九州清源

CoWaste |Publication|MSWI FA| 02.09.2018

Municipal Solid Waste Incinerator Fly Ash CoWaste Alternative Solution to the LandfillMunicipal Solid Waste Fly Ash (MSWI FA) refers to the residue that the waste incineration power plant (also called Waste to Energy “WtE”) collects in the flue gas purification system and the total amount is about 3 to 5% of the MSW disposal volume.  

For example an incinerator with a treatment capacity of 600 t MSW produces around 20 tons per day.

MSWI FA contains organic pollutants such as benzopyrene, benzanthracene, dioxins and trace of heavy metals such as Cr, Cd, Hg, Pb, Cu, Ni and is classified as hazardous waste.

At present, the disposal of MSWI FA mainly adopts the method of landfill, but it faces the problems of difficult site selection, high construction cost and surrounding environment pollution.  In fact, the incinerator can only offer a partial solution of the fly ash environmental problem.

According to the compositional characteristics, the MSWI FA can be utilized as alternative raw material for cement production, so this is a very competitive advantage in order to achieve an integral and total solution for fly ash treatment.

However, the high salinity of fly ash (mainly chloride, in some cases ˃15%) makes necessary a preliminary study of the chlorine content in order to choose the right technology (from the operational and economical point of view) to avoid and control potential problems related to fly ash salinity in the cement kiln.

In this case, the co-processing of fly ash as alternative raw material (ARM) is a viable and real alternative solution to the landfill.

Municipal Solid Waste Incinerator Fly Ash (MSWI FA) Co-processing in the Cement Production: An Integral Solutio

· Dioxin removal: High to very high system temperatures. In a study performed for the World Business Council for Sustainable Development data from more approximately 2200 PCDD/F measurements from wet and dry kilns, performed under normal and worst case operating conditions, and with the co-processing of a wide range of hazardous wastes fed to both the main burner and to the precalciner shows that most cement kilns can meet an emission limit of 0.1 ng TEQ/Nm3 (Karstensen, 2008a).

· Heavy metals removal:  All trace elements (heavy metals) safely embedded in final product.  (Karstensen, 2012. SINTEF). Due to the high temperature of the rotary kiln, strong turbulence of the high-temperature gas in the kiln and the alkaline atmosphere, most of the heavy metal elements in the fly ash are fixed in the clinker, avoiding its re-pollution of the environment.

· Mineral input: All mineral input turned into product. (Karstensen, 2012, SINTEF).  The fly ash contains 12% to 65% of lime and some silicon, aluminum, which can be disposed of in cement kilns. The Co-processing of MSW Incinerator Fly Ash (MSWI FA) can reduce the consumption of traditional raw material for cement production.

CoWaste MSWI FA Co-processing Technologies

According to the characteristics of the fly ash source and composition (key parameter, the chlorine content),  CoWaste can offer two alternatives to do the Co-processing of fly ash viable from the operational and economical point of view as a real alternative to the landfill 

 Technology 1 (Chlorine ˂ 5%): Direct feeding/Dosing into the kiln system

Technology 2 (Chlorine ˃ 5%): Washing Process (Chlorine removal, ˃98%) + Feeding/Dosing into the kiln system

For both technology options, a Chlorine bypass system is required in order to control and avoid clogging and operational problems in the cement kiln system during the fly ash Co-processing.

Many studies and international experiences have shown that MSW Incinerator Fly Ash washing and cement kiln co-processing technology is an effective method of fly ash disposal.