Manufacturing Process

ROM coal hoppers in the pre washery circuit. Shall receive ROM coal of size (-) 100 mm from surface miner. The hopper shall be provided with a Grizzly feeder. The grizzly feeder reclaims the feed coal from the respective hopper and discharges on to a reclaim conveyor which in turn discharges the same on to another conveyor through a transfer conveyor. The Oversize coal (-)100+50mm from the primary sizing screen gets fed to a toothed double roll crusher to get the coal crushed to (-)50 mm. The crushed coal (-50mm) from the toothed double roll crusher along with the primary sizing screen undersize (-) 50 mm then fed to the secondary sizing screen through a common feed conveyor.

The undersize coal (-)6mm from the secondary sizing screen gets fed to the fines hopper to which a hydraulic gate will be provided to extract the fine coal for further use by SCL. Similarly, the oversize (-)50+6mm from secondary sizing screen gets fed to the Raw Coal Hoppers through a Transfer conveyor and a reversible shuttle conveyor.A provision will be given to feed the total (-) 50 mm coal to the washery incase the (-)6 mm fraction is less than 15%.

The (–) 50+6 mm coal will be reclaimed from the sized coal hoppers through Vibro-Feeders and washery feed conveyor. The reclaimed sized coal will then be fed to a Sieve Bend followed by Vibrating De-sliming Screen together with pulping water. This screen separates out the undersize material (-) 2 mm, if any, which is gravity, fed to the fines sump for further processing. To enhance the separation extensive use is made of spray-water.

The Desliming Screen oversize material reports to Heavy Media Cyclone via a wing tank. Before entering this tank the coal is mixed with correct media (a mixture of Magnetite and water). The coal and media mixture is pumped to the HM Cyclone at a prescribed pressure. The overflow media from the wing tank will gravitate to the Correct Media Recirculation Tank.

The HM cyclone underflow is the reject material that reports to a dedicated Static Sieve Bend. The Sieve Bend underflow, mainly media, will gravitate to the Correct Media Recirculation Tank. The Sieve Bend overflow will report to the Reject Coal Drain and Rinse Screen, the first section of this screen allows most of the media to drain through the screen apertures. This recovered media is still of near correct density and is gravity fed through a media splitter box, under normal operating conditions, most of the media reports directly back to the media recirculation tank. Some of the media can be routed to the dilute media tank, this typically occurs when the coal quality changes that is at increased ash content and there is a requirement to quickly increase the correct media density.

Once the coal passes across the drain section it enters the rinse section, both spray-water and shower box water is used to clean the coal and maximize media recovery. The media and water that passes through the screen aperture reports directly to the dilute media tank, a pump delivers the mixture to the wet Low Intensity Magnetic Separator (LIMS). The barren stream of LIMS reports, by gravity, to a distribution box, which in turn supplies the Clean and Reject Coal Drain and Rinse (D&R) screen and desliming screen with flood-box water. Concentrated media from the LIMS is extracted and gravity fed directly to the media recirculation tank. Finally, the washed reject coal from the reject coal D&R screen is discharged on to the Reject Coal Conveyor.

The HM cyclone overflow stream reports to a dedicated Static Sieve Panel. The Sieve Panel underflow, mainly media, will gravitate to the Correct Media Recirculation Tank and the overflow will report to the Clean Coal Drain and Rinse Screen, the first section of this screen allows most of the media to drain through the screen apertures. This recovered media reports directly back to the media recirculation tank. Once the coal passes across the drain section it enters the rinse section, both spray-water and shower box water is used to clean the coal and maximize media recovery. The media and water that passes through the screen aperture reports directly to the above said dilute media tank.

After the coal passes across the rinse section it enters the separation section wherein the (-) 25 mm fraction of the coal is separated and gravity fed to the Clean Coal Centrifuge. The cent rate from the centrifuge is gravitating to the Effluent Sump Pump through floor drain. Finally, the washed clean coal from both the centrifuge and clean coal D&R screen overflow is discharged on to the Clean Coal Conveyor.