Abstract: By adopting dual-plane electrical capacitance tomography（ECT） technique,the velocity measurement of multiphase flow was transformed to the time delay estimation problem.Aiming to improve the reliability and accuracy of velocity measurement,common time delay estimation methods and their features were analyzed,and a twin-plane ECT system was developed and applied to monitoring pneumatically conveyed coal ash in a pipeline in real time.The velocity of gas/solid two-phase flow in this process ranges from 0 to 14 m/s,the mass ratio of coal ash and gas is about 10/1~40/1,and the range of granularity is generally 2 m~2 mm.Time delay estimation algorithms based on higher-order statistics and wavelet transformation were implemented respectively to calculate solid velocity in a horizontal pipe of inner diameter 125 mm,and the experiment results demonstrated the feasibility of the proposed method.Due to the non-Gaussian and non-stationary features of the two-phase flow signals,the wavelet transformation-based algorithm is more accurate,and the differences between the results of time delay estimation algorithms based on cross-bispectrum and wavelet transformation are about 1 m/s.