Effects of Thermal Desorption on Removal Effectiveness of Mercury and Dioxin Contaminants

• Main Authors: Shing-Yi Li, 李欣怡
• Other Authors: 席行正
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/4g4bqr

碩士 === 國立臺北科技大學 === 環境工程與管理研究所 === 100 === This study examines the effectiveness of thermal desorption of CPDC’s contaminated soils using a bench-scale column reactor and a pilot-scale rotary reactor. The test parameters include desorption temperature, duration, and carrier gas flow rate. bench-scale column reactor is used to preliminarily understand the thermal parameters of soils. Four soil samples (A, B, D, E) contained various amounts of Hg and PCDD/Fs were then tested for their desorption properties at 350, 450, 500, 550, 700 and 800℃. The resulting physical and chemical properties and distribution of mercury fractionations and dioxin profiles were then accessed. The experimental results showed that the soil pH changed from neutral or weak basic into a strongly basic. Soil organic matter content decreased with elevating the desorption temperature. At all of the test temperatures, Hg concentration can be reduced to < 20 mg kg-1, the soil standard by Taiwan EPA, from the concentrations between 6.7–480 mg kg-1. The TEQ of PCDD/Fs at 500℃ for 0.5 hr after treatment reduced to < 1000 ng I-TEQ kg-1. High chlorine PCDD/Fs dechlorination decomposition to low chlorine PCDD / Fs at law temperatures (350, 450). OCDD and OCDF were the major dioxin homologues in the soils, before and after thermal desorption. Mercury fractionation examinations showed that mercury was mainly in residual form before and after thermal desorption. These results suggested that the bioavailability of mercury in the contaminated site was relatively low. Considering reutilization of thermally treated soil, a lower desorption temperature can be tested on the targeting soils to save energy under the direct-heating desorption operations. This study provided a better comprehension in the repartitioning of these contaminants in soil. Results presented here may provide useful suggestions for the scale-up thermal treatment processes in the future.