Instructors : Dr. Su Chin Chen Dr. Jack Jie Dar Cheng. Dr. Paris Honglay Chen Dr. Der Guey LIN

Transcription

1 Instructors : Dr. Su Chin Chen Dr. Jack Jie Dar Cheng Dr. Paris Honglay Chen Dr. Der Guey LIN 1

2 CONTENT 1. INTRODUCTION 2. LITERATURE REVIEW 3. METHODOLOGY 4. RESULTS & DISCUSSION 5. CONCLUSION 2

3 1. INTRODUCTION Short circuiting significance different types of reactors Short circuiting problems Simulate short circuiting in lab Research purpose: To invent a method for short circuiting comparison 3

4 2. LITERATURE REVIEW 2.1 The definition of short circuiting 2.2 The effect of short circuiting 2.3 The difficulty of short circuiting evaluation 2.4 Differentiation criteria for reactor type 2.5 Available short circuiting indexes 4

5 2.1 THE DEFINITION OF SHORT CIRCUITING Non ideal flow 1.Density currents 2.Circulation 3.Inadequate mixing 4.Poor design 5.Axial Aildispersioni Source: Metcalf & Eddy,

6 2.2 THE EFFECT OF SHORT CIRCUITING Hindrances to a successful reactor design (Persson, 2000) Reaction time dead zones (Metcalf & Eddy, 2003) Reactor volume reduce function (Dierberg et al., 2005) poor hydraulic efficiency (Singh et al., 2009) Watershed Flood control: reservoir, retention basin (Shutes et al., 1999) Erosion control: sedimentation ti tank k(fitch, 1957) Quality control: wetland, self purification (Wong et al., 1999) 6

7 2.3 THE DIFFICULTY OF SHORT CIRCUITING EVALUATION Each index show fuzzy result Inde ex value Short circuiting indexes Different reactors Source: Teixeira and Siqueira,

8 2.4 DIFFERENTIATION CRITERIA FOR REACTOR TYPE MDI =22 (Metcalf & Eddy, 2003) Indexes criteria for differentiation of reactor types (Tsai et al., 2009): 1. N: λ: MDI: V e : 5.6% 5. d: 0.5 8

9 2.5 AVAILABLE SHORT CIRCUITING INDEXES 13available indexes 1.Different ideal values Ta and Brignal index (S tb ) (Ta and Brignal, 1998; Persson, 2000) θ 10 index (θ 10 )(Kim and Bae, 2007) Thirumurthi s index (S th ) (Thirumurthi, 1969; Burrows et al., 1999; Wang 6 indexes et al., 2009) 5 indexes 2 indexes Index of short circuiting (τ i ) (Metcalf & Eddy, 2003) index of modal retention time (τ p ) (Metcalf & Eddy, 2003; Wang et al., 2009) 2. Same ideal values Hydraulic efficiency (λ) (Persson et al., 1999; Singh et al., 2009) Effective volume ratio (e) (Thackston et al., 1987) Index of short circuiting flow (Q sc ) (Cauchie et al., 2000) Dead volume (V d ) (Cauchie et al., 2000) Index of average retention time (τ c ) (Metcalf & Eddy, 2003) 3. Seldom used index θ 50 index (θ 50 ) (Stamou, 2008) Hold ldback parameter (HBP) (Stamou and Adams, 1988) The Groche s index (ICC) (Stamou and Rodi, 1984) 9

10 3. METHODOLOGY Model PFR Experimental design for reactor analysis HRP CSTR Tracer Reactor analysis Residence time distribution curves Hydraulic indexes es of short circuiting * Reactor differentiation i i criteria 10

11 Operational factor of tracer study Operational factor HRP CSTR scale lab lab detention time 4hr 4hr reactor design Paddle wheel with recirculation 4 L up flow flask water level 15 cm Low energy wonder water volume 199 L 4L inflow velocity 820cc cc./min 16.8cc cc./min tracer NaCl NaCl inflow type spike spike mixing speed 10 cm/sec magnetic mixer effluent measure interval 15 min 15 min 11

12 The process of comparison Step 1 Reactor type Step 2 Distance method Step 3 The degree of short-circuiting among different reactors 12

13 4. RESULTS & DISCUSSION 4.1 Residence time distribution 4.2 Hydraulic performance indexes 13

14 4.1 RESIDENCE TIME DISTRIBUTION E( (t) t peak(cstr) i(cstr) =15 =15 min min d CSTR =15min =t peak(hrp) i(hrp) d HRP =225min Theoretical retention time E(t) (ideal CSTR) E(t) (CSTR) E(t) (HRP) E(t) (ideal PFR) E(t) (real PFR) Time, min 14

15 4.2 HYDRAULIC PERFORMANCE INDEXES Different ideal values indifferent ideal reactors 422S Same ideal values in different ideal reactors Seldom used indexes 15

16 4.2.1 Different ideal values in different ideal reactors 1. Ta and Brignal index (S tb ) 2. θ 10 index (θ 10 ) 3. Thirumurthi s index (S th ) 4. Index of short circuiting (τ i ) 5. Index of modal dlretention time (τ p ) 6. Hd Hydraulic efficiency i (λ) 16

17 1. Ta and Brignal index (S tb ) t 16 0 Ideal CSTR Reservoir Design (Ta and Brignal, 1998) 16% & 50% S tb=t 16/ /t 50 tracer HRP: Recirculation 2. Outlet design d HRP = HRP S tb d CSTR = CSTR: Ideal PFR More short circuiting in the HRP t 16 = t 50 (Persson, 2000) 17

18 2. θ 10 index (θ 10 ) Pond Evaluation (Kim and Bae, 2007) θ 10 =t 10 / τ t 10 = τ Ideal CSTR HRP: Theoretical retention time d HRP = θ d CSTR = 0.02 CSTR: More short circuiting in the HRP t 10 = τ (Kim and Bae, 2007) Ideal PFR 18

19 3. Thirumurthi s index (S th ) Activated sludge plants design (Thirumurthi, 1969) d HRP = S th = 1 t peak /t mean HRP: t peak 0 Ideal CSTR S th Ideal PFR t peak = t mean CSTR: d CSTR = More short circuiting in the HRP 19

20 4. Index of short circuiting (τ i ) & index of modal retention time (τ p ) t i = t p = 0 τ i = t i / τ τ p = t p / τ t HRP: i = t p Ideal CSTR d HRP = τ i, τ p t i = t p d CSTR = CSTR CSTR: t i = t p More short circuiting in the HRP t i = t p = τ Ideal PFR 20

21 5. Hydraulic efficiency (λ) Wetland evaluation (Persson et al., 1999) λ = e (1 1/N) e = 1, N = 1 d CSTR>d HRP Ideal CSTR HRP: d HRP = Ideal PFR λ d CSTR = CSTR: e = 1, N = 21

22 Complexity Explanation of error in λ Pool index Tank in series number λ = e (1 1/N) 1/N) 4th paper Effective volume ratio Offset effect Dead volume effect 22

23 Results of different ideal values in Index different ideal reactors Ideal Ideal Lab HRP PFR CSTR (spike) TB index (S tb ) 1 ~ θ Thirumurthi s index (S th ) Lab CSTR evaluation reference (spike) d HRP > d CSTR Ta and Brignal, 1998; (0.743>0.251) Persson, 2000 d HRP > d CSTR (0.846>0.020) d HRP > d CSTR (0.949>0.058) Kim and Bae, 2007 Thirumurthi, 1969; Burrows et al., 1999; Wang et al., 2009 Index of short d 1 0 <0.063 <0.063 HRP > d CSTR Metcalf & Eddy, 2003 circuiting (τ i ) (0.937>0.063) Index of modal d HRP > d CSTR Metcalf & Eddy, 2003; 1 0 <0.063 <0.063 retention time (τ p ) (0.937>0.063) Wang et al., 2009 Hydraulic efficiency d CSTR > d HRP Persson et al., 1999; (λ) (0.446>0.424) Singh et al., Feasibility of distance method 2. λ index is not recommended 23

24 4.2.2 Same ideal values in different ideal reactors 1. Effective volume ratio (e) 2. Index of short circuiting flow (Q sc ) 3. Dead volume (V d ) 4. Index of average retention time (τ c ) 5. θ 50 index (θ 50 ) 24

25 1. Effective volume ratio (e) 1. Recirculation Shallow outdoor basin 2. Axial (Thackston dispersion et al., 1987) 3. Dead zone e > 1 Ideal t mean = τ PFR d HRP = e =t mean / τ mean/ HRP: e 0 Ideal 1 2 CSTR CSTR: t mean = τ d CSTR = MoreUp flow short circuiting design in the e HRP > 1 25

26 2. Index of short circuiting flow (Q sc ) Q sc = 1 τ /t mean Adapted from Cemagref (1983) Ideal PFR t mean = τ d HRP = 17.8% HRP: 17.8% Performance of the aerated stabilisation pond (Cauchie et al., 2000) 0% 50% 100% Ideal CSTR: CSTR t mean = τ7.1% Q sc d CSTR = 71% 7.1% More short circuiting in the HRP 26

27 3. Dead volume (V d ) d V d = 1 t mean /τ Adapted from Cemagref (1983) 1. t mean > τ : no dead zone (Cemagref, 1983) 2. Dead zone was observed 3. Metcalf & Eddy definition of short circuiting 4. d HRP = > d CSTR = More short circuiting in the HRP 27

28 4. Index of average retention time (τ c ) τ c =t centroid / τ t centroid = τ Ideal PFR d HRP = HRP: τ c 0 Ideal 1 2 CSTR CSTR: d CSTR = t centroid = τ More short circuiting in the HRP 28

29 5. θ 50 index (θ 50 ) θ 50 Water process tank (Stamou, 2008) θ 50 =t 50 / τ HRP: t 50 = τ CSTR: d HRP = Ideal PFR Ideal CSTR: (From this study) d CSTR = d CSTR >d HRP d CSTR >d HRP t 50 = τ d CSTR = 0.16 Ideal CSTR: 1 (Stamou, 2008) 29

30 Limitation of θ 50 inconsistent lue Index val Short circuit level Source: Teixeira and Siqueira,

31 Results of same ideal values in different ideal reactors Index Ideal PFR Ideal CSTR Lab HRP Lab CSTR evaluation reference Effective volume d HRP > d CSTR Thackston ratio (e) (0.217>0.077) et al., 1987 Index of short d 0% 0% 17.8% 7.1% HRP >d CSTR Cauchie et circuiting flow (Q sc ) (0.178>0.071) 071) al., 2000 d Dead volume (V d ) 0% 0% HRP > d CSTR Cauchie et (0.217>0.077) al., 2000 Index of average d HRP > d CSTR Metcalf & retention time (0.222 > 0.082) Eddy, d CSTR > d HRP Stamou, θ 50 index (0.59) (0.160/0.252>0.001) Feasibility of distance method 2. θ 50 index is not recommended 31

32 4.2.3 Seldom used indexes 1. Hold back parameter (HBP) 2. The Groche s index (ICC) 32

33 Results in the category of seldom used indexes Index definition range Ideal PFR Ideal CSTR Lab HRP (spike) Lab A CSTR (spike) Area difference evaluation Ref. Hold back parameter (HBP) Groche s index (ICC) The area below the cumulative RTD function from 0<θ<1 Distance d HRP >d CSTR ( > ) Measurement interval The area below the Symmetry RTD of RTD d = d function HRP CSTR between t=t (0 = 0) p (t p t i ) and t=t p +(t p t i ) Indirect tindex Stamou and Adams, 1988 Stamou and Rodi,

34 General discussion 1. Mathematical basis in the distance method 2. Mechanism in different categories of short circuiting index 34

35 1. Mathematical basis in the distance method E(t) E(t) ()(ideal CSTR) E(t) (real PFR) Time, min 1. Comparison in the same type of distribution 2. No short circuiting in ideal reactors (Metcalf & Eddy,

36 2. Mechanism in different categories of short circuiting i i indexes Different ideal values in different ideal reactors (Front part tracer) Circulation effect Same ideal values in different ideal reactors (Whole part of tracer) t i, t 10, t 16, t peak Effective volume t mean, t centroid Seldom used index (area difference) distance 36

37 5. CONCLUSION 1. Reactor type differentiation is essential 2. Demonstrate the feasibility distance method 3. Evaluation of short circuiting 4. Invention of new method 37

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39 Journal submission Journal Bioprocess and Biosystems Engineering Application date January 22, 2010 Process Inthereview process 39

40 Thanks for your attention 40