College of Mechanical and Electrical Engineering, China Jiliang University, Hangzhou, 310018, PR China.
College of Mechanical and Electrical Engineering, China Jiliang University, Hangzhou, 310018, PR China.
Water Res. 2021 Feb 1;189:116611. doi: 10.1016/j.watres.2020.116611. Epub 2020 Nov 7.
The disposal of huge municipal sludge with high moisture content has led to numerous energy consumption and brought extensive concerns in the world. In this paper, three dewatering modes, ultrahigh-pressure mechanical dewatering mode (UMDW), pressurized electro-dewatering (PEDW) with constant voltage mode (U-PEDW) and constant voltage gradient mode (G-PEDW) were performed on a self-designed pressurized electro-dewatering apparatus for municipal sludge. The pore structures and moisture distributions were detected by low-field nuclear magnetic resonance technology. Meanwhile, the moisture distributions and quantitative bound strength were analyzed by the thermogravimetric differential scanning calorimetry test. Moreover, a pore-scale electro-osmosis model was accordingly developed based on the fractal characteristics of pore size distribution. Finally, the effect of dewatering modes and operating parameters on moisture content and energy consumption were examined in detail. The results indicate that the pore-scale electro-osmosis model show good consistency with experimental data. The electric field can drive the middle-layers-water to overcome the capillary pressure, and make G-PEDW removing more water than UMDW. The moisture content of dewatered municipal sludge by G-PEDW and U-PEDW reaches to 28.41% and 27.33%, respectively. Furthermore, the energy consumption of G-PEDW is 189.62Wh/kg., it is much lower than that of U-PEDW. Therefore, the G-PEDW mode with low moisture content and less energy consumption indicates best dewatering performance compared with UMDW and U-PEDW modes. The present work is helpful to understand the dewatering mechanisms of G-PEDW and provides useful guidelines for G-PEDW dewatering technology.
高含水率市政污泥的处置需要消耗大量能源，引起了世界范围内的广泛关注。本文采用自行设计的加压式电脱水装置，对超高压力机械脱水模式（UMDW）、恒压模式加压电脱水（U-PEDW）和恒压梯度模式加压电脱水（G-PEDW）三种脱水模式对市政污泥进行了脱水处理。采用低场核磁共振技术检测了孔结构和水分分布，通过热重差示扫描量热试验分析了水分分布和定量结合强度。此外，还根据孔径分布的分形特征，相应地建立了孔隙尺度电渗流模型。最后，详细考察了脱水模式和操作参数对水分含量和能耗的影响。结果表明，孔隙尺度电渗流模型与实验数据具有较好的一致性。电场可以驱动中层水克服毛细压力，使 G-PEDW 比 UMDW 去除更多的水。G-PEDW 和 U-PEDW 脱水后市政污泥的含水率分别达到 28.41%和 27.33%。此外，G-PEDW 的能耗为 189.62Wh/kg，远低于 U-PEDW。因此，与 UMDW 和 U-PEDW 模式相比，G-PEDW 模式具有低含水率和低能耗的特点，表现出最佳的脱水性能。本工作有助于理解 G-PEDW 的脱水机制，并为 G-PEDW 脱水技术提供了有用的指导。
