Post on 08-Jun-2018
© 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.