biomass co-firing studies for commercial-scale ......co-fired biomass: wood pellet, palm kernel...
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Biomass Co-firing Studies for Commercial-Scale Applications in Korea
European Biomass Conference and Exhibition(EUBCE), 11~15 June 2017, Stockholm, Sweden#2AO.8.5
Won YANG1,2
Principal researcher/Professor
1Thermochemical Energy System Group Korea Institute of Industrial Technology
2University of Science and Technology, Korea
Current issues in coal power generation Fuel diversity: Low-rank coals, Bio-SRFs
‒ Energy security‒ RPS (Renewable portfolio standard)
CO2 abatement: 37% reduction on BAU bases by 2030 (25.7% domestic and 11.3% with purchasing carbon credit)‒ CCUS‒ Biomass co-firing
• The easiest way to reduce CO2 and secure REC(Renewable energy certificate)• > 90% should be imported from other countries
‒ Efficiency enhancement: Retrofit & USC/A-USC
Emission of particulate matters: PM10 and PM2.5‒ Effects to current PM concentration in Korea have not clearly found yet‒ But causes reduction in portion of coal power generation (currently ~ 40% of total
electricity generation in Korea) by new government (10/05/2017~)
Co-firing of renewable fuels to conventional boilers
Biomass
CoalOilGas
Existing boiler
1. Parallel co-firingCombustion Steam cycle
Gasification
Pyrolysis
Liquefaction
Biomass mill
ExistingCoal mill
Pretreatment(Drying,
Pelletizing)
Dedicatedburner
Dedicatedburner
Conventionalburner
2. Indirect co-firing
3. Direct co-firing
Thermochemical conversion
Biomass-dedicated PowerGen Donghae CFBC biomass power plant(EWP): 30 MW – New plant
Several plants are under construction‒ KOSEP: Yeongdong Unit #1 (125 MW): Retrofit‒ GS EPS: Samcheok biomass-dedicated powergen (105 MW): New plant‒ …
Donghae CFBC Biomass-dedicated Power Plant (30 MW, EWP) - Currently in operation
Yeongdong Unit #1 (125 MW, Pulverized coal, KOSEP) - being retrofitted to biomass-dedicated power
generation system
Project overview: biomass co-firing to a PC power plant
Background: Obligation to produce electricity partially by renewable energy (RPS)
Purpose‒ Maximize co-firing ratio (up to > 10%)
• Securing REC(Renewable energy certificate) for power companies in KOREA
‒ Flexibility in co-fired fuels: Wood pellet PKS, EFB, and BioSRF‒ Reduce NOx in the furnace: using reburning
Applied to Samchunpo Power Plant in Korea‒ 500 MWe, Pulverized coal power plant (Owned and operated by KOEN)
Wood pellet (WP) Empty fruit bunch pellet(EFBP)
Palm kernel shell(PKS)
Walnut shell(WS) Torrefied biomass(TB)Samcheonpo Thermal Power Plant
Basic concept Tested in
‒ 80 kWt test furnace in KITECH (combustion, slagging/fouling..)‒ 1 MWt multi-burner furnace in KITECH (Co-firing methods)‒ Commercial power plant (500 MWe) in Samcheonpo TPP, KOREA)
Pulverizer(existing)
Coal (Main fuel) Existing
PC Boiler
Burnerzone
Pre-treatment(Chip, Pellet)
Reburn zone
This project
Various renewablefuels
Co-firing + Reburning- Maximizing co-firing ratio- Fuel flexibility + NOx reduction
BiomassPulverizer
1; 팜부산물2; 팜부산물펠릿3; 잣부산물4; 잣부산물펠릿5; 우드칩
1 2
3 4 5
*REC: Renewable energy certificate
Burnout zone
Direct co-firing study Process simulation for various biomasses Bench-scale experiments
‒ Co-firing: blending‒ Reburning: syngas reburning (for
observation of NOx reduction) Numerical Simulation
For 3 Co-firing Methods‒ Method 1
• No facility addition (Except biomass handling system)
• Limited co-firing ratio due to the low grindability for biomass fuels
‒ Method 2• Biomass dedicated pulverizer• No boiler modification
‒ Method 3• Traditional reburning system
BoilerPC
pulverizerPC
Burners
Coal Biomass
Coal + Biomass Mixture
BoilerPC
pulverizerPC
BurnersCoal
Biomass
Coal + Biomass Mixture
Biomasspulverizer
BoilerPC
pulverizerPC
BurnersCoal
Biomass
Separated biomass injectionBiomass
pulverizer
Overfiring air
Method 1
Method 2
Method 3
Days
0 20 40 60 80 100 120
Info
rmat
ion
of co
al m
ixtur
e
Adaro+Adaro47
Adaro+Rotosouth
Adaro+Malinau
Adaro+KPU
Adaro+Adaro49
Adaro+Adaro45
Process Simulation: Case selection
Days
0 50 100 150 200 250
Info
rmat
ion
of co
al m
ixtur
e
Adaro
Adaro+1 SBC
Adaro+2 SBCs
Adaro+3 SBCs
Others
138 days
207 days
88 days 102 days
Main coals (sub-bituminous coals) confirmed from the target plant (500MW)
a: Wet basis, b: Elemental analyzer, c: Channiwala and parnikh equation, TL: Texas lignite, WP: Wood pellet, EFBP: Empty fruit bunch pellet, PKS: Palm kernel shell, WS: Walnut shell, TB: Torrefied biomass (from torrefaction under 325 oC, 30 min)
Proximate analysis (wt.%)a Ultimate analysis (wt.%)a,b HHVc
(Kcal/kg)Fuel M VM FC A C H N S O Cl
Coal
Design 10.3 42.0 46.2 1.5 64.4 4.7 0.89 0.098 18.1 - 6249.0Adaro 17.2 39.2 40.8 2.9 57.7 4.0 0.98 0.083 17.2 - 5489.5
Adaro47 19.5 39.9 37.2 3.4 55.7 3.9 0.91 0.089 16.5 - 5310.0TL 32.0 28.0 25.0 15.0 37.7 3.0 0.71 0.900 10.7 - 3666.7
Biomass
WP 8.3 82.0 8.6 1.1 46.8 5.6 0.10 0.010 40.7 0.003 4471.8EFBP 7.7 73.5 17.8 1.0 47.0 5.7 0.28 0.004 46.3 0.015 4375.2PKS 9.8 59.6 14.8 15.9 48.4 5.7 1.04 0.014 39.1 0.018 4605.2WS 9.3 70.5 19.2 1.1 48.5 7.1 1.33 0.029 37.2 - 5110.2TB 3.1 62.5 33.3 1.1 71.2 4.6 0.01 0.010 22.3 - 6666.3
Process flow diagram on the target PCPP (gCCS)
Coupled analysis of gas side and water/steam side
Simulation procedure Basic input parameters for process simulation
‒ Physical property method: Peng-Robinson equations for gas side and IAPWS-25 for turbine island
‒ Steady-state flow‒ Same parameters on turbine island in all case: Mass flowrate of feed-water and
pressure‒ Oxygen concentration at the exit of the furnace: 3 % in case studies‒ Air leakage at the air pre-heater: 6.79 wt.%
Main simulation conditions
Parameters M.V.Combustion of low rank coals Biomass co-firing
Case1 Case2 Case3 Case4 Case5 Case6 Case7 Case8 Case9Coal
(Thermal share %) D
(100)TL
(100)A
(100)A47
(100)A+A47
(60+40)A+A47
(60+30)A+A47
(60+30)A+A47(60+30)
A+A47(60+30)
A+A47(60+30)
Biomass(Thermal share %)
WP(10)
EFBP(10)
PKS(10)
WS(10)
TB(10)
D: Design coal, TL: Texas lignite, A: Adaro coal, A47: Adaro47 coal, WP: Wood pellet, EFBP: Empty fruit bunch pellet, PKS: Palm kernel shell, WS: Walnut shell, TB: Torrefied biomass
Power consumption in the pulverizer
Power consumption of pulverizers obtained from HGI* test‒ HGI of the fuel is directed related to the power consumption of mills‒ Coal-biomass blends have lower HGI and higher fuel feedrate
More milling power is required‒ However, AC+TB(Torrefied biomass) has similar milling power requirement due to
high HGI and lower fuel feedrate than other biomass co-firing cases
Fuel(Thermal base %)
TL(100%)
AC(100%)
A47C(100%)
AC (60%)+A47C (40%)
AC (90%)+WP (10%)
AC (90%)+EFB (10%)
AC (90%)+PKS (10%)
AC (90%)+WS
(10%)
AC (90%)+TB
(10%)
More than 75 ㎛ (g) - - - - 45.56 45.45 45.24 46.14 45.11
HGI 60 51 51 51 43.8 44.5 46.0 39.8 46.9
BWI (kJ/kg) 30.82 34.06 34.06 34.06 36.65 36.60 35.86 38.09 35.53
Fuel amount (kg/s) 86.76 56.54 58.52 57.34 58.86 59.52 58.49 58.14 56.21
Milling power requirement (MWe) 2.673 1.926 1.993 1.952 2.157 2.166 2.097 2.215 1.997
*Hardgrove grindability index**Bond work index
Minimum power consumption among biomass co-firing cases
TL AC A47C AC/A47C AC/A47C/WP AC/A47C/EFBP AC/A47C/PKS AC/A47C/WS AC/A47C/TB
Plan
t eff
icie
ncy
(%)
0.0
37.037.237.437.637.838.038.238.438.638.839.039.239.439.639.840.0
Gross plant efficiencyNet plant efficiency
Plant efficiency
Gross plant efficiency Net plant efficiency
Less efficiency for biomass co-firing case, but TB co-firing case shows the larger efficiency than the AC/AC47 case
39.93
37.92
39.91
37.90
Experimental works – 80 kWth furnace
Gas mixer
Line
coo
ler
Cycl
one
Fouling sampling zone
Burner
Gas inlet
OFA inlet
Measurement port
Bag filter
Induced draft(ID) fan
Air compressorMass flow controller(MFC)
CH4 N2H2CO
Coal + 1st oxidizer(Main fuel) 2nd oxidizer(Main oxidizer)
Overfire air(OFA)
Reburn gas
Furnacecross
section
Combustion gas
Measurement data
Cooling air out
Cooling air in
Combustion gas
Observation window
Feeding system
Measurement point(105 point)
Test condition for direct co-combustion Fuel: Trafigura (Bituminous coal) Co-fired biomass: Wood pellet, Palm kernel shell, Empty fruit bunch, Walnut
shell‒ Average particle size: 400 μm‒ Directly mixed with coal and introduced to the burner
Thermal input: 80 kW Stoichiometric ratio: 1.2
Fuel Conditions Ref. WP 10%
WP 20%
PKS 10%
PKS 20%
EFB 10%
EFB 20%
WS 10%
WS 20%
CoalHeat ratio (%) 100 90 80 90 80 90 80 90 80
Fuel rate (kg/hr) 10 9 8 9 8 9 8 9 8
BiomassHeat ratio (%) 0 10 20 10 20 10 20 10 20
Fuel rate (kg/hr) 0 1.6 3.2 1.9 3.8 1.7 3.4 1.6 3.2
Flowrate ofOxidizers
*PA (Nm3/hr) 9.2 8.4 8.2 8.4 8.2 8.4 8.1 8.4 8.1
**SA (Nm3/hr) 85.5 84.4 83.5 84.7 83.5 83.7 83.4 83.8 82.8
*PA: Primary air**SA: Secondary air
Temperature distribution In co-firing cases,
‒ Upper part of the furnace temperature was lower than reference case• Because biomass contains more moisture and less fixed carbon Low heating value
‒ Higher temperatures in the downstream due to the fact that• Particle size of the biomasses was larger than coal• Char reaction became slow, caused increase in burn-out time
0 200 400 600 800 1000 1200 1400 1600800
900
1000
1100
1200
1300
Aver
age
tem
pera
ture
(o C)
Length (mm)
Ref. WP 10% PKS 10% EFB 10% WS 10% TF 10%
0 200 400 600 800 1000 1200 1400 1600800
900
1000
1100
1200
1300
Aver
age
tem
pera
ture
(o C)
Length (mm)
Ref. WP 20% PKS 20% EFB 20% WS 20% TF 20%
Area-averaged temperature distribution along axial distance
(a) 10% co-firing (b) 20% co-firing
Gas concentration at the exit CO concentration at the exit increases by biomass co-firing
‒ Due to slow reaction of biomass char oxidation (C + ½O2 CO) NOx concentration
‒ NOx emission decreases by biomass co firing‒ Reference case: 348.5 ppm, EFB 20% case: 282 ppm Max 19.1 % reduced
• Other combustion conditions (e.g. local stoichiometric ratio) can affect the NOx emission regardless of the fuel nitrogen
Ref. WP10 WP20 EFB10 EFB20 WS10 WS20 PKS10 PKS20 TF10 TF200
50
100
150
200
250
300
350
ppm Mg/MJ
Case
NO
x ppm
(O2 6
%)
50
100
150
200
NO
x mg/
MJ
Stable combustion can be observed for 20% biomass co-firing
During co-firing experiment -1 MWth furnace
Co-firing
Reburning
Reburningfuel
멀티버너연소로3D 도면1st ,2nd stage furnace and
ash hole
Cyclone and back pass5th stage furnace and observation camera
4th stage furnace andOFA port
3rd stage furnace andReburning port
Top of the furnace andobservation window
Temperature measurement locations
Test conditions Main fuel: Adaro (Subbituminous coal) Co-firing fuel: Wood pellet, Empty fruit bunch, Torrefied biomass Thermal input: 1 MW Stoichiometric ratio: 1.2
Combustion typeCoal 100%
Co-firing Reburning
Fuel Name Ref. Co-3 Co-5 Co-10 Co-15 Co-20 Re-5 Re-10 Re-15 Re-20
CoalHeat ratio (%) 100 97 95 90 85 80 95 90 85 80
Fuel rate (kg/hr) 161 156 153 145 137 129 153 145 137 129
BM Heat ratio (%) 0 3 5 10 15 20 5 10 15 20
WP
Fuel rate (kg/hr)
0 5.6 9.4 18.8 28.2 37.6 9.4 18.8 28.2 37.6
TB 0 4.5 7.5 15.0 22.5 30.0 7.5 15.0 22.5 30.0
EFB 0 - 11.8 23.5 35.3 47.0 11.8 23.5 35.3 47.0
Burner (Coal + Biomass +Air)
OFA (Air)
Co-firing
Burner (Coal +Air)
Reburn fuel (Biomass + Air)
OFA (Air)
Reburning
Result of direct co-firing condition – 1MWth furnace NOx concentration decreases as
SR(stoichiometric ratio) decreases‒ Air staging is effective for NOx reduction
NOx reduction‒ Co-firing < Co-firing + Air staging < Reburning
Torrefied biomass shows slightly higher NOx concentration than other biomass‒ Contain less moisture compared to biomass
Ref
(0.9
8)C
o-3(
0.98
)C
o-5(
0.98
)C
o-10
(0.9
8)C
o-15
(0.9
8)C
o-20
(0.9
8)R
ef(0
.94)
Co-
3(0.
94)
Co-
5(0.
94)
Co-
10(0
.94)
Co-
15(0
.94)
Co-
20(0
.94)
Ref
(0.9
0)C
o-3(
0.90
)C
o-5(
0.90
)C
o-10
(0.9
0)C
o-15
(0.9
0)C
o-20
(0.9
0)R
e-5
Re-
10R
e-15
Re-
20
0
100
200
300
Exit NOx concentration NOx reduction ratio
NO
x pp
m(O
2 6%
)
Burner zone SR: 0.98 Burner zone SR: 0.94 Burner zone SR: 0.90 Reburning
0
10
20
30
40
50
NO
x re
duct
ion
ratio
(%)
Ref
(0.9
8)C
o-3(
0.98
)C
o-5(
0.98
)C
o-10
(0.9
8)C
o-15
(0.9
8)C
o-20
(0.9
8)R
ef(0
.94)
Co-
3(0.
94)
Co-
5(0.
94)
Co-
10(0
.94)
Co-
15(0
.94)
Co-
20(0
.94)
Ref
(0.9
0)C
o-3(
0.90
)C
o-5(
0.90
)C
o-10
(0.9
0)C
o-15
(0.9
0)C
o-20
(0.9
0)R
e-5
Re-
10R
e-15
Re-
20
0
100
200
300
Exit NOx concentration NOx reduction ratio
NO
x pp
m(O
2 6%
)
Burner zone SR: 0.98 Burner zone SR: 0.94 Burner zone SR: 0.90 Reburning
0
10
20
30
40
50
NO
x re
duct
ion
ratio
(%)
Ref
(0.9
8)
Co-
5(0.
98)
Co-
10(0
.98)
Co-
15(0
.98)
Co-
20(0
.98)
Ref
(0.9
0)
Co-
5(0.
90)
Co-
10(0
.90)
Co-
15(0
.90)
Co-
20(0
.90)
Re-
5
Re-
10
Re-
15
Re-
20
0
100
200
300
Exit NOx concentration NOx reduction ratio
NO
x pp
m(O
2 6%
)
Burner zone SR: 0.98 Burner zone SR: 0.90 Reburning
0
10
20
30
40
50
NO
x re
duct
ion
ratio
(%)
SR: Burner zone stoichiometric ratio
SR 0.98 SR 0.90 Reburning
SR 0.98 SR 0.90 ReburningSR 0.94
SR 0.98 SR 0.90 ReburningSR 0.94
EFB co-firing TB co-firing
CFD simulation results (500 MW) 1
Case Name Furnace exittemperature
Furnace heatrecovery
NOx(reduction)
Reference 1295 oC 1043 MWth 184 ppmWP-8A 1236 oC 1001 MWth 156 ppm (-15%)WP-5A 1239 oC 1010 MWth 163 ppm (-11%)WP-5B 1199 oC 1030 MWth 155 ppm (-16%)WP-5C 1249 oC 1011 MWth 119 ppm (-35%)PKS-5A 1188 oC 1016 MWth 175 ppm (-5%)
• Various biomasses, Co-firing ratios & Co-firing methods
• Co-firing method is most important for NOx reduction
(a) Pathline
[m/s] [oC]
①
②
③
④
①
②
③
④
WP-5A
WP-5C
WP-8A
WS-5A
[vol. %]
WP-5C
WP-5A WP-8A
WS-5A
(b) Temperature (c) O2 concentration (d) NOx concentration
[ppm] WP-5A WP-8A
WS-5A WP-5C
200
180
160
140
120
100
80
60
40
20
0
0.21
0.19
0.17
0.15
0.13
0.10
0.08
0.06
0.04
0.02
0
1600
1445
1290
1135
980
825
670
515
360
205
50
30
27
24
21
18
15
12
9
6
3
0
CFD simulation results (500 MW) 2
Eqv. ratioBiomass
Co-firing ratio(heatbasis, %)
Exit O2 (vol %)
NOx(ppmv)
NOxReduc.ratio(%)BNR OFA
Ref 0.995 0.125 - - 2.4 214 -1
0.90 0.22Wood pellet
3 2.9 166 22.42 5 2.9 160 25.23
0.98 0.143 2.3 171 20.0
4 5 2.4 169 21.05
0.90 0.22Torrefiedbiomass
3 2.9 165 22.96 5 2.9 158 26.27
0.98 0.143 2.9 166 22.4
8 5 2.9 160 25.2Case_ref
[Unit: °C]
Case_6
[Unit: ppm]
Case_ref Case 8
[Unit: kgmol/m3-s]
Case_ref Case 8Eva
porat
or
Divisio
n SH
Platen
SH
Platen
RH
Final
RH
Final
SH
Primary
SH
Econo
mizer
Hea
t tra
nsfe
r ra
te (
MW
th)
- E
vapo
rato
r
0
100
200
600
700
800
0
50
100
150
200
250Case_refCase_3Case_8Case_8Operation data
Heat transfer rate (M
Wth)
• Target: In-furnace NOx reduction• Main operating parameter: Equivalence ratio in the burner zone
Commercial power plant(500MWe) in Samcheonpo, Korea‒ NOx reduction characteristics for biomass co-firing and coal firing‒ Operating condition
• fuel : Coal - Bituminous coal+ subbituminous coal , Biomass - Woodpellet• Experiment Period for biomass co-firing : 57 hr• Biomass co-firing ratio : mass basis 6%, heating value basis 4.9%
‒ NOx reduction ratio by co-firing : Max 28.6%, Min 24.5% Reburning of biomass was not applied – Risks in adding new
facility(Biomass dedicated mill)
Commercial operation
Co-firing (p
pm)
Co-firing (m
g/kWh)
REF. 1(ppm)
REF. 1(m
g/kWh)
REF. 2(ppm)
REF. 2(m
g/kWh)
REF. 3(ppm)
REF. 3(m
g/kWh)
REF. 4(ppm)
REF. 4(m
g/kWh)
200
250
300
350 NOx (ppm @6% O2) NOx emission (mg/kWh)
NO
x (p
pm @
6% O
2)
600
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
NO
x em
issi
on (m
g/kW
h)25.8%
28.6%
24.5%
24.6%
31.3%
26.4%
37.4%
40.2%
Biomassco-firing
Torrefaction can be a good option for enhancing co-firing ratio
Lab-scale torrefaction experiment (1)
Lab-scale fixed-bed type Major parameters
‒ Nitrogen vs Steam‒ Temperature
Yield
230 240 250 260 270 280 290 300
40
50
60
70
80
90
Yield
of to
rrefie
d woo
dpell
et (w
t.%)
Temperature (oC)
Steam Nitrogen
85.35 %
68.34 %
49.45 %
82.81 %
63.78 %
45.86 %
0
20
40
60
80
100
Prod
uct y
ield (
wt.%
daf)
VM FC
230oC 270oC 300oC
VM/FC
<Van Krevelen diagram of various samples>
230oC270oC
300oC
Lab-scale torrefaction experiment (2) Grindability of torrefied biomass – lab-scale pulverizer
‒ When torrefied by steam, grindability was better Optimum torrefaction temperature:
‒ Dependent on the object function‒ In this study: ~270oC
230oC 270oC 300oC
Pilot-scale experiments
Wood pelletTorrefiedWood pellet
과열증기배출
Steam exhaust
Superheated steam
Superheated steam
합성가스연소기
I.D Fan
배기가스
Treatment system for exhausted steam Torrefaction system Boiler
Proximate analysis (wt.%) Elemental analysis (wt.%) HHV(MJ/kg)M VM FC Ash C H N O
WP 5.6 78.6 15.4 0.4 48.8 5.6 0.59 39.0 18.85TWP 1.7 75.5 22.4 0.4 54.5 5.8 0.3 37.3 21.53
Conclusion Pilot-scale combustion tests were conducted for three direct co-firing
methods: (1) Blending, (2) Blending + Air staging, (3) Reburning
Low N content in biomass compared to coal reduces fuel NOx formation
NOx emission decreases with increasing biomass co-firing ratio
Reburning was the most efficient among the three direct co-firing technologies
Torrefaction can be a feasible option for enhancing co-firing ratio of biomass without modification of the facility (e.g. biomass-dedicated mill)
Other issues being studied‒ Slagging/fouling‒ Corrosion‒ PM generation in biomass co-firing