Study On Rotary Disc Drying Technique Of Sewage Sludge And Optimization Of Process

With the rapid development of sewage treatment in china, sewage sludge production has increased quickly. The water content of mechanical dewatering sludge (about 80%) is too high to meet the argillaceous requirement of landfill, compost, incineration and land utilization. Due to sludge thermal drying has advantages of significantly reducing the volume and weight of sludge, killing pathogen and microorganisms, and maintains the nutritional content and calorific value of sludge, sludge could be further used for landfill, compost, incineration and land utilization. Sewage sludge drying is the prerequisite as resource for sludge disposal and utilization. Based on above, in the dissertation the rotary disc drying technique optimization is studied, and environment-friendly and efficient rotary sludge drying demonstration has been built.The background review of sewage sludge and sludge disposal has been introduced. Several common technologies of sludge thermal drying were summarized and the structure, function, features and engineering application of rotary disc dryer are introduced. The rotary disc drying technique was recommended as the dominant sludge thermal drying technology, overall consideration of the type, energy consumption, safety, environmental friendliness, flexibility of sludge thermal drying.Sludge production of wastewater treatment plant and current treatment situation of sludge in Kun Shan city are introduced, and physical and chemical properties of sludge are analyzed. Due to the technique optimization, the optimum operating condition of rotary disc dryer is selected: inlet amount 20kg/h, steam flow 14.87kg/h, steam temperature 133.5℃, revolution speed 10rpm, with the use of the rotary disc dryer independent developed by our school.Combination of physical and chemical properties of sludge, basic drying characteristics of sludge, and according to the result of rotary disc drying technique optimization, rotary sludge drying demonstration is built. Technology route and process flow of demonstration project are determined, and base construction and equipment installation and debugging are completed. After 240 days to run verification, the result of sludge drying system of the demonstration project reach the intended target. The water content of sludge is below 53% after drying, and stability is well. The results of dry exhaust emissions monitoring show that the drying process had high performance. NH3 content of drying exhaust is 9.42-45.4mg/m~3, H2S below 0.001 mg/m~3,total hydrocarbon 5 mg /m~3,reach the standard. The results of economic analysis of the demonstration project show that energy consumption (electric energy consumption and thermal energy consumption) was the largest expenditures of drying total cost, about 83%. The drying process uses the latent heat recovery equipment to achieve heat recycling, and thermal efficiency reaches more than 85%, drying energy consumption 673.5 kcal/kg(H2O), cost of drying 123.43 yuan/t (wet sludge), which reached the advanced level comparison of domestic and foreign similar sludge drying technology and had broad prospects.