Among various technical problems related to the operation of densemedia seperation of ores and coals, the most fundamental ones are the viscosity and stability of heavy suspensions and the physical characteristics of the material for suspensions.
The viscosity. of suspensions has been studied by many investigators and it has been established that Einstein's equation is applicable for lower concentrations and Arrhenius' empirical formula for concentrations up to 20-25%. However, the higher concentrations, in which these equations fail to be applied, are used in practice. Moreover, it is to be teken into consideration that the viscosity of suspensions is influenced by the size and shape of suspensoid. particles. It is reported elsewhere that the viscosity is also affected by the specific gravity of particles.
In this report the viscosity of heavy suspensions has been studied critically and the following empirical viscosity equation applicable for higher concentrations has been introduced. η=η_w[1+K{δ-1+p (σ/D) ^k} C+qeⁿ1δ (δ/D) ^n₂ (δ-1+σ/D)nCn] where η=viscosity of suspensions, cp.ηω; =viscosity of water, cp.; C=concentration in volume, %;δspecific gravity of suspensoid particles;σ-=mean diameter of suspensoid particles, μ; D=diameter of the capillary, μ; e=base of Naperian logarithm; and K, p, k, q, n₁, n₂and n=constants. In this equation the variables such as the concentration and the size and the specific gravity of suspensoid particles are involved. From this equation the viscosity of suspensions of any concentration and of suspensoid particles of any size and specific gravity may be calculated. The exception is the viscosity of suspensions of the mixture of two or more materials or of the mixed size particles. The materials used are copper slag, “Sendust”, magnetite, iron sand, etc. and the consistometer used is similar to that of De Vaney and Shelton but with some modifications such as preagitation and temperature control of suspensions.