Application of high-frequency impedancemetry approach in measuring the deposition velocities of biomass and sand slurry flows in pipelines

Abstract

Since the lower limit to operating velocities in slurry transport systems is influenced by deposition conditions, measuring the “deposition velocity” is an essential step in slurry pipelines’ design and operation. This study proposes a new experimental technique in measuring deposition velocities in slurry pipeline transport called the high-frequency impedancemetry approach. This non-invasive technique of measuring electrical properties of substances, based on their frequency-dependent behavior, was applied using a 16-electrode impedancemetry device on a 25m long closed-circuit pipeline to measure the deposition velocities of sand- and biomass–water mixture flows. Slurries of play and gravel sands, as well as wheat straw and wood chips biomass feedstock, were prepared over a range of concentrations (1.5–20wt% dry-matter), and deposition velocities were measured over a wide range of operating velocities (0.04–4.5m/s). Experimental measurements for sand–water mixtures were found to be in good agreement with empirical correlations derived previously through various analytical and mathematical techniques. In addition, for the first time, the deposition velocities for biomass–water mixtures were measured and found to be in the range of 0.21–0.8 m/s; surprisingly well below the common range of commercial pipelines’ operating velocities, i.e., 1.4–3.0m/s.