A fluidised bed reactor is designed to carry out multi-phase reactions, usually where we a fluid (gas or liquid) reactions with heterogeneous catalyst. The fluid is injected from the base of the reactor with sufficient energy to suspend solids and hence provide the maximum surface area for the process reaction to proceed.
A key to reactor performance is good solids distribution and even gas flow at different parts of the reactor so that the process conditions are homogenous, materials consumed efficiently and side reactions to not develop.
These conditions are generally very difficult to measure non-invasively. However capacitance tomography provides a basis for taking valuable data.
The dielectric constant of particulate solids present in fluidised beds are significantly different to those of the injected gases. This provides a basis for capacitance tomography to image the distribution of solids across the bed as conditions change. The relative permittivity of the solids can be related to solids concentration allowing the effective homogeneity of the system to be measured.
Capacitance data can be taken rapidly and this provides a basis for instantaneous changes to be observed, in addition ITS software allows time averages to be taken allowing the identification of any “dead spots”.
Capacitance sensors can usually be installed around model reactors and moved up and down the reactor to provide data on solids distribution under different reaction conditions.