(72a) Measurement and Imaging of Gas-Solid Systems Using Electrical Capacitance Volume Tomography

Electrical Capacitance Volume Tomography (ECVT) is a non-invasive imaging technology recently developed for multi-phase flow applications. It is based on distributing flexible capacitance plates on the peripheral of a flow column and collecting real-time measurements of inter-electrode capacitances. Capacitance measurements here are directly related to dielectric constant distribution, a physical property that is also related to material distribution in the imaging domain. Reconstruction algorithms are employed to map volume images of dielectric distribution in the imaging domain, which is in turn related to phase distribution. ECVT is suitable for imaging interacting materials of different dielectric constants, typical in multi-phase flow systems.

ECVT is being used extensively for measuring flow variables in various gas-solid flow systems. Recent application of ECVT include flows in risers and exit regions of circulating fluidized beds, gas-solid bubble columns, trickle beds, moving beds, and slurry bubble columns. ECVT is also used to validate flow models and CFD simulations. The technology is uniquely qualified for imaging phase concentrations in various energy applications as it exhibits favorable features of compact size, low profile sensors, high imaging speed, and flexibility to fit around columns of various shapes and sizes. ECVT is also safer than other commonly used imaging modalities as it operates in the range of low frequencies (~1 MHz) and does not radiate radioactive energy.

High temperature and pressure gas-solid reactors are widely used in industry. Deep understanding of flow behavior in such reactors is limited due to the complex hydrodynamics that exist in the bed. In this effort, ECVT is used to study flow behavior in various gas-solid systems and at different conditions. Case studies that involve bubbling beds, moving beds, and slugging at temperatures up to 900C will be presented. Real-time images and quantitative data acquired in those experiments provide a very unique insight into gas-solid systems at harsh conditions.