http://physics.colorado.edu/phys3070Sulfur Dioxide“Natural” sulfurAtmospheric processesReducing Sulfur DioxideReducing Sulfur DioxideReducing Sulfur DioxideWaste productsOlder generating stations1990 Clean Air Act1990 Clean Air ActRules for older plantsRules for older plantsOther solutionsAcid RainMeasure of acidityParticulates (aerosols)Particulates (aerosols)ProblemsRemoving particulatesWorst and best citiesCurrent situationJudah Levine, 3070L36 1http://physics.colorado.edu/phys3070http://physics.colorado.edu/phys3070Judah LevineJudah LevineJILA SJILA [email protected]@colorado.edu303 492303 492--7785 (27785 (2--7785)7785)M,F 11M,F 11--Noon, W 1Noon, W 1--3 pm3 pmalso by appointmentalso by appointmentJudah Levine, 3070L36 2Sulfur DioxideSulfur DioxidePrimary source is burning coal:Most coal has at least some sulfur (1%+)Eastern coal has 3+%Judah Levine, 3070L36 3““NaturalNatural””sulfursulfurHydrogen sulfide (H2S)Decay productSulfates in ocean sprayaerosols with relatively short lifetimeSimilar quantity by volume by usually less serious in practiceJudah Levine, 3070L36 4Atmospheric processesAtmospheric processesSulfur dioxide combines with water vapor to produceSulfuric acidSulfur dioxide condenses on atmospheric particulatescarried by the wind for great distancesSulfur dioxide and sulfuric acid combine with carbonatesand silicates to form water-soluble sulfatesJudah Levine, 3070L36 5Reducing Sulfur DioxideReducing Sulfur DioxideLow-sulfur coal in Wyoming– less sulfur but less energy by weightnet decrease may be smallMimic atmospheric process in the smoke stackJudah Levine, 3070L36 6Reducing Sulfur DioxideReducing Sulfur DioxideMimic atmospheric process in the smoke stack:Spray exhaust with water: Converts SO2to H2SO4(sulfuric acid)Add limestone (calcium carbonate)yields calcium sulfate + water + CO2Judah Levine, 3070L36 7Reducing Sulfur DioxideReducing Sulfur DioxideMimic atmospheric process in the smoke stack:Spray exhaust with water: Converts SO2to H2SO4(sulfuric acid)Add limestone limestone (calcium carbonate)yields calcium sulfate + water + CO2Exhaust is cold and must be re-heated to rise.Requires 5%+ of the energy outputIncreases capital construction cost by 10+%Judah Levine, 3070L36 8Waste products Waste products Slurry consists of:Calcium sulfateSulfuric acidWaterWhat to do with this stuff?No good solution for dealing with acid slurryJudah Levine, 3070L36 9Older generating stationsOlder generating stationsShould older plants be retro-fitted with scrubbers? About 50% of plants were built before 1975Rates for electricity were set based onan assumption about station lifetimeJudah Levine, 3070L36 101990 Clean Air Act1990 Clean Air ActBy 2000: Reduce SO2emission by 50% from 1990 levelsNew EPA rule in 2005 for Eastern states: Reduce emissions or buy allowancesEmission limits based on generated powerCleanest plants can sell allowances to dirtiest onesJudah Levine, 3070L36 111990 Clean Air Act1990 Clean Air ActBy 2000: Reduce SO2emission by 50% from 1990 levelsShould oldest/dirtiest plants continue to operate?No – they violate the clean air actYes – they should be allowed to buy allowancesuntil they are modernizedStrong dis-incentive to modernizeJudah Levine, 3070L36 12Rules for older plantsRules for older plantsForce conversion to natural gasIs this a better solution?Judah Levine, 3070L36 13Rules for older plantsRules for older plantsForce conversion to natural gasIs this a better solution?Yes: sulfur dioxide and acid rain are serious problemsNo: solve a short-term problem and make a longer-termoneJudah Levine, 3070L36 14Other solutionsOther solutionsRemove sulfur before the coal is burnedRemove the sulfur dioxide in the boiler Fluidized bed combustionStill have to deal with the sulfurVolume of waste material can be larger thanoriginalJudah Levine, 3070L36 15Acid RainAcid RainSulfuric Acid from Sulfur DioxideNitric Acid from NOxWhat goes up, comes downSomewhere elsePrevailing winds carry materialNorth and EastJudah Levine, 3070L36 16Measure of acidityMeasure of acidityH2O+CO2pH value: Each unit is factor of 10 in concentrationJudah Levine, 3070L36 17Judah Levine, 3070L36 18Adirondack LakesJudah Levine, 3070L36 19Particulates (aerosols)Particulates (aerosols)Particles smaller than about 100 µm (10-4m)Natural sources: wind-blown dust, fog, …Produced during combustion of coalParticles scatter light, but too small to see individuallyJudah Levine, 3070L36 20Particulates (aerosols)Particulates (aerosols)Buoyant force proportionally much larger than for larger particlesSettling velocity < 0.1 m/sParticles remain suspended in the air for daysor longerJudah Levine, 3070L36 21ProblemsProblemsParticles scatter sunlight, reduce intensity onthe groundSmallest particles are most likely to enter lungsParticles can pick up sulfates and nitrates –can be another form of “acid rain”Judah Levine, 3070L36 22Removing particulatesRemoving particulatesMechanical filtersElectrostatic precipitatorsSmall particles become chargedOften combined with scrubbers forsulfur removalJudah Levine, 3070L36 23Worst and best citiesWorst and best citiesLos Angeles: About at legal limitWorst:Beijing, Calcutta: 7X Los AngelesMexico City: 6X Los AngelesBangkok, Bombay: 5X Los AngelesBest:New York, London, Paris: about 50% of Los AngelesJudah Levine, 3070L36 24Current situationCurrent
View Full Document
Unlocking...