화학공학소재연구정보센터
Chemical Engineering Science, Vol.56, No.8, 2859-2866, 2001
Study of mixing in gas-fluidized beds using a DEM model
This paper examines the usefulness of a discrete element method simulation in studying solids mixing in gas-fluidized beds. At steady state, a part of the solids were tagged with a dark colour and the rest were tagged with a light colour. The state of mixing of bed solids was studied by analysing the variation of the proportions of the marked particles with time and position in the bed. This was achieved by scanning the bed using a sampling box. The variance of mixture composition based on the samples was incorporated into a mixing index which describes the degree of mixing of the particles at a particular time. This method enables assessment of the overall mixing behaviour in terms of the rate of mixing (through estimation of the time required for the mixing index to increase from zero to a certain value), together with the degree of mixing at the mixing equilibrium. Illustrative examples show that gas velocity and particle properties are important parameters influencing solids mixing in bubbling fluidized beds.