5 th Oxyfuel Combustion Research Network Meeting. Acid Gas Control by Dry Sorbent Injection in Air and Oxy-Fuel Combustion

Transcription

1 Institut für Feuerungs- und Kraftwerkstechnik Prof. Dr. techn. G. Scheffknecht 5 th Oxyfuel Combustion Research Network Meeting Hongyi Hotel, Wuhan, China 27 th /30 th October 2015 Acid Gas Control by Dry Sorbent Injection in Air and Oxy-Fuel Combustion by Reinhold Spörl, Stefan Pek, Siqiang Qin, Jörg Maier, Günter Scheffknecht Contacts: Reinhold.Spoerl@ifk.uni-stuttgart.de Joerg.Maier@ifk.uni-stuttgart.de

2 Outline 1. Introduction 2. Motivation 3. Methodology 4. Experimental results 5. Summary and outlook 2

3 Acid gases in oxy-fuel combustion Air-fired combustion: fuel & air N 2 Combustion products: CO 2, H 2 O, SO 2, HCl, etc. 3

4 Acid gases in oxy-fuel combustion Oxy-fuel combustion: fuel & O 2 Combustion products: CO 2, H 2 O, SO 2, HCl, etc. Exclusion of airborne N 2 : Generation of CO 2 rich gas for sequestration/utilization Increase of acid gas concentrations (factor 4-5) 4

5 Acid gases in oxy-fuel recycle combustion Oxy-fuel recycle combustion: fuel & O 2 CO 2 -rich flue gas Flue gas recirculation to control: Temperatures Gas flows HEAT TRANSFER 5

6 Acid gases in oxy-fuel recycle combustion Recycle combustion: Acid gases (SO 2, HCl): No recycle: Recycle combustion does not alter gas concentrations 6

7 Acid gas removal in recycle combustion Recycle combustion: Acid gases (SO 2, HCl): No recycle: Recycle ratio: 70% Performance gain by recirculation 7

8 Acid gas removal within recycle Dry Sorbent Injection (DSI) [e.g. CaCO 3 or Ca(OH) 2 ]: reactions, e.g.: CaCO 3 + SO O 2 CaSO 4 Benefits/drawbacks: - Low costs (no scrubber required) - No excessive gas cooling - Contamination of ash 8

9 Outline 1. Introduction 2. Motivation 3. Methodology 4. Experimental results 5. Summary and outlook 9

10 Motivation Open Questions: Impact of oxy-fuel conditions on DSI performance: High impurity levels (e.g.: SO x, HCl) High CO 2 levels Changed temperature profile Flue gas recirculation Goal of this study: Identify limitations of DSI technology Demonstrate DSI applicability/performance under oxy conditions 10

11 Outline 1. Introduction 2. Motivation 3. Methodology 4. Experimental results 5. Summary and outlook 11

12 20kW Electrically Heated Combustion Test Rig Sorbent injection locations: In-furnace (~ 1100 C) Low temperature (~ 220 C) Combustion conditions: T furnace :1350 C C λ VV flue gas = 11.5 m 3 (STP)/h Gas sampling: End of furnace After filter 12

13 Combustion conditions Simulate recycle Air (reference) Simulated oxy-fuel: 28 vol% O 2 Partial recycle cleaning: 50% SO 2, 100% HCl & 20% H 2 O capture in recycle 13

14 Sorbent injection Feeder has a venturi dispersion system Injection with approx. 1.2 m 3 (STP)/h gas Loss in weight recorded Feeding Ca(OH) 2 with CO 2 is problematic: Ca OH 2 + CO 2 CaCO 3 + H 2 O Sorbent gets sticky, blocks pipes/venturi 20kW oxy tests carried out with N 2 carrier gas CaCO 3 dosing with CO 2 was successfully tested at IFK s 500 kw test rig 14

15 SO 2, SO 3 & HCl measurement techniques SO 2 : Continuous NDIR analyser ABB EL3020 SO 3 : Discontinuous wet chemical measurement (controlled condensation: triplet measurements) HCl: Continuous FTIR analyser GASMET DX4000 allows investigation of time resolved behaviour: Good agreement to wet chemical measurement method: US2.5 coal wood pellets torr. straw HCl wet chem FTIR

16 Fuel and Sorbents Fuel for DSI tests: high S and Cl US coal NCV H 2 O Ash V C fix C S H N Cl O [MJ/kg, raw] [%, raw] [%, wf] [%, waf] [%, waf] [%, waf] [%, waf] [%, waf] [%, waf] [%, waf] [%, waf] US Sorbents: Different hydrated limes (Ca(OH) 2 ): Sorbacal A, H, SP, SPS [by Lhoist] Finely milled limestone (CaCO 3 ) [by Lhoist] Na-based sorbent: Trona [milled & sieved < 32µm] Sample type Unit Fine limestone 45μm (Germany) Sorbacal A (Germany) Sorbacal H (Spain) Sorbacal SP (France) Sorbacal SPS (France) CaCO 3 [%] 98,3 4,1 3,2 4,1 6,4 CaO available [%] 0,2 69,2 70,3 72,2 70,6 Ca(OH) 2 [%] 0,3 91,4 92,9 95,4 93,3 TOTAL [CaCO 3 + Ca(OH) 2 ] [%] 98,5 95,6 96,0 99,5 99,6 Laser PSD - d90 [μm] 24,2 7,2 15,2 39,3 39,3 Specific Surface Area BET [m²/g] Total Porous Volume BJH ( Å) [cm³/g] 0,005 0,086 0,080 0,209 0,186 16

17 Normalized stoichiometric ratios & DSI performance Injection stoichiometry determines acid gas removal efficiency: (i.e.: How many moles of sorbent per mole of SO 2 /SO 3 /HCl are injected?) Ca S = m sorbent Wsorbent y SO 2 V FG Vmol ; Ca 2Cl = m sorbent Wsorbent 2 y HCl V FG Vmol ; Na Cl = m sorbent Wsorbent y HCl V FG Vmol ; Where: m sorbent = mass flow sorbent [g/h], W sorbent = mol. weight sorbent [g/mol], y SO2 = SO 2 conc. [ppm], y HHCCCC = HCl conc. [ppm], VV FFFF = flue gas flowrate [m 3 (STP)/h], VV mmmmmm = molar volume [m 3 (STP)/mol]. Percentaged acid gas removal: η ii Where: y ii 0 = conc. of component i without sorbent injection, η ii = y ii 0 y ii sorbent y ii 0 100% y ii sorbent = equilibrated conc. of component i during sorbent injection, ii= acid gas component: SO 2, SO 3, HCl. 17

18 Outline 1. Introduction 2. Motivation 3. Methodology 4. Experimental results 5. Summary and outlook 18

19 Results: Example of DSI test Air-fired, in-furnace injection of SPS Explanation: D dosing gas on; S sorbent on; I injection increased; F filter cleaning 19

20 Results: Sorbent performance air vs. oxy-fuel In-Furnace Injection (~1100 C): (Target SO 2 ) Similar air and oxy-fuel performance for all sorbents (limestone air Ca/S ratio may be biased/shifted) 20

21 Results: Sorbent performance air vs. oxy-fuel In-Furnace Injection (~1100 C): (Target SO 2, Co-benefit: HCl) HCl capture less efficient for in-furnace injection & better in air-firing (at high SO 2 : sorbent consumed by SO 2 before it can react with HCl) Requires excess sorbent to show an effect on HCl (esp.: limestone) 21

22 Results: Sorbent performance air vs. oxy-fuel Injection upstream filter: (Target: HCl) Very similar air and oxy-fuel performance Very efficient HCl removal with SP and SPS 22

23 Results: Sorbent performance air vs. oxy-fuel Injection upstream filter: (Target: HCl, Co-benefit: SO 2 ) SO 2 capture less efficient in low temperature injection (at low temp.: sorbent consumed by HCl before it can react with SO 2 ) Requires excess sorbent to show an effect 23

24 Results: Sorbent performance air vs. oxy-fuel Injection upstream filter: (Target: HCl, Co-benefit: SO 2 ) Similar air and oxy-fuel performance HCl (and SO 2 ) removal efficiency similar to Ca(OH) 2 Reaction behaviour of trona much slower than Ca(OH) 2 24

25 Results: Sorbent performance SO 3 oxy-fuel Injection into furnace & upstream filter: (Target: SO 2 or HCl) In-Furnace: At a high SO 2 reduction also SO 3 capture is good Upstream Filter: Also at low HCl reduction, good SO 3 capture 25

26 Outline 1. Introduction 2. Motivation 3. Methodology 4. Experimental results 5. Summary and outlook 26

27 Summary and outlook DSI for acid gas control is a highly promising technology for the oxyfuel recycle process: Limitation: - Feeding of Ca(OH) 2 with CO 2 is problematic - No problems observed with limestone No negative impact of oxy-fuel conditions on sorbent performance Very high SO 3 and HCl removal efficiencies (>90%) possible with low temperature injection at moderate sorbent consumption Performance will profit considerably from flue gas recirculation (oxy-fuel recycle tests that were just completed can validate this) Outlook: DSI tests at CIUDEN s 20MW oxy-fuel plant in 2016 More details on air/oxy-fuel DSI tests will be published in future 27

28 Thank you for your attention! ACKNOWLEDGMENTS The research leading to these results has received funding from the European Union s Research Fund for Coal and Steel (RFCS) research programme under grant agreement num. RFCR-CT (RFCS research project BiOxySorb: The authors gratefully acknowledge this financial contribution and the support by advices and expertise of the BiOxySorb project partners Fundación Ciudad de la Energía, E.ON Technologies (Ratcliffe) Ltd., Lhoist Recherche et Développement SA and Gestamp Biomass Solutions. The authors also thank the colleagues of IFK s department Firing Systems who contributed to this work and in particular M. Pagano and M. Faulhaber, as well as W. Ross and his team of IFK s Laboratory for Fuels, Ashes and Slag for their support in the performed experiments. 28

29 Ash analysis SiO 2 Al 2 O 3 Fe 2 O 3 CaO MgO SO 3 K 2 O Na 2 O TiO 2 P 2 O 5 [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] US coal

30 Backup: Controlled condensation method No other flue gas component condensing at C Separation of H 2 SO 4 through selective condensation Condenser: Glas coil tempered between water and acid dew point Sample train: in out H 2 SO 4 condenser Sample analysis by ion chromatography 30

31 Backup: SO 3 sampling - Ash separation At IFK in-stack dust removal is considered to be the most reliable configuration, to avoid H 2 SO 4 condensation on the filter air ingress Possible filter material for in-stack dust removal: Quarz wool: quarz fibers consisting of >99% SiO 2 31

32 Trona: Time-resolved behaviour Injection upstream filter: Time-resolved behaviour (Target = HCl) 32

33 Example of measured concentrations Air-fired, injection of SPS before filter Explanation: D dosing gas on; S sorbent on; I injection increased; F filter cleaning 33