CFD simulation of a spiral-channel dust separator for removal of black powder from natural gas pipelines

Abstract

A spiral-channel dust separator was investigated experimentally and numerically for its efficiency to separate black powder from natural gas pipelines. Effects of gas flowrates and concentration of black powder on separation efficiency and pressure drop were studied. The size distribution (0.15–5 µm) of the black powder particles was measured. Efficiency for the finest particles (mean 0.327 µm) reached 86%, compared to < 1% for a high-efficiency Stairmand cyclone of equal throughput capacity. The separation efficiency reached spiral-channel dust separator 100% for particles > 1 µm. Results of CFD simulations are reported for velocity and pressure fields in the channels, particle separation contours, and local enrichment within the channels. Calculations showed that the radial contraction and diversion of the gas flow at the separator's outlet generated highly decontaminated air above the clean air inlet tube. The distance between the separator outlet and the cleaned gas inlet has been identified as a significant design parameter due to its impact on the separation efficiency. Modeling results showed further that reducing the swirling angle of the channels leads to a decrease in pressure drop with minimal effect on separation efficiency. An evaluation of the RNG k-ε code is provided as well.