Stone that passes into the dryer is heated to 100ºc, which removes the moisture from the stone and kills bacteria this will help to screen a cleaner product.
From the dryer material is fed into one of three mills, each of which is fitted with a magnet to remove any foreign metal should the problem ever occur. Stone is then ground down to <5 mm and then passes over one of two sets of screens and is graded into four products - Grit, Gran, Flour & Ground Limestone.
The graded products are then stored in 180 tonne capacity bins, except the Ground Limestone, which goes to a storage shed ready for delivery.
Castle Hill Quarry limestone products are produced from a particularly pure form of Carboniferous Limestone containing 98.63% Calcium Carbonate.
The production of Agricultural Limestone involves at least seven processes. This starts with the excavation of the virgin rock from the face using an excavator fitted with either a hydraulic hammer or ripping tool.
This method of extraction stops the stone from being contaminated by soil and explosive residues.
The dug rock is then loaded into a dumper which takes the stone to the crusher, where it is tipped into the feed hopper. The stone passes over a screen to remove all material less than 50 mm, the larger pieces pass into the crusher where it is broken down to less than 100 mm.
Crushed stone passes over another screen and is sorted into two materials 50/100 mm Course Aggregate and DOT Type 1.
The former goes to a stockpile and the later either into the dryer, or to the chipping plant where it is graded by more screens into seven products which are then stored in hoppers. These can be drawn into the dryer at any time or taken to external stocks.
The Limestone Dust is taken from the hopper to the storage area ready for delivery. Additionally 50/40 mm Chippings are taken from the storage bins and feed into another mill that produces Limestone Dust.
