Abstract
Aluminosilicate microspheres are a valuable fraction of coal fly ash with diverse applications due to their low density. Currently, there is no efficient and ecologically rational method of cenosphere recovery from fly ash. A combination of dry methods for the recovery of both fine ash particles and aluminosilicate microspheres from coal fly ash is presented. It is comprised of fluidised bed separation followed by screening and pneumatic separation in a free-fall air chamber. Fluidised bed separation was assisted by a mechanical activator to prevent agglomeration. This step reduced the portion of material that required further treatment by 52–55 wt.%, with the recovery of microspheres exceeding 97%. Then, the concentrates were individually subjected to pneumatic separation. The final separation product for the fly ash containing 0.64 wt.% cenospheres was a cenosphere concentrate that constituted about 17 wt.% of the initial fly ash. The recovery of cenospheres was around 81%. Usage of a combination of dry methods allowed for maintaining almost 83 wt.% of the raw material in its dry form. Furthermore, the produced fly ash grain fractions could be used for different industrial purposes.
Highlights
Nowadays, the dominant fuel used for electricity generation worldwide is coal
It is clearly shown that the bed, during the process, underwent segregation into characteristic layers: the bottom layer included mostly sand particles, the middle layer consisted of coarse fly ash particles and the upper layer contained in the majority char particles
Fly ash beneficiation is in agreement with the practice of sustainable waste management and leads to the increase in the market value of this industrial waste
Summary
Energy production based on coal is inevitably connected with several issues, notably with a generation of vast amounts of combustion by-products [1,2]. The main coal combustion by-product is fly ash and in many countries its utilisation level is low. Fly ash is an inhomogeneous material, concerning its chemical composition and physical parameters such as density and grain size. According to the practice of sustainable waste management, the whole mass of the fly ash should be divided into fractions of different chemical and physical properties to expand potential opportunities for its use. The low density (
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