Centre for Research and Technology Hellas Institute for Solid Fuels Technology and Applications (CERTH / ISFTA) Greek Lignite / Cardoon co-firing at PPC Kardia PP 2 nd International Workshop on Bio-CCS 25-26 th October 2011, Cardiff, Wales CERTH (GR): Emmanouil Karampinis *, Panagiotis Grammelis, Emmanuel Kakaras IFK (DE): Aaron Fuller, Eva Miller, Joerg Maier ECN (NL): Jana Kalivodova ALSTOM (DE): Markus Michel, Ioannis Tsolakidis * Tel: +30 210 6501 509, Fax : +30 210 6501 598, E-mail : karampinis@certh.gr
Introduction Support mechanisms for co-firing biomass Green Certificates or feed-in tariff systems for bioenergy; Financially supported by many EU countries (e.g. NL, UK, DK), limited or no support in others (e.g. BE, FR, DE); Biomass availability and market Imported biomass for electricity and heating sector important for meeting targets in some countries (e.g. NL, UK), while others rely on domestic biomass sources; Growing EU and international wood pellet trade; Competition with traditional end-user of wood (paper & pulp industry, etc) and domestic heating sector Growing interest for agricultural biomass; however, limited market and supply chain development Technical issues Substitution of coal with biomass up to 10-20% on energy basis typically considered easy to implement, at least for woody biomass; Growing trend to increase co-firing percentage above the typical limit or repower to 100% biomass combustion due to structure of support mechanisms; Issues related to slagging / fouling and corrosion, especially for herbaceous biomass; 2
A collaborative project with 17 partners (electricity utilities, research institutes, industrial partners). Greece: PPC & CERTH / ISFTA Budget: ~ 7 M / Duration: Jan 2008 - Dec 2011 Demonstration and assessment of advanced and innovative co-firing techniques focusing on : Fuel supply chains for different bio-fuel qualities (wood pellets, agro-biomass, RDF); The application of advanced co-firing techniques to a number of pulverised fuel power plants burning both lignite and bituminous coals; The detailed evaluation of the role of co-firing in a sustainable energy market, including both the technical and socio-economic impacts. FP7 DEBCO Project Demonstration of Large Scale Biomass CO-Firing and Supply Chain Integration / www.debco.eu
Greek Energy Sector & Co-firing Energy Sector and Lignite Greek energy sector domineered by lignite (>50% of electricity production), followed by natural gas, oil (mostly for noninterconnected islands) and hydropower; Lignite mining and power production takes place mostly in Region of Western Macedonia; operated by Public Power Corporation S.A.; Most power plants are quite old and have low efficiencies and high specific CO 2 emissions; RESe growing constantly and receive strong governmental support through feedin tariff mechanisms; Goal of 40% energy produced from RESe, mostly wind and solar; Biomass and co-firing potential Feed-in tariff: 150 200 / MWhe depending on capacity (one of the highest in EU); Co-firing eligible for support (at least in theory); Low lignite price and CO 2 cost put limits to the maximum price at plant gate for potential co-firing fuels; Wood biomass is limited or hard to collect and can claim higher prices on growing pellet heating sector; Good availability of agricultural land; many farmers are looking to switch from traditional crops (tobacco, cotton, etc) to energy crops; Co-firing biomass in lignite power plants has the added advantage of acting as support fuel in case of poor lignite quality; 4
The Kardia PP Co-firing Project The Kardia Power Plant Located in the Kozani Prefecture, West Macedonia, Greece. 4 Units, total capacity 1250 MWe; co-firing initiative implemented in Unit I (300 MWe) Produces ~13% of the electricity in Greece; Fuel: mostly lignite from the nearby Kardia mine. Low heating value, high moisture, ash and calcium content; Due to poor lignite quality is forced to utilize lignite from other sources, resulting in large variations of quality; Cardoon Cultivation Pilot program initiated by Prefecture of Kozani for energy crops cultivation in order to supply biomass for co-firing trials. Budget ~ 1 m ; 60 farmers with 400 ha total participated; Cynara Cardunculus (cardoon), a herbaceous energy crop of Mediterranean origin was selected as the biomass fuel to be cultivated and combusted due to reported high yield potential with limited input; A supply chain was organized by CERTH, PPC and local agencies taken into account limitations of power plant (e.g. no closed storage or dedicated feeding system); 5
Kardia The Joint Measurement Campaign Super heater area: Fouling/slagging probes Cooled corrosion-probe Particle sampling Gas measurements Burner area: APCD: Gas measurement Boiler modelling Emissions evaluation ESP performance Ash characteristics Ash usability Joint Measurement Campaign implemented by PPC (Greece) University of Stuttgart / IFK (Germany) ECN (Netherlands) CERTH/ISFTA (Greece) ALSTOM (Germany) First Scernario - boundary conditions (19 & 25 / 10 / 2010) Boiler load: 100% lignite Second Scernario - boundary conditions (20 22 / 10 / 2010) Boiler load: 90% lignite 10% cardoon 6
Indications before the JMC Combustion efficiency Potential increase of unburnt material in bottom ash (CFD modeling) Enhanced combustion conditions in the boiler (CO decrease at pilot units) Limited impact on fly ash burnout Depends on particle size Emissions SOx reduction due to lower sulfer content of cardoon anf calcium retention NOx reduction of up to 10% (CFD modeling, pilot scale combustion) Slagging, Fouling, Corrosion Limited risk of chlorine corrosion at 10% cardoon share (pilot scale combustion) Serious corrosion issues at higher shares Beneficial effect on fouling at 10% thermal share (pilot scale combustion) Risk of fouling (calcium sulfates, alkali chlorides) at higher shares 7
Fuel Characterization & Monitoring 8
Cardoon / lignite feeding Contemporary chipping through harvesting with forage harvesters; Cardoon quality monitored upon delivery to plant; Yard mixture: 50 tn lignite, 5 thn cardoon (~20% thermal share); Combustion after one month of open storage; Addition of further quantities of lignite straight from the mine for a final thermal share of 8.8 9.3%; Fuel mixture sampled before the mills; Difficulty to keep constant lignite quality; Harvesting Sampling Chipped cardoon Mixing with lignite
Monitoring of cardoon samples (1/2) Moisture (as received) Ash, dry basis 30.0 25.0 Moisturear, mean = 15.43 ± 3.82 %wt Ashdb, mean = 8.63 ± 1.12 %wt 20.0 weight (%) 15.0 10.0 5.0 0.0
Monitoring of cardoon samples (2/2) 22.0 LHV (as received) HHV, dry basis 20.0 HHVdb mean = 19.17 ± 0.51 MJ/kg LHVar, mean = 14.67 ± 0.87 MJ/kg 18.0 Heating Value (MJ/kg) 16.0 14.0 12.0 10.0
Fuel Analysis Parameters* Cardoon Lignite 1 (19.10.2010) Lignite 2 (25.10.2010) Lignite after mill (25.10.2010) 10% cardoon mix after mills (21.10.2010) Moisture (ar) [% wt] 11.23 53.76 50.80 4.89 7.34 Ash (d.b.) [% w.t.] 7.15 30.66 36.11 41.80 35.37 LHV (raw) [MJ/kg] 15.22 5.35 5.73 12.68 12.71 Parameters* Volatiles (daf) 74 63.89 63.11 61.96 62.47 Fixed Cardon (daf) 18.85 36.11 36.89 38.04 37.53 C (daf) 46.77 61.94 64.14 65.55 62.66 H (daf) 6.26 4.31 4.71 4.76 3.51 O diff (daf) 38.36 31.26 27.94 26.0 31.31 N (daf) 0.76 1.64 1.89 1.96 1.55 S (daf) 0.24 0.84 1.31 1.73 0.97 Cl (daf) 0.46 - - - - 12
Ash composition (%) Cardoon Lignite 1* (19.10.2010) Sample Lignite 2* (25.10.2010) 10% cardoon mix (21.10.2010) Al 2 O 3 3.33 11.87 12.85 11.71 CaO 36.39 45.41 38.92 46.29 Fe 2 O 3 1.68 6.13 7.69 5.81 K 2 O 23.65 0.62 0.83 0.61 MgO 5.45 4.50 4.45 4.60 Na 2 O 12.42 0.14 0.38 0.10 P 2 O 5 4.02 0.26 0.26 0.29 TiO 2 0.10 0.63 0.67 0.62 SiO 2 7.92 28.07 31.07 27.35 MnO 0.00 0.06 0.05 0.05 SO 3 5.04 2.31 2.83 2.58 Total 100.00 100.00 100.00 100.00 Sample Mineral Phase Cardoon Lignite Calcite (CaCO 3 ) +++ +++ Dolomite (CaMg(CO 3 ) 2 ) + Hematite (Fe 2 O 3 ) + Anhydrite (CaSO 4 ) + +++ Sylvine (KCl) +++ Arcanite (K 2 SO 4 ) +++ Quartz (SiO 2 ) ++ Lime (CaO) +++ Mullite (3Al 2 O 3 2SiO 2 ) + Hematite (Fe 2 O 3 ) + Lignite: high but varying calcium content in several mineral phases (calcite, anydrite, lime), high silica content, Al, Fe Cardoon: high calcium content (calcite), also potassium (sylvine, arcanite). High sodium content in tested sample, probably in amorphous phase 13
Ash melting temperatures Fuel Initial Deformation Temperature [ C] Softening Temperature [ C] Hemisphere Temperature [ C] Fluid Temperature [ C] Slagging Index [ C] Cardoon 693 1153 > 1550 > 1550 > 864 Lignite 1* (19.10.2010) Lignite 2* (25.10.2010) 10% cardoon mix (21.10.2010) 1325 1465 1470 1478 1354 1228 1238 1250 1280 1232 1353 1443 1458 1468 1374 Cardoon has very low IDT, high potential for slagging Changes in lignite quality are also indicated by changes in the melting temperatures 14
Fuel mixture Size: > 10 mm Size: 1-10 mm 15
Boiler measurements 16
Boiler measurements IFK Particle sampling Uncooled deposition (ceramic probe) Gas measurement Corrosion probe ECN Particle sampling Slagging / fouling probe (cooled probe) IFK Gas measurement 17
Particle sampling at 42 m, compositions Parameters Lignite combustion 10% thermal share cardoon Volatiles 2.53 2.57 Ash 97.3 97.5 Burnout (LOI; O 2 +550 C) 0.31 < 0.1 C (daf) 1.30 1.29 S (daf) 2.14 1.14 Cl (daf) 0.006 0.019 18
19 Samples ash compositions
Ash fusion behavior softening range range between ID and HT melting range range between HT and FT 1550 1500 Softening range Melting range 1450 Temperature [ C] 1400 1350 1300 1250 1200 1150 1100 Deposit lignite Deposit cardoon 10% th. Share FA lignite FA cardoon 10% th. Share 20
Conclusion of boiler measurements (1/2) Particle sampling Lignite firing particles were dominated by calcium and silicates; 10% cardoon share particles revealed chlorine, indicating influence of cardoon combustion; lower LOI indicates better combustion conditions; Deposits Significant deposit formation and fouling has been observed during both firing scenarios; Lignite deposits showed calcium sulfates and silicon to be dominant; 10% cardoon deposits showed calcium sulfates, carbon, silicon, iron, and aluminum to be dominant; Potassium detected in form of silicates; decrease of melting point of the ash Fine powdery ash formation and deposition: impaction (W-side) less deposit significant build up on (L-side) No sintering at SH level observed - deposit removal with conventional soot blowing technique High concentration of S in the ash (SO2 autocapture) - possible risk of corrosion; 21
Conclusion of boiler measurements (2/2) Corrosion Corrosion probe monitoring verified sulphur induced corrosion; Indications of chlorine induced corrosion not detected; possible beneficial impact of the sulphur content of coal which increases the S:Cl molar ratio Gas formation Addition of cardoon reduced SO 2 emissions; NO x increased contrary to expectation; likely due to more thermal NO x creation from higher temperatures; Higher CO 2 concentration during co-firing suggests improvement of combustion behaviour possibly due to the higher volatile content of cardoon; HCl concentration at 42 m is 5.81 mg / Nm 3, which is quite low compared to other measurements; 22
Emissions & ESP 23
Stack emissions, NOx 550 concentration (mg/nm 3, dry 6% O 2 ) 500 450 400 350 300 250 200 150 100 50 0 0 10 20 30 40 50 60 70 80 NOX (10% cardoon) time (h) NOX (lignite) 24
Stack emissions, CO 200 concentration (mg/nm 3, dry 6% O 2 ) 180 160 140 120 100 80 60 40 20 0 0 10 20 30 40 50 60 70 80 time (h) CO (10% cardoon) CO (lignite) 25
Stack emissions, CO 2 & O 2 14 12 concentration (vol. %) 10 8 6 4 2 0 time (h) O2 (10% cardoon) O2 (lignite) CO2 (10% cardoon) CO2 (lignite) 26
Stack emissions, dust concentration (mg/nm 3, dry 6% O 2 ) 400 380 360 340 320 300 280 260 240 220 200 180 160 140 120 100 80 60 40 20 0 0 10 20 30 40 50 60 70 80 time (h) dust(10% cardoon) dust (lignite) 27
Stack emissions- future required limits Limit (LCPD) 100% lignite 10% cardoon [mg/nm3] actual @ 6% O 2 actual @ 6% O 2 Emission Limits @ 6% O 2 [mg/nm3] [mg/nm3] NOx (01.01.2016) 200 413 427 SO 2 200 247 42 CO - 45 38 Dust 50 31 137 Increase of SO 2 emissions usually means lower Dust emissions and vice versa 28
ESP Performance 29
ESP performance Dust load before and after ESP (mg/nm 3 ) Day Dust [mg/nm 3 ] ESP ESP 1 (before) ESP 2 (after) collection efficiency 20-Oct 29,387 173 99.41 21-Oct 45,998 167 99.64 22-Oct 26,945 178 99.34 Photo of a PILAT MARK V cascade impactor 30
ESP performance Concentration, normalised [%w/w] Elemental composition of Cascade Impactor measurements at 10% cardoon co-firing before & after ESP 70 60 50 40 30 20 10 0 Si Al Ti Fe Ca Mg S Na K P Concentration, normalised [%w/w] 70 60 50 40 30 20 10 Cl 0 Si Al Ti Fe Ca Mg S Na K P Cl Course particles: CaO, silicates Fine fraction <1µm: CaO and CaSO 4 31
ESP performance high dust emissions due to high ash content of lignite relatively high dust emissions to stack ESP efficiency 99.5% coarse particulates represent the largest fraction by weight; CaO, silicates submicron fraction mainly consists of salts (Ca, K, S, Fe) calcination, sulphation potassium detected in aluminium-silicates agglomerations and also in the fine fraction (K 2 SO 4 ) fine particles (PM2.5) and aerosols are emitted after ESP negative impact on human health 32
Ash Characteristics 33
34 Fly Ash components
Bottom Ash combustible content Parameters [wt.-%] lignite BA (19.10.10) 10% cardoon BA (20.10.10) 10% cardoon BA (21.10.10) 10% cardoon BA (22.10.10) lignite BA (25.10.10) Total moisture 48.3 60.7 58.1 50.4 53.5 LOI 34.7 51.1 57.6 42.6 20.7 Total Carbon 21.0 34.4 38.9 26.2 15.4 Total inorganic Carbon Total organic Carbon 2.29 2.12 2.07 1.88 0.65 18.7 32.3 36.8 24.3 14.7 35
Overall conclusions 36
Conclusions & Future Needs Main Conclusions Lignite issues: low heating value, high moisture and ash content; Cardoon issues: chlorine content and low IDT may be an issue for dedicated cardoon combustion; Co-firing can be a beneficial option for both fuels; Generally positive results identified for 10% cardoon thermal share in modeling and pilot scale combustion tests; Variations of lignite quality has bigger impact on boiler performance and slagging / fouling that the addition of cardoon; difficulty in judging effect of cardoon addition; However no significant issues were detected during the testing; co-firing cardoon appears to be a promising option to reduce GHG emissions for lignite-fired boilers; Future Needs Increase duration of testing and optimize feeding system; Long-term monitoring of boiler performance anc especially of corrosion potential required; Testing of other types of biomass (agricultural residues, other energy crops) to avoid logistics issues and minimize environmental and supply risks; Identify the optimal biomass thermal share for maximum GHG emissions reduction; Investigate through CFD modeling and pilot testing the co-firing of Greek lignite and biomass under oxy-fuel conditions. Evaluate the potential for applicating both co-firing and CCS technology to newer lignite-fired boilers; 37
Thank you for your attention The financial grant of the European Commission through the DEBCO project (TREN/FP7EN/218968) and the support of Public Power Corporation S.A.are gratefully acknowledged. 38