EP0478509A1

EP0478509A1 - Degraphiting system for coke ovens

Info

Publication number: EP0478509A1
Application number: EP91830234A
Authority: EP
Inventors: Renato Boccia
Original assignee: Ilva SpA
Current assignee: Ilva SpA
Priority date: 1990-09-28
Filing date: 1991-05-30
Publication date: 1992-04-01
Also published as: IT1242356B; IT9048321A0; IT9048321A1

Abstract

The pusher machine on coke ovens is equipped with a mobile blowing device which is automatically positioned and comes into operation after the pusher ram has started to push the mass of incandescent coke out of the oven. Once the blowing has finished and before the pusher ram has been extracted from the oven, the device is withdrawn.

Description

The present invention concerns a system for degraphiting coke ovens, namely the removal of carbon build-up therefrom. More preclsely, it conerns an air-blowing system which is positioned and operated in the lapse of time between the introduction and extraction of the pusher ram.
Coke is produced in batteries of distillation ovens measuring several metres in length and height but only a few decimetres in width. Between one oven and the next are heating flues through which circulate hot gases. The ovens are filled with coal via charging-holes at the top. The filling operation is performed in a set sequence, as is the subsequent pushing operation, which is carried out by a machine on the pusher (front) side of the ovens to ensure that the coke produced is pushed out on the coke (rear) side. During the time the charge is being heated, with the aid of a carefully calculated quantity of air which is introduced into the ovens, the volatile matter contained in the coal distils and is removed from the coking chambers through offtakes known as ascension pipes.
Part of the distilled substances, whose nature is essentially organic, decomposes and leaves a solid, carbonaceous, graphite like deposit on the walls of the ascension pipes, tending to block them, thus increasing the pressure within the ovens.
This results in a variety of problems, such as:

escape of hot gases and combustible materials from the oven doors and charging-hole covers; these gases may start to burn, thus causing local overheating of the doors and covers; this may lead to distortion of the seals which further aggravates gas leaks that not only damage the doors but also pollute the environment
leakage of gas from the distillation ovens to the adjacent heating or combustion flues, causing the escape of black smoke and an increase in pollution
high thermal stresses on the oven support structures, leading to the malfunctioning of the ovens themselves and possible damage thereto.

As it is impossible to prevent these carbon deposits, they must be removed. Where the ascension pipes are concerned, this is done at the present time by scraping or by combustion induced via natural or forced air circulation through the relevant offtakes. These methods have not so far been automated. Hence they require the presence of an operator at the door of the oven or on the top, namely in positions where working conditions are very difficult and dangerous. Furthermore, the operations must be performed when the oven is empty, leading to delays in the oven operating sequences.
Quite evidently the problem of carbon build-up in the ascension pipes has repercussions from the ecological, industrial-safety and economic aspects, because of the damage it causes to the installations and the loss of production.
The object of this invention, therefore, is to attenuate the problem of environmental pollution, improve working conditions on the batteries and reduce damage to the ovens, while raising productivity, through a system for eliminating graphitic carbon deposits from the ascension pipes, which is implemented effectively during the coke-pushing operation without requiring the presence of operators in the immediate vicinity.
According to the invention, in a coke battery consisting of side-by-side coke ovens each having the form of a straight parallelepiped whose height and length are both much greater than the width, and each complete with a floor, a roof, side walls and front and rear end walls each having a removable door, and with an ascension pipe for removal of the distillation gas, and in which a pusher machine complete with a pusher ram is positioned on the front or pusher-side of the ovens and can move parallel to said side, a system is introduced for cleaning said ascension pipes, consisting of means for blowing oxidizing gas, preferably air, mounted on said pusher machine, and movable towards said coke ovens, controlled automatically by the movement of the pusher ram so that it can advance inside an oven and blow said oxidizing gas into the ascension pipe after the pusher ram has penetrated into the oven, and can then be withdrawn from the oven to the "rest" position in the pusher machine before the pusher ram is extracted from the oven.
Said air-blowing devices can advantageously consist of a boom mounted on a movable carriage with a pipe through which the air is blown. At the end of the pipe is an upward-facing nozzle which directs a jet of air into the ascension pipe.
Said boom, can advantageously be cooled so that it is not damaged by exposure to the high temperatures encountered at the entrance to the coking chamber.
The present invention will now be described in greater detail by reference to an embodiment illustrated by way of example in:

Fig.1 - which provides a partial sectional view of a coke oven fitted with the system as per the invention, prior to it being brought into action
Fig.2 - which represents the same view as above, but with the system advanced into the oven and operating.

In both Figures the same parts are indicated by the same numbers: 10 indicates the coke oven as a whole, seen partially in section, and 20 the coking chamber proper, in section, complete with a front (pusher) side 21 and a rear (coke) side 22, a floor 28 and a roof 23 in which there are charge-openings 24 and the ascension pipe 25 located near the front side. The oven also has a front bench 11, a rear bench 12 and a steam drum 15 for collecting condensate deriving from the destructive distillation of coal in the various ovens and extracted therefrom via ascension pipe 25 and other similar pipes on each unit. The oven is served by a pusher machine 30, which moves parallel to the front side of the ovens 21, and by a coke guide 13, which moves along the rear bench 12, as well as by a quenching car 14 which runs parallel to the rear side 22 of the ovens.
The front and rear doors of the coking chamber 20 are not shown.
The pusher machine has a pusher ram 31 with a pusher head 32, as well as a levelling bar 33 which levels the coal charge that is loaded through charge-openings 24.
According to the present invention, the pusher machine 30 is fitted with a blowing boom 35, which is complete with a blowing nozzle 36, and moves on a carriage 34 from a withdrawn position, shown in Fig.1 to an advanced position, shown in Fig.2 where said nozzle is positioned at the inlet to ascension pipe 25 in roof 23.
The oxidizing gas, air for example, is carried to boom 35 by flexible hose 37.
As already mentioned, when the oven is in operation the volatile matter present in the coal distils and is deposited as carbon build-up on the walls of ascension pipe 25.
When distillation is complete in a cokins chamber, the pusher machine 30 is spotted on the front side 21 of the oven, while the coke guide 13 and the quenching car 14 are spotted on the rear side 22 of the oven whose doors are then opened.
The pusher machine 30 advances ram 31 which pushes the coke 40 out of the oven into quenching car 14.
Immediately after pusher head 32 has pushed the coke beyond the position of ascension pipe 25, carriage 34 is advanced and boom 35 is brought into the operating position, its blowing nozzle 36 being opposite the inlet to ascension pipe 25. Blowing of the oxidizing gas is then commenced; this burns off the carbon deposit 27 and the internal dimensions of the ascension pipe are restored to normal.
Esperience with specific distillation conditions will indicate the best length of time for blowing oxidizing gas into each oven. This blowing must, of course, cease and the blowing boom be withdrawn to its "rest" position before the pusher ram is drawn back into the pusher machine.
Use of the system as per the invention has produced the following benefits:

reduction of gas leaks from the doors: 85%
reduction of door maintenance: 40%
elimination of black smoke
increase in production: 5%.

Claims

1) Degraphiting system for coke ovens, in which a battery consisting of several side-by-side ovens each having the form of a straight parallelepiped whose height and length are both much greater than the width, and each complete with a floor, a roof, side walls and front and rear end walls each having a removable door, and with an ascension pipe for removal of the distillation gas, which passes through the roof near the front or pusher side, and in which a pusher machine complete with pusher ram is positioned on said front side and can move parallel to said side, characterized by the fact that said pusher machine is provided with a means for blowing oxidizing gas, which can move towards the coke ovens, controlled by the movement of the pusher ram to advance into a coke oven and blow said oxidizing gas into the ascension pipe therein, and is then withdrawn from the oven to the "rest" position in the pusher machine before the pusher ram is estracted from the oven.

2) Degraphiting system for coke ovens, as per claim 1, in which said means for blowing consist of a boom mounted on a movable carriage, complete with a pipe for the oxidizing gas which has a blowing nozzle on the free end.

3) Degraphiting system for coke ovens as per claim 2, in which said boom is cooled.

4) Degraphiting system for coke ovens, as per claim 1, in which said oxidizing gas is air.