| The state-of-the-arts about dioxins from coal and waste combustion processes in the world is reviewed in details with concerning the following aspects: environmental problems about dioxin formation from municipal solid waste (MSW) incineration processes, the dioxin emission percentage of waste incineration to the total environment, dioxin formation from uncontrolled combustion processes, dioxin inhibition and control mechanisms for combustion processes. The project is sponsored by China National Key Basic Research Special Funds project (G1999022211), key project of National Nature Science foundation (N59836210), National Nature Science foundation (N59878O47). Through an experimental way, much detailed basic work was conducted to investigate the dioxin formation inhibition and control mechanisms from coal and waste combustion processes with variety points. All results obtained could serve as guidelines for practical application concerning dioxins. The main topics of this dissertation are as follows:1) Fly ash is the main carrier of dioxins from waste incineration process; its distribution with size fractions from two typical incinerators (grate fired and fluidized bed fired) in China is studied. Dioxin concentration in fly ashes from bag filters in several incinerators is also compared. The results suggest that dioxin concentration in fly ash from fluidized bed incinerators is much lower than that from grate-fired incinerators. The following aspects: incinerator type, combustion operation system, fuel component, char, heavy metal and chlorine content in fly ash, are discussed to explain the great differences of dioxin concentration for the fly ash from different incinerator types, and the distribution of dioxin concentration with size fraction.2 ) The heterogeneous catalyzed reaction in fly ash surface is the main mechanism for dioxin formation in post combustion zone. Different sources were used to study dioxin formation from heterogeneous catalyzed reaction in fly ash surface with concerning different factors, such as oxygen, carbon, catalyst, C/Cu, particle size and inorganic chlorine. The differences of dioxin formation from different sources at low temperature are discussed. Furthermore, chlorinating reactions playing important roles on heterogeneous catalyzed reaction process is discussed generally.3) In order to stabilize the combustion process, MSW is co-fired with coal. The co-firing of waste and coal was found to inhibit dioxin formation greatly, and the sulfur in coal was explained to this inhibition. In this dissertation, three series of experiments were done in order to better understand the influence of sulfur during dioxin formation process. The results from heating of PCP and element sulfur under different temperatures showed that, the toxic lag phenomenon could be observed about 500℃, sulfur could inhibit dioxin formation when heating temperature was setover 500℃ and on the contrary more dioxin formed when heating temperature is less than 500℃. The S/Cl in fuel also has a great influence on dioxin formation from precursors. When standard coal according to different sulfur content and PCP were co-fired, the dioxin inhibition efficiency was over 80% and even over 99%. Beside at high temperature, Sulfur and its oxides can influence dioxin formation at low temperature on heterogeneous catalyzed reaction. Collaboration with USEPA was carried out about this field. The reaction mechanism of Cl2 with SO2 was discussed in details under different combustion systems. There is an interaction with fly ash and SO2 on the transformation of Cl2 to HC1. The mechanism of SO2 on the heterogeneous catalyzed reaction of Cl2 and fly ash was suggested4 ) Combustion is a main dioxin emission resource in our country. Dioxin emission from coal combustion boiler, different density fluidized bed waste and coal co-fired incinerator was tested and dioxin input and output balance in incineration systems was calculated. The results suggested that ESP has a great influence on the dioxin emission from. The annual dioxin emission fr...
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