PRL operations on Christmas Island commenced in 1990, and in normal times the Company would expect to export approximately 700,000 tonnes of phosphate product a year to Australia, New Zealand, Malaysia, and Indonesia.
The Company uses modern open-cut mining methods with a range of different mining and earth-moving machinery to efficiently recover rock phosphate from the different ore bodies and stockpiles. The phosphate-rich soils are excavated with a hydraulic excavator, and haul trucks move the ore to designated field stockpiles, where mobile field screens remove large limestone rocks and vegetation. The ore is then loaded onto road trains with a front-end loader and hauled to the Run-of-Mine pad located adjacent to the dryers, where it is stockpiled according to grade. The stockpiled ore is then blended to create a product that meets our customer’s specifications, and then dried and crushed.
The fine particles created during this process are collected by a dust extraction system and all the rock and dust is stored temporarily at the dryers in enclosed silos.
Rock and dust phosphate are then transported via conveyor belt system and a covered air slide system respectively, through a number of transfer points to the bulk storage area at the wharf, 3km away. The dust is packed into bags and stacked on pallets, ready to be shipped. The phosphate rock is loaded onto shipping vessels by two cantilever arms fitted with telescopic chutes with dust suppression systems. The arms are swung over the appropriate hatches on the ship, and the rock is poured into the hold, each arm can load 600 tonnes per hour.
PRL’s quality control process starts before the mining operations begin. Drill hole samples of each of the ore bodies are collected and sampled in the laboratory. A comprehensive network of holes is drilled and ore samples are taken along each hole for analysis of the total citric acid soluble P2O5, calcium content, and other elements.
These mine survey analysis results are then used to prepare computerised mine plans that show the characteristics of the phosphate reserves in each location. The mined phosphate is stockpiled separately, with each containing rock phosphate with a different phosphate grade. Separate samples are taken from each stockpile for further analysis.
Each phosphate shipment is prepared specially to meet the customer’s specification. Depending on this specification, the rock phosphate may be taken from one stockpile, or blended from a number of stockpiles, so that the specification is consistently correct. Check samples are taken regularly through the drying and shipping processes to ensure that our customers receive the specification they require.