Institut für Verfahrenstechnik und Dampfkesselwesen Institute of Process Engineering and Power Plant Technology Prof. Dr. techn. G. Scheffknecht 3 rd Workshop IEAGHG International Oxy-Combustion Network Yokohama, Japan 5 th and 6 th March 2008 Impact of Combustion Conditions on Emission Formation (SO 2, NO X ) and fly ash Patrick Mönckert, Bhupesh Dhungel, René Kull Jörg Maier Maier@ivd.uni-stuttgart.de
Topics of Presentation, R&D Topics at IVD Fuel characterization (electrical heated pf reactors) Combustion Rank of coal (bituminous, lignite ) Emission formation, ricirculation (NO X, SO 2, H 2 S, CO Char burnout and fly ash formation Pyrolysis under CO 2 and N 2 atmosphere Volatile release and char formation/reactivity Technical scale combustion tests (0.5MW th ) Combustion and emission behavior, slagging, fouling, corrosion, SO 3,, acid dew point Component development and test (burner ) Plant handling and operation, safty requirements Model development and combustion simulation (AIOLOS)
Parameter Study on Emission Formation (SO 2, H 2 S) electrically heated reactor (20kW)
Analysis of the Coals Used Coals Klein Kopje LHV [%,ar] Moist. [%,ar] Ash [%, wf] Vol. [%, waf] Cfix [%, waf] C [%, waf] H [%, waf] N [%, waf] S [%, waf] O [by diff] Ca in ash [%] Ca/S [mol. Ratio] 24932 3.60 19.29 27.76 72.24 83.93 4.50 1.67 0.72 9.18 5.8 2.98 Lausitz 21412 10.20 5.46 57.36 42.64 66.78 5.26 0.65 0.85 (0.36) 26.5 17.0 3.17 Rhenish 20965 11.50 4.07 54.18 45.82 67.96 7.68 0.73 <0.3 23.6 26.3 3.96 Ensdorf 30955 2.42 7.47 37.21 61.90 74.85 5.05 1.59 0.83 17.7 7.55 1.03 Klein Kopje Coal Lausitz Coal Rhenish Coal Ensdorf Coal D 10 [µm] 4.83 7.46 10.83 5.79 D 50 [µm] 28.05 47.91 93.07 23.66 D 90 [µm] 72.68 142.54 264.65 92.25
Set-up and description of 20 kw once through furnace SO 2 Injection: up to 3000 ppm via the secondary stream of the burner In-flame measurements H 2 S/SO 2, staged/unstaged SO 2 measurements outlet rediative section T=1150 C SO 2 measurements outlet of convective section T= 450 C
Test Results: SO 2 emission at the outlet of the rediative section (1150 C) by SO 2 injection up to 3000ppm SO 2 captured along the convective section (1150 C down to 450 C) by SO 2 injection up to 3000ppm
Impact of SO 2 injection at the outlet of the radiative section (1150 C), OF27 SO2-injection SO2-measured 4000 3000 A. Klein Kopje Coal B. Lausitz Coal 4000 3000 SO 2 [ppm] 2000 646 SO 2 [ppm] 2000 936 1000 646 1000 936 0 0 4000 C. Rhenish Coal 4000 D. Ensdorf Coal 788 3000 320 3000 SO 2 [ppm] 2000 SO 2 [ppm] 2000 1000 1000 788 0 315 Negligible reduction of recycled SO 2 in the high temperature, radiative section of the furnace. 0
SO 2 captured along the convective part (down to 450 C) by different inlet concentrations KK_Captured RH_Captured LA_Captured EN_Captured 500 SO2 captured @ flue-gas path [ppm] 400 300 200 100 0 SO 2 injection increased 0 1000 2000 3000 4000 SO 2 measured at the end of radiative section [ppm] Oxy-fuel 27 % O 2
In-flame measurements of staged flames with focus on SO 2 and H 2 S with and without injection of 3000ppm SO 2
H 2 S formation: Impact of SO 2 accumulation (λ 1 =0.75) H2S [ppm] 1400 1200 1000 800 600 KK_0 KK_3000 LA_0 LA_3000 H2S [ppm] 1400 1200 1000 800 600 KK_0 KK_3000 LA_0 LA_3000 400 400 200 200 0 0 0.5 1 1.5 2 2.5 Distance from Burner [m] 0 0 0.5 1 1.5 2 2.5 Distance from Burner [m] OF27 Air-Blown Higher SO 2 concentrations (3000ppm) in the furnace results in at least 2 times more H 2 S formation in the sub-stoichiometric region H 2 S induced corrosion.
Impact of coal property on H 2 S formation (λ 1 =0.75, T 1 ~3 Sec) 100 SO2 and H2S Volumetric Fraction 75 50 25 OF27 H2S SO2 0 KK_0 KK_3000 EN_0 LA_0 LA_3000 Volumetric percentage of H 2 S and SO 2 in the substoichmetric furnace section, Oxyfuel 27 % O 2
Results of Parameter Study (SO 2 /H 2 S) H 2 S concentrations in the furnace can significant increased under oxyfuel conditions, Volumetric percentage of H 2 S in the furnace decreases by higher SO 2 input concentrations H 2 S formation seems to be influenced by volatile content of the coal and may other parameters: mineral composition etc. conversion of Sulphur to SO 2 close to 100% at the outlet of the rediative section for the investigated coals and atmospheres calcium rich coals show a clear tendency to capture additional Sulphur with increasing SO 2 concentration (Oxyfuel conditions), this correlates with increasing SO 3 concentrations of the fly ash
SO 3 measurements and acid dew point calculations in the flue gas duct of a 500kW facility
Oxyfuel facility (0.5 MWth) SO 3 sampling CO 2 Air Coal feeding Burner windbox Gas distribution O 2 FD/ RG fan Storage tanks Air O 2 CO 2 Stack By-passes HX SCR ESP ID fan Bottom ash SO 3 sampling position
Measured SO 3 concentrations for Lausitz coal at AIR and OXYFUEL combustion conditions SO 3 measured, ppm 140 120 SO 2 measured SO 3 measured OXYFUEL 100 80 60 40 20 0 ppm ppm AIR 733 8 (6 11)* OXYFUEL 1758 85 (36 121)* AIR 0 500 1000 1500 2000 2500 SO 2 at measurment position, ppm *... min. / max. value measured
Acid dew point T correlated with conversion rate of SO 2 SO 3 acid dew point T, C 150 140 acid dew point for AIR with 733 ppm Acid dew point T for AIR with 733 ppm SO 2 acid dew point T, C 150 140 acid dew point for OXYFUEL with 1758 ppm Acid dew point T for OXYFUEL with 1758 ppm SO 2 130 130 129 C 5.0% 120 120 4.0% 110 4.0% 5.0% 110 3.0% 2.0% 100 3.0% 2.0% 1.0% 98 C 100 1.0% 90 90 80 80 70 70 60 0 10 20 30 moisture content (of flue-gas), vol.-% 60 0 10 20 30 moisture content (of flue-gas), vol.-%
Desposits under oxyfuel conditions
Deposit-Sampling Probes (air/oxyfuel) Un-cooled ceramic temperature controlled (alloys 400-750 C) T sample = T flue gas = 750-850 C, T exposed : 10 h APH AK ESP2
SEM-BSE and SEM-MAP Ca-C Ca,C
SEM-WDS/EDS-MAP: Al, Si, O and Ca, S, Fe Al Si O Ca S Fe
SEM-MAP: Ca,S / Ca,C Ca,S Ca,C
Results of the 500kW facility- SO 3 and Deposits Clear tendencies that under Oxyfuel conditions the SO 3 concentration is increasing and also the acid dew point temperature Impact of Oxyfuel conditions on SO 2 /SO 3 conversion rate needs further clarification Further measurements of SO 3 and acid dew point temperatures are required to minimize uncertainties (measurement device, measurement procedure, operational issues of plant etc. Indications that beside sulfatization carbonization on the particle surface of deposits occurs under Oxyfuel conditions Impact of carbonization on fouling and corrosion in the convective section of the boiler needs further testing
Ongoing/Future R&D Topics at IVD Experimental Oxyfuel combustion topics: Rank of coal (bituminous, lignite ) Slagging, Fouling, (impact of higher SO 2, H 2 S, CO 2, HCl etc. Corrosion high-low temperature (Deposits, HCl, SO 2, SO 3, H 2 O Fly ash quality (EN 450 ) Component development and test (burner, ) Emissions (Hg, fine dust etc) Flue gas cleaning (SCR, Additives ) Oxy-fuel: PF/CFB, Post combustion capture: Carbonate Looping (connected CFB/FB starts operation April 2008) Lime Enhanced Gasification: Hydrogen rich Syngas
SO 2 / SO 3 sampling and analysis procedure according to VDI (draft) guideline SO 3 Condenser Sampling equipment flue gas 1 Sampling probe 2 Particle filter 3 Heating 4 SO 3 condenser and thermostat 5-6 SO 2 absorption vessels 7-9 Sampling pump