The Simulating Study Of Dioxins Inhibition Technology By Calcium-based Compounds In The Process Of Municipal Solid Waste Incineration

With the changing of human living habits and the way industrial manufacture, theproduction of living waste, medical waste, industrial waste and other waste is increasing.Waste incineration can make its volume reduction and realize energy recyclesutilization. However, it will produce some chlorinated aromatic organic pollutants, suchas dioxin (PCDD/Fs), polychlorinated biphenyls, polychlorinated naphthalene,polychlorinated chlorobenzene, etc., during the burning process, which is one of themain sources of PCDD/Fs emissions in the environment. In recent years, wasteincineration capacity enhanced and its application proportion increased in our country,unfortunately, unintentional produced and emissions of PCDD/Fs during incinerationhas become a key issue to restrict the development of incineration technology.This paper focuses on simulation study of PCDD/Fs suppressing techniques in theprocess of waste incineration. The main contents are as follows:1. For a preliminary inquiry of some kinds of commonly used calcium compoundssuch as CaO, CaCO3, Ca(OH)2. Then CaO was selected as one of the main componentof calcium-based inhibitor, because of its better inhibition performance. To exploresynergistic effect, CaO mixed with another metal oxide were studied, the results showedthat with CaO and MgO, CeO2, BaO, r-Al2O3mixtures adding, the generation ofPCDD/Fs has no magnitude orders of difference, synergistic effect not obvious. WithCaO and activated carbon mixtures adding, the total amount of generated PCDD/Fs wassignificantly reduced while its international toxicity equivalent increased due togenerated more lower chlorinated PCDD/Fs isomers2. Influences on the total PCDD/Fs formed of adding CaO, Urea2%, Urea5%,Urea10%, Urea20%, Urea50%, Urea100%, respectively, the blank group with noneinhibitor, under300°C for2h were studied. The results showed that the generatedPCDD/Fs isomers were quite different, especially when CaO and Urea added alone,which may be the main reason for CaO and Urea mixtures performed remarkablesynergistic suppression effect. With the increasing of mass ratio of Urea in the totalCaO and Urea mixtures, the total generated PCDD/Fs and I TEQ showed a trend of decreased first, then increased, and its TSE and I TEQ/SE showed a trend of increasedfirst, then decreased. After changing the reaction temperature, under250,350°Cconditions, the inhibitor also performed good suppressing effect, and total generatedPCDD/Fs and I TEQ showed the similar laws of under300°C.3. The reaction solid phase products of adding CaO and Urea20%inhibitors atroom temperature,250,300,350°C, respectively, were analysed by the X-ray powderdiffraction(XRD) and infrared spectrum diffraction(FT-IR). The results showed that,CaO and Urea mixtures inhibitor performed good synergistic suppressing effectmechanism may be as follows, Urea generated melamine after heating, might generatesubstances such as ammonia if continue to raise the temperature, ammonia can reactwith PCP to generate pentachlorophenol ammonium salt; and CaO can react with H2Othat formed from Urea heating and PCP condensation reaction, generated Ca(OH)2, thenacid-base reaction of Ca(OH)2and PCP generate pentachlorophenol calcium salt,moreover Ca(OH)2also can react with CO2formed from PCP, generated CaCO3, soPCP was converted into other substances.