CFD modeling of reduced lignin black liquor combustion

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Sammanfattning

Computational Fluid Dynamics (CFD) modeling is carried out to investigate how in-furnace processes are affected by lignin removal and what changes are needed in boiler operation. For a modern recovery boiler (5300 tds/day), with spraying operated in the flashing regime, two scenarios are considered. In one case, the recovery boiler is unloaded by removing lignin, but production is not increased, so the dry solids to the boiler decrease. In the second case, the total flow to the recovery boiler is increased after lignin removal so that the total flow to the recovery boiler stays the same as before lignin removal.

The simulations show that if droplet size remains the same less char carbon is delivered to the lower furnace with lignin removal, and changes to boiler operation (air and spray) are needed to compensate for this change. The needed decrease in liquor firing temperature generally increases with degree of lignin removal, and is greater in the scenario of unloading the boiler as compared to when boiler dry solids load is maintained.

The simulations suggest that up to 20% lignin removal can be implemented in an existing recovery boiler. Simulations show that with air distribution unchanged (prim22%/sec43%/tert35%), a decrease in liquor firing temperature of approximately 1.0 °C is needed. In case air distribution is changed to deliver more air to the lower furnace (prim28%/sec40%/tert32%) a decrease in liquor firing temperature of approximately 3.6 °C is needed. The simulations also show the volatile-C / char-C to be an important model input.

OriginalspråkOdefinierat/okänt
Titel på gästpublikationProceedings of the 2017 International Chemical Recovery Conference
Sidor
StatusPublicerad - 2017
MoE-publikationstypA4 Artikel i en konferenspublikation
EvenemangInternational Chemical Recovery Conference - International Chemical Recovery Conference (ICRC 2017)
Varaktighet: 1 jan 2017 → …

Konferens

KonferensInternational Chemical Recovery Conference
Period01/01/17 → …

Nyckelord

  • Black liquor
  • CFD modelling
  • Combustion
  • Lignin

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