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Formation and Decomposition Mechanisms of Dioxins in High Temperature Packed Bed Processes

高温填充床过程中二恶英的形成与分解机理

基本信息

批准号：
11650756
负责人：
KASAI Eiki
金额：
$ 2.3万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

In 1999, an experimental apparatus of a packed bed reactor with gas flow was made which has a gas supplying system quantitatively controlling the concentration of chloro-benzenes or chloro-phenols of the main gas. A number of interesting results were obtained, e.g., the peak of dioxins formation is observed at about 300℃ and about 2% of O_2, and formation rate of highly chlorinated dioxins promoted by the HCl addition to the gas through the bed.Based on the above results, in 2000, the packed bed combustion process was first applied to the remediation of soils highly contaminated by dioxins. The validity of the process was verified using a laboratory-scale simulator on the bases of process efficiency. The sample was soil contaminated by dioxins (13,100 pg/g-dry soil, 330 pg-TEQ/g-dry soil) and different conditions, e.g., admixing ratios of coke, limestone and water for pre-granulation, were examined. The results showed that high efficiencies of dioxins removal (more than 98.9% of removal ratio) were obtained in all conditions. Further, pretreatment soils such as pre-drying and pre-granulation can give extremely high efficiencies, i.e., more than 99.9%.Further, quenching experiments were conducted to observe in detail the transport phenomena of dioxins and relating compounds in the bed during combustion. The macroscopic phenomena of dioxins removal with the proposed process was clarified.

1999年制作了气流填充床反应器实验装置，该装置具有定量控制主气体中氯苯或氯酚浓度的供气系统。得到了许多有趣的结果，例如，在约300℃和约2%O_2时观察到二恶英的形成峰值，通过床向气体中添加HCl促进了高度氯化二恶英的形成速率。基于上述结果，2000年，填充床燃烧工艺首次应用于二恶英高度污染的土壤修复。使用实验室规模的模拟器基于流程效率验证了该流程的有效性。样品是被二恶英污染的土壤（13,100 pg/g-干土，330 pg-TEQ/g-干土），并检查了不同的条件，例如用于预制粒的焦炭、石灰石和水的混合比例。结果表明，在所有条件下都获得了较高的二恶英去除效率（去除率超过98.9%）。此外，对土壤进行预干燥、预造粒等预处理，处理效率极高，可达99.9%以上。此外，还进行了淬火实验，详细观察了燃烧过程中二恶英及相关化合物在床层中的迁移现象。阐明了所提出的工艺去除二恶英的宏观现象。