To fix a principal crushing plant that has been excavated and built underground is complicated and costly; therefore, careful planning pays good dividends. This paper looks at different aspects of plant design including capacity, installation, layout, maintenance and safety.
This paper concentrates on hard rock applications, however, a few of the findings will apply and also to crushing softer minerals using other than compression crushers, for instance, impact crushers, sizes, etc.
Real estate in an underground mine is usually with a prime cost; therefore, the design of primary crushing plants faces more limitations compared to surface where you could say the sky’s the limit. However, the key crushing and transportation from the ore to come to light tend to be dimensioned so that they define the capacity of the mine; whatever limits the functionality with the plant may limit the output of the mine.
Required capacity defines the dimensions and type of crushing equipment along with the variety of parallel crushers or plants required to meet the mine production rate. Most suppliers and EPCM providers have simulation and calculation tools for that basic equipment and capacity selection, however, especially underground, the choices criteria gets wider, usually in the direction of securing production capacity having a larger safety margin.
Jaw crushers would be the most typical solution if the throughput is less than 1000 tonnes hourly, depending somewhat on the scalping solutions, which is discussed later. Above 1000 tph, primary gyratory crushers begin to look interesting; there aren’t any exact boundaries but above 2000 tph, jaw crushers get rare except in the parallel plant layout. Generally jaw crushers are in the clear majority in underground crushing.
Capacity depends also around the feed size and material type unveiled in the flower and required product curve. Typically, the first stage of crushing really has two functions:
To get the material small enough for transporting out of the mine To get a suitable product curve for an additional stage of combination
In any case, the top size of the information eventually ends up typically in the range of 300 ?¡ìC 350 mm, which is great for belt conveyors and fits into most secondary crushers without causing process risks, to make this happen top size, the Construction Waste Crusher setting is within the array of 200 mm or below, according to rock characteristics. The belt may be the way of transporting the crushed ore out of the mine but even when it’s not, there is certainly usually a conveyor somewhere within the materials handling process, so the requirements have to be met.
You will find mines where multiple stage of crushing takes place underground but mostly the lower cost and flexibility of surface construction result in only primary crushing being carried out underground.
Most underground mining methods produce a feed that’s finer compared to a normal open pit mine, leading to higher capacity through-plant; however, surprises do happen where there has to be a method to handle oversize feed material when the requirement occurs.
Planning the crushing plant for maintenance is an important part of achieving high process reliability and availability. Lifting requirements for the major components has been discussed above nevertheless it should also be noted that the routine maintenance includes lifting wear and spare parts, well located jib cranes or monorails will be the answer. In large crushers, perhaps the tools necessary for opening or tightening bolts can get bulky and benefit from creating a lifting device handy