Comparative study of two non-intrusive measurement methods for bubbling gas-solids fluidized beds: electrical capacitance tomography and pressure fluctuations

Conventional measurement techniques used to investigate the internal fluid flow processes in gas-solids fluidized beds are known to introduce disturbances to the flow. Two non-intrusive methods: pressure fluctuation measurement and electrical capacitance tomography (ECT) techniques have been usually used separately to study the complex two phase flow phenomena in fluidized beds. However, no systematic study has been carried out to compare these two methods in terms of their capabilities to reveal the hydrodynamic characteristics of fluidized beds. This paper presents a comparative study between these two non-intrusive measurement techniques within a bench-scale fluidized bed. Experiments were carried out using two alternative test sections (one equipped with pressure transducers, one with ECT sensor) for the same operating conditions. The performance of these two methods was evaluated against some important hydrodynamic parameters within fluidized beds, such as the determination of the minimum fluidization velocity, the determination of the minimum slugging velocity, dominant frequency and bubble rise velocity. The results demonstrate that the two measurement techniques can both provide broadly consistent results, although ECT tends to be more reliable with respect to estimating bubble rise velocity.