Hernic has 2 underground and one opencast mines. During difficult market conditions, Hernic opted to save its reserves and re-engineer its underground mining operations. This process allows Hernic mines to be safe, competitive and sustainable, once mining commences. The proximity of Hernic’s mining sites to the smelters gives it a competitive edge. The smelters are adjacent to the Morula underground mine and approximately 15 kilometres from its Bokone opencast and underground mines. The original source of Hernic’s ore was the Morula opencast mine. Production from this pit ceased in 2000 resulting in the development of the Morula underground mine. In 2006 the Bokone opencast mine, situated approximately 15 kilometres to the west of the smelter operations, commenced. The development of the Bokone underground mine commenced early 2010 and once operational, it will ensure that Hernic has the capacity to support ferrochrome production over the next 60 years.
Run of mine ore is upgraded through an ore beneficiation plant. The ore is crushed and screened into two size fractions, 120 x 20 mm and -20 mm. The 120 x 20 mm size material is upgraded through heavy media separation while the -20 mm material is milled to -1 mm and then upgraded through a spiral plant. The -1 mm concentrate is fed to the Pelletising and Sintering plants for the production of sintered pellets.
Chrome Recovery Plant (CRP)
The Company introduced new technology in the jigging process of the Chrome Recovery Plant,in this process this section of the plant has the ability to produce 85 000 tons of slag per month.
The Company commissioned the Dense Medium Separation (DMS) Plant in June 2015. The plant is designed to process 120 000 ROM per month.
The plant produces 4 products namely:
fine chip fractions;
coarse chip fractions;
This Plant assists Hernic to produce better quality ore as raw material to the furnaces at a higher yield and lower cost. The quality is also moreconsistent which ease the control on the furnaces.
Hernic believes this will be the competive edge for sustainable furnace production.
Pelletising and Sintering
The natural occurring chromite is very brittle and yields a limited portion of lumpy product. The chromite fines are pelletised and sintered through Outokumpu technology to produce competent pellets of 13 mm in diameter. A mixture is added to the chromite pellets and it is then heated in a steel belt sintering furnace. During this process the pellets are heated to form strong bonds between the chromite grains to yield and agglomerate the material. The sintered pellets are then sized and fed to the furnaces.
Ferrochrome is produced using electric submerged Arc furnaces. The closed furnaces are fed raw materials from various sources including chrome ore, coke, char, coal, quartzite and dolomite via the proportioning system for the production of ferrochrome. The valuable portion of the chromite is converted into a metallic phase. The impurities and higher melting oxides remain in a slag phase.
The furnaces are tapped intermittently. The ferrochrome and slag are separated by means of a skimmer plate. The ferrochrome is tapped into sand moulds where it is left for a few hours to cool down and then removed to the breaking floor. The finished product is crushed and screened to exact customer requirements.
After the slag is cooled down, it is removed to a slag dump from where it is fed into the alloy recovery plant.