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