School of Energy and Environmental Engineering, Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants, International Science and Technology Cooperation Base for Environmental and Energy Technology of MOST, University of Science and Technology Beijing, Beijing 100083, PR China.
Sci Total Environ. 2021 Jul 10;777:146109. doi: 10.1016/j.scitotenv.2021.146109. Epub 2021 Mar 2.
Microwave drying is attracting increasing attention due to its energy efficiency. A self-developed pilot-scale microwave dryer was used in this study to dry two different common types of sewage sludge, namely mechanically dewatered sewage sludge and composting dewatered sewage sludge, by using two heating modes: constant temperature and constant power modes. The microwave drying behavior, specific energy consumption, average drying rate, energy efficiency, and drying effect were explored considering the influences of microwave output power, initial mass, and heating mode. Results showed that the output power had the largest influence on specific energy consumption, energy efficiency, and drying efficiency, followed by the constant temperature and initial mass. The specific energy consumption of mechanically dewatered sewage sludge decreased by roughly 14%. By contrast, the average drying rate increased by approximately 6%, and the energy efficiency increased by approximately 20% for each 1 kW increase in output power. Meanwhile, composting dewatered sewage sludge displayed drying effects at an output power of 3 kW, and the temperature exceeded 80 °C. The comparison of the two modes suggested that the constant temperature mode was better than the constant power mode considering product quality and operational safety. Compared with six thin-layer drying mathematical models, the Midilli-Kucuk model could provide a good fit for the constant temperature mode. The proposed microwave drying process exhibited effective performance in drying rate. This process also demonstrated considerable application potential for sewage sludge drying.
微波干燥由于其高效节能而受到越来越多的关注。本研究采用自行开发的中试规模微波干燥设备，采用恒温模式和恒功率模式对两种不同类型的常见污水污泥（机械脱水污泥和堆肥脱水污泥）进行干燥，探讨了微波输出功率、初始质量和加热模式对微波干燥特性、比能耗、平均干燥速率、能效和干燥效果的影响。结果表明，输出功率对比能耗、能效和干燥效率的影响最大，其次是恒温模式和初始质量。机械脱水污泥的比能耗大约降低了 14%，而平均干燥速率提高了大约 6%，输出功率每增加 1kW，能效提高了大约 20%。同时，堆肥脱水污泥在输出功率为 3kW 时表现出干燥效果，温度超过 80°C。两种模式的比较表明，从产品质量和操作安全角度考虑，恒温模式优于恒功率模式。与六种薄层干燥数学模型相比，Midilli-Kucuk 模型更适合恒温模式。所提出的微波干燥过程在干燥速率方面表现出了有效的性能。该过程在污水污泥干燥方面也具有相当大的应用潜力。
