A kinetic model for batch coal flotation

Abstract

Experiments were carried out in a batch flotation cell using four coals at different levels of variables. From the results of these experiments, it is verified that the recoveries of non-ash and ash material from any size fraction follow first order kinetics given by the equation: R = R −8(1 − e − kt ) It has been found in the present investigation that the rate constant ‘k’ for any size fraction is dependent not only on the average size of the size fraction, but also on the proportion of ash and non-ash fractions within that size range and in the fines below 75 micron in the feed. When logarithm of rate constant for the recovery of non-ash material i.e. k N of any size range is plotted against a parameter X N which is defined as average size weight fraction weight fraction X N of that size × of non-ash × of non-ash range material in that material in the size fraction 75 micron Straight lines with constant slope have been obtained. Based on this observation, the influence of material characteristics and the process variables on the rate constant has been separately quantified. The equilibrium recovery of non-ash material from any size fraction has been related to the average size(d) by an equation R N = 100 e −ab b The constant ‘b’ has been found to be dependent on the type of coal and the constant ‘a’ has been related to the levels of process variables. Similar observations have been noted with the recovery of ash material also from each size range in the feed. Thus knowing the rate constants and equilibrium recoveries of non-ash and ash material, the recoveries of non-ash and ash material have been predicted at different flotation periods. These values have been used along with size and size-ash analyses of the feed to estimate the yield and ash content of the clean coal product. The model developed has been verified with additional two more coals and the prediction of yield and ash content of concentrate using the model has been found to be highly satisfactory.