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1、Reduction of VOC Emissions from Paint-Booth Operations Using Dielectric Barrier Discharge30th Environmental and EnergySymposium&ExhibitionSan Diego,CAApril 7,2004Gregory D.HollandJohn N.VeenstraArland H.JohannesGary L.FoutchFreddie Hall,BackgroundThe Oklahoma City Air Logistics Center(OC-ALC)conduct
2、s surface coating as regulated by 40 CFR 63.741 in maintenance paint booths at the facility.Volatile Organic Compounds(VOCs)are emitted as a result.While the emissions rate is currently well below the stationary major source threshold of 10 tons per year,these low emissions are the result of using l
3、ow-VOC/low-solids paints.,BackgroundThe low-VOC/low-solids paint has performed and weathered poorly,and as a result,the planes require more frequent painting as well as constant touch-ups.An efficient method of emission treatment is desired to enable renewed use of the better performing high-VOC/hig
4、h-solids paints.,BackgroundThe typical emissions control technique for surface coating spray booths is carbon absorption(average control efficiency=90%).Carbon absorption has a fire potential in the carbon bed when high concentrations of ketones and alcohols are present as at TAFB.Furthermore,the pa
5、inting operations at TAFB are not continuous but are of short duration.Due to this operational pattern,a technology with an“instant-on”,”instant off”capability without a concurrent step-up in emissions would be the most efficient treatment for TAFB.,BackgroundTAFB has commissioned the investigation
6、of an innovative technology to meet plant and regulatory requirements.A Gas Phase Corona Reactor(GPCR),also known as a dielectric barrier discharge(DBD)or non-thermal plasma(NTP)reactor,is being designed to reduce VOC emissions from painting operations.,Project GoalsEstablish optimum operating condi
7、tions using bench-scale studies.Test capacity limits for design and cost of full-scale equipment.Collect statistically significant data to verify VOC destruction and determine operating costs.Two week operation test at Tinker AFB with greater than 90%removal of VOCs from stack exhaust.,Project Phase
8、sPhase I:Investigate operation of different reactor geometries.Verify destruction capabilities.Investigate operating variables using single-tube,bench-scale reactors.Phase II:Design pilot-scale reactor for 1,000 scfm(multi-tube design)and demonstrate unit at TAFB.Develop technology demonstration pla
9、n.Phase III:Test 1,000 scfm unit.Determine economic and scale-up factors for the plasma unit.Design full-scale reactor for 20,000 cfm.,Plasma Discharge ProcessHigh electric fields are used to generate high energy electrons(up to 10 eV)which collide with the gas molecules to create highly reactive io
10、ns and/or free-radicals.The dielectric barrier prevents the direct flow of current and prevents excess heating.Essentially no warm-up period required,allowing“instant on”capability.“On-the-fly”adjustment of power to handle variation in VOC loading,Dielectric Barrier Discharge,Phase IInvestigate oper
11、ation of different reactor geometries.Verify destruction capabilities.Investigate operating variables using single plasma zone,bench-scale reactors.,Target components:TolueneMethyl Isobutyl KetoneButyl AcetateSec-Butyl AlcoholMethyl Propyl KetoneEthyl 3-Ethoxypropionate1,6-Hexamethylene Diisocyanate
12、Gas MixtureActual Stack Gas,Operating variables:Reactor geometryRound,square,plateElectric field strength16-18 kVDischarge frequency200-400 HzResidence time0.05-0.2 secondsVOC concentration35-250 ppmHumidity0-80%relative humidity,Flat Plate Reactor,Square Tube Reactor,Single Tube Reactor,Single Tube
13、 Reactor,Figure 3.Plot of destruction data(as concentration)for V”=17 kVrms,f=300 Hz,tres=0.1 second,and rh=0%(Run#04).,Figure 4.Plot of destruction data(as a fraction of inlet conc.)for V”=17 kVrms,f=300 Hz,tres=0.2 second,and rh=70-80%(Run#40).,Phase I ResultsReactor geometry:Single dielectric bar
14、rier,annular gap.Electric field strength:Greater destruction at higher electric field strengths.Discharge frequency:Greater destruction at higher discharge frequencies.Residence time:Greater destruction efficiency at higher residence times.VOC concentration:Greater destruction efficiency at higher c
15、oncentrations.Humidity:Improves destruction efficiency of some components,reduces destruction efficiency of others.Humid conditions improve overall destruction efficiency.May increase energy requirements.,Phase IIDesign pilot-scale reactor for treating 1,000 cfm(multi-tube design)and demonstrate uni
16、t at TAFB.Determine economic and scale-up factors for the plasma unit.Develop technology demonstration plan.,Phase II Current StatusComparing energy consumption parameters of different size reactors to determine scaling factors:Single-tube reactor with a 1 to 50 cm plasma zone.10-tube reactors with
17、1-cm or 5-cm plasma zones in each tube.Difficulties measuring the secondary current require customized circuitry.Economics will depend on energy requirements and final size.,10-Tube Reactor,AcknowledgmentsOklahoma City Air Logistics CenterCenter for Aircraft andSystems/Support Infrastructure,Acknowl
18、edgmentsVijay Kalpathi Ph.D.student,Chemical EngineeringVisalakshi Annamalai M.S.student,Electrical EngineeringRajbarath.P M.S.student,Environmental EngineeringElangovan Karuppasamy M.S.student,Environmental Engineering,Questions,Table 1.Summary of destruction data for residence time comparisons.,Table 2.Summary of destruction data for line operating frequency comparisons.,Table 3.Summary of destruction data for applied electric potential comparisons.,Table 4.Summary of destruction data for VOC concentration comparisons.,Table 5.Summary of destruction data for relative humidity comparisons.,
