The major operation in mines and quarries, up to and including primary crushing, can be split into drilling, blasting, loading, hauling and finally the primary crushing itself. Within these operations the blasted material is usually transported by dump trucks to the primary crushing stations, which traditionally are stationary plants. Looking back, it has become obvious that often companies have set up the plants at a more or less good starting position not thinking about the further development in the future. In a lot of cases the pit extended itself far away from the preparation plants and more and more haulage needs to be done. This is one of the most important points to be mentioned, because depending on the haulage distance and operational cost structures within the mine or quarry, only the haulage costs themselves represent 30 to 60 percent of the whole operational costs. Therefore in countries with high fuel prices the most interested companies for mobile or semi-mobile technology can be found.
The key to cost reduction and lower haulage cost in mining industry is an in pit crushing and conveying system (IPCC), a combination of track mounted mobile or semi-mobile crusher, with mobile and fixed conveyor belts. Below are the main advantages of IPCC systems to improve mining operations:
- One way to reduce the explosion of haulage costs is to use conveyor belts. The combination of mobile and fixed conveying can save up to 2/3 of the existing haulage costs.
The use of dump trucks is in fact often very inefficient. Some of the largest dump trucks use over 50 percent of the energy to move themselves in spite of hauling blasted material.
- Contrary to the reduction of the haulage capacity of dump trucks, the transport distance does not affect the capacity of conveyor belts. The capacity of conveyor belts is limited by the belt drive speed, belt width and form. As shown belt drives are much more economical than dump trucks and they are not limited by haulage distance. In addition to this, the haulage distance limits the transport ratio of a dump truck. The further you need to transport the material, the less efficient it is to use a dump truck.
- Belt conveyors save a lot of money in comparison to dump truck haulage. Belt conveyors are much cheaper to maintain, because they contain far fewer parts and they also don’t use as many spare parts, e.g. tires, as dump trucks
- Moreover fast driving dump trucks are always a risk for operators and the technical surrounding. Besides increased safety, less traffic also means that less dust is produced. Therefore the watering of haul roads can also be reduced (a typical mine needs 2-4 litres per m2 per day of water for haul roads). As an example a mining operator reports that his new 2-mile-long conveyor eliminates more than 140.000 cycles, which means 570.000 vehicle miles on an annual basis are no longer needed. Conveyors require only about 20% of the energy needed by heavy-duty trucks. As a matter of fact, this does not only reduce fuel consumption and labour costs but also reduces estimated production of PM- 10 emissions by mobile haulage from 95 kg/d to 3 kg /d.
- One great advantage is the lower stripping ratio; Lower stripping ratios mean that less money has to be spent on mining overburden or waste material and transporting it around. Normal, main haul roads need to be a minimum width of the dump trucks. In addition to this they must be “shallow” with a maximum in- or decline of about 10%. As a result the whole pit must be wider at the surface, in order to provide the trucks the safety required to navigate down to the working site. Belt conveyors need less broad roads and therefore allow for steeper pit wall angels and are then furthermore able to offer lower stripping ratios.