Kinetics of switch grass pellet thermal decomposition under inert and oxidizing atmospheres

Sriraam R. Chandrasekaran, Philip K. Hopke

Research output: Contribution to journalArticle

Abstract

Grass pellets are a renewable resource that have energy content similar to that of wood. However, the higher ash and chlorine content affects combustion. Thermal degradation analysis of a fuel is useful in developing effective combustion. Thermogravimetric analysis (TGA) of the thermal degradation of grass pellets under inert (nitrogen) and oxidizing (air) atmospheres was conducted. Non-isothermal conditions were employed with 4 different heating rates. Kinetic parameters (activation energy and pre-exponential factors) were estimated using the iso-conversional method. Both pyrolysis and oxidative atmospheric thermal degradation exhibited two major loss process: volatilization of cellulose, hemicelluloses and lignin and burning or slow oxidation of the residual char. The activation energy and pre-exponential factors were high for the oxidizing environment. During pyrolysis, major decomposition occurred with 40% to 75% conversion of the mass to gas with an activation energy of 314. kJ/mol. In air the decomposition occurred with 30% to 55% conversion with an activation energy of 556. kJ/mol. There was a substantial effect of heating rate on mass loss and mass loss rate. The TG shifted to higher temperature ranges on increasing the heating rate. In both pyrolyzing and oxidizing conditions, average combustion and devolatilization rates increased. Enhanced combustion takes place with higher activation energy in oxidizing atmosphere compared to the inert atmosphere due to presence of air.

Original languageEnglish (US)
Pages (from-to)52-58
Number of pages7
JournalBioresource Technology
Volume125
DOIs
StatePublished - Dec 1 2012
Externally publishedYes

Keywords

  • Combustion
  • Gasification
  • Grass pellets
  • Pyrolysis
  • Thermal degradation

ASJC Scopus subject areas

  • Bioengineering
  • Environmental Engineering
  • Renewable Energy, Sustainability and the Environment
  • Waste Management and Disposal

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