影響活性碳濾毒罐效能因子評估研究

Abstract

Charcoal cartridges are commonly used to protect against a wide range of organic vapors in the workplaces. The service life of charcoal cartridge has been found to be affected by many factors, including assault agent, concentration, temperature, humidity and flow rate through the cartridges. Therefore, a filter unit was normally placed in front of the cartridges to protect the charcoal from contamination. However, in the practical situation, organic vapors often accompany aerosol particles. Due to the air resistance caused by the filter media, the filter units equipped in the cartridge or canister are seldom “absolute filter”, especially for respirators designed for negative pressure mode. Therefore, principal objective of this work was to study the effect of aerosol loading on the breakthrough characteristics of charcoal cartridges, as a function of particle size. A stainless holder (diameter 71.6 mm, height 25.6 mm) will be fabricated to accommodate 35.0 g of activated charcoal made of coconut shell. The charcoal powder has the BET surface area of about 1300 m2/g. Cyclohexane will be used as the assault agent. Cyclohexane vapor concentration will be controlled at 3000 ppm by passing an air flow of 15 L/min through surface of liquid cyclohexane in a jar dipped in a water bath. A flame ionization detector will be used to monitor the organic vapor concentration. A syringe pump will be used to refill the escaped cyclohexane. The relative humidity will be controlled at 50% by using a tubing pump feeding water into a needle wrapped with a heating tape. The same can of charcoal will be regenerated in a 150 C oven to remove the absorbed cyclohexane. The pressure drop across the charcoal cartridge will be monitored by using a pressure transducer, which will be calibrated against an inclined manometer. For aerosol penetration test, a constant output aerosol generator (model 3075, TSI) will be used to generate submicrometer-sized aerosols, and an ultrasonic atomizing nozzle (model 8700, Sonotek) will be used for generating micrometer-sized aerosols. An electrospray aerosol generator will be used to generate nanometer-sized particles to study the loading effect on the breakthrough characteristics of charcoal cartridge. A scanning mobility particle sizer (for aerosols < 0.7