Gas-phase oxidation of odorous compounds emitted fromhot melting of asphalt

• Main Authors: Yi-Jyun Liou, 劉怡君
• Other Authors: Ming-Shean Chou
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/68756976421316974990

碩士 === 國立中山大學 === 環境工程研究所 === 103 === Hot-melted asphalt (HMA) plants use asphalt, recycled asphalt and gravels as raw materials and blend them at around 170 oC. Fumes and particulates emit from the process equipments in the asphalt melting and blending operations. Most of the particulates and the aerosols in the fumes can be removed by bag filters, however, gaseous volatile organic compounds (VOCs) and reduced-sulfur compounds can''t be effectively removed from the fumes. These gaseous compounds have peculiar smells and may be harmful to the nearby residents. Complaints also come with the odorous emissions. In this study, gaseous phase reactions were tried for the oxidation and removal of the odorous compounds (alkenes, aliphatic and aromatic hydrocarbons) emitted from heated asphalt. Hypochloric acid (HOCl) was used as the gaseous oxidant and solid sodium thiosulfate or activated carbon was used as a chlorine-reducing agent following the oxidation reaction. A portable flame ionization detector (FID) was used for the detection of total hydrocarbon carbon (THC) concentrations in the gas before and after the oxidation and reduction reactions. A sensory test was used to examine the gas odor. Results indicate that at a reaction temperature of 100oC, with initial chlorine concentrations of 2 and 4 ppm and a gas residence time of 1.73 s, odor intensities of the influent gas could be reduced from 7,330 (expressed as dilutions to threshold) to less than the regulation of 1,000 for exhaust gas from an emission pipe with a height of lower than 18 m above ground, as set by the EPA of Taiwan. An estimation indicates that the chemical cost is around USD 0.023 for scrubbing 1,000 Nm3 of the exhaust gas.