MODERN MINING PROCESSES
Having identified an area of anthracite reserves, an efficient blasting process is carefully planned out in order to fracture the rock so that it can be excavated.
Overburden (rock lying above the anthracite) is removed at a ratio of 18:1 (cubic yards of overburden: tons of clean coal) using large hydraulic excavators, and taken away by 100 tons capacity dump trucks.
Smaller excavators then remove the anthracite carefully to reduce the amount of rock carried to the washing plant.
Run of Mine anthracite enters the washing plant to be ‘cleaned’ of rock and other non-anthracite material and is then sorted into a range of sized anthracite products suitable for market. ROM anthracite is fed into a hopper from the ROM storage bay using a Front End Loader. Large rock is removed from the plant feed before being conveyed to a fixed grizzly screen and jaw crusher station that sizes the anthracite to 4” top size before feeding to the preparation plant.
The anthracite product is sorted into 8 standard sizes. Coarse refuse is collected on a belt conveyor and discharged to ground storage pile while fine refuse from the clarifier is collected in a sump and pumped to a disposal pond.
Concurrent mine reclamation is practised at Stockton – as the overburden is removed, it is taken to a disposal area in a previously mined section of the pit. This continual backfilling process ensures all reclamation remains current and maintains the open pit within permitted limits, without having to establish an overburden dump elsewhere.
Excavated overburden “bulks up” to a greater volume than it was in the ground (the “swell” or “bulkage” factor) so the backfilled areas are restored to slightly above original contours even after taking into account removal of the anthracite. The reclamation is completed by seeding with grass and planting trees.