Collection Efficiency of Acidic and Basic Gases of the Porous Metal-Disc Denuder

• Main Authors: Si Ho Wang, 王斯厚
• Other Authors: Chuen Jinn Tsai
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/07687623185217196553

碩士 === 國立交通大學 === 環境工程所 === 87 === The porous metal disc in the personal denuder sampler is used to sample the acid and alkaline gases. According to the study, the disc of 100 mm in nominal pore size, 0.317 cm in thickness is suitable for acidic gas sampling. In addition to the porous metal disc, two different media: silica gel tube and impinger were tested for comparing the gas collection efficiency and collection capacity at the gas concentration of 2 PEL, and the testing condition is 80% relative humidity and 30℃ temperature. The test data indicate that the gas collection efficiency is between 90% and 100% for three sampling media for 4 hr sampling period, and the adsorbing capacity is sufficient for the gas sampling in the workplace. The gas collection efficiency of porous metal disc is the highest compared to the first section of the silica gel and the first impinger. Using 5% sodium carbonate/glycerin coating on the porous metal disc, the collection efficiencies for HNO3、HCl、HF are 91±0.9%、95±1.5% and 100±0.4%, respectively. In comparison, the collection efficiencies of the silica gel for these gases are 105±1.8% (1st section: 98±0.6%, 2nd section: 7±1.3%), 103±4.1 % (1st section: 99±0.2%, 2nd section: 4±3.9%); and 101±0.4% (1st section: 95±0.1%, 2nd section: 6±0.2%); and those for the impinger are 96±0.9% (1st impinger: 66±0.4%, 2nd impinger: 30±0.6 %), 98±1.6% (1st impinger: 86±1.2%, 2nd impinger: 12± 0.4%) and 101±0.5% (1st impinger: 92±0.4%, 2nd impinger: 9±0.2%), respectively. The collection efficiency for NH3 for the porous metal disc with 4% citric acid coating is 96±1.8%, and for the impinger is 99±3.6% (1st impinger: 95±0.1%, 2nd impinger: 4±3.2 %). The residual inorganic ion on the silica gel tube was found to be high, which explains why the overall collection efficiency of the silica gel can sometimes be higher than 100 %. Because of their high boiling point and low volatility, sulfuric acid and chromic acid generated in the laboratory were found to exist as mist particles. The collection efficiencies of both inorganic acids are near 100% for the porous metal disc. The collection efficiencies of both silica gel tube and impinger for sulfuric acid are over 97%, but most of the mist was found to be collected on the small PVC filter in front of the silica gel tube. To sum up, the personal denuder sampler outperforms the tradition samplers for acidic gas sampling in the workplace. With its compact size and capability to sample gases and particles simultaneously in the workplace, it is worthwhile to promote its use domestically and internationally.