Thesis by Zaenab Abd Allahl

206 Pages·2012·3.85 MB·English

by  Zaenab Abd Allah

N -
ON THERMAL ATMOSPHERIC PRESSURE
PLASMA FOR REMEDIATION OF VOLATILE
ORGANIC COMPOUNDS
A thesis submitted to The University of Manchester for the degree of
Doctor of Philosophy
in the Faculty of Engineering and Physical Sciences
2012
ZAENAB ABD ALLAH
THE SCHOOL OF CHEMICAL ENGINEERING AND ANALYTICAL
SCIENCE
Contents
1 Introductiontotheenvironmentalproblemandtechnologicalplasmas 28
1.1 Theenvironmentalproblemofairpollution. . . . . . . . . . . . . . . . . 28
1.1.1 Globalwarmingandgreenhousegases. . . . . . . . . . . . . . . 29
1.1.2 Acidrain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
1.1.3 Groundlevelozone . . . . . . . . . . . . . . . . . . . . . . . . . 30
1.2 Volatileorganiccompounds(VOCs) . . . . . . . . . . . . . . . . . . . . 30
1.3 RemovalofVOCsfromgasstreams. . . . . . . . . . . . . . . . . . . . . 31
1.4 Principlesoftechnologicalplasmas . . . . . . . . . . . . . . . . . . . . . 33
1.5 Non-thermalplasmageneration,propertiesandapplication . . . . . . . . 34
1.6 Typesofplasmadischarges . . . . . . . . . . . . . . . . . . . . . . . . . 36
1.7 Directcurrent(DC)discharge . . . . . . . . . . . . . . . . . . . . . . . 36
1.7.1 Coronadischargeplasmareactors . . . . . . . . . . . . . . . . . 37
1.7.2 Radiofrequency(RF)andmicrowavedischarges . . . . . . . . . 38
1.7.3 Dielectricbarrierdischarge(DBD) . . . . . . . . . . . . . . . . . 38
1.7.4 Surfacedischargeplasmareactor(SD) . . . . . . . . . . . . . . . 40
1.8 Packed-bedplasmareactorcharacteristicsandadvantagesforairpollutant
remediation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
1.8.1 Pelletmaterialsanddielectricconstant . . . . . . . . . . . . . . . 42
1.8.2 Pelletsizeandshape . . . . . . . . . . . . . . . . . . . . . . . . 43
1.8.3 Advantagesandapplicationsofpacked-bedplasmareactors . . . 43
2
1.9 Literaturereviewfordichloromethaneandmethylchloridedecomposition
usingplasma. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
1.10 Aimsandobjectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
1.11 Structureofthethesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
2 Methodology 47
2.1 Experimentalarrangements . . . . . . . . . . . . . . . . . . . . . . . . . 47
2.2 Packed-bedplasmareactors . . . . . . . . . . . . . . . . . . . . . . . . . 48
2.2.1 Singlestagepacked-bedplasmareactor . . . . . . . . . . . . . . 48
2.2.2 Multiplepacked-bedplasmareactor . . . . . . . . . . . . . . . . 50
2.3 SpectroscopicdiagnostictechniquesusinganFTIRspectrometer . . . . . 51
2.3.1 PrinciplesofIRspectroscopy . . . . . . . . . . . . . . . . . . . 52
2.3.2 FTIRspectrometercomponents . . . . . . . . . . . . . . . . . . 53
2.3.3 TheadvantagesofFTIRspectroscopy . . . . . . . . . . . . . . . 58
2.4 Sampling,spectralanalysesandconcentrationcalculations . . . . . . . . 58
2.4.0.1 Signal to noise ratio, spectral resolution and limit of
detectionfortheFTIRspectrometer . . . . . . . . . . . 62
2.4.1 Opticalemissionspectroscopy . . . . . . . . . . . . . . . . . . . 65
2.5 Gasdeliverysystemandthecalculationsofthegasflowrates . . . . . . . 66
2.6 Errorcalculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
2.6.1 Theerrorinconcentrationscalculation. . . . . . . . . . . . . . . 68
2.6.2 ErrorcausedbyDCMtemperaturechange . . . . . . . . . . . . . 69
2.7 Electricalmeasurementsandcalculations . . . . . . . . . . . . . . . . . 70
2.8 Time required to reach a steady state plasma in nitrogen and argon gas
streamsgeneratedinapacked-bedplasmareactor . . . . . . . . . . . . . 72
3
2.8.1 Dichloromethane decomposition in nitrogen and argon plasma
overtime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
2.8.2 Nitrogen and argon plasma emissions over time in a packed-bed
plasmareactor. . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
2.8.3 Consumedpowerandplasmatemperatureovertime . . . . . . . 74
2.8.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
3 Remediation of dichloromethane, CH Cl using non-thermal plasma gener-
2 2
atedinapacked-bedplasmareactor 77
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.1.1 Experimentalsetup . . . . . . . . . . . . . . . . . . . . . . . . . 78
3.2 InfluenceofoxygenconcentrationontheremovalefficiencyofDCM. . . 79
3.2.1 The effect of oxygen concentration on the formation of plasma
endproducts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
3.3 Influenceofinitialdichloromethaneconcentrationsontheremovalefficiency. 85
3.3.1 The effectof initial dichloromethaneconcentration on the forma-
tionofplasmaendproducts. . . . . . . . . . . . . . . . . . . . . 85
3.4 InfluenceofenergydensityontheremovalefficiencyofDCM. . . . . . . 87
3.4.1 Influenceofenergydensityontheformationofplasmaendproduct
fromdichloroethanedecomposition. . . . . . . . . . . . . . . . . 89
3.5 InfluenceoftheplasmaresidencetimeontheremovalefficiencyofDCM. 90
3.6 InfluenceofbackgroundgasontheremovalefficiencyofDCM . . . . . . 91
3.6.1 Argonplasmainfluenceontheremovalefficiencyofdichloromethane 92
3.7 Reaction pathway for the decomposition of dichloromethane in non-
thermalplasmareactor. . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
3.8 Initialkineticsimulationwork . . . . . . . . . . . . . . . . . . . . . . . 97
3.9 Comparisonbetweentheresultsobtainedinthisinvestigationforoxygen
concentrationinfluenceandotherwork. . . . . . . . . . . . . . . . . . . 100
3.10 Summaryandconclusions . . . . . . . . . . . . . . . . . . . . . . . . . 102
4
4 Remediation of Methyl Chloride, CH Cl using non-thermal plasma gener-
3
atedinapacked-bedplasmareactor 104
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
4.2 Influenceofoxygenconcentrationandinitialmethylchlorideconcentration
ontheremovalefficiencyofmethylchloride . . . . . . . . . . . . . . . . 105
4.2.1 Influence ofoxygen and initialmethyl chloride concentrationon
plasmaby-productformation. . . . . . . . . . . . . . . . . . . . 108
4.3 Influenceofenergydensityontheremovalefficiency . . . . . . . . . . . 111
4.3.1 Energydensityeffectonplasmaby-productformation . . . . . . 112
4.4 Influenceofplasmaresidencetimeontheremovalefficiency . . . . . . . 117
4.5 Reactionpathwayforthedecompositionofmethylchlorideinnon-thermal
plasmareactor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
4.6 SummaryandConclusions . . . . . . . . . . . . . . . . . . . . . . . . . 120
5 TheeffectofaddingalkeneonthedestructionofDCMinnon-thermalplasma
generatedinapackedbedreactor 122
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.2 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
5.3 The influence of adding varying amounts of propylene to a gas stream
containing 500 ppm of dichloromethane on the removal efficiency of
dichloromethaneinnon-thermalplasma. . . . . . . . . . . . . . . . . . . 124
5.3.1 Theeffectofaddedpropylene concentrationontheformationof
plasmaendproducts. . . . . . . . . . . . . . . . . . . . . . . . . 127
5.3.2 Reaction pathway for the decomposition of propylene in non-
thermalplasmareactor. . . . . . . . . . . . . . . . . . . . . . . . 129
5.4 SummaryandConclusions . . . . . . . . . . . . . . . . . . . . . . . . . 131
5
6 Multiplepacked-bedplasmareactor 133
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
6.1.1 Experimentalsetup . . . . . . . . . . . . . . . . . . . . . . . . . 134
6.2 Multiplepacked-bedplasmareactorfordichloromethaneremediation . . 136
6.2.1 The energy efficiency parameter β for the multiple packed-bed
plasmareactor . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
6.2.2 Theformationofplasmaendproductsasaresultofdichlorometh-
anedecompositioninamultiplepacked-bedplasmareactor . . . 141
6.3 Theeffectofaddingpropyleneontheremovalefficiencyofdichlorometh-
aneinamultiplepacked-bedplasmareactor. . . . . . . . . . . . . . . . . 144
6.3.1 Thedecomposition ofdichloromethane withthe additionof 500
ppmpropyleneusingamultiplepacked-bedplasmareactor. . . . 144
6.3.2 Thedecomposition ofdichloromethane withtheaddition of1000
ppmpropyleneusingamultiplepacked-bedplasmareactor. . . . 148
6.3.3 The energy efficiency parameter β for dichloromethane decom-
positioninamultiplepacked-bedplasmareactorwiththeaddition
of1000ppmpropylenetothegasstream. . . . . . . . . . . . . . 151
6.4 In situ IR absorption measurements for the decomposition of dichloro-
methaneusingamultiplepacked-bedplasmareactor. . . . . . . . . . . . 152
6.4.1 Comparisonofdichloromethanemeasuredinsituandin-lineusing
amultiplepacked-bedplasmareactor. . . . . . . . . . . . . . . . 156
6.4.2 The detection of new species with in situ measurements using a
multiplepacked-bedplasmareactor. . . . . . . . . . . . . . . . . 157
6.5 Summaryandconclusions . . . . . . . . . . . . . . . . . . . . . . . . . 158
6
7 Behaviourofnitrogenoxidesinnon-thermalplasmapacked-bedreactor 160
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
7.2 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
7.3 Formation of nitrogen oxides in non-thermal plasma with nitrogen and
oxygengasmixture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
7.4 Theeffectofaddingchlorinatedhydrocarbonsontheformationofnitrogen
oxides in non-thermal plasma generated in a single stage packed-bed
plasmareactor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
7.5 Theeffectofaddingpropylenealonecomparedwithamixtureofdichloro-
methaneandpropyleneontheformationofnitrogenoxidesinnon-thermal
plasma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
7.6 Theinfluenceofthenumberofplasmacellsontheformationofnitrogen
oxidesasplasmabyproductduringthedecompositionofdichloromethane
inanitrogen-oxygenplasma. . . . . . . . . . . . . . . . . . . . . . . . . 171
7.7 AcomparisonofNO behaviourinallthestudiedconditionsinairplasma. 173
x
7.8 Reaction pathway for the formation of nitrogen oxides in non-thermal
plasmareactor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
7.9 Summaryandconclusions . . . . . . . . . . . . . . . . . . . . . . . . . 176
8 Summary,conclusionsandfurtherwork 177
8.1 Furtherwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
9 Appendix 202
Thetotalwordcountofthisthesisis58460words.
7
List of Figures
1.1 A sketch of the Earths annual energy balance illustrating the incoming
radiation from the sun and the radiated energy from earth surface. All
the numbers are in W m−2, the width of arrows is proportional to their
importance. ThissketchistakenfromKiehletal. (1). . . . . . . . . . . . 29
1.2 Examplesofnaturallygeneratedplasma,sun,auroraandlightning. Pic-
turesaretakenfrom(en.wikipedia.org)on26-11-2011 . . . . . . . . . . 34
1.3 SeveralDCdischargesasafunctionofthepropertiesoftheappliedvoltage
anddischargecurrent. Takenfrom(2)and(3) . . . . . . . . . . . . . . . 37
1.4 Two examples of pulsed corona plasma reactors. (a) is a wire and pipe
reactorand(b)isawireandplatereactor . . . . . . . . . . . . . . . . . 38
1.5 DischargedevelopmentinaDBDreactor. (a,bandc)showsthedischarge
development,while(dande)showtheeffectofincreasingthedielectric
conductivityanddecreasingthegap. Takenfrom(4) . . . . . . . . . . . 39
1.6 SomeexamplesforDBDplasmareactors . . . . . . . . . . . . . . . . . 40
1.7 Anexampleofsurfacedischargeplasmareactor . . . . . . . . . . . . . . 41
1.8 Examplesofpacked-bedplasmareactors . . . . . . . . . . . . . . . . . . 41
2.1 Aschematicdiagramoftheexperimentalinletsystemwhichhasbeenused
foralltheinvestigationscarriedoutinthisstudy. . . . . . . . . . . . . . 48
2.2 Avelocityprofiledistributioninafunnel . . . . . . . . . . . . . . . . . . 49
2.3 Aphotoandasketchforthesinglestageplasmareactor . . . . . . . . . 50
2.4 Photograph and sketch of the modified single stage packed-bed plasma
reactor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
2.5 Photographandsketch ofthemultiplepacked-bedplasmareactor. Three
similarneonsignpowersupplieswithafrequencyof20kHzwereused. . 52
8
2.6 Dichloromethanefundamentalmodesofvibration. AdaptedfromShiman-
ouchi,1972(5). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
2.7 An example FTIR spectrum for about 500 ppm of dichloromethane in
nitrogenshowingthevibrationalmodes. Amultiplepassopticalgascell
witha5.3mpathlengthwasused. . . . . . . . . . . . . . . . . . . . . . 55
2.8 AschematicdiagramforthelayoutofaFTIRspectrometer . . . . . . . . 55
2.9 AnexampleofFTIRinterferogram . . . . . . . . . . . . . . . . . . . . . 56
2.10 An example of the steps taken via the FTIR spectrometer to obtain an
absorbance spectrum for a gas stream of 500 ppm DCM, 3 % oxygen
andnitrogen. Amultiplepassopticalgascellwith5.3mpathlengthand
spectralresolutionof1cm−1 wereused. . . . . . . . . . . . . . . . . . . 57
2.11 Specac multiple pass gas cell and a sketch demonstrating the multiple
reflectionstoobtaina5.3mpathlength . . . . . . . . . . . . . . . . . . 59
2.12 Anexampleofareasselectionwhencalculatingtheconcentrationof(A)
DCMand(B)CO. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
2.13 The integrated area between 787 and 647 cm−1 for (a) an experimental
spectrum of DCM at unknown concentration measured with 5.3 meter
opticalpathlengthandaresolutionof2cm−1. (b)standardspectrumfor
1ppmdichloromethanemeasuredwith1meteropticalpathlengthanda
resolutionof0.1cm−1. . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
2.14 Examples of the different options for setting the spectral baseline for
integratingtheareabeneatheachpeak. . . . . . . . . . . . . . . . . . . 61
2.15 AnexampleFTIRspectrumforabout1000ppmCOwitharesolutionof1
cm−1. Amultiplepassopticalgascellwitha5.3mpathlengthwasused. . 62
2.16 An example of the spectrum used to calculate the limit of detection. (a)
showsthebackgroundnoisewitharesolutionof1cm−1,while(b)shows
theHCNspectrumfor1ppmwitharesolutionof0.1cm−1. Bothspectra
arefor5.3mopticalpathlength. . . . . . . . . . . . . . . . . . . . . . . 64
2.17 An example HCN limit of detection calculation. The intercept point
between HCN peaks heights and the minimum accepted signal to noise
ratio. HCNlimitofdetectionisabout15ppm. . . . . . . . . . . . . . . . 64
9
2.18 Nitrogenplasmaemission . . . . . . . . . . . . . . . . . . . . . . . . . . 66
2.19 Simplifiedsketchofthegasdeliverysystem . . . . . . . . . . . . . . . . 66
2.20 Standardandexperimentalspectrafor500ppmCO.Thestandardspec-
trumwitharesolutionof0.1cm−1isinblueandtheexperimentalspectrum
with a resolution of 2 cm−1 is in red. The black spectrum presents the
subtractionofthetwospectra. . . . . . . . . . . . . . . . . . . . . . . . 69
2.21 Voltageandcurrentwaveformsmeasuredusingapicoscope. . . . . . . . 70
2.22 Powerwaveformoveronepulse. . . . . . . . . . . . . . . . . . . . . . . 71
2.23 The removal efficiency of 500 ppm of dichloromethane in nitrogen and
argon plasma over thirty minutes starting from the moment of initiating
plasma. Gas streams with 0 and 1 % oxygen in a total flow rate of 1 L
min−1 wereused. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
2.24 UVvisibleemissionfromargonplasmaafteraboutfifteenminuteofiniti-
atingplasmainapacked-bedplasmareactor . . . . . . . . . . . . . . . 74
2.25 Theintensityofexcitednitrogenmoleculesandargonatomsinpacked-bed
plasmaismeasuredoverthirtyminutes. Totalflowrateof1Lmin−1 and
anenergydensityofabout1000JL−1 wereused. . . . . . . . . . . . . . 75
2.26 Deposited energy consumption and the temperature of the reactor body
fornitrogenplasmaasafunctionoftime. Measurementsweretakenevery
minutefromthemomentofinitiatingplasmaandupto30minutes . . . . 75
3.1 Plasmainletsystemwhichhadbeenusedtoinvestigatetheinfluenceofa
varietyofparametersontheremediationofdichloromethane. . . . . . . . 79
3.2 FTIR spectra for 500 ppm dichloromethane after plasma reactor (a) ni-
trogen plasma without adding oxygen (b) nitrogen plasma with adding
3 % oxygen to the gas stream. A multiple pass optical gas cell with a
5.3 m pathlength, a total flow rate of 1 L min−1 and an energy density
of about 1000 J L−1 were used. Measurements were taken about 0.75
secondsdownstreamoftheplasmareactor. . . . . . . . . . . . . . . . . 80
10