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-64287 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 + 117 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 2 + 1 2 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 www.est.tu-darmstadt.de maximilian.vonbohnstein@est.tu-darmstadt.de Tel.: +49 6151 16 20365 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 Back Left Right Front