Coal tailings

Coal Slurries - Two component treatments prove to be effective on a commercial scale for coal slurry flocculation. The use of encapsulated floccuiant suspended in a counter charged floccuiant provides the robusmess of traditional dual component systems, but with additional performance advantages, which include reduction in filter cake moisture content and an increased throughput rate. Figure 5 illustrates the typical filter cake moisture content obtained by a conventional treatment system compared to the encapsulated treatment system using coal tailings as the substrate. 

Rotary cascading bed incineration is an ex situ incineration technology that can treat organic-or hydrocarbon-contaminated materials such as sewage sludge, refinery sludge, coal tailings. 

Capillary bridges can also be created in liquid systems. Let, in the same fig., A be water and the hatched immiscible liquid be an oil. Then an attraction is created between the particles and this has to compete with the disjoining pressure. In practice the phenomenon is used by adding an oil as an agglomeration aid to coagulate slurries of hydrophobic particles, such as coal tailings. 

Secondary belite, free lime, periclase autoclave problems Failure of solid fuels (fly ash, carbonaceous shales, coal tailings as part of raw mix) to bum before granulation zone (Hawthorne, Richey, and Demoulian, 1981)... 

Coal tailings Filter press Amorphous/- 1, 5, 14 Dimensional stability for large... 

Field showed that a combined anionic flocculant/cationic coagulent system, at constant coagulent dose, performs better on coal-tailings than when flocculant alone is used. In general, it is the type of solid-liquid processes in use which dictate the molecular weight of the chosen electrolyte—see Table 4.5. On the other hand, the chemical type necessary generally depends on the slurry characteristics, i.e. solid chemical surface type, particle size distribution, the dissolved electrolytes and the pH. 

Clayey coal tailings highly cationic coagulent Medium molecular weight anionic polyacrylamide plus 0.03-0.05 kg... 

Coal tailings Low to medium/high anionic polyacrylamides 0.04-0.06 kg... 

Mid-range anionic copolymers (15—45mol%) are often used to treat neutral slurries such as coal tailings or sand and gravel effluents. 

Whatever the size of coal being processed, there will always be a need to separate residual coal from the washings, for which the decanter is a standard separating device (as well as for the final dewatering of waste liquids — the coal tailings). Fine coal may also be separated by means of froth flotation, and the dewatering of flotation concentrates is another good application for decanters. 

Coal tailings require the use of an anionic flocculant, albeit a relatively small amount, which is usually admitted upstream of the decanter, as in this case. The first four runs recorded were conducted at a standard bowl speed, giving just under 2400g gravitational field. The last six runs were when using a much lower gravitational field, under 1 OOOg. 

Table A.8 Coal tailings data discussed in Section 6.4.8...

Polyacrylates are used extensively as dispersants for emulsion paints and as boiler-scale inhibitors and copolymers of acrylic acid and acrylamide are used to aid water clarification at water treatment works and for the treatment of coal tailings. The manufacture of such polyelectrolytes could leave a small residue of unpolymerised acrylic acid monomer in the polymer. 

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