Settling characteristics of coal washery tailings using synthetic polyelectrolytes with fine magnetite

Abstract

The study examines the potential reuse of waste water from coal preparation plant tailings, which are often problematic in terms of solid liquid separation and dewatering. The settling rate of fine coal particles by interaction with proper coagulants and flocculants is important in the dewatering process. The tailings water from the Kedla coking coal preparation plant, Central Coalfield Limited (CCL), India is highly turbid with a negative surface charge dominating at pH values between 2 and 10. A polymeric flocculant in conjunction with fine magnetite was used to achieve a faster settling rate with the lowest level of water turbidity. The conditions affecting the interaction between the reagents and the turbid particles present in the tailings water are investigated. it was possible to reduce the turbidity of the water to 73 NTU from a very high turbid tailing water by using 1.2 mg/l of the polymer with 0.1 g/l of fine magnetite at the natural pH of the tailing slurry. The finely divided positively charged magnetite particles, when combined with the flocculent, coat the negatively charged impurities in the water, which results in a faster settling rate under the influence of a magnetic field.