USE OF IMPACT CRUSHING FOR THE ENRICHMENT OF LOW-GRADE COLEMANITE CONCENTRATES

摘要

This paper presents the results of an investigation into the enrichment of -25+3 mm low graderncolemanite concentrates exploiting differential breakage properties of various minerals associatedrnwithin the ore sample. Boric acid production process requires concentrates containing at least 42 perrncent B_2O_3, hence concentrates below this grade either stock piled or further treated to increase B_2O_3rncontent. The low grade concentrate is obtained as a by-product of Emet Colemanite Concentratorrnand the B_2O_3 content may vary around 37 - 38 per cent. The sample used in the experimentalrnstudies assays 37.52 per cent B_2O_3. In the experimental procedures the sample was crushed using arnlaboratory size horizontal shaft impact crusher and the products were classified into different sizernfractions by screening so that any improvement by size could be observed. In the tests the effectsrnof parameters such as the revolution speed of the crusher and heat treatment was checked. Testrnresults prove that boron contents show a tendency to increase as the particle size decreases. As arnresult of the experimental studies a colemanite concentrate assaying 42.13 per cent B_2O_3 is producedrnwith 76.55 per cent recovery. Arsenic content is seen to change inversely proportional with the B_2O_3rncontent of the concentrate such that it drops from 1016 ppm from the as received sample to 676 ppmrnin the concentrate.