Patent Application
20120247939
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 U.S. Pat. No. 4,344,820 A or U.S. Pat. No. 4,287,024 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 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.
U.S. Pat. No. 3,844,901 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 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 600° C. 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 1000° C. 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.
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
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 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
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 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102009052502.5 | Nov 2009 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP10/06603 | 10/28/2010 | WO | 00 | 4/20/2012 |
