| Incineration treatment is currently becoming one of the main disposal technologies formunicipal solid waste(MSW) and medical waste(MW) in China, however, dioxin-a highly toxicsubstance mainly generated from the process likely pose huge harm to the ecological environmentand human health. Dioxin is normally emitted into the surrounding of incineration plant by meansof flue gas and fly ash.Furthermore, the total yield of dioxin of fly ash contributed to the morethan 80% of total yield of dioxin generated from the source of waste incineration. Based on theurgent demand for developing efficient technology to control the dioxin emission fromincineration process, a series of fundamental studies involving of control technology for dioxincontained in fly ash were conducted by means of experimental and theoretical way, which aresponsored by the doctor-ship fund for college education of State Ministry of Education and pre-study fund for cross-disciplined task of Zhejiang University. The main contents of thedissertation are formed by the six parts as follows.1) The physical and chemical properties as well as the characteristic of dioxins content ofslag, deposited ash and fly ash sampled from a rotary kiln and fluidized bed multi-stageincinerator engaging for MW treatment were studied. It was found that chlorine and ferrouscontent of deposited ash sampled from air pre-heater is highly greater than that of fly ash and slag,and the calcium content is lower than the that of fly ash and slag; Comparably speaking, the dioxincontent of slag is extremely lower than that of deposited ash and fly ash, which is characterized asboth high concentration and fluctuated in wide range; and the de-nova mechanism is majorpathway contributing the dioxin formation of deposited ash and fly ash.2) Mechano-chemical treatment of aryl chlorine was experimentally studied. It was found that:under the condition of 246TCP mixed with CaO in a molar ratio of 1:16, a series of chemicalreactions induced to occur by ball milling, and organic chlorine of 246TCP is gradually changedinto ion-state chlorine as milling proceeding. Dechlorination, complete destruction, carbonationand carbonization are the reaction mechanism contributing to the degradation of 246TCP duringMechano-chemical treatment. A global model for kinetic orbit of milling ball and a local-modelfor energy transferring during collision of milling ball are proposed, the effect of ratio ofrevolution speed to rotary speed(ω/Ω)and revolution speed (Ω)on the colliding speed, collidingenergy and efficient mechanical energy were studied by the simulation through above two models.The results indicate thatω/Ω=1.15 is the condition to produce the maximal colliding energywhenΩis fixed. 3) Mechano-chemical treatment of dioxin contained in MW fly ash was experimentallystudied. Fly ash mixed CaO at a fixed weight ratio range of 0.06～1.5, the degradation of dioxinin fly ash was observed after the mixture powder treated by mechano-chemical method. Thedegradation efficiency of dioxin rises in correlation with the increasing dosage of CaO in somedegree. Two types of MW fly ash were directly treated by mechanochemical method. It wasamazingly observed that the dioxin in fly ash had been degraded without the addition of CaO. Inorder to confirm the result, an additional test was carried out in OCDD-OCDF contained fly ash,which was manually synthesized by spiking OCDD and OCDF into the thermal treated fly ash,then such fly ash was mechano-chemically treated in the same manner. It was found that the flyash acting like CaO or other degradation catalysis induces the degradation of PCDD/Fs containedin itself during mechano-chemical treatment.4) Low-temperature thermal treatment(LPTT) of dioxin in MWI fly ash was studied intubular fumace. In two different atmospheric condition as flowing nitrogen and atmosphericcondition, both the formation and degradation of PCDD/Fs were observed in fly ash incorresponding to respective temperature range. However, it was appeared as quite different in theextent of formation and destruction as well as variation trend due to the different atmosphere, butde nova formation is commonly contributed that formation of PCDD/Fs in both atmosphere.Based on the test results, it is concluded that atmospheric condition, temperature of 450℃andresidence time of lh are the optimal condition for LPTT to guarantee the destruction efficiency ofPCDD/Fs greater than 99%. In pilot-scale LPTT system, different types of MWI fly ashes weretreated. Comparably speaking, the degradation efficiency of dioxin contained in fly ash of fixedbed stocker incinerator was higher than that of fly ash of fluidized bed incinerator, anddegradation efficiency generally increasing with prolonger the treatment duration. It was shownthat water cooling was better than air cooling to prevent from forming dioxin during coolingperiod of treated fly ash.The total concentration of dioxin was abated to 97.2～99.8% as well as forTEQ concentration was reduced to 94.1～99.1%, which means the LPTT treated fly ash compliedwith the international standard of dioxin for residential soil.So, it was confirmed that the LPTT isa efficient measure to reduce the total discharge for dioxin contained in fly ash. Based on the pilotsystem and operational condition, economic analysis of LPTT system for a 10T/D MWI plant wascarried out.
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