Detection of solid contaminants in gas flows using microwave resonant probes

The presence of undesirable solid contaminants can have adverse effects on the integrity of gas pipelines. One of the most common contaminants in such pipelines is black powder. Developing predictive maintenance protocols, including online quality monitoring, is imperative to ensure the on-spec supply of gas to customers and to avoid severe consequences such as pipeline blockage. In this paper, a microwave sensing system that utilizes resonant probes for the detection and monitoring of solid contaminants, is presented. The proposed probe is essentially a conventional circular waveguide with a resonant iris structure attached to the aperture. The concentration of solid contaminants in gas flows is assessed by analyzing the scattering parameters of transmitting/receiving probes at a resonant frequency, which are coupled non-intrusively to the pipeline. 3D electromagnetic simulations are performed for sensitivity analysis of the proposed sensing system. Furthermore, the detection and evaluation of solid contaminants are experimentally validated using air/sand flow in a 51 mm inner diameter pipeline. The efficacy of the proposed system is demonstrated following the successful detection of solid contaminants in the dual-phase flow. Additionally, it is also illustrated that inclusion of a resonating iris structure in the aperture of the circular waveguide results in enhanced sensitivity when compared to a non-resonant counterpart.