The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.

Spray Formation of High Dry Solids Black Liquor in Recovery Boiler Furnaces

Pasi Miikkulainen

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Mechanical Engineering for public examination and debate in Auditorium K216 at Helsinki University of Technology (Espoo, Finland) on the 14th of December, 2006, at 12 noon.

Overview in PDF format (ISBN 951-22-8508-8)   [1038 KB]
Dissertation is also available in print (ISBN 951-22-8507-X)


This thesis focuses on the characteristics of high dry solids black liquor sprays under in-furnace conditions, more specifically, on how the atomization process starts and the nature of the initial properties such as velocity, opening angle, and trajectory of a high dry solids content black liquor spray, which is sprayed well above its atmospheric boiling point. The experiments were carried out in operating recovery boiler furnaces. The results were compared with full-scale spraying chamber tests. The information and measurement data of black liquor spraying achieved in the furnace environment give valuable information for furnace modeling, boiler design and control, and help to understand the in-furnace processes involved. Validated initial data for CFD calculations is essential.

The spray research under in-furnace conditions is introduced as a very useful method of studying black liquor spraying practice with real black liquor, in a real environment with industrial-scale nozzles. The furnace endoscope, developed during this work, made this possible. It was the first attempt to systematically obtain information about high dry solids black liquor spraying under in-furnace conditions.

Flashing inside the nozzle was found to be a factor key to the whole spraying process of high dry solids black liquor. It has a major role in spray disintegration and initial velocity, both of which correlate very well with the final drop size and shape. A dry solids content of approximately 75% was observed to be the limit that forced boiler operators to change their spraying practice from non-flashing to flashing mode. Dimensionless velocity can be used in categorizing the disintegration processes. Regardless of the disintegration mechanism, it is possible to find the dominating frequency in disintegrating spray with techniques based on image analysis.

This thesis consists of an overview and of the following 6 publications:

  1. Miikkulainen, P., Kankkunen, A., and Järvinen, M. P., 2004, Furnace endoscope – Measuring fuel spray properties in hot and corrosive environments, Experiments in Fluids, vol. 37, no. 6, pp. 910-916. © 2004 by authors and © 2004 Springer Science+Business Media. By permission.
  2. Miikkulainen, P., Järvinen, M., and Kankkunen, A., 2000, Black liquor spray properties in operating recovery boiler furnaces, 5th European Conference on Industrial Furnaces and Boilers (INFUB 2000), Porto, Portugal, 11-14 April 2000. © 2000 INFUB. By permission.
  3. Miikkulainen, P., Järvinen, M., and Kankkunen, A., 2002, The effect of a furnace environment on black liquor spray properties, Pulp and Paper Canada, vol. 103, no. 9, pp. 34-38. © 2002 Pulp and Paper Technical Association of Canada (PAPTAC). By permission.
  4. Miikkulainen, P., Kankkunen, A., and Järvinen, M., 2002, The effect of excess temperature and flashing on black liquor spray properties, IFRF Finnish-Swedish Flame Days 2002, Vaasa, Finland, 24-25 September 2002. © 2002 by authors.
  5. Kankkunen, A., and Miikkulainen, P., 2003, Particle size distribution of black liquor sprays with a high solids content in recovery boilers, IFRF Online Combustion Journal, Article Number 200308, December 2003. © 2003 by authors.
  6. Miikkulainen, P., Kankkunen, A., Järvinen, M., and Fogelholm, C.-J., 2005, Predicting droplet size from black liquor spray characteristics, TAPPI Journal, vol. 4, no. 5, pp. 11-17. © 2005 by authors.

Keywords: black liquor, recovery boiler, furnace, spray

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© 2006 Helsinki University of Technology

Last update 2011-05-26