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 25 m 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 (1.5-20 wt% dry-matter), and deposition velocities were measured over a wide range of operating velocities (0.04-4.5 m/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., 1.4-3.0 m/s.

Experimental Study on Two-Phase (Solid-Liquid) Flows of Ground Wheat Straw in Inclined Pipes

“…Visual observations (despite the dark brown background, which made the analysis challenging) showed no bed formation for 6.4 mm particle size wheat straw-water slurries across the whole range of mass concentrations (C m = 5%-30%) running down the inclined pipe section of any of the slopes (-7° to +21°) used in the current investigation, even at the minimal slurry velocity of 0.5 m s -1 . This outcome was on par with an earlier study on the deposition velocity of biomass particles, in which it was discovered that this velocity was 0.21-0.28 m s -1 for slurries of wheat straw particles with d 50 = 4.81 mm for C m = 5%-20% in horizontal flows (Vaezi et al, 2018). Further, in the earlier work, the terminal settling velocity (v t ) of several particle lengths (5-30 mm) of wheat straw was evaluated as 13-17 mm s -1 in a quiescent medium and it was found that these particles were buoyant (i.e., (v m / v t ) ≤ 0.021), specifically for v m ≥ 0.5 m s -1 and particle sizes of 5-10 mm (Javed et al, 2022a).…”

Resolved CFD-DEM simulations of the hydraulic conveying of coarse grains through a very-narrow elbow

“…In addition, piping systems frequently contain horizontal and vertical portions and changes of direction via elbows and tees, making the design of conveying systems complex. Therefore, the prediction of flow patterns, pressure drops, sedimentation and erosion rates, transport rates, clustering, clogging, and jamming in liquid-solid piping systems re-mains challenging [5,6].…”

CFD-DEM Simulation to Predict the Critical Velocity of Slurry Flows

“…Slurry pipeline transport is a commercially viable mode of transporting solid commodities as an alternative to truck and rail; nevertheless, it is a complex process (Vaezi, Verma and Kumar, 2018). The environmental and economic advantages of this method rather than by road or rail are being increasingly recognized by mining companies (Bhabra, 2013).…”

“…It was found that viscosity plays an important role in the sand minimum transport condition. A new experimental technique to measure deposition velocities in pipeline transport of solids was proposed by (Vaezi, Verma and Kumar, 2018). The authors used high-frequency impedancemetry, a non-invasive technique, to determine the deposition velocities of sand-water and biomass-water mixtures over a wide range of concentrations and pumped over a range of velocities much wider than the common industrial practice.…”