Environmental Aspects of Phosphate and Potash Mining United ...

More documents

Recommendations

Info

Overview of Phosphate Rock and Potash Mining and Beneficiation 12 Figure 2.2 Common potash mining processes and equipment Extraction Handling Underground Solution Surface Beneficiation / concentration Size reduction Desliming Concentration Dewatering Drying Compaction Granulation Storage Continuous mining machine Longwall Load-haul-dump (LHD) units Drill and blast Injection wells Recovery wells Evaporation ponds Shuttle cars Conveyors Feed bins Shaft or decline haulage Brine pipelines Cooling ponds Crushing Grinding Screening Hydrocyclones Attrition scrubbing Hydrocyclones Flotation Thermal dissolution- -crystallization Electrostatic separation Heavy-media separation Filters Thickeners Centrifuges Rotary ovens Fluidised bed dryers Rotary compactor Granulator Conveyors Sheds Although it is not strictly mining, the concentration of brine in solar evaporation ponds is another method of producing potash ore. The method relies on the evaporation of brine through a series of shallow ponds. The initial ponds are used to precipitate halite (NaCl) and concentrate the desired minerals, the brine is then pumped into a second series of ponds in which the potash ore, mostly carnallite, is precipitated. The carnallite is harvested and pumped as a slurry to beneficiation facilities for processing. Potash Beneficiation The processing of potash generally involves a series of steps including: Size reduction; Desliming; Separation; Drying; Compaction and granulation; Disposal of the waste streams. The specific process employed will depend on factors such as the characteristics and constituents of the potash ore and the market specifications. Generally, the ore is reduced in size using a system of crushing and grinding to liberate the different minerals from each other. This is usually followed by desliming by intense agitation followed by flotation or hydrocyclones to separate the fines consisting of clays, dolomite and sand from the potash ore. Four basic techniques are used to separate the waste minerals or by-products such as salt and concentrate the potash; flotation, electrostatic separation, thermal dissolution-crystallization, and heavy media separation. Several of these may be used together to enhance recovery. Flotation is the most widely used technique, relying on the difference in surface properties between minerals to selectively float the desired mineral. Electrostatic separation is a dry process in which the minerals are separated using their different electrical conductivities. Thermal dissolution-crystallization relies on the same principle as solution mining, whereby a heated brine preferentially dissolves potassium chloride. Heavy media separation relies on the difference in specific gravity between sylvite and halite to selectively float and remove the lighter sylvite particles.
Environmental Aspects of Phosphate and Potash Mining After concentration, the potash concentrate is generally dried in a rotary or fluidized bed dryer to reduce the moisture content. Depending on market requirements, this may be followed by compaction at high pressure between rollers and then granulation to produce a uniform size potash product. Three major waste streams are produced during beneficiation; brines, fines, and salt tailings. A variety of disposal methods are currently used, including: Stacking of the salt tailings on the surface; Retention of the fines and brines in surface ponds for solar evaporation; Deep well injection of brines into confined permeable geological strata; Backfilling of mined underground openings with salt tailings, fines and brines; Release of wastes to water bodies such as rivers or seas. Filtering potash before drying - Kali und Salz GmbH, Germany These are discussed in greater detail in Chapter three. Figure 2.3 Typical potash beneficiation process Kali and Salz GmbH, Germany Mine Primary crushing Fine grinding Flotation Hot leaching Potash rotary drier - Potash Corporation of Saskatchewan (PCS), Canada Classification Crystallization Drying Washing process Granulation Drying Dustfree Granular KCl 99 Storage / shipment Storage / shipment Potash compaction rollers - Potash Corporation of Saskatchewan (PCS), Canada
Page 1: Environmental Aspects of Phosphate
Page 4 and 5: Acknowledgements A number of people
Page 6 and 7: Preface This report on the environm
Page 8 and 9: Introduction 2 During recent decade
Page 10 and 11: Introduction 4 Figure1.2 The minera
Page 12 and 13: Overview of Phosphate Rock and Pota
Page 20 and 21: Beneficiation Handling Extraction d
Page 22 and 23: The Environmental Approach of the P
Page 28 and 29: Handling The Environmental Approach
Page 30 and 31: Beneficiation The Environmental App
Page 42 and 43: Closure The Environmental Approach
Page 44 and 45: Rehabilitation The Environmental Ap
Page 56 and 57: Emerging Environmental Issues and T
Page 58 and 59: Appendices Appendix B. Illustrated
Page 60 and 61: Appendices Appendix C. Australian M
Page 62 and 63: Appendices Appendix D. Glossary of
Page 64 and 65: Appendices Appendix E. Acronyms Acr
Page 66 and 67: Appendices 60 14000 Environmental M
Page 68:
www.unep.org United Nations Environ
show all

Environmental Aspects of Phosphate and Potash Mining United ...

Create successful ePaper yourself

Delete template?

Save as template?