Expansion of multi-jet bed with large particles

An experimental investigation under cold conditions was made to study the effect of some operating parameters on average porosity in a 1·1 m long, 0·35 m wide and 1·2 m high multi-jet bed (Ingnifluid type) with air flow rate varying from 1200 m³ h⁻¹ to 3500 m³ h⁻¹ and total bed inventory from 26 kg to 45 kg. Rice, peas and one rice-pea mixture (mass ratio 70–30) of sizes 1·95 mm, 5.0 mm and 2·44 mm, respectively, were used as bed material to simulate coal particles. Average bed porosity was estimated based on pressure drop along the bed height. It was found to be in the range 0·58 to 0·72, 0·51 to 0·62 and 0·55 to 0·65 for rice, peas and rice-pea mixture, respectively. One mathematical correlation has been developed from the experimental results to predict average porosity as a function of air flow rate, total bed inventory and particle size used. This correlation is developed for hydrodynamic modelling of an industrial multi-jet combustor.