Storage and Loading Out

Storage of run-of quarry and partially processed limestone is necessary to provide surge capacity between the various processing stages. Storage of fully processed limestone is also required to service despatches, to provide a strategic reserve and to store surplus grades. 

Limestone is stored in elevated silos (bunkers, or bins) and also in stockpiles. Short-term storage, typically sufficient to service one day s production, is often provided in silos, which are filled directly from the processing plant, and are used to load road and rail vehicles. Reserve stocks and surplus quantities of positively screened grades are transported to uncovered stockpiles. 

However, the greatest tonnage of limestone is stored on the ground in uncovered stockpiles. Most stockpiles are fed by an elevated conveyer, resulting in a conical shape. Radial elevated conveyers can service three or four stockpiles, each consisting of a different grade of stone. Alternatively, stone can be transported to the stockpile by dump truck or shovel. 

Limestone may be reclaimed from stockpiles by a variety of mechanisms, including conveyers in tunnels below the stockpile, scraper reclaimers and mobile shovels. 

As many aggregate specifications require specific particle size distributions, processing plants generally screen the stone into single sized fractions with a size ratio of approximately 1.4 (e.g. 20 to 28 mm, 14 to 20 mm and 10 to 14 mm) and store them separately. The fractions are then blended, using sophisticated weighing-out equipment, to meet the size distributions specified by the customers. 

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