Impact of Combustion Conditions on Emission Formation (SO 2, NO X ) and fly ash

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1 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

2 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)

3 Parameter Study on Emission Formation (SO 2, H 2 S) electrically heated reactor (20kW)

4 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] Lausitz (0.36) Rhenish < Ensdorf Klein Kopje Coal Lausitz Coal Rhenish Coal Ensdorf Coal D 10 [µm] D 50 [µm] D 90 [µm]

5 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

6 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

7 Impact of SO 2 injection at the outlet of the radiative section (1150 C), OF27 SO2-injection SO2-measured A. Klein Kopje Coal B. Lausitz Coal SO 2 [ppm] SO 2 [ppm] C. Rhenish Coal 4000 D. Ensdorf Coal SO 2 [ppm] 2000 SO 2 [ppm] Negligible reduction of recycled SO 2 in the high temperature, radiative section of the furnace. 0

8 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 flue-gas path [ppm] SO 2 injection increased SO 2 measured at the end of radiative section [ppm] Oxy-fuel 27 % O 2

9 In-flame measurements of staged flames with focus on SO 2 and H 2 S with and without injection of 3000ppm SO 2

10 H 2 S formation: Impact of SO 2 accumulation (λ 1 =0.75) H2S [ppm] KK_0 KK_3000 LA_0 LA_3000 H2S [ppm] KK_0 KK_3000 LA_0 LA_ Distance from Burner [m] 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.

11 Impact of coal property on H 2 S formation (λ 1 =0.75, T 1 ~3 Sec) 100 SO2 and H2S Volumetric Fraction 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

12 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

13 SO 3 measurements and acid dew point calculations in the flue gas duct of a 500kW facility

14 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

15 Measured SO 3 concentrations for Lausitz coal at AIR and OXYFUEL combustion conditions SO 3 measured, ppm SO 2 measured SO 3 measured OXYFUEL ppm ppm AIR (6 11)* OXYFUEL (36 121)* AIR SO 2 at measurment position, ppm *... min. / max. value measured

16 Acid dew point T correlated with conversion rate of SO 2 SO 3 acid dew point T, C acid dew point for AIR with 733 ppm Acid dew point T for AIR with 733 ppm SO 2 acid dew point T, C acid dew point for OXYFUEL with 1758 ppm Acid dew point T for OXYFUEL with 1758 ppm SO C 5.0% % % 5.0% % 2.0% % 2.0% 1.0% 98 C % moisture content (of flue-gas), vol.-% moisture content (of flue-gas), vol.-%

17 Desposits under oxyfuel conditions

18 Deposit-Sampling Probes (air/oxyfuel) Un-cooled ceramic temperature controlled (alloys C) T sample = T flue gas = C, T exposed : 10 h APH AK ESP2

19 SEM-BSE and SEM-MAP Ca-C Ca,C

20 SEM-WDS/EDS-MAP: Al, Si, O and Ca, S, Fe Al Si O Ca S Fe

21 SEM-MAP: Ca,S / Ca,C Ca,S Ca,C

22 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

23 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

24 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