ZERO FORMATION OF DIOXINS AND SUPPRESSION OF DE NOVE SYNTHESIS

通过燃烧实验和热力学评价的基础研究，明确了二恶英/呋喃（dioxins/furans，简称二恶英）主要形成于CO/CO_2比高的热力学非均相部位，即燃烧气体中残留的飞碳（C^*）物质表面的边界层。因此，认为蝇类C^*物质的分解或消失以及蝇类C^*物质的脱氯作用很难形成二恶英。本文研究了CaO对蝇类C^*物质的脱氯作用，以及高能量密度电磁波对燃烧气体照射在蝇类C^*物质周围的高CO/CO_2比边界层的色散是否实现了二恶英的零生成。用电磁波照射聚氯乙烯燃烧废气，其二恶英浓度为85 ng-TEQ/m^3 （s.t.p）。辐照条件为功率1.8 kW，频率915 MHz，辐照时间6 s，温度423 K。电磁波照射后的二恶英浓度降至2.4 ng-TEQ/m3 (s.t.p)，分解率约为97%。认为大量的二恶英是通过形成二恶英的蝇类C^*物质周围边界层的弥散，以及蝇类C^*物质随着升温而分解或燃烧而分解的。在较高的温度区域，二恶英的分解速率有望提高。在高温区设置CaO晶片床，二恶英从1 ng-TEQ/m^3 （s.t.p）急剧下降到0.007 ng-TEQ/m^3 (s.t.p)，这是因为在蝇C*物质内部和周围的氯被脱氯为热力学稳定的CaCl2。高温区脱氯对二恶英的零生成非常有效。

From our fundamental studies on combustion experiments and thermodynamic evaluations, it is clarified that dioxins/furans (Dioxins) are mainly formed at the thermodynamically heterogeneous site with high CO/CO_2 ratio, which is the boundary layer on the surface of the fly carbonaceous (C^*) matters remaining in combustion gas. Therefore, it is considered that Dioxins are hardly formed by the decomposition or the disappearance of the fly C^* matters and by the dechlorination from the fly C^* matters. The present study has investigated whether zero formation of Dioxins was achieved or not by the dechlorination from the fly C^* matters with CaO, and by the dispersion of the boundary layer with high CO/CO_2 ratio around the fly C^* matters through an irradiation of electromagnetic wave with high energy density to combustion gas.Electromagnetic wave was irradiated to an exhaust gas of PVC combustion, in which Dioxins concentration was 85 ng-TEQ/m^3 (s.t.p.). The irradiation conditions were the power of 1.8 kW, the frequency of 915 MHz, the irradiation time of 6 s, and the temperature of 423 K. Dioxins concentration after the irradiation of electromagnetic wave decreased to be 2.4 ng-TEQ/m3 (s.t.p.), the decomposition rate of about 97 %. It is regarded that a lot of Dioxins is decomposed by the dispersion of the boundary layer around the fly C^* matters, where Dioxins are formed, and by the decomposition or the burning out of the fly C^* matters with heating up. Decomposition rate of Dioxins are expected to improve more at higher temperature zone.By setting CaO chips bed in the high temperature zone, Dioxins extremely decreased from 1 ng-TEQ/m^3 (s.t.p.) to 0.007 ng-TEQ/m^3 (s.t.p.) because chlorine in and around the fly C* matters was dechlorinated to thermodynamically stable CaCl2. The dechlorination at the high temperature zone is very effective for zero formation of Dioxins.