Note: Descriptions are shown in the official language in which they were submitted.
l The present invention relates to a method of heating
cold, wet coal, particularly coal for subsequent coking, as well
as to an arrangement for heating coke. In addition to the above
mentioned utility of the invention for heating coking coal, it is
also applicable to the heating of coal for other purposes, for
example for heating coal to be briquetted. 11ereinbelow the in-
vention will be illustrated as an example for a coking coal.
Coal for coking is generally available with surrounding
temperature 0-20C with a water content of up to 15~ and a grain
size distribution of l-lO mm, wherein approxirnately 85~ of the
grain size is less than 3 mm. For using it in coking ovens, cok-
ing properties of coal are very important, such as dilatation,
swelling degree, fluidity, etc. It is known that, by heating the
coal to 200-250C, the coking time of the coking oven can be con-
siderably reduced, for example from 20 hours to l~ hours, and by
heating the water is removed to an insignificant residual content
It is important that during heating the coking properties of the
coal not be affected. In contrast, it has been found that by
proper heating the coking of the coal in a coking oven can be im-
proved so that coals which are difficult to coke without treat-
ment can be used in coking ovens with success.
During heating particularly impact-type heating of in-
dividual coal particles, comminution of coal can take place,
which is undesirable, inasmuch as this increases the fine-grain
fraction in an unacceptable manner. The coal heating must there-
fore be performed very carefully. To prevent oxidation, the coal
heating 1~USt be continuously performed without access of oxygen.
Various process principles are known for implementation
of coal heating, some of which have been extensively used, such
as for example heating by hot gas flying stream, or by indirect
~'
L4~3
heating via heat exchange surfaces installed in the driers,
or by direct heating by hot gas in moYable shakers, for example
in a rotary drum. A11 these methods are characterized by high
investment costs, considerable machine expenses, and great energy
consumption. Moreover, displacement of the grain distribution to-
wards finer grain takes place during these processes. Also, other
coking properties, such as for example dilation and fluidity,
are undesirably affected. A device for heating coal which is
particularly advantageous in respect to energy consumption of the
coking oven is described in the Canadian patent application
402,417, in which the energy recovered during cooling of the
generated coke can be used for heating the coal. This device,
however, also possesses some disadvantages.
Accordingly, it is an object of the present invention
to provide a method of heating coal at low cost and which is
~nargy-economical, and with which coking properties of the coal
are guaranteed, and comminution of coal particles is avoided.
Another object of the present invention is to provide
an arrangement which attains the above mentioned advantageous re-
sults.
In keeping with these objects, and with others which
will become apparent hereinafter, one feature of the present in~
vention resides in a method of heating coal, in which hot solid
particles with an initial temperature exceeding a desired end
temperature of the coal are admixed with cold wet coal to heat
the latter.
In accordance with another feature of the present in-
vention, the solid particles have a continuously uniform shape
without edges, sharp corners, projections, and grooves. Par-
ticularly suitable are solid particles having a spherical shape.
-- 3 --
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1 Moreover, it is advan~tageous for good mixing of the coal with the
heat-conductive solid particles when the solid particles are pro-
vided in a narrow size range, for example formed as spheres with
a diameter smaller than 40 mm.
In accordance with other features of the present inven-
tion, the solid particles can be composed of metal materials, for
example steel or cast iron, or of non-metallic materials, for ex
ample ceramics or porcelain. The solid particles can also be com-
posed of mechanically strong and temperature-resistant synthetic
plastic materials.
The solid particles can be of natural origin, for ex-
ample pebblestone, which can be found advantageously in a prede-
termined shape and size. It is important for the selection of
the material of the solid particles that they be wear-resistant.
Thus, in the event of non-metallic materials, mechanical wear re-
sistance in accordance with DIN 52108 is advantageously smaller
then 0.45 cm3/cm2.
Heat properties of the solid partieles are of particular
importanee. It is reeommended to use solid particles with a heat
permeability (J/m2KsO 5) whieh is smaller than 16,000, preferably
smaller than 5,000. The thermal eonduetivity (m2/h) must be
smaller than 700 10 4, advantageously smaller than 150 10 4.
The speeifie heat of the solid particles (J/kgK) must be greater
than 400, advantageously greater than 800. In connection with
this it is expeeted, as desired, that the quantity of the heat-
transmitting solid partieles can be retained as small as possible
rela-tive to the coal quantity to be heated. It is thereby ad-
vantageous to select a material having maximum heat-accumulating
properties.
To prevent the situation wherein the cold wet coal is
~ ?~
1 subjected to heat impacts, the temperature of the heat-trans-
mitting solid particles is kept within certain limits. It has
been recognized that the temperature of the solid particles must
be selected so as to not exceed 500C, and the solid particles
must be composed of a material whose heat permeability and thermal
conductivity provide for fine transmission of the heat energy
accumulated in the solid particles to the coal.
Steam produced during evaporation of the coil moisture
shields the coal particles as protective gas against the undesir-
able influence of the air oxygen upon the coke-favorable proper-
ties of the coal.
~ eating of the solid particles can be performed in any
manner. When a coke dry cooling device is available in a coking
plant, it is advantageous to use heated cooling gas produced
thereErom. This cooling gas can be supplied in a container
accommodating the solid particles and gives out a part of its
heat to the latter, prior to flowing back to the coke dry cooliny
device.
Another possibility for heating the solid particles is
to provide a separate combustion chamber and to use exhaust gas
generated from a solid, liquid or gaseous fuel to heat the solid
particles in heat exchange therewith. The installation of such
a combustion chamber is advantageous when a coke dry cooling de-
vice is not recommended. This combustion chamber guarantees
heating of the coal in desirable quantities in the event of
failure or operational disruptions of the coke dry cooling de-
vice. Since the exhaust gases produced by combustion have an
excessively high temperature for heating the coal of approximately
1,400C their temperature can be lowered, for example by admixing
a water vapor in a required quantity.
1 - The novel features which are considered characteristic
for the invention are set forth in particular in the appended
claims. The invention itself, however, both as to its construc-
tion and its method of operation, together with additional objects
and advantages thereof, will be best understood from the following
description of specific embodiments when read in connection with
the accompanying drawing.
FIG. 1 is a view showing a principal sketch of a method
of heating coal in accordanee with the present invention;
FIG. 2 is a view schematically showing an arrangement
for heating coal in accordance with the present invention, in-
cluding a travelling layer drier formed as a vertically stand~ng
container;
FIG. 3 is a view sukstantially corresponding to the
view of FIG. 2, but showing the travelling layer drier with a
different discharging and separating deviee;
FIG. 4 is a view substantially corre~ponding to the
view of FIG. 2, but showing the travelling layer drier with a
built-in shaking screen;
FIG. 5 is a view showing an arrangement in accordance
with the present invention, formed as a multi-stage drier;
FIG. 6 is a view showing an arrange~ent in accordance
with the present invention, which includes a travelling layer
drier formed as a rotatable drum;
FIG. 7 is a view showing the inventive arrangement
with a travelling layer drier formed as an inclined container;
and
FIG. 8 is a view showing the inventive arrangement in-
cluding a travelling layer drier formed as an evaporating chute.
In accordance with FIG. 1, wet coal is supplied from
~.?~
1 a coal bi.n via a feeding device B and heated solid particles are
supplied from a solid particle heater C via a dosing device D,
with the aid of a suitable distributing device E together to a
device for heating the coal F. The coal and the solid particles
travel together in a direct stream through the device F. The
solid particles give out a part of the energy accumulated there-
in to the coal. The removed coal moisture is withdrawn via a
suitable steam space.
The thus heated coal is separated from the solid par-
ticles in a suitable separating device G, for example a shaking
sc:reen t and supplied in a suitable manner to a coke oven. The
solid particles are returned back, for example by a bucket con-
veyor H, to the solid particle heater C. The solid particle
heater C can operate with smoke or exhaust gases produced by com-
bustion. It is especially advantageous in the sense of energy
consumption of the coking oven when hot gas of a coke dry cooling
is utilized. The hot gas supply is identified by reference le-tter
I, and -the hot gas withdrawal is identified by reference letter
K.
In the embodiments shown hereinbelow for heating coal,
gases from a coke dry cooling are utilized for this purpose.
In the arrangement shown in FIG~ 2, the wet coal is
supplied from a supply bin 1 via a cellular wheel sluice 2 into
a travelling layer drier 3 which is formed here as a vertically
extending cylindrical contain~r. Sol~id particles, for example
having the shape of steel balls, are continuously supplied from
a heater 4 via the cellular wheel sluice 5 into the same travelling
layer drier. The coal and the admixed balls flow continuously
through the travelling layer drier from above downwardly, and the
coal and balls are maintained in constant movement by a stirring
~L~2Q~
1 m~echanism 6 with stirring arms 7. The drive of the stirring
mechanism is identified by reference numeral 8. The stirring
mechanism guarantees that new coal grains always come in contact
with the hot balls, so that the coal is subjected generally to
a substantially uniform thermal treatment. The resistance dur-
ing downward flow of the coal is overcome by its own weight and
the weight of the balls, and the variable dwell time of the coal
in the travelling layer drier is determined by withdrawal of the
coal and the balls in the lower region.
The discharge of the coal and balls from the travel.ling
layer drier 3 is carried out by a transporting screw 9 which
leads to a pneurnatic separating device 10. The coal, heated to
approximately 200C, is separated from the balls in the separat-
ing device 10 with the aid of a carrier gas supplied via a con-
duit 11, and is transported via a conduit 12 to a not shown coal
tower with a preceding separator. The speciically heavier balls
fall in an intercepting container 13 and are supplied with the
aid of a transporting device 14 (a chain conveyor, a bucket con-
veyor, etc.) to the heater 4. The discharge of the coal and
balls from the travelling layer drier can be facilitated by a
bin-emptying device 15 of suitable construction arranged in the
lower region of the travelling layer drier.
The waste-gas-containing steam separated in the
travelling layer drier 3 from the wet coal is withdrawn in dif-
ferent planes via conduits 16 and supplied via a cyclone lB, a
conduit 19 and a blower 20 into a circulating washer 21 in which
washing of impurities takes place in addition to condensation.
Instead of the above shown washer construction, other construc-
tions can also be utilized, such as for example a venturi washer.
The coal grains separated in the cyclone 18 travel via
-- 8
~?~Q~8
1 a cellular wheel sluice 22 and a conduit 23 to the separating de-
vice 10, from which they are supplied together with the heated
coal to the above mentioned coal tower~
The liquid flowing from the circulating washer 21 is
supplied via a conduit 24 and a pump 25 to a cooling tower 26 in
which further cooling to approximately 20C takes place. The
cooled liquid is supplied after this via conduit 27 into a cool-
ing water distributor 28. From here the required cooling water
is further supplied via conduits 29, 30 and 31 in different
planes to the circulating washer 21. The gas escaping from the
circulating washer is drawn via a conduit 32 and supplied to a
not shown fireplace.
The hot stream of the cooling gas exiting from the upper
part of a coke dry cooler 33 with a temperature of approximately
800C is withdrawn via a conduit 34. A conduit 35 branches from
the latter and is arranged so that a partial stream of the gas is
supplied via a heat exchanger 36 and then to the coke dry cooler
again. The remaining hot cooling gas travels via conduit 37 to
the heater 4 in which it is used for heat transmission to the
balls accommodated in the latter. This gas leaves the heater
via a conduit 38 and after passing a blower 39 with a tempera-
ture of approximately 220C is supplied in the conduit 35. From
this conduit one part of the gas is supplied via conduit 61 into
a central region, and another part is supplied via a conduit 32
in a lower region of the coke dry cooler. From a conduit 38
branches a conduit 40 through which a partial stream of the gas
can be blown via a fireplace 41 to the atmosphere. Moreover~ a
bypass conduit 42 is provided behind the blower 39 and communi-
cates with the conduit 37 to the heater 4. The hot gas flowing
from the coke dry cooler via the conduit 34 can be admixed via
1 *he kypass conduit for temperature regulation with cold gas from
the conduit 38.
In order to guarantee that, in the event of failure or
operational distortions of the coke dry cooler 33, the heating
of the balls in the heater 4 is not undesirably affected, a com-
bustion chamber 43 is additionally provided. The combustion
chamber 43 is supplied via conduit 44 with a gaseous, liquid or
solid fuel, and via a conduit 45 with a required combustion air.
Since hot gas generated during combustion has an excessively
high temperature of approximately 1 400C, water vapor is supplied
via a conduit 46 which branches from the conduit 19. By addition
of the water vapor, the combustion gas temperature is reduced to
the desired value of for example 800-900C. With this tempera-
ture, the combustion gas is supplied via a conduit 47 in the
conduit 37 which leads to the heater 4. A not shown regulating
valve is provided in the conduit 47, so that the withdrawn gas
quantity is throttled in some cases and the combustion chamber
43 can be used if necessary as an additional heating source.
The arrangement shown in FIG. 3 differs Erom the
arrangement shown in FIG. 2, in that the Separ~Rting device is
formed here as a shaking screen 48 located under the travelling
layer drier. The balls fall from it into the intercepting con-
tainer 13, whereas the coal travels via a conduit 49 to a bucket
conveyor 50 which transports the coal to a not shown coal tower.
The arrangement shown in FIG. 4 shows the vertically
standing travelling layer drier 3, in which, however, the sepa-
rating device is Eormed as a shaking screen 51 which is built in
the lower region of the travelling layer drier. The separated
balls are supplied into the intercepting container 13. The coal
is transported with the aid of a transporting screw 52 and the
-- 10 --
conduit 49 to the bucket conveyor 50. For providing disaggrega-
tion of the coal and avoiding nesting of balls in the center of
the travelling layer drier, the heat transmitting solid particles
are formed as steel balls, and additional electromagnets 53 are
provided outside of the travelling layer drier in offset relation-
ship relative to one another. The electromagnets 53 are period-
ically activated so that the steel balls are maintained in dis-
bributed condition in the drier. The dwell time of the coal in
the travelling layer drier is determined in this embodiment by
the transporting screw 52, on the one hand, and by the position
of throttliny flaps 54 in the interior of the travelling bed
drier.
The arrangement shown in FIG. 5 has the travelling lay-
er drier 3 which is formed as a multi-stage or multi-storv drier.
The supplied coal and the balls are mixed by the stirring mecha-
nism 6 with the stirring arms 7 and travel via openings in story
bottoms 55 from one story to the other.
The arrangement shown in FIG. 6 has the travelling layer
drier 3 which is formed as an inclined rotary drum. The coal
and balls are supplied to the drum via a transporting screw 56
and mixed in the former. The discharge is also performed via a
transporting screw 57 which supplies the material to the pneumat-
ic separating device 10. The withdrawal of the steam from the
drum is performed via a conduit 58 which, as can be seen from the
drawings, extends into t~a interior of the drum. A plurality of
driving elements to act on solid particles can be arranged within the
rotary drum 3.
The arrangement shown in FIG. 7 has the travelling
layer drier which is formed as an inclined container. The supply
and discharge of the material is carried out here similarly to
the arrangement of FIG. 6 by the transporting screw 56 and 57.
The steel balls are alternately displaced by electromagnets 60
which are provided at the upper and lower sides of the container
and offset relative to one another. Thereby the steel balls move
, . 11
1 along a sinusoidal path from the inlet to the outlet of the con-
tainer. This prevents segregation of the material and provides
for disaggregation of coal.
FIG. 8, finally, shows the arrangement in which the
travelling layer drier 3 is formed as an inclined vibrating chute.
For preventing settling of the steel balls because of their great-
er specific weight on the bottom of the chute, the electromagnets
60 provided at the upper side of the vibration chute are periodi-
cally actuated and thereby provide for a continuous sinusoidal
path of the steel balls.
When the method is performed and the arrangement is de-
signed in accordance with the present invention, -the following,
highly advantageous results are obtained. The invention provides
for a great speciic heat exchange surface, which depending upon
the radius of balls is equal to 200-600 m2/m3. There is a high
heat exchange coefficient which amounts to 80-400 W/m2K. There
are relatively small drying volumes, such as 4-16 m3 relative to
100 t/h o the dry coal. A great power density is obtained,
equal to 1,050-3,200 3 . A low consumption of electrical energy
is required, namely 20-60 kW for the transportation of the solid
particles with a total consumption of approximately 600 kW, re-
lative to 100 t/h of coal. It requires a little staff for opera-
tion and maintenance of the device, and low maintenance costs.
It c~uses insignificant environmental problems. There is no
danger of undesirably affecting the coking properties of the coal,
since the input temperature of the solid particles is equal at
maximum to approximately ~00C.
Two examples are presented hereinbelow in a table,
wherein they are based on a coal quantity to be heated of 100 t/h
and steel balls of steel 35.8 in one example, and silica brick
balls, in the other example.
- 12 -
1 Solid Particles
steel silica
Material coal balls brick
dosing quantity (t/h) 100 320 247
input temperature (C) 20 400 400
output temperature (C) 200 220 238
moisture of entering coal (%) 9 - -
moisture of exiting coal (%) 0
diameter of apparatus ~m) - 1.5 1.5
10 length of apparatus (m) - 2.1 6.5
length of entire moisture
separation (m) - 1.4 4.3
diameter of balls (mm) - 15 15
dwell ti.me of coal (S) - 100 139
travelling speed of coal (m/min) - 1.9 3
volume ratio (m3 coal/m3balls) - 2.8 1.2
mass ratio (t eoal/t balls) - 0.28 0.42
theoretieally required eireu-
lating conductivity of balls (kW) - 15 10
speeiic surEaee of balls (m2/m3) - 300 300
20thermal eonduetivity (W/mK) 0.27 45 0.37
speeifie thermal capaeity
(J/kg K) 1423 683 1013
- 13 -
1 It will be understood that each of the elements describ-
ed above, or two or more together, may also find a useful applica-
tion in other types of constructions dif~ering from the types
described above.
While the invention has been illustrated and described
as embodied in a method of and an arrangement for heating cold,
wet coal, it is notintended to be limited to the details shown,
since various modifications and structural changes may be made
without departing in any way from the spirit of the present inven-
].0 tion.
- 14 -
