This paper describes the use of a disc-stack nozzle centrifuge for wet classification of ultra-fine particles of calcium carbonate. The influences of G-force and disc geometry on the performance of the ultra-fine clas...This paper describes the use of a disc-stack nozzle centrifuge for wet classification of ultra-fine particles of calcium carbonate. The influences of G-force and disc geometry on the performance of the ultra-fine classification have been investigated. The results have demonstrated that the efficiency of the classification can be increased by (1) applying a relatively moderate G-force and (2) the use of stud spacer discs in the centrifuge. The increased extraction of the fine particles is related to the formation of the appropriate fluid velocity profile at a lower G-force and a circumferential motion without meridional barriers for the case of the stud spacer discs.展开更多
The core mechanism of comminution could be reduced to the breakage of individual particles that occurs through contact with other particles or with the grinding media, or with the solid walls of the mill. When brittle...The core mechanism of comminution could be reduced to the breakage of individual particles that occurs through contact with other particles or with the grinding media, or with the solid walls of the mill. When brittle particles are loaded in compression or by impact, substantial tensile stresses are induced within the particles. These tensile stresses are responsible for splitting failure of brittle particles. Since many engineering materials have Poissons ratios very close to 0.3, the influence of Poissons ratio on the tensile strength is neglected in many studies. In this paper, the state of stress in a spherical particle due to two diametrically opposed forces is analyzed theoretically. A simple equation for the tensile stress at the centre of the particle is obtained. It is found reasonable to propose this tensile stress at the instant of failure as the tensile strength of the particle. Moreover, this tensile strength is a function of the Poissons ratio of the material. As the state of stress along the z-axis in an irregular specimen tends to be similar to that in a spherical particle compressed diametrically with the same force, this tensile strength has some validity for irregular particles as well. Therefore, it could be used as the tensile strength for brittle particles in general. The effect of Poissons ratio on the ten-sile strength is discussed.展开更多
文摘This paper describes the use of a disc-stack nozzle centrifuge for wet classification of ultra-fine particles of calcium carbonate. The influences of G-force and disc geometry on the performance of the ultra-fine classification have been investigated. The results have demonstrated that the efficiency of the classification can be increased by (1) applying a relatively moderate G-force and (2) the use of stud spacer discs in the centrifuge. The increased extraction of the fine particles is related to the formation of the appropriate fluid velocity profile at a lower G-force and a circumferential motion without meridional barriers for the case of the stud spacer discs.
文摘The core mechanism of comminution could be reduced to the breakage of individual particles that occurs through contact with other particles or with the grinding media, or with the solid walls of the mill. When brittle particles are loaded in compression or by impact, substantial tensile stresses are induced within the particles. These tensile stresses are responsible for splitting failure of brittle particles. Since many engineering materials have Poissons ratios very close to 0.3, the influence of Poissons ratio on the tensile strength is neglected in many studies. In this paper, the state of stress in a spherical particle due to two diametrically opposed forces is analyzed theoretically. A simple equation for the tensile stress at the centre of the particle is obtained. It is found reasonable to propose this tensile stress at the instant of failure as the tensile strength of the particle. Moreover, this tensile strength is a function of the Poissons ratio of the material. As the state of stress along the z-axis in an irregular specimen tends to be similar to that in a spherical particle compressed diametrically with the same force, this tensile strength has some validity for irregular particles as well. Therefore, it could be used as the tensile strength for brittle particles in general. The effect of Poissons ratio on the ten-sile strength is discussed.
