A case study showing the reduction of capex and opex by filtering fine and coarse fractions separately

The treatment of tailings is becoming an increasing focus of discussions and decision-making about mining operations. Safety hazards, environmental risks, the huge consumption of fresh water and the cost of mine closure are the main topics discussed. And most, if not all, of the problems could be reduced if the tailings were dry stacked and most of the water was returned to the process. However, this solution requires a significant investment in combination with increased operation costs. The return on investment will come later, with less fresh water being required and far less costs for mine closure. In many cases the tailings dewatering is studied by comparing different technologies for the total tailings stream. Coal and metal ore processing already show how the processing efficiency can be improved if the total plant feed is split into two or three different size fractions and processed separately. This paper will show how capex and opex can be reduced if the same is done with copper tailings using hydrocyclones to split the tailings into coarse and a fine fractions. For the fine fraction, filter presses are used to ensure the target moisture is reached by applying high pressure. The coarse fraction is filtered on high-performance vacuum disc filters, which can be fed directly with the cyclone underflow. This reduces the size of the tailings thickener to the fines fraction only. This paper will present the two flow sheets and the case study will list and compare the items adding up to the total opex and capex for using filter presses only versus a combination of filter presses and high-performance disc filters. The result is savings of > USD 100,000,000 in capex for copper tailings operations with 100,000–200,000 t/d capacity, plus further savings in opex.