|
Although a portion of the field formerly dominated by crushing rolls has been pre-empted by newer machines of other types, there are a number of applications for which the rolls are eminently adapted. There is a gap, for example, between the economical products ranges of the gyratory fine-crusher, on the one hand, send the ball mill or rod mill, on the other, which the rolls fill effectively.
They are used for making granules and grits, and have been successfully applied to the production of manufactured sand for concrete aggregates.
Although rolls never attained any great degree of popularity in the commercial crushed stone industry, a number of sets are being used for low reduction ratio recrushing in stone and gravel plants. In this application they are quite successful. They are also weIl adapted by virtue of their forced-feed action to the handling of soft" and sticky material s, such as rock asphalt, although as has been noted, some materials of this nature wilI cake in the rolls.
It is in the realm of ore dressing that crushing rolls found their greatest field of application, and, although a portion of this field has been taken over by the modern high-speed gyratory crusher, and some of it eliminated by changing methods in concentration practice, a large number of rolls are stilI in active service in ore dressing milIs throughout the world.
Some experienced operators favor them in preference to any other type of crusher for the final crushing stage ahead of fine-grinding ball milIs, as one example. They are also used in many milIs to prepare the ore for coarse concentration, prior to further grinding for flotation or other recovery processes. Crushing rolls require a certain amount of skilI and experience to obtain the best and most economical performance from them, and the mining man has learned through his years of experience how to operate them and care for them.
|
