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14 Ash-Forming Matter and Ash-Related Problems

Part 4. Solid Fuels

  1. Maria Zevenhoven,
  2. Patrik Yrjas,
  3. Mikko Hupa

Published Online: 15 JUL 2010

DOI: 10.1002/9783527628148.hoc068

Handbook of Combustion

Handbook of Combustion

How to Cite

Zevenhoven, M., Yrjas, P. and Hupa, M. 2010. Ash-Forming Matter and Ash-Related Problems. Handbook of Combustion. 4:14:493–531.

Author Information

  1. Åbo Akademi University, Process Chemistry Centre, Åbo/Turku, Finland

Publication History

  1. Published Online: 15 JUL 2010


Deposit formation, that is, fouling and slagging, corrosion, and sintering are often cause for unwanted shutdowns of boilers. These problems are ash related. The composition and physical state of ash determines if problems may occur and where and when.

Ash properties depend on the way ash-forming matter is present in a fuel, how it is released from the fuel, and process conditions in the furnace.

This chapter is dedicated to the more challenging fuels like biomass-derived fuels that nowadays are used as a replacement for coal. Examples are taken from 92 fuels extracted from the Åbo Akademi fuel database, a collection of fuel analyses carried out at Åbo Akademi University during the last decade.

Fuel characterization and analysis of ash-forming matter in fuels will be discussed. Here, the analyses of the association of ash-forming matter by chemical fractionation are emphasized. Release of ash-forming matter and the formation of ash will be examined. Here, knowledge obtained from the fuel analyses plays an important role. Formed ash may cause deposits on heat exchanger surfaces, agglomeration of bed material in a fluidized bed, or corrosion. Nowadays, biomass fuels are often co-fired, either with positive or negative effects on boiler availability. All these above-mentioned phenomena can be seen from a chemistry point of view, where understanding of interaction of ash forming and melting behavior of ashes is seen to be vital.


  • ash-forming matter;
  • biomass fuel;
  • boilers;
  • co-fired fuels;
  • deposit formation