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.
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Enhancement of the Use of Wood Fuels in Heat and Power Production in Integrated Pulp and Paper Mills

Jukka-Pekka Spets

Dissertation for the degree of Doctor of Technology to be presented with due permission of the Department of Mechanical Engineering for public examination and debate in Auditorium K215 at Helsinki University of Technology (Espoo, Finland) on the 12th of December, 2003, at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-6422-6)   [403 KB]
Errata (in PDF format)
Dissertation is also available in print (ISBN 951-22-6421-8)

Abstract

The drying of moist biofuels such as wood-based biomasses should be as effluent-free and as energy-efficient as possible in order to ensure the safe and economical operation of industrial CHP plants. This work presents a multistage drying system (MSDS), which provides significant benefits in comparison with earlier conventional single dryer systems. This new application is installed most promisingly in integrated pulp and paper mills. The MSDS, which simultaneously uses secondary process energy, as well as backpressure and extraction steam as the drying energy, enables a smaller volume flow of drying air than single dryer systems. Depending on the structure of the system, up to 100 % of the exhaust drying air can be utilized as combustion air. The use of MSDSs enables an increase in CHP plant boiler capacity, which in turn boosts the production of power and heat in combined heat and power (CHP) plants. Additionally, the improvement in CHP can be achieved with reduced organic emissions from moist biomass drying. Also, the amount of unburned organic compounds and of CO in flue gases from combustion is reduced as a result of the improved quality of the biofuels. When compared to direct steam drying, the MSDS also better minimizes, or even eliminates, the formation of organically loaded condensates in the drying operation.

This thesis consists of an overview and of the following 5 publications:

  1. Spets J.-P., 2001. A new multistage drying system. Proceedings of the 1st Nordic Drying Conference. Trondheim, Norway, 27-29 June 2001, Paper no. 13. © 2001 SINTEF. By permission.
  2. Spets J.-P. and Ahtila P., 2001. Preliminary economical examinations for a new multistage biofuel drying system integrated in industrial CHP-power plant. Proceedings of the 1st Nordic Drying Conference. Trondheim, Norway, 27-29 June 2001, Paper no. 14. © 2001 SINTEF. By permission.
  3. Spets J.-P. and Ahtila P., 2001. A new multistage biofuel drying system integrated into an industrial CHP-power plant: description of process and performance calculations. Proceedings of 2001 ACEEE Summer Study on Energy Efficiency in Industry. New York, USA, 24-27 July 2001, Vol. 2, pages 67-78. © 2001 American Council for an Energy-Efficient Economy (ACEEE). By permission.
  4. Spets J.-P. and Ahtila P., 2002. Improving the power-to-heat ratio in CHP plants by means of a biofuel multistage drying system. Applied Thermal Engineering 22, No. 10, pages 1175-1180. © 2002 Elsevier Science. By permission.
  5. Spets J.-P. and Ahtila P., Reduction of organic emissions by using a multistage drying system for wood-based biomasses. Drying Technology – An International Journal, accepted for publication. © 2003 by authors and © 2003 Marcel Dekker, Inc. By permission.

Errata of publications 1, 2, 3, 4 and 5

Keywords: multistage drying system, energy efficiency, combined heat and power production (CHP)

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© 2003 Helsinki University of Technology

Last update 2011-05-26