Gas Tracer Study in a Non Mechanical L-Valve

Transcription

1 Engineering onference International EI Digital Archive 10th International onference on irculating Fluidized Bed and Fluidization Technology - FB-10 Refereed Proceeding 2011 Ga Tracer Study in a Non Mechanical L-Valve Mohammad-Mahdi Yazdanpanah IFP, France Ali Hoteit IFP, France Ann Forret IFP, France Thierry Gauthier IFP, France Arnaud Delebarre ESSTIN, niverite Henri Poincare, France Follow thi and additional work at: Part of the hemical Engineering ommon Recommended itation Mohammad-Mahdi Yazdanpanah, Ali Hoteit, Ann Forret, Thierry Gauthier, and Arnaud Delebarre, "Ga Tracer Study in a Non Mechanical L-Valve" in "10th International onference on irculating Fluidized Bed and Fluidization Technology - FB-10", T. Knowlton, PSRI Ed, EI Sympoium Serie, (2013). Thi Article i brought to you for free and open acce by the Refereed Proceeding at EI Digital Archive. It ha been accepted for incluion in 10th International onference on irculating Fluidized Bed and Fluidization Technology - FB-10 by an authorized adminitrator of EI Digital Archive. For more information, pleae contact franco@bepre.com.

2 GAS TRAER STDY IN A NON MEHANIAL L-VALVE Mohammad-Mahdi Yazdanpanah 1, Ali Hoteit 1, Ann Forret 1*,Thierry Gauthier 1, Arnaud Delebarre 2 1 IFP Énergie nouvelle, Rond-point échangeur de Solaize Solaize, France *T: + 33 (0) ; F: +33 (0) ; E: Ann.forret@ifpen.fr 2 ESSTIN, niverité Henri Poincaré, Nancy, France ABSTRAT A ga tracer (Helium) wa ued to tudy olid and ga flow in an L-valve. Effect of olid flow rate and preure drop variation on the quantity of ga in the vertical ection of the L-valve i preented. Reult were then ued to calculate the voidage of the moving olid bed in the L-valve vertical ection. INTRODTION The control of olid flow rate i an important element in many different olid circulating fluidized bed procee. The olid circulation control could be bet achieved through ue of the mechanical valve a in ome mature catalytic proce like F (1). However, ue of the mechanical valve i more complex and limited in high temperature procee (>800 ) due to the material election and reitance problem. hemical Looping ombution (L) i an example of thi kind. L i a promiing novel combution technology involving inherent eparation of the O 2 (2). An oxygen carrier, motly a metal oxide, tranport oxygen from the air reactor to the fuel reactor while circulating between them. The olid tranport rate control the extent of reaction converion in each reactor while controlling the energy balance in the ytem. The control of particle circulation rate i hence one of the mot important factor in the L ytem. The non-mechanical valve are a category of olid flow control device employing no mechanically moving part (3). Accordingly, they can be eaily adapted to high temperature condition uch a L. An external ga injection i ued to control olid flow rate in thee valve. L-valve i one of the poible choice for L proce among different exiting non-mechanical valve. It i imple in deign, eay to operate, effective in olid flow control and require minimum maintenance (4;5). Variou tudie on the L-valve behavior have been publihed to date (3;5-9). Thee tudie motly illutrate the effect of operating and geometrical parameter on the olid flow rate actuated in the L-valve and the correponding preure drop (3;6-8). The flow in the horizontal ection of the L-valve i an important ubject in thee tudie. Three flow pattern have been ditinguihed in horizontal flow baed on the aeration rate including: fat moving tream flow, dune-ripple flow, and dune-lug flow (5;7;9). The olid flow in vertical ection of the L-valve (tandpipe) i in downward cocurrent or counter current olid and ga flow. The particle flow in the dene

3 phae mode due to the gravity force. The preure drop in thi ection i developed through the relative movement of ga and olid (3). A olid are not fluidized, change in the relative olid ga velocity can change the preure drop acro the olid bed. Ergun equation (10) modified for lip velocitie i ued to calculate the preure drop in the tandpipe of the L-valve (3;7;11). Ga-olid flow in a tandpipe can be largely divided into non-fluidized and fluidized flow. The non-fluidized bed flow are divided into the packed bed and the tranitional packed bed flow by lip velocity (12). The lip velocity (v l ) i defined a the intertitial ga velocity (v g ) minu the olid intertitial velocity (v ) with downward olid velocity a poitive direction. Packed bed flow occur when the intertitial lip velocity i poitive and ga preure i higher at the top of the tandpipe than at the bottom. The bed poroity i believed to remain contant regardle of v l value in thi cae (12). The tranitional packed bed flow occur when v l i negative, and the ga preure at the bottom of the tandpipe i higher than that at the top (13). Different correlation have been developed to etimate the voidage of the olid bed in a tandpipe. Some of the exiting correlation in the literature are lited in Table 1. Table 1: orrelation of olid bed voidage in a tandpipe/ downcomer (p). orrelation ondition Reference ( mf ) SP = + v linear relation between Knowlton T. M. l v ga velocity and voidage and Hiran I. (3) SP 1 = 1 R R = 3.1( d p ρ ) 0.5 R = 23.94( d ρ ) mf 0.3 p for t t for < t o t 0.6 o > t d d Ar = p = d d, 18Re + 2.7Re d pρ g Qp p Re = ± + ν µ g A 1 p D p = d d 0.2, EXPERIMENTAL SETP d d 0.6 Ar = 18Re + 2.7Re Sand particle d p (503, 232, 90) µm (2818,2730,2365)kg/m 3 Geldart group A Alumina/Hydrated alumina/ F catalyt d p (34.11,46.66, 54) µm (2770.4, , ) kg/m 3 Sand particle d p (95) µm, (2260) kg/m 3 Yagi (14) Li et al. (15) han. W. et al. (16) IFP EN and TOTAL are collaborating on an R&D project on L. A novel L deign baed on the interconnected bubbling fluidized bed wa developed at IFP EN to build a 10 kw th pilot plant. The main concern wa to inure an independent olid flow control, and to achieve minimum ga leakage between the air reactor and the fuel reactor. A cold prototype wa contructed with identical geometrical dimenion a the hot 10 kw th L prototype. The ytem i chematically illutrated in Figure 1. Detailed explanation of the ytem and function of each ection can be find elewhere (17). Helium wa ued to trace the ga flow in different L-valve ection. Helium flow rate

4 wa controlled by mean of a rotameter at fixed preure fed from a bottle with 99.99% Helium purity. A Protec TM Helium Sniffer Leak Detector wa ued a the Helium meaurement device. It i capable of detecting He ucked in the device though a niffer line by mean of a ma pectrometer. The Helium injection and detection point are illutrated in Figure 1. Silica and wa ued a the olid in the current tudy. The propertie of particle are lited in Table 2. He detection Table 2: Propertie of and particle ued in thi tudy. Property Value (kg/m 3 ) 2650 d (µm) 321 d 50 (µm) 334 mf (m/) mf (free ettled) 0.46 t (tapped) 0.40 (phericity) 0.76 GAS TRAING IN THE L-VALVE Section I Section II He Injection D R1 0.1 m H R1 1.0 m D lv m H lv 1.27m L H 0.14 m 2.15 m Figure 1: The cheme of the L cold flow prototype. Different Helium injection and detection poition are indicated in the figure. The ga and olid flow in two main ection of L-valve were experimentally invetigated. The firt ection i the vertical part above the external ga injection point. Second ection i the vertical ection below external ga injection point together with elbow and horizontal pipe of the L-valve, (Figure 1). Tracer ga (Helium) wa injected into the fluidization ga of the reactor with low concentration of 0.33 vol. %. Low inlet concentration of tracer ga wa ued to enure that the tracer ga doe not modify ignificantly propertie of the fluidization ga (air). Helium wa then detected in the cyclone ga exit (Figure 1). Preure drop in the tandpipe (P v ) i a variable parameter that adjut to match the preure balance acro the olid circulation loop. hange of P v will in turn change the quantity of ga paing through thi ection. Serie of tet were conducted where the ga flow rate in the vertical ection of the L-valve wa meaured for different preure drop acro the element. A unique feature of the current L intallation i the poibility to adjut P v through variation of the preure drop acro the reactor (P R ) by change of the olid height in the reactor. Thi permit control of preure drop acro the tandpipe independently from the L-valve external aeration. The meaurement were conducted during the teady tate olid circulation for H L

5 different bed height in the reactor with contant external aeration rate in the L-valve (Q lv ). The uperficial velocity of the ga and preure drop in the vertical ection of the L-valve are illutrated in Figure 2. Increae in P R caue the P v to reduce from +60 mbar to 30 mbar. The ga flow change baed on the preure drop acro the tandpipe. Two zone can be ditinguihed for ga flow in the tandpipe ( v ). In the cae of high preure drop in the tandpipe, ga flow upward in the tandpipe and no Helium wa detected in the ga exit of the cyclone (yc1 in Figure 1). A the preure drop reduce below a critical value, ga tart flowing downward in the tandpipe and progreively increae a the preure drop reduce further in the tandpipe. The variation of the intertitial velocitie in the tandpipe i illutrated in Figure 3 for the ame tet erie above. In the cae of negative preure drop, the lip velocity i poitive and the ga velocity i higher than the olid velocity. A the preure drop in the reactor increae, lip velocity reduce progreively to zero (the olid and the ga have the ame velocity). At higher reactor preure drop, the lip velocity become negative. In thi cae, the particle flow fater than the ga. Finally, the relative velocity increae more than the olid velocity in value, which mean the ga flow upward in the tandpipe in the oppoite direction of the olid flow. Pv (mbar) Zone I Zone II v (m/) V (m/) Vl V Vg DPR (mbar) 0.00 Figure 2: The effect of the reactor preure drop on the preure drop and the ga flow in the vertical ection of the L-valve with lv = 0.2 m/ DPv (mbar) Figure 3: The change of the intertitial velocitie in the tandpipe due to the change of the tandpipe preure drop with lv = 0.2 m/ and G = kg/m². (equivalent to variation of V ). The variation of the ga flow through the vertical ection of the L-valve change the total ga flow around the bend of the L-valve. The olid flow rate in the L-valve i controlled by the ga flow rate through the bend of the L-valve (Q H ) (3). Therefore, the olid flow actuated in the L-valve will be affected due to the variation of the ga flow in the L-valve( V ). Thi phenomenon i hown in Figure 3 where increae of P v from -30 to 33 mbar reduce olid velocity from to m/ equivalent to olid flux variation of 64 to 43 kg/m².. The internal and the external L-valve air flow rate veru the olid flux in the L- valve are preented in Figure 4 for two tet erie. In the firt erie, the olid flow rate wa controlled by the variation of the external L-valve aeration ( lv ). A expected, increae in lv increae olid flux. Moreover, the ga flow rate in the tandpipe increae a olid entrain more gae downward in the tandpipe. Ga

6 flow rate in the horizontal ection of the L-valve which i um of lv and v increae in the ame order. The external L-valve aeration ( lv '), wa kept contant in the econd erie of experiment preented in the Figure 4. The tandpipe ga flow rate wa then varied by adjuting the preure drop acro the tandpipe through change in the reactor preure drop. Accordingly, for a contant external aeration, horizontal ga flow rate in the L-valve increae a v ' increae. Thi demontrate that for a contant external aeration of the L-valve, the olid flow rate can be varied through variation of the v impoed by change of preure drop acro the tandpipe. Therefore, the olid flow rate actuated in the L-valve i not only a function of the external aeration but alo preure drop acro the L-valve. Knowlton (3;4;18) ha explained thi phenomenon being due to the fact that the olid flow rate in the L-valve i controlled by the quantity of the ga flowing around the bed of the L-valve (Q H ). Thi theory i well illutrated in the Figure 4 where the Q H curve lay on the ame line for both of the experimental erie. Standpipe ga flow variation i teeper in cae of preure drop change compared to the external aeration change for unit change of the olid flux. Thi i due to the fact that Q v mut compenate required Q H variation for a unit change of olid flux while external aeration i contant. Thee reult illutrate that a deired olid flow rate in the L-valve can be achieved by different configuration of the external aeration and the ga flow in the tandpipe. Thi i of particular interet in cae of L proce where the ga flow out of the reactor i conidered a a leakage and i deired to be minimized. Therefore, a proper control of preure drop acro the ytem together with appropriate external aeration help to optimize thi ga leakage out of the reactor. VOIDAGE OF THE MOVING SOLID BED (m/) The experimentally meaured preure drop, ga flow rate and olid flow rate value were ued to calculate the average voidage of the moving olid bed ( p ) baed on the Ergun equation. A dicued before, the current intallation permit to control the preure drop acro the tandpipe independently from Q lv. ing thi feature, the voidage of the olid bed wa meaured for two non-fluidized olid flow regime (Figure 5). The packed bed olid flow regime wa reached when the preure drop acro the tandpipe wa negative, correponding to poitive lip velocitie (ee Figure 3). Thi correpond to Zone II illutrated in Figure 5. The lip velocity i poitive in thi regime, a ga downward flow i fater than olid velocity (ee Figure 3). The reulting moving bed voidage in thi cae i contant and correpond roughly to the tapped bed voidage. In other word, ga flow puhe to H R =cte: Q lv =cte: H lv H' lv' v v' G (kg/m².) Figure 4: The variation of the olid flux veru the meaured ga flow velocity in the L-valve for two experimental erie: the change in external L-valve aeration with the fixed olid height (,, ) and the variation of the preure drop in the tandpipe with fixed external aeration (,, ). (m/)

7 pack moving olid tighter together in thi regime. Tranition packed bed olid flow attained by impoing poitive preure 60% drop in the tandpipe. Slip velocitie wa negative in thi region (ee Figure 3). In Zone I (Vl <0) Zone II mf (Vl >0) thi cae, reactor preure drop wa 50% kept contant and olid flow and preure drop variation wa adjuted through change of Q lv. Reulting 40% variation of average voidage i illutrated v mf in Figure 5, Zone I. Slip velocity i 30% negative in thi region, meaning that olid particle have higher velocity than Vl (m/) ga. A lip velocity increae in value, Figure 5: The experimental reult of voidage of olid bed expend from the variation of the average voidage of tapped bed voidage toward bed voidage moving olid bed in the tandpipe of the at the minimum fluidization condition. L-valve. The correlation lited in the Table 1 were then compared with experimental reult in Figure 6. Linear correlation propoed by Knowlton and Hiran (3) reult in cloet prediction. orrelation of Li et al. (15) and han et al. (16) give a good etimate of the voidage variation trend, they however over/under etimate the voidage value. The ignificant difference oberved in ome cae i motly due to different operating condition in thi tet and developed correlation. L-VALVE LIMITING OPERATION The L-valve operation i reported to be limited due to different limiting condition including: fluidization of vertical arm (3), limit of olid flow rate into the L-valve (8), or untable operation of the inclined ection of the L-valve (19) (in cae of hybrid tandpipe a in the current configuration). However, thee limit depend on the preure drop acro the tandpipe of the L-valve which i a dependent variable parameter. Accordingly, the upper operation limit of the L-valve can be adjuted depending upon the operating condition. A tet wa carried out to invetigate continuou operation of the L-valve in the limiting condition. External ga flow rate wa et to a high value of m/. The reulting preure drop variation and ga flow in the tandpipe i illutrated in Figure 7. An ocillatory behavior of the preure drop and ga the flow wa oberved in the ytem. Moreover, height of the moving bed in the tandpipe wa alo behaving in an ocillatory mode. Once the L-valve wa opened, olid height tarted to gradually decreae while preure drop wa increaing acro the tandpipe. The olid height finally got to a minimum level where it tarted to raie again. The olid height then increaed till it reached the top of the L-valve where the olid height tarted to decreae again. Thi unteady phenomenon repeated itelf in an ocillatory mode (%) (%) 80% 60% 40% 20% Li et al. Yagi Knowlton han et al. 0% Vl (m/) Figure 6: The experimental reult of variation of the voidage of the moving olid bed in the tandpipe of the L-valve compared with the literature correlation.

8 a illutrated in Figure 7. When a very high ga flow rate i injected into the L-valve, a very high olid flow rate i actuated in the L-valve exit (W ) higher than olid flow into the L-valve (W in ). The olid height in the tandpipe (H ) then reduce, reulting in increae of the preure drop per unit height of the tandpipe (P/H ). onequently, the downward ga flow rate in the tandpipe ( v ) reduce gradually, get to zero and finally ga flow upward in the tandpipe. Accordingly, H reduce, reulting in reduction of olid flow rate actuated in the L-valve. The olid inventory in the reactor then increae. onequently, preure drop in the reactor increae, reulting in reduction of the total preure drop in the tandpipe. A the olid flow rate reduce, W in exceed W out and tandpipe tart to fill. A the olid height in the tandpipe increae, P/H reduce. Therefore, more ga pae downward, and the olid flow rate increae gradually. Thi continue until olid height get it maximum once tandpipe i filled with the olid and again W out exceed W in. Once more, the ame cycle tart to repeat again. At the ame time, the econd L-valve (lv2 in Figure 1) wa operating normally with an average olid flow rate equal to that of the firt L-valve (lv1) which wa operating in an untable manner. The table operation of the econd L-valve wa due to proper adjutment of the external aeration and the preure drop along the tandpipe. The external air flow velocity wa et to m/ (compared to m/ in the lv1) and the preure drop in the reactor wa lightly higher in the reactor R2 compared to R1. Thi illutrate importance of proper election of the operating condition in high olid flow rate operation to avoid poible intable intabilitie. Thi i of particular interet in the L proce where a high olid circulation rate i deired between two reactor to tranfer the required oxygen for combution. ONLSION DP (mbar) PR Pv PL PH v t () The reult of experimental tudy of an L-valve in a chemical looping combution cold prototype wa preented in thi work. Helium wa ued a ga tracer to experimentally meaure quantity of ga flow in the different ection of the L-valve. Ga flow rate in the vertical ection of the L-valve increaed by increaing olid flow rate or by decreaing preure drop acro the vertical ection of the L-valve. Experimental reult were then ued to calculate the average voidage of the moving olid bed in the vertical arm of the L-valve. Voidage variation in two regime of packed bed flow and tranitional packed bed flow were preented. Finally, ocillatory operation of L-valve in the limiting condition wa preented in term of ga and olid flow and preure drop Figure 7: Ocillatory operation of L-valve in limiting condition of lv = m/. v (m/) NOTATION G : olid flux, kg/m².. H : Height of olid bed in the tandpipe, m. V g : intertitial ga flow rate, m/. V : intertitial olid velocity, m/.

9 Q lv : The external L-valve aeration, Nm 3 /h. lv : external aeration flow velocity calculated baed on the L-valve area, m/. H : ga flow velocity in the horizontal ection of the L-valve, m/. v : ga flow velocity in the vertical ection of the L-valve, m/. V l : ga-olid lip velocity, m/. REFERENES P R : preure drop in the reactor, mbar. P v : preure drop in he vertical arm of the L-valve, mbar. : voidage of free ettled olid bed. p : voidage of olid bed in the tandpipe. t : voidage of tapped olid bed. 1. Gauthier T., Bayle J., Leroy P. F: Fluidization Phenomena and Technologie. Oil & Ga Science and Technology - Rev IFP 2000;55(2): Lyngfelt A., Leckner Bo, Mattion T. A Fuidized-bed combution proce with inherent O2 eparation; application of chemical-looping combution. hemical Engineering Science 2001;56: Solid Flow ontrol uing a Nonmechanical L-valve. Ninth Synthetic Pipeline Ga Sympoium; hicago, illinoi Knowlton T.M. Feeding and Dicharge of Solid ing Nonmechanical Valve. Intitute of Ga Technology hicago, Illionoi, Intitute of Ga Technology. 5. Yang Wen-hing, Knowlton Ted M. L-valve equation. Powder Technology 1993;77: han W, Seville J, Fan X, Baeyen J. Particle motion in L-valve a oberved by poitron emiion particle tracking. Powder Technology 2009;193(2): Geldart D., Jone P. The behaviour of L-valve with granular olid. Powder Technology 1991;67: Smolder K, Baeyen J. The Operation of L-valve to ontrol Standpipe Flow. Advaced Powder technology 1995;6(03): Yang TY, Leu LP. Multi-reolution analyi of wavelet tranform on preure fluctuation in an L-valve. International Journal of Multiphae Flow 2008;34(6): Ergun S. Fluid flow through packed column. hemical Engineering Proce 1952;48(2): Smolder K, Baeyen J. The Operation of L-valve to ontrol Standpipe Flow. Advaced Powder technology 1995;6(03): Kojabahian. Propertie of dene-phae fluidized olid in vertical downflow Maachuett Int. of Technology; Zhang J.Y., Rudolph V. Tranitional Packed Bed Flow in Standpipe. an J of hem Eng, 1991;69: Yagi S. hemical Machinery, Japon 1952;16: Li Y., Lu Y., Wang F., Han K., Mi W., hen X. et al. Behavior of ga-olid flow in the downcomer of a circulating fluidized bed with a V-valve. Powder Technology 1997;91: han.w., Seville J., Fan X., Baeyen J. Solid particle motion in a tandpipe a oberved by Poitron Emiion Particle Tracking. Powder Technology 2009;194(1-2): Yazdanpanah M.M., Hoteit A., Forret A., Delebarre A., Gauthier T. Experimental Invetigation on a Novel hemical Looping ombution onfiguration. OGST - Revue d'ifp Energie nouvelle Wet and Dry Limetone Feeding ing an L-valve. Sixth International onference on Fluidized Bed ombution; Atlanta, Georgia Knowlton T.M. Standpipe and Nonmechanical Valve. In: Yang W-, editor. Handbook of Fluidization and Fluid-Particle Sytem. NEW YORK: MAREL DEKKER, IN; p. 576.