THE CRUSHING OF ANTHRACITE WITH AN IMPACTOR-TYPE CRUSHER

Special Research Report SR-8 anthracite industry is facing a steady decline in market for domestic sizes. It is therefore found necessary to crush the domestic sizes to more popular steam sizes. It is a prerequisite for the crushing operation to produce a minimum quantity of low priced buckwheat No. 5 and smaller material. It -is also necessary that the initial and operating expenses of the crusher should be low. The present method of multistage crushing with toothed rolls proves quite expensive. The objective of this investigation is to search for a new tool that can fulfill the requirements stated above. Impact crushers appeared quite promising. Detailed experimental work was, therefore, conducted using Kennedy Van Saun Cuber No. 20 Impactor-Type Crusher. Egg, stove, and nut size samples were tested at a low (5. 9 ± 0. 1 TPH) and high (13. 8 :I: 2. 0 TPH) feed rates, and with rotor speeds of 620, 1090, and 1280 RPM. The products were screen analyzed using round hole screens and plotted on a Rosin and Rammler graph paper. Standard anthracite sizes were determined from the aforesaid curves. An analysis of the results indicated that a low rotor speed of 620 RPM and a low feed rate of 5. 9 ± 0. 1 gave the best results for the crusher tested. Egg size feed is more sensitive to changes in rotor speed, whereas nut size feed is more sensitive to changes in feed rate. In all cases the top size decreased with an increase in rotor speed. An increase in either rotor speed, size of feed, or rate of feed resulted in an increase in power._ consumption.