Fly ash particle formation in kraft recovery boilers

Dissertation

Pirita Mikkanen

Research output: ThesisDissertationCollection of Articles

Abstract

Fly ash particle formation in the recovery boilers has been studied experimentally in five industrial scale recovery boilers operating in Finland. The formation and growth mechanisms of the particles were studied by measuring particle characteristics including number, mass and composition size distributions in the gas phase at the recovery furnace exit, at superheater area and at boiler exit. As part of the thesis work, measurement methods were developed for recovery boiler conditions. In addition to the experimental studies, the particle formation was simulated with an Aerosol Behaviour in Combustion (ABC) model, which includes models for gas-to-particle conversion and for deposition. The results indicate that seed particle formation is involved in the fume particle formation. Particle growth occurs primarily in the furnace at temperatures greater than 800°C where the particles grow by simultaneous condensation and coagulation. Below the melting temperature of the particles, coalescence of the particles becomes slower than the particle collisions, due to increasing viscosity of the particles. Subsequently, the particles are not completely coalesced spheres but form agglomerated structures. The mean fume particle aerodynamic diameter measured at the furnace was 1.1 µm whereas it was almost 2 µm at the boiler exit. This growth is primarily due to agglomeration. The results showed two sources of coarse particles. Coarse particles formed in the furnace were efficiently depositing on the heat exchangers. The other source, which turned out to be significant as well, is the re-entrainment of particle aggregates from the heat exchangers.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Kauppinen, Esko, Supervisor, External person
  • Jokiniemi, Jorma, Supervisor, External person
Award date3 Nov 2000
Place of PublicationEspoo
Publisher
Print ISBNs951-38-5583-X
Electronic ISBNs951-38-5584-8
Publication statusPublished - 2000
MoE publication typeG5 Doctoral dissertation (article)

Fingerprint

fly ash
boiler
particle
measurement method
coalescence
agglomeration
gas
coagulation
entrainment
aerodynamics
condensation

Keywords

  • fly ash
  • particles
  • formation
  • recovery boilers
  • black liquor
  • combustion
  • aerosols
  • nucleation
  • agglomeration
  • modelling

Cite this

Mikkanen, P. (2000). Fly ash particle formation in kraft recovery boilers: Dissertation. Espoo: VTT Technical Research Centre of Finland.
Mikkanen, Pirita. / Fly ash particle formation in kraft recovery boilers : Dissertation. Espoo : VTT Technical Research Centre of Finland, 2000. 71 p.
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title = "Fly ash particle formation in kraft recovery boilers: Dissertation",
abstract = "Fly ash particle formation in the recovery boilers has been studied experimentally in five industrial scale recovery boilers operating in Finland. The formation and growth mechanisms of the particles were studied by measuring particle characteristics including number, mass and composition size distributions in the gas phase at the recovery furnace exit, at superheater area and at boiler exit. As part of the thesis work, measurement methods were developed for recovery boiler conditions. In addition to the experimental studies, the particle formation was simulated with an Aerosol Behaviour in Combustion (ABC) model, which includes models for gas-to-particle conversion and for deposition. The results indicate that seed particle formation is involved in the fume particle formation. Particle growth occurs primarily in the furnace at temperatures greater than 800°C where the particles grow by simultaneous condensation and coagulation. Below the melting temperature of the particles, coalescence of the particles becomes slower than the particle collisions, due to increasing viscosity of the particles. Subsequently, the particles are not completely coalesced spheres but form agglomerated structures. The mean fume particle aerodynamic diameter measured at the furnace was 1.1 µm whereas it was almost 2 µm at the boiler exit. This growth is primarily due to agglomeration. The results showed two sources of coarse particles. Coarse particles formed in the furnace were efficiently depositing on the heat exchangers. The other source, which turned out to be significant as well, is the re-entrainment of particle aggregates from the heat exchangers.",
keywords = "fly ash, particles, formation, recovery boilers, black liquor, combustion, aerosols, nucleation, agglomeration, modelling",
author = "Pirita Mikkanen",
year = "2000",
language = "English",
isbn = "951-38-5583-X",
series = "VTT Publications",
publisher = "VTT Technical Research Centre of Finland",
number = "421",
address = "Finland",
school = "Aalto University",

}

Mikkanen, P 2000, 'Fly ash particle formation in kraft recovery boilers: Dissertation', Doctor Degree, Aalto University, Espoo.

Fly ash particle formation in kraft recovery boilers : Dissertation. / Mikkanen, Pirita.

Espoo : VTT Technical Research Centre of Finland, 2000. 71 p.

Research output: ThesisDissertationCollection of Articles

TY - THES

T1 - Fly ash particle formation in kraft recovery boilers

T2 - Dissertation

AU - Mikkanen, Pirita

PY - 2000

Y1 - 2000

N2 - Fly ash particle formation in the recovery boilers has been studied experimentally in five industrial scale recovery boilers operating in Finland. The formation and growth mechanisms of the particles were studied by measuring particle characteristics including number, mass and composition size distributions in the gas phase at the recovery furnace exit, at superheater area and at boiler exit. As part of the thesis work, measurement methods were developed for recovery boiler conditions. In addition to the experimental studies, the particle formation was simulated with an Aerosol Behaviour in Combustion (ABC) model, which includes models for gas-to-particle conversion and for deposition. The results indicate that seed particle formation is involved in the fume particle formation. Particle growth occurs primarily in the furnace at temperatures greater than 800°C where the particles grow by simultaneous condensation and coagulation. Below the melting temperature of the particles, coalescence of the particles becomes slower than the particle collisions, due to increasing viscosity of the particles. Subsequently, the particles are not completely coalesced spheres but form agglomerated structures. The mean fume particle aerodynamic diameter measured at the furnace was 1.1 µm whereas it was almost 2 µm at the boiler exit. This growth is primarily due to agglomeration. The results showed two sources of coarse particles. Coarse particles formed in the furnace were efficiently depositing on the heat exchangers. The other source, which turned out to be significant as well, is the re-entrainment of particle aggregates from the heat exchangers.

AB - Fly ash particle formation in the recovery boilers has been studied experimentally in five industrial scale recovery boilers operating in Finland. The formation and growth mechanisms of the particles were studied by measuring particle characteristics including number, mass and composition size distributions in the gas phase at the recovery furnace exit, at superheater area and at boiler exit. As part of the thesis work, measurement methods were developed for recovery boiler conditions. In addition to the experimental studies, the particle formation was simulated with an Aerosol Behaviour in Combustion (ABC) model, which includes models for gas-to-particle conversion and for deposition. The results indicate that seed particle formation is involved in the fume particle formation. Particle growth occurs primarily in the furnace at temperatures greater than 800°C where the particles grow by simultaneous condensation and coagulation. Below the melting temperature of the particles, coalescence of the particles becomes slower than the particle collisions, due to increasing viscosity of the particles. Subsequently, the particles are not completely coalesced spheres but form agglomerated structures. The mean fume particle aerodynamic diameter measured at the furnace was 1.1 µm whereas it was almost 2 µm at the boiler exit. This growth is primarily due to agglomeration. The results showed two sources of coarse particles. Coarse particles formed in the furnace were efficiently depositing on the heat exchangers. The other source, which turned out to be significant as well, is the re-entrainment of particle aggregates from the heat exchangers.

KW - fly ash

KW - particles

KW - formation

KW - recovery boilers

KW - black liquor

KW - combustion

KW - aerosols

KW - nucleation

KW - agglomeration

KW - modelling

M3 - Dissertation

SN - 951-38-5583-X

T3 - VTT Publications

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Mikkanen P. Fly ash particle formation in kraft recovery boilers: Dissertation. Espoo: VTT Technical Research Centre of Finland, 2000. 71 p.