Developing Suppression Techniques for Dioxin (DXN)s Released from Small-scale Incinerators for Industrial Wastes by Adding Titania Particles

目前的工作旨在开发一种方法，通过在焚化炉中添加一种化学物质（含硫二氧化钛）来抑制工业废物焚化炉排放的二恶英（DXN）s的形成，这种方法难以在良好的控制燃烧下运行。第一年，在聚氯乙烯粉末中加入一定量的水合石灰（Ca(OH)_2），进行了不完全燃烧实验。实验表明，Ca(OH)_2添加量为33.2wt%时，燃烧样品中的DXNs浓度比未添加Ca(OH)_2时降低了约1/10。然而，我们得出的结论是，即使使用比Ca(OH)_2反应性更强的二氧化钛，这种在焚化炉中添加化学物质的技术也不足以对未来的总排放量进行调节。因此，我们重点研究了DXNs最集中的粉煤灰的二次热处理。在常规方法中，粉煤灰中的DXNs在500℃以下的还原气氛下，通过添加一些化学物质进行脱氯，因为500℃以上的粉煤灰易凝固。在第二年，我们研究了粉煤灰在高温下凝固的机理，并试图建立防止粉煤灰凝固的高温处理技术。选择氢氧化钠（NaOH）和莫来ile作为能捕获飞灰中的氯的添加剂，假设它可能有助于凝固，然后将所选的化学品与飞灰按给定的比例混合，然后在700℃的电炉中加热。结果表明，掺加添加剂的粉煤灰在热处理后未发生凝固。此外，x射线衍射分析表明，加热前的粉煤灰中不含氯化钙（CaCl_2），而含有CaClOH， CaClOH是Ca(OH)_2与HC1反应的产物，NaOH加热后的试样中检测到氯化钠（NaCl），莫来石处理后的试样中检测到瓦达石。差热分析表明，对于没有添加剂的样品，在冷却步骤中有一个放热峰（约800℃）。而在添加添加剂的情况下没有检测到这个峰值。进一步分析了修复前后样品中的dxn。结果表明，添加添加剂后样品中DXNs浓度下降幅度小于1/！05，与未添加添加剂的相比。这些结果证实了这些添加剂的应用不仅具有防止粉煤灰凝固的优势，而且还具有促进DXNs分解的优势。少

The present work is aimed at developing a method for suppressing the formation of dioxin (DXN)s emitted from small-scale incinerators for industrial wastes, which are difficult of operate under well controlled combustion, by adding a chemical (sulfur-contained titania) into incinerators. In the first year, the lab-scale experiments on incomplete combustion of me waste samples prepared by adding hydrated lime (Ca(OH)_2) with a given content into PVC powders were performed. The experiments revealed that the DXNs concentration in the burnt samples with 33.2wt%-added Ca(OH)_2 decreased by about 1/10 compared to that without the addition. However, we concluded that this technique adding chemicals into an incinerator is insufficient for the future regulation of tolal emission even if titania, which might be more reactive than Ca(OH)_2 is applied. Thus, we focused on the secondary heat treatment for fly ash in which DXNs arc most concentrated. In the conventional method, DXNs in the fly ash a … More re dechlorinated under reductive atmospheres below 500 deg. C. by adding some chemical since fly ash is subject to solidification above 500 deg. C. In the second year, we investigated the mechanism on solidification of fly ash at the high temperature and attempted to establish the technique of high-temperature treatment for fly ash preventing it from the solidification. Sodium hydroxide (NaOH) and mullile were chosen as an additive that can trap chlorine in fly ash, assuming that it might contribute the solidification, and then me chosen chemical was mixed with fly ash at a given ratio, followed by heating in an electric furnace at 700 deg.C. It was found that no solidification of fly ash with the additives took place after the heat treatment. Moreover, the X-ray diffractometer analyses indicated that the fly ash prior to the heating did not contain calcium chloride (CaCl_2) but CaClOH, which was a product of reaction between Ca(OH)_2 and HC1, and that sodium chloride (NaCl) was detected in the heated sample with NaOH and wadalite in the treated one with mullitc. The differential thermal analyses revealed that for the sample without additives there was an exothermic peak in ihe cooling step (around 800 deg.C). while this peak was not detected in that with additives. Furthermore, the DXNs in the samples before and after the heal treatment were analyzed. The results showed that DXNs concentration in the treated samples with additives decreased by less than 1/!05 compared to the untreated one without additives. These findings confirmed that the application of these additives has the advantages not only to prevent fly ash from the solidification but also to enhance the decomposition of DXNs. Less