Note: Descriptions are shown in the official language in which they were submitted.
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'iA method ~f keeping hot an inoperative regenerator
during repair in a coke-oven battery"
BACKGROUN~ GF rrHE INVENTION
1 FIELD OF THE INVENTION
_
The invention relates to a method of keeping
hot a regenerator of a coke-oven battery while the
regenerator is out of operation during repair. Such
a regenerator, which itself may or may not be the subject
of the repair, is here referred to as "inoperative".
2. DESCRIPTION OF THE PRIOR ART
A horizontal coke-oven battery comprises
a number of coking chambers separated by so-called
combustion walls. Combustion chambers are arranged
in eaeh combustion wall. Beneath the row of coking
chambers and the combustion cha~bers, there are regenerators
for pre-heating the combustion air fed to the combustion
chambers. Each regenerator contains a heat-storage
strueture, typically a structure known as the checker
work, which stores and releases heat in order to effect
heat exchange in the regenerator. The whole construction
is of refractory material with a predominance of silica
bricks, fireclay bricks possibly also being used in
the less hot regions.
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~ uring operation of the battery, gas (e.g.
coke-oven gas) is burned in the combustion charnbers.
The heat thereby liberated is conducted through the
combustion chamber walls to the coking coal in the
coking chambers to effect the c~oking. The waste
(i.e. exhaust) gases released during combustion are
led through one half of the plurality of regenerators,
which are heated by the waste gases, and the waste
gases are then discharged through a stack. At the
same time air is led through the other regenerators,
which air is heated and supplied as warm combustion
air to the combustion chambers. The regenerators have
a large thermal capacity because of the checker work.
After a period of e.g. half an hour the regenerators
are reversed, air is conducted through the now warmed
regenerators, and the cooled regenerators are heated
by waste gases.
To conduct the waste gases and air, there
is in the refractory construction a complicated system
of connecting ducts in the spaces between the combustion
chambers and the regenerators. Various systems are
known for connecting the regenerators and combustion
chambers, which it is not necessary to discuss here.
The invention will be discussed here for in relation
to a particular system, namely the Coppée sys em,
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in which alternate regenerators are coupled at any
time to waste gas and air respectively. However, the
invention also relates to other systems such as for
instance the Still system. A regenerator is said to
be "on air" when it passes air and "on gas" when passing
the hot waste gas.
As has already been mentioned the refractory
construction is largely built of silica brick. On
being heated from room temperature to 400-600C, the
silica material exhibits a very large expansion. On
the other hand, its expansion in the operating temperature
range is very small. A problem always arises when
a regenerator of a coke-oven battery in operation cools
below the temperature of 400C mentioned above and
enters the high expansion range. Shrinkage cracks
occur in the refractory construction which do not close
up again when the regenerator is brought back up to
operating temperature. Air from a regenerator on air
can enter a regenerator on gas via these cracks. As
a result, combustion in the combustion chambers suffers
from a deficiency of air so that there is local occurrence
of so-called "cold spots" at the coke side and/or the
pusher side of the battery. As a result of incomplete
combustion in the combustion chambers, after-combustion
can occur in the regenerators, with consequent melting
of the checker bricks.
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I'he problem of an excessively cooled regenerator
occurs above all when the regenerator as a whole is
receiving no further waste gas, because the combu~tion
chambers with which it is connected are out of operation.
Such a situation arises during the repair of two (or
more) adjacent combustion walls, a so-called "two
wall repair" although the present invention is also
applicable in less radical repair situationO
DE-OLS 2 124 618 and 2 122 729 both of
Heinrich Koppers GmbH describe a repair process for
coke-oven batteries in which the inoperative regenerator
is kept hot by the use of additional burners located
above the checker work of the regenerator. This method
is not satisfactory primarily because the heating
effect is by radiation from the combustion at the
burners which causes an uneven temperature distribution
and consequently variations in thermal expansion in
the regenerator walls. This leads to cracks in the
walls. Other disadvantages are the cost of the fuel
supplied to these burners and the danger of explosion.
SUMMARY OF THE INVENTION
The invention is intended to provide a method
in which excessive cooling of an inoperative regenerator
is avoided.
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According to the invention the waste gas
flow of one or more operating regenerators is conducted
to the inoperative regenerator from a location upstream
of the heat-storage structure of the operating regenerator(s).
The main advantage of this is that the regenerator
can be held at a temperature which is so high that
the occurrence of shrinkage cracks is prevented.
Another advantage is that, when the regenerator is
brought back into operation it reaches the operating
temperature more rapidly, so that the repaired region
is not out of operation for so long and the loss of
production is limited.
Preferably the hot waste gas is supplied
to the inoperative regenerator through one or more
by-pass lines arranged for the duration of the repair
in at least one "meistergang" of the battery (also
known as the bench gallery). The by-pass lines may
then be connected to a regenerator by means of a passage
in the front wall of the regenerator. This passage
into the regenerator opens above the checkerwork in
the regenerator.
In order to avoid loss of heat ~rom the
inoperative regenerator in the period during which
this regenerator, if it were operating, would be on
air, the air inlet valve of the inoperative regenerator
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should be kept continuously closed during the inoperative
period.
In order to avoid loss of heat from the in-
operative regenerator in the period during which waste
gas from one or more operating regenerators are conducted
to the inoperative regenerator, as a result of unwanted
cold air entering through the ducts connecting it with
inoperative combustion chambers, these connecting ducts
should be blocked during the inoperative period. Preferably
these connecting ducts should be blocked at their openings
in these combustion chambers.
In order to prevent the temperature of the
inoperative regenerator from falling too low and the
temperature of the operating regenerator(s) delivering
hot waste gas from being too much affected, preferably
the temperature of the inoperative regenerator is measured
and is then regulated by displacement of a butterfly
valve in the waste gas outlet of this regenerator and/or
the butterfly valves of the operating regenerator(s)
which are connected to it.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the invention will
now be described by way of non-limitative e~ample with
reference to the accompanying drawings, in which:-
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Fiy. 1 is a vertical longitudinal sectionthrough a plurality of coking chambers of a coke-oven
battery.
Fig. 2 is a vertical transverse section through
a combustion wall of the coke-oven battery of Fig.
1.
Fig. 3 is a schematic plan view of one part
of the coke oven battery of Fig. 1.
Fig. 4 is a schematic plan view of the coke-
oven battery showing the by-pass lines.
Fig. 5 is a vertical longitudinal section
at the location of the regenerators of the coke-oven
battery showing the by-pass lines.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As has already been mentioned, the invention
is discussed here in relation to a coke-oven battery
of the Coppée system.
Fig. 1 shows a coke-oven battery having coking
chambers 1 and intervening combustion walls 2 in which
combustion chambèrs 3 are arranged. Below the coking
chambers there are regenerators 4, which are connected
with the combustion chambers 3 by connecting ducts
5, and which are each connected at their bottom ends
to a waste gas duct 10 via a reversible valve chest
6, which contains a waste gas valve 7 and waste gas
outlet ~, the latter having a butterfly valve 9.
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The waste gas duct 10 is connected to a flue which
is not shown. An air inlet valve 12 is also arranged
in the reversible valve chest 6. The regenerators
4 are filled with checker work 13. Gas supply ducts
15 also open in the floors 14 of the combustion chambers
3.
It may be seen from the vertical cross-section
of Fig. 2 that in a combustion wall 2 there are a large
number, for instance 24, combustion chambers 3 connected
with resenerators via the connecting ducts 5. The
combustion chambers 31 are connected to a regenerator
on air via connecting ducts 51. These combustion
chambers are in connection with neighbouring combustion
chambers 32 via ports 16. The waste gas generated
by eombustion in the combustion ehambers 31 and 32
is discharged via eonneeting duets 52 to the regenerator
on gas 4 and is further diseharged via a eolleeti.ng
duet 17 via the reversible valve ehest and the waste-
gas duet to the staek (not shown in the figure).
Fig. 3.shows the arrangement of several
combustion ehambers and regenerators in a sehematie
top view of a eoke-oven battery. The regenerators
loeated below two adjaeent eoking ehambers are indicated
by the reference numbers 718 and 719. The combust.ion
walls between the coking chambers are indieated by
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references 717/718, 718/719 and 719/720. Each combustion
wall has a plurality of combustion chambers 3, which
each have a gas supply duct 15 and connecting ducts
5 to the regenerators. Fig. 3 shows for example the
situation in which regenerator 718 is on air, that
is to say it is delivering heated combustion air to
the combustion chambers in the combustion walls 717/718
znd 718/719. At the same time regenerator 719 is on
gas, i.e. receives waste gas from the combustion walls
718/719 and 719/720. This is the normal mode of operation.
The danger of shrinkage cracks in the regenerators
is especially prominent when both the combustion walls
718/719 and 719/720 are not operating. Then regenerator
719 as a whole is no longer receiving waste gas. This
situation occurs with the repair of these two (or more)
combustion walls. The regenerator 718 is no longer
receiving waste gas from wall 718/719 but only has
to deliver air to wall 717/718. The temperature of
this regenerator is however affected by heat leakage
to the cold regenerator 719 and as a result the regenerator
718 cools.
In Figs. 4 and 5 illustrate for this embodiment
the measures to be taken (with regenerator 719 inoperative)
according to the invention in the above situation.
The waste gas of other operating regenerators is supplied
to regenerator 719. It is preferred that this waste
gas is not provided by the adjacent regenerators 718
and 720, since these are, as already discussed, at
half power and i.n addition are losing heat already
because of heat leakage to regenerator 719. In addition
the waste gas valves of regenerators 718 and 720 are
operated in counter~phase with those of regenerator
719. Similarly, there is the possibility of supply
of waste gas from regenerators 717 and/or 721. However
these regenerators are subject to heat leakage to the
regenerators 718 and 720. Although the quantity of
heat to be supplied to the inoperative regenerator
719, in order to compensate for the heat leakage from
it to the exterior, is not large in comparison with
the heat exchanged in an operating regenerator, this
may cause a disturbance which acts adversely on coke
production. Fig. 4 shows that the hot waste gas is
in this embodiment supplied from the regenerators 715
and 723 which are relatively far from the inoperative
regenerator 719.
Although the hot waste gas can be supplied
by one operating regenerator, there is the preferred
possibility since a regenerator is usually divided
by an intermediate wall 18 into two compartments 19
of supplying the hot waste gas to each compartment
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from one operating regenerator. Waste gas can also
be supplied to one compartment from several operating
regenerators, if the action of one operating regenerator
would be adversely affected by the loss of hot waste
gas to an inoperative regenerator compartment.
- The hot waste gas is supplied via by-pass
lines 20, which are arranged in a space 21 known to
the industry as the l'melstergangll or llbench gallery"
(see also Fig. 2). The by-pass lines can be mounted
in the bench gallery on the pusher side or in the bench
gallery on the coke side of the coke ovens, or in both.
'The hot waste gas is supplied via the by-pass lines
20 whicn are connected to a regenerator compartment
715, 719 and 723 by means of an aperture 22 in the
so~called front wall 23 of each regenerator, with the
aperture in the regenerator compartment in each case
opening above the checker work 13 (see also Fig. 2).
The advantage of this is that the hot waste gas is
supplied to the inoperative regenerator in a duct
bounded by the vault 24 of the regenerator and the
checker work, so that the heat penetrates deep into
the compartment and is distributed evenly over the
compartment.
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FigO 2 thus shows that the hot waste gas
supplied to the operating regenerators is partly diverted
to the inoperative regenerator from a location upstream
of the checkerwork of the operating regenerators.
When regenerators 715 719 and 723 are gas,
that is to say the waste gas valves 7 are open, the
waste gas i~ drawn through the by-pass lines 20 -to
the inoperative regenerator 719 by the gas outlet flue
draught. At the same time, however, cold air may be
led via the connecting ducts 5 of the combustion chambers
in the inoperative combustion walls 718/719 and 719/720
to the regenerator 719, thus hindering the maintenance
of the regenerator at temperature. To prevent this,
connecting ducts of the inoperative combustion chambers
are therefore kept closed during the repair; particularly
the ports 25 (see Fig.l) at ~hich the connecting ducts
open into the floor 14 of the combustion chambers are
blocked.
When the regenerators 715,719 and 723 are
on air, i.e. the waste gas valves 7 are closed and
the air inlet valves 12 are open, air may be brought
via the by-pass lines 20 from regenerator 719 to regen-
erators 715 and 723. This not only affects the action
of regenerators 715 and 723, but also partly neutralizes
the effect of the hot waste gas brought to regenerator
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719. Therefore to prevent this the air inlet valves
of the inoperative regenerator are kept continuously
closed during the repair.
In this embodiment of the method of 'he invention,
the temperature of the inoperative regenerator is
monitored by measuring the temperature of the regenerator
for instance by means of thermocouples in the regenerator,
and optionally by measuring the temperature of the
waste gas in the reversible valve chest 6 and taking
this as a measure of the regenerator temperature.
From this data relating to the temperature of the
regenerator, this temperatùre is then controlled by
adjustment of the butterfly valves 9 in the waste gas
outlets of the inoperative regenerator 719 and the
operating waste gas supply regenerators 715 and 723.
