Note: Descriptions are shown in the official language in which they were submitted.
~2~ssgs
The invention relates to a method for utilizing the
sensible heat which is formed during the dry cooling of coke
by means of a gas, in which, for preheating the coal used in
producing the coke, a circulating gas is passed through a
waste heat boiler or the like heat consumption device and,
after being freed from dust, is then returned to the coke
cooling chamber, any excess gas being removed from the circuit.
In the case of known installations for cooling coke,
operating in conjunction with a steam producing device, the
cooling gas, after cooling in the steam boiler, is returned to
- the cooling chamber at a temperature of about 150C. In order
to cool the coke down to about 200C, a correspondingly large
volume of cooling gas and a correspondingly large cooling
chamber are needed. Since the latter is lined with refractory
material, a considerable investment is required.
It is also known to preheat the coal used to produce
the coke in the coke oven by means of flue gas or blast furnace
gas as a carrier gas which has withdrawn the sensible heat from
the coke in a coke dry cooling unit. The use of a blast
furnace gas as a carrier gas is known from German Patent
27 33 365. According to this method, which is mainly suitable
for steel plant coke ovens where blast furnace gas is available,
the cooled gas is returned to the circuit after the coal has
been heated.
In all circulating processes, the volume of circu-
lating gas is increased by gasification (coke burn up) and
subsequent coke degasification, and a certain amount of
circulating gas must therefore be removed continuously~ In
the method disclosed in British Patent 1,334,373, a flue gas
is used as the carrier gas. Because of the residual oxygen
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content in all flue gases, the increase in gas and the loss of
coke by burn up is greater than with combustible gases, and
the volume of circulating gas to be carried away is also
greater. This gas enriched with pollutants is released to the
atmosphere, and thus requires expensive conditioning equipment,
such as after burners, dust removers and possibly desul-
phurizing e~uipment.
It is the aim of the present invention to provide
conditions for the low cost implementation of a method for
the dry cooling of coke in which the carrier gas flows in a
closed circuit between the step of dry cooling of coke and
that of preheating coke, any excess of circulating gas being
discarded without causing pollution.
According to the invention, this aim is achieved by
cooling down the circulating gas leaving the waste gas steam
~oiler, before said gas enters the coke cooling chamber, in a
combined washer cooler, approximately to the cooling tempera-
ture thus removing the dust from said circulating gas.
This rnakes it possible to reduce considerably the
size of the coke cooling chamber. The circulating gas is not
freed from dust as usual, by means of a dry separator, but
with a co~bined wet washer cooler, where the said circulating
gas is not only cleaned, but is cooled down to a temperature
close to that of the coolant used. Since the circulating gas
which is returned to the coke cooling chamber has, according
to the invention, a substantially lower temperature, for
example below 20C., the volume of circulating gas can be
reduced considerably, and the coke cooling chamber itself may
also be considerably smaller. Because of the smaller volume
of circulating gas, a smaller blower using less power may be
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used. The arrangement according to the invention therefore
results in a considerable reduction of the investment and
of the operating costs.
Moreover, by using an additional cooling unit, or a
heat pump like unit, it is possible to provide additional
cooling for the circulating gas leaving the washer cooler,
before said gas enters the coke cooling chamber. This again
reduces the volume of circulating gas and, at the same time,
allows part of the water vapour to be removed from the circu-
lating gas by condensation~ The resulting nearly dry gasbehaves like the circulating gas which is used in a normal
dry coke cooling process and eliminates additional coke burn
onO This allows the method according to the invention to be
still more economical.
In accordance with a preferred ernbodiment of the
invention, the clrculating gas between the coke dry cooler
and the coal preheater is a combustible gas. The calorific
value of the cornbustible gas is adjusted by feeding nitrogen
or clean flue gas into the cold circulating gas ahead of
the coke dry cooler, and/or by feeding air into the hot
circulating gas after the coke dry cooler. Any excess cold
circulating gas is withdrawn from the circuit ahead of the
coke dry cooler and is mixed with the under-grate-firing
gas to be fed to the coke ovens.
In accordance with another ernbodiment of the
invention, the excess hot circulating gas, i.e. part of
the circulating gas not needed to preheat the coal, is
withdrawn between the coke cooling chamber and the preheating
unit, after which it is passed through a waste heat boiler,
and is mixed with the gas leaving the said preheating unit.
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~ccording to a preferred embodiment of the
invention, part of the cooled down gas emerging from the
preheating unit is withdrawn so as to adjust the operating
temperature and is fed into the duct running from the coke
cooling chamber to the said preheating unit~
The method according to the invention is particularly
suitable for colliery coking plants and produces extremely
little pollution, since the excess ~as can be mixed with the
under-grate-firing gas for the coke-ovens, thus eliminating
the conditioning of the equipment.
The invention will now be illustrated by means of
the annexed drawings, in which:
FIGURE 1 is a diagram illustrating the method of
cooling coke according to the invention, and
FIGURE 2 is a diagram which illustrates another
embodiment of the method according to the invention.
With reference to Figure 1 of the drawings, it will
be seen that the hot circulating gas leaves the coke cooling
chamber 101 at 103 and is sent to the waste heat steam boiler
105 via duct 107. The circulating gas leaves the waste heat
steam boiler 105 at 109 and is thereafter sent to the combined
washer cooler 111 by circulating through duct 113, which is
at a temperature between 180 and 200C. It will be noted
that a coolant, for example water, is introduced into the
combined washer cooler 111 by means of a duct 115 from which
it is sprayed into the combined washer cooler 111 by means of
the spraying device 117. The hot circulating gas is passed
through the combined washer cooler 111 via duct 119 and it
leaves at 121.
This, in effect, removes the dust from the
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circulating gas and cools it to approximately the temperature
of the coolant, for example about 20C. The thus cooled
circulating gas is sent via duct 123, to a cooling unit 125
which operates in the same manner as, for example, a heat
pump, where it is cooled down still further. The circulating
gas, thus cooled down to this extent, is returned to the coke
cooling chamber via duct 127, after which it is picked up by
a blower 129 from which it is sent to the coke cooling chamber
. 101, via duct 131.
Figure 2 illustrates another embodiment of the
method according to the invention. According to this
embodiment, there is provided a coke oven 1 inside of which
there is a chamber 2 which is filled with preheated coal,
the latter being introduced from above, through a system of
ducts 3, by means of filling holes, not shown which can be
closed off.
Fuel gas and combustion air are fed through ducts
5 and 6 and pass, through regenerators 4, into the flues (not
shown) surrounding the oven chamber. The gases which are
formed during the dry distillation are removed through riser
pipes, not shown, from which they are sent into a receiver
(also not shown).
The hot coke which is forced out of the coke oven
at about 1000C, is removed in batches, by means of a bucket,
through a pressure tight lock, after which it is sent to dry
cooling unit 7 where the coke is dry cooled and releases its
sensible heat to the circulating gas. The coke, cooled down
to a temperature of ~ 200C, leaves the dry cooler through
duct 12. The circulating gas enters dry cooler 7 via duct 8
and leaves it through duct 9, through which the hot gas
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reaches unit 10 which is used for preheating the coal. The
coking coal is introduced into the preheating unit via duct
11 and is filled into the coke oven chamber 2 via duct 3.
The circulatlng gas leaving the preheating unit 10,
after having been freed as much as possible from dust carried
along, for example in an electrostatic dust filter 13, is
cooled in a gas cooler 14 to the desired final temperature
of between 30 and 40C, for example, and is returned, through
a pressure booster blower 15 and duct 8 to dry cooler 7.
The adjustment of the operating temperature of the
preheating unit 10 is carried out in the following manner. A
specific volume of cooled gas is removed from ductl~, whichruns
to filter 13 -through duct 17. This volume is fed into duct 9
by means of pressure booster blower 18. The portion of the
gas leaving the dry cooler 7, and which is not required for
heating the coking coal, is removed from duct 9 for producing
steam in waste gas boiler 19, after which it is sent to duct
16 which runs to filter 13.
According to the invention, the heat carrier is a
combustible gas flowing in a closed circuit. The circulating
gas may be produced, when the installation is started up, by
feeding air into dry cooler 7 through duct 21, shown in
dotted line in the drawing of Figure 2. This air is used
only for starting the operation and is deviated from air
duct 20. The air reacts with the hot coke and burns or
gasifies a small portion thereof. During this operation, the
circulating gas is enriched with the products resulting from
the burning up, gasification and after-degasification of coke.
The excess gas is removed from the circuit between pressure
booster blower 15 and dry cooler 7, via duct 22 and is fed to
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hot gas duct 6, i.e. it i5 mixed with the under-grate-firing
gas fed to the coke ovens.
In order to keep constant the desired calorific
value of the circulating gas, the value of which is preferably
between 2900 and 6300 kJ/m3N, it is possible to mix nitrogen,
cleaned flue gas and/or air selectively with the circulating
gas. The addition of air, which is substantially less costly,
also causes a reduction in the hydrogen content and a slight
increase in heat potential. Air is added through duct 20
into duct 9, where it is fed into the hot gas behind the
dry cooler. Flue gas or nitrogen is added to the cold
circulating gas, through duct 23, between blower 15 and dry
cooler 7. The operating pressure in the coke dry cooler is at
a level of about 1~00 mm water, so that the circulating gas
may pass, without any increase in pressure, through subsequent
stages of the method, thereby avoidiny negative pressure at
any point in the system.
