Characterization of Flocs in Dewatering of Coal Plant Tailings

Abstract

L ignite coal, which has a large share in world coal reserves, must be subjected to coal preparation processes in coal washing plants due to its low calorific value and high ash content. After these processes, the huge amount of tailings is produced from the plants, and they must be dewatered before disposal. For this purpose, flocculation is a widely preferred method for solid-liquid separation of fine coal tailings. In this method, long-chain polymers are used to bind particles together to form bigger particles to settle them easier and faster. Flocculation process is affected by various parameters including solid ratio, pH, temperature, stirring speed and time, molecular weight, chain length, charge, and dosage of flocculant. In the flocculation process, flocs with several physical characteristics such as size, structure, and strength are formed depending on these flocculation conditions. Different floc characteristics are preferred for various processes. For example, strong and high-density flocs are favorable in filtration, but not in sedimentation processes. Therefore, it is extremely important to characterize the flocs to optimize the flocculation processes [1-7]. For this reason, there have been various studies on the investigation of floc size, density, structure, and strength [8-13]. Different techniques were used for the floc strength measurements such as image-based tech-Article History:

Investigation of flocculation properties and floc structure of coal processing plant tailings in the presence of monovalent and divalent ions

“…The coagulation/flocculation experiments were carried out with the coal tailing sample at 5% solids ratio (w/v) at room temperature (23°C). 10 -3 , 10 -2 , 10 -1 , and 1 mol/dm 3 ion concentrations and 50, 150, and 300 g/Mg flocculant dosages were used in the light of the results of Gungoren et al (2018). The experiments were carried out at natural pH (~6.87).…”

“…Duzyol (2016) used Taguchi (L16) experimental design to determine the optimum conditions for the turbidity removal from fine coal suspensions and found that the most influential factor was the polymer dosage. Therefore, the flocculant dosage should be optimized for an effective flocculation process (Gungoren et al, 2018).…”