Ｗｏｒｋ Ｉｎｄｅｘ相当数による石灰石の微粉砕性評価

Abstract

Comminution is the oldest mechanical unit operation for size reduction of solid materials and an important step in many processes where raw materials are converted into intermediate or final products. Limestone is self-sufficient mineral resource in Japan and has been using as a sample for grinding tests.Recently, a demand for fine or ultra-fine particles is increasing in many kinds of industries.The energy efficiency of comminution is very low and the energy required for comminution increases with a decrease in feed or produced particle size. Research and development to find energy-saving comminution processes have been performed. Then, it is necessary to estimate the comminution energy. Bond had proposed Work Index and it is an important factor in designing comminution processes and has been widely used. The measurement procedure of Work Index is closely defined by JIS. In a previous paper, the authors proposed a corresponding Work Index which is proportional to the Work Index. A corresponding Work Index could be estimated by the examination of the zeroorder increasing rate constant of mass fraction less than a evaluating size using an arbitrary ball mill.In this paper, ball mill, vibration mill and planetary mill grinding, compressive crushing of powder bed, and autogenous grinding with a stirred mill were carried out on limestone. The relationships between the corresponding Work Index and the evaluating size (sieving size) were studied.As a result, the corresponding Work Index had the minimum value when the evaluating size was approximately the grain size of limestone in the five kinds of mills.