Air Pollution Control Devices - continued CE 326 Principles of Environmental Engineering Prof. Tim Ellis January 30, 2009
Air Pollution Control Devices A tower B C Separator ad Bed E precipitator V scrubber
Electrostatic Precipitator w in t or wire and p configurations wet or dry, wet cleaned by w s, dry by rapping, can be cleaned while in service c wire imparts an electrical l charge (neg), particles are attracted to charged (pos) collecting plates high p removal efficiencies possible
Venturi Scrubber velocity of gas is a by a factor of four in the throat section where nozzles inject water or solution high velocity causes a of liquid pressure drop following the t section creates a lot of turbulence resulting in good intermixing requires s (e.g., cyclone) following venturi to collect particles and liquid
T Incineration
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Air Pollution Control Devices: Mobile Sources
Automotive Emissions M sources contribute approximately 60% of total air pollution (78% of CO, 47% of NO X, 44% of total hydrocarbons, 5% of particulates, and 2% of SO X 20 to 40% of the automobile's total hydrocarbon emissions are from the crankcase. This emission is called b. function of s after 1963 all vehicles are required to have a positive crankcase ventilation (PCV) valve the PCV valve opens up more at h speeds to allow more crankcase fumes to be sucked into the intake manifold
Fuel tank e As the fuel tank warms, the vapors in the headspace are exhausted through the vent line. activated carbon canister vent the fuel tank to the crankcase
Carburetor Losses After the engine is shut off, the gas in the float valve evaporates to the atmosphere. This is called h s activated carbon canister vent to the crankcase
Engine Exhaust. E modifications F system modifications E system modifications: catalytic converter for NO X and HC control platinum-rhodium or platinum-palladium palladium catalyst t - requires temp of 350 C (660 F) NO + CO + HC N 2 + CO 2 + H 2 O
Reformulated Gasoline 1990 Clean Air Act Amendments had two performance targets for reformulated gasoline: 15% r in VOCs 15% reduction in a t (e.g., benzene)
Reformulated Gasoline one third of U.S. uses r gasoline Congress mandated that reformulated fuel contains 2% o
Common Oxygenates M E fermented from c MTBE (methyl tertiary ti butyl ether) derived from natural gas and c ETBE (ethyl tertiary butyl ether) derived from
Air Pollution Meteorology CE 326 Principles of Environmental Engineering Prof. Tim Ellis February 2, 2009
Announcments If you missed part of last week s field trip, the video from last year is posted on the course website. First exam is scheduled for 2/13/09 Lab class this week will be in the lab classroom (230 TEB section 1 and 250 TEB section 2)
Atmospheric Engine atmospheric s (and weather) is a function of t and p wind flows from h pressure areas to l pressure areas in absence of earth s rotation, wind would be p to constant pressure lines (i ) earth s rotation creates C effect
Atmospheric stability tendency of atmosphere to r or e vertical air movement is termed s there are three categories of stability depending on the l r rate of temperature change as a function of elevation neutral d a l r unstable s lapse rate stable s lapse rate isothermal no change in t with elevation i temperature increases with elevation
Atmospheric Looping stability Coning Fanning Lofting Fumigation
H I E Terrain Effects mass of material that a and e heat at a greater rate than surrounding area stability over heat islands sa is l good for g l sources bad for t s
Land/Sea Breeze land c more rapidly at night than sea l breeze land h faster during day s b land
Valleys valleys at an a a to the prevailing wind will direct a portion of wind into the valley valleys oriented in the n - s direction are more susceptible to inversions than east-west direction during daytime sun heats valley floor v breeze during night h breeze early day i possible
How do we predict the dispersion of air pollutants? t