Study on Sewage Sludge Drying System With Built-in Solar Drying BedZhipan Gu, Jichun Yang, Jing Liu, Leren Tao, Ye Zhang and Lihao HuangE3S Web Conf., 237 (2021) 01041DOI: https://doi.org/10.1051/e3sconf/202123701041