Environmental Aspects of Phosphate and Potash Mining

Environmental Aspects of Phosphate and Potash MiningBeneficiation plants frequently implement measuresto contain and recover process spillages, in order tominimize environmental effects and product loss.Water ConsumptionBeneficiation operations generally consume largequantities of fresh water for processes such as washingand flotation. The water is usually sourced from nearbysurface and ground water supplies. In arid areas,local water supplies may be limited, requiring water tobe piped considerable distances.Water piped in from distant sources may provide asuitable source for other users.Provision of Water Resources to Other UsersIn New Mexico, the Mississippi Chemical Corporationpipes water from a distant freshwater aquifer to theirCarlsbad potash operation. Local groundwater in thevicinity of the operation is high in total dissolvedsolids and not suitable for human or livestock consumption.The freshwater pipeline has provided awater source available for local ranchers, reducingreliance on variable rainfall in this arid area.Electrostatic Separation and Pneumatic Flotationfor Potash OreThe Kali und Salz GmbH operation in Germany hasdeveloped the ESTA electrostatic separation processand the pneumatic flotation cell to improve the recoveryof potash from complex mineralized ores.Implementation of these techniques has also createdadditional environmental benefits through reducedenergy consumption and waste water production.The ESTA electrostatic separation process requiresthat complex potassium/magnesium ores are dryground to less than 1 millimetre to separate the differentminerals. The particles are conditioned tocreate differential positive and negative chargesbetween them. Separation occurs as the mineral particlesare subject to a 125,000-volt potential dropduring free fall. A multi stage separation processallows the various product and waste minerals to beisolated and concentrated. Environmental and economicbenefits arise from the dry separation processthat produces no waste brines and the relatively lowenergy requirements.A non-mechanical, pneumatic flotation cell has beendeveloped for the separation of kieserite (magnesiumsulphate) from halite. In comparison to conventionalmechanical flotation cells the pneumatic cells consumeless energy and recover more kieserite.Water management is an important aspect of theoperation and is usually integrated with waste disposal.Where possible, recirculation or recovery of thewaste process water/brine is effected. In many casesthe process waters/brines are used to transport thewastes as a slurry to the disposal areas. Typically, theyare recovered for reuse, minimizing the need for additionalfresh water input.Where fresh water sources are not available for phosphaterock beneficiation, salt water has been used forprocessing. A clean water wash is required afterwards,to reduce the chloride content of the ore concentrate.Utilizing dry beneficiation processes reduces waterconsumption. However, it can create additional dustproblems.Water ContaminationContamination of surface and ground water mayoccur from the spillage of process water, brines, oreconcentrates, wastes or chemical reagents during processing.A variety of methods to contain spills areused, including drains, bunds around storage and processingtanks and dams for major process spills.Pneumatic flotation cell - Kali und Salz GmbH,GermanyThese allow spills to be recovered and returned to theprocess or be disposed of safely.Air ContaminationDry processing operations may generate significantquantities of dust during operations such as crushing,grinding, compaction and drying. This can be controlledto some extent through the use of emissioncontrol equipment such as baghouses and wet scrubbers.