stanje i perspektive u rudarstvu i odrţivi razvoj mining present state ...

Rudarstvo 2011 / Mining 2011Table 5. Pellet pressure resistance after 3 days of airing.Class of coarseness, Average pressure resistance value of pellets, kg/pelletmm 1 % cement 3 % cement 5 % cement 7 % cement+ 25 6,03 6,17 13,40 46,43- 25 + 15 3,80 4,27 12,57 29,17- 15 + 7 2,63 3,10 7,87 14,50- 7 + 2 1,10 1,57 4,10 6,50Table 6. Pellet pressure resistance after 7 days of airing.Class of coarseness, Average pressure resistance value of pellets, kg/pelletmm 1 % cement 3 % cement 5 % cement 7 % cement+ 25 7,33 8,76 17,13 55,40- 25 + 15 6,13 6,43 15,30 37,37- 15 + 7 2,50 4,12 8,97 29,37- 7 + 2 1,37 1,57 4,87 15,30Table 7. Pellet pressure resistance after 28 days of airing.Class of coarseness, Average pressure resistance value of pellets, kg/pelletmm 1 % cement 3 % cement 5 % cement 7 % cement+ 25 10,33 16,10 38,30 62,90- 25 + 15 6,83 8,77 21,00 42,43- 15 + 7 5,70 7,93 11,17 37,10- 7 + 2 2,30 3,67 7,85 14,13Generally, the pellet pressure resistance rises with the increase in binding agent mass content and timeof airing.4.2. Testing pellets impact resistanceThe testing of pellets impact resistance was performed by the standard method of dropping the lot ofpellets from 453 m onto the steel 12.5 mm thick plate and by measuring the undersize on the sievewith aperture of 2 mm (Anon, 1956). It was adopted that pellets having less than 10% of 2 mmundersize on the sieve after being dropped 25 times satisfy the impact resistance requirements.Table 8 shows the test results for pellet impact resistance using 1, 3, 5 and 7 % of cement, after 3 daysof airing.Table 9 shows the test results for pellets impact resistance using 1, 3, 5 and 7 % of cement, after 7days of airing.Table 10 shows the test results for pellets impact resistance using 1, 3, 5 and 7 % of cement, after 28days of airing.Table 8. Pellet impact resistance after 3 days of airing.Number of droppings 1 5 10 15 20 251 % cement 1,15 2,30 7,90 17,60 26,20 34,10SM, % 3 % cement 0,40 1,90 3,10 4,20 5,70 6,95-2mm 5 % cement 0,35 1,70 2,70 3,55 4,45 5,357 % cement ----- ----- 0,40 0,60 0,80 1,00673