Coal fly ash, which is the solid waste produced during the coal combustion and utilization, causes serious environmental problems. The preparation of concrete from coal fly ash has been proven helpful in potentially improving its value and reducing its environmental impact to a certain extent. However, the presence of unburned carbon components affects the performance of coal fly ash-based concrete. In this study, unburned carbon is separated from coal fly ash by pre-classification and subsequent optimized flotation, wherein the factors influencing are explored. The results show that under the pre-classification function of the inflatable-inclined liquid–solid fluidized bed, the underflow product is enriched in unburned carbon particles, with loss-on-ignition (LOI) and yield (Y_o) values of 11.58 % and 72.87 %, respectively. Further, the underflow product is flotated for a cleaner carbon product, which is affected by the stirring rate (W) and the amount of collecting agent (C) and foaming agent (F_o). Optimized flotation (i.e., C = 18 kg/t, F_o = 6.5 kg/t, W = 1600 rad/min) results in the maximum combustible recovery rate of the flotation concentrate (89.89%), with LOI of 41.80 % and Y_o of 18.51 %, yielding unburned carbon products for fuel. After mixing the flotation tailings with the pre-classified overflow production, the LOI of the formed ash-rich product is 1.73% with Y_o of 81.49%, prepared into concrete. Thus, the proposed pre-classification and flotation process can improve the quality of coal fly ash. The results provide a theoretical basis for the harmless and resource treatment of coal fly ash.

粉煤灰是煤炭燃烧和利用过程中产生的固体废物，造成严重的环境问题。事实证明，从粉煤灰制备混凝土有助于潜在地提高其价值并在一定程度上减少其对环境的影响。然而，未燃烧的碳成分的存在会影响粉煤灰基混凝土的性能。本研究通过预分级和后续优化浮选从粉煤灰中分离出未燃碳，并探讨了影响因素。结果表明，在充气倾斜液固流化床的预分级作用下，底流产物富含未燃烧的碳颗粒，具有烧失量（ LOI）和产率（Y_o ) 值分别为 11.58 % 和 72.87 %。此外，浮选底流产物以获得更清洁的碳产物，其受搅拌速度（ W）以及捕集剂（ C）和发泡剂（ Fo）_{的量的影响。}优化浮选（即C = 18 kg/t， F _o = 6.5 kg/t， W = 1600 rad/min）导致浮选精矿的最大可燃回收率（89.89%）， LOI为 41.80 %， Y _o 18.51 %，产生未燃烧的碳产品作为燃料。浮选尾矿与预分级溢流生产混合后， LOI形成的富灰产品的含量为1.73％，Y _o为81.49％，制备成混凝土。因此，所提出的预分级和浮选工艺可以提高粉煤灰的质量。研究结果为粉煤灰的无害化、资源化处理提供了理论依据。