Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A SYS~I FOR SUPpLyING ~RE~HEATED ~O~L
TO A COKING O~N B~TTER~
THIS INYENTION relates ~o coking ovens and
in particular a system for supplying pre~heated coal
to a coking oven battery,
Several processes are ~own for the pre-
heating and charging of coking coals into slot-type
coking ovens. These processes differ both in the
method in which the coal is pre~heated and also the
method by which the coal is charged into the coking
ovens.
The pre-heated coal may be conveyed and
charged into the ovens by several different methods,
for example, by the use o a charging car, by steam or
gas operated pipeline conveyor systems, or by
mechanical conveyors.
Combined pre-heating and charging plants
require intermediate storage units for pre~heated coal
in order to provide the necessary transition between
the continuous operation of the pre~hea~ing and
conveying section and the batch operation of the
meLering and charging sections.
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For effective and economic operation, the
equipment used for conYeying, metering and charging
the coal is physically separated ~rom the pre-heatîng
equipment~ and as a result the hot process gases which
are circulated within the pre~heating section and
which are used to pre-heat the coal, are excluded from ~,
the conveying, ~etering and charging equipment.
To reduce the level of oxidation of the pre-
heated coal and to reduce the risk of ire and explosion
it is necessary to maintain the pre-heated coal in an
inert environment whilst is is being conveyed, stored
and metered prior to charging.
The inert environ~ent has been provided by
introducing products of combustion from burning gaseous
fuels in near~stoichiometric conditions, or by
introducing steam or nitrogen or other gaseous compounds
of a sufficiently low oxygen content.
In practice, if any type of combustion
products are used as the ineTtising medium~ blockages
may occur in the conveying system due to the increased
moisture in the pre-heated coal caused by condensation
from the combustion products as they cool. Such
problems are avoided when using dry ni~rogen or any
inert gas with a low water vapour content as an
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inertising medium, but such gases may not be readily
available and in any case have proved costly to supply
on a continuous basis.
~n object o the pre5ent in~ention is to
provide a new and economic method of supplying and
controlling an inertising medium or the conveying~
storage and metering sections of a coal pre-heating
and coking oven plant.
According to the present invention there is
provided a system for supplying pre-heated coal to a
coking oven battery, comprising a conveying section,
a plurality of storage bunkers for receiving the coal
from the conveying section, a plurality of metering
bins for receiving the coal from the storage bunkers
lS and for transferring same in metered quantities to the
coking ovens, and an inert gas source adapted ~o
introduce inert gas to the conveying section and to
the storage bunkers, characterised by an inert gas
reservoir adapted or connection selectively to the
inert gas source or to said metering bins, and control
means to permit t~e reserYQir to become charged with
inert gas prior to the discharge o coal from the
metering bins, and to release said gas charge into the
metering bins consequent upon the discharge of coal
therefrom.
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Preferably, the system includes means for
permitting the trans~er of inert gas from the metering
bins to the storage bun~ers during the transfer of
coal from the storage bunkers to the metering ~ins.
Throughout this speclfication the term
"inert gas" is to be construed as including also any
lnert vapour such as steam.
An embodi.ment of the invention will now be
described, by way of example only with reference to
the accompanying schematic dra~ing of a system for
supplying pre-heated coal to a coking oven battery.
The system comprises a coal pre-heating
plant 10 fired by a furnace 12 and arranged to
discharge, via a conveying chute 14, into the first of
a series of conveying sections 16, 17, 18, 19. The
coal is transferred from the final conveying section
19 into a series of storage bunkers 20, therebeing a
control gate 21 associated with each bunker except for
the final bunker in the line 9 thus to ensure
substantially uniorm supply. As required, the coal
is discharged from the bunkers into a series of
metering bins 22 via lines 23, whereby metered
quantities of coal can then be charged into the
individual ovens of the coking o~en ba~tery 24.
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An inert gas reservoir 25 supplies inert gas,
for example, nitrogen, via a heater 26 and pressure
regulators 27 and 28, to a line 29 connected ~ia a
shut-off valve 30 to the coal input end of the
conveying section 16, 17, 18, 19. The inert gas, thus
introduced, occupics the ~hole conveying section and is
passed into the storage bunkers 20. Gas ducts 31 are
provided between the conveyor 19 and all but the final
bunker in the line thus to permit the free passage of
gas into the bunkers independently of the flow of coal.
Further gas ducts 32 connect the top of each
bun~er to a gas escape duct 33 including a shut-off
valve 34. A gas analyser 35 is connected to the duct
33 for a purpose to be described,
Also supplied with inert gas from reservoir
25 is a duct 36 connected via a shut-off valve 37 to a
second gas reservoir 38. Outlet ducts 39~ each
containing a shut~off valve 40, connect the reservoir
38 to the metering bins 22 via a series of ducts 41
each of which connects one of the metering bins 22 to
an associated one of the storage bunkers 20.
In the operation of the system iner~ gas is
initially fed from the reservoir 25 via line 29 to ~he
conveyor section 16, l7, 18~ 19. Thus valves 30 and
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34 are open and the oxygen in the system is purged
via line 33 to atmosphere and replaced by the ine~t
gas. ~len the gas anal~ser 35 indicates a sufficiently
reduced quantit~ of oxygen in the system valves 30
and 34 are closed and the interior of the system
remains inert. Whilst coal is being delivered from
the storage bunkers 20 to the metering bins 22, valve
37 is opened so that reservoir 38 becomes charged with
inert gas. At the requisite gas pressure valve 37 is
closed.
When the metering bins 22 discharge their
contents into the oven chamber, valves 40 are opened
to permit the gas charge in the reservoir 38 to be
released into the meterillg bins 22 to replace the gas
evaçuated with the coal charge. Thereafter, the
valves 40 are closed, valve 37 opens once again and
the reservoir 38 is recharged with inert gas in
readiness for the next discharge of coal.
Whilst coal descends into the metering bins
22 from the bunkers 20 the inert gas in the metering
bins is forced upwardly through ducts 41 into the
upper end o bunkers 20 to replace the gas which has
been evacuated along with the coal. In this way the
interior of the system remains inert and is topped up
whenever the inert gas quantity is reduced by lf
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evacuation along ~Yith the coal. If necessary a
pressure sensor can be provided and adapted to open
valve 30 thus to inject urther gas into the system
should the pressure therein fall below an acceptable
limit. In addition another gas analyser could be
included in the conveying system and adapted to open
valve 30 to inject further gas into the system should
the oxygen level therein rise above an acceptable limit.
It will be appreciated that the intermittent
supply of inert gas ensures a considera~le reduction
in operating costs when compared with systems in which
the inert medium is supplied continuously. It may be
advantageous for the valves 40 to be variable whereby
the rate at which the inert gas flows into the metering
bins 22 can be selected according to the rate a~ which
the pre-heated coal discharges therefrom. Thus the
gaseous atmosphere inside the bunkers and conveyors
can be maintained substantially constant.
