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July, 1932
Pneumatic Cleaning of Coal at Ryhope Colliery
A Birtley Coal-Cleaning Plant has recently been erected by the Ryhope Coal Co. Ltd., Co. Durham.
The Ryhope Coal Co. Ltd. have recently initiated an extensive modernisation programme, which includes the erection of new winders and headgears and a general electrification of the power services. This work is now being actively pursued, and will be completed about the end of the year. As a first measure, however, attention was given to the preparation of the coal, and a Birtley pneumatic separator plant was given priority in the entire reorganisation schedule. This equipment is now in active commission, and through the kind offices of Mr. Geo. Hindson, Agent to the Ryhope Coal Co. Ltd., we were privileged to inspect it.
As arranged at present the plant has a capacity of 60 tons of raw coal per hour, 3/8 in. to zero, but provision has been made for an additional separating unit — making three in all — to be incorporated at a later date to bring up the capacity to 100 tons per hour of 1-in, to zero coal. The conveyors and elevators were installed initially to handle this larger throughput, so that, apart from extending the belt conveyors to collect the product from the third separator, no modifications to the handling equipment will be necessary.
The 3/8-in. to zero raw coal is carried from the colliery screening plant by an existing belt conveyor, which has been extended, as shown in Fig. 6, to discharge into a ground hopper. It is then elevated into the plant by the main elevator. This, as has already been stated, has a capacity of 100 tons per hour. It is of the continuous bucket type, and the casing is built up from rolled-steel sections of mild-steel plates, so that the loaded and return strands each work in separate totally enclosed trunks, which are braced at intervals by means of cast-iron distance pieces.
The elevator discharges on to a pair of Hum-mer screens, the oversize passing on to one mild-steel storage hopper and the undersize to another. From the hoppers the coal is fed direct to the separating tables. These are illustrated in Figs. 4 and 7, the former showing the unit treating the 3/8 to 1/8-in coal and the latter the 1/8 to 1/32-in. size. In Fig. 7 the raw coal chute is shown to the top left-hand of the illustration, the aspirator removing the dust below 1/32 in being shown behind. The bulk of the aspirated dust is deposited in a settling chamber, situated just above the point at which our view is cut off, and falls down the two chutes shown on each side of the separator. The coal is thus de-dusted before it is fed to the machine; both the coal and dust discharges are sealed by means of spring-balanced air-sealed doors.
After separation, the cleaned coal is delivered by means of mild-steel chutes to a belt conveyor, on to which is generally added the aspirator dust. This conveyor discharges to a cross conveyor, which returns the cleaned product back to the colliery screening plant. "Middlings" from both separators are fed on to another belt conveyor and returned to the main elevator for re-circulation. The shale is delivered to a space bucket elevator by means of a belt conveyor, and is discharged to the existing stone gantry in the screening plant.
As will be seen from the illustrations, both the separators are totally enclosed in mild-steel hoods and connected up to the main suction range, which also carries the airborne dust, which is deposited in the aspirator settling chamber. The dust-laden air is taken to the Waring filter, constructed in reinforced concrete, shown in the title block. The whole of the air is filtered through canvas bags, perfectly clean air being discharged into the atmosphere. Connections are also made from the suction range to the fine-coal bunker. An efficient dust-collecting plant was especially important in the present case, because the raw coal feed is absolutely dry and contains a high percentage of very fine dust.
The whole of the electrical equipment is operated through a contactor controlled by a push-button panel situated upon the operating floor of the cleaning plant. This contactor panel is so arranged with interlocks that when the main start-button is pressed the whole of the plant starts up in a manner which brings into operation each of the individual motors in proper sequence automatically. Motors which drive conveyors and machines that are fed from other units are so arranged on the interlocking switch-gear that if, for they cease to any reason, operate, the units which are feeding them, and which if left running might cause serious chokes, or overflows, are automatically cut out at the switch panel and come to rest. In shutting the plant down, all that is necessary is to press the main stop-button, which brings out the whole of the switches. This arrangement of the electrical gear prevents any serious delays due to chokes, and spillages are avoided.
Drawings and Photographs accompanying the article
Article reproduced from a copy of the magazine held at National Mining Museum Scotland, Newtongrange, Midlothian.
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