Slug Characterization in Multiphase Flow with Electrical Capacitance Tomometry – Frame by Frame Analysis of Raw Capacitance using Wavelets and Eigenvalues

Y. Ru, S. Mylvaganam

Faculty of Technology, Department of Electrical Engineering, Information Technology and Cybernetics, Telemark University College, N- 3901 Porsgrunn, Norway

Abstract

In multiphase flow, runaway flow phenomena can occur due to escalating slug flows in pipelines. Build-up of slugs can lead to serious outcomes to the operation of the plant, in the worst case leading to expensive and extensive plant damage and even loss of life. Timely characterization of slug flow and continuous monitoring of flow velocities and flow regimes can help in achieving safe and continuous plant operation. It is useful to know the slug parameters in addition to the flow velocities. Parameters of interest with respect to the slugs are slug size, velocity and frequency. Study of slugs using non-intrusive twin plane electrical capacitance tomographic (ECT) system has been done before. In this paper, bypassing image processing, raw capacitance values, on a frame by frame basis, are analysed using wavelet decomposition and eigenvalues. The Electrical Capacitance Tomometric (ECTm) approach is used in this paper with the data obtained from a twin plane ECT system. Slug size; frequency and velocity are calculated using two different methods: wavelet decomposition and eigenvalues of raw capacitance data, all done on a frame by frame basis, leading to a new set of time series. The new set of time series lends itself amenable for correlation based estimation of the slug parameters in both the wavelet and eigenvalue domains. The slug parameters calculated using these two different approaches are compared and the overall results are discussed.

Keywords: Electrical Capacitance Tomometry (ECTm), slug parameters, wavelets; frame-by-frame raw capacitance, eigenvalues