Volatilization Mechanism of Pb from Fly Ash in Municipal Waste Incinerator

Abstract

Fly ash produced by waste combustion is designated as specially controlled waste in Japan due to harmful heavy metals contained in it and is legislated to be processed properly before disposal to landfill. As for technologies for making the fly ash harmless, several methods are recommended for the treatment, but each of them has some problems to be solved. The fly ash from a municipal solid waste incinerator contains large amounts of chlorinated compounds that make the harmful treatment difficult. A complete recycling of waste residue left behind after waste incineration, however, is required to solve the shortage of available final disposal sites. With this background, a new technology needs to be developed, that the heavy metals in the fly ash are removed sufficiently, no harmful heavy metals are leached and the residue ingredients are used effectively. In addition, Japanese government revised the Soil Contamination Countermeasures Law in February 2003 to strengthen the soil environmental evaluation standards. This could also promote the development of above technology. This paper focuses on lead that is particularly emphasized in the law, and proposes an advanced technology to remove lead from the fly ash, discussing the removal mechanism and removing conditions of lead. The newly developed technology is associated with the sintering process using a rotary kiln, and effectively uses only the chlorinated compounds contained in the fly ash to volatilize and remove the heavy metals. The technology achieves satisfactory low level of dioxins as well as prevention of lead leach. The fly ash treated by the technology also has passed a leaching test at pH 4 simulating typical acid rain circumstances.

Differences in cadmium transfer from tobacco to cigarette smoke, compared to arsenic or lead

“…From thermodynamics, chlorides are favored over sulfides above 300 °C for both cadmium and lead [96] . They were found to be the preferred species up to at least 600 °C [110] , [111] . The reaction of lead with chloride, even from lead oxide, is spontaneous at elevated temperature [111] , and no PbCl 4 is formed [109] .…”

“…They were found to be the preferred species up to at least 600 °C [110] , [111] . The reaction of lead with chloride, even from lead oxide, is spontaneous at elevated temperature [111] , and no PbCl 4 is formed [109] . CdCl 2 and PbCl 2 are the most volatile documented species for lead and cadmium.…”

Thermogravimetric Investigation of the Lead Volatilization from Waste Cathode-Ray Tube Glass

“…Lead present in the waste is volatilized in the presence of chlorine sources and released into the environment, if not recovered as fly ash. However, the same effect can be used for detoxification of heavy-metal contaminated materials such as contaminated soil [15], and ashes 112 from the incineration of sewage sludge [16] and municipal waste [17][18][19][20][21]. It has also been used for the separation of lead from galena ore [22], iron in electric arc furnace dust [23,24], and from cement during cement sintering [25].…”

Removal of lead from cathode ray tube funnel glass by chloride volatilization

“…This process was already successfully used to remove lead, zinc, cadmium, and other metals that form volatile chlorides under these conditions from fly ash (Jakob et al 1995(Jakob et al , 1996Chan and Kirk 1999;Matsuno et al 2003;Saikia et al 2007), metal ores (Kanari et al 2001;Yoo et al 2005;Lee and Song 2007), molten slag (Wang et al 2010;Kageyama et al 2013), and other waste materials. In many cases, the chlorine content of the substrate was sufficient to achieve the desired reduction of the heavy metal content.…”