NOx processing experiences for removal in the CO2 plant for the Oxyfuel combustion processRoland Ritter, Torsten Stoffregen, Linde Engineering Dresden GmbHNicole Schödel, Florian Winkler, Linde Engineering HQ Pullach3. OCC, Ponferrada, 12th September 2013
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 20132
Overview of the Oxyfuel-pilot plant at Schwarze Pumpe
Boiler
Dust filter
FGD
ASU
CO2 plantFGC Control room
operator:Vattenfall Europe
location:Schwarze Pumpe
capacity: 30 MWth
fuel:5,2 t/h (lignite)
O2 consumption:10 t/h (99,5%)
CO2 (liquid): 9 t/h
capex:approx. 70 Mio. €
Start-up: Sept 2008
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 20133
Oxyfuel technologyCO2 purification and liquefaction plant (pilot plant)
Processpre-compression, drying, liquefaction, rectification with CO2 recycling and liquid storage
Capacity7 000 Nm³/h flue gas
max. 240 t/d CO2 liquid
Purity> 99.7 vol % CO2
Scope of workTurnkey plant
Start-up2008
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 20134
The challenge of SOx and NOx removal at oxyfuel fired power plants
typical content of SO2 in air fired mode after boiler: 1500… 5000 mg/Nm³
content of SO2 in flue gas in oxyfuel fired mode after boiler
(w/o FGD in recycle flow ): 8000… 35000 mg/ Nm³
typical content of NOx in flue gas in oxyfuel fired mode after boiler:
(w/o DeNOx unit in recycle flow): 500… 1400 mg/ Nm³
ca. 1.5 times increase of
NOx-concentration at boiler
recycled NOx will be reduced
3 to 5 times increase of
SO2-concentration
acid dew point change, serious corrosion
at boiler
source:„CO2 Quality and other relevant Issues“
A. Kather; 2nd Working Group Meeting; 7th September 2009; Cottbus
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 20135
New process development NOx and SOx removal - background
The flue gas of oxyfuel power plants with CSS has to be purified before transportation and storage.
There are several common technologies for flue gas purification for:
— DeNOx (Selective Catalytic Reduction-unit)
— DeSOx (FGD – lime stone suspension)
— Simultaneous removal
There is a high operation pressure available in the CO2-stream.
new process ideas
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 20136
Development of the Linde-concept (laboratory)
researched technologies in LINDE-laboratory:1) catalytic reduction technology with reduction media hydrogen and ammonia2) alkali based wash unit with ammonia, sodium hydroxide and ammonia derivate (urea)3) reduction/ regeneration of spent salt solution
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 20137
Principle units for Oxyfuel technology
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 20138
Development of the Linde-concept for Oxyfuel technology
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 20139
LINDE-concept alkaline wash unit LICONOX™ (“Linde cold DeNOx”)
NO and SO2 Oxidation:
NO+½ O2 NO2
SO2 + NO2 SO3 + NO
Alkali based wash unit:
SO2+ 2 NH3 + H2O (NH4)2 SO3
SO3+ 2 NH3 + H2O (NH4)2 SO4
NO + NO2 + 2 NH3 + H2O 2NH4NO2
2 NO2 + 2NH3 + H2O NH4NO2 + NH4NO3
2 NO +O2 + 2 NaOH NaNO2 + NaNO3 +H2O
2 NO2 + 2 NaOH NaNO2 + NaNO3 +H2O
Regeneration/ reduction: NH4NO2 N2 + 2 H20 (Nitrite-decomposition > 60°C)
Ammonia water …
— reaction of NO and NO2
— reaction of SO2 and SO3
results are nitrite and nitrate …
— reaction to a mix of nitrogen and sulfur fertilizer
— reduction to N2 and H2O possible (De-nitrification)
• pre-purified, compressed gas
• moderate temperature
• small gas stream (low volume flow rate)
• smaller equipment
• high conversation rate
• no acid mixture (corrosion problem)
advantages:
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 201310
Cost comparison of different NOx-removal units
key results of alkaline wash unit tested in laboratory in Linde:
• better opportunity to remove NOx than standard solution
• NOx-conversion of 97 % approved
• simultaneous removal of SOx and NOx
• NOx-removal directed to selective synthesis of Ammonium-nitrite
• option of Nitrite reduction and/ or conversion into fertilizers (nitrate)
Cost estimate Standard SCR solution Fast SCR at elevated pressure with H2 or NH3
Alkaline wash unit at elevated pressure
Conversion rate in % 90 90 85-95
Capital in % 100 140-170 65-70
Operating cost in % 100 80-140 20
Total capex and opex in % 100 120-140 40-50
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 201311
Alkaline wash unit with real flue gas from oxy-boiler – installation in the CO2-pilot plant Schwarze Pumpe
Atm
.capacity:
200… 700 Nm³/h
30… 40 (80) °C
5… 20 bar
NO/ NO2-
concentration
adjustable
with additional
dosing (cylinder)
using of
15 wt%
ammonia water or 33 wt%
sodium hydroxide
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 201312
Installation of test facility at oxyfuel pilot plant
process flow diagram of alkaline wash process
installation of column skid
first test campaign:
27.07. – 07.09.2010 using ammonia water
second test campaign:
26.04. – 27.05.2011 using sodium hydroxide
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 201313
Measuring values / performance
NOx conversation versus operation pressure p1<< p2 and residence time
pressure p1pressure p2
• Converstion rate of NO/ NO2 depending of pressure, temperature, ph-value • Kinetic Model based determination of NO/NO2 profileTarget for future plants:• Selection of DeNOx position (depended from pressure)• Performance simulation based on kinetics for demonstration/ commercial power plant • Column height and diameter determination for NOx removal• Calculation of utility consumption (NH3, NaOH) and also spent salt solution flow rate
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 201314
LICONOX™ - results of pilot plant laboratory results confirmed
Simulat ion and Comparison with measured Data10bar; 24°C; 6,5vol% O2; pH6,5
0
20
40
60
80
100
120
140
160
180
0 5 10 15 20 25 30
time sec.
NOx
[vpp
m]
0,5
0,6
0,7
0,8
0,9
1
nitr
ite se
lect
ivity
[mol
/mol
]
nit rogen monoxide
nitrogen dioxide
nitrite select ivity
50%55%60%65%70%75%80%85%90%95%
100%
0 5 10 15 20pressure in bar
NOx c
onve
rsio
n pi
lot p
lant
Extended kinetic Model• Consideration of NO2 yield and influence
onto NO conversion• Determination of kinetic rate constants• Nitrite selectivity forecast
NOx conversation rate versus pressure
nitrite selectivity versus NO-NO2 rate on column entry
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 201315
Development of the kinetic model
NO-conversation versus pH-value
4 NO + 3 02 + 2 H2O → 4 HNO3
4 NO + O2 + 2 H2O + 4 NH3 → 4 NH4NO2
determination of kinetic rate constants
[NO2]/([NO]x[O2]) in dm³/mol
0%
25%
50%
75%
100%
0% 25% 50% 75% 100%NOx conversion simulated
NOx c
onve
rsio
n pi
lot p
lant
Kinetic model confirmed Good correlation between measured data and kinetic model
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 201316
Reduction of spent salt solution(test phase in Schwarze Pumpe)
possible reduction of spent salt solution:
• NO-NO2 removal with 15wt%- ammonia water 100% (Basis)
• NO-NO2 removal with 33wt%- sodium hydroxide ca. 46%
• NO-NO2 removal with ammonia water and reduction ca. 23%
0
100
200
300
400
500
600
700
800
0 50 100 150 200
Temperture °C
HNO 2
mm
ol/l
pH 7.2pH 7.6pH 7.8
Nitrite-content after reduction versus temperature
Regeneration/ reduction: NH4NO2 N2 + 2 H20 (Nitrite-decomposition)
Cooling Water
Make up Water
spent saltsolution(nitrates)
Ammonia Water
compressedCO2-Gas
purifiedCO2-Gas
nitrite reduction
Linde Engineering Dresden GmbH 3. Oxyfuel Combustion Conference Ponferrada / 12. September 201317
Advantages of the LICONOX™ - processConclusion
• reduced gas flow in the CO2 plant (three times lower, SCR is arranged after the boiler, were the gas contains the recycle gas)
• the process conditions are “mild” and “moderate”
• raw gas is pre-purified and compressed; smaller equipment are required
• an alkaline solvent has a significantly better capability for removal of NOx compared to water and no complete oxidation of NO is needed
• simultaneous SOx and NOx removal is possible; SO2 adsorption is independent of the NO kinetics and can directly be removed along with SO3 (an oxidation of SO2 to SO3 is not required)
• high conversation rate
• no acid mixture (corrosion problem)
• there is a potential for regeneration of the washing media or the oxidized washing media can be used e.g. as a fertilizer
The pilot phase is complete, the Scale-up is on going and the LICONOX is ready for commercialisation.
The new process has a couple of advantages compared to normal existing hot SCR technology (state of the art) and the washing process with water:
Thank you for your attention
Roland RitterLinde Engineering Dresden GmbHphone +49-351-250 [email protected]