Optimizing thin‐layer drying conditions to improve waste sludge drying efficiency and modeling accuracy

Abstract In tandem with the expansion of the amount of sewage treatment, the production of sludge has increased significantly, making sludge treatment suffer from environmental problems. Optimizing sludge drying technology to reduce pollutant emissions and improve treatment efficiency will garner widespread concern and attention. This study explores the efficacy of the moisture distribution, temperature, and thickness of three types of sludge (brewery sludge, printing and dyeing sludge, and municipal sludge) using thin‐layer drying technology. Except for studying the three common moisture contents, it also expands on the influence of bound water on the drying process, and the addition of CaO primarily facilitates the conversion of a portion of interstitial water into free water. Additionally, multiple parameter combinations analysis of sludge drying illustrated that temperature has a more significant impact on the drying process of sludge than thickness, and increasing the temperature can mitigate the effects brought about by changes in thickness. Remarkably, under conditions of high temperature (200°C) and low thickness (0.5 cm), the drying curves of the three sludges showed little difference. Further, mathematical models of thin‐layer drying were elaborated, and it was found that the Page model was quantitatively processed with a higher experimental relationship ( R 2 = 0.9974) and a physical model was established to illustrate the role of CaO as a desiccant and conditioner to coordinate thin‐layer drying. Therefore, the optimization of the drying characteristics of thin‐layer sludge shows it is pivotal for adjusting the drying differences to reveal the drying behavior mechanism, as well as providing technical theoretical support.