Gas Bypass and Solids Circulation Rate of an i-cfb Reactor with Coarse Particles

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1 Engineering Conferences Interntionl ECI Digitl Archives The 14th Interntionl Conference on Fluiiztion From Funmentls to Proucts eferee Proceeings 213 Gs Bypss n Solis Circultion te of n i-cfb ector with Corse Prticles Xingxing Cheng The niversity of British Columbi, Cn Xioto T. Bi The niversity of British Columbi, Cn Follow this n itionl works t: Prt of the Chemicl Engineering Commons ecommene Cittion Xingxing Cheng n Xioto T. Bi, "Gs Bypss n Solis Circultion te of n i-cfb ector with Corse Prticles" in "The 14th Interntionl Conference on Fluiiztion From Funmentls to Proucts", J.A.M. Kuipers, Einhoven niversity of Technology.F. Mue, Delft niversity of Technology J.. vn Ommen, Delft niversity of Technology N.G. Deen, Einhoven niversity of Technology Es, ECI Symposium Series, (213). This Article is brought to you for free n open ccess by the eferee Proceeings t ECI Digitl Archives. It hs been ccepte for inclusion in The 14th Interntionl Conference on Fluiiztion From Funmentls to Proucts by n uthorize ministrtor of ECI Digitl Archives. For more informtion, plese contct frnco@bepress.com.

2 Gs Bypss n Solis Circultion te of n i-cfb ector with Corse Prticles Xingxing Cheng n Xioto T. Bi * Fluiiztion eserch Centre, Deprtment of Chemicl n Biologicl Engineering The niversity of British Columbi, Vncouver, Cn, V6T 2K9 T: (4) F: (4) E: xbi@chbe.ubc.c ABSTACT: An i-cfb rector ws recently propose for ecouple NOx sorption n reuction. In this pper, the hyroynmic of i-cfb, incluing gs bypssing n soli circultion rte, ws moele with the results compre with the experimentl t. The rector performnces with ifferent istributors, flt, cylinricl n conicl, were lso stuie. INTODCTION As promising e-nox technology, hyrocrbon selective ctlytic reuction (HC-SC) hs been wiely stuie since mi 198s. To llevite the negtive impct of oxygen on the enox performnce, ul sorption n reuction system hs been propose (1) in which the NOx sorption tkes plce in seprte column, ecouple from the ctlytic reuction which tkes plce in nother column. A novel HC-eNOx internl circulting fluiize be (i-cfb) rector ws recently propose by Yng n Bi (1) in which NOx is sorbe onto the ctlyst surfce in the sorption zone, n then sorbe NOx is reuce ctlyticlly in the reuction zone, with the ctlyst circulting between the sorption n reuction zones to fcilitte the continuous opertion. The performnce of the i-cfb rector is expecte to be impcte by the hyroynmics. Severl stuies hve reporte the hyroynmics of i-cfb rectors, minly focusing on the mesurement of solis circultion rtes (2) n the evelopment of correltions for preicting the soli circultion rte (3). These empiricl or semi-empiricl moels coul not be pplie irectly to i-cfbs with ifferent configurtions. In this stuy, gs bypssing n soli circultion rte in enox i-cfb rector of new configurtions were stuie in col moel unit with ifferent istributor configurtions, n hyroynmics moel ws evelope bse on mss n pressure blnce.

3 EXPEIMENTS A plexiglss i-cfb rector ws constructe with imeter of.116 m, rft tube imeter of.58 m n the column height of 1.16 m. The imensions of the unit were given in (4). Gs ws fe to both the rft tube n nnulus t ifferent velocities n the be mteril circultes between the rft tube n nnulus. Three types of istributors, flt, cylinricl n conicl pltes, s shown in Fig.1, were teste for the gs bypssing n soli circultion. The gp istnces for both the flt n cylinricl istributors, H G1, re set to be 1 mm. Two ifferent gp istnces, H G =1 mm n H G =15 mm, were teste for the conicl istributor. () (b) (c) Fig.1 Distributors for the nnulus gs flow. (): flt; (b): cylinricl; (c): conicl Builing ir ws use s the fluiizing gs. Millet ws use s be mteril in the test, with the properties shown in Tble 1. Two prmeters were mesure in the experiment, which re gs bypss n soli circultion rte. The gs bypss between the rft tube n the nnulus ws evlute by CO 2 trcer metho. The solis circultion rte of millet ws mesure using the visul observtion metho. The etils of the mesurement were given in (4). Be mteril Bulk ensity (kg/m 3 ) Tble 1 Prticle properties Averge prticle imeter (mm) (m/s) c (m/s) t * (m/s) Millet Note: *: clculte by correltion from (5) HYDODYNAMIC MODEL OF i-cfb Mss n pressure blnce equtions In n i-cfb, the internl circultion of solis is chieve by the pressure ifference between the rft tube n the nnulus operting t ifferent superficil gs velocities. Solis mss blnce n pressure blnce equtions re: M loing s 1 A H s A H M M 1 (1)

4 s 1 A A 1 s (2) P P P or In fluiize stte, the pressure rop coul be expresse by Eqs.4 n 5, which consist of the pressure rops ue to grvity, soli ccelertion, flui-wll friction n prticle-wll friction. (3) P H 2 1 pg.5 pup, HrfttubeF gw HrfttubeF pw effective, 1 (4) P H 2 1 pg.5 pup, HrfttubeFgw HrfttubeFpw effective, 1 where H effective, n H effective, re the effective be heights in the nnulus n rft tube, respectively. Konno n Sito s eqution (6) ws use to clculte the soli-wll friction n Grbvcic s correltion (7) ws use for the gs-wll friction. Ci s eqution (8), which shows goo greement with our experimentl be expnsion t, ws use to estimte the be expnsion in both the nnulus n the rft tube of the i-cfb rector, H H f p f.376 p (5) (6) where H f is the expne be height n H is the be height t minimum fluiiztion. Effective be height To obtin the effective be height for Eqs.4 n 5, the flow in the i-cfb ws ctegorize into four ifferent operting moes s shown in Fig.2. (): If there is no sufficient be soli loing or the ifference between the gs velocities of nnulus n rft tube is too smll, solis re not circulte n this flow pttern shoul be voie for the opertion of i-cfb. (b): When the solis be loing or the gs velocity ifference in the two zones is increse, the rft tube coul be fille up with ilute suspene solis n the solis coul strt to circulte to the nnulus region. In this moe, effective be height in the rft tube is the sme s the rft tube height, n the effective nnulus be height coul be clculte from totl mss blnce. (c): If the be loing or gs velocity is further increse, the nnulus be height clculte from mss blnce coul excee the height of the rft tube n flow pttern (c) is estblishe. In this cse, the effective nnulus be height cn still be clculte by mss blnce n the effective rft tube be height is equl to the effective nnulus be height.

5 (): When the be loing or gs velocity is further higher, the be of the nnulus ense be becomes too high n the ilute jet on top of the rft tube becomes unstble or cn no longer penetrte through. The effective rft tube be height, H effective,, is the sum of rft tube length n jet height, n the effective nnulus be height equls H effective,. () (b) (c) () Fig.2 Illustrtion of four i-cfb flow moes n the effective be height. ESLTS AND DISCSSION Gs bypss Due to the pressure ifference between the rft tube n nnulus n the flow of prticles from the nnulus into the rft tube t the bottom region, gs cn be crrie from one region to the other by prticles, cusing gs bypss n ltering the ctul gs flow in ech region. The mount of gs prtitioning into the nnulus n rft tube from their inlets coul ffect the flow rte of both zones n further ffect the soli circultion rte. Furthermore, in the i-cfb rector, the bypss of gs coul chnge the oxygen concentrtions in the ctlytic reuction zone, ffecting the rection performnce. Tble 2 Gs bypss correltions for ifferent istributors Distributor AD DA Flt H G = mm.88 AD 129 DA Cylinricl H G =1 mm.93 6 AD DA Conicl H G =1 mm Conicl H G =15 mm AD DA DA DA

6 Gs, kg/m 2.s Gs, kg/m 2.s Gs, kg/m 2.s Gs, kg/m 2.s The gs bypss rtio, both from the nnulr region to the rft tube ( AD ) n from rft tube to nnulr region ( DA ), ws mesure t ifferent gs velocities for the i-cfb with ifferent istributor configurtions (4). The t re then correlte s function of the rft tube gs velocity,, n nnulus gs velocity,, with the results shown in Tble 2. Those correltions will be couple into the hyroynmics moel to preict the soli circultion rte. Soli circultion rte The soli circultion rte ws mesure for ifferent rector configurtions with the t shown in Fig () =2.56 m/s =2.79 m/s =3.3 m/s =3.26 m/s =3.49 m/s Flt istributor.5.6.7, m/s (b) =.37 m/s =.45 m/s =.52 m/s Cylinricl istributor , m/s 3 25 =2.33 m/s =2.56 m/s =2.79 m/s 3 25 Conic istributor H G =15 mm (c) Conic istributor H G =1 mm.2.4.6, m/s () =1.63 m/s =1.86 m/s =2.1 m/s =2.33 m/s =2.56 m/s =2.79 m/s , m/s Fig.3 Soli circultion rtes t ifferent inlet velocities for ifferent configurtions: (): flt istributor; (b): cylinricl istributor; (c): conicl istributor, H G =1 mm; (): conicl istributor, H G =15 mm. (symbols: experimentl t (4); lines: moel fitte) Bse on the gs bypssing correltions, the rel gs velocities in the nnulus n rft tube coul be clculte. The voige in both zones coul then be obtine, followe by the clcultion of pressure rop over ech zone using Eqs.4 n 5, respectively. The pressure rop cross the orifice coul be obtine from the overll pressure blnce (Eq.3). It hs been reporte tht the pressure rop for gs-solis two-phse flow cross the orifice coul be generlly expresse s Eq.7, s erive from

7 (P or )^.5 (P or )^.5 (P or )^.5 (P or )^.5 Bernoulli s eqution for single phse flow (2, 9). This eqution showe goo greement with the experimentl vlues in Kim s group for i-cfbs (2, 3), with C D rnging from G S D A A 2 P. 5 C or / or (7) In this stuy, the nnulus of the i-cfb opertes s moving be t low vlues of. Thus voige in the nnulus is quite close to the voige t minimum fluiiztion. Accoring to Eq.7, G s is linerly proportionl to (ΔP or ).5, since ll the other prmeters re more or less remin s constnts. Vlues of G s n (ΔP or ).5 plotte in Fig.4show tht the performnces of ifferent istributors iffer significntly. The cylinricl istributor shows the best fitting with Eq.7. However, no liner reltionship with (ΔP or ).5 ws observe for G s vlues of i-cfb with flt istributor. Even for the sme type of conicl istributor, G s vlues from H G =15 mm shows better fitting with Eq.7 thn the vlues from H G =1 mm. Overll, it is unlikely tht single C D vlue coul be fitte to the experimentl t for ech istributor. 1 9 Flt istributor () G s, kg/m 2.s (b) 1 Cylinricl istributor G s, kg/m 2.s (c) Conicl istributor H G =1 mm G s, kg/m 2.s () Conicl istributor H G =15 mm G s, kg/m 2.s Fig.4 Plot of (ΔP or ).5 s function of G s for ifferent configurtions: (): flt istributor; (b): cylinricl istributor; (c): conicl istributor, H G =1 mm; (): conicl istributor, H G =15 mm; To further explore the chrcteristics of C D, C D vlues fitte from ech t point were plotte in Fig.5 s function of eynols numbers bse on prticle

8 velocity through the orifice, with the efinition given in Eq.8. It is observe tht ll the C D vlues increse lmost linerly with e p for ll the configurtions, with the obtine liner correltions given in Eqs.9 to 12. e p g p p, (8) Flt istributor: CD.245e p (9) Cylinricl istributor: CD.113e p (1) Conicl istributor, H G =1 mm: CD.45e p (11) Conicl istributor, H G =15 mm: CD.261e p (12) Flt Cylinricl Conicl HG=1 mm Conicl HG=15 mm C D e p Fig.5 C D s function of e p for ifferent configurtions. The simulte results using the fitte C D vlues in Eqs re lso plotte in Fig.3. This moel will be use for the moeling n simultion of the rector performnce of the i-cfb rectors for ctlytic reuction of NOx using hyrocrbon reuctnts. CONCLSIONS Hyroynmics in n i-cfb with ifferent istributor configurtions, flt, cylinricl n conicl, ws stuie. A hyroynmic moel ws evelope bse on the pressure/momentum blnce n mss blnce. Gs bypss ws lso consiere in the moel. Prticle ischrge coefficients of the orifice of ifferent istributors were obtine by fitting with the experimentl t. The moel showe goo greement with the mesure solis circultion t for ll the configurtions stuie.

9 NOMENCLATE A Cross sectionl re, m 2 ε Voige C D Drg force coefficient ρ Density, kg/m 3 Dimeter, m μ Viscosity, P.s F Frictionl force, P/m Subscript G s Soli circultion rte, Annulus kg/m 2.s H Be height, m Drft tube M Mss of solis, kg AD Annulus to rft tube ΔP Pressure rop, P DA Drft tube to nnulus Gs bypss rtio, % p Prticle e eynols number g Gs Velocity, m/s or Orifice EFEENCES (1). T. T. Yng n H. T. Bi, A novel fluiize be rector for integrte NOx sorption-reuction with hyrocrbons, Environ. Sci. Technol., (13): (2). J. H. Jeon, S. D. Kim, S. J. Kim, n Y. Kng, Soli circultion n gs bypssing chrcteristics in squre internlly circulting fluiize be with rft tube, Chem Eng Process, (12): (3). S. D. Kim, Y. H. Kim, S. A. oh, n D. H. Lee, Soli circultion chrcteristics in n internlly circulting fluiize be with orifice-type rft tube, Koren J. Chem. Eng., : (4). T. T. Yng, A novel fluiize be rector for integrte NOx sorption-reuction with hyrocbons, in Deprtment of chemicl n biologicl engineering. 28, niversity of British Columbi: Vncouver. (5). D. Kunii n O. Levenspiel, Fluiiztion Engineering. 1991, Msschusetts: Butterworth-Heinemnn. (6). H. Konno n S. Sito, Pneumtic conveying of solis through stright pipes, J. Chem. Eng. Jpn, : (7). Z. B. Grbvcic, D. V. Vukovic, S. D. Jovnovic,. V. Gric, D. E. Hzismjlovic, H. Littmn, n M. H. Morgn, Flui-Flow Pttern n Solis Circultion te in Liqui-Phse Spout Flui Be with Drft Tube, Cn J Chem Eng, (5): (8). P. Ci, G. D. Michele, n A. T. Grssl, A generlize metho for preicting gs flow istribution between the phses in FBC, Fluiize be combusiton, : (9). M. Kurmoto, D. Kunii, n T. Furusw, Flow of Dense Fluiize Prticles through n Opening in Circultion System, Power Technology, (2):