Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Physicochemical Problems of Mineral Processing

2 2016

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

First-order and second-order breakage rate of coarse particles in ball mill grinding

Barani K., Balochi H.

Physicochemical Problems of Mineral Processing

2016

Vol. 52, iss. 1

268--278

It has been observed by many authors that the breakage rates of coarse particles in a ball mill slow down with increasing grinding time and deviate from the first order. In this paper it is intended to find out whether the breakage rates of coarse particles obey second-order kinetics or not. For this purpose, quartz, limestone, iron ore and a mixture of quartz/limestone (weight ratio of 1:1) were selected as a ball mill feed. The first-order breakage rate was determined for the four particle sizes of quartz, limestone, iron ore and the mixture of quartz/limestone. Results indicating good first-order kinetics were obtained with the fine-sized particles (-1.2+1 mm, -0.6+0.42 mm). However, the coarse-sized particles (-5+4 mm, -3.15+2.5 mm) showed deviations from the first order. These coarse particles were in the abnormal breakage region. The second-order breakage rate was determined for the coarse particles (-5+4 mm, -3.15+2.5 mm). It can be seen that, for both sizes and all the materials, the second-order plot had better fit than the first-order plot. Also, it can be concluded that the second-order kinetics could model the breakage of coarse particles better than the first-order kinetics, and the validity of the second-order breakage rate was increased with increasing particle size. However, it is suggested to examine the validity of the second-order breakage rate kinetics for other materials and particle sizes.

Comparative study on the effect of using conventional and high pressure grinding rolls crushing on the ball mill grinding kinetics of an iron ore

Barani K., Balochi H.

Physicochemical Problems of Mineral Processing

2016

Vol. 52, iss. 2

920--931

The effect of using conventional and high pressure grinding rolls (HPGR) crushing on the ball mill grinding of an iron ore was assessed to determine how these different comminution processes affect the ball mill grinding kinetic. For this purpose, the sample was obtained from the Jalalabad Iron Ore Mine and crushed by conventional crusher and HPGR. Then, the crushing products were ground in a laboratory ball mill. Five single-sized fractions of (–4+3.15 mm), (–2+1.7 mm), (–1+0.850 mm), (–0.500+0.420 mm), and (–0.212+0.180 mm) were selected as the ball mill feed. The specific rates of breakage (Si) and cumulative breakage distribution function (Bi,j) values were determined for those size fractions. It was found that for all fraction the Bi,1 values of the HPGR product were higher than those for the crusher product. It means that the particles produced by the dry ball milling of the HPGR product were finer than by the crusher. Also, the results showed that the specific breakage rate of the material crushed by HPGR at coarse fractions (–4+3.15 mm, -2+1.7 mm, and -1+0.850 mm) was higher than the material crushed by conventional crushers. However, at fine fractions (–0.500+0.420 mm and -0.212+0.180 mm), there was a small difference and the specific breakage rates were the same. This issue can be explained by the fact, that for coarse fractions the particles had longer side surfaces and thus were more affected by the lateral pressure. The results of verification test showed that after 60 seconds of grinding the 80% passing size of the HPGR and crusher products (D80) were reduced from 3311 μm to 760 μm and 1267 μm, respectively.