screw or conveyor~ Upon entering the screw or con-
veyor, the coal is sprayed with 2 percent by weight of bituminous
coal tar (containing 4 percent by weight of water) which has pre~
viously been heated to 70C. The sprayed coal leaves the conveyor
or screw and enters an intermediate or feed cont~iner. From the
container, the sprayed coal travels onto a chain conveyor having -~
a length of 70 meters. The conveyor opens into a charging hopper.
From the hopper, the sprayed coal is permitted to slide intv a ~ ;
coke oven chamber via conduits which are connected to the filling
holes of the oven chamber. After the filling operation, the
"carry over" is determined in the collecting means. The "carry
over" is found to be 6 to 8 kilograms of coal dust per ton of
coal charged or poured into the coke oven chamber~
I, instead of bituminous coal tar, the coal is ad~
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1 mixed with a mixture of residual oils and pitch having a tem-
perature of 70C, the "carry over" amounts to about 12 kilograms
of coal dust per ton of coal poured into the coke oven chamber.
If, further, the thus-treated coal is pneumatically conveved into
the oven, rather than being poured in, a "carry over" o~ more than
15 kilograms of coal dust per ton of coal charged is observed.
It will be understood that each of the elements de-
scribed above, or two or more together, may also find a useful
application in other ~ypes of operations differing from the types
described abovev
While the inven-tion has been illustrated and described
as embodied in a method of restricting dust development when feed-
ing preheated coal into coke ovens, it is not intended to be limit-
ed to the details shown, since various modifications and structur-
al changes may be made without departing in any way from the
spirit of the present invertion.
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