The present invention relates to coke ovens. As is well
known, the distillation chambers of batteries of coke ovens are all connected individually
via pipes (called "goosenecks") to a manifold, the so-called "collecting main".
The pressure inside the collecting main is critical. Normally it is maintained above
atmospheric pressure, for example approx. 150 Pa, taking care that the pressure
in the collecting main does not become negative, because if this were to occur air
might enter the oven and cause combustion of the coke, with fusion of metallic parts
and even of refractories. The reason why such a high pressure is maintained in the
collecting main is that the collecting main is always connected to different ovens
at different moments of the distillation time. For example, in a battery of coke
ovens the collecting main communicates via the goosenecks with an oven that has
just been charged, and so has a huge flow rate of distilled gas, whereas the adjacent
oven is now in the 15th or 16th hour of distillation and so is practically at the
end of the distillation stage, and it now has a low flow rate. There might be a
pressure of the order of 350-400 Pa in the first oven, whereas at some points in
the adjacent oven, for example at the bottom of the oven door where there is a draught
effect due to the gooseneck, the pressure will be very close to atmospheric. Thus,
if for example the pressure in the collecting main were to fall from a value of
150 Pa to a value of the order of 20 Pa, that would be advantageous for the oven
in which the charge is at the start of distillation, but would be harmful for the
adjacent oven which is at the end of distillation and would develop negative pressure,
with the disadvantages previously mentioned. In practice, in a coke plant in which
all the goosenecks are all identical, all open and so have the same loss of head,
it is not possible to bring the pressure in the collecting main below a value of
about 150 Pa without causing enormous pressure losses in the ovens which are now
at the end of distillation.
In coke plants, at the point where the goosenecks are connected
to the collecting main, a special valve is installed, called a "pot valve" because
it resembles a large bowl with a hydraulic seal.
In existing coke plants, the pot valve is open throughout
the distillation time. It is in fact an "on-off" valve which serves exclusively
for isolating the collecting main by means of a hydraulic seal when the coke has
to be discharged from the distillation chamber in question. At that time the pot
valve is made to engage in the pipe union comprising the gooseneck with a hydraulic
pressure head so as to permit the coke to be discharged, while preventing the gas
present in the collecting main from escaping into the environment.
It had been proposed in the past to use this pot valve
as a device for manual control of the flow rate from the ovens into the collecting
main, so as to keep the pressure in the collecting main more or less constant by
manually constricting the opening between the gooseneck and the collecting main.
However, this known system is not reliable and requires skilled manpower for its
Effecting this control with a hydraulic system has also
been proposed by Deutsche Montantechnologie GmbH and by Thyssen Krupp Stahl AG,
in practice with a variable-level hydraulic seal, in such a way that constriction
is provided by a head of water, the level of which is regulated during operation
of the oven.
This system, though reliable, requires considerable structural modification of existing
Therefore the main aim of the present invention is to decouple
the pressure of the collecting main from that of each individual oven in a simple
manner, without having to make extensive modifications to plant that is currently
This aim is achieved by replacing the solenoid valve controlling
the on-off operation of the pot valve, keeping it open throughout the distillation
time and only making it close at the time of discharge with a proportional solenoid
valve actuated by a sensor of the pressure of the oven to which said valve is connected,
so as to vary the position of the pot valve, and hence the constriction of the gooseneck,
as a function of the pressure variation in the oven, which is in its turn a function
of the distillation time.
Advantageously, said proportional valve is coupled with
a positional transducer to show the position of the pot valve at any given moment.
According to a further characteristic, the present invention
relates to a particular profile of the pot, which has been designed in such a way
that the latter does not give rise to resonances and various fluctuations. For this
purpose, a block formed from a hollow metal structure with a curvature designed
to follow the movement of the pot has been mounted on an existing pot.
Further aims and characteristics of the present invention
will become clearer from the following description of a preferred embodiment of
the invention, illustrated in the appended drawings, in which:
- Fig. 1 shows a top view of the detail of a gooseneck of a distillation chamber
of a coke oven connected to the collecting main;
- Fig. 2 shows in longitudinal section, on an enlarged scale, a detail of the
assembly in Fig. 1, illustrating the pot valve for controlling the opening between
the gooseneck and the collecting main, in the fully open position.
- Fig. 3 is a view similar to that of Fig. 2, showing the pot valve in a position
of partial constriction of the opening between the gooseneck and the collecting
- Fig. 4 is a view similar to those of Figs. 2 and 3 with the pot valve in a position
of complete closure of the opening between the gooseneck and the collecting main.
Although in Figs. 2 to 4 the pot valve is shown as being
provided with a hollow metal structure or "block", it is to be understood that said
structure can also be absent.
Referring to the drawings, and with special reference to
Fig. 1, the numeral 1 indicates a fragment of the roof of a distillation chamber
of a coke oven, from which the gooseneck 2 is connected, via the interposed pot
valve 3, to the collecting main 4.
Referring to Fig. 2 of the drawings, the end of the gooseneck
2 is connected to the pipe union 102 provided with a truncated-cone end 202 that
fits into collecting main 4.
The pot valve, indicated in its entirety as 3, comprises
the stopping element or pot proper 103, generally comprising a circular plate with
raised edges with inside diameter such as to permit insertion therein of the truncated-cone
end 202 of the pipe union 102.
The pot 103 is connected at one end to a pin 203 supported
in an oscillating manner by the casing of valve 3. In its turn, pin 203 is provided
at its end with a lever 403 hinged to the end of the rod 105 of the piston of a
hydraulic jack 5.
As is well known, normally the pot valve is a valve with
on-off action, that is, either it is operated by a solenoid valve in the fully open
position, as shown in Fig. 2 in the drawings, or it is operated in the fully closed
position (position in Fig. 4 in the drawings).
In accordance with the present invention, the solenoid
valve controlling the on-off operation of pot valve 3 has been replaced with a proportional
solenoid valve EP controlled by a sensor S of the pressure of the oven to which
said valve EP is connected, so as to vary the position of the pot valve 3, and therefore
the constriction of the gooseneck 2, with the variation of the pressure in the oven,
which is in its turn a function of the distillation time.
Advantageously, said proportional valve EP is coupled to
a positional transducer TP to enable the position of the pot valve 3 to be known
at any given moment.
In this way it is possible to have a reduced pressure in
collecting main 4, for example a pressure of 10 Pa, i.e. a pressure that is very
close to the ambient pressure so that when the pressure in an oven rises to 300-350
Pa, complete opening of the pot valve 3 is operated by means of a signal of the
pressure detected in the oven by the sensor S, allowing the gas to pass completely.
With operation in this manner, there is no risk of negative
pressure arising, since the oven that has just been charged develops a tremendous
pressure and the pressure of the collecting main 4 will be low but controlled to
values capable of maintaining a certain excess pressure in the distillation oven.
As distillation proceeds, the flow rate of oven distillate decreases and therefore
the oven pressure also decreases. This decrease is detected by the pressure sensor
S which gradually causes pot valve 3 to close (position in Fig. 3). At the end of
distillation, the flow of distillate is so reduced that the pot 3 remains in the
almost-closed position, with a minimal gradient, barely sufficient to cause draining
of the water that falls on it continually and maintaining a small slit for passage
of the gas, production of which has practically ceased.
According to a further characteristic, the present invention
relates to the profile of pot 103. For this purpose, a curved tubular metal structure
6 (shown in Figs. 2 to 4) has been mounted on pot 103 and has a curvature such that
it follows the movement of pot 103.
Said structure 6 has, preferably at the base, openings
7 to allow the condensed water to flow freely into the well of pot 3, so as to produce
the necessary hydraulic pressure head.
Owing to this structure, there is much better control both
of the pressure and of the flow rate of the gases entering the collecting main 4.
Of course, the present invention is not limited to the
embodiments that have been illustrated and described, but comprises all variants
and modifications falling within the wider scope of the innovative concept, as claimed