Combustion of low-volatile coal with an advanced oxy-fuel burner concept including direct oxygen injection

Transcription

1 Institute of Combustion and Power Plant Technology Prof. Dr. techn. G. Scheffknecht Combustion of low-volatile coal with an advanced oxy-fuel burner concept including direct oxygen injection Simon Grathwohl, Jörg Maier, Günter Scheffknecht Sheffield, Sept, 2016

2 Overview 1. Introduction Motivation and research gap Test facilities, Infrastructure 2. Experimental procedure and results Firing concepts and burner-setup Experimental tests with bituminous coal advanced burner A Experimental tests with bituminous and anthracite coal advanced burner B 3. Summary, conclusions and outlook 2

3 Motivation and Research gap Combustion under recycle conditions different to air firing: Flame characterisation and ignition optimisation under recycle conditions Determination of optimum O 2 injection method Determination of impact of recycle ratio on, flame stabilisation, internal recirculation and mixing Investigation of beneficial application of pure pressurized oxygen. Design and testing of burner with pure oxygen injection Burn difficult/cheap Fuel (Anthracite) Avoid operational issues 3

4 Infrastructure and oxy-fuel test facilities at IFK 20 kw th (BTS) 500 kw th (KSVA) Fuel characterisation Investigation on emissions, burnout, fly ash Burner testing Material testing Investigation on emissions, fly ash, deposition, slagging/ fouling and corrosion ESP and SCR performance testing 4

5 Test facility 500 KW th test rig (KSVA) Inflame Measurements Gas emissions Gas temperature Heat Flux Radiation etc. Continuous gas emission measurements Sampling Ash, HCL, SO3, Hg

6 Overview 1. Introduction Motivation and research gap Test facilities, Infrastructure 2. Experimental procedure and results Firing concepts and burner-setup Experimental tests with bituminous coal advanced burner A Experimental tests with bituminous and anthracite coal advanced burner B 3. Summary, conclusions and outlook 6

7 Possible firing concepts O 2 pre-mixing O 2 pre-mixing + direct injection O 2 direct injection Staging premixed or with pure oxygen In-flame gas composition (O 2, CO, CO 2, NO, SO 2 ) In-flame gas temperature Heat flux and heat radiation measurements Continuous gas emission (O 2, CO, CO 2, NO X, SO 2 ) Fly ash sampling (ESP, APH) 7

8 Burner designs A Standard B V1 V2 V3 Coal Core 8

9 Advanced Burner A; Coal US Pittsburgh (#8) Boundary condition : Coal : US Pittsburgh (#8), O 2 Total ~22% - direct injected Un-staged Air OXY Very stable flame Burner concept is flexible enough to run bituminous coal 9

10 Advanced Burner A; Coal US Pittsburgh (#8) Oxygen concentration Air Oxy 22%, 100 %O 2 - direct Air Gas temperature Oxy 22%, 100% O 2 - direct max.: 15% max.: 20% max.: 1400 C max.: 1400 C S = 0,27 S = 0,25 S = 0,27 S = 0,25 Very fast dilution of the oxygen Temperature distribution is more homogenous in case of oxy-fuel 10

11 Summary Advanced Burner A Smooth and stable oxy-fuel operation under all tested conditions ( Iignite and bituminous ) No damages occur due the pure oxygen conditions Switching from air to oxyfuel operation in less than 10min in direct injection mode The tests showed that a safe direct injected operation is possible under oxy-fuel conditions. 11

12 Burner designs A Standard B V1 V2 V3 Coal Core 12

13 Advanced Burner B O 2 Anthracite Campaign A Tests with South African coal Premixed Mode O 2 Anthracite Campaign B Primary Secondary 1 Tests with Anthracite Premixed mode Oxygen enriched air mode Oxygen direct injected annular (up to 100%) anthracite campaign A Oxygen direct injected center (up to 15%) anthracite campaign B Secondary 2 13

14 Test conditions Advanced Burner B Test with South African coal (SAC) premixed Air SAC OXY 21 SAC OXY 30 SAC OXY 37 SAC Fuel Thermal Input kw Combustion Conditions O 2 Enrichment in Secondary Vol.-%, dry 20,9 27,6 40,6 51,1 O 2 in total Vol.-%, wet 20,9 21,3 30,2 37,1 Flue-gas volume, wet m³ (i.n.)/h ,9 245,4 203,4 Recirculation % 77,7 68,5 61 Rate Overall Stoichiometric ratio λ - 1,15 1,15 1,15 1,15 Swirl Number Sth 0,8 0,8 0,75 0,7 14

15 Results Advanced Burner B 400,0 350,0 Test with South African coal (SAC) premixed Heat flux : Ellipsoidal Radiometer Heat Flux Density q [kw/m²] 300,0 250,0 200,0 150,0 100,0 50, Measurement Level Air Oxy 21 premixed Oxy 30 premixed Oxy 37 premixed Case Elementary analysis Carbon (C), % Burnout ash sample AIR SAC- Oxy21 SAC- Oxy30 SAC- Oxy37 4,8 13,1 4,42 1,81 Sulfur (S), % 0,64 1,54 1,41 1,25 Swirl Number 0,8 0,8 0,75 0,7 Better performance in oxy-fuel >21 % O 2 Aerodynamic changes clearly visible in between Oxy30 and Oxy37 Higher Oxygen concentrations must not lead to higher heat flux in the near burner region 15

16 Results Advanced Burner B South African coal Standard Burner NOx Advanced Burner B Less fluctuations Lower NOx emissions in all test cases 16

17 Results Advanced Burner B South African coal Burner performance / comparisson Burnout ash sample Standard Burner Advanced Burner B Case AIR CIU-Oxy21 CIU-Oxy30 Case AIR CIU-Oxy21 CIU-Oxy30 CIU-Oxy37 Elementary analysis Carbon (C), % 5,49 7,55 9,42 Hydrogen (H), % n. b. < 0,3 n. b. < 0,3 n. b. < 0,3 Nitrogen (N), % n. b. < 0,3 n. b. < 0,3 n. b. < 0,3 Sulfur (S), % 0,85 1,89 1,04 Elementary analysis Carbon (C), % 4,8 13,1 4,42 1,81 Hydrogen (H), % 0,32 0,44 n. b. < 0,3 n. b. < 0,3 Nitrogen (N), % 0,24 0,23 n. b. < 0,1 n. b. < 0,1 Sulfur (S), % 0,64 1,54 1,41 1,25 Better performance in air and oxy-fuel 17

18 Antracite (El Bierzo) characterisation H o,v H u,p [J/g] [J/g] raw wf waf Ho,v = HHV and Hu,p = LHV Water Ash Volatiles Cfix C H N S O [%] [%] [%] [%] [%] [%] [%] [%] [%] raw 1,15 30,20 9,54 59,11 61,80 2,47 0,89 1,19 2,30 wf - 30,55 9,65 59,80 62,52 2,50 0,90 1,20 2,32 waf ,90 86,10 90,02 3,60 1,30 1,73 3,35 High ash content Low volatiles very good grindability > promising precondition Volumen-% El Bierzo (Antracite) D50 16 μm Particle size [μm] Volumen-% 18

19 Antracite (El Bierzo) characterisation El Bierzo characterisation (BTS 20 kw el ) Air Mass Flow Wall Temperature TL: 1,5m³/h PL: 4,0m³/h SL: 6,0 m³/h 1.6 kg/h (λ = 1,15) C % O2 [Vol.-%] CO2 [Vol.-%] Nox [ppm] CO [ppm] 2,50 2,00 1,50 1,00 0,75 0,60 0,50 0,40 0,25 Distance to Burner ppm 19

20 Test conditions Advanced Burner B Anthracite Tests with Anthracite (El Bierzo) % O2 annular direct injected Air Air 30 35% O 2 premixed Air 30 35% O 2 direct OXY 30 premixed OXY 30 50% O 2 direct OXY 40 O 2 premixed OXY % O 2 direct Fuel Thermal Input kw Combustion Conditions O 2 Enrichment in Secondary Vol.-%, dry 20,9 29, ,4 26,2 55,2 7 O 2 in total Vol.-%, wet 20,9 28,3 28,5 30,3 30,3 40,5 40,5 Flue-gas volume, wet m³ (i.n.)/h ,6 246,6 186,6 186,6 Recirculation Rate % 69,6 69, Swirl Number 0,8 0,64 0,06 0,76 0,15 0,68 0,01 20

21 Test conditions Advanced Burner B Anthracite Tests with Anthracite (El Bierzo) up to 15 % O 2 center injected Air Air 3% O 2 direct Air 9% O 2 direct Air 14% O 2 direct Oxy 37 premixed Oxy 37 10% O 2 direct Oxy 37 15% O 2 direct Fuel Thermal Input kw Combustion Conditions O2 Enrichment in Vol.-%, Secondary dry 20,9 20,9 20,9 20,9 49,4 46,8 46,1 O2 in the total Vol.-%, wet 20,9 21, ,5 36,9 37,1 37,1 Flue-gas volume, m³ wet (i.n.)/h ,1 203,7 203,7 Recirculation Rate % 62,8 62,9 62,9 Swirl Number 0,80 0,79 0,69 0,62 0,71 0,55 0,48 21

22 Ellipsoidal radiometer measurement Anthracite Air Heat Flux Density q [kw/m²] 400,0 350,0 300,0 250,0 200,0 150,0 100,0 50,0 Ellipsoidal Radiometer Measurement Level Air 21 Air 21 ~3% O2 direct center Air 23 ~9% O2 direct center Air 30 ~35% O2 premixed Air 30 ~35% O2 direct anular Big improvement by adding only 3% additional 0 2 Heat release faster in case of annular O 2 injection 22

23 Ellipsoidal radiometer Measurement Anthracite Oxy-Fuel 400,0 350,0 Ellipsoidal Radiometer Oxy 30 premixed Heat Flux Density q [kw/m²] 300,0 250,0 200,0 150,0 100,0 Oxy 37 premixed Oxy 37 ~9% O2 direct anular Oxy 37 ~14% O2 direct anular Oxy 40 premixed Oxy % O2 direct anular 50,0 Measurement Level Heat release faster in case of premixed O 2 injection 23

24 Results Advanced Burner (Anthracite) Ash analysis Anthracite (El Bierzo) Oxygen Annular Case Anth-Air 21- Anth-Air 30 premixed- Anth-Air % O 2 - direct Ant-Oxy-30 premixed Ant-Oxy 30 50% direct Ant-Oxy -40 premixed Ant-Oxy DI % O 2 direct Carbon (C), % 6,62 3,49 4,39 5,19 6,45 2,8 6,6 Sulfur (S), % 0,51 0,3 0,39 0,52 0,52 0,37 0,56 Swirl Number 0,8 0,64 0,06 0,76 0,15 0,68 0,01 Oxygen Center Case Anth-Air 21 (Copied) Anth- Air 3% O 2 direct Anth- Air 9% O 2 direct Anth- Air 14 % O 2 direct Anth-Oxy-37 premixed Anth-Oxy-37 9% O 2 direct Anth-Oxy 37 14% O 2 direct Carbon (C), % 6,62 4,42 4,31 4,19 2,09 2,7 2,8 Sulfur (S), % 0,51 0,35 0,39 0,44 0,42 0,43 0,54 Swirl Number 0,802 0,79 0,69 0,62 0,71 0,55 0,48 Performance in air improved by only adding a small amount of oxygen Aerodynamic changes clearly visible in between Oxy 40 premixed and Oxy 40 direct 24

25 Overview 1. Introduction Motivation and research gap Test facilities, Infrastructure 2. Experimental procedure and results Firing concepts and burner-setup Experimental tests with bituminous coal advanced burner A Experimental tests with bituminous and anthracite coal advanced burner B 3. Summary, conclusions and outlook 25

26 Summary Advanced Burner B Compared to the standard Burner the combustion performance of the new burner design was significantly improved. The burner was shown to perform very good even with anthracite The effect of the swirl number and momentum had a higher influence on the ignition and stability than the availability of oxygen in the reaction zone. In the current configuration, 100% direct injection was possible, but was not improving the burner performance due to reduced volumes through the swirled compartments. Partial oxygen injection in the center up to 15% in this configuration without changing the swirl was improving the performance of the burner significantly in air and oxy mode. >>It was possible to burn Anthracite with an acceptable Burner performance 26

27 Conclusion One should keep in mind the total swirl influence when changing in between different operation conditions The tests showed that under oxy-fuel conditions non premixed applications by injecting the oxygen directly into the combustion chamber is possible and possibly the best way for oxy-fuel combustion. Oxy-fuel and direct injection of O 2 offers further possibilities in the utilization of challenging fuels e.g. Anthracite, biomass, waste 27

28 28

29 Thank you! Simon Grathwohl phone +49 (0) fax +49 (0) University of Stuttgart Institute of Combustion and Power Plant Technology Pfaffenwaldring Stuttgart Germany ACKNOWLEDGMENTS The authors gratefully acknowledge the financial support by the European Commission s Seventh Framework Programme (FP7/ ) under grant agreement n that founded part of this work. 29

30 Back-up Back-up 30

31 Pittsburgh #8 H 2 O Volatiles Ash fixed C C H N S O 2 H u [MJ/kg]* [%]an; ([%]waf) (85.84) 4.44 (5.22) 1.45 (1.66) 0.97 (1.14) 5.23 (6.15) * 31

32 South African Coal H o,v [J/g] H u,p [J/g] South African (CIUDEN) D50 27 μm an raw wf waf Ho,v = HHV and Hu,p = LHV Water [%] Ash [%] Volatiles [%] Cfix [%] C [%] Htot [%] H [%] N [%] S [%] O [%] an 2,63 15,25 26,25 55,87 68,50 3,95 3,66 1,48 0,51 7,97 raw 2,63 15,25 26,25 55,88 68,50 3,95 3,66 1,49 0,51 7,98 wf - 15,66 26,96 57,38 70,35 3,75 3,75 1,53 0,52 8,19 waf ,96 68,04 83,41 4,45 4,45 1,81 0,62 9,71 32

33 Results Advanced Burner B Burner performance / comparisson Standard Burner CO Advanced Burner B 33