Impacts of flow velocity and microbubbles on water flushing in a horizontal pipeline

TL;DR

This study uses CFD modeling validated with field data to analyze how flow velocity and microbubbles influence water flushing efficiency in pipelines, revealing optimal conditions for reducing water consumption and improving cleaning performance.

Contribution

The paper introduces a CFD-kinetic theory model for pipeline flushing, validated with real data, and systematically studies the effects of flow parameters and microbubbles on flushing efficiency.

Findings

Higher water velocity reduces water consumption by 28%.

Small microbubbles facilitate flushing and reduce water use by 35%.

Large bubbles hinder flushing and increase water consumption by 23%.

Abstract

Water flushing to remove particle sediment is essential for safe and continuous transport of many industrial slurries through pipelines. An efficient flushing strategy may reduce water consumption and the cost associated with water usage, and help water conservation for sustainability. In this study, a computational fluid dynamics (CFD) model coupled with the kinetic theory of granular flow for the flushing process is presented. The CFD models were validated against field data collected from a coal slurry pipeline of 128 $km$ in length, 0.575~$m$ in diameter, achieving an average error of less than 15\% for outlet solid concentration over time. A parametric study evaluated the effects of water velocity (1.88-5.88~$m/s$), bubble size (50~$\mu m$, 150~$\mu m$, and 1000~$\mu m$) and bubble volume fraction (0.05-0.2) on flushing performance including pipeline cleanness, cleanness efficiency, and water consumption. The obtained outcomes indicate that higher water velocity is preferred and an increase in water velocity from $1.88~m/s$ to $5.88~m/s$ reduces the water consumption by $28\%$. Large bubbles may hinder the flushing process and increase the water consumption by $23\%$. Remarkably, small bubbles facilitates the flushing process and lead to $35\%$ reduction in water consumption. These effects are attributed to the turbulent characteristics in the pipelines in presence of microbubbles.