Leveraging the performance of washing cycles to enhance the preprocessing of coal fly ash

Abstract

Coal is relatively cheap and abundant fossil fuel contributing to 40% of the world's electricity production. However, coal combustion generates a significant number of by-products, majority being the coal fly ash (CFA). The heterogeneous nature of CFA poses significant challenges in its value-added applications hence, requiring appropriate preprocessing treatments which are expensive and technically savvy. Therefore, this research aims to improve CFA's suitability for the application of value-added products through a technique called “washing cycles” which wash the CFA multiple times using distilled water under a controlled environment with continuous and vigilant monitoring to ensure accuracy throughout the entire process. To optimise this washing cycle process, parameters such as the number of washing cycles, stirring time, and temperature were analysed, and the results were optimised through surface response methodology. The analytical findings on the optimization process demonstrated that a suitable pre-treatment involved employing five washing cycles with a stirring time of 7.5 minutes. Furthermore, varying the temperature did not yield a substantial effect on the effectiveness of washing cycles, since the precipitation of Ca2+ ions even complicate the preprocessing. Therefore, we recommend conducting additional investigations into the efficient use of pre-processed CFA to produce value-added applications adhering to circular economy and sustainability.