Experimental quantification of the head loss coefficient K for fittings and semi-industrial pipe cross section solid concentration profile in pneumatic conveying of polypropylene pellets in dilute phase

Pneumatic conveying in diluted phase is often employed due to its low acquisition and maintenance costs to displace pellets, sawdust and grains. Such a project requires pressure drop and solid concentration profile data. This work aimed at quantifying a) the coefficient K to calculate the fitting pressure drop and b) solid concentration profile in a vertical pipe after a fitting. The experimental unit was built in acrylic ducts with an inner diameter of 117mm. The following singularities were studied: standard tee through side outlet without extension and with three different extensions and a 90° curve with three pieces. The solid used in this study was polypropylene in pellets, conveyed by air. Mathematical models obtained for the prediction of the K coefficient for the bend and tees exhibited an adjusted coefficient of determination of 0.83 and 0.84, respectively. Regarding pressure drop and the solid concentration profile, the 90° bend showed a high homogeneous distribution and lower pressure drop values. However, the use of the tee standard or with 30mm extension is recommended, to avoid unit shut down for maintenance and possible loss of material in case of breakage, due to an intense abrasion at a single point.