Investigation of wetting and drying process in a spout-fluid bed using acoustic sensor and electrical capacitance tomography

To investigate complex gas-solids flow characteristics of a spout-fluid bed with bafflers in wetting and drying process, a non-intrusive measurement technique combining pressure, acoustic transmitters and an electrical capacitance tomography (ECT) sensor is proposed in this paper. The proposed approach can collect acoustic and pressure signals and realize visualization in three flow regions separated by two bafflers synchronously. By ECT images and power spectrum and wavelet analysis of the pressure drop signals, two typical flow state transitions in the wetting and drying process can be identified. The result analysis based on acoustic transmitter indicates that the particle-wall collision frequency band is narrow and the particle-particle collision frequency band is wide. A key recurrence quantization parameter of acoustic signal, Laminarity, increases with the decrease of particle flowability. The parameter of Laminarity combined with the capacitance signal related to the particle moisture content can effectively reflect the wetting rate and provide an accurate monitoring of de-fluidization process in the bed.