Slagging and fouling characteristics during co-combustion of Scots pine bark with low-temperature dried pulp and paper mill chemical sludge

Research output: Contribution to journalArticleScientificpeer-review

Researchers

  • Alejandro Grimm
  • Jarkko Etula

  • Roushdey Salh
  • Gunnar Kalén
  • Markus Segerström
  • Jörg Brücher
  • Christer Söderberg
  • David Soukup
  • Christoph Pfeifer
  • Sylvia H. Larsson

Research units

  • Swedish University of Agricultural Sciences
  • Umeå University
  • Holmen AB
  • University of Natural Resources and Life Sciences, Vienna
  • Iggesund Paperboard AB

Abstract

This paper shows how chemical sludge (CS) generated during wastewater treatment at a paperboard mill can be quickly dried at low-temperature and employed in bark-fired boilers to reduce slagging and corrosion problems. By using a cyclone-dryer operated at an inlet-air velocity of 110 m/s and a temperature of 90 °C, the dry-matter content of CS was increased from approximately 19 to 82%. The residence time of CS inside the cyclone was approximately 2 s when using the inlet-air velocity mentioned above. Disaggregation of the feedstock caused by collisions with the cyclone wall and between particles played a crucial role in enhancing the efficiency of heat and mass transfer. Three co-pelletized mixtures of Scots pine bark (SPB) and dried-CS were combusted in a 40 kW fixed-bed burner. Flue gas analysis was performed with a gas analyser. Coarse and fine ash were analysed by SEM-EDS and XRD. NOx and SO2 emissions increased with increasing amount of CS in the mixtures. Mono-combustion of SPB resulted in a large quantity of slag (i.e., molten ash) with a high degree of sintering (i.e., hardness of the slag), and ash deposits formed on heat transfer surfaces were rich in K2SO4 and KCl. Mixtures of SPB and CS were less prone to slagging, and the amount of alkali chloride in the deposits was reduced in favour of alkali sulphate formation.

Details

Original languageEnglish
Pages (from-to)282-294
Number of pages13
JournalFuel Processing Technology
Volume193
Publication statusPublished - 1 Oct 2019
MoE publication typeA1 Journal article-refereed

    Research areas

  • Combustion, Drying, Fouling, NO, Pulp and paper mill sludge, Slag, SO

ID: 34480405