In sludge treatment, drying sludge using typical technology with high water content to a water content of approximately 10% is always difficult because of adhesive characteristics of sludge in drying. Many methods hav...In sludge treatment, drying sludge using typical technology with high water content to a water content of approximately 10% is always difficult because of adhesive characteristics of sludge in drying. Many methods have been applied, including direct and indirect heat drying, but these approaches of reducing water content to below 40% after drying are very inefficient in energy utilization of drying sludge. In this study, fry-drying technology with a high heat transfer coefficient of approximately 500 W/m2·°C was used to dry swine excreta, sewage and industrial sludge. Also waste oil was used in the fry-drying process, and because the oil’s boiling point is between 240°C and 340°C and the specific heat is approximately 60% of that of water. In the fry-drying system, the sludge is input by molding it into a designated form after heating the waste oil at temperatures between 130°C and 150°C. At these temperatures, the heated oil rapidly evaporates the water contained in the sludge, leaving the oil itself. After approximately 8 - 10 min, the water content of the sludge was less than 10%, and its heating value surpassed 20,000 kJ/kg. Indeed, this makes the organic sludge appropriate for use as a solid fuel. The dried swine excreta, sewage and industrial sludge can be used in an incinerator like low-rank coal or solid fuel.展开更多
Scale pig production is an effective approach to improve farmers＇ income. Many pig feeding villages and intensive pig farms has presented rapidly in Center China in recent years, the focus of large quantity of manure...Scale pig production is an effective approach to improve farmers＇ income. Many pig feeding villages and intensive pig farms has presented rapidly in Center China in recent years, the focus of large quantity of manure and sewage discharged by pig farms has become the leading source of pollution in vast rural areas. How to dissolve the contravention between the development of scale pig production and the serious pollution caused by swine excreta in rural area is a complex systematic problem. An approach named Systems Dynamic Digraph Analysis Approach is presented in this paper. And the approach is applied to analyze the scale pig breeding system in small hill watershed area systematically. A case of Pingxiang Taihua pig farm in the west region of Jinggang Mountain, which is a typical intensive pig farm in small hill watershed area in Center China, was studied, after the systematical analyses with its system dynamic digraph, three common management policies are presented at the end of the paper.展开更多
文摘In sludge treatment, drying sludge using typical technology with high water content to a water content of approximately 10% is always difficult because of adhesive characteristics of sludge in drying. Many methods have been applied, including direct and indirect heat drying, but these approaches of reducing water content to below 40% after drying are very inefficient in energy utilization of drying sludge. In this study, fry-drying technology with a high heat transfer coefficient of approximately 500 W/m2·°C was used to dry swine excreta, sewage and industrial sludge. Also waste oil was used in the fry-drying process, and because the oil’s boiling point is between 240°C and 340°C and the specific heat is approximately 60% of that of water. In the fry-drying system, the sludge is input by molding it into a designated form after heating the waste oil at temperatures between 130°C and 150°C. At these temperatures, the heated oil rapidly evaporates the water contained in the sludge, leaving the oil itself. After approximately 8 - 10 min, the water content of the sludge was less than 10%, and its heating value surpassed 20,000 kJ/kg. Indeed, this makes the organic sludge appropriate for use as a solid fuel. The dried swine excreta, sewage and industrial sludge can be used in an incinerator like low-rank coal or solid fuel.
基金The research is supported by National Natural Science Foundation of China（70361002）.
文摘Scale pig production is an effective approach to improve farmers＇ income. Many pig feeding villages and intensive pig farms has presented rapidly in Center China in recent years, the focus of large quantity of manure and sewage discharged by pig farms has become the leading source of pollution in vast rural areas. How to dissolve the contravention between the development of scale pig production and the serious pollution caused by swine excreta in rural area is a complex systematic problem. An approach named Systems Dynamic Digraph Analysis Approach is presented in this paper. And the approach is applied to analyze the scale pig breeding system in small hill watershed area systematically. A case of Pingxiang Taihua pig farm in the west region of Jinggang Mountain, which is a typical intensive pig farm in small hill watershed area in Center China, was studied, after the systematical analyses with its system dynamic digraph, three common management policies are presented at the end of the paper.
