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Патент USA US2108495

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Feb. 15,1938.
‘
2, 108,495
N. D. LEVIN
METHOD OF AND APPARATUS FOR CLEANING COAL _
“ Original Filed Oct. 11, 1934
6 Sheets-Sheet 1
N.
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ATT'Y
Feb. 15, 1938.
N. 'D. LEVIN
2, 108,495 '
METHOD OF AND APPARATUé FOR CLEANING COAL
Original Filed Oqt. V11, 1934
6 Sheéts-Sheet 2
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BY
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ATT'Y
Feb. 15, 1938.
'
up, LEVIN
' 2,108,495
METHOD OF AND APPARATUS FOR ‘CLEANING GOAL
Original Filed Oct. 11, 1934
6 Sheets-Sheet 4
Feb. 15, 1938.
‘
N'_ D_ LEvm"
2, 1 08,495
METHOD OF AND APPARATUS FOR CLEANING COAL
briginal Filed Oct. 11, 1934 '
, 6 Sheets-Sheet 5
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‘Patented Feb. 15, 1938
* 2,108,495
UNITED STATES ‘PATENT- OFFICE
ING COAL
Nils n. Levin, Columbus, Ohio, assignor to The
Je?rey Manuiaoturingcompany, a corpora- _
tion of Ohio
Application October 11, 1934, sews...‘ 147,901
Renewed July 31, 1937
’ 12 Claims. (Cl. 209-173)’
My invention relates to the separation of ma
Fig. 6 is a diagrammatic plan view of the ap
terlals according to their speci?c gravities and
the re-clainiing of the solid constituents of the
separating medium, and one of the objects of my
invention is the provision of an improved method
tank, supply tank and settling tanks;
of separating coal from its impurities by increas
sediment from the settling tanks shown in either
ing the efficiency of operation.
Fig. 4 or Fig. 6;
paratus shown in Fig. 5, connected to a mixing '
Fig. '7 is diagrammatic view illustrating con
veying apparatus which may be used for removing
-
Another object of the invention is to provide im
'
'
proved apparatus for reclaiming the solidcon
stituents oi’ the separating medium for gravity
separation of impurities from coal.
A further object of the invention is the prel
liminary treatment of raw coal or run of mine
plenishing water in the washing tanks; ‘and
coal for gravity separation of impurities from the
coal employing insoluble material mixed with
water .so that when such coal impurities are re
out or said medium.
which will be carried out with the separated coal
into the washing tanksvfor recovery. in the ‘system
shown in Fig. 4 or in thesystem shown in Fig. 6.
'
A further object of the invention is the pro
vision of a system, of coal cleaning apparatus '
comprising separating mechanism, washing mech
anism, reclaiming mechanism and automatic
means for maintaining the liquid in the washing
25 mechanism at a predetermined level.
More particularly it is the object of the'present
‘invention to provide improved apparatus for
cleaning .coal and carrying out an improved
method therewith to reduce the expense of opera- '
30 tion to a minimum by enabling the use of insoluble
granular materials in their natural states and
A
Fig. 10 is a curve illustrating a method of
‘adapting a separating medium which will retain
a, maximum amount of its solid constituents, so as
.to reduce the amount of such solid constituents
moved from the separating medium a minimum
amount 01' such solid constituents wili'be taken
'20
.
Fig. 8 is a diagrammatic ,elevational view of
the system shown in Fig. 4, to illustrate the rela
tive elevations of the various tanks;
10
Fig. 9 is a wiring diagram to illustrate the
automatic float control of lthe pump for re
In Figs. 1 and 2 I have shown a supporting
, frame ii on which are mounted the separating
tank i2 and the series of washing tanks it, it
and I5.
The raw or run of mine coal may be
introduced into the hopper l6, as shown in Fig.
1, in the bottom of which the discharge of the
coal is regulated by the vertically slidable gate
11. The separating medium, comprising natural
clay and granular sand in its natural state mixed
with water and an electrolyte, as hereinafter more 30
without comminution, in the separating medium,
fully explained, may be of varying depth in the
tank I! according toconditions. The impurities
and in the washing of the separated coal reclaim
ing such solid materials as. may adhere thereto
which sink in the separating medium are received
upon emerging from the separating medium.
Other objects of the invention will appear here
inafter, the novel features and combinations be
ing set forth in the appended claims.
In the accompanying drawings,
Figs. 1 and 2, placed end to end, illustrate ap
paratus including" a separating tank for cleaning
coal and for washing the same successively in a
series of washing tanks;
‘
-
‘ Fig. 3 illustrates apparatus including a tank
for immersing the raw coal or run of mine coal
before it is conveyed to the separating tank, the
latter being ‘also shown connected to the series
of washing tanks similar to those shown in Figs.
1 and 2;
'
.
Fig. 4 is a diagrammatic plan view showing the
arrangement of the tanks illustrated in Fig. '3,
together'with settling tanks and. mixing storage
tanks;
,
g
I Fig. 5 is an elevational view illustrating the ‘ap
paratus shown in Figs. 1 and 2;
_ ‘
'
by the conveyor l8 comprising the ?ights i9, i9.
These ?ights are adapted to travel in the direc
tion of the arrow 20 to convey the impurities, such
as slate, to the chute 28 from which such im
purities are delivered to the endless belt conveyor
The coal which is capable of ?oating on‘ a 40
separating medium in the separating tank i2 is
crowded toward the left, as-viewed in' Fig. 1, by
the incoming raw coal, and such separated coal
is received by the conveyor 23, comprising the 1'
?ights M, M. The cleaned coal is conveyed up
wardly along an incline in the direction of the
arrow 25 where it is discharged into the tank 23
in which a de?ector plate 26' guides the coal to
the conveyor 2i comprising the flights 23, 2t.
Inasmuch as the washing tank It is ?lled with
water, the cleaned coal will tend to sink therein
and consequently it is desirable to provide an in
clined plate 29 for the ?ights 28 so that coal
which reaches the plate 29 may be scooped from
the semi-circular receiving portion 3% to move 55
-
2,108,495
upwardly along the incline in’ the direction of
tion while the other is being used for receiving
the arrow 3| for discharge into the next washing
tank I4. Further washing in the tank I4 is effect
ed by the discharge of the coal therein for trans
fer by the conveyor 32 into the tank I5. In the
latter the conveyor 33 transfers the washed coal
to the discharge chute 34 from which it ?ows
to the belt conveyor 35 for transfer away from the
material from any one or more of the tanks I3,
washing apparatus in the direction of the arrow
10 35
At the right-hand end of Fig. 1 is shown in
dotted lines the position that the operating elec
tric motor 31 occupies on that side of the frame
II remote from the sprocket chain gearing 38
which is connected to simultaneously ‘drive all of
the conveyors shown in Figs. 1 and 2. The motor
31 is connected by reduction gearing 39 and the
sprocket gearing 40 to that end of the shaft 4I
remote from the sprocket chain 38. That is to
20 say, the driving connection from the motor 37 is
to one end of the shaft 4|, and to the opposite
end of the latter is connected the endless sprocket
chain 38 which in turn is connected to all of the
traveling conveyors to drive them simultaneously.
At the upper left-hand end of Fig. 2 is shown an
inlet port 42 and at the bottom of the washing
tanks I3, I4, and I5 are shown drain pipes 43, 44,
and 45. Inasmuch as the separating medium in
the separating tank I2 contains natural clay and
30 sand in ‘its natural granular state mixed with
water and a very small quantity of electrolyte,
a small quantity of the separating medium will
adhere to the cleaned coal which is transferred
by the conveyor 23 to the tank I3. When the con
veyor 21 operates to transfer the coal to the next
tank I4, most of the clay and sand is washed from
the coal and dispersed in the water in the tank I3
where it settles on the conical bottom so that it
may‘fiow through the outlet port 43.
If any clay and sand still remain on the coal
when introduced into the tank I3, further wash
ing occurs‘ and the clay and sand may be with
drawn through the port 44, shown in Fig. 2. Still
further washing may occur in the tank I5 and the‘
clay and sand eliminated through the outlet port
45. Clean water may be introduced intermit
tently and continuously through the port 42 for
?ow into the tank- I5 and thence into the tank
I4 and from the latter into the tank I3. The
50 upper edges 46 and 41 of the walls or separating
partitions 48 and 49 are at lower elevations than
the upper edges 50 and 5| of the end walls 52
and 53. Consequently, when the tank I5 is ?lled
it may over?ow the edge 46 into the tank I4, and
when the latter is ?lled it may over?ow the edge
41 into the tank I3.
'
Regulation of’ the flow of the sediment from
the conical bottoms of the tanks I3, I4 and I5
through the outlet ports 43, 44, and 45 may be
60 secured by means of the system diagrammati
cally illustrated in Fig. 6. Manual valves 54, 55,
and 56 may be placed in the pipes which lead
from the ports 43, 44, and 45 so that each of the
tanks I3, I4 and I5 may be individually drained
to such an extent as to remove the sediment from
the conical bottoms thereof. When any one of
the valves 54, 55, 56 is opened the mixture of
sediment and water will ?ow into the pipe 57
which is connected by the branch pipes 58 and
59- to the settling tanks 50 and BI. The latter are
at lower elevations than the bottoms of the sedi
mentation tanks I 3, I4, and I5,4and ?ow thereto
is controlled by the manual valves 62 and 53.
It is preferred to employ two settling tanks
75 60 and 6I_so that one may be used for sedimenta
I4, I5. For instance, if the valve 82 is closed and
the valve 83 is open the tank 84 may be used for
sedimentation._ During operation of the coal
cleaning apparatus including the washing mecha
nism, it is preferred to close the valves 55 and 56
and regulate the'opening of the valve 54 so that
as the ‘clay and sand settle in the bottom of the
tank I3 it will ?ow immediately into the settling
tank 8|, the liquid in the tank I3 being auto
matically replenished by means of the pump 34
operated by the electric motor 65 under the con
trol of switch mechanism. When the pump 64
operates, the valve 56 is closed and the valve 61
is opened so that water will be withdrawn from
the tank 80 into the pipe 42 for ?ow into the tank
I5. After clear water has been obtained by sedi
mentation in the tank 6|, the valve 62 may be
opened, the valve 63 closed, the valve 65 opened
and the valve 51 closed. Then when the pump 54
operates, clear water ‘will be withdrawn from the
tank 6| through the pipe 68 into the pipe 42 and
thence into the tank I5.
.
In Fig. 6, 69 designates a mixing tank in which
the clay, sand, electrolyte and water may be
thoroughly intermixed while the valve ‘III is
closed. It is desirable to effect this mixture in
a separate mixing tank so that it may be per
mitted to age by standing in a quiescent condi- -
tion for a period of approximately twenty-four
hours, thereby rendering the electrolyte more
e?icient in its e?ect on the clay and sand con-'
stituents.
After the separating medium has been aged -
for a predetermined period of time, the valve ‘I0
may be opened to permit the mixture to ?ow into
the storage or supply tank ‘II which is larger in
capacity than the tank 59, and from which the
medium may flow into the separating tank I2
under the control of the manual valve ‘I2.
In the system illustrated in Fig. 4, mixing and
storage tanks are provided as indicated at ‘I3 and
‘I4 which are connected through manual valves
‘I5 and ‘I6 to the pipe ‘II which leads to a float
controlled valve ‘I8 in the separating tank l2’.
When the valve ‘I5 is' closed the mixing tank ‘I3
may be used for permitting the mixed ingredi
ents of the separating medium to age. During
the aging period the other tank ‘I4 may be used
for storing the previously aged mixture so that
when the valve ‘I5 is opened, flow will take place
automatically from the. tank ‘I4 to the separat
ing tank I2’ under the control of the float valve
‘I8. Consequently, during the operation of the
cleaning and washing mechanism illustrated in
Fig. 3, the separating medium carried out from
the separating tank I2’ by removal of the coal
and impurities, will be automatically replenished
under the control of the ?oat valve ‘I8. When 60
the valve ‘I6 is closed and the valve ‘I5 is opened
the flow will be from the tank ‘I3 into the
tank I2’.
‘
In Fig. 8 I have shown the relative elevations
of the various tanks, the mixing and storage
tanks ‘I3 and ‘I4 being located at such elevations
as to permit the separating medium to ?ow by
gravity into the separating tank I2’ as permitted
by the automatic ?oat valve ‘I8.
The operation of the electric motor 65 for driv 70
ing the pump 64 may be controlled by means
of the electric ?oat switch ‘I9, shown diagram
matically in Figs. 8 and 9. When the water in
' the tank I5’ falls to the level indicated at B0 in
Fig. 9, the ?oat 8| will descend sufficiently on its 75
'3
2,108,495
pivot 82 to cause the enclosed ‘mercury switch ' ing vtanks while sedimentation ‘is taking place in
83 to connect‘the conductors 88 and 85 where
the other sedimentation tank. The coal dust
' upon the solenoid" will be energized since it which may be mixed with the clay and sand can
will be connected across the‘ mains 81 and 88. readily be separated therefrom by ?otation on a
When the-switch 88 is- closed and the solenoid liquid separating medium, and the clay and sand
86 energized, the latter will‘ e?'ect the closure of recoveredin this manner may be re-used'in the
I the motor switch 88. The motor 85 will then be
mixing tanks ‘I3 and ‘I4.
connected by means of the conductors 8|, 82
'
’
* In the co-pending application of applicant and '
across the supply mains, and the pump 88 will , Samuel H. Yost/for an Improvement in method
of cleaning coal and ?uid-separating'mediums
the settling tanks 88 or BI through the pipe 82' therefor, Serial No. 747,906, ?led Oct. 11, 1934,
into the tank I5’. When the waterin the tank the‘ preferred separating medium for use in the
I5" reaches the level indicated by the dotted line tank I2 or tank I2’ is described and claimed,
10 be permitted ‘to draw "clear‘liquid from one of
position 93 in Fig. 9, the ?oat 8| will be moved
whereas the present application adds the ‘pre
15 ‘to. its dotted line position 8|’ to e?‘ect opening
of the switch ‘I8 which will cause de-energiza
liminary step of wetting the raw coal in the tank 15
85 and also includes the washing of the separated
coal after leaving the separating‘ tank, and in
addition I have disclosed in. Figs. 4, 6, 8, and 9
systems of handling the liquids and solid ma
terials immersed therein. I, have also added the
curve shown in Fig. .10 to illustrate the tests
which may be carried outso as to reduce to‘ a
minimum the amount of solid constituents car
ried out from the separating medium when the
cleaned coal and the impurities are removed from
tion of thesolenoid 86 andthe dropping of the
"switch 88 to its dotted line position, thereby cut-'
ting off the motor 65 and stopping the .pump 84.
20
‘The operation of the valves 58, 55, 56, 62, 63,
66, and 61, in the system shown in Fig. 8, will be
the same as described in connection with Fig.‘ 6.
The separating tank I2’ in Fig. 8 is provided with
a drain valve 94. This valve is opened only when
25 it is-desired to drain the separating tank I2’.
By referring to Fig. 3 it will be seenthat the
tank 95 is provided for containing water into
the tank l2 or tank I2’.
which the raw coal or run of mine coal may be
introduced from the chute 86. By means of the
30 conveyor!" the wetted coal is removed from’the
"
crevices therein‘ so‘ that less of the solid con 80
stituents of the separating medium in the tank
I2’ will adhere to‘ the separated coal ‘and im
purities when they areremoved from the tank
I2’. Inasmuch as the washing system herein
disclosed is arranged and. operated to obtain 35
the greatest’ ef?ciency, the operating medium is
tank 95 tothe chute 88 for ?ow into the separat
ing tank I2’. The impurities which sink in the
separating’ medium in the tank I2’ are removed
by means of the travelingconveyor I8’ to the
35 chute 2I' and thence to the belt conveyor 88.
The motor 31' may be connected by means of the
40
.
In the ?rst place it should be understood that
the principal object of wetting the raw coal
preliminarily in the tank 85 is to fill up the
sprocket chain 38’ to all of the conveyors in the ‘
so composed as to retain the greatest amount
whole ‘system shown in Fig. 3. The sprocket
chain should be driven in the direction of the
possible of its solid constituents by preventing
the removed coal and impurities from carrying
I88.'
'
'
',
.
out ‘any more than is necessary. In order to
The bottom of the tank 85 is preferably conical fully understand the signi?cance of the curve
in shape and is provided with -a draining port ' shown in Fig. 10, it will be necessary to describe
IIII which is connected to the pipe I82 shown in the preparation of the separating medium used
in the tank I2 in the system shown in Figs. 1,
' Fig. 8. The draining of the tank 85 may be con
45 trolled at intervals by'the valve I83. Although
2. 5, and 6, and in the‘tank I2’ in the system
shown in Figs. 3, 4, and 8.
the raw .coal is screened and de-dusted before
arrows
entering the tank, 85, the wetting of the coal
eifects further elimination of the coal ,dust, and
'
In order to predetermine. the specific gravity
of the separating medium or mixture to 'be used
when the water in the tank‘ 85 becomes con-' in the systems disclosed in the accompanying
drawings, the raw coal or run of mine coal to
50 taminated with coal dust it may be drained by
be cleaned is analyzed by methods of sampling,
opening the valve I83-and permitting the sedi
_ ment to ?ow intoone of the settling tanks 68 or
6I. It may also occur in practicethat the raw
coal introduced into the tank 85 even after
55 screening and de-dusting, has considerable sand
and clay adhering thereto which will be washed
off by being introduced into the tank, 85 and the
,washed raw coalmay be conveyed out of the
same bythe conveyor 81.
-
- The solid materials which are washed from the
coal in the tanks 85, I3, I6 and I5 and allowed
to settle in the settling tanks, 58 and GI vmay be
removed therefrom by means of the dragwcon
veyors I84, I85, as shown in Fig. '7. . These con
65 veyors are operated respectively-by the motors
45
to
sink and ?oat tests, l chemical analyses, etc.
Then, depending upon what grade of purity of
coal is desired, the ‘speci?c gravity at which sep
aration should take place, when following my 55
improved methods,-is predetermined. The sep
arating medium 'orinixture is then .prepared so
that the marketable coal will float in the separat
ing tank I2 or the separating tank I2’.
-
In preparing the separating medium it is pre
ferred to follow certain de?nite formulae which
from actual tests have given the best results
but which may be varied in accordance with con- -
ditions. By using one part natural clay and four
parts natural sand, by weight, without pulveriz
I86, I81 inthe direction of the arrows I08, I88 -‘ ing or comminuting either the clay or the sand,
to‘ take the sediment from the inclined bottoms, and stirring the clay and sand in water, a me- _
*III), III to the chutes H2,- Il3,'*for ?ow into the dium of the desired speci?c gravity may be. ob
mixing tanks ‘I8, ‘I4. The motors I86,'I8l are tained with the assistance of well known tests
70 connected by the sprocket chain gearing H4, of speci?c gravities ofv mixtures of solid granu 70
I I 5 to the conveyors I84, I85 to drive the same in lar matter with water. The speci?c-gravity of
the direction of the arrows I88, I88. It should be the sand is approximately the same as that of
' understood, however, that the conveyors I84, I85
‘are operated‘ alternately because one of the set
75 tling tanks receives the sediment from the‘wash- '
vthe clay.‘
>
'
‘The addition of a small amount of a de?occu
lating agent such as sodium alumlnate or sodium 75
l
4
2,108,496
In the formation of the separating medium by
mixture of the ingredients in the mixing tanks
‘I! and ‘ll of Figs. 4 and 8, .or in the mixing tank
in suspension for a relatively long period of time, . 8! of Fig. 6, it is important to follow certain
thereby rendering the ?uid'mixture very efii-, de?nite formulae according to conditions. It has
cient in the gravity separation of impurities been found from actual tests that under certain
silicate to the mixture of natural clay and nat
ural sand in the water, will cause the clay and
sand after being stirred in the water. to remain
from coal with littleor no agitation of the sep
arating‘medium.
-
'
"
-
In gravity separation of impurities from coal,
10 agitation of the liquid hampers the process, and
it is therefore desirable to reduce the agitation‘
to a minimum. For instance, when the agita
tion of the liquid medium is too great, small and
?at pieces of slate will follow upward currents
15 and be mixed with the cleaned coal, thereby
rendering perfect separation impossible. How
ever, in the use of the conveyors l8 and 23 in
the'separating tank II or the conveyors II’ and
23' in the tank l2’, the agitation of the liquid
medium is so small as not to disturb'the ‘desired
separation of impurities from the marketable
coal.
If su?icient natural clay is so mixed with water
as to ?nely divide it without comminution or
pulverization, a liquid medium may be obtained
of sumcient speci?c gravity to ?oat coal, but
it will be found to be too thick or viscous for
practical use.
However, by adding the proper
amount of electrolyte such as sodium aluminate
or sodium silicate, the mixture will be rendered
more ?uid without affecting the speci?c gravity.
‘After testing various forms of natural clay, one
form of ?reclay was found that could be used
in practice without the addition of sand, but this
35 separating medium was not found to be very
, emcient.
In other words, while satisfactory re
conditions the amount of sodium silicate or so
dium aluminate for the best results in maintain
ing the clay and sand in suspension for a rela
tively long period of time without agitation, 10
should be approximately .8% of the weight or
the clay. By means of tests hereinafter explained
the critical proportions may be ascertained.
That these proportions are critical is evidenced
by‘ the fact that in the tests referred to above.
doubling the amount of the electrolyte caused a
rapid settling of the clay and sand in a mixed
mass without layering.
‘
In order to explain the procedure by which cer
tain de?nite formulae may be arrived at for obi 20
taining the best results in the use of a separating
medium for the cleaning of coal, certain actual
tests have been carried out and the results ob
served. By mixing one part Minford silt (argil
laceous material in its natural state) and four
parts of white coarse sand by weight, and adding
su?icient water to obtain a speci?c gravity of
1.55, after stirring into the mixture .8% of
sodium. aluminate, no sediment of the solid in
soluble ingredients was shown after a period of 30
twenty-four hours.
When a mixture having a speci?c gravity oi.’
1.55 was made of one part Minford silt and ?ve
parts sand and .8% of sodium aluminate in wa
ter, a very slight settlingwas observed after a 35
lapse of twenty-four hours, but in similar mix
sults may be obtained by the use of a mixture tures having one part silt and six parts sand,
of a certain clay and water without sand but
and one part silt and seven parts sand, pro
including the addition of a small amount of nounced settling occurred after a lapse of twenty
sodium aluminate or sodium silicate, the best four hours, but the settled mass was a very soft 40
results are obtained by the inclusion of natural intermixture of silt and sand such as not to inter
sand in the mixture. The use of natural clay fere with the restarting of the conveyor mecha
alone in most cases decreases the ?uidity of the nism shown in the separating tank l2 in Fig. 1 or
mixture to such ‘an extent as to slow down the in the separating tank l2’ in Fig. 3. Upon re
45 separating process as compared with the speed of ‘ starting the conveyor mechanism through such
operation ‘when natural sand is included in the
mixture, because the inclusion of the sand in- '1
creases the ?uidity of the separating medium.
Clay is an argillaceous material which is com
posed of particles in a ?nely divided state which
when mixed with water may be dispersed
throughout the volume thereof, while sand is a
non-argillaceous granular material usually found
in its natural state as silica. The particles of
clay in their natural state are relatively ?ne and
the granules of the natural sand are relatively
'coarse. Both of these materials are available at
low cost'almost anywhere in this country, and
by reason of the use of the electrolyte, prefer
ably sodium aluminate or sodium silicate, no
grinding or pulverizing of either the natural
clay or the natural sand is necessary in the for
mation of the separating medium used in my
systems illustrated in the accompanying draw
lugs.
The sodium aluminate or sodium silicate may
be a de-?occulating agent so far as the clay
suspension is concerned, but the suspension of
the sand may perhaps be best explained by the
70 fact that the sodium silicate or sodium aluminate
acts as an electrolyte to produce electrical charges
in the .clay particles to hold in suspension for a
‘relatively long period of time the natural sand
granules in intimate relation with thedispersed
15 clay in a homogeneous separating medium.
settled mass, only a slight mechanical agitation
was necessary to recondition the separating me
dium, but the homogeneous condition of the medi
um could be obtained only by su?icient agitation.
The water used in the foregoing tests was that 60
from ‘a city hydrant in Columbus, Ohio.
When Sandusky Foundry sand (10% clay) was
used in tests with Minford silt, there appeared to
be no appreciable settling aftera lapse of twenty
four hours, even when the ratio of the ingredients
was one part silt to 8 parts of sand, by weight.
Fireclay and white sand mixtures did not prove
to be as suitable as silt and white sand mixtures.
Fireclay and Sandusky sand mixtures showed no
appreciable settling after standing twenty-four 60
hours at a ratio including one part ?reclay to six
parts Sandusky sand.
Inasmuch as it consumes some timeufor the
progressive de?occulating action of the sodium .
aluminate to take place, it is preferred to age the 65
mixture for a period of at least twenty-four
hours. This can readily be done in the systems
shown in Figs. 4\and 8 where two mixing tanks
are included for alternate use.
When the Min
ford silt is used with a mixture containing city
water, it was found that the minimum de?occula
tion vwas effected by the use of sodium aluminate
over a, range of .6% to .9% as to the amount of
sodium aluminate relative to the weight of the
clay. After aging the mixture in the tank 13 or
2,108,495
the tank ‘II, the maximum de?ccculation is de
?nitely indicated at approximately .8% with a
pronounced reaction over a range of .8% to one
Sandusky'sand'by weight) in water having, in
solution .8% sodium aluminate (the separating
medium having the specific gravity of 1.53) was
about 40 pounds per ton of raw coal treated,
The percentage of the‘solid ingredients in sus I whereas with a separating medium having a spe
pension in the separating medium is much great
ci?c gravity of 1.53 and composed of 1 part silt
er for Minford silt than for ?reclay and the dura
‘and 4 parts white coarse sand in water having in
tion of the suspension is also much longer‘ for the solutlon .8% sodium aluminate, the carry-01f was
Minford silt. This is probably due to the differ;
found to be 26 lbs. per ton of raw coal treated.
10 ence in the size of the particles in the two clays. ' Even ?reclay gave better results when mixed with 10
The Minford silt is the better suspending agent coarse white sand than when mixed with the fine
of the two clays tested and the Sandusky sand, Sandusky sand. With ‘a separating medium hav
a relatively‘ ?ne sand, vis the onemore readily ing the speci?c gravity of‘ 1.53 and composed of
maintained in suspension of the‘ two sands tested. ' 1 part ?reclay and 6 parts white sand by weight
The permissible ‘sand variation for a given in water having in solution .8% sodium aluminate 15
I speci?c gravitybetween, 1.5 and 1.6 was found the carry-off was found to be 18 lbs. of solid in
to be 25 percent for practical operations. With gredients per ton'of raw coal treated, whereas
the less favorable sand, the permissible elec
with a separating medium composed of 1 part
percent.
'
,
,
Y
5
trolyte variation plus or minus from ‘the optimum ?reclay and 6 parts Sandusky sand by weight in
point of .8 percent was found to be 12 percent. water- having in solution .8% sodium aluminate
20
.That is to say, the best results are obtained with the carry-off was found to be 20 lbs. of ~ingre
.8 percent of electrolyte with a permissible range dients per ton of raw coal treated.
from .6 percent to nearly. one percent.
While therefore theoretically it may be de
Inasmuch as Minford silt is composed of ?ne . sirable to have both of the ingredients in ?nely I 5
-' ly divided particles of argillaceous material and divided ‘condition, itis more practical and eco-'
Sandusky Foundry sand is relatively ?ne, eight nomical to have one relatively ?ne as found in
" parts of sand could be held in suspension in the nature and the other relatively coarse and also
water having in solution a‘ small. quantity of \as found in nature.
\
sodium aluminate, so that there would be no
Ageing of the mixture of sodium aluminate,
'30 appreciable settling after a lapse of twenty-four water, clay and-sand greatly reduces the amount 80
hours. The highest speci?c gravity of the mix
of carry-off in the treatment of coal to separate
ture can-therefore be obtained when the argil
the impurities therefrom. The proper balance
laceous material is in a naturally ?nely divided may readily be obtained in ‘practice. Fireclay
state and the sand is relatively ?ne.
' white sand mixtures over a' range of M; to 1A; all
Bentonite is another form of argillaceous ma
settled considerably faster than silt-white sand
terial which is found in nature in a ?nely divided mixtures. But ?reclay-Sandusky sand mixtures
state and has the property _of cooperating with an showed no appreciable settling at ratios up to
electrolyte to hold ten‘part's of?ne sand in sus
pension in a separating'medium over a relatively
40 long period of time without agitation.
Fireclay is composed of particles’ in a ?nely
divided state but not as ?ne as either silt or
bentonite. However, ?reclay was found to co
act with the electrolyte to hold in suspension six
" parts‘ of Sandusky sand by weight in a suitable
separating medium because no appreciable set
tling occurredafter standing for twenty-four
hours.
'
'
- It will thus be seen that the tests which were
conducted showed that the selection of the ?nest
argillaceous material in its natural state and the
and including %.
_
’
~
Inasmuch as the argillaceous material and the
sand varies in nature in various parts of ‘the 40
country the correct formula for the separating
medium to suit conditions depends upon the clay
suspension, the sandsuspension, and the clay
sand adherence resulting from contact with
smooth‘imporous surfaces. The related deter
minations to be made are (1) the concentration
of the electrolyte such as sodium aluminate ‘or
sodium silicate to clay which produces the maxi- I
mum de?occulation of the clay, (2) the eifect
of varying the sand-clay ratios upon the dura
tion of the suspension and the homogeneity of
selection, of the ?nest sand in its natural state _ the suspended mixture, (3) the effectof .varying ‘
enabled the electrolyte sodium aluminate to act
to ,hold in suspension the greatest amount of
solid ingredients in the separating medium over
a long period'of time without appreciable set
the sand-clay ratio upon the adherence value,
and (4) the effect upon the foregoing of varying
the type of clay and sand used in the mixtures. 55
The most e?icient formulas will be those which
tling, thereby demonstrating the practicability
maintain suspension of _both ingredients over _
of avoiding agitation although solid insoluble in
such a length of time asto render agitation un
necessary, and which will, result in- a minimum“
gredients are used as found in nature without
comminution or pulverization.
In this manner
‘ a separating medium of relatively high speci?c
gravity may be obtained. Such separating me
dium would have maximum buoyancy and would
permit the adding of more water-to obtain the
m. desired speci?c gravity of'the mixture. There
fore the ?ner the solid materials the greater may
be the fluidity for a given speci?c gravity.
However, it was found from actual tests that
the ?ner the solid ingredients in theseparating
medium the greater would be the carry-off of
such ‘materials with the separated coal. and with
the impurities separated and removed. For in
stance, the minimum carry-oil‘ of solid ingredi
v carry-off - of _ the
solid
ingredients—clay
and
so
sand-from the ‘separating medium. The clay‘
and sand should be available as found in nature
without screening or comminution or pulveriza
tion, and therefore the process may be carried
out anywhere at a very low cost in materials and, 65
maintenance.
Such sand, of course, includes
silica sand. [Where solid materials are to be used
as sand,_by crushing ganister, quartz, etc., the
granules need be no smaller than those of ordi
nary silica
sand.
. ..
-
_
~.
70
The conclusions from the actual tests made
are as to the solid insoluble ingredients, that
Sandusky sand, a relatively fine sand,‘ is not as
ents from a separating medium composed of a silt "favorable as coarser sands unless the matter of i
and Sandusky sand (1 part silt plus‘ 4 parts
suspension becomes a icontrollingfactor and re
‘e
2,108,495
quires its use at lower speci?c gravities. In other
words, the colloidal clay acted upon by the elec
trolyte has the property of keeping in suspension
,
various parts of the country in accordance with
for a long period of time the ?ner sands. The
the nature of the natural clays and the natural
sands available. I will therefore set forth the
procedure that should be adopted to arrive at
tests also showed that silt gave more iavorable
the most e?lcient results for various kinds of
results than ?reclay. Silt in its natural state is
clays and sands.
composed of particles more ?nely divided than
the ?reclay. The ageing of the mixture for a
period of at least twenty~four hours enabled bet
The procedure is to mix the clay and water to
be used, the weight of the clay being about 25
percent of that of the water. This mixture is
ter results to be obtained. I The variation of the
placed in a series of beakers and to each beaker
speci?c gravity of the mixture can be controlled
by varying the proportion of the water. The
?uidity of each of the mixtures tested was su?i—'
cient to permit ireesettling of the impurities
15 during ?otation of the cleaned coal, since the
consistency or mobility of the mixture is not
such asv to interfere with the rapid operation of
the separating process.
>
It has been found from actual tests that sodium
20 silicate is preferable when the water is well water
or hard water, while sodium aluminate is prefer
able for the'hydrant water of the city of Colum
bus, Ohio, which water has been treated chem
ically to purify the same. However, either sodi
25 um silicate or sodium aluminate may be used as
the suspension agent in either hard water or soft
water.
'
Sodium silicate is usually obtainable in liquid
form, whereas sodium aluminate is in powdered
30 or desiccated form, the latter being more con
veniently handled than liquid sodium silicate.
Both sodium silicate and sodium aluminate can
be obtained at very low cost. For instance, in the
formula. using one part natural clay and four
parts natural sand with .8% of sodium aluminate,
the cost of the latter in certain localities is only
about 1/250th oi’ the cost of the clay and sand
‘combined. That is to say, in a separating medi
um having one part clay, four parts sand and .8
49 percent sodium aluminate, the cost of the sodium
aluminate required is only .4.- percent of the cost
of the clay and sand combined. This cost of the
electrolyte is sov low that no attempt need be
made in practice to reclaim any of it that clings
to the cleaned coal as it passes through the
washing tanks shown in the accompanying draw
,
g
is added a different amount. of electrolyte such
as sodium aluminate or sodium silicate.
After
the mixture in each beaker is stirred it is allowed
to stand for forty-eight hours and the one that
shows the best suspension of clay is the mixture
that should be selected. If the clay cannot be
maintained in suspension in any of the beakers
it is not a suitable form of clay.
When a suitable clay is found by following the
tests with the electrolyte, the mixture of clay
and electrolyte is introduced into a series of beak
ers, and sand in various proportions is added to
the various beakers. The combined weight of the
sand» and clay should be the same in each beaker.
One beaker may contain clay alone and the other
one part clay-and two parts sand, one part clay
and three parts sand, etc. Some clays such as
bentonite, have the property of carrying ten
parts of sand when the electrolyte sodium alumi
nate is used in a suitable separating medium in ‘
my method of cle'anlng coal, It should also be
understood that su?lcient water is added to the
various beakers to obtain the speci?c gravity re
quired for the desired coal separation.
After the mixtures in the beakers containing
the sand have stood for twenty-four hours, ob
servations are made and those beakers eliminated
which show settling of the sand at the bottoms of
the beakers.
'_
After selecting the most e?icient mixture’ by
proceeding with the tests outlined, the next test
to be made is to determine the amount of the
mixture that will be carried away with the coal
when removed from the separating tank to the
?rst washing tank. For this purpose a piece of
polished glass triangular in shape and having
ing's.
The formula for making up the mixture or'sep
sides each four inches long may be dipped into
aratlng medium used in our method of cleaning
glass before dipping and after, the weight of the I
mixture that adheres to the glass can be calcu
£30 coal di?'ers with the materials available to serve
as the insoluble solid ingredients. The clays
which are useful in my method, while having the
general characteristics of kaolinite are ‘not nec
essarily pure clays but would fall under the gen
in Q1 eral classification of shale, surfaces lay, silt and
?reclay. These types are widely distributed and
the mixture and withdrawn; by weighing the
lated. The mixture that carries ed the least
amount of separating medium is the most desir
able to he used in practice. For instance, in ac
tual tests it was found that for each one-tenth of
a grain per square inch carried off by the testing ;
glass, there will be seventeen (17) pounds of mix
ture carried off by a ton of separated coal.
v‘These tests were made by dipping the glass
and each is useful in the process in its natural
plate into the beaker mixtures andv weighing
60
The essential characteristics of the argillaceous while wet. The weights were calculated as the 60
material in the method of separating coal from weight of the mixture adhering to each square
its impurities, are those having the property oi’ inch of surface of the plate. Instead of using
glass plates imporous card-board squares may be
being dispersed or- de?ccculated bythe electro
lyte and after being dispersed or de?occulated, used for immersion in the beaker mixtures but
.65 having the property of maintaining in suspension I it will be found that less solid material will ad
the desired quantities‘ of sand or other inert here to the card-board than to the glass plate.
In such carry-off tests of beaker mixtures, a
granular material.
Such properties in my separating'medium used curve maybe plotted from the results obtained.
in my improved method of cleaning coal, may For instance, in connection with actual tests
70 be readily determined by simple tests which may made with a series of beaker mixtures in which
be carried out wherever clay and sand are found the amount of sodium silicate ranged from zero
in various parts of the country or wherever it is to 3.6 percent by weight of clay in the fluid, the
desired to iollow such method. I have set forth plotted curve will show a gradual decrease in
formulae for most emcient operation in certain the amount of clay carried out on a card until
localities but such formulae may be varied in the percentage of sodium silicate is about 1.3
readily available in various parts of this country,
state.
to
i
'
.7‘
2,108,495
or 1.4,.aiter which the increase of the percentage
of sodiuinsilicate vinoreasesthe amount of clay
carried out on a card. The clay used was a
form of' ?reclay having a pH value‘ of 5. Afterv
‘permitting the beaker mixtures to stand for
twenty-four hours after adding the electrolyte
' and stirring the mixture, it was found that the
suspension of the solid ingredients ‘in the sepa
rating medium andas to reduction to. the mini
mum of the solid ingredients carried oil from the
' separating medium.
It should be particularly noted by reference to
Figs. 4, 8, and 9 that the operation of separating
coal from the impurities may be carried on auto
clay remained in suspension the longest in the.
matically over an extended period of time, For
instance, if the tank 13 acts as a storage tank
10 clay in the'mixture, and the tests further showed while :the valve 16 is closed and the valve 15 10
that the range for best results would be between ' open, the automatic ?oat valve ‘I8 will maintain
1% and 1.4 %. of electrolyte. ' The carry-off tests the depth of the separating medium in the sepa
of clay mixtures also enabled the plotted curve rating tank I!’ at a predetermined level. At the
in Fig. 10 to show pounds of clay per ton of coal > same time the settling tank 60 may have clear
'. is that would be carried out of the medium during liquid therein so that when the valve 66 is closed 15
the coal separating process. For instance, in and the valve 61 is open the ?oat controlled
the tests just described where the best results switch ‘I! will e?eot intermittent automatic oper
would be obtained with the electrolyte ‘1.3% by ation oi’ the pump 64 to replenish water in the
beaker having 1% of sodium silicate by weight 01’
weight of clay in the mixture, the least amount of
tank ii’ for ?ow successively into the tanks i4,
20 clay would be carried out on the card and would
represent about 30 pounds of clay per ton of coal.
As above explained, there is a permissible range
and It. This is true whether the valve 54 is open
or not but will take place oftener if the valve 54
is partially open and the valve 62 is closed when
the valve 63 is open. There will then be a con—
" in the use of the proportions of the ingredients
in the water for maintenance of the clay and
"sand in suspension over relatively long periods
or time. In the beaker tests there may therefore
be various mixtures which would be suitable so
far as'maintenance of the clay and sand in sus
tinuous draining of settling material from the
bottom of the tank l3 to the settling tank 6!
while the automatically controlled and operated
motor M replenishes the water in the tanks 15',
II and i3. When sediment is removed from
pension is concerned, but by following the pol
either of the settling tanks 60 or 6| it may be
ished glass test the .best separating medium may ‘ delivered by means of the chutes H2, H3 directly
be obtained so that a minimum amount of the
separating medium will be carried away with the
separated coal by the conveyor,” and a minimum
amount will be carried away when the impurities
at the bottom of the separating tank are con
veyed out of the tank by the conveyor i8. It
. should be understood that during the operation
of the separating apparatus the intermixture of
the ingredients is so thorough that when the
40 cleaned coal and impurities are removed from the
separation tank, the medium that clings to the
removed materials is about the same in its pro
portions of constituents as the medium that re
mains in the tank. ‘The medium in the tank
45 therefore remains as to specific gravity and em
'
ciency, the same as when ?rst introduced and
the replenishment of the medium in the sepa
rating tank is by means of the same'mixture as
that selected by means of the foregoing tests.
Inasmuch as it is important to reduce to a
to"
minimum the amount of solid ingredients‘carried
to the mixing tanks 13, ‘ll, as shown in Fig. 7.
That is to say, when the system shown in~Fig. 4
is in operation, the valve 94 is keptopen contin
uously. The extent of opening of the valve 94
is regulated so that the water in the last tank i5’ "
is practically clear. If the water in the second
tank . I4 is practically clear, too much water is
being used in the automatic circulating system
which indicates ‘that the valve 9| should be par- '
tially closed. 0n the other hand if‘ the water in
the last tank I5’ is discolored, the valve 94. should
be 'moved toward open position. The valves 55
and 56 are kept closed during normal operation
and are opened for draining purposes only about
once in a shift of about eight hours and then 45
closed again.
,
‘It is also important to note that in the appa
ratus' used in my system and for my methods the >
liquids are substantially quiescent. This is par
ticularly true in the separating tank the bottom on
of which is entirely closed during operation‘ and
oil‘ from the separating medium and it is also , in which no special means is provided for agitat
important to maintain suspension of the solid ing the separating‘ medium.‘ The conveyors for
ingredients in the separatingmedium, the curve removing the separated coal and impurities are '
65 shown in Fig. 10 after.being plotted from the
operated at a relatively slow speed and may be 5.1
tests above: outlined, may be used to determine arranged either, as shown in-Fig, 1 or as shown in
the most practical percentage of sodium silicate . Fig. 3.
or sodium aluminate in the separating medium.
While I prefer to include the preliminary wet
For instance, since the best results from the ting of the raw coal for the reasons hereinbefore
60 tests indicate from .6% to .9% of sodium silicate explained this is not always necessary or desirable 60
by weight of clay and the curve shown in Fig. 10 .from the standpoint of economic operation.
indicates 1.3% of sodium silicate by weight of -The raw coal wet or dry, is fed into a quiet
clay, approximately one percent ofasodium sili
pool or separating bath in the separating tank
' cate by weight of clay' could be used in practice
to the extent, that the amount of solid ingre
dients that would be carried-out by the separated
coal and impurities from the separating medium
will'be approximately 32 lbs. per ton of raw coal
treated.
'
,
Inasmuch as the percentage of sodium silicate
or sodium aluminate for suspension purposes is
. critical as above explained, the region to the left
of the lowest point of the curve of Fig. 10 should
_ be relied on to determinelthe percentage of elec
trolyte for obtaining the desired results both as to
and .the , separated
coal
is. then
moved
up— >
wardly to a predetermined height from ‘which 65
it is dropped-by gravity into the ?rst washing
tank. ~This operation is entirely automatic and
the impact against the water'assists materially in
washing from the coal the solid ingredients car
ried over from the separating medium. However, 70
when the coal strikes the water the latter yields
to prevent breakage of the coal.
In some localities the sand and clay may be
obtained at such low cost that the reclaiming of
the same may not be‘ desirable in which event,
8
' 2,108,495
however, it may still be economical to retain the
water circulation for the washing tanks. That is,
the sedimentation steps may be carried out for
the purpose of obtaining clear water to replenish
that used- in the washing tanks and this may be
done automatically. In fact, all of the apparatus
shown in the drawings may be retained if desired,
although the sediment from the sedimentation
coal from said tank while leaving the separating
medium therein except for particles which ad
here to said coal, washing said coal to remove the
adhering separating medium therefrom, ‘and re
covering the removed separating medium to be
used again.
Obviously those skilled in the art may make
various changes in the details and arrangement
5. The method of cleaning coal which com
prises mixing a. separating medium comprising
sand, clay and a de?occulating or dispersion
of parts without departing from the spirit and
agent, storing and aging said medium, introducing
scope of the invention as de?ned by the claims
said separating medium into a separating tank,
introducing raw coal into said separating medium
while in a quiescent condition in said separating
tanks is discarded.
10
thereby separating the coal from the refuse, re
moving the refuse from said tank, removing the
, ,
.
hereto appended, and I therefore wish not to be
16 restricted to the precise construction herein dis
closed,
Having thus described and shown an embodi
ment of my invention, what I desire to secure'by
Letters Patent of the United States is:
1. In apparatus for separating coal from its im
purities,‘ and washing the separated coal. the
combination with a wetting tank, of a separating
tank, a washing tank, two sedimentation reclaim
ing tanks adapted to be used alternately, two mix
ing and storage tanks either adapted to be used
as a mixing tank while the other is being used as
a storage tank, means connected between the last
named tanks and said separating tank to main
tain the separating medium in the last-named
tank at a predetermined level, means a?ording
?ow of settled solids from the washing tank to
either of said sedimentation tanks, automatic
mechanism for pumping water from either sedi
mentation tank to said washing tank to maintain
the depth of water in the latter at a predeter
mined level, and conveyor mechanism associated
with the separating tank for removing impurities
and separated coal therefrom, and conveyor
mechanism for the washing tank to remove the
40 washed coal therefrom.
~
'
2. In apparatus for separating coal from its
impurities, the combination with a separating
tank, of a washing tank, a sedimentation tank.
conveyor mechanism for removing separately the
separated coal and impurities from the separat~
ing tank, conveyor mechanism for removing sep
arated coal from the washing tank, means for ef
fecting transfer of settled solids from the wash
tank thereby separating the coal from the refuse,
removing the refuse from said tank, removing
the coal from said tank while leaving the sep
arating medium therein except for particles which
adhere to said coal, washing said coal to remove
the adhering separating medium therefrom, and
recovering the removed separating medium to be
used again.
I
'
6. The method of cleaning coal which com
prises mixing a separating medium comprising
clay, sand and a relatively small amount of a
de?occulating or dispersion agent, storing and
aging said medium in a quiescent state, intro
ducing said aged separating medium into a sep
arating tank, introducing raw coal into said tank. 30
and separately removing the materials which
?oat and those which sink.
7. The method of cleaning coal which com
prises mixing a separating medium comprising
sand and a relatively small amount of a de?occu
lating or dispersion agent, storing and aging said
medium in a quiescent state, introducing said
aged separating medium into a separating tank,
introducing raw coal into said tank, and separate
ly removing the materials which ?oat and those
which sink.
_
8. The method of cleaning coal which com
prises mixing a separating medium comprising
clay and a relatively small amount of a defloccu- _
lating or dispersion agent, storing and aging said 43
medium in a quiescent state, introducing said
aged separating medium into a separating tank,
introducing raw coal into said tank, and sep
. ing tank to said sedimentation tank, and auto-v arately removing the materials which ?oat and
matic pump mechanism for pumping water from those which sink.
the sedimentation tank into said washing tank to
9. In a systernjol separating impurities from
maintain the depth in the latter at a predeter
raw coal, the combination with a separating
mined level.
tank, of means comprising a ?oat controlled valve
3. The method of cleaning coal which com
for maintaining the depth of separating medium
prises mixing a separating, medium comprising in said tank at a predetermined level, a washing
insoluble granular material and a de?occulating tank, a settling tank, means for controlling drain
or dispersion agent, storing and aging said me
ing of sediment from said washing tank to said
dium, introducing said separating medium into settling tank, means comprising a pump for draw
a separating tank, introducing raw coal into said. ing liquid from above the sediment in said set
no separating medium while in a quiescent condition
tling tank and. delivering said liquid to said
insaid separating tank thereby separating the washing tank, a motor for operating said pump,
coal from the refuse, removing the refuse from automatic means comprising a ?oat in said
said tank, removing the coal from said tank while washing tank for controlling said motor to op
leaving the separating medium therein except for eratesaid pump to maintain the depth of liquid
particles which adhere to said coal, washing said in said washing tank at a predetermined level, 65
coal to remove the adhering separating medium means for removing separated impurities from
therefrom, and recovering the removed separat
said separating tank, and means for moving
ing medium to be used again." '
cleaned coal from said separating tank into said
4. The method of cleaning coal which com
washing tank and then out of the latter.
TO prises mixing a separating medium comprising
10. In a system of separating impurities from
insoluble granular matériahclay, and a de?occn
raw coal, the combination with a wetting tank‘
lating or dispersion agent, storing and aging said adapted to contain water, of a separating tank
medium, introducing said separating medium into adapted to ‘contain aseparating medium, means
a separating tank, introducing raw coal into said for introducing raw coal into the water in the
separating medium while in said separating tank wetting tank and then deliver such wetted coal
‘ 2,108,495
£9
into the medium in said separating tank, a wash
ing tank adapted to contain water, means for
removing the separated impurities from said
a valve for controlling drainage of sediment from
said washing tank into said settling tank, and
separating 'tank, means for removing cleaned
1 liquid from above the sediment in said settling
coal from said separating tank and moving it
into and out of the water in-said washing tank,
a settling tank, means for eifecting drainage of
sediment from said wetting and washing tanks
into said settlement tank, and automatic means
10 for drawing water from above the sediment in
said settling tank and introducing such water
into said washing tank to maintain the depth of
automatic means for-controlling the drawing of
tank and introducing said liquid into said wash ca
ing tank to maintain the depth in the latter at
a predetermined level.’
12. In a system ‘of separating impurities from
raw coal, the combination with a separating tank
adapted to contain a separating medium, of a 10
plurality of washing tanks each adapted to con
tain water, over?ow means between each wash
water in the latter ‘at a predetermined level.
ing tank and the next adjacent washing tank,
11. In a system of separating impurities from
l 5 raw coai,‘_the combination with a separating tank
adapted vto contain a separating medium com
prising granular material held in suspension by
a dispersion agent, means for removing from said
tank the separated impurities, a settling tank,
20 means comprising a valve for controlling drain
age to said settling tank of impurities settled to
the bottom of said separating tank, a washing
tank adapted to contain water, means for re
moving cleaned coal from said separating tank
IO andmoving such cleaned coal into and out of the
mechanism for removing separated impurities
water in said washing tank, means comprising
from said separating tank, a settling tank, means 15
for controlling ?ow of sediment from said wash
ing tanks to said settling tank, means for remov
ing cleaned coal from said separating tank and
then moving such cleaned coal intoand out of
the water successively in said washing tanks, and 20
automatic means for drawing water-from above
the sediment in the settling tank and introducing
such water into one of said washing tanks to the
level of said over?ow means to e?ect auniiorm
predetermined depth in all of-the washing tanks. 25
Nils D. LEVIN.
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