Insight into the Enhanced Removal of Water from Coal Slime via Solar Drying Technology: Dewatering Performance, Solar Thermal Efficiency, and Economic Analysis

Abstract

In this work, solar drying technology was applied for the deep dewatering of coal slime to save thermal energy and reduce the dust produced during the hot drying process of coal slime. Solar drying technology is used to dry coal slime to realize its resource utilization. The influence of solar radiation intensity and slime thickness is investigated on the drying process. The greater the solar radiation intensity (SRI) is, the faster the drying indoor air and coal slime are heated, and the faster the drying efficiency is. As the slime becomes thinner, the internal water diffusion resistance becomes smaller and the drying efficiency correspondingly becomes faster. In addition, to facilitate the application of coal slime drying in the actual project, the Page model is fitted and found to have a good fit for solar drying coal slime. Meanwhile, the optimal drying conditions are determined by analyzing the energy utilization under different conditions. It is found that the target moisture content of 10% is optimal for coal slime drying with the highest energy utilization. The laying thickness (L) of 1 cm has the highest solar thermal efficiency of 54.1%. More importantly, economic calculation and analysis are conducted in detail on solar drying. It is found that the cost of solar drying (¥38.59/ton) is lower than that of hot air drying (¥ 65.09/ton). Therefore, solar drying is a promising method for the drying of coal slime.