INFLUENCE OF THE CHEMICAL COMPOSITION OF LIMESTONE ON THE DEVELOPMENT OF MINING WORKS IN QUARRY

There are only a few limestone mines in Bosnia and Herzegovina that provide the mineral raw material for industrial production. As a result, the experience in planning and designing such quarries is lesser than in designing the quarries for construction. Limestone from "Vijenac" deposit is an industrial mineral raw material, which is used for the production of soda (light, heavy and bicarbonate), cement, nitrogen fertilizer named "KAN", and is also used in construction and road construction. The use of limestone as a mineral raw material in industrial production requires more attention to the chemical composition of limestone than to the physical-mechanical characteristics. The paper presents a solution to this problem by creating a block of models of exploitation reserves of limestone, which enables foresight of the chemical composition of limestone, both in each floor partially and during the period of exploitation. The block model was created on the basis of the updated state of works, the projected contour of limestone surface mine and the exploration works' database. The block model uses the following: CaCO3, CaO, SiO2, Al2O3, Fe2O3, bulk density, category of reserves and the purpose of the mineral raw material, i.e. for industry or construction. The block model analysis has determined that the northern part of the mine, from the floor E-612.5 to E-525 meters a.s.l., does not meet industrial requirements in terms of chemical composition of limestone. Therefore, limestone from this part of the surface mine will be used for construction purposes. These quantities of limestone are about 2.6x106 m3. Limestone from the southern part of the surface mine meets the industry requirements. Its quantities are about 8.47x106 m3.

Generating of Electric Energy by a Declined Overburden Conveyor in a Continuous Surface Mine

Exploitation of lignite in continuous surface mines requires removing masses of overburden, which are hauled to a dumpsite. There are some technological arrangements where the overburden is transported several dozen meters down to a spreader operating on a lower located dumping level. Depending on an angle of a declined transportation route, there is a possibility to convert the potential gravitational energy of conveyed down overburden masses into electric energy. To recover the maximum percentage of stored energy, an energy-effective and fully loaded belt conveyor should work in a generator mode. Due to the implementation of such a solution, a lignite continuous surface mine, which is a great electric energy consumer, can obtain the status of an electricity prosumer and reduce its environmental impact, in particular demonstrating significant savings in primary energy consumption. Though lignite surface mining is phasing out in Europe, the recuperative, overburden conveyors for downhill transport match up the targets of sustainable mining, understood as getting the maximum benefits from the exploited natural resources. According to the analyzed case study, an investment into the installation of regenerative inverters for the electric power supply of the declined overburden conveyor would pay off within 3–4 years.