Average Particle Size and Instantaneous Mass Flow Rate Estimation in Dilute Phase Pneumatic Conveying Systems using ECT

U. Datta2, and S. Mylvaganam1,2

1Telemark University College, Faculty of Technology, Kjølnes Ring 56, N-3914 Porsgrunn, Norway,

2Tel-Tek, Kjølnes Ring, N-3918 Porsgrunn, Norway, Email: Saba.Mylvaganam@hit.no

ABSTRACT

The dilute phase solid/gas pneumatic conveying system being essentially a high velocity system leads to particle degradation. Breakage of solid particulates is caused due to inter particle collisions, particle- wall collision etc. at high operating gas velocity. This causes the difference in particle size and size distribution in the sample obtained from the downstream process and the feeding sample. Therefore it is important to develop a non-intrusive technique to measure particle size online. Here by fitting the measured solid velocity using ECT into best suitable gas/solid flow model for vertical dilute phase pneumatic system an attempt is made to calculate mean particle size. The statistical analysis shows that the model proposed is capable of estimating mean particle size with a maximum relative error not greater than ± 20% of the mean true size. It is also noticed that at higher superficial air velocity the error is reduced to even less than ± 6%. Online continuous measurement of mass flow rate can be used as a controlling factor in operational efficiency of pneumatic conveying system. In cases when the flow is uniform it is sufficient to estimate only average solid mass flow rate over a long period of time. But in case of non-uniform turbulent flows as both velocity and concentration fluctuates spatially and with time, it is more accurate to estimate instantaneous mass flow rate rather than average flow rate. The reconstructed image of ECT system is grouped into zones. The estimated instantaneous velocity and material concentration measured at each zones are used here for calculating instantaneous solid mass flow rate. The fluctuation of instantaneous solid mass flow rate is also compared with inlet air mass flow rate.

Keywords ECT, particle size, mass flow rate, dilute phase pneumatic conveying systems.