Processing
01 Location
02 Mineral Processing method
Location
The mineral processing facility is planned to be located within the industrial zone adjacent to inactive coal pit areas outside of Valjevo.
Why?
First, this approach avoids any use of agricultural land. Instead, approximately 30 hectares of land already used for industry would be re-used for the mineral processing facility.
Second, the by-product of mineral processing (tailings) can be used to backfill nearby inactive coal pits. The processing of sodium borate ore uses no toxic reagents, which means the by-product is non-hazardous and suitable for the remediation and reclamation of inactive coal pit areas. The objective is to return parts of the inactive coal pit area to its pre-mining state, providing the opportunity for revegetation and reforestation.
A similar approach has already been applied to an inactive coal pit area near Ub, which has been redeveloped as the site of a regional sanitary landfill serving multiple municipalities and towns in this part of Serbia, including Valjevo.
Mineral Processing method
Processing of sodium borate ore is non-hazardous and well established, having been used for more than 100 years.
Over time, it has been further improved through technological innovation and the strictest environmental and safety standards, ensuring that mineral processing activities do not impact the surrounding environment and water is recycled.
The processing plant would include the following components:
- receiving stockpile warehouse
- conveyors
- mixing tanks (mixers), where ore is blended with water and sodium carbonate (Na₂CO₃)
- thickeners
- filters and filter presses
- crystallisers to produce the final saleable product
Only hot water and sodium carbonate are used in processing sodium borate ore, and are recycled to ensure maximum operational efficiency and minimal environmental impact.
How Water
Water is used to dissolve minerals from the mined ore. The process water temperature is approximately 93 °C and reused across various cycles of ore processing.
During processing, water is mixed with the ore and then, in a closed-loop system, treated and reused.
Sodium carbonate (Na₂CO₃)
Sodium carbonate is a widely used household and industrial compound. Its applications span everyday applications such as:
- Household detergents and cleaning agents
- Water treatment, for softening and pH regulation
- Food industry, to neutralize pH and preserve food products
Sodium carbonate is not toxic under proper handling conditions. As an alkaline substance, it may cause mild irritation if it comes into contact with skin or eyes, so appropriate precautions are required when handling large quantities. It breaks down naturally and does not leave lasting environmental consequences.
In sodium borate processing, sodium carbonate and hot water are added to the ore to extract boron minerals and manufacture final saleable product.
Processing steps
Processing of sodium borates is relatively simple and similar to a water treatment facility. After arriving from the mine, the ore passes through the following stages:
- Leaching: Ore is dissolved in large industrial tanks using hot water and sodium carbonate (Na₂CO₃). Solubilization occurs at approximately 93 °C, allowing boron minerals to dissolve into the water–sodium-carbonate solution.
- Solid–Liquid Separation: Separation of solids (underflow) from liquids (overflow) occurs in thickeners (large circular tanks), where solids settle to the bottom while the liquid containing dissolved boron minerals remains on top.
- Filtration: The solids are transferred to a filter press to remove remaining solution. The resulting solid is tailings, the by-product of sodium borate processing, which contains no toxic substances.
- Crystallisation (Stage 1): The liquid from the thickeners and filter presses is transferred to a crystalliser, where borate crystals form at approximately 26 °C.
- Crystallisation (Stage 2): These crystals are then mixed at approximately 85 °C with liquid from the filter press. Further crystallisation at approximately 66 °C produces the final saleable product, borax pentahydrate. It is a white powder that is packaged in large industrial bags and shipped to customers in local, regional and international markets.