1. Simulation results and measurements
Prediction of corrosive atmospheres in a furnace of an industrial power plant
Maximilian von Bohnstein, Alexander Stroh, Jochen Ströhle, Bernd Epple
Institute for Energy Systems and Technology, Technische Universität Darmstadt, Otto-Bernd-Str. 2, DE Darmstadt
Model description
Power plant furnace
1. Coal combustion with ESTOS +
2. Mineral matter transformation
3. Detailed sulfur chemistry
Boiler sketch
Numerical Mesh
PC burner
Hot gas off-take
Over-fire air 1
Over-fire air 2
Outlet
Secondary burner
CFD
Prediction of corrosive atmospheres
Major reactions:
1. Coal combustion:
In-house coal combustion code “ESTOS” (R1-R5)
Mixture theory; particles treated as heavy gas component
2. Mineral matter transformation:
Reactions of pyrite and gypsum (R6-R12)
Release of SO2, H2S, S2
Oxidizing and reducing atmospheres
3. Gas phase reaction mechanism:
C-H-O-combustion system + detailed sulfur chemistry
Replaces R5
42 gas species reactions
Formation and consumption of corrosive gases H2S, COS
𝑅𝐶→ 𝐶 𝑓𝑖𝑥 +𝐶 𝐻 4 +𝐶𝑂+ 𝐻 2 𝑂+ 𝑂 2 + 𝑁 2 + 𝐻 2 𝑆+𝐻𝐶𝑙
(R1)
𝐶 𝑓𝑖𝑥 +0,5 𝑂 2 →𝐶𝑂
(R2)
𝐶 𝑓𝑖𝑥 +𝐶 𝑂 2 →2 𝐶𝑂
(R3)
𝐶𝑂+0,5 𝑂 2 → 𝐶 𝑂 2
(R4)
𝐶 𝐻 4 +1,5 𝑂 2 →𝐶𝑂+2 𝐻 2 𝑂
(R5)
𝐹𝑒 𝑆 2 𝑠 → 1 𝑥 𝐹 𝑒 𝑥 𝑆 𝑠 + 2𝑥−1 2𝑥 𝑆 2
(R6)
𝐹 𝑒 𝑥 𝑆 𝑠 + 2𝑥+3 3 𝑂 2 → 𝑥 3 𝐹 𝑒 3 𝑂 4 𝑠 +𝑆 𝑂 2
(R7)
3 𝐹𝑒 𝑆 2 𝑠 +8 𝑂 2 →𝐹 𝑒 3 𝑂 4 𝑠 +6 𝑆 𝑂 2
(R8)
𝐹 𝑒 𝑥 𝑆 𝑠 →𝑥 𝐹𝑒(𝑠)+0,5 𝑆 2
(R9)
𝐶𝑎𝑆 𝑂 4 𝑠 →𝐶𝑎𝑂 𝑠 +𝑆 𝑂 𝑂 2
(R10)
𝐶𝑎𝑆 𝑂 4 𝑠 +4 𝐶𝑂→𝐶𝑎𝑆 𝑠 +4 𝐶 𝑂 2
(R11)
𝐶𝑎𝑆 𝑠 + 𝐻 2 𝑂→𝐶𝑎𝑂 𝑠 + 𝐻 2 𝑆
(R12)
1,66 Mio. cells
2 pass boiler
250 MWel
Cross section of the first pass: 12.6 m x 15.6 m
Height: 66 m
Coal: Lausitz lignite
Coal drying in beater mills with hot flue gas
 14% residual moisture
Further classification of sulfur content in the coal: organic sulfur, pyritic sulfur and sulfates
[wt.-%]
Raw
After milling C
25.0
44.6 H
1.97
3.5 N
0.27
0.48 O
8.5
15.2 S
1.03
1.84 Cl
0.0111
0.0198
Water
51.7
14.0
Ash
11.5
20.46
Reaction model sketch:
Pyrolysis
Char combustion/gasification
SO2, S2, etc.
Mineral matter transformation
[wt.-%]
After Milling
Pyrite
0.348
Anhydrite
0.37
Burner arrangement:
6 burners, each primary + secondary burner
Two-point firing
Main burner: pulverized coal
Secondary burner: gases from coal drying
Burners are inclined to 10° and 15°
Full load operation; Coal mass flow: 78 kg/s
Air staging to reduce NOx emissions
Main combustion zone: air ratio = 0.9
Overall: air ratio = 1.2
Simulation results and measurements
Horizontal slice 9.5 m above the hopper:
Measurement 9.5 m above the hopper over several hours:
H2S and COS at the walls in the lower part of the furnace:
CO2
H2S
COS
= Measurement position
Measurement
Simulation
H2S [ppm]dry
473 – 1491
505
COS [ppm]dry
60 – 149 90
CO2 [Vol-%]dry
14,8 – 19,3 16
Contact
Measurement
Simulation
Measurement Location
O2 [Vol-%]dry
3.07
2.95
Before APH
SO2 [ppm]dry
1734
1959
Before FGD
Maximilian von Bohnstein, M. Sc.
Energy Systems & Technology
Tel.:
Conclusion:
Agreement of global O2 and SO2 concentration
Agreement of local H2S, COS and CO2 concentration
Identification of endangered wall regions
Financed by the Federal Ministry of Economic Affairs and Energy
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