18 / 2021-06-23 10:39:51

Water-heat balance characteristic of sewage sludge bio-drying process in a composting plant with air circulated

Bio-drying, Full-scale, Ventilation, Water-heat balance, air circulated

Bio-drying technology for sewage sludge has attracted much attention. The water-heat balance characteristic for practical bio-drying process was important. This study explored water and heat balance under different ventilation volume of 3.96 m³/kg initial matrix (low ventilation) and 5.52 m³/kg initial matrix (high ventilation) in sewage sludge bio-drying plant, and analyzed the influence of air circulation on water removal and heat recovery. The water content was removed effectively for 12 days bio-drying process, and decrease from 60.2% to 44.3% under low ventilation, and decrease from 62.2% to 48.7% under high ventilation. Compared low ventilation group, high ventilation obtained higher bio-drying index (7.04) and heat utilization efficiency (90.60%). The selection of ventilation strategy is to increased ventilation under the condition of maintaining high pile temperature. We proposed energy consumption index E, put ventilation and organic matter degradation converted energy input, the energy consumption index of high and low ventilation group were 3.78 MJ/kg and 3.36 MJ/kg. Compared with the bio-drying index, the cost index takes bulking agents and ventilation into account, which can be used to compare the bio-drying performance more accurately. The air circulation during achieved energy recovery (2135.01 - 4662.25 MJ) and improve the carrying capacity of water vapor (2.78 - 2.97 times), but brings more water to pile (1743.3 – 3793.8 kg) at the same time.