Estimate of solid flow rate from pressure measurement in circulating fluidized bed

Abstract

A method is described to estimate solid mass flow rate based on measurement of pressure drop in horizontal section of circulating fluid bed (CFB). A theoretical model was derived based on momentum balance equation and used to predict the solids flow rate. Several approaches for formulating such models are compared and contrasted. A correlation was developed that predicts the solids flow rate as a function of pressure drop measured in the horizontal section of piping leading from the top of the riser to the cyclone, often referred to as the cross-over. Model validation data was taken from literature data and from steady state, cold flow, CFB tests results of five granular materials with various sizes and densities in which the riser was operated in core-annular and dilute flow regimes. Experimental data were taken from a 0.20 m ID cross-over piping and compared to literature data generated in a 0.10 m ID cross-over pipe. The solids mass flow rate data were taken from statistically designed experiments over a wide range of Froude number U g 2 g D , 25 – 2 00 , load ratio G s ρ g U g , 0. 2 – 23 , Euler number 2 Δ P Horiz ρ g U g 2 ,2 – 5 0 , density ratio ρ p − ρ g ρ g , 6 0 – 2 000 , Reynolds number ρ g U g d p μ g , 6 0 – 16 00 , and Archimedes number ρ s − ρ g ρ g d p 3 μ g 2 , 29 – 95 00 . Several correlations were developed and tested to predict the solids mass flux based on measuring pressure drop in the horizontal section of CFB. It was found that load ratio G s ρ g U g is a linear function of the Euler number 2 Δ P Horiz ρ g U g 2 and that each of these expressions all worked quite well ( R 2 > 95%) for the data within the range of conditions from which the coefficients were estimated.