Investigation of relationship between residence time distribution and size distribution of solid particles in tank leaching modelling

Abstract

In the most important models of continuous tank leaching process, residence time distribution and particle size distribution are considered independently. While the studies by some researchers has shown that particle size distribution affect the residence time in the tank. However, no systematic study has been conducted on this issue yet. In this research, while studying the relationship between particle size and residence time, an empirical method for determining of residence time distribution based on inflow size composition to the agitated tank was presented. The relationship between average size of one size fraction of particles and its residence time was obtained by mean residence time and parameter (the slop of a fitted line to the data of a diagram that its horizontal axis is nondimensional time and its vertical axis is the natural logarithm of the ratio of solid concentration in time t to initial solid concentration). Results showed that with enhancing the particle sizes from -38 micron to the range of +125-150, mean residence time increases from 59.1 to 93 min and decreases from 0.95 to 0.3 .Also using calculated amount of for each particle fraction, residence time distribution function for inflow stream with different size distribution was determined. Furthermore, the effect of changing of parameter on the results of segregated flow model of leaching process was evaluated. Results showed that the decreasing in the from 1 to 0.7 leads to increasing the conversion from 0.71 to 0.78.