Flashcards
Sustainability Unit 7
Cards in this deck (50)
- 1Criteria PollutantsCO, NOX, VOC, SO2, Pb, Particulates
- 2CO, NOX, VOCs plus sunlight equals BLANKphotochemical smog
- 3Some indoor air quality issues aretobacco smoke, radon, asbestos, off-gassing
- 4BLANK are emitted directly into atmosphere, e.g., CO, SO2, NOX BLANK are formed by chemical reaction in the atmosphere, e.g., O3, a product of photochemical reactions between VOCs and NOX, both primary pollutants.Primary pollutants
Secondary pollutants - 5Sources of Primary Pollutants areCombustion, evaporation, and grinding
- 6first federal effort to control air pollution; prior to this had been state & local issue (under nuisance laws)Air Pollution Control Act (Clean Air Act)
- 7Set acceptable concentrations of pollution in the atmosphereNational Ambient Air Quality Standards
- 8Criteria for acceptable concentrations of pollutionPrimary
Secondary
six criteria pollutants
Compliance with CAA - 9Set allowable rates at which pollutants can be released from a source.Emission Standards
- 10Future deterioration of attainment areas was limited depending on the BLANK of areaClass
- 11Based on NAAQS; used by US metro areas for public reporting of overall assessment of particular day’s air qualityAir Quality Index
- 12An AIQ over BLANK is rare, and an AIQ over BLANK is an emergency200
400 - 13Sources and Health affects of CO are BLANK and BLANKTransportation
Asphyxiant - 14Most important as air pollutants are BLANK and BLANKNO and NO2
- 15Unburned hydrocarbons from tailpipes and stacks after incomplete combustion of fossil fuels; also from evaporation of solvents, fuelsVOCs
- 16May range from 0.005 to 100 μm in size. Size, composition, concentration all important. Aerosol, dust, fumes, fog, smoke, soot, mist, smog. Most important size range is BLANK to BLANKPM
0.1 to 10 μm - 17maximum constant velocity at which the sphere falls through a fluid of constant density and viscosity (in our case air) when the downward gravity weight force acting on the sphere is just balanced by the upward drag force on it.Settling Terminal Velocity
- 1886% from combustion of fossil fuels in stationary sources, most from electric power plantsSulfur Oxides
- 19Today in the US most BLANK comes from point sources—mining, smelters, lead-acid battery plants, old flaking paintLead
- 20BLANK, i.e., species known to be “carcinogens, mutagens, teratogens, neurotoxinstoxic air pollutants
- 21PM (TSP) is highest in BLANK —more burning of solid fuel, one and two cycle engines, no emission controls, leaded gasoline. BLANK is highest in Chinese cities, Mexico City, Seoul. BLANK is highest where there are lots of cars for commuting—LA, Tokyo, Sao Paulo, Mexico City.developing countries
SO2
O3 - 22Rise in popularity/sales of SUVs and light trucks caused the combined CAFÉ value to drop to BLANK in the 1990’s and the 2006 actual average mpg for light-duty vehicles was only BLANK using the newer “more realistic” fuel efficiency model25 mpg
21 mpg - 23Cycle where Air to fuel ratio in the intake stroke determines emissionsOtto
- 24Cycle that is more polluting than 4-stroke because oil must be mixed with gasoline during combustion—oily, smelly exhaustTwo Stroke
- 25Do not use spark ignition, can run on leaner fuel-air mixtures, inherently more fuel efficient in CO and HC emissions. Higher temperatures cause more thermal NOX emissions which cannot be converted using conventional catalysts which require low oxygenDiesel
- 26BLANK used for after burner for CO and HC. Requires rich fuel mixture so that some is available to sustain combustion in the exhaust manifoldThermal Reactors
- 27BLANK oxidizes CO, HC while reducing NOX to N2 all in the same catalyst bed.Catalytic Converter
- 28The oxygen in the fuel provides “extra oxygen” to aid complete combustion of the gasoline. One of the ways to make cleaner gasoline. Examples are BLANKMBTE
- 29burns at lower temp so reduces NOX; burns more completely so reduces HC and CO; but emissions are high in formaldehyde; low volatility makes it hard to start in coldMeOH
- 30Made from vegetable oil, animal fat, waste cooking oil, etc. Biodegradable. Net CO2 emissions about 0.25 of petroleum diesel, as well as reduced other emissionsBiodiesel
- 31used for fleet vehicles in some countries; clean, low emissions of all criteria pollutants except NOX; problems with fueling sources, also large tanks needed for comparable rangeCNG
- 32used in fleet vehicles; again NOX higher, other criteria pollutants lower or same; similar problems in fueling as with CNG. CO2 higher or lower depending on sourceLPG
- 33Very clean, main product of combustion is water but also thermal NOX possible from N2 in the air; however BLANK must be produced from a fossil fuel source so the net is not cleanhydrogen
- 34• Responsible for ~90% of SOX and 50% of NOX and PM in US. • Most released at electric power plants as result of coal combustionStationary Source Emissions
- 35• Fossil fuel substitutes: (6)solar, wind, hydroelectric, geothermal, tidal and nuclear fuel sources
- 36Two types of Pre combustion controlsFuel Switching
Coal Cleaning - 37Crushed coal and limestone are suspended in air rising from the bottom of the bedFluidized-bed Combustion
- 38• First gasify the coal, using steam, to CO and H2; clean up this syngas and then burn it in a high efficiency gas turbine; waste heat from the gas turbine powers a conventional steam cycle to generate more electricityIntegrated Gasification Combined Cycle
- 39Four ways to lower NOx combustion1. Low excess air 2. Two Stage Burner
3. Limestone Injection Multistage Burner 3. Selective Catalytic Reduction - 40Cons of scrubbers areexpensive, use lot of water, up to 5% of there energy is wasted, generates lots of sludge
- 41Three types of particulate control arecyclones
electrostatic precipitates
Baghouses - 42Air quality at a given site is strongly influenced by the weather—wind and its velocity, temperature, sunlight, precipitation dynamics of the atmosphere or BLANKmeteorology
- 43The temperature change per unit altitude caused by moving a parcel of dry air up or down in the atmosphere• Dry Adiabatic Lapse Rate
- 44lapse rate allowing for moisture content of the air; varies with moisture content of the air which is function of temp• Saturated Adiabatic Lapse Rate
- 45Lapse rate in the real atmosphere is different from the dry adiabatic lapse rate because of , BLANK BLANK BLANK etc., in the real atmosphere, all of which can contribute to atmosphere stability/instability and vary the lapse ratewind speed, sunlight, terrain
- 46If the ambient lapse rate causes cooling BLANK than the dry adiabatic lapse rate then the atmosphere is absolutely unstable; air will continue to move up to a higher altitude and vertical dispersion of pollutants is BLANKfaster
enhanced - 47BLANK is an extreme case of a sub-adiabatic lapse rate where the ambient temperature increases with altitude causing a very stable stratosphere that can trap pollutants for a long timeTemperature Inversion
- 48A summertime phenomenon occurring at higher elevations in the atmosphere and lasting longer than radiation inversions (in extreme cases can last days to months) and known as anticyclones• Subsidence Inversions
- 49BLANK is the altitude at the top of this near ground level mixing zone. The product of mixing depth and wind speed, the BLANK, may be used as an indicator of the atmosphere’s ability to disperse pollutantsMixing depth or height
ventilation coefficient (m2/s) - 505 types of smokestack plumesConing
Looping
Fanning (small looping)
Fumigation (coning with constant max)
Lofting (coning with constant min)
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- Flashcards on Sustainability Unit 7, created by amsond01 on 22/10/2015.
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