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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,7/5/2016,#,废水,处,处理,工,工艺,设,设计,及,及计,算,算,第,6,章,9-11,节,目录,CONTENT,6-9PHOTOLYSIS,光解,6-10,CHEMICALNEUTRALIZATION,SCALECONTROL,&STABILIZATION,化学,中,中和,水垢,控,控制,稳定,性,性,6-11,CHEMICALSTORAGE,FEEDING,PIPING,&CONTROLSYSTEMS,化学,贮,贮藏,、,、供,给,给、,管,管道,及控,制,制系,统,统,6-9,PHOTOLYSIS,6-9,1,Photolysisisaprocessbywhichconstituentsarebrokendownbyexposureandabsorptionofphotonsfromalightsource.AswithAOPs,theprimaryuseofphotolysisisfortheremovaloftraceorganiccompoundsinwaterreuseapplications.Innaturalsystems,sunlightisthelightsourceforphotolysisreactions,however,inengineeredsystems,ultraviolet(UV)lampsareusedtoproducethephotonicenergy.Theeffectivenessofthephotolysisprocessdepends,inpart,onthecharacteristicsofthereclaimedwater,structureofthecompounds,designofthephotolysisreactor,anddoseandwavelengthoftheappliedlight.Thephotolysisratecanbeestimatedfromtherateatwhichthecompoundabsorbslightandthe photonic efficiencyofthereaction(quantumyield).,定义,6-9,1,光解工,艺,艺,Photolysis Processes,Engineered photolysisreactions areconductedinspecially designed reactorsoptimizedwithrespect toUVdose.Photolysisreactorsare typicallycomprisedofastainlesssteelcolumnorpipe containing,UVlamps,arrangedparalleltotheflow,perpendiculartotheflow,or in acrisscrossingpattern perpendiculartothe directionofflow.,原理,The photons that areabsorbed causethe electrons in theouter orbitalof somecompoundsformsan unstable compoundthatsplits apart or becomesreactive.,UV,与,O,3,、,H,2,O,2,、,Fenton,联用。,UV,会促进,H,2,O,2,产生,OH,但加入,H,2,O,2,会抑制某些,有,有机物的分,解,解,6-9,1,Fouling that may occur ontheoutside oftheUV lamp protective quartzsleeve may bemanaged using an,automaticcleaning system,consistingof acollar that periodicallymoves along the lamp toremove precipitatesand interceptedmatter.,Whenusedin conjunctionwithreverse osmosispretreatment,the,chemicalsadded,to reducethe pH forscale controlin the membranes will also reduce the potential for precipitationon the UVlamps.,Photolysisreactionsare causedby lightemission in theultraviolet range(200to400nm).Therearethreetypes ofUV lamps usedfor photolysisprocesses:(1),low-pressure low-intensity,(2),low-pressure high-intensity,and(3),medium-pressurehigh-intensity,lamps.Low-pressurelampsemitmuchof theirenergy atawavelengthof 254 nmwhile medium pressure lamps emit energyatmultiple.The type of lamp used andreactor configurationwilldependon the constituent to beremoved aswellas the water matrixandsite-specific conditions.,6-9,1,光解所涉及,基,基本概念,:,(1),紫外光吸收,(2),入射能量,(3),光解速率,(4),电效率,The absorptionof light by a compound inwater orotheraqueous solutioncan be described using the,Beer-Lambert Law.,The absorbanceof asolution isa measureof the amount of light absorbed byconstituents inthe solution usinga spectrophotometerat aspecifiedwavelengthand overa fixed path length.,1,紫外光吸收,Absorptionof UV Light,A=absorbance,dimensionless,L=lightintensityafter passingthroughsolution,L=lightintensityafterpassing through a blanksolute,=extinctioncoefficient,C=concentration of light absorbingsolute,x=length oflightpath,K=absorptivity,The,extinctioncoefficient,is afunction of wavelength becauseasthe wavelengthdecreasesmoreenergeticphotons are absorbedandthe absorptivityof alightabsorbingcompound increases.,6-9,1,不同物质的,消,消光系数,6-9,1,溶液中存在,多,多种化合物,的,的情形：,使用多重波,长,长光源的情,形,形：,canbe determined usinga similarapproach,summing,adsorptionof each compound foreachwavelength.,2,入射能量,Energy Input for Photolysis,The lamp outputandreactor size can beusedto estimate theenergy input for the photolysis reaction.,存在问题,：,：,Theactualperformanceofa photoreactor is expected to belower thancomputeddueto lightbeing absorbed by the,reactorwalls,or blocked by the,precipitate,thatforms onthelampsleeve.,Whilea,safety factor,specifictoa particularsystemcould beappliedtocompensate for theseinefficiencies,pilot studies,areusedtoobtain morereliabledesigncriteria.,6-9,1,3,光解速率,RateofPhotolysis,Therateatwhich acompoundisphotolyzed depends on the rate and frequencyofphoton absorption.,Thequantumyield isa quantityusedtodescribethe,frequency,at whichphoton absorption resultsin aphotolysisreactionandis,specific,to the typeof compoundandthewavelength.,量子产率,quantumyield,As ageneralrule,the quantum yield,increases,aswavelength,decreases,(increasingphotonicenergy).,6-9,1,伪一级动,力,力学方程,Thepseudo firstorder ratelaw,Typically,the lightabsorptionby the componentthat istargeted for removal is,minor,ascomparedtothelight absorptionbythebackground watermatrix.,（全局平,均,均光解反,应,应速率）,4,电效率,ElectricalEfficiency,Theelectrical energy requirement for photolyticreactionsis significantdueto the process,inefficiencies,.Consequently,itisimportant tocompareprocessefficiencyonthebasisofelectricalusageperamountofcompounddestruction.Onesuchmeasureistheelectricalefficiencyperlogorder(EE/O)ofcompounddestruction.,6-9,1,electricalefficiencyperlogorder,（单,位,位,体,体,积,积,降,降,低,低,单,单,位,位,个,个,数,数,量,量,级,级,消,消,耗,耗,的,的,电,电,能,能）,通过测,量,量,EE/O,可以对,于,于特定,反,反应可,以,以计算,流,流率。,6-9,1,局限性,Photolysis ProcessLimitations,Theefficiencyofthepho
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