Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR THE DRY QUENCHING OF COKE BY MEANS OF CARBON DIOXIDE
WITH SUBSEQUENT USE OF THE CARBON MONOXIDE PRODUCED
[0001]
The invention relates to a method for the dry quenching of coke by means of
car-
bon dioxide with subsequent use of the carbon monoxide produced, said method
involving
the cyclic coking of coal to coke with the coke being sent to a quenching
device after being
discharged from the coke oven and carbon dioxide being introduced into the
quenching de-
vice for dry quenching, thus creating carbon monoxide via a Boudouard reaction
and the car-
bon monoxide produced being used to heat the coke oven. This method allows the
heat gen-
erated during coking to be used for the production of carbon monoxide which,
in turn, can be
used in the heating process, thus on the whole achieving an extremely even
heat balance
throughout the entire process.
[0002]
Most methods for the production of coke take place in large coke oven
batteries
or coke oven banks that comprise conventional coke oven chambers or coke oven
chambers
of the "heat recovery" or "non-recovery" type. In conventional coke oven
chambers the coking
gas is collected and processed, while the coking gas in "heat recovery" or
"non-recovery"-
type coke oven banks is combusted in the coke oven in order to heat said oven.
Here, in
many embodiments the heating of the coke oven is carried out in several steps
in a gas
space above the coke cake and in a coke oven sole below the coke oven chamber.
[0003]
The coking process is performed cyclically, the cycles being charging,
coking,
discharging and quenching. After coking, the coke is pushed out of the coke
oven chamber at
a temperature of approximately 1100 C. It is pushed out into a quenching car
that collects the
coke cake and transports it to a quenching device. In many embodiments this is
a wet quench
tower, where the coke cake is sprayed with water which evaporates and cools
the coke cake
to a temperature below the kindling temperature of the coke so that it can be
transported in
the open air without posing a hazard. After quenching, the temperature of the
coke is uneven-
ly distributed in the coke cake but is usually less than 100 C.
[0004]
DE19614482C1 gives one embodiment of a wet quench tower. This teaching de-
scribes a plant for the wet quenching of hot coke in a method for the coking
of coal using a
coke sluice and a coke transfer chute that is located in a quench tower with a
water feed de-
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vice. On the other side, the chute fits onto a coke quenching car equipped at
the bottom end
with a coke discharge device and water discharge flaps. The water feed system
is located di-
rectly at the transfer chute and empties into the coke quenching car, which
can be sealed wa-
tertightly and is equipped with a control system which keeps the coke
discharge flaps closed
watertightly while the water is being fed in and opens the water discharge
flaps once the wa-
ter feed has been completed. When water is used for quenching, all of the
thermal energy
stored in the coke cake is lost without being used.
[0005] For this reason, increasing efforts have recently been made to
dry quench hot
coke using gases instead of water. Here, the gases are passed through the hot
coke and col-
lected or extracted until the coke has cooled to a temperature below its
kindling temperature.
The hot gas is usually passed through a heat recovery unit in which steam is
generated, thus
recovering the thermal energy. In turn, the steam can be used to drive
auxiliary units or to
generate electric power. For these purposes, inert gases, such as nitrogen or
blast furnace
gas, are often used.
[0006] W09109094B1 describes a method for the dry quenching of coke in a
quenching
chamber with the aid of circulating quenching gas, said method allowing the
velocity of the
gas coming from the coke to be adjusted so that the grain size of the
entrained coke dust par-
ticles is less than 3 mm and when the hot quenching gas enters the waste heat
boiler the
grain size of the entrained coke dust is less than 1 mm, said method involving
this gas being
passed through a device that consists of a quenching chamber and an
antechamber with a
round cross section of about equal size and a cylindrical outer casing made of
metal, and in
particular the roof of the quenching chamber being in an inclined position so
that it rises to the
hot gas channel, thus increasing the cross section of the annular gas channel
above the coke
pile enough to allow the gas velocity of the hot quenching gas to be adjusted
during quench-
ing so that it remains virtually uniform across the length.
[0007] W08602939A1 describes a method for dry coke quenching using
quenching gas,
said method involving the coke and the quenching gas being fed in
countercurrent direction
through a two-stage quencher, the first stage involving quenching to coke
temperatures of
approximately 800 C and the quenching gas fed through the second quenching
stage con-
taming steam, the quenching gas loop thus being directly coupled with a
thermal treatment
step in which steam is added so that there is essentially no char burnout,
which is achieved
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by the quenching in the first quenching stage taking place solely by indirect
heat exchange
between the coke and a coolant via heat exchanger walls and the quenching in
the second
stage being carried out solely by means of the steam-containing quenching gas.
[0008] State-of-the-art methods for dry coke quenching may include a
variety of embod-
iments. EP0317752A2 describes a method for improving the performance of coke
dry
quenchers which involves hot coke being broken up before entering the
quenching shaft.
DE3030969A1 describes a method for the dry quenching of hot raw coke that is
pushed out
of the chambers of a coke oven battery and discharged in a quenching chamber,
where it is
quenched by means of direct or indirect contact, or both, with a quenching
agent, and there-
fore the raw coke is preclassified into two or more size fractions before
entering the quench-
ing chamber and the individual size fractions are subjected to quenching in
separate quench-
ing chambers.
[0009] Further embodiments relate to the heat recovery or cleaning of
the quenching
gas. DE2435500A1 describes a method for preheating coking coal using
superheated waste
heat steam which is generated in a dry coke quencher by the coke releasing, at
its highest
temperature level, some of its heat to the walls of a steam jacket.
DE3217146A1 describes a
device for dedusting the loop gas of a coke dry quencher in which the gas
inlet channel and
the gas outlet channel are located at right angles to each other, the gas
outlet channel being
directly connected, via a conical expansion, with the inlet opening of the
waste heat recovery
boiler integrated into the gas loop and a dust collection chamber with an
inclined dust dis-
charge area being positioned on the opposite side to the gas inlet channel.
[0010] However, the said methods and their embodiments have the
disadvantage that
during quenching the heat of the coke either cannot be recovered or the heat
of the coke can
only be inefficiently recovered as during quenching a large gas volume is
generated and this
needs to be passed through a heat recovery unit, making quenching technically
difficult or
economically inefficient. For this reason, it would be advantageous to utilise
the heat that ex-
ists in the pushed coke via an endothermic chemical reaction that makes this
energy availa-
ble in chemical form.
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[0011]
One suitable endothermic chemical reaction is the Boudouard reaction. To con-
duct this reaction carbon dioxide (CO2) is passed through the hot coke, which
reacts with the
carbon dioxide to form carbon monoxide (CO). This reaction is endothermic and
reads:
C + CO2 2 CO; AH = + 172.45 kJ/mol
[0012] The
carbon monoxide is then contained in the gas heated by the quenching of the
coke and can be used to heat the coke oven. Quenching hot coke with carbon
dioxide using
the Boudouard equilibrium is described in GB245702A. Although the application
describes
the use of carbon monoxide as a fuel gas, it does not propose quenching the
coke in a
quenching device using carbon dioxide, subsequently collecting the carbon
monoxide and
then heating a coke oven chamber with the carbon monoxide.
[0013]
Therefore, the objective is to provide a method that cyclically carbonises
coal and
uses carbon dioxide (CO2) to dry quench hot coke after a coking cycle, with
the carbon diox-
ide thus reacting at least partially with the coke to form carbon monoxide
(CO) according to
the Boudouard equilibrium and the carbon monoxide obtained being collected and
used to
heat at least one coke oven.
[0014]
According to the invention, coke quenching using carbon dioxide takes place
in a
quenching device that is preferably designed as a quenching shaft. Following
coking of the
coal and completion of the coking process, the coke cake is taken to, or
tipped onto, a
quenching car, which transports the coke cake to the quenching device. Here,
the coke cake
is sealed off from the surrounding atmosphere and carbon dioxide is passed
through it. Pref-
erably, this is done in a vertically upward gas flow direction so that the
specifically heavier
carbon dioxide is displaced by the lighter carbon monoxide during the
quenching process.
The carbon dioxide may be a gas mixture in any state and even be in a mixture
with other
gases, but is preferably used cooled and dried in pure form.
[0015] What is claimed in particular is a method for the dry quenching of
coke, in which
= coal is heated in a coke oven via heating by means of a high calorific
gas and
coke is obtained via cyclic coking, said coke being pushed out into a coke
quenching car on completion of the coking, and
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=
= the incandescent coke is transported to a coke quenching device in a coke
quenching car in which said incandescent coke is quenched to a temperature
below the kindling temperature by means of a quenching gas, and
= carbon dioxide (CO2), which reacts at least partially with the
incandescent coke
5
to form carbon monoxide (CO) according to the Boudouard reaction, is used as
the quenching gas,
said method being characterised in that
= due to the dry quenching being carried out in a coke quenching device the
car-
bon monoxide-containing quenching gas obtained is collected, and
= the gas
mixture obtained is at least partially returned to the coke oven in order
to heat said oven with the carbon monoxide (CO).
[0016] The
carbon dioxide added for quenching purposes may be dried or undried. So as
to avoid the production of undesired by-products, the carbon dioxide added is
usually dried
and in pure form. For this, the carbon dioxide can be taken from any source
and in an exem-
plary embodiment comes from gas scrubbing processes. Said carbon dioxide can
be used
without being cleaned, but may also be cleaned prior to use. Other inert
gases, such as nitro-
gen, may also be added to the carbon dioxide.
[0017] For
addition, the carbon dioxide may be temporarily stored in a storage tank. The
carbon monoxide obtained during quenching of the coke may also be temporarily
stored. Part
streams of these two gases may also be diverted and used for purposes
unrelated to the
coke production plant. Meters for measuring the concentration of the gases may
be installed
in the carbon dioxide or the carbon monoxide lines. These readings may be
referred to in or-
der to decide on the use of these gases at various times. This may be done
manually or by
computer.
[0018] In a
further embodiment steam (H20) is added to the carbon dioxide as quenching
gas. The steam then reacts with the coke to form hydrogen (H2) and carbon
monoxide (CO),
from which synthesis gas is generated with the carbon monoxide which is formed
by the car-
bon dioxide reacting with the coke. The synthesis gas can be used solely for
heating or a part
stream can also be diverted and used for any further purpose.
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[0019]
The steam may be added to the carbon dioxide used for quenching at any
point. It
may, for example, be added to the carbon dioxide before said carbon dioxide is
used to
quench the coke. It may, however, also be fed to the quenching device or to
the shaft above
the feed point for the carbon dioxide separately from said carbon dioxide and
downstream in
the direction of flow. For this, the water may also be injected into the
carbon dioxide stream in
liquid form. It is also possible to add the steam to the coke cake via side
feed nozzles directly
downstream in the direction of flow when part of the coke has already reacted
with the carbon
dioxide.
[0020]
Steam can also be added to the carbon monoxide after quenching by the carbon
dioxide in order to carry out a separate carbon monoxide (CO) shift and thus
achieve conver-
sion into synthesis gas. The steam is then added after the carbon dioxide has
been passed
through the coke. For this, liquid water may also be added. In a typical
embodiment this is
then sprayed into the quenching gas after it has passed through the coke cake.
After the
Boudouard reaction has been carried out, the carbon monoxide is then cooled
and passed
though a conversion reactor to convert the carbon monoxide (CO) into carbon
dioxide (CO2)
and hydrogen (H2) via the water-gas shift reaction.
[0021]
An excess of steam may also be added prior to quenching and passage through
the coke cake so that a reaction for converting surplus steam and carbon
monoxide into hy-
drogen can subsequently be carried out. In this case, part of the steam (H20)
may already
react with the hot coke in a water-gas reaction to form carbon monoxide (CO)
and hydrogen
(H2). Liquid water can also be used instead of steam. This is sprayed into the
carbon monox-
ide stream before its passage through the coke. This procedure can also be
carried out in
combination with feeding steam to the quenching gas.
[0022]
When water is added to the quenching gas or during a subsequent conversion
re-
action, synthesis gas is obtained. It is possible to divert a part stream
thereof and use the
synthesis gas for any other purpose. In one embodiment of the invention it can
be used at
least partially to heat the coke oven.
[0023]
Before being fed to the coke oven the carbon monoxide used to heat the coke
ov-
en can be mixed with a fuel gas. In one embodiment this is hydrocarbonaceous
and so a hy-
drocarbonaceous fuel gas is mixed with the carbon monoxide. In one embodiment
of the in-
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vention, the fuel gas is natural gas. This is mixed with the carbon monoxide
before it is fed in-
to the coke oven and used to heat said oven. It is also possible for the
carbon monoxide for
heating the coke oven to be mixed with fuel gases that are generated as by-
products in other
processes and still have a certain calorific value. For example, it is
possible to add blast fur-
[0024] The carbon monoxide that is generated by the Boudouard reaction
and to which a
fuel gas has been added as required can be used directly for heating without
further treat-
[0025] This temperature is adequate for heat recovery and so in an
advantageous em-
bodiment the carbon monoxide is passed through a heat recovery unit before
being fed into
the coke oven for combustion. For example, it is possible to use this heat to
preheat, in coun-
tercurrent, the carbon dioxide gas stream that is fed in. It is also possible
to use the heat for
[0026] After quenching, the coke cake usually has a temperature of 500
to 900 C. To fi-
nally bring the coke down to a temperature below the kindling temperature
after quenching,
[0027] The carbon dioxide for quenching the coke can simply be directed
into the coke
cake in a stream. It may however also be split into any number of part
streams. In one em-
bodiment of the method according to the invention the carbon dioxide stream
that is fed in is
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coke quenching device from below and a further carbon dioxide part stream
being fed in in a
part of the shaft in which the coke to be quenched has a temperature of 500 to
900 C. The
carbon dioxide part stream can be fed in at any point in the quenching device,
but is prefera-
bly done at this point as utilisation of the heat is thus optimum. An
additional part stream of
carbon dioxide can also be fed in at any time in order to achieve complete
quenching of the
coke. The part streams can generally be fed into the coke at any point in the
hot coke cake.
[0028] For use in implementing the method, the coke oven battery or
coke oven bank
may be of any design and configured in any way. The coke oven battery from
which the coke
comes and which is heated by the carbon monoxide may, for example, be a coke
oven bat-
tery in which the coking gas is collected and processed. The coke oven bank
from which the
coke comes and which is heated by the carbon monoxide may, for example, be a
"heat-
recovery"-type coke oven battery. Finally, the coke oven bank from which the
coke comes
and which is heated by the carbon monoxide may also be a "non-recovery"-type
coke oven
battery. Even the coke ovens that are located in a coke oven battery or bank
may ultimately
be of any design as long as they are suitable for the production of coke and
for being heated
by carbon monoxide. The coke pushing may also be carried out at a different
coke oven bat-
tery or bank from that to which the carbon monoxide obtained during quenching
is fed, but
this is not usual practice.
[0029] In one embodiment of the invention the waste gas or completely
combusted cok-
ing gas from the coke oven is subjected to gas scrubbing. This allows the
carbon dioxide to
be scrubbed from the waste gas and the carbon dioxide obtained to be added to
the carbon
dioxide for quenching the coke. In this way an even carbon dioxide (002)
balance can be
achieved for the entire plant as the carbon dioxide from the waste gas is, in
turn, used to
quench the coke and, after being converted to carbon monoxide, to heat the
oven. As a re-
suit, the overall emission of carbon dioxide is low and ideally non-existent.
[0030] The quenching device for the coke may be of any design for
implementing the in-
vention. Preferably, for example, the coke quenching device may be a coke
quenching shaft.
But the coke quenching device may also be a coke quenching chamber. This may
be
equipped with auxiliary equipment to improve or optimise quenching. In one
embodiment of
the invention the coke quenching chamber is equipped with an antechamber in
which the gas
velocity is evened out. The quenching device or the subsequent transfer line
for the carbon
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monoxide may also be equipped with a dedusting device. This allows the dust to
be reduced
if a dust-laden coal is used or large amounts of dust are created during
quenching.
[0031] Furthermore, auxiliary equipment, such as storage tanks for
liquids or gases,
pumps, valves, heating or quenching equipment, or meters for measuring
temperatures or
[0032] The invention has the advantage of utilising the thermal energy
of the coke after
coking by means of an endothermic chemical reaction and so the thermal energy
of the hot
coke can be utilised much better than in prior-art methods. In addition, if
downstream gas
[0033] The invention is further explained by means of a drawing, this
drawing merely rep-
[0034] FIG.1 shows a coke oven which serves to carbonise coal. It
depicts the coke oven
chamber (1) with the coal cake (2), the coke oven chamber doors (3), the
primary heating
space (4) above the coke cake (2) and the secondary heating space (5) below
the coke cake
(2). The quenching car (6), which collects the coke cake (2) for quenching, is
parked in front
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tion, the fully combusted coking gas is exported out of the secondary heating
space (5) as
waste gas (12) and sent to a gas scrubbing device (13). Thereby, carbon
dioxide (13a) is ob-
tained. This is used to quench the coke (2) via a storage tank (14) for the
carbon dioxide (8).
The cleaned waste gas (13b) is exported from the gas scrubbing device (13) and
sent to a
5 heat recovery unit (15). Here, a generator (15a) that generates electric
power is driven via a
turbine. The cooled waste gas (15b) is exported via a flue (16). The quenched
coke (5a) is
discharged via a discharge flap (7b) and sent for final quenching.
[0035] List of reference numbers and designations
1 Coke oven chamber
2 Coal or coke cake
3 Coke oven chamber doors
4 Primary heating space
5 Secondary heating space
5a Quenched coke
6 Quenching car
7 Coke quenching chamber
7a Feed flap
7b Discharge flap for quenched coke
8 Carbon dioxide
9 Carbon monoxide
10 Dedusting unit
11 Heat exchanger
12 Waste gas
13 Gas scrubbing device
13a Carbon dioxide from the gas scrubbing
13b Cleaned waste gas
14 Storage tank
Heat recovery unit
15a Generator
15b Cooled waste gas
16 Flue
11)
=
