Circulating Fluidised Bed Technology for Indian and other coals Dr John Topper IEA Clean Coal Centre, London

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1 Circulating Fluidised Bed Technology for Indian and other coals Dr John Topper IEA Clean Coal Centre, London STEP-TREC Programme,Trichy, December, 2013

2 Introduction Pulverised coal combustion provides over 90% of global coal capacity CFBC technology offers greater fuel flexibility and low cost emissions reduction Recent development of large, super-critical boilers make CFBC a viable alternative for utility power projects

3 Overview of PCC Coal is pulverised finely enough to ignite in a flame (>1300 C) State-of-the-art USC plants up to 47% efficient Problems with large deviation from design coal, or high ash content (slagging and fouling)

4 Overview of CFBC High pressure air suspends solid fuel in a fluid-like state Particles escaping the furnace are returned by cyclones Low temperature combustion ( C) over a longer residence time Low NOx, simple desox by limestone addition to furnace

5 Unit size, MW Growth in boiler capacity First utility CFB boiler in 1985 Similar rate of scale-up to PCC 800 MW CFB boilers commercially available PCC CFBC

6 Gross electical output, MWe Utility-scale CFBC plants Baima SC Samcheok SC 500 Lagisza SC 450 Foster Wheeler Gardanne Northside Sulcis Baima Alstom Harbin Dongfang Year commissioned

7 BHEL - CFB Boilers Experience CFBC Boilers - 26Nos (18 In Operation) Less than 30 Mwe to 70 Mwe - 6 >70 to 135 MWe MWe - 4

8 BHEL CFBC Technology Development Export order received from Koniambo 2x 135MW & PT MSW 2x 126tph coal fired boiler 250 MW (845 t/h) Neyveli Lignite based Power Plant for NLC commissioned x 275 t/h Pet Coke Fired Boilers for BORL First export order to PT IBR, Indonesia - 1x120 t/h coal fired boiler 2004 CFB Market Expanded in Utility Segment with 6 more 125MW orders secured x125 MW (405 t/h) Rajastan Lignite based Power Plant for RVUNL 175 t/h Boiler for Sinarmas Pulp & Paper Ltd firing coal & 2x125 MW (390 t/h) Gujarat Lignite based Power Plant for GIPCL

9 Performance of BHEL CFB Boilers SLPP Units 1&2 Units Commissioned in &4 Units Commisioned in 2010 One of the best performing lignite power plants SLPP Boiler Availability % 95% 90% 85% 80% 75% 70% SLPP Continous Operation in Hours 65% 60% 55% 50% Unit #1 Continuous Run Unit #2 Continuous Run Unit #1 Boiler Unit #2 Boiler Year Particulars Units 1&2 3&4 Availability Factor % PLF % Generation MU

10 Supercritical CFBC Lagisza, Poland: First SC CFB, 460 MW unit operating since 2009 Local bituminous coal Baima, China: 600 MW, largest in the world Trial operation April 2013 Local high-ash anthracite

11 Ultra-supercritical CFBC Samcheok Green Energy Centre, South Korea: 4 x 550 MW ultra-supercritical CFB boilers scheduled for start-up in 2015 Four more to follow Wide range of imported coal possible, up to 20% biomass

12 Growth in CFBC market share CFBC represents ~5 7% of global coal capacity and is projected to grow at over 12% per year. Motivating factors: Response to stricter emissions limits Exploiting cheaper fuels or using poorer quality coal available (high ash, waste coal, petcoke, lignite) Flexibility to international market

13 Efficiency Combustion efficiency: Problems with high residual carbon have been experienced for some fuels in CFBC Boiler efficiency: In-furnace desulphurisation allows lower boiler exit temperature without risk of acid corrosion Thermal efficiency: Fluidising air fans consume more power than wet FGD and pulverisers Supercritical steam has allowed a significant gain in CFBC efficiency

14 Aux. power, % Bed pressure drop, kpa Auxiliary power consumption Fan power can be reduced by optimising fluidisation state Requires control of fuel size distribution Coarse Fine Normal Novel PCC w/ FGD 2.3% points saved 2 0

15 Load following Lower ramp rates in CFBC due to thermal inertia of bed material: 2 4% MCR/min compared to 5% MCR/min in PCC Hot or warm restarts easier in CFBC but cold starts difficult Lower minimum loads without oil support achievable for low volatile matter coal Transients and low loads detrimental to desox

16 Ash-related operational issues Very high ash coal can be used in CFBC as low temperatures reduce slagging and fouling Bed agglomeration still a problem Erosion damage also a major concern Initially poor reliability for several utility CFB boilers, particularly in China Agglomeration Erosion

17 Availability CFB Boiler Initial availability, % Northside 59 (2004) (99) Gardanne 87 - Spurlock 1 (Alstom) 92 - Availability/ (reliability) 2012, % Foster Wheeler bituminous average Foster Wheeler lignite average China 300 MW average - (98.5) - (98.3) 78 87

18 SO 2 emissions: PCC options Wet FGD Spray-dryer FGD

19 Emissions: NOx CFBC produces around 60% of PCC NOx SNCR is often added to meet limits SNCR SCR SNCR CFBC + SNCR Ammonia use Operating cost Low High Moderate Capital cost SCR The 550 MW boilers at Samcheok will use SCR to meet 50 ppm limit. May be necessary for larger boilers.

20 Emissions: Nitrous oxide CFBC produces high levels of N 2 O, over 300 times the greenhouse effect of CO 2 Potential for regulation Could be abated with SNCR/SCR or afterburning

21 Ash recycle CFBC ash: High levels of lime and anhydrite Self-cementing, but can expand on hydration Not approved for use in concrete (principal PCC fly ash use) Mostly used in mine reclamation: neutralising acid soil or sealing-off acid drainage Oxide (%) CFBC bed ash PCC fly ash Silica Alumina Iron oxide Lime SO Acid mine drainage

22 Ash CFBC ash applications: Lower grade construction applications (soil stabilisation, road base, flowable fill) Waste stabilisation Agriculture Quantity of ash is higher due to limestone. PCC with wet FGD produces two saleable byproducts: coal ash and gypsum.

23 Biomass cofiring CFBC widely used for biomass firing and cofiring in Sweden and Finland Most large CFB produced by Foster Wheeler offer 10 20% cofiring capability Coarser fuel feed acceptable Less problem with slagging Agro-wastes can also cause problems for CFBC (agglomeration) Virginia City CFB Drax

24 Developments in Oxy-CFB technology A simplified flow diagram of an oxy-cfb combustion process

25 Oxyfuel combustion Possible advantages of CFBC for oxyfuel combustion: Heat transfer from circulating solids allows higher oxygen concentrations: smaller boiler Positive boiler pressure reduces air ingress Lower excess air reduces oxygen demand per kw No new burner design required CIUDEN

26 Capital costs Estimates of CFBC capital costs are beginning to approach those of PCC. CFB boiler equipment is still more expensive, but can be balanced by lack of FGD equipment, SCR, and coal pulverisers. PCC CFBC Boiler ($/kw) 506 (w/ SCR) 678 FGD ($/kw) Contingencies ($/kw) Total plant cost ($/kw) O&M ($/MWh) LCOE ($/MWh) 73 78

27 Summary CFBC has achieved competitive efficiency and costs Some fuel flexibility may be sacrificed for high efficiency and reliability Strict emissions standards could make CFBC of high sulphur coal less competitive CFBC ash markets limited High potential for biomass and oxyfuel Future growth depends on adoption of SC CFBC in China; and India?

28 THE END THANK YOU ALL FOR LISTENING Acknowledgements to Toby Lockwood and Qian Zhu of IEA Clean Coal Centre who have both produced reports on CFBC on which this presentation is based