A Cutting-Edge “Turning Waste into Treasure” Technology for Municipal Solid Waste

With the improvement of people’s living standards, the amount of municipal solid waste (MSW) has also increased year by year, resulting in a series of environmental problems that have attracted the attention of the whole people. MSW contains a lot of combustibles that can be used as fuel for cement production, and inert as raw meal for cement production. These are techniques of co-processing MSW in cement kilns. The high temperature, long residence time of materials and flue gas, good turbulence, oxygen-rich characteristics and alkaline environment in cement kiln, whice are conducive to the degradation of organic matter and the solidification of heavy metals in MSW. Meanwhile, cement kiln co-processing techniques have been widely recognized and applied in the world, because of them unique advantages such as small investment, low operating cost and no impact on product quality. It is very important to realize the pre-treatment technologies, clinker production and environmental risk to comprehensively evaluate cement kiln co-processing techniques characteristics.

Cement kiln co-processing techniques have been developed in recent years in China, and more than 60 factories now use fermentation, screening, and gasification pre-treatment techniques to co-process municipal solid waste. However, there are no complete reports on common MSW pre-treatment technologies, cement kiln co-processing techniques and corresponding environmental risk assessment in China.

To comprehensively assess the exposure risks to the environment by commonly used MSW pre-treatment processes and the CK production process in China, Researcher Dahai Yan from Chinese Research Academy of Environmental Sciences, Master Hua Long from Sichuan Normal University and their team members have conducted at three representative cement factories of China. This study entitled “Assessment of popular techniques for co-processing municipal solid waste in Chinese cement kilns” is published online in Frontiers of Environmental Science & Engineering.

In this study, alternative raw meal and alternative fuels produced by fermentation, screening and gasifier pretreatment technologies and corresponding pollutant emissions were respectively concerned, which is conducive to comparative evaluation of the characteristics of mainstream MSW pre-treatment technologies. The alternative raw meal and alternative fuels produced in the pretreatment process are respectively put into the cement kiln for co-processing. It is necessary and significant to analyze and evaluate  flue gas and by-pass flue gas pollutants emission for environmental risk assessment of cement kiln co-processing techniques. The analysis of dioxin content, chlorine mass balance and heavy metal distribution characteristics (including heavy metal recycling ratio) in cement kiln dust and bypass cement kiln dust is beneficial to reveal the mechanism of pollutant migration and enrichment, provide important reference data for optimization design of cement kiln co-processing procedures. Quality assessment of clinker produced in the co-processing was carried out to provide a detailed scientific basis for the process of “turning waste into treasure”.

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