mbchang@ncuen.ncu.edu.tw 03-4227151 4227151-46634663 300
Introduction of Plasmas 2
600~800 200~400 (< () ) ~ ~ ~ ~ ~ ~~~ 1. 1. 2. 2. 3
( ) >> ( ) 4
v.s. 100 % 10-4 ~ 10-1 % 1 10-6 ~ 10-2 torr * (Tg) > 10,000 K ~300 K ( ) (Te) Te = Tg Te/Tg = 10~100 *: 1 5
1. (NO x, SO 2 ) 2. (VOCs) 3. (NH 3 ) 4. (PFCs) 5. (Odor) 6. (NOx, PAHs) 7. (CO 2, CH 4 ) 8. (Dioxin) 9. (O 3 ) 6
7
8
e + pollutant products e + O 2 O( 1 D) + O + e e + H 2 O OH + H + e e + M M + + 2e O, O( 1 D), OH, M + + pollutant products O( 1 D) + H 2 O OH + OH O + O 2 + M O 3 + M O 3 + pollutant products 9
The gas stream contains 7% CO 2, 8% O 2, 6% H 2 O, 400 ppm CO, 260 ppm NO, 133 ppm H 2, 0-1100 ppm C 3 H 6 and N 2 as balanced gas. 10
Major Chemical Reactions (Elastic Collision) (Excitation) (Ionization) (Relaxation) (Dissociation) (Recombination) 11
(Elastic Collision) e + A e + A (Ionization) 1) e + A 2e + A + 2) h+ A e + A + 12
(Excitation) e + A e + A* (*: ) (Relaxation) A* A + h() 13
(Recombination) e + O 2+ 2 O ( ) F - + CF 4+ CF 4 + F ( ) e + A + A + h( ) e + A + + M A + M ( ) 14
Plasma Reactors 15
1. (electron beam, E-beam) E 1. 2. (corona discharge) 2. 3. (dielectric barrier discharge, DBD) 3. 4. (radio-frequency plasma, rf plasma) 4. 5. (microwave discharge) 5. 6. (Inductively Coupled Plasma, ICP) 6. 1-3 4-6 16
vs. 17
(Pressure) (V/cm) (Electric Field) * (Td) (Reduced Field) (Cold Plasmas) <10 mbar 1 bar < 100 torr 1 bar 10 50 0.5~2 (ev) (5,000~20,000 (Electron Energy) K) (cm -3 ) (Electron Density) 0.5~50,000 (variable) 2~2,000 (variable) 5 (variable) 10 8 ~10 11 10 13 (variable) Small 10-6 ~10-5 (Degree of Ionization) (variable) - 0.1~100,000-1~500 ~1 ev 1~10 10 8 ~10 10 10 14-10 -4 18
19
SO /NO 2 x 20
21
RF 22
DBD 1. 2. 3. 4. 5. 23
DBD (a) pulsed corona (b) DBD (c) packed-bed plasma
(a) pulsed corona (a) (b) DBD (b) (c) multipoint-to-plane (c) 25
26
NOx 27
28 28 52.6% 24.4% 14.0% 9.0% 47% 53% 52.6% 24.4% 14.0% 9.0% 47% 53% NOx 70~80
1. 2. 3. 29
(Pre-Combustion Treatment) fuel NO x (Combustion Modification) thermal NO x (Post-Combustion Treatment) 1. SCR SNCR 2. 30
31
( 1998) 32
( 1998) 33
( 1999) De-SOx > 90% (Mok et al., 1999) 34
(CPC) Combined Plasma Catalysis 35
36
de-nox Test Conditions Summary ( ) Item Value Unit Configuration Conversion (%) NO 260 ppm Plasma 26 CO 400 ppm Plasma+Cu-ZSM 5 H 2 133 ppm Plasma+"A" 50 Ar 1 % Plasma+"A"+Cu-ZSM 46 O 2 8 % CO 2 7 % C 3 H 6 1575 ppm C 3 H 8 525 ppm H 2 O 7 % N 2 Balance Temperature 180 Flow Rate 2 slpm Energy Deposition 30 J/L DBD test device of Ford Motor Co. The device consists of a pair of alumina plates, 18 mm wide by 90 mm long. Gap = 1.3 mm. Catalyst materials have been coated on cordierite monoliths placed downstream of the plasma device. Two proprietary catalysts are used: Cu-ZSM is a copper zeolite formulation provided by a catalyst supplier. Test piece is 25 mm long by 25 mm diameter. A is a proprietary catalyst formulation developed by the CRADA partners. Two pieces used are 25 mm long by 25 mm diameter. 37
(HC/NOx) Chemical kinetics modeling of the plasma oxidation of NO to NO 2 in a gas mixture simulating diesel engine exhausts, using propene additive. Initial NO = 600/100 ppm, in 10% O 2, 10% CO 2, 5% H 2 O, balance N 2. 38
ev/molecule 39
NOx (US$/kW) Scale*(kW) 3500 800 Frank 8000 50 estimate 5000 60 Synergetic Tech. Inc. 5000 60 Synergetic Tech. Inc. 300 1000 Thermal Energy Inc. 40
1500 1200 900 600 300 0 500 MW 41
NOx/SOx 500 MW 1 2 3 4 NO ppm 300 200 230 300 NO x % 60 70 80 80 SO x ppm 1000 800 1000 3050 SO x % 90 95 95 90 ** g-no/kwh 20 374 56 - Nm 3 /h 600 12 20,000 1.9x10 6 * Data obtained from 1. (Dinelli et al, 1990), 2. (Chang et al., 1998), 3.(Ebara Co., 1998), 4. (EPRI, 1983; JMIA-EEI,1991). ** Note: All electric power is assumed to contribute to the removal of NO x. 42
VOC 43
44
VOCs ( ITIS / ) 144 68 6 48 1947 31 100 379 72 620 427 892 24 2111 431 458 155 547 118 574 18 3219 178 89 45
VOCs 70~ 90% NO x / ~70% NO x / VOC UV UV 46
Wire-Tube DBD VOCs Type of Reactor (ref) Treatment Gas (ppm) Added Gas (%) Destruction Efficiency (%) Coaxial Silent Discharge CFC-113 Air 99 (54) Silent Discharge (12) (14) C 2 HCl CH 2 O Ar, O 2 and H 2 O 99 90 Pulsed DB wire-tube Methanol (400) dry air up to 100 (20) TCE (160) ac DB wire-tube (10) C 7 H 8 (200) C 4 H 8 O (124) C 7 H 8 and C 4 H 8 O (126/135) 80 >80 75/45 ac DB wire-tube (11) HCHO (1000) dry and humid 97 air Wire Tube (with catalyst) (Yang, 1997) DBD (Chang, 1997) Toluene, Ethyl acetate, 2-butanoue Toluene MEK up to 100 >80 DBD (Lee, 1998a, b) p-xylene dry and humid > 99 N 2 /O 2 DBD, (, 1998) p-xylene CH 3 CHO dry and humid > 99 N 2 /O 2 47
Packed Bed Plasmas VOCs Type of Reactor (ref) Corona-Packed Bed (32) Packed Bed (60) AC Packed Bed (58) Packed-bed BaTiO 3 coaxial type (16) Treatment Gas (ppm) HCl, HF SOx, Cl 2 O-xylene (200) Trichloroethylene (200) Mixed-xylene/TCE (200) CFC-113 (1000) Toluene (57-234) Methylene Chloride (500) TCE (200-1000) Methyl acetate (1000) ethyl acetate (1000) butyl acetate 1000 Packed bed, (65) CCl 4 ( 450-560) Packed bed Soda lime glass coaxial type (18) Packed Bed (with catalyst) (Yang, 1997) Packed Bed (99 %, r-al 2 O 3 ) (, 1998) TCE (130) PCE (720) Toluene, Ethyl acetate, 2-butanoue Added Gas (%) Efficiency (%) Packed Bed (99 %, r-al 2 O 3 ) p-xylene > 99 (, 1998) CH 3 CHO 48 Air Air and H 2 O Air dry and humid air pure N 2 dry and humid air dry and humid air 99 99 99 55 99 60 up to 100 up to 100 >80 >65 up to 100 99 Toluene 98.4 up to 100
VOCs. 1000000 100000 10000 1000 100 10 1 0.01 0 0.1 0 1 10 100 1000 10000 100000 1000000 0 49
VOCs ( ) 120 100 80 60 40 20 0 VOCs Ref: Kim and Chang, 1998. 50
PFC Gases GWP 100 CO 2 1 50-200 CH 4 21 12 N 2 O 310 120 CF 4 6,500 50,000 C 2 F 6 9,200 100,000 Life Time C 3 F 8 7,000 2,600-7,000 C 4 F 8 8,700 3,200 CHF 3 11,700 250-390 SF 6 23,900 3,200 NF 3 8,000 50-740 GWG Global Warming Gases 51
CO 2 (%) Conversion of CO2 (%) 30 20 10 0 14 16 18 20 Applied Voltage (kv) (kv) 150 100 50 25 (%) Selectivity (%) 60 40 20 With 4.8% O 2 CO C 2H 2 H 2 (%) Selectivity (%) 0 0 14 16 18 20 14 16 18 20 Applied Voltage (kv) (kv) Applied Voltage (kv) 60 40 20 Without O 2 CO H 2 C 2H 2 CO2 Conversion (%) CO 2 (%) 50 40 30 20 10 0 14 16 (kv) 18 Applied Voltage (kv) 20 4.8 % 0.0 % 1.0 % O 2 Content 52
% Corona CH 4 43.3 300~500 O 2 Liu Corona CH 4 2 120 O 2 Okumoto Corona -- -- O 2 /He/Ar Okumoto DBD CH 4 24 200 O 2 Zhou DBD CH 4 20 O 2 / CO 2 /CO Larkin DBD CH 4 30 O 2 /N 2 /air Ogata MW CH 4 97 -- O 2 Huang RF CH 4 98.2 750~870 O 2 Zhang DBD CH 4 50 CO 2 Gesser DBD CH 4 64 CO 2 54 0~1000 CO 2 Zhou DBD CH 4 78 -- CO 2 Chang RF CO 2 60 316 CO 2 /Ar Hsieh 53
PFCs 100 C 2 F 6 (%) Removal (%). 80 60 40 NF 3 SF 6 CF 4 20 0 0 60 120 180 240 300 (Hz) Frequency (Hz) CPC PFC/O 2 /Ar/N 2 =300ppm/20%/40%/39.97% Q CF4 =Q C2F6 =0.6 slpm, Q SF6 =Q NF3 =1.0 slpm, V=15kV 54
Conclusions 55
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