to control the heat alongside the boiler to protect the more sensitive metal components against thermal, erosive and corrosive degradation

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1 Testing procedures for refractory material in bottom grid of biomass/waste-fired CFBs 1 Karol Nicia, Edgardo Coda Zabetta 2 Mikko Hupa, Leena Hupa 1 Foster Wheeler Oy, Varkaus, Finland 2 Process Chemistry Centre, Åbo Akademi University, Turku, Finland Naantali, 2009

Mikko Hupa, Leena Hupa 1 Foster Wheeler Oy, Varkaus, Finland 2

$Refractories in CFB applications main goals of ceramic refractories in furnaces: to control the heat alongside the boiler to protect the$

2 Refractories in CFB applications main goals of ceramic refractories in furnaces: to control the heat alongside the boiler to protect the more sensitive metal components against thermal, erosive and corrosive degradation cross-over duct separator combustion chamber loop-seal

more sensitive metal components against thermal, erosive and

$chutes refractory pre-casts flat air nozzles Hydro beam grate system Slopping floor Step-grid Step-grid$

3 CFB boiler design for difficult fuels waste biomass demolition wood Waste fuel in the fuel feeder bottom ash chutes refractory pre-casts flat air nozzles Hydro beam grate system Slopping floor Step-grid Step-grid design

$ash chutes refractory pre-casts flat air nozzles Hydro$

$Refractory pre-cast bricks observed to weaken in boiler operation$

4 Refractory pre-cast bricks observed to weaken in boiler operation Thermal wear Mechanical wear Chemical attack erosion corrosion chipping

5 Aim to select and define suitable laboratory analysis methods and procedures for identifying primary causes for occasional underperformance of pre-cast bricks to develop a test method for the evaluation of pre-cast bricks in laboratory conditions prior to their utilization in real combustors to conduct a first screening of seven selected pre-cast materials to compare samples from laboratory tests with samples from boilers

pre-cast bricks in laboratory conditions prior to their utilization in real combustors to conduct a first

6 Corrosion Testing Steel Corrosion Techique to study molten salt induced corrosion of alloys at high temperatures Salt compositions of interest within (Na,K) 2 (CO 3,SO 4,Cl 2 ) Analysis with SEM/EDX before heat treatment after heat treatment polished coss-section of sample in epoxy

interest within (Na,K) 2 (CO 3,SO 4,Cl 2 ) Analysis with SEM/EDX

8 Corrosion / degradation mechanism of refractory in boilers using fuels with difficult ashes? Refractories in CFB boilers typically high content of Al 2 O 3 or SiC refractory crystalline phases bonded with small amounts of silicates Selected commercial compositions: 5 with Al 2 O 3 (60 80 wt%) + silicate matrix 2 with SiC (<80 wt%) + silicate matrix Corrosion of refractory complex process: Material does not have uniform composition Material is porous, thus spalling and liquid penetration is possible

$matrix Corrosion of refractory complex process: Material does not have uniform composition Material is porous, thus spalling$

9 Experimental corrosion tests laboratory tests of 7 commercial refractories (A G) at 4 conditions 2 temperatures (500 & 700ºC) one week heat treatment 2 salts: 100 % K 2 CO 3 90/10 mol% K 2 CO 3 /KCl mixture erosion test 1 test with two refractories A and C temperature (~25ºC) test duration 8 minutes Test number Time [days] Temp [ºC] Salt K 2 CO K 2 CO /10-mol% K 2 CO 3 /KCl /10-mol% K 2 CO 3 /KCl

$erosion test 1 test with two refractories A and C temperature (~25ºC) test duration 8 minutes Test number$

10 Analyses using SEM-EDX + XRD + COM phase composition of all (7) refractories four refractories from laboratory tests ( B, C, F, G ) 2 refractory materials removed from boilers ( A & C )

$refractories from laboratory tests ( B, C, F,$

$Results and discussions SEM-EDX of exposed material Sample F (SiC refractory) after exposure to 90/10$

11 Results and discussions SEM-EDX of exposed material Sample F (SiC refractory) after exposure to 90/10 K2CO3/KCl at 700ºC, 7 d Al Potassium penetrates the matrix phase Si K Ca SiC particles O Ca-Al-silicate matrix

K2CO3/KCl at 700ºC, 7 d Al Potassium penetrates the

12 SEM-EDX line analysis of sample C (Al 2 O 3 refractory) after exposure to 90/10 K 2 CO 3 /KCl, 700ºC & 7 d K Si Potassium diffuses along the silicate phase

$Refractory C (Al 2 O 3 ) from a full-scale CFB boiler firing biomass and waste fuel K Si Ca Si$

13 Refractory C (Al 2 O 3 ) from a full-scale CFB boiler firing biomass and waste fuel K Si Ca Si increased K, Ca and S contents within silicate phase S Si accumulation of K and S at Alumina crystal boundary

14 Impact of test conditions on potassium diffusion depth in Al 2 O 3 refractory (sample C) Corrosion depth Corrosion depth m] Elemental analysis Line analysis K2CO3, 500C K2CO3, 700C K2CO3/KCl, 500C K2CO3/KCl, 700C potassium diffusion depth higher for mixtures with chloride deeper diffusion at lower temperature (Cl evaporation?)

analysis 200 100 0 K2CO3, 500C K2CO3, 700C K2CO3/KCl, 500C K2CO3/KCl, 700C potassium

15 Corrosion depth of different tested materials

$Surface topography with confocal optical microscopy, COM Refractory B (Al 2 O 3 ), K 2 CO 3 /KCl, 700 C, 7 d 1544 x 1600$

16 Surface topography with confocal optical microscopy, COM Refractory B (Al 2 O 3 ), K 2 CO 3 /KCl, 700 C, 7 d 1544 x 1600 µm depth [µm] unexposed surface B lenght [µm]

1600 µm depth [µm] 400 300 200 100 0-100 -200-300 -400

$Refractory erosion, sample C (SiC) after laboratory corrosion and sand blasting K 2 CO 3, 500 C erosion (8 min) K 2 CO 3$

17 Refractory erosion, sample C (SiC) after laboratory corrosion and sand blasting K 2 CO 3, 500 C erosion (8 min) K 2 CO 3 /KCl, 500 C erosion (8 min) K 2 CO 3, 700 C K 2 CO 3 /KCl, 700 C Salt exposure does not clearly affect abrasion resistance

K 2 CO 3 /KCl, 500 C erosion (8 min) K 2 CO 3, 700 C K 2 CO

18 CONCLUSIONS: the laboratory procedure used for alloy corrosion can be applied to study molten salt attack on refractory molten salt attack was verified by potassium diffusion depth in the sample cross-section section potassium diffusion mainly via the matrix phase salt composition and furnace temperature affected the diffusion depth samples from CFB boilers indicated increased concentrations of Ca, S and (K), thus suggesting that also other salt mixtures should be considered in further studies

via the matrix phase salt composition and furnace temperature affected the diffusion depth samples from CFB boilers

OPTICAL DETECTION OF KCl VAPOR AND ATOMIC K RELEASES FROM BIOMASS FUELS COMBUSTED IN SINGLE PARTICLE REACTOR

OPTICAL DETECTION OF KCl VAPOR AND ATOMIC K RELEASES FROM BIOMASS FUELS COMBUSTED IN SINGLE PARTICLE REACTOR Tapio Sorvajärvi*, Juha Toivonen Tampere University of Technology Department of Physics, Optics