National Key Research and Development Program of China, Key Special Item of Intergovernmental International Technological Innovation Cooperation,

Project Title: Cement kiln cooperative disposal of incineration fly ash detoxified and dechlorinated by bioreactor landfill

Project Lead Unit: University of Science and Technology Beijing

Project Manager: Qunhui Wang

Execution period: January 2017 to December 2019

Project Description:

The resource utilization of incinerated fly ash is effective to solve the contradiction that the output of fly ash increases year by year and the available capacity of hazardous waste landfill sites decreases year by year.  The high-temperature calcination of fly ash in cement kilns can not only effectively fix heavy metals and destroy dioxin, but also effectively reduce the use of natural resources such as cement raw materials limestone and clay. However, in addition to traces of toxic and hazardous substances, fly ash contains high levels of chlorine, sulfur and heavy metals, which are the bottlenecks restricting its direct preparation of Portland cement. Therefore, the use of effective incineration fly ash pretreatment methods to remove heavy metals and chlorine in fly ash in advance has become an important direction of cement resource utilization of fly ash.

Chlorine and heavy metals in fly ash mainly exist in the form of soluble salts. At present, the more mature fly ash pretreatment method is water elution salt pretreatment. It can remove most of the water-soluble chlorine in fly ash. However, the chlorine in fly ash also contains water-insoluble chlorine, which cannot be removed by water washing. Biological leaching technology with microorganism as the main body can effectively destroy the fly ash mineral structure, expose more heavy metals and water-insoluble chlorine, increase the concentration of heavy metals and chlorine in the leaching solution, and facilitate subsequent heavy metal recovery. At the same time, the heavy metal content in the fly ash can also be reduced, meeting the industry standard HJ662 restrictions on the heavy metal content of the material entering cement kiln.

Incineration is the mainstream technology for waste disposal in Japan. Therefore, its research level in the field of stabilization and recycling of incinerated fly ash also ranks in the world. The Japanese cooperation team has a solid research foundation and many years of practical experience in the reduction of greenhouse gas emissions of organic waste, the utilization and risk assessment of fly ash. This project cooperates with Kyushu University in Japan to develop a bio-reactor landfill detoxification and dechlorination technology for incineration fly ash and organic waste based on bioleaching technology in order to overcome the shortcomings of waste of water resources, low removal rate of water insoluble chlorine, and great difficulty in heavy metal recovery caused by traditional water washing pretreatment of fly ash. This technology can improve the dechlorination efficiency of incineration fly ash, make the treated residue meet the standard limits of heavy metals and chlorine content in the materials entering the cement kiln, and achieve the purpose of providing alternative raw materials for cement production and co-processing with organic waste. While reducing the consumption of resources and energy in the process of ore mining (limestone and clay) and calcination, this technology can realize the efficient recycling of incinerated fly ash, which meets the requirements of national energy conservation, emission reduction and sustainable development, and has important strategic significance and application prospect.