IMPACT OF OPERATING CONDITIONS ON SO 2 CAPTURE IN A SUPERCRITICAL CFB BOILER IN POLAND Artur Blaszczuk, Rafał Kobylecki, Wojciech Nowak, Marcin Klajny, Szymon Jagodzik 18 th Symposium on Fluidization and Particle Processing November 8-9, 2012, Sakai, Osaka, Japan
DEMONSTRATION PROJECT 2 FLEXI BURN CFB Collaborative Project Development of High-Efficiency CFB Technology to Provide Flexible Air/Oxy Operation for a Power Plant with CCS PROJECT CONSORTIUM RESEARCH INSTITUTES VTT Technical Research Centre of Finland CIUDEN Lappeenranta University of Technology (LUT) Czestochowa University of Technology (CzUT) Universidad de Zaragoza (UZ-LITEC) VTT (Coordynator) CIUDEN Foster Wheeler Energia Oy EDP Tauron Generation S.A., Lagisza Power Plant Praxair Siemens Energy ADEX UZ-LITEC LUT Czestochowa University of Technology Foster Wheeler Energia S.A. AICIA BUDGET : 11 190 163
DEMONSTRATION PROJECT 3
SCHEDULE A PRESENTATION 4 Introduction Development of circulating fluidized bed technology SO 2 capture inside a CFB furnace CFB facility (large scale) Operating range of the 1296 t/h CFB boiler, Characteristic solids samples (coal, limestone, ashes) Calcium balance Results Effect of Ca/S molar ratio on SO 2 capture, Utilization sorbent as a function of Ca/S molar ration, Sulfur dioxide levels versus of bed temperature, Effect of excess air ratio on SO 2 emission. Conclusions
DEVELOPMENT OF CFB TECHNOLOGY 5 Main factors determinig the development of CFB technology: standarts of gaseous emissions (LCP Directive, IPPC directive); unlimited access to various types of fuels; Fig. 1. The increase of the size of CFB boilers [1]. strong competition in the field of new advanced energy technologies (i.e. clean coal technologies). Modern CFB boilers characterized by: fuel flexibility, high efficiency (net efficiency near 45%), low emissions of pollutants. [1] Hotta A. : Foster Wheeler s solutions for large scale CFB boiler technology. Features and operational performance of Lagisza 460Mwe CFB boiler. Proc. 20th International conference on Fluidized Bed Combustion, pp. 59-70, May 18-21, X ian China, 2009
SO 2 CAPTURE MECHANISM 6 CaCO 3 CaO + CO 2 183 kj/ g mol Calcination CaO + SO 2 + 0.5 O 2 CaSO 4 + 486 kj/g mol Sulfation CaO + SO 2 + 0.5 O 2 CaSO 4 + CO 2 Direct sulfation Fig. 2. Absorption of sulfur dioxide by sorbent [2]. [2] Basu P. : Combustion and Gasification in Fluidized Beds. Taylor&Francis Group, 2006
SO 2 removal efficiency, [%] KEY PARAMETERS FOR SO 2 CAPTURE 7 An important reason to optimized bed temperature! fuel + sorbent 100 Ca/S = 3.5 Ca/S = 2.5 Ca/S = 2.0 90 80 70 60 50 750 800 850 900 Bed temperature, [ o C] Primary air to grid Fig. 4 Effect of bed temperature on desulfurization efficiency [3]. Fig. 5 Topology of CFB boiler [3]. [3] source: Metso Power
KEY PARAMETERS FOR SO 2 CAPTURE 8 Important factors for desulfurization process in CFB boilers: bed temperature, Ca/S molar ratio, sorbent particle size distribution, solids recirculation rate into CFB furnace (bed inventory & ashes), efficiency of solids separator, bed hydrodynamic conditions (i.e. height bed), excess air ratio, utilization sorbent, sorbent residence time, sorbent reactivity index, fuel parameter (i.e. sulfur content). Fig. 3 Effect of bed temperature on desulfurization efficiency for different particle size of limestone.
SUPERCRITICAL CFB BOILER (LAGISZA POWER PLANT) 9 Water/Steam Separator Table 1. Design parameters of supercritical CFB boiler at Lagisza Power Plant. SH III SH III Design parameters Unit Data SH II Capacity MW th 966 Net electrical efficiency % 44 INTREX TM -SH IV INTREX TM -RH II Boiler type - OT - SC Main steam flow kg/s 360 Main steam pressure MPa 27.5 Main steam temperature C 560 Reheat steam flow kg/s 307 Reheat steam pressure MPa 5.5 Reheat steam temperature C 580 Fig. 6 Schematic layout of utility supercritical CFB boiler arrangement of superheaters (SH) and reheater (RH). Feed water temperature C 289.7
SUPERCRITICAL CFB BOILER (LAGISZA POWER PLANT) 10 Integrated separators BENSON Vertical Tube Technology Vertical Tube Furnace Walls Low mass flux design: Low Pressure Drop Self Compensating Natural Circulation Characteristic Furnace 10.6 m * 27.6 m Height 48 m INTREX superheaters Fig. 7. Siemens technology (rifled tube).
SUPERCRITICAL CFB BOILER (LAGISZA POWER PLANT) 11 EMISSION ( at 6% O 2, dry flue gas) - (follows EU s LCP directive) SO 2 mg/m n 3 200 NO x (as NO 2 ) mg/m n 3 200 Low Emissions CO mg/m n 3 200 Dust mg/m n 3 30 Improved emissions SO 2 NO x CO 92% ~ 22 300 t/year reduction 71% ~ 4 700 t/year reduction 28% ~ 970 000 t/year reduction
Cumulative distribution, [%] EXPERIMENTAL CONDITIONS 12 Table 3. Operating range of the 1296 t/h CFB boiler during the tests. Operating parameter Unit Range of variation Superficial gas velocity, U o m s -1 2.92-5.25 Thermal velocity, U t m s -1 1.28-1.59 Minimum fluidization velocity, U mf m s -1 0.00724-0.00773 Furnace temperature, T b C 762-860 Excess air ratio, - 1.21-1.69 Ca/S molar ratio - 1.43-7.44 Table 4. Bituminous coal characteristic on performance tests. Specification Unit Range of variation Proximate analysis LHV Q ar MJ/kg 19.24-22.92 Ash A ar wt % 8.09 22.40 Moisture W ar wt % 11.81-18.47 Volatile V daf wt % 26.90-30.37 Ultimate analysis Carbon C ad wt % 52.00-57.00 Hydrogen H ad wt % 3.86-4.74 Nitrogen N ad wt % 0.73-0.97 Oxygen O ad wt % 6.30 6.90 Sulphur S ad t wt % 0.85-1.70 Superscripts: ad air dried; ar air dried; daf dry ash-free Subscripts: t total content 100 90 80 experimetal data approximation 70 60 50 40 30 20 10 0 10 100 1000 Particle diameter, [ m] Fig. 8. Particle size distribution of limestone at 1296t/h supercritical CFB boiler.
CHARACTERISTIC SOLIDS SAMPLES 13 Table 5. Analysis of limestone on test runs. Component Unit Value CaO wt.% 54.85 CaCO 3 wt.% 97.91 MgO wt.% 0.79 MgCO 3 wt.% 1.65 Al 2 O 3 wt.% 0.13 Fe 2 O 3 wt.% 0.07 Na 2 O wt.% <0.05 K 2 O wt.% <0.05 Table 6. Elemental analysis of fly ash and bottom ash. X-ray fluorescence (XRF) spectrometry Component Overall range, wt.% Bottom ash Fly ash SiO 2 37.31-70.73 35.7-47.6 Al 2 O 3 9.55-17.08 8.3-16.4 Fe 2 O 3 3.86-5.79 5.39-8.28 CaO 2.91-17.70 14.3-23.7 MgO 0.29-4.32 0.59-4.3 Na 2 O 0.29-1.16 0.53-0.89 K 2 O 1.53-2.79 1.34-1.72
CALCIUM BALANCE 14 m Ca in = Ca limestone m CaCO3 + Ca fuel m fuel m Ca in m Ca out m Ca out = Ca FA m fly ash + Ca BA m bottom ash Fig. 9. Solids mass flow at 1296t/h supercritical CFB boiler.
RESULTS 15? Utilization rate of sorbent (not available on-line), T b (available on-line)
Desulfurization efficiency, [-] Utilization rate of sorbent, [-] Ca/S molar ratio 16 1,0 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 experimental data approximation 0,60 0,55 0,50 0,45 0,40 0,35 0,30 0,25 experimental data approximation 0 1 2 3 4 5 6 7 8 Ca/S molar ratio, [-] 1,8 2,0 2,2 2,4 2,6 2,8 Ca/S molar ratio, [-] Fig. 10. Effect of Ca/S molar ratio on desulfurization efficiency in a 1296t/h supercritical CFB boiler. Fig. 11. Utilization sorbent as a function of Ca/S molar ratio in a 1296t/h supercritical CFB boiler.
SULFUR DIOXIDE EMISSION 17 SO 2 emission, [mg/m 3 n ] 200 180 160 140 120 100 80 60 40 20 high level of sulfur content in the fuel Ca/S = 2.1 100% MCR load 80% MCR load 60% MCR load 40% MCR load approximation 740 760 780 800 820 840 860 880 Bed temperature, o [ C] SO2 emission, [mg/m 3 n ] 200 180 160 140 120 100 80 60 40 20 experimental data approximation 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 Excess air ratio, [-] Fig. 12. Sulfur dioxide levels as a function of bed temperature within furnace chamber. Fig. 13. Effect of excess air ratio on SO 2 emission.
CONCLUSIONS 18 Experimental studies in a large scale CFB boiler have shown that the SO 2 capture was carried out at optimum temperature range. Ca/S molar ratio affects on SO 2 removal efficiency, but only in the range of value Ca/S<3. Above this value the efficiency of sulfur dioxide capture was at the constant level equal to 99.8% Reduction of Ca/S molar ratio (approximately 27%) affected on the increase of sorbent utilization rate by about 53%. Efficiency in the use of sorbent during all tests varied within the range 30% 42%. In the case all unit loads concentration of SO 2 in dry flue gas was lower than 200mg m n -3
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