文档介绍：1 ? VOCs are liquids or solids that contain organic carbon (carbon bonded to carbon, hydrogen, nitrogen, or sulfur, but carbonate carbon as in CaCO 3 nor carbide carbon as in CaC 2 or CO or CO 2 ), which vaporize at significant rates. ? Some VOCs (., benzene) are toxic and carcinogenic, and are regulated individually as hazardous pollutants. 2 ? Most VOCs are believed not very toxic to humans. ? Our principal concern with VOCs is that they participate in the “ smog ” reaction and also in the formation of secondary particles in the atmosphere. ? Some VOCs are powerful infrared absorbers and thus contribute to the problem of global warming. 3 ? Next slide (Table ) The estimated . emissions of VOCs for 1997. 5 ? Most VOC emissions are of refined petroleum products, use as fuels or solvents. ? The total emissions shown in Table are roughly 2% of the total petroleum usage in the . 6 1. Vapor Pressure, Equilibrium Vapor Content, Evaporation ? To understand which chemicals are volatile we must consider the idea of vapor pressure. ? Fig. (next slide) shows vapor pressures as a function of temperature for a variety pounds. 8 ? From , at 212 o F, water ’s normal boiling point, water has a pressure of psia (=760 torr = 1 atmosphere = kPa ≈ psia). ? At room temperature (68 oF = 20 o C) the vapor pressure of water is psia = torr = atm. 9 ? At this temperature water does not boil but it does evaporate if the surrounding air is not saturated. ? The vaporization behavior of volatile liquids is summarized in Table (next slide).