Environmental Science

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1 ISSN : Volume 8 Issue Environmentl Siene An Indin Journl Current Reserh Pper ESAIJ, 8(), 03 [436-44] Theoretil nd experimentl study of rdon seprtion from ter by bubbling system Hossein Noorinezhd, Hssn Hshemipour Rfsnjni *, Mrym Mirzie, Ali Negrestni Deprtment of Chemil engineering, College of Engineering, ShhidBhonrUniversity of Kermn, Kermn, (IRAN) Rdon reserh lbortory, Interntionl Center of Siene, High Tehnology & Environmentl Sienes (ICST), Kermn, (IRAN) E-mil : H-hshemipour@mil.uk..ir ABSTRACT To py ttention to importne of erthquke predition, mny of reserhers try to predit this nturl disster by mens of events nd preursors tht tke ple before erthquke. Chnge of rdon onentrtion in therml ters bout tive fults is one of these preursors. Rdon in ter (espeilly in ontinues monitoring) n be determined by mesuring rdon in n ir iruit oupled to the ter. In this reserh used bubbling System for oupling of ir nd ter, theoretil nd empiril study re done on this system. Time onstnt prmeter s n inditor of seprtion rte s lesser thn 0 minutes in most of experimentl onditions. In other to determine of bubbling system s optimum orking point, mthemtil modeling of this system s presented, too. 03 Trde Siene In. - INDIA KEYWORDS Seprtion; Bubble olumn; Rdon; Mthemtil modeling. INTRODUCTION Annully, in ll over the orld nturl dissters suh s floods, hurrines, erthqukes, et. use irreprble losses of life nd property. Most of these events re preditble nd humn tkes neessry tions before tht they tke ple. Unfortuntely, ginst the improvement of siene nd tehnology, one of these nturl dissters tht humn nnot predit tht, is erthquke. Erthquke from the viepoint of losses of life hs first ple mong the nturl dissters nd it is on seond ple from the viepoint of losses property. Therefore, more studying nd reserhing on this field is vitl. Reserhers indited tht there re mny erthquke preursors. One of these preursors is hnging of rdon onentrtion in therml ters bout of tive fults. In 007, Erees et l. studied rdon onentrtion in therml ters nd indited tht rdon onentrtion in therml ters hnges before or fter of erthquke []. Therefore, rdon onentrtion in therml ters bout tive fults should be mesure ontinully. Most of rdon monitors nnot detet rdon onentrtion in ter diretly, nd they n detet rdon onentrtion in ir bond it. Therefore rdon moleules should be seprted from ter nd trnsferred to ir. Aertion nd membrne seprtion methods re usul methods. Aertion method is fster thn membrne seprtion but ir humidity in this method is too

2 ESAIJ, 8() 03 high. When rdon onentrtion in ter hnges, its onentrtion should hnge in ir. Most importnt ftor for selet seprtion method is quikness of this proess. Here, time onstnt prmeter is defined s required time tht onentrtion of rdon reeives to 63% of its finl onentrtion. In 996, Surbek used membrne ontt method to trnsfer rdon from ter into ir. He provided pipe membrne from polypropylene nd put it in ontinous flo of ter. Air inter side of pipe membrne nd out from nother side, then inter to detetor of rdon onentrtion. Exhusting ir from detetor return to membrne so tht ir hs losed ouple yle. Time onstnt tht he hieved from his system, s bout 7 minutes []. In this reserh, ith ontt of ter nd ir in bubbling system, ho hnging of rdon onentrtion is studied nd time onstnt of this system is mesured. The used ir system in this study is bubble olumn. This system is seleted sine the rte of mss trnsfer beteen to phses ter nd ir is pproprite nd diffusion of ter into ir phse inrese so onsumption of desint inrese. Also, in this study in order to determine optimum performne point, pproprite mthemtil model is given. In the must experimentl onditions, time onstnt is less thn 0 minutes. At optimum performne point this onstnt is bout minute. TIME CONSTANT DETERMINATION METHOD Hssn Hshemipour Rfsnjni et l. 437 Current Reserh Pper nd trnsport it to ir, bubbling system s used. Bubbling system omposed of ylindril bubble olumn by 0 m dimeter nd 3 m height. Mteril of olumn s glss nd perforted tube s used for mking bubble in bottom of olumn. There re to holes on top of olumn. One of these holes for entering ter nd other for exhusting ir. Also there re to holes in bottom for ter dishrging nd ir entering to olumn. Wter rte s ontrolled by vlve nd (figure ). In order to onsidertion of ter temperture on time onstnt, heter s used on ter pth before inter in olumn. Wter temperture s deteted by thermometer nd (figure ). A pump s used for irultion of ir in ouple yle. Also ir flo rte s mesured by rotmeter. Wter flo rte s mesured by sled glss nd hronometer. In this reserh, RAD7 ontinues monitor s used for detetion of rdon onentrtion in ir. This detetor mde by DURRIDGE Compny. Some desint s used on ir yle pth beuse of RAD7 is sensitive bout humidity. At hole of experiments in this reserh, holdup to hold on 30 m. there is shemti of this system in figure. Surbek shoed in figure, if rdon onentrtion in ter hs step hnge then rdon onentrtion in ir ill hnge exponentilly ith time (eqution ()). t C( t) C( ) ( exp( )) () In this eqution ô is time onstnt. By fitting experimentl dt nd mthemtil modeling results on this reltion, e n determine experimentl nd modeling time onstnt respetively. It is ler tht if seprtion is fst then ô is smll. MATERIALS AND METHODS In this reserh, for rdon seprtion from ter Figure : Rdon onentrtion hnging in ter detetor MATHEMATICAL MODELING Experimentl dt shoed stisftory of this setup (TABLE ). Mthemtil modeling of this setup s presented. By this modeling optimum performne point of system s determined. Bubble olumn is most importnt to modeling this set-up. In this reserh, xil ersion model tht is usul model for bubble ol- Environmentl Siene An Indin Journl

3 438 Theoretil nd experimentl study of rdon seprtion. from ter by bubbling system Current Reserh Pper umns [3], s used for both phse (ter nd ir). An element ith dx idth s supposed in xil diretion of bubble olumn (figure ). Mss blnes in to phses ere ritten on rdon. ESAIJ, 8() 03 Figure : Element of bubble olumn In figure, N nd N re rdon mss trnsfer rtes in ter nd ir due to ersion, respetively. N nd N lso re rdon mss trnsfer rtes in ter nd ir due to etion, respetively [4]. These prmeters re defined s follos: C N EA () x N u AC (3) N Environmentl Siene An Indin Journl C E A x N u AC () In figure, N is mss trnsfer rteof rdon per unit R volumeof bubble olumn from ter to ir. Usullythe overll mss trnsfer rte per unit volume of bubble olumn is governed by the liquid-sidemss trnsfer oeffiient. Therefore: * N K ( C C ) (6) R L In this reltion * C is rdon onentrtion in interfe of to phses. It s supposed t equilibrium ith rdon onentrtion in ir bulk: * C k C (7) In eqution (7), k is rdon ter solubility (Ostld oeffiient), defined sthe stedy stte rtio C /C.k is the temperture dependent (see figure 3). (4) Figure 3 : Rdon ter solubility vs. temperture (Ostld oeffiient k) With substtion (7) into (6): N R K L( C kc ) (8) After riting blnes on rdon in ter nd ir, then substtion reltions, 3, 4,, 8 in these blnes, governing equtions on rdon onentrtion in ter nd ir ill be obtining. These governing equtions re ouple nd depend on time (t) nd lotion (x). It is neessry to remind tht time of experiment is negligible ginst rdon hlf time (T / = 3.8 Dys), then rdon onsumption in ir nd ter by dey retion s negleted []. For ter phse: C C C E u KL( C kc ) (9) x x t Boundry nd initil onditions of this eqution re: C (0) ( x,0) C0 C (0, t) 0 () x C () ( L, t) C0 In these reltions, C 0 is rdon onentrtion in inlet ter to olumn. This onentrtion is mesured by bth method. It is stndrd y of RAD7 detetor for mesuring of rdon onentrtion in ter. For ir phse: C C C E u KL( C kc ) x x t Boundry nd initil onditions of this eqution re: ( x,0) 0 (3) C (4)

4 ESAIJ, 8() 03 C ( L, t) 0 () x In other to obtin seond boundry ondition of eqution 4, it is neessry to model ir out of olumn. In other ords, this modeling result reltion beteen rdon onentrtion in ir t inlet nd outlet of olumn. Constituents out of olumn ere supposed mix tnk. Therefore: dc (0,t ) Q( C( L,t ) C (0,t )) Vm (6) dt Vmis volume of mix tnk equivlent ith volume of prts in ir yle (exeption bubble olumn). For this setup, V m is bout 6 liters. Experimentl orreltions for estimting of prmeters Correltions ere used for estimting of prmeters listed in TABLE : TABLE : Correltions ere used for estimting prmeters in the model Prmeter Symbol orreltion ref Wter.4 ersion E E.7d u [3] oeffiient Air ersion oeffiient Air hold-up volumetri mss trnsfer oeffiient Ostld oeffiient E å K L k E u 4. 0 d Hssn Hshemipour Rfsnjni et l u g K L d D R, d u k 0.4 D 3 4 R, g d u d g [3] [6] [6] 0.00 T e [6] SOLUTION OF MODEL S EQUATIONS In other to determintion of rdon onentrtion in ir, equtions (9) nd (4) ith their onditions must solved simultneously. 00 volume elements ere supposed in xil diretion of olumn. Then finite volume Current Reserh Pper method s used nd disrete form of equtions (9) nd (4) for ll of element s obtined [7]. Ultimtely, system of liner equtions s solved. RESULTS AND DISCUSSIONS Experimentl results After prepring setup, 0 tests ere rried. There re onditions of eh experiment nd their time onstnts in TABLE. In order to verifying of model, time onstnts by models ere obtined, too (TABLE ). Aording to this tble, model n predit this lb setup, stisftory. Therefore, this model s used for determintion of optimize orking point of this setup. In other ords, t optimum orking point: Time onstnt s muh s possible must be minimum. Sensitivity of time onstnt versus test onditions must be lo. Chnge onentrtion of rdon in ir must be influened by hnge onentrtion in ter to pplied it for predit erthquke. As shon in figure 3, finl onentrtion of rdon in ir lso influened by temperture. Error of model (%) TABLE : Results of experiments Mô (min) Eô (min) C 0 (Bq/m 3 ) T ()ú Mthemtil modeling results Wter flo rte effet Q (lit/min) Q (lit/min) 0.3 Environmentl Siene An Indin Journl.8 Effet of ter flo rte on time onstnt s shon in figure 4. Inresing ter flo rte uses little deresing of time onstnt. This effet is sme in other tempertures. Experimentl dt in TABLE onfirm this result. When ter flo rte s inresed, mss trns-....

5 440 Theoretil nd experimentl study of rdon seprtion. from ter by bubbling system Current Reserh Pper Figure 4 : Effet of ter flo rte on time onstnt (C 0 = 3000Bq/m 3, Q = lit/min) fer of rdon beteen ter nd ir lso inrese little. Therefore, Time onstnt s deresed little. As result, if ter flo rte be more then time onstnt is little smller. Therefore, ith ttention to restrition of rte of spring, ter flo rte - 4 liter per minute is suitble for this setup. Air flo rte effet Effet of ir flo rte on time onstnt s shon in figure. Inresing of ir flo rte from 0.lit/min to lit/min derese time onstnt ppreibly. More inresing of ter flo rte doesn t ppreible effet on time onstnt. Then, ith ttention to figure nd restrition of ir pump poer (eletriity optimiztion), 6 lit/min is suitble rte for ir yle. Time onstnt t this flo rte is stisftory. In ddition, it hs lo sensitivity regrd to hnging of -lit/min of ir flo rte. Wter temperture effet ESAIJ, 8() 03 Effet of ter temperture on time onstnt s shon in figure 6. It is observed tht hnges of time onstnt ith temperture hs to reigns, inresing nd deresing. Therefore it hs mximum t temperture bout 3 C. Experimentl dt in TABLE onfirm this result. As mentioned lredy, solubility of rdon in ter is exponentil funtion of temperture (figure 3). Inresing of temperture use derese solubility of rdon in ter, then mount of finl onentrtion of rdon in ir,tht ontt ith ter, rises. Therefore time onstnt of system inreses. Rise of temperture lso, trnsends oeffiient of mss trnsfer nd slkes time onstnt. With ttention to this disussion, t initil time solubility ftor domintes nd use initil time onstnt inrese. With higher temperture, oeffiient mss trnsfer ftor in proportion to solubility is dominte, then time onstnt derese. With hnge in ter temperture, solubility in ter nd finl onentrtion of rdon in ir revolve. Therefore for optimum performne of system, temperture must be hosen tht: sensitivity of equilibrium rdon onentrtion on hnge of temperture be negligible, time onstnt be enough smll t this temperture nd energy onsumption for het of system be lo. With respet to given disussions nd figures. 3 nd 6, temperture bout 0 C is n pproprite temperture for optimum performne of this system. Figure : Effet of ter flo rte on time onstnt (C 0 = 3000Bq/m 3, Q =. lit/min) Figure 6 : Effet of ter temperture on time onstnt (Q =. lit/min, C 0 = 3000Bq/m3) Environmentl Siene An Indin Journl

6 ESAIJ, 8() 03 NOMENCLATURE A : bubble olumn ross re (m ) C : rdon onentrtion in ir (Bq/m 3 ) C : rdon onentrtion in ter (Bq/m 3 ) : Rdon onentrtion t interfe (Bq/m3) : diffusivity of rdon in ter (m /s) d : olumn dimeter (m ) E : ersion oeffiient of ir (m /s) E : ersion oeffiient of ter (m /s) k: rdon ter solubility ( -) K L : volumetri mss trnsfer oeffiient bsed on liquid phse (s - ) L : bubble olumn height (m) N : rdon mss trnsfer rte in ir due to etion N : rdon mss trnsfer rte in ir due to ersion N : rdon mss trnsfer rte in ter due to etion N : rdon mss trnsfer rte in ter due to ersion N : rdon mss trnsfer rte from ter to ir (Bq/ R s) Q : ir volume flo rte (m 3 /s) Q : ter volume florte (m 3 /s) T : ter temperture (ë) t : time (s) : superfiil veloity of ir (m/s) u u Vm : super fil veloity of ter (m/s) : volume of ir store inluding pump nd RAD7 system (m 3 ) ñ : ter density (kg/m 3 ) µ : kinemti visosity of ter (kg/(m.s)) v : dynmi visosity of ter (m /s) ó : surfe tension of ter (s) å : ir hold-up ( -) å : ter hold-up ( -) CONCLUSIONS. Inresing ter flo rte doesn t hve ny ppreible effet on time onstnt. Hssn Hshemipour Rfsnjni et l. 44 Current Reserh Pper. Inrese ir flo rte to 4 lit/min use time onstnt onsiderbly derese, nd ith higher flo rte, this deresing trend is negligible. 3. t initil time, hen temperture of ter inrese, time onstnt lso inrese but ith higher temperture, trend of time onstnt is not inresing nd from bout 3 C, it derese. 4. With spet to time onstnt of system, it is resulted tht this system is pproprite for mesure of rdon onentrtion. Only defet of this system is high onsumption of desint.. With ttention to good greement beteen mthemtil model nd experimentl dt, n sy tht xil ersion model is n pproprite model for nlysis of bubble olumn. REFERENCES [] F.S.Erees et l; Rdon onentrtions in thermlters relted to seismi events long fults in the DenizliBsin,Western Turkey, J. Rdition Mesurements, 4, (007). [] H. Surbek, A rdon- in- ter monitor bsed on fst gs trnsfer membrnes, Int. Conf. On TENR, Otober 6-9, (996). [3] W.D.Deker; Modeling for bubble olumn retors, st edition, John Wiley & sons, (99). [4] J.Behin, G.Soltnin, M.Jfri Nsr, M.FlhiYekt; Modeling nd simultion of multi stges bubble olumn in produe of hydrogen peroxide prosess, pper presented t the 0th onferene of hemil engineering, Zhedn,Irn, (004). [] D.NikeziL, V.Urosevi; A theoretil study of rdon mesurement ith tivted hrol, J. Nul. Instr.And Meth.In Phys.Res.A, 406, (998). [6] K.Shimizu, S.Tkd, K.Minek, Y.Kse; Phenomenologil model for bubble olumn retors: predition of gs hold-ups nd volumetri mss trnsfer oeffiients, Chem.Eng.J, 78, (000). [7] S.V.Ptnkr; Numeril Het Trnsfer nd Fluid Flo, Hemisphere Publishing Corportion, Ne York, (980). Environmentl Siene An Indin Journl