多孔金屬型固氣分離器對酸鹼氣體之收集效率研究

Abstract

本研究利用多孔金屬片、矽膠管、吸收瓶等採樣介質來進行不同酸鹼氣體的吸附效率與容量實驗，測試氣體濃度為2 倍之容許濃度(PEL, Permissible Exposure Limit)，溫度為30±3 ℃，相對溼度(RH, Relative Humidity)為80±5 %。結果顯示多孔金屬片的氣體吸附效率與吸附容量和矽膠管(內有兩段矽膠)，及兩段吸收瓶相當，在測試氣體濃度為2 PEL，測試時間為4 hr時，三種採樣介質的吸附效率或吸收效率均在90-100 % 之間，且有足夠的吸附容量來作為作業環境測定之用。但若只考慮矽膠管前段及第一個吸收瓶時，本研究所設計之多孔金屬片的吸附效率及容量則均明顯的高於前述兩種採樣介質。當採樣時間4 hr，氣體濃度2 PEL，多孔金屬片塗敷5% Na2CO3對HNO3、HCl、HF的採集效率分別為91±0.9%、95±1.5%、100±0.4%，矽膠管與吸收液採集效率則為105±1.8%(前段98±0.6%，後段7±1.3%)、103±4.1%(前段99±0.2%，後段4±3.9%)、101±0.4%(前段95±0.1%，後段6±0.2%)與96±0.9%(前瓶66±0.4%，後瓶30±0.6%)、98±1.6%(前瓶86±1.2%，後瓶12±0.4%)、101±0.5%(前瓶92±0.4%，後瓶9±0.2%)。另外，多孔金屬片塗敷4% 檸檬酸(citric acid)時對NH3的採集效率為96±1.8%，吸收液效率為99±3.6% (前瓶95±0.1%，後瓶4±3.2%)。作採樣介質背景值實驗時，可以發現矽膠管均存在各離子背景濃度(無機酸)，因此有時會造成矽膠管前後段的收集效率和高於100%的現象。 在硫酸與鉻酸吸附實驗方面，因兩者的沸點很高，分別為300℃與250℃以上，測試時發現兩種物質均會以液滴而非以氣體形式存在，測試結果發現硫酸被多孔金屬片收集的效率大於100%，前段吸收瓶與前段矽膠管採集效率均逾97 %，但大部分硫酸液滴均過濾在矽膠前段之小片PVC濾紙上；鉻酸被多孔金屬片收集的效率亦比100%高，前段吸收瓶採集效率超過79 % (若合計則兩段吸收瓶將近100%)，PVC濾紙有99.5 %以上。 綜上所述，本研究所設計之多孔金屬片個人採樣器的效率及性能優於傳統採樣器，且因體積小故可以同時做酸鹼液滴及氣體之作業環境測定之用，應可在國內外逐漸推廣使用。

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.