Ash behavior during hydrothermal treatment for solid fuel applications. Part 2: Effects of treatment conditions on industrial waste biomass

Mikko Mäkelä*, Kunio Yoshikawa

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

22 Citations (Scopus)

Abstract

This second half of our work on ash behavior concentrates on the effects of hydrothermal treatment conditions on paper sludge. Ash composition and solubility were determined based on treatment temperature, reactor solid load and liquid pH using experimental design and univariate regression methods. In addition, ash properties for combustion were evaluated based on recent developments on ash classification. Based on the results, all experimental variables had a statistically significant effect on ash yields. Only reactor solid load was statistically insignificant for char ash content, which increased based on increasing treatment temperature due to the decomposition of organic components. Ash dissolution and ash yield were governed by liquid pH and the generation of acids mainly due to the solubility of calcium carbonate identified as the main mineral species of paper sludge. Dissolution of calcium carbonate however decreased ash fusion temperatures more likely causing problems during char incineration. This indicated that decreasing the ash content of sludge during hydrothermal treatment can actually weaken ash properties for solid fuel applications.

Original languageEnglish
Pages (from-to)409-414
Number of pages6
JournalEnergy Conversion and Management
Volume121
DOIs
Publication statusPublished - 1 Jan 2016
MoE publication typeA1 Journal article-refereed

Keywords

  • Biosolids
  • Calcium carbonate
  • Experimental design
  • Hydrothermal carbonization
  • Multiple linear regression
  • Wet torrefaction

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