Improvements in the Treatment of Coal-slime, and Apparatus therefor.
Year: 1895

page_text: Date of Application, 6th Aug., 1895-Accepted, 19th Oct., 1895
COMPLETE SPECIFICATION.
Improvements in the Treatment of Coal-slime, and Apparatus
therefor.
I, GOTTFRIED BACHER, of Kladno, Bohemia, in the Empire of Austria,
K.K. Mining-councillor and Manager, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
This invention relates to the preparation of coal-slime, that is, small coal and
coal dust mixed with water, or of the lump coal, which is to be separated from
the mass, with or without separation of the sediment therefrom, by submitting it
to the action of a flow of water, capable of regulation, in a direction opposed to
the natural subsidence of such materials, so as to obtain, in the first case, only
lumps subsiding similarly, or in both the last cases the separation of coal from the
mass with or without the removal of the adherent slime or sludge.
Different arrangements of apparatus serving to carry out this process are
illustrated in the accompanying drawings.
The apparatus shown in Figs. 1, 2 and 3 is designed for the treatment of large
quantities; while that shown in Figs. 4 and 5, may be used with success for
treating small quantities.
The two apparatus represented in Figs. 6 and 7, serve for the separation of the
coal from the slime; the former however, (Fig. 6) being without, but the latter
(Fig. 7) with an arrangement for the removal of the adherent slime.
All these apparatus are based upon the same fundamental conception; never-
theless it will be well, for clearness' sake, to describe them and their functions, each
separately.
The apparatus for the preparation and treatment of coal-slime, shown in Figs. 1
to 5, consist each of a settling tank A, through which a contrary current of water
(ie. in the upward direction) is made to pass, by means of the compartment a filled
to a higher level than the slime in the settling tank.
The slime, containing small pieces of coal, is passed through the settling tank
from B to C (in the direction indicated by the arrow) through a stream of water
ascending from a, and the coal is therein deposited, while the ascending current
carries off the slime. For, with a velocity duly proportioned, the water divides
the mass into two parts; one of these falls to the bottom, while the other is
carried upward by the current and washed away over the edge of the tank.
The
more the velocity of the stream is checked, the greater is the part deposited.
In this way, not only a separation of the coal takes place according to the size
of the lumps, but also according to the proportion of ashes contained in the bulk;
inasmuch as the deposited coal, according to practical experience, contains only
half as much ashes as the part carried away, and is, as a rule, already clean enough
for use in the preparation of coke, or for heating purposes, without further
treatment. This circumstance is explainable by the fact that, almost without
exception, small or fine coal contains a larger proportion of ashy constituents, the
finer it is. The coal thus deposited, in lumps nearly all of one size, is removed
from the bottom of the apparatus by any well-known means.
Should it be desired to remove more ashes from the coal thus recovered, this is
best attained by screening, so as to divide it into two classes, a coarser, and a finer
class of coal. The coarser coal, i.e. the coal kept back by the screen, contains

page_text: now only about one half as much ashes as the mass contained, before the screening;
while the finer part, viz., that which passed through the screen, contains about
6 or 8 times as much ashes as the first.
This favourable result of preparation is confirmed by bodies of different specific
gravities falling or being deposited simultaneously in water.
The product thus obtained in an ascending current is a mixture of coarser
grained lumps, or specifically lighter coal and consequently with a smaller
proportion of ashes, and of finer grained coal, specifically heavier, and therefore
containing a larger proportion of ashes.
If this mixture be screened into two classes, a coarser and a lighter class, it is
clear that at the same time a separation results, according to the proportion of
ashes contained.
As soon as, in the above described apparatus, the separation, out of the coal
slime, of the uniform coal is effected, according to the velocity of the water-
current; and if it be desired to obtain therefrom more of the fiuer-grained coal,
it will be necessary to repeat the process, and pass the product through a second,
third and if desired further apparatus similar to that described, with however a
lower rate of speed, of the ascending water-current introduced whereby again a
uniform but finer sized coal than in the first apparatus, will be obtained.
This, similarly, contains only about one half of the proportion of ashes contained
in the part washed away, and, as in the former case, is sufficiently clean for use in
the preparation of coke or for heating purposes without further treatment; and
if, again, this be screened (with a corresponding screen) into two classes, the
proportion of ashes contained in the part which does not pass through the screen
will as in the first operation, likewise be decreased by somewhere about the half,
while the screenings will show a proportion six to 8 times as large.
Whether a single apparatus suffices, or two or more should be employed, will
depend upon whether the difference of the specific gravities, of the coal itself
and of the splint or schistous coal and other mixtures containing a large pro-
portion of ashes or cinder, he greater or less; and in particular also upon whether
the coal-slime is more or less strongly mixed or analgamated with slip or clayey
sludge.
In general one or two apparatus will suffice.
The yield in clean coal, which, nearly approximating to coal washed in a
precipitating apparatus, will amount to from forty to seventy per cent.; and,
consequently, this improvement is especially adapted for the treatment of coal
of all sizes which are too small for the advantageous and satisfactory use of such
ordinary washing apparatus, say in dimensions of from two millimetres downwards.
The apparatus illustrated in Figs. 6 and 7 is constructed on the same principles as
that above described, and serve for the separation, from the washing sludge derived
from the ordinary precipitating apparatus, of coal of all sizes as above. For
instance, if one conducts the washed coal and its sludge through G into a settling
tank A through which passes an ascending water-current from a device a, the coal
only descends through the ascending stream, while the slime or sludge is driven
upwards by the water-current and washed away over the edge H.
By regulating the speed of the ascending current, one is able to cause the
deposit of the smallest appreciable piece of coal which it may be desired to
recover.
The still finer coal particles, particularly, however, the slime and sludge charged
with ashes are driven back and carried away; whereby is attained the result that
the coal thus separated contains from one to two per cent. less ashes than by any of
the processes hitherto employed for the separation of washed coal, in which a
considerable part of slime and sludge containing a considerable proportion of ash
and cinder still remains behind between the coal-particles.
To each individual particle there remains adherent a thin coating of slime and
sludge, which augments the quantity of ash and cinder contained in the washed
coal, in the same proportion as in the slime, the clayey sludge and the like increase.

page_text: This adherent slime or the clayey sludge therein contained can, in many cases, only
le entirely removed by mechanical treatment.
This task would be effectually executed by bringing into combination, with the
above-described process, a scrubbing or scouring apparatus, acting in such manner
that the coal to be freed from slime or sludge should be set in motion so that its
particles rub against each other, and be subjected, while in motion, to a water-
current flowing in the opposite direction (i.e. a counter-current) which may wash
away the slime and sludge (scoured away from the coal).
The washing-off can take place through a conveyor (such as e.g. the worm or
screw J, Fig. 7) which takes away the coal from the settling-tank or apparatus,
freed from slime by means of the ascending water (stream-apparatus), in which it
is collected together; and this water-current may also serve to carry away all the
slime scoured from the coal, as shown in Fig. 7.
For the removal, however, of the deposited coal from the places which it thus
reaches, after passing through the settling-tank and having been exposed to the
flow of the upward water-current, any well-known devices may be employed and
similarly the screening of the uniform small-coal deposited from the slime, any
known sieve-devices may be used.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is-
1. A process for the treatment of coal-slime consisting in subjecting it in one
or more settling tanks to a preliminary separation and to a final separation of the
coal and slime in an ascending water-current for the purpose of obtaining the
separation of a fine uniform coal free from any considerable proportion of ashes
which for the sake of a further decrease in the proportion of ash and cinder
retained can be classified by screening and so divided into grains or particles of
different but uniform dimensions.
2. The employment of the process claimed in Claim 1 for the purpose of
separating washed coal from the washing-slime.
3. For treating coal slime a process for the removal of the adherent slime
consisting in submitting the coal in a washing apparatus to the action of a counter-
current either in combination with or independent of the process claimed in
Claim 2.
4. In processes such as described in Claims 1 and 2 an apparatus comprising a
settling tank such as A provided with a compartment a wherein the downward
pressure or head of water causes a water current to flow down into the settling
tank A and then up thereby creating a counter-stream which carries away the
slime or finer-grained coal and washes it over the edge C of the vessel substantially
as described and illustrated in the accompanying drawings.
5. In apparatus for carrying out the process claimed in Claim 3 an agitating or
conveying device J by means of which the coal-particles are carried away and
subjected during their passage to the action of a counter-current of water
substantially as described and illustrated in the accompanying drawings.
6. The combination and arrangement of parts constituting the complete coal
slime treating apparatus substantially as described and illustrated in Figures 12
and 3 or Figures 4 and 5 Figure 6 or Figure 7 of the accompanying drawings.
Dated this 6th day of August 1895.
BOULT & WADE,
Agents for the Applicant.