Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD FOR GENERATING A NEGATIVE PRESSURE IN A COKE OVEN
CHAMBER DURING THE PROCESS OF COKE PUSHING AND COAL CHARGING
The invention relates to a method for generating a negative pressure in a coke
oven chamber during the process of coke pushing and coal charging by way of
which
noxious flue gases evolving particularly during the charging and pushing
procedure of a
coke oven chamber are sucked from a coke oven chamber to prevent these gases
from
escaping into the environment. The invention also relates to a device for
generating a
negative pressure in a coke oven chamber.
Coke is frequently produced in coke oven chambers which are charged
horizontally, wherein coal charging is followed by the coking process which
produces a
usable coke from coal. In this type of construction, a coal-free space is
provided above
the coke cake in order to ensure a trouble-free gas evolution of coking gases.
Coke oven
gas escaping from coal when heated-up is collected in this coal-free space and
incinerated by admission of air. To ensure a uniform heating of the coke cake
from all
sides, the partially burned coking gas is conducted in special channels
located in the side
walls of the coke oven chambers and passed into secondary heating spaces
arranged
beneath the actual coke oven chamber. There, it is completely incinerated by
admission
of a further volume of air. Thereby, the coke cake is also heated from below
and thus
from all sides. Coke ovens of this type are called "Heat Recovery" or "Non-
Recovery"
coke ovens, depending on the use of the heat of combustion. Typical types of
construction are disclosed in US 4344820 A or US 4287024 A.
As a rule, the operation of coke oven chambers is run in cycles. After a
certain
period of time, the carbonization of coal is complete and the coke is removed
from the
coke oven chamber. This is accomplished in a cycle of coke pushing,
transferring the
coke into a vehicle for further transportation or into a cooling device.
Subsequently, the
coke oven chamber is again charged with fresh coal. Since a coke oven chamber
in
general provides capacity for just a limited amount of coal, several coke oven
chambers
are united to form a coke oven bank. As a result, coke production can be
continuous.
During the procedure of coke pushing and coal charging, the coke oven chamber
doors must be opened. For example, if the oven doors are opened too early, non-
burned
flue gases leak through the open doors or primary air apertures into the
environment.
When the ovens have been emptied, they are charged again with non-preheated
coal.
As coal is charged into the oven, an intensive evolution and incineration of
crude gases
occurs spontaneously due to the high oven space temperature ranging between
1100 C
and 1400 C. This is the reason for the large volume of flue gases evolving at
the
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beginning of the cokemaking process. In conventional types of construction,
these flue
gases can leak unrestrictedly into the atmosphere, because the negative
pressure in the
combustion chamber existing with closed doors could otherwise not be
maintained as the
doors are open during coal charging. The flue gas quantities escaping during
the coal
charging procedure, too, constitute a burden on the environment and endanger
the
operating staff. For this reason, numerous tests and experiments have been
made in
prior art with the aim to avoid this non-desired escape of flue gases.
US 3844901 A describes a device for the suction of dust-laden hot gases, said
device comprised of a tapered roof supported by supporting pillars, the tip of
the roof
being located above the source of emissions, and a thermal expansion zone
being
formed by the upper zone of the roof, and there being a suction channel
located in the
upper zone of the roof and extending the whole length of the roof, and the
cross-section
of which widening towards the suction source, and the suction channel being
provided
with air scoops to ensure constant negative suction pressure over the entire
length of the
suction channel. The design is claimed for all methods and chemical processes,
but in
particular it is suitable for horizontal coke oven chambers, the roof being
located above
the coke oven chamber door so that the flue gases are emitted into the roof,
with the
opening of the suction channel being arranged in the tip of said roof. The
roof extends
along the whole front of the coke oven chamber. The structure is stationary
and it
demands substantial space in front of the coke oven chamber doors, said space
not
being available for coke oven charging machines, for example.
GB 365934 A describes coke oven chambers comprised of an oven free space
above the coke cake, with the coke cake being provided with channels through
apertures
in the coke oven chamber ceiling to withdraw the gases evolving during coal
carbonization, sucking theses gases through a connecting pipe into a gas
collecting pipe
which is linked to all coke oven chambers, and wherein devices for controlling
the
pressure are arranged between the connecting pipe and the gas collecting pipe.
In one
embodiment of the invention, the pressure in the oven free space above the
coke cake is
adapted to the relevant stage of the coal carbonization process by way of
adjusting the
suction pressure.
A suction of flue gases during coke pushing and coal charging is not
described.
Moreover, the implementation of channels into the coke cake prior to the
process of coal
carbonization is costly. It would therefore be advantageous to take-up the
flue gas
evolving during coke pushing and coal charging by way of a negative pressure
which is
established during this procedure in the oven free space above the coke cake.
Generating a negative pressure in the primary and secondary heating space has
already
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been disclosed in prior art. For flue gas suction, the negative pressure must
be regulated
because the negative pressure is increased for this purpose only for a certain
period of
time.
GB 447036 discloses a method for distillation and carbonization of coal heated
in
cokemaking retorts, with these cokemaking retorts being arranged in rows to
form coke
oven banks, and with the coal being progressively heated-up so as to dry and
distill it until
it has attained a temperature of 6000C whereby it is cooled. The retorts can
be provided
with vertical heat transport ducts which can also be utilized for suction of
coking gases by
way of a negative pressure, said heat transport ducts being connected to the
flue gas
channels under the cokemaking retort in one embodiment of the process. In this
manner,
a negative pressure can be aspirated into the oven free space of the
cokemaking retort
via the flue gas channels. A coal carbonization with a controlled exploitation
of coking
gases can be achieved thereby. A process step for special aspiration of flue
gases
during coke pushing and coal charging is not disclosed.
The regulation of a negative pressure in a coke oven chamber has also been
disclosed in prior art. EP 1230321 B1 describes a method for discharge of hot
crude
gases evolving on coal carbonization in oven chambers of a coke oven battery,
with the
crude gases being withdrawn from the oven chambers at a temperature of 600 to
10000C
and introduced without decreasing the crude gas temperature into a hot gas
collecting
main, and wherein the pressure in the oven chambers is measured and regulated
independently of the pressure level of the hot gas collecting main by way of
shutoff and
throttling apparatus arranged in the hot gas streams between the crude gas
outlet from
the oven chambers and the hot gas collecting main, and the position of which
is
controlled as a function of the pressure measured in the allocated oven
chamber, and
wherein the gas from the hot gas collecting main is passed on to a steam
boiler control or
a split reactor. By way of the inventive process, the hot crude gases evolving
on coal
carbonization can be supplied without any further treatment and without
decreasing the
crude gas temperature to a complete incineration or cracking unit, without
this influencing
the cokemaking process in the oven chambers. The hot gas collecting main is
kept at a
slightly negative pressure to generate a vacuum. The process does not disclose
a
process step for quick aspiration of flue gases during coke pushing and coal
charging.
The processes or devices mentioned hereinabove bear a disadvantage in that a
special process step for the suction of gases is not provided for. However,
this process
step must be provided especially for this purpose, because substantial
quantities of flue
gas burdened with contaminants escape into the atmosphere only at the moment
of coke
pushing and coal charging as the coke oven chamber doors are opened.
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Now, therefore, it is the task to provide a method for aspirating the flue gas
evolving on coke pushing and coal charging back into the coke oven chamber by
generating and regulating a negative pressure in the oven within the coke oven
chamber
which is increased as compared with normal operation. The term of an elevated
negative
pressure shall be understood to mean a pressure that is further reduced as
compared
with the atmospheric pressure. Suction must be so effected that a relatively
high
negative pressure is available within a short time interval so that the
suction is complete
and free of emissions.
It would also be of advantage to have no need for structures on the coke oven
chamber ceiling, because the space on the coke oven chamber ceiling is often
utilized for
devices serving the purpose of ventilation. Structures for charging, cleaning
or process
controlling, too, may be provided on coke oven chamber ceiling if the space
existing there
is not required for the suction device.
The invention solves this task by way of an aspiration system for negative
pressure which effects the aspiration through the secondary heating space via
channels
through the side walls, so that an elevated negative pressure is generated in
the oven for
the period of opening the coke oven chamber doors and of pushing and charging
the
coke or coal cake in the oven free space above the coke cake which is also
called
primary heating space.
For example, this can be accomplished by means of a special aspiration device
which is connected to the channels on the suction side. The pressure in the
primary
heating space is thus lowered when the coke oven chamber doors are opened, so
that
the flue gases evolving during coke pushing after opening the doors are sucked
into the
interior of the primary heating space instead of escaping into the atmosphere.
By way of
this method and the device associated therewith, space is not required,
neither on the
coke oven chamber ceiling nor in front of the coke oven chamber doors.
Claim is particularly laid to a method for generating a negative pressure in a
coke
oven chamber during the process of coke pushing and coal charging, wherein
= the coke oven chamber is filled with a layer of coal for coal carbonization,
whereby flue gases are generated, and wherein
= after coal charging, the coal is heated-up for coal carbonization, and
wherein
= these volatile coal constituents are partially oxidized by means of sub-
stoichiometrically supplied air directly above the coal charge in an oven free
space
intended to serve this purpose, and wherein a combustion system for combustion
of non-
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burned volatile coal constituents as well as gases generated during partial
oxidation is
arranged beneath the coke oven chamber, and wherein
= the coke oven chamber in its side walls contains channels and wherein
these channels connect the upper coke-free section of the coke oven chamber on
the gas
side with the combustion system beneath the coke oven chamber,
and which is characterized in that
= a negative pressure is generated through these channels in the oven free
space above the coal cake, said negative pressure serving the purpose of
aspirating the
flue gases from the oven free space which evolve during the temporary coal
charging or
coke pushing procedure.
For an advantageous execution of the present invention, the aspiration
procedure
is started 5 minutes prior to opening the coke oven chamber doors and finished
30
minutes upon closing the coke oven chamber doors. An optimal suction of flue
gases
from the coke oven chamber is thus ensured. In an exemplary embodiment of the
present
invention, the aspiration procedure is continued for up to 4 hours after the
doors have
been closed. The flue gases may contain soot.
In a simple type of construction, it is conceivable to establish the negative
pressure directly at the channels in the side walls so that the channels are
connected to
the suction side of an aspirating device, thus creating a negative pressure in
the primary
heating space, with the coke oven chamber being arranged at the end side in
the
direction of suction. In an advantageous manner, however, the negative
pressure is
lowered in the secondary heating space located beneath the coke oven chamber
so that
this negative pressure is aspirated via the channels in the side walls, the so-
called
"downcomer" channels, into the primary heating space, with the coke oven
chamber
being arranged at the end side in the direction of suction.
Typical negative pressures required for a complete suction of flue gases range
between minus 20 and minus 50 Pa in the primary heating space near the coke
oven
chamber doors. To achieve this negative pressure, the discharge of waste gas
from the
secondary heating space and the supply of air into the primary heating space
can be
temporarily shut-off. In some embodiments of the inventive process, negative
pressures
of up to minus 120 Pa can also be achieved. The inventively sucked-off flue
gas can be
further used for any arbitrary purpose.
For example, in another embodiment, it is favorable to employ a vacuum
receiver
tank which on opening the doors of the coke oven chamber is linked via a valve
to be
opened to the secondary heating space so that a negative pressure is thereby
generated
CA 02778789 2012-04-24
within a short period of time in the oven free space above the coke cake, with
the coke
oven chamber being arranged at the end side in the direction of suction. In
this manner,
the negative pressure in the oven free space above the coke cake is aspirated
via the
channels from the secondary heating space.
In this case, the vacuum receiver tank will be at an elevated negative
pressure
and shortly connected with the secondary heating space as the coke oven
chamber door
is opened. Thereby, the negative pressure in the primary heating space is
sufficient to
reliably prevent an escape of gases from the coke oven chamber. The negative
pressure
in the combustion system beneath the coke oven chamber is thus generated by a
vacuum receiver tank which is linked to the secondary heating space via a
lockable
secondary channel which is shortly connected to the secondary heating space
for the
process of suction so that a negative pressure in the oven free space above
the coke
cake is aspirated via the channels. After the suction process, the vacuum
receiver tank
can be separated by way of appropriate devices from the secondary heating
space and
be evacuated again.
In a further embodiment of the invention, the negative pressure in the
combustion
system is generated by a negative pressure-containing vacuum line arranged
outside the
coke oven chamber, the negative pressure being aspirated via a branch line in
the oven
free space above the coke cake via the channels. This vacuum line can be
arranged at
any place in the vicinity of the coke oven chamber or the coke oven bank. For
example,
an arrangement beneath the coke oven chamber doors is possible. But an
arrangement
on the coke oven chamber ceiling is also possible.
It is also feasible to generate the negative pressure in the combustion system
beneath the coke oven chamber by way of a blower which aspirates the negative
pressure in the combustion system beneath the coke oven chamber via separate
channels. The negative pressure can then be controlled by a device regulating
the
blower performance. A receiver tank is not necessarily required for this
purpose.
Claim is also laid to a device for generating a negative pressure in a coke
oven
chamber during the process of coke pushing and coal charging, said device
comprised of
= a coke oven chamber that can be charged with a coke cake destined for
carbonization, there being an oven free space above the coke cake in which the
coal
destined for carbonization is warmed-up after charging, and wherein
= the side walls accommodate channels which are suitable for aspirating a
negative pressure, and wherein
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= a combustion system for combustion of non-burned volatile coal
constituents as well as gases generated on partial oxidation is arranged
beneath the coke
oven chamber, and wherein
= the coke oven chamber in its side walls contains channels and wherein
these channels connect the upper coke-free section of the coke oven chamber on
the gas
side with the combustion system beneath the coke oven chamber,
and which is characterized in that
= the combustion system beneath the coke oven chamber is equipped with
outward-leading secondary channels through which the combustion system can be
charged with a negative pressure, so that
= the oven free space above the coke cake can be charged with a negative
pressure via the combustion system and the channels, and wherein
= at least one of the outward-leading secondary channels is equipped with a
regulating device.
Depending on the magnitude of the vacuum receiver tanks or aspirating device
in
relation to the demanded vacuum, the locking mechanism in the connection
between the
vacuum receiver tank and secondary heating space is configured accordingly. If
the
vacuum receiver tank is small and provided for taking-up an elevated negative
pressure,
the locking mechanism must open quickly and completely. In this case, a slide
gate is
suitable, for example. It opens the secondary channel between the vacuum
receiver tank
and the secondary heating space shortly and completely so that a sufficient
negative
pressure is generated in the primary heating space via the secondary heating
space and
the channels lying there in between. However, if the volume of the vacuum
receiver tank
is large in relation to the required negative pressure, a spindle will be
sufficient for fine
dosing, for example.
In one embodiment of the inventive device for controlling the negative
pressure in
a coke oven chamber during the coke pushing and coal charging procedure, claim
is laid
to a channel that contains a regulating device for the vacuum, and which
connects the
secondary heating space with the suction side of an aspirating device, with
the regulating
device being a slide gate.
In another embodiment for controlling the negative pressure in a coke oven
chamber during the coke pushing and coal charging procedure, claim is laid to
a channel
which utilizes a spindle instead of the slide gate as regulating device.
Finally, in another
embodiment for controlling the negative pressure in a coke oven chamber during
the coke
pushing and coal charging procedure, claim is laid to a channel which utilizes
a flap as
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regulating device. In principle, however, every regulating device effecting
the adjustment
of a vacuum in the primary heating space via the channels in the side wall
through
secondary channels at the desired level and within the desired requisition
period is
deemed suitable.
The inventive method and the device utilized for this purpose bear the
advantage
in that on opening the coke oven chamber doors, a negative pressure is shortly
generated in the oven free space above the coke cake so that the flue gases
evolving on
coke pushing after opening the doors are aspirated into the interior of the
primary heating
space instead of escaping into the atmosphere, this method and the device
prompted
thereby requiring no space, neither on the coke oven chamber ceiling nor in
front of the
coke oven chamber doors. Non-desired emissions into the atmosphere and the
liberation
of flue gases representing a danger to environment and plant staff are thus
avoided.
The inventive device is hereinafter explained by way of two drawings. These
drawings just represent examples of embodiments for the design and
construction of the
inventive device, which are not restricted to these embodiments.
FIG. 1 shows a lateral view of a coke oven chamber (1) comprised of a primary
heating space (2) and a secondary heating space (3). Gases evolving on coal
carbonization stream into the primary heating space (2), where they are
partially burned
and where the partially burned coking gas streams via channels (4) in the side
walls of
the coke oven chamber (1) or in the coke cake (5) into the secondary heating
space (3)
arranged beneath the coke cake (5). There it is completely burned, thus
heating the coke
cake (5) from below. The completely burned coking gas is passed on to a waste
gas
discharge (6) comprised of a shutoff device (6a) and terminating into a waste
gas channel
(6b). To be seen here, too, are the apertures (4a) of the "downcomer" channels
in the
primary heating space (2) through which the negative pressure is aspirated
(4b). Now, if
the doors (7) of the coke oven chamber are opened for coke pushing and coal
charging,
the feed of primary air which in this case is accomplished via apertures for
primary air in
the ceiling with a U-tube-shaped cover (8) is shut-off through appropriate
shutoff devices
(8a) for primary air. The discharge of waste gases (6), too, from the
secondary heating
space (3) is shut-off via appropriate shutoff devices (6a) for waste gas. The
locking
devices (9) at the apertures for the feed of secondary air into the secondary
heating
space (9) are shut for this procedure. The valve (10a), which for example may
be a slide
gate for the vacuum receiver tank (11) is opened, thereby generating a
negative pressure
in the primary heating space (2) via the secondary channel (10), the secondary
heating
space (3), and the channels (4). According to the present invention, the flue
gases are
thereby sucked into the primary heating space (2) during the opening of the
coke oven
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chamber doors (7). After the procedure of aspiration, the vacuum in the vacuum
receiver
tank (11) can be restored by means of a vacuum pump (12) via a vacuum line
(13)
equipped with a shutoff device (13a).
FIG. 2 shows a lateral view of a coke oven chamber (1) comprised of a primary
heating space (2) and a secondary heating space (3), wherein a vacuum-
generating and
pressure-regulating vacuum line (14) are additionally arranged on the ceiling
of the coke
oven chamber (1), an example of which is described in GB 365934 A. In
particular, it
serves the purpose of regulating the pressure in the coke oven chamber (1)
during
operation. To this effect, a vacuum line (14) connected to all coke oven
chambers is
arranged on the ceiling of the coke oven chamber (1). For fastening on the
coke oven
chamber (1), it is equipped with a holding device (14a). Via a connecting line
(14b)
including valve (14c) and pressure regulating device (14d) the pressure in the
primary
heating space (2) of the coke oven chamber (1) is controlled during operation.
In this
embodiment, the valve (14c) for the connecting line is shut during the vacuum
aspiration
phase via the "downcomer" pipes (4), so that the pressure regulating device
(14d) is not
connected to the coke oven chamber (1) during the aspiration phase. In this
embodiment, the doors (7) of the coke oven chamber (1) are open so that the
coke cake
(5) can be pushed out. To be seen here, too, is the wall (7a) above the coke
oven
chamber door (7). According to the invention, a negative pressure is aspirated
now via
the "downcomer" channels (4) during this period of opening the coke oven
chamber doors
(7) in order to suck the flue gases back into the coke oven chamber (1).
Instead of U-
tube-shaped apertures (8a) on the ceiling, there are simple apertures (8c)
installed there
which are equipped with a flap (8d) that can be opened. The first of these
doors (7b) is
opened for charging, while the other door (7) closes the coke oven chamber
(1). To be
seen here is the charging of the coke cake (5) accomplished via a vehicle (16)
with the
pushing device (15a). The vehicle (15) rests on rollers (15b) which in turn
are arranged
at plane ground level (16) In this embodiment, the waste gas channel (6b) is
arranged
below ground, with the feeder of the secondary channel (10) being located
upstream to
the shutoff valve (6a) of the waste gas channel. It is provided with a valve
which is
opened in this case (10b). Thereby, the secondary channel (10) is connected to
the
vacuum receiver tank (11), aspirating a negative pressure from it. Located at
the end of
the suction device and connected via the secondary heating space (3) and the
"downcomer" channels (4) is the coke oven chamber (1).
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List of Reference Numbers
1 Coke oven chamber
2 Primary heating space
3 Secondary heating space
4 Channels
4a Apertures of "downcomer" channels
4b Aspirated negative pressure
Coke cake
6 Waste gas discharge
6a Shutoff device for waste gas
6b Waste gas channel
7 Coke oven chamber doors
7a Coke oven chamber wall above the coke oven chamber door
7b First door of the doors (7b), opened for charging
8a Apertures for primary air in the ceiling with U-tube-shaped cover
8b Shutoff device for primary air
8c Apertures for primary air in the ceiling
8d Flap for locking the apertures for primary air in the ceiling
9 Locking devices at the apertures for the feed of secondary air
9a Locking devices at the apertures for the feed of secondary air
Secondary channel
10a Shutoff device for secondary channel
10b Valve for secondary channel which is opened in this case.
11 Vacuum receiver tank
12 Vacuum pump
13 Vacuum line
13a Shutoff device for vacuum line
14 Vacuum line
14a Holding device for vacuum line
14b Connecting line for vacuum line
14c Valve for connecting line
14d Pressure regulating device
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15 Vehicle
15a Pushing device
15b Rollers
16 Plane ground level
11
