OPERATION FOCUS
The CM loads a locally made shuttle car from Niva Holding
shearers, and a bottom layer up to 80 cm thick mined using Eickhoff low seam height shearers. However, the seam thicknesses do vary. Where the CM is being used, on average 2.2 m of material is cut, including the small amount of waste interburden, which is generally rock salt( halite) with some thin clay layers.
The geological issues are widespread in the mine, so there are plenty of potential application areas for the machine. It does not have to advance on a flat surface, and a laser is used to follow the direction of the potash based on the mine plan, with the operator monitoring the angle of inclination. The operator usually sits in the cab following the production on screen. He also has a remote control rig for use in unstable areas as well as when the CM is moving from one working area to another, when he can remotely reverse tram the machine. The CM production advance is mainly limited by the maximum tramming distance of the shuttle car with its trailing 660 v cable. The CM itself requires a higher powered cable, at 1,140 v.
IM had travelled to the production area with Igor Novik, the Belaruskali Foreman responsible for the CM project, and asked him about his opinion of the Eickhoff machine:“ Despite the geological problems such as faults in the areas where it has been working, as well as interruptions in production at times due to economics such as falling potash prices, the CM has been working for us now for 3.5 years in a very stable way and we are quite happy with its performance. The machine is very well designed and reliable.”
He added:“ Eickhoff is always there to monitor the machine with us and work out any problems. All issues with spare parts and software have been solved very quickly and so from a service point of view we also hold Eickhoff in high regard. In a wider sense, Belaruskali wants to use the latest technology
and equipment where possible to remain competitive. In addition to advanced mining equipment from Eickhoff we are also fortunate to have the local suppliers for shields, shuttle cars, feeders and other equipment.”
Belaruskali has tested a continuous miner from one of the local suppliers but was not able to achieve the same production with it; and is still trying to make improvements to it.
Processing routes
The potash ores are the main raw material used to produce potash and compound fertilisers and other chemicals. The potash ore generally consists of sylvite( KCl), with waste halite( NaCl) containing inclusions of carnalite, anhydrite, silicate and carbonate( insoluble residue).
The basic method of processing of potash ores by hot leaching with further crystallisation of potash salt from saturated salt brines( halurgical method) began in the 19th century in Strasburg.
The primary methods of potash ore processing are flotation( mechanical method) and hot leaching( chemical method). JSC Belaruskali uses both methods: Production Units 1, 2 and 3 process the potash ore by flotation and Production Unit 4 uses the hot leaching method.
The processing of ore by flotation is based on the different capacity of sylvite and halite surfaces to be moistened with water through the addition of specifically acting chemicals – surfactants – and further formation of the froth containing the valuable component. The production process includes the following stages:
■ Ore crushing and prescreening;
■ Ore milling and presizing;
■ Mechanical and flotation desliming of ore;
■ Sylvite flotation;
■ NaCl leaching from the flotation concentrate;
■ Hydro-thickening and dehydration of tailings;
■ Hydro-sizing and dehydration of concentrate;
■ Concentrate drying;
■ Preparation of chemicals;
■ Granulation of potassium chloride;
■ Granule refining;
■ Finished product loading;
■ Waste stockpiling. The flotation method of ore processing is used to manufacture the reddish-pink standard and granular potassium chloride. The KCl mass fraction in the product is 95-96 %. The recovery of the valuable component when using the flotation method is 85.5-87.2 %.
The hot leaching method of ore processing is based on the physicochemical properties of NaCl-KCl-H 2O system. The main principle of this method is the different temperature-dependent degree of solubility of the mineral components – sylvite and halite: the high solubility of potassium chloride from ore by cycling the solution at 115 ° C and the further crystallisation of the valuable component on cooling.
The production process includes the following stages:
■ Ore crushing and prescreening;
■ Leach heating;
■ Ore dissolution;
■ Filtration of halite tailings;
■ Clarification of saturated leach;
■ Crystallisation of potassium chloride;
■ Thickening and centrifugation of potassium chloride slurry;
■ Potassium chloride drying;
■ Granulation of potassium chloride;
■ Stockpiling, storage and loading;
■ Recycled water cooling;
■ Preparation of chemicals;
■ Waste stockpiling The hot leaching method is used to produce the white fine-crystalline and granular potassium chloride. The coarse crystalline product( if necessary) can be painted reddishpink. The KCl mass fraction in the product is 96- 99 %. The recovery of the valuable component of fertilisers produced when using the hot leaching method is 88-89 %. IM
The final production, in this case NPK fertiliser, is exported globally to over 90 countries
18 International Mining | AUGUST 2017