Effect of Prestirring Time on Carbon Removal from Coal Fly Ash in the Flotation Technology

Abstract

Coal fly ash (CFA) is one of the industrial byproducts of burning coal for energy production and has unburned carbon, which negatively affects its full potential use. The flotation technology can be effective in separating unburned carbon from CFA, and the prestirring time is crucial for the ideal initial conditions during the flotation process. To find the suitable prestirring time, eight prestirring times, including 0, 1, 2, 3, 4, 5, 6, and 7 min, were selected in this paper, followed by flotation of CFA after prestirring. Parameters such as loss on ignition (LOI), the removal rate of unburned carbon (RUC), contact angle, and particle size volume fraction were used to assess the effect of prestirring time on flotation results. The results showed that the prestirring time significantly affects the CFA flotation performance. As the prestirring time increased, the LOI of CFA first decreased and then increased, and the contact angle showed the opposite trend. Besides, the prestirring time of over 2 min positively affected the fineness of the tailings. Overall, the prestirring time of 3 min had the most significant carbon removal effect, obtaining an LOI of tailings of 0.96%, a yield of 74.56%, an RUC of 72.70%, and a volume fraction less than 45 μm of 36.65%. This study provides theoretical support for improving stirring efficiency and saving flotation costs in industrial applications and is conducive to the recycling of CFA resources.

A comparative study of coal fly and bottom ashes as sustainable electroactive vibration damping materials

“…These results are consistent with the previously reported literature studies on coal ashes [32][33][34]. Although the presence of C atoms in coal ashes might be due to the residual carbonaceous materials, the low amounts of C atoms might be attributed to the excess oxidation condition in the steam boiler [35]. Considering the high atomic percentage of O atoms, it might be suggested that both ashes are composed of SiO 2 , Al 2 O 3 , and Fe 2 O 3 , which are well-known electroactive materials [36,37].…”