© Babcock Hitachi k.K.. 2009. All rights reserved.

Advanced AQCS for Oxy-fuel Combustion System;Controlling Mercury & SO3

January 26, 2011

Special Workshop on SO2, SO3, Hg and Boiler Corrosion IssueUnder Oxyfuel Combustion Condition

BabcockBabcock--Hitachi K.K. HirofumiHitachi K.K. Hirofumi KikkawaKikkawaNoriyukiNoriyuki ImadaImada

Takayuki SaitoTakayuki Saito

Contents1. Introduction2. Mercury & SO3 Behavior in Coal-Fired Power Plant3. Pilot Plant Test Facility4. High Mercury Oxidation & Low SO2 Conversion Catalyst TRACTM

5. SO3 Behavior in AQCS6. Mercury Behavior in AQCS7. Conclusion

1

A-USC: AdvancedUltra Super Critical

- High TemperatureGas Turbine

- 700 deg-C ClassA-USC

2000

CO

2E

mis

sio

n

CO2

Capturing

Step-1

IGCC: Integrated CoalGasification CombinedCycle

Step-2

HighEfficiency

Current Thermal Power Plant

2020 2035 2050

Current Technology

High Efficiency

Direct CO2 Capturing

Hitachi’s Approach of Low CO2 Emission Technology

- Oxy-fuelCombustion

- ChemicalScrubbing

- IGCC-CO2

2

Development Subjects in OxyDevelopment Subjects in Oxy--fuel Combustionfuel Combustion

SCRSCR

AHAH

Mill

Boiler

BoilerHigh radiation intensity: CO2,H2O-same heat absorption as air combustion-reduce oxygen consumption

Liq.CO2

stackO2

Fan

DESP FGD CPU

AQCS-keep SCR,DESP,FGD performance-installation of gas cooler

Mill outlet pipe-keep gas temp. 70 – 90 dig-CRe-circulation line-reduce corrosive gas: SO3

ASU-reduce initial cost-reduce power consumption

compact & low power

ASU

CPU-reduce corrosion potential(Hg,SOx,NOx,Cl etc)-reduce power consumption

compact & low power

AQCS: Air Quality Control System

ASU: Air Separation Unit CPU: CO2 Compression and Purification Unit

GC

GC: Gas Cooler

3

Fundamental study- Laboratory test- Basic combustion test(0.4MWth test facility)

Feasibility study- Trial design of actual plant

(500MW class)- Cost evaluation

0.4MWth test facility

1) Trial design- System flow(Process analysis)

- Equipments design(Numerical analysis)

- Control system(Dynamic analysis)

2) Cost evaluation- Initial cost(Construction, Equipment)

- Running cost(Utility check)

FurnaceBurner

FurnaceBurner

Development Process for OxyOxy--fuel Combustionfuel Combustion

Verification study- Large scale combustion test(4MWth test facility)

- Total system test(1.5MWth test facility)

4MWth test facility

AQCS Furnace

1.5MWth test facility

4

Mercury & SO3 Behavior in Coal-FiredPower Plant

5

Behavior of Mercury & SOBehavior of Mercury & SO33 in Power Plantin Power Plant

Hg inCoal

Hg,SO2 Hg2+,SO3

SCR Catalyst

Hg2+

Ash Particulate(S.A., Gas Temp.)

Spray Nozzle

Absorption(HgCl2,SO2)

HCl,NH3,H2OSO2 Re-emission

SO3

Stack

A/H DESPFGD

Boiler

SCR

GasCooler

WESP

HgCl2Metal HgMetal Hg

SO3 Collision withspray droplets

Electrostaticcollection

Condensationon ash particle

gas mist

OxidationOxidation

Oxidation of SO2

Adsorptionon ash particle

Absorptioninto FGD slurry

Hard to removefrom flue gas

Easier to removefrom flue gas

6

60

10

CO2 [%]

30

10

H2O [%]

< 5

> 75

N2[%]

120

30

SO3 [ppm]

102,000Air Combustion

408,000Oxy-Combustion

Hg [g/m3N]SO2 [ppm]Condition

Hg Capture Tower

ASU

DESP

SCR

W-FGD

CPU

BoilerGas re-circulation ratio:75%

Gas Re-circulation Line

Comparison of Flue Gas CompositionsTypical Flue Gas Compositions in Conventional System (High Sulfur Coal)

ASU : Air Separation Unit CPU : CO2 Purification Unit

Increase in SO3 & Hg concentrations due to flue gas re-circulationIncrease in corrosion potential by SO3 & Hg

50 70deg-C

22 Hg + 4Hg + 4 HClHCl + O+ O22 = 2 HgCl= 2 HgCl22 + 2 H+ 2 H22OO4 NO + 4 NH4 NO + 4 NH33 + O+ O22 = 4 N= 4 N22 + 6 H+ 6 H22OO

7

Gas re-circulation

ASUESPCooler

SCRBoiler

FGDCPU

AdsorbedSO3 mist

SO3 (Gas)Ash

160 deg-C

90 deg-C(< acid dew point)

Finned tube

- Below acid dew point, gaseous SO3 changes the form into mist- Mist attached to ash and neutralized by alkali in ash is removed across ESP with ash

1.0

0S

O3

Con

cent

ratio

n[-

]

ESPOutlet

SCROutlet

FGDOutlet

ESPInlet

Location of coolerwithout Cooler(160 deg-C)

with Cooler(90 deg-C)

Mechanism of SO3 Removal across Gas Cooler

Picture of finned tubes

8

Pilot Plant Test Facility

9

Pilot Plant Test FacilityPilot Plant Test Facility

Flue gastreatment facility

DESP

Combustionfacility

Control room

FFSCR

FGD

GC

OxygenSupply Unit

10

Schematic Diagram of the Pilot Test PlantSchematic Diagram of the Pilot Test Plant

approximately 90 %approximately 90 %DeNOxDeNOx EfficiencyEfficiency

1100~1300 m3/hGas Flow Rate

110~200 kg/hCoal Feed Rate

ConditionItem

Burner

SCRreactor

Dry-

Pump

WFGD

Coal

BUFIDF

HeatExchanger

DESP : Dry Electrostatic Precipitator

A

B

D

C

E

A～E:Hg Sampling Points

GasCooler DESP

SCR : Selective Catalytic Reduction

WFGD : Wet Flue Gas Desulfurization

GRF

GasReheater

GRF: Gas Re-circulation Fan

O2

11

Structure of Gas CoolerStructure of Gas Cooler

Structure of Gas Cooler

Flue Gas

Coolingmedium

覗き窓

Nozzle Compressor Air

Soot Blower

Finned tube

Coolingmedium

12

D

2401203547μg/kgHg

8.7

15,660

11.7

27,880

7.0

25,970

%

kJ/kg

41030025330mg/kgCl

5.1

28,870Higher Calorific Value

Total Moisture

47.910.711.214.0%, dryAsh

S

N

O

H

C

Fixed Carbon

Volatile Matter

Moisture

0.772.90.260.43%, dry

0.61.580.970.8%, dry

8.08.4514.311.5%, dry

2.35.144.264.8%, dry

40.971.369.268.6%, dry

Ultimate Analysis

33.048.751.949.7%, dry

19.040.637.036.3%, dry

2.07.26.43.7%

Proximate Analysis

CBACoal Name

Properties of Test Coals

13

High Mercury Oxidation & Low SOHigh Mercury Oxidation & Low SO22

Conversion CatalystConversion Catalyst

TRACTRACTMTM

TRACTM:Triple Action Catalyst

14

SOSO22 to SOto SO33 Conversion ActivityConversion Activity

LowLow HighHigh

Hg

Oxi

datio

nA

ctiv

ityH

gO

xida

tion

Act

ivity

LowLow

HighHigh

NewNewCatalystCatalyst

Amount of ActiveAmount of ActiveComponentsComponentsIncreaseIncrease

DecreaseDecrease

ConventionalConventionalTechnologyTechnology

New Catalyst withNew Catalyst withHigher Hg Oxidation & Lower SOHigher Hg Oxidation & Lower SO22

Conversion at LowerConversion at Lower ClCl Conc. &Conc. &Higher Temp.Higher Temp.

Lower SOLower SO22 conversion is requiredconversion is requiredto improve corrosion problemto improve corrosion problem

ClCl ConcentrationConcentration

LowLowH

gO

xida

tion

Act

ivity

Hg

Oxi

datio

nA

ctiv

ityLowLow

HighHigh

TemperatureTemperatureLowLow

HighHigh

HighHigh

Properties of SCR CatalystProperties of SCR Catalyst

15

Comparison of Hg Oxidation & SOComparison of Hg Oxidation & SO22 Conversion RateConversion Rate

- Hg oxidation activity* :1.4~1.7 times higher Higher Hg removal- SO2 conversion activity : Approximately half Less SO3 formation

Hg oxidationHg oxidation SOSO22 conversionconversion

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

320 340 360 380 400 420

Temperature (Temperature (ooCC))

SO

SO

22C

onve

rsio

nA

ctiv

ityra

tio(

Con

vers

ion

Act

ivity

ratio

( --))

New CatalystNew Catalyst

ConventionalConventionalCatalystCatalyst

*Hg oxidation activity = k •Log(1(1- Hg oxidation rate(%)/100))

60

65

70

75

80

85

90

95

100

320 340 360 380 400 420

Hg

Oxi

dat

ion

Rat

e(%

) New CatalystNew Catalyst

ConventionalConventionalCatalystCatalyst

Temperature (Temperature (ooCC))

16

SOSO33 Behavior in AQCSBehavior in AQCS

17

Flue Gas Composition at SCR inlet (Coal : A & D)Flue Gas Composition at SCR inlet (Coal : A & D)

Component

Flue gas rate (m3N/h)

CO2 (%,dry)O2 (%,dry)

SO2 (ppm,dry)H2O (%)HCl (ppm,dry)

SO2 (ppm,dry)H2O (%)HCl (ppm,dry)

105013.5

3.5

1701030

10001440

Aircombustion

Oxy-fuelcombustion

85085

6.0

3503165

400040

160

High Sulfur Coal : SO2 & HCl conc. increased by a factor of 4 due to the re-circulation of flue gas (re-circulation ratio = 4).

Low Sulfur Coal : SO2 or HCl conc. did not increase so much as re-circulation ratio because part of SO2 or HCl reacted with alkali in ash.

18

Flue gas

Soot Blower

With Cooler(90 deg-C)

Without Cooler(160 deg-C)

0

10

20

30

40

0.2ppm

SO

3at

DE

SP

outle

t[pp

m]

Test condition- Coal : High surfer coal (S=2.9%)

- Moisture content in flue gas :30-40%

CoolerDESP

Finned tubes

Measurementpoint

SO3 Removal across DESP in Oxy-fuel Combustion

Re-circulationline

SO3 was reduced under 1ppm with 90 deg-C cooler system.

Carbon steel can be used for re-circulation line.

19

Cleaning of Finned Tube by S/BCleaning of Finned Tube by S/B

0.4

Time

伝熱

係数α

(kcal/℃・min・m

2)

Before S/B

After S/B

Soot Blowing

1.0

Rela

tive

overa

llheat

transfe

rcoeff

icie

nt

(-)

Woutgout

Wingin

WoutgoutWingin

TT

TT

TTTTAQ

ln

1

1Q

A

ginT

goutT

WinT

WoutT

: Amount of Heat Transfer

: Surface area of heat exchanger

: Overall heat transfer coefficient

: Gas temperature of GC inlet

: Gas temperature of GC outlet

: Heat medium temperature of GC inlet

: Heat medium temperature of GC outlet

20

Effect of Lime Injection on Ash DepositionEffect of Lime Injection on Ash Deposition

SO3：90ppm

SO3：90ppm+Lime

0.4

伝熱

係数α

2)

Lime Injection

1.0

SO3:90ppm

Soot Blowing

- S/B removed ash from finned tube even when SO3 conc. and gastemperature were 90 ppm and 90 deg-C respectively.

- Injection of lime decreased ash deposition and interval of S/B operations.

Rela

tive

overa

llheat

transfe

rcoeff

icie

nt

(-)

Time

21

Mercury Behavior in AQCSMercury Behavior in AQCS

22

Effect of DESP temperature on Hg removalEffect of DESP temperature on Hg removal

Coal A (S: 0.5%)

Coal B (S: 0.3%)

Coal C (S: 3.2%)

Coal D (S: 1.5%)

Coal A (S: 0.5%)

Coal B (S: 0.3%)

Coal C (S: 3.2%)

Coal D (S: 1.5%)

Air comb.

Oxy comb.

S : Sulfur (dry ash free)

0

20

40

60

80

100

50 100 150 200

DESP Temperature (oC)

Hg

Rem

ova

l(%

)

( ):LOI(%)

(1.6 - 2.4)

(2.4 - 2.9)

(2.5 - 2.9)

(1.7 - 1.9)

(1.4)

(0.7 - 1.2)

(4.2 - 4.5)

(2 - 2.1)

- Mercury removal across DESP increased with decrease of DESPtemperature in both oxy-fuel and air combustion system.

- Higher mercury removal across DESP was observed at lower sulfur contentin coal.

23

Effect of Sulfur Content in Coal on Hg removalEffect of Sulfur Content in Coal on Hg removal

Air, 90 oC

Air 160 oCOxy, 90 oC

Oxy,160 oC

0

20

40

60

80

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

S (%,d.a.f.)

Hg

rem

ova

l(%

)

DESP:90oC

DESP:160oC

Air Comb.

Oxy Comb.

- DESP 90oC : Little difference in mercury removal was observed between airand oxy-fuel combustion system. Mercury removal decreased little withincrease of sulfur content.

- DESP 160oC : Mercury removal decreased drastically with increase of sulfurcontent, especially in oxy-fuel combustion system.

24

Hg Behavior in Oxy-fuel Combustion (DESP=90，160C)

0

2

4

6

8

10

12

Hg

conce

ntr

ation

(μg/m

3N

)

SCRinlet

SCRoutlet

DESPinlet

DESPoutlet

FGDoutlet

η=90%η=97%

η=63%

Hg(P)

Hg++

Hg0

0

2

4

6

8

10

12

SCRinlet

SCRoutlet

DESPinlet

DESPoutlet

FGDoutlet

Hg

conce

ntr

ation

(μg/m

3N

)

η=94%

η=75%

η=77%

Hg0

Hg++

Hg(P)

DESP Temp. : 90 oC DESP Temp. : 160 oC

Mercury removal at FGD outlet (at stack) increased from 94% to 97% (outletconc. decreased to 1/3 )by decreasing DESP temperature from 160 to 90 oC.

25

SummarySummary

(1) Mercury oxidation activity of the new catalyst was 1.4~1.7 times higherthan that of the conventional catalyst and the SO2 to SO3 conversion ratewas about half of the conventional catalyst.

(2) As SO3 was reduced under 1ppm with 90 deg-C cooler system, carbonsteel can be used for re-circulation line.

(3) S/B removed ash from finned tube in GC even when SO3 conc. and gastemperature were 90 ppm and 90 deg-C respectively. Injection of lime intoflue gas decreased ash deposition and interval of S/B operations.

(4) Mercury removal across DESP increases with decreased of DESPtemperature and sulfur content in coal. Adsorption of Hg on ash particleswas inhibited under high SOx condition.

(5) Mercury removal at stack increased from 94% to 97% (outlet conc.decreased to 1/3 )by decreasing DESP temperature from 160 to 90 deg-C.

26

AcknowledgementsAcknowledgements

This study was partly carried out under

contract with New Energy and Industrial

Technology Development Organization

(NEDO) in the fiscal year 2007–2010.

27

28

SO2 Removal : Transition from Air to Oxy-fuel (Coal:C)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

SO

2C

on

c.a

tS

CR

inle

t(p

pm

)

0

50

100

150

200

250

300

SO

2co

nc.a

tF

GD

ou

tlet

(pp

m)

90

92

94

96

98

100

SO

2R

em

ova

lacro

ss

FG

D(%

)

2:38 8:38 14:38Time

FGD outlet

FGD inlet

Air comb. Oxy comb.

By shifting from air firing to oxy-fuel combustion, SO2 conc. at FGD outletdecreased rapidly due to less flue gas volume.