Thesis

Experimental and modelling study on the release of potassium during biomass combustion

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Awarding institution
  • University of Strathclyde
Date of award
  • 2020
Thesis identifier
  • T16104
Person Identifier (Local)
  • 201668915
Qualification Level
Qualification Name
Department, School or Faculty
Abstract
  • Understanding the release mechanism of potassium (K) is crucial in tackling alkali metal-induced ash problems during the combustion process of biomass. This thesis focuses onenhancing the knowledge on the release mechanism of potassium experimentally anddeveloping a model to predict the release profiles of potassium compounds from biomass.In the beginning, the thesis investigated the thermal characteristics of biomass and itsmajor chemical components in a thermogravimetric analyser (TGA). According to thetests, the thermal conversion process of natural biomass and be predicted through theanalyses of artificial biomass, which is the mixture of major chemical components. Theresults illustrate the feasibility to use major chemical components as initial inputs in thebiomass combustion model. Biomass combustion experiments were then performed in ahigh-temperature furnace-balance system (FBS). The results revealed that the finaltemperature affects the K transition the most. Over 60% of the initial K was lost as thefinal temperature increased from 30℃ to 1000℃. The heating rate affects the K transitionduring combustion by influencing the devolatilisation of volatile matter related K and thestructural changes of particles. The higher the heating rate, the more release of K. Thedeveloped kinetically controlled model was validated and used to estimate the release ofdifferent K compounds under different scenarios. The results indicate that KCl is themajor compound released at the early stage of combustion, followed by KOH and K₂SO₄.Analysing the reaction path of K reveals that KO and KO₂ are the most criticalintermediate species during combustion. The initial concentration of Cl significantlyaffects the release of major species: KCl, KOH, HCl and K₂SO₄; while the initialconcentration of S can affect the release of KOH and K₂SO₄ at high temperatures. Theexistence of O₂ in the system favours the formation of KO and KO₂, and thus to controlthe release of major K species.
Advisor / supervisor
  • Li, Jun
  • Lue, Leo
Resource Type
DOI
Date Created
  • 2019

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