Crushing, general principles

A number of general principles govern the selection of crushers [Riley, Chem. Proce.ss Eng. (January 1953)]. When the rock contains a predominant amount of material that has a tendency to be cohesive when moist, such as clay, any form of repeated pressure crusher will show a tendency for the fines to pack in the outlet of the crushing zone and prevent free discharge at fine settings. Impact breakers are then... 

Secondary crushing, as has already been pointed out, may be performed in machines of various types, but for such work, the gyratory principle is being generally preferred. 

Once the magnesite rock has been blasted, it is generally loaded onto trucks and transported to the primary crushing operation. Primary crushers are heavy-duty machines and handle dry run of mine feed material as large as 1 m. There are two principle types of primary crushers in operation— gyratory crushers and jaw crushers, with the gyratory type being the most common. 

A most often observed fact of colloid and surface chemistry is that work must be done in order to create a new surface. This law is a basic principle not only valid for liquid interfaces, as shown in Chapter 1, but also for solid bodies work is necessary for grinding and crushing for example. Surface thermodynamics starts from the ftmdamental principles of the general thermodynamics and includes equilibrium and non-equilibrium states. 

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