Advertorial structured-media misteliminator is less prone to plugging than con- ventional knitted-mesh mist eliminators, achieves higher removal efficiencies per unit of pres- sure drop, and has lower energy consumption and operating costs. Many pocss aiand gas stam pob- lms involvmist cayovand mist liminatoplugging. This oftn sults in ducd poduct yild, xcssivngyusag, coosion of plant quipmnt, shot- -than-xpctd quipmnt and catalyst lif, shotnd plant un tims, and/onot mting output capacity quimnts. Msmaoass Any tima liquid coms into intimatcontact with a flowing gas – as happns in many manufactuing pocsss – thntainmnt of liquid doplts into thgas stam gnats a mist. This mist can sult in pocss infficincis, poduct losss and quipmnt damag. Thbasic function of a mist liminatois to coll ct and movdoplts fom a gas stam. This is accomplishd whn thdoplts within thflowing gas stikthmist liminatomdia and acaptud. Thmatial coalscs on thmdia, and thlagdoplts that fom flow by gav- ity to a dainagaa and acovd. Thtypof mist liminatoappopiatfoa paticulaapplication is dtmind by thpaticl sizof thmist to bcol- lctd. In odto slct a mist liminatoand nsuthat it functions fficintly, it is ncssay to dfinthsizof thdoplts psnt in thsystm. Dopl ts aclassi- fid basd on thipaticldiamts: Spays: lagthan 10 micons •Mists: 10 micons to 1 micon •Aosols: smallthan 1 micon •Thfibs of thmist liminatomdia collct doplts by thdiffnt mch- anisms (Figu1) – intial impaction (≥ 10-20 micons), intcption (fodop- lts down to 1-3 micons in diamt) whdoplts tavl along thflow path but acaught (intcptd) as thy pass btwn thfibs. Bownian diffusion – dpnding on thdopl t siz. Duing intial impaction, lag(≥ 20-30 micons) doplts tavling in a staight lin, dvi- ating fom thflow of thgas, stikthsufacof thcylindical fib, and acollctd as thy impingon thfibs. Intcption, which applis to doplts down to about 1 to 3 micons in diamt, taks placwhn thdopl ts tavl along thflow path but acaught (intcpt- d) bcausthy cannot pass btwn thfibs. Bownian diffusion affcts paticls small than 1 micon in diamt. Whn gas mol culs collidwith small mist dop- lts, thdoplts gain kintic ngy in thfom of andom motion; thsmallthpaticl , thgatits andom motion, and thgatthliklihood that it will contact and bcoll ctd by thfibs. Mist liminatos aavailablin sval diffnt styls: Vanpacks, also known as chvon o•plat-typmist liminatos, consist ofclosly spacd cougatd plats that focmist-containing gas to follow totuous paths Candlfilts, ofibbds, mploy•finfibs, gnally of plastic oglass, packd into a mat and wound into a cylindWi-msh (oknittd-msh) mist •liminatos consist of multipllays of msh knittd fom mtal oplastic monofilamnts Stuctud-msh mist liminatos •acompisd of intlockd plastic monofilamnts smbling a laddohonycomb Vanmist liminatos agnallymoffctivfolagdopl ts (10 – 20 micons). Thy ausually moxpnsivthan a msh pad fothsamapplication. Candlfilts and convntional knit msh pads can plug adily; if thliq- uid bing captud is not pfctly clan, it will vntually clog thmdia, which must bcl and piodically and vntu- ally placd. KIMre Inc, Miami, Fla., has dvlopd a highly fficint stuctud-msh mist liminatoto ovcomthsand othdisadvantags of thmist liminatos cu- ntly on thmakt. OaoIn applications whsolids xist candls (fib-bds) should not busd. Manymist liminatoapplications adsignd foxcss capacity to compnsatfothsolids in thgas stam. Howvsuch mist liminatos anot dsignd to placthfunction of thgas clan- ing systm’s wt scubb. Plugging and thattndant high pssudop makfqunt maintnancand placmnt ncssay , causing a dop in ovall plant poduction and xcssivdowntim. Low-fficincy mist liminatos can lad APaticcoction mchanisms incintiaimpaction, intcp - tion, anBownian iffsion. HOwTo: Control Process Mist ELIMINATORS By Fred Mueller, Kimre Inc. Air pOllutiOn cOntrOl 62 Pollution EngineeringnOveMber2007 | HOwToGuide
