Zhejiang University develops new sludge treatment technology

From the School of Energy Engineering of Zhejiang University, Professor Yan Jianhua of the Institute of Thermal Engineering of the university successfully solved the world-wide problem of sludge treatment. The integrated technology of sludge agitation indirect thermal drying and combined circulating fluidized bed cleaning and incineration developed by the research group independently dehydrates the sludge and then incinerates the sludge. This not only results in a 90% reduction in the volume of the sludge, but also truly achieves the pollution. The dual purpose of mud harmless treatment and energy utilization.

According to Yan Jianhua, the energy use of sludge needs to overcome three technical difficulties: First, sludge has a high moisture content, strong viscosity, what kind of drying technology can be used to reduce its moisture content, and achieve energy use? Second, sludge is different from conventional fuels. It has low calorific value, high moisture content, and a large amount of fly ash. What combustion technology can be used to ensure efficient, complete combustion and complete combustion of sludge? Third, the sludge contains a large number of pollutants. How can we ensure that secondary pollution is not generated during the sludge drying and incineration?

Yan Jianhua's research team developed a sludge agitation type indirect thermal drying and integrated circulating fluidized bed cleaning and incineration integration technology to solve these difficulties one by one. Yan Jianhua told reporters that the innovation of this integrated technology was inspired by the energy utilization technology of coal slime that was used during the development of their coal washing process some years ago. Compared to slime with higher calorific value, sludge produced during the sewage treatment process has a higher moisture content, a lower calorific value, a higher viscosity, and is more difficult to handle.

Through many years of sampling and research analysis, in view of the large viscosity and high sediment content of the sludge, resulting in equipment viscous and wear, the research team proposed a special type of agitation mixing method, through the optimization of blade arrangement and enhanced heat transfer, etc. Innovative technologies to develop agitation-type sludge drying technology and equipment that can reduce the moisture content of sludge from 80% to 30% or less, and then use low-grade residual heat steam as a drying agent for sludge drying equipment Medium to achieve energy use of sludge. In view of the difficulty of low sludge calorific value and non-uniform spatial combustion, the research team invented a highly efficient and low-polluting compound circulating fluidized bed sludge incineration technology, achieving stable ignition and efficient clean combustion of the sludge.

In addition, in order to reduce the secondary pollution generated during the sludge drying and incineration process, the research team also developed a coordinated control technology for pollutants in the whole process of sludge drying and incineration, which made the pollutant discharge in the incineration process better than the national standards. The f-emission concentration is better than the EU standard by two orders of magnitude.

It is reported that sludge drying and incineration integration technology has achieved remarkable industrialization results. Through technology research and development and industrialization cooperation, this technology has been used to build the world's largest processing capacity of 3,900 tons/day sludge incineration project of Zhejiang Qingyuan and a sludge agitation type indirect drying equipment with a single processing capacity of 500 tons/day. The main technical indicators have reached the international advanced level.

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