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Entrained Flow Reactor Study of KCl Capture by Solid Additives
Wang, Guoliang; Jensen, Peter Arendt; Wu, Hao; Jappe Frandsen, Flemming; Bøjer, M.; Glarborg, Peter
Publication date:
2016
Document Version
Accepted author manuscript
Link to publication
Citation (APA):
Wang, G., Jensen, P. A., Wu, H., Jappe Frandsen, F., Bøjer, M., & Glarborg, P. (2016). Entrained Flow Reactor
Study of KCl Capture by Solid Additives. Poster session presented at 24th European Biomass Conference &
Exhibition, Amsterdam, Netherlands.
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Entrained Flow Reactor Study of KCl Capture by Solid Additives
Guoliang Wang1*, Peter Arendt Jensen1, Hao Wu1, Flemming Jappe Frandsen1, Martin Bøjer2, Peter Glarborg1
1Department
of Chemical and Biochemical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
2DONG Energy, Nesa Allé 1, 2820 Gentofte, Denmark
Introduction – An option for abating deposition and corrosion caused by
conditions are obviously different from that in suspension fired boilers.
alkali species during biomass combustion, is the introduction of additives
Detailed knowledge on the reaction between K-species and solid additives
under suspension-fired conditions is still limited. In this study, a water slurry
into boilers for transforming harmful gaseous alkali compounds (e.g. KCl,
KOH) into less corrosive ash species with a higher melting point. Kaolin and
containing K-salt and solid additives was introduced into an entrained flow
reactor (EFR) to study K-capture at suspension-fired conditions. A model will
coal fly ash have been proved to be very promising additives and have
received extensive studies during the past decades. However, most
be developed based on experimental data and recommendations for optimal
use of additives in full scale boilers will be provided.
previous studies were carried out in fixed-bed reactors where the reaction
Impact of temperature
Experimental setup
Slurry
Slurry pump
Slurry Nozzle
0.14
0.12
EFR, kaolin powder,K/(Al+Si) = 0.06, 50 ppm KCl
EFR, kaolin powder,K/(Al+Si) = 0.44, 500 ppm KCl
Fixed bed, kaolin pellet, 1000 ppm KCl
0.10
0.08
0.06
0.04
1000
1200
Temperature (°C)
Entrained Flow Reactor
Main air
MFC
Particle Size
Water-cooled feeding
probe
Residence Time
• Reactor length : 2 m
• Inner diameter: 79 mm
• Gas residence time : 0.8-0.9 s
Heating
elements
Heating
Controller
Vent
• Maximum temp.: 1450 °C
0.06
0.04
0.00
Pump
Feeding air
0.08
0.00
1400
1600
KCl in flue gas
800
1000
1200
Temperature (°C)
1400
1600
K-capturing level of coal ash as a function of temperature
K-capturing level of kaolin as a function of temperature
MFC
0.10
0.02
800
EFR, coal ash 0-32 µm (ASV2), 50 ppm KCl
Fixed bed, coal ash pellet, 1000 ppm KCl
0.12
0.02
Slurry feeding and atomizing system
Slurry
K-capturing level (g K/g additive)
K-capturing level (g K/ g additive)
Gas
Slurry
D3 D2
D1
Gas
0.14
Fixed Bed Reactor
D50 = 5.47 µm
pellet diameter = 1.56 mm
<1s
1h
50 ppm, 500 ppm
1000 ppm
Theoretical maximum CK is 0.30 g /g kaolin
Entrained Flow Reactor
Fixed Bed Reactor
Particle Size
< 32 µm
pellet diameter = 1.50 mm
Residence Time
<1s
1h
KCl in flue gas
50 ppm
1000 ppm
• K-capturing level of kaolin and coal ash does not change with increasing temperature (1100 - 1450 °C);
• The controlling mechanism of K-capturing at suspension-fired conditions is different from that in fixedbed reactor.
Vent
1100 °C
kaolin
1300 °C
Flow meter
Ball valve
Drier
Condenser
Vent
Cooler
Cooling water
Air cooling probe
Gas analyzer
200 °C
Quench gas
Cyclone
Aerosol
Filter
raw kaolin powder, D50 = 5.47 µm
• Difference of morphology does not affect K-capturing level.
Impact of molar ratio of K/(Al+Si) in reactants
K-capture quantification
C
B
100
Water-insoluble K
brought in by additives
D
• K-conversion fraction XK (%):
the fraction of K transformed into water-insoluble K-species.
K-conversion (%)
Water-insoluble K from
K-capturing reaction
• K-conversion decreases with increasing molar
ratio of K/(Al+Si) in reactants;
EFR, kaolin powder, D50 = 6.47 µm
Coal fly ash 0-32 µm (ASV2)
Coal fly ash 32-45 µm (ASV2)
Coal ash in full scale boiler
80
Water-soluble K
• Kaolin is more effective than coal fly ash for KClcapturing;
60
• Finer coal fly ash captures K more effectively;
• K-conversion in full scale boilers is around 100%
using coal fly ash, while in EFR it is lower
probably due to relatively shorter residence time.
40
20
• K-capturing level CK ( g K/g additive):
the mass of K captured by 1 g solid additives.
0
𝐵
𝑋𝐾 = × 100%
𝐷
𝑛𝐾𝐶𝑙 𝑀𝐾 𝑋𝐾
C𝐾 =
𝑚𝑎𝑑.
reacted kaolin, 1300 °C, 500 ppm KCl
• Melting point of reacted kaolin particles is between 1100 °C and 1300 °C;
Entrained Flow Reactor (EFR)
A
reacted kaolin , 1100 °C, 500 ppm KCl
𝑛𝐾𝐶𝑙 is the amount of KCl fed into the EFR (mol);
0.0
0.1
𝑀𝐾 is the molar mass of K (g/mol);
𝑚𝑎𝑑 is the mass of additives fed into the EFR (g).
0.2
0.3
0.4
0.5
Molar ratio of K/(Al+Si)
0.6
0.7
Entrained Flow Reactor
Full-scale Boiler
Residence time
<1s
3-5 s
Additive
Kaolin, coal fly ash
Coal fly ash
K-conversion
52% - 95%
~100 %
K-capturing level of solid additives as a function of molar ratio of
K/(Al+Si) in reactants
Conclusions
Ongoing and future work
• A method for studying additive behaviors in a entrained flow reactor has been developed;
• EFR experiments with different alkali species, like KOH, K2CO3 and K2SO4;
• KCl was effectively converted into water-insoluble K-aluminosilicate by kaolin and coal ash;
• Experiments with different coal fly ash to investigate the influence of ash properties;
• K-conversion increased when molar ratio of K/(Al+Si) in reactant decreased;
• Experiments with mullite, quartz, metakaolin to study the kinetics of K-capture;
• K-capturing level does not change obviously with increasing temperature (1100 - 1450 °C),
which is different from that in fixed-bed reactor, indicating different controlling mechanism;
• Developing a model based on experimental data for optimal utilization of solid additives
in full-scale boilers;
*[email protected]