Charcoal-adsorption air purification system for chamber studies investigating atmospheric photochemistry
An air purification system has been designed and constructed to furnish the very pure matrix air required for environmental chamber studies of photooxidations of very low concentrations of hydrocarbons and nitrogen oxides. The system furnishes air containing a few parts per billion carbon (ppbC) or less of individual organic impurities and nitrogen oxides. Methane is an exception but is reduced to less than half the natural background level, more than sufficient for chamber studies. Carbon monoxide is reduced to less than 1% of its ambient concentration. In this system air is drawn through Purafil beds, compressed by a liquid (water) ring compressor to 100 psig, and passed successively through a heatless dryer, a Hopcalite tower, and a second heatless dryer packed with activated coconut charcoal. The yield is a purified air stream that is approximately 20% of the inlet flow or typically 12 to 15 scfm. The extremely dry pure air can be rehumidified up to approximately 90% RH and brought to any desired temperature between 55 and 122/sup 0/F prior to being admitted to either of two 6000-l. irradiation chambers. The system has been in daily operation for three years with only routine maintenance and recharging of filter beds.