In with electric charge. In an experiment carried out

In order to prepare coal ash for further preparation, sieving is most preferable method. Sieving method able to characterize bulk material which is in different forms and sizes. This characterization has an essential role in both physical and chemical properties. This method is typically used due to its simplicity, low cost investment and chances to separate the particle size fractions. For an example, in a research conducted by D.Oz, H. Koca, S. Koca (2004), which used floatation method in their work, sieved the coal ash prior to the floatation.

 

2.1.1.1.1                     Mechanism of Sieving

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Sieving shakers are equipped with sieving trays and holes in between so that the particles able to pass through. During this sieving process, the apertures of every sieve are being compared with the particles. The ratio of the particle size to the sieve openings and particles’ orientation are being analysed to determine the chances of a particle to pass through the sieving mesh.

 

2.1.1.2   Tribo-electrostatic Separation

One of the advanced technique used in the separation methods is tribo-electrostatic separation. In this method, triboelectric effect is being used when particles of two different levels of non-conducting particles are keep in contact with electric charge. In an experiment carried out by R. Dwari, K. H. Rao (2008), tribo-electrostatic method was used to analyse dry coal beneficiation. The process was carried out in a newly built fluidised bed tribo-charger which works on the basis of polarity of particle charge generated. From the experiment, they concluded that the magnitude of particles was relatively high which indicates great efficiency.

 

2.1.3.2.1 Mechanism of Tribo-electrostatic Separation

         This equipment works based on triboelectric effect by electrifying the two different levels of non-conducting particles. Their trajectories is affected by the charge in the electric field. A separator consisting of two electrodes, where one of them is grounded. The electrodes are covered by insulationg aterials. This is to prevent the particles from recharging (Mach, F., K?s, P., Karban, P., Doležel, I, 2012).