Sewage sludge treatment with oxygen enrichement and oxyfuel combustion in CFBC - new pilot plant results

Transcription

1 Sewage sludge treatment with oxygen enrichement and oxyfuel combustion in CFBC - new pilot plant results 64 TH IEA FLUIDIZED BED CONVERSION MEETING Naples 3 rd of June, 2012 Authors: David Wöß, Gregor Tondl, Werner Höltl, Tobias Pröll, Hermann Hofbauer : Prof. Hermann Hofbauer

2 Outline - Introduction / Objective - The oxyfuel CFBC pilot plant - Experimental results - Conclusion / Outlook 2

3 Introduction (1) - Oxyfuel combustion technology is typically discussed for use in coal fired power plants - Especially in countries where coal plays a minor role, the application of Oxyfuel for other fuels (sewage sludge, biomass, waste fuels) is interesting in order to reduce greenhouse gas emissions from the energy sector. 3

4 Introduction (2) Oxyfuel provides concentrated CO 2 exhaust streams for carbon capture Variations in the terms of O 2 concentration in the feed allows improved operation especially for low calorific fuels Oxyfuel Combustion of alternative fuels 4

5 Phase 2 yes/no Phase 1 Basic aspects of oxy-fuel technology and technoeconomic assessment Phase 2 Oxygen-enriched industrial sewage sludge incineration Reduced CO 2 emissions because of less fossil support fuel consumption Phase 3 Demonstration CO 2 capture ready sewage sludge incineration Demonstration capture-ready sewage sludge incineration with flue gas recycing Phase 4 Present status CO 2 compression for subsequent transport and strorage 5

6 Objective of the present work to investigate oxyfuel combustion of sewage sludge in a 100kW pilot plant: - Generate first operating results on CO 2, O 2, NO x, SO x and CO concentration in exhaust gas - Use the supplementary degree of freedom, in terms of O 2 content in the feed, to allow improved operation especially for low calorific fuels 6

7 Experimental (1) - Circulating Fluidized Bed - Wet hot recycling - Cyclone separator - Exhaus gas heat exchanger - Bed material cooler - Bag filter - Exhaust gas recycle 7

8 Experimental (2) - Oxyfuel combustion of sewage sludge with high ash and water content - Start up phase in air mode - During Oxyfuel combustion, reactor temperature: 850 C - Variation on water content (9-40 %) Component Unit Dry sewage sludge C [wt %] 33 H [wt %] 5 O [wt %] 21 N [wt %] 4 S [wt %] 1 Cl [wt %] 0 Ash [wt %] 37 Sum [wt %] Variation on oxygen excess Sewage sludge composition 8

9 Experimental (3) - Circulating Fluidized Bed - Cyclone separator - Exhaus gas heat exchanger - Bed material cooler - Bag filter - Exhaust gas recycle Parameter Symbol Unit Value fuel power P fuel [kw] 100 bed material - - silica Sand bulk density ρ b [kg/m³] 1500 particle size d m [μm] 154 riser height l [m] 5 sectional area of the riser A_exit [m²] temperature riser T riser [C ] 850 9

10 Riser Cyclone separator Post combustion chamber Filter box Fuel hopper Bed material cooling Flow meters 10

11 Measured pressure profile height [m] pressure [mbar] 11

12 Measured temperature profile 12

13 Performance map sewage sludge (no cooling) Thermal fuel power (basis LHV) [kw] Change of O 2 concentration (fluidization vs. exhaust gas) [vol%] Fuel water content [wt.%] 13

14 CO versus oxygen concentration in exhaust gas 250 exhaust gas CO [vol.ppm] air Oxyfuel oxygen excess [vol.%] 14

15 Influence of oxygen purity 100 exhaust CO 2 [vol.% dry ] O %_(0.3 kwh/kg O 2 ) O %_(0.27 kwh/kg O 2 ) O 2 95%_(0.25 kwh/kg O 2 ) oxygen excess [vol.% dry ] 15

16 Exhaust gas (oxygen enriched air) exhaust gas volumeflow [Nm 3 /h] incoming oxygen [%] 16

17 Exhaust gas (oxyfuel combustion) 100 CO 2 N 2 exhaust gas volumeflow [Nm³/h] O 2 SO 2 NO Ar CO H 2 O 0 Luft air Oxy 20.5 Oxy 30 17

18 Conclusion / Outlook Oxyfuel CFBC pilot plant operates with sewage sludge pellets Very little air leakage into the system Bed material cooling system needs to be put in operation SEWAGE SLUDGE COMBUSTION IN A 16 MW TH BUBBLING FLUIDIZED BED USING OXYGEN ENRICHED AIR Stefan Penthor et al., Paper at the 21 st FBC Conference, Naples Contact: tobias.proell@tuwien.ac.at 18