Calculation of the parameters of the hydraulic transport of enrichment waste in polyethylene pipes

Abstract

In the article, a new method is presented for calculating hydraulic slope and critical speed of cleaning reject hydrotransportation through the polyethylene pipelines, which is based on the Methodology for Calculating Hydrotransport Plants for Tailings Transporting and Inwashing at the Iron Ore Mining and Processing Enterprises. This methodology was approved by the State Construction Committee of the Ukrainian SSR in its Temporary Instructions on Technology of the Tailing Dump Arrangement and was used in the design of all of the waste storage facilities in the Krivyy Rih ore-dressing and processing enterprises. For the conditions of the experiments, it was shown that experimental multiplier in the formula for calculating critical speed of hydrotransportation was depended on the pipeline diameter, free fall acceleration, kinematic coefficient of water viscosity and absolute roughness of the pipe inner surface. The acknowledgement of these factors made an empirical constant in the considered formula dimensionless and close to average value of the constants in the formulas obtained by other similar methods. With the considered method, it is proved that experimental constant in the formula for calculating critical speed of hydrotransportation is inversely proportional to the cubic root of the roughness of the pipeline inner surface, while coefficient of proportionality is a universal constant, which does not depend on the properties of the pipeline material and is equal to 10.1. Therefore, for determining critical speed of hydrotransportation through the polymer pipes by using this method, it is necessary to multiply critical speed for steel pipe with a similar diameter by the cubic root of ratio of roughness of the inner surfaces of the steel and polymer pipelines. It is further shown that value of hydraulic slope significantly depends on the operating coefficient, which shows by how many times coefficient of friction hydraulic resistance in the polyethylene pipe operating in supercritical flow regime exceeds the same value in case of critical flow regime for the same pipe. The research results allowed finding formulas for calculating hydraulic slope and critical speed of the iron-ore cleaning reject hydrotransportation through the polyethylene pipelines, which are based on the dependencies obtained for the steel pipes and value of absolute roughness of the pipeline inner surface.