DEVOLATILIZATION OF SOLID WASTE PARTICLES AND COMBUSTION OF VOLATILES IN A FLUIDIZED BED: MODELING AND EXPERIMENTAL VALIDATION

Choi, Jinhwan; Choi, Sangtnin

doi:2004.9.4.143

Environmental Engineering Research 2004;9(4): 143-153. DOI: https://doi.org/10.4491/eer.2004.9.4.143

DEVOLATILIZATION OF SOLID WASTE PARTICLES AND COMBUSTION OF VOLATILES IN A FLUIDIZED BED: MODELING AND EXPERIMENTAL VALIDATION

Jinhwan Choi, and Sangtnin Choi^†

Department of Mechanical Engineering Korea Advanced Institute of Science and Technology Yusong-Gu, Daejon, 305-701, Korea

Corresponding Author: Sangtnin Choi ,Tel: +82-42-869-3030, Fax: +82-42-862-1284, Email: smchoi@mail.kaist.ac.kr

Received: April 14, 2003; Accepted: July 14, 2004.

ABSTRACT

Devolatilization and char combustion of solid fuel particles of which typical size was in the order of 2cm and combustion of evolved volatiles were investigated, using two different FBCs (fluidized bed combustors). By varying the combustion conditions, fraction of bunt carbon was estimated from gaseous concentration measurements in a laboratory-scale FBC and the fraction of the original volatiles burnt above the bed was determined from the calorimetric calculation in a semi-pilot-scale FBC. Combustion of solid particle and volatiles in a FBC was modeled by a simulation model where two sub models were introduced; a particle combustion model and a three-phase bed model. The particle combustion model considered devolatilization and char combustion, external and internal heat and mass transfer, and changing fuel properties. The three phase mathematical model for a fluidized bed described the bed hydrodynamics and gas exchange between phases as well as the combustion of volatiles from the fuel particle. The particle combustion model provided the inlet conditions for the fluidized bed model such as gaseous products and the fluidized bed model provided the combustion environment for the particle combustion model. Comparison of the experimental results and the predicted results by the model showed a good agreement as to the fraction of carbon conversion and the fraction of volatiles burnt in the freeboard. Interrelation of the fluidized bed conditions and particle combustion was adequately treated in this simulation model by combining the particle combustion model and the fluidized bed model.

Keywords: devolatilization | char combustion | fluidized bed combustor | particle combustion model | three phase bed model