An Investigation into Blow Tank Performance and Solids Friction for Pneumatic Conveying of Fine Powders

Abstract

An accurate estimation of design parameters such as blow tank initial pressurization, blow tank aeration, total pipeline pressure drop and solids friction factor is important for reliable design of fluidized dense-phase pneumatic conveying systems. This report presents the results of an investigation carried out to provide these important design parameters for fluidized dense-phase conveying of cement. Cement (median particle diameter: 14 µm; particle density: 3060 kg/m^3; bulk density: 1070 kg/m^3) was conveyed through four different pipelines (viz. 43 mm I. D. × 24 m length, 54 mm I. D. × 24 m length, 54 mm I. D. × 70 m length and 69 mm I. D. × 24 m length) over the wide range of flow conditions (from fluidized dense-phase to dilute-phase flow). Pneumatic conveying characteristics based on total pipeline pressure drop were developed for all the pipelines, which showed a clearly defined pressure minimum curve for all the pipelines except for 69 mm I.D. × 24 m long pipeline. Two existing models of solids friction for horizontal straight pipe sections were compared with experimental results. Pressure drop across bends was obtained by using Chamber and Markus formula. A power function based model was developed for solids friction using the straight pipe pressure drop data of 54 mm I.D. × 24 m long pipeline and is evaluated for all other pipelines. Models were found to give good predictions for total pipeline pressure drop at higher solid discharge rates. Blow tank characteristics were plotted to study the effect of blow tank initial pressurization and aeration on material discharge rate. It has been found that material discharge rate increases with an increase in blow tank initial pressurization and mass flow rate of top and fluidization air. It is concluded that blow tank performance has huge impact on the overall performance of the pneumatic conveying systems.