Hydraulic transport of mineral and ore products: friction losses of stratified flows at high solids concentrations
1996 (English)Doctoral thesis, comprehensive summary (Other academic)
The overall objective of the work presented in this thesis was to investigate the hydraulic transport of mineral and ore products with regard to friction losses in horizontal pipelines at high solids concentrations. In detail, the objectives are to present and examine experimental pilotscale and large-scale friction loss results, and to investigate the performance of a scaling relationship for stratified slurry flows with regard to the effects of pipe diameter and solids concentration. The experimental results are from pilot-scale and large-scale loop-tests in 0.1-0.44 m in diameter pipelines of coarse sands and coarse and high-density industrially comminuted mineral and ore products. Volumetric solids concentrations of up to about 40% were studied at velocities of practical interest, i e well above risks of stationary deposition and lower than about 6 m/s. The effects of pipe diameter and concentration on friction losses were investigated for aqueous coarse sand slurries in 0. 1-0.44 m in diameter pipelines at delivered volumetric solids concentrations of up to about 40%. The ratio of d85/d50 (d50 is the mass-median particle size and d85 the particle size for which 85% by mass is finer) varied between 1.2-7.3. With the intermediately graded sands, the relative solids effect was lower in larger pipe diameters than accounted for by a scaling relationship presented in the literature. This relationship relates the relative solids effect to mean velocity. The influence of pipe diameter was less distinct for narrowly and broadly graded sands. In the scaling relationship, the solids effect increases in proportion to solids concentration. This was confirmed for all sands at solids concentrations below 20%, and for the intermediately graded sands with solids concentrations of up to about 40%. At solids concentrations greater than 20% by volume, a non-linear decrease in solids effect with increasing solids concentration was found with broadly graded sands. An opposite trend, a non-linear increase in solids effect with increasing solids concentration, was seen with narrowly graded sands. Experimental results showed energy-efficient pseudohomogeneous-like flow behaviour when a mixture of coarse (20 - 200 mm) granite rock in tar-sand tailings (-1 mm) in mass proportions 1:9 was transported at a total volumetric solids concentration of 31% in a 0.44 m in diameter pipeline loop. Similar results were obtained with an industrially comminuted copper ore (-100 mm; mass-median particle size 0.75 mm) when pumped in a 0.2 m in diameter pipe at a concentration of 39%. The favourable friction loss performance in some results may demonstrate how broad particle size distributions and high concentrations may cause reduced pipe wall friction without influence of true rheological mechanisms. The different hydrodynamic mechanisms active in the near wall region in the lower part of the pipe are discussed in light of the results obtained here for different particle size distributions and solids concentrations. Furthermore, difficulties and sources of error in large-scale pipelineloop experiments are discussed.
Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 1996. , 16 p.
Doctoral thesis / Luleå University of Technologyy… → 31 dec 1996, ISSN 0348-8373 ; 195
Research subject Water Resources Engineering
IdentifiersURN: urn:nbn:se:ltu:diva-17733Local ID: 4e7f0330-f5a4-11db-ac79-000ea68e967bOAI: oai:DiVA.org:ltu-17733DiVA: diva2:990738
Godkänd; 1996; 20070428 (ysko)2016-09-292016-09-29Bibliographically approved