Combustion Rate Analysis of a Char Particle Produced by Pyrolysis of Surplus Activated Sludge in Nitrogen-Oxygen Atmosphere

Abstract

The combustion rate of a char particle produced by the pyrolysis of surplus activated sludge was measured in N₂-O₂ atmosphere by using a micro thermo-gravimetric analyzer (TGA). The effect of combustion temperatures, ambient oxygen concentrations, pyrolysis temperatures and particle-diameters of a char on the combustiom rate was studied.
As a result, the following conclusions were drawn for the range of the present experimental conditions :
1) At combustion temperatures below 550°C, the overall combustion rate is controlled by the rate of chemical reaction and is proportional to the first order of the oxygen concentration and the carbon concentration in the solid particle, simultaneously.
2) The combustion rate constants are considerably affected by the oxygen content within a char particle produced. It is observed that both the energy of activation and the frequency factor of reaction decrease with increase in oxygen content.
(3) It is suggested from a comparison of the present results with the existing kinetics data for coal chars that the combustibility of a char particle produced from a coarse solid fuel may depend on oxygen content. Thus, conclusion (2) is applicable to the extent of coal chars.