Investigation of ash removal from fine grain coal-water suspension by hydrophobic flocculation using Taguchi (L-16) experimental design

Abstract

In this study, it was aimed to remove ash from fine-grained coal-water suspensions and a series of hydrophobic flocculation experiments were performed using the Taguchi (L-16) experimental design to determine the experimental optimum conditions. Five different controllable process variables such as amount of sodium silicate, suspension pH, amount of waste vegetable oil, flock growth time, and precipitation time, which are effective in hydrophobic flocculation of coal, and four different levels of each variable were investigated. Optimum conditions were determined as amount of sodium silicate 1 mL, pH = 3, amount of waste vegetable oil 4 mL, flock growth time 7 min and precipitation time 1 min. According to the optimization results obtained, the high calorific value (5450 kcal/kg) clean coal with 15.46% ash content and 100% combustible recovery was obtained with 57.52% ash removal. In addition, the contributions of each factor to hydrophobic flocculation of coal were determined with one way variance analysis (ANOVA). The most influential factor was determined as the pH value with a contribution of 61.34%.