SYSTEM FOR SUPPLYING PRE-HEATED COAL TO A COKING OVEN BATTERY

CO/1701 A SYSTEM FOR SUPPLYING PRE-HEATED COAL TO A COING OVEN B ATTEIRY" THIS INVENTION relates to coking ovens and in particular a system for supplying pre-heated coal to a coking oven battery.

Several processes are known for the preheating 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 of 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 procreated coal in order to provide the necessary transition between the continuous operation of the pre-heating and conveying section and the batch operation of the metering and charging sections.

co/17ol For effective and economic operation, the equipment used for conveying, metering and charging the coal is physically separated from the pre-heating equipment, and as a result the hot process gases which are circulated within the pre heatìng section and which are used to pre-heat the coal» are excluded from the conveying, metering and charging equipment.

f iO To reduce the level of oxidation of the preheated coal and to reduce the risk of fire 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 environment 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 inertising medium, blockages may occur in the conveying system due to the increased moisture in the preheated coal caused by condensation from the combustion products as they cool. Suck problems are avoided when using dry nitrogen or any inert gas with a low water vapour content as an C0/1701 inertising medium, but such gases may not be readily available and in any case bave proved costly to supply on a continuous basis.

An object of the present invention is to provide a new and economic method of supplying and controlling an inertìsing medium for the conveying, storage and metering sections of a coal pre-heatìng and coking oven plant.

i0 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 and for transferring same in metered quantities to the coking ovens, and an inert gas source adapted to introduce inert gas to the conveying section and to the storage bunkers, characterised by an inert gas reservoir adapted for connection selectively to the inert gas source or to said metering bins, and control means to permit the reservoir to become charged with inert gas prior to the discharge of coal from the metering bins, and to release said gas charge into the metering bins consequent upon the discharge of coal therefrom.

C0/1701 Preferably, the system includes means for permitting tile transfer of inert gas from the metering bins to the storage bunkers during the transfer of coal from the storage bunkers to the metering bins.

Throughout this specification the term "inert gas" is to be construed as including also any inert vapour such as steam.

An embodiment of the invention will now be described, by way of example only with reference to the accompanying schematic drawing of a system for supplying pre-heated coal to a cokìng oven battery.

The system comprises a coal pre-heating plant I0 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, thus to ensure substantially uniform 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 oven battery 24.

1289 18 - 5 - CO/1701 S i0 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 via a shut-off valve 30 to the coal input end of the conveying section 16, 17, 18, 19. The inert gas, thus introduced, occupies the whole 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 bunker 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 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 In the operation of the system inert gas is :initially fed from the reservoir 25 via line Z9 to the conveyor section 16, 17, 18, 19. Thus valves 30 and iO C0/1701 34 are open and the oxygen in the system is purged via line 33 to atmosphere and replaced by tl e inert gas. en the gas analyser 35 ìndìcates a sufficìently reduced quantity of oxygen in the system valves and 34 are closed and the interior of the system remains ìnert. Whilst coal is being delìvered 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 metering bins 22 to replace the gas evacuated 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 of 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 i i i I I I C0/1701 evacuation along with the coal. If necessary a pressure sensor can be provided and adapted to open valve 30 thus to ìnject further 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 considerable 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 at which the pre-heated coal discharges therefrom. Thus the gaseous atmosphere inside the bunkers and conveyors can be maintained substantially constant.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

i. A system for supplying pre-heated coa! 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 and for transferring same in metered quantities to the coking ovens, and an inert gas source adapted to introduce inert gas to the conveying section and to the storage bunkers, characterised by an inert gas reservoir adapted for connection selectively to the inert gas source or to said metering bins, and control means to permit the reservoir to become charged with inert gas prior to the dischar of coal from the metering bins, and to release said gas charge into the metering bins consequent on the discharge of coal therefrom.

2. A system according to claim I, including means for permitting the transfer of inert gas from the metering bins to the storage bunkers during the transfer of coal from the storage bunkers to the metering bins.

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