(373ab) Spatial and Temporal Hydrodynamic Parameters in a 0.3 m Diameter Bubble Column Using Wire Mesh Sensors and Pressure Transducers

Bubble columns are widely used as multiphase reactors in chemical, petrochemical, and biochemical industries owing to their ease of operation and construction. Though there are extensive experimental and numerical investigations reported on the design and scale-up of bubble column reactors, the design of these reactors is still an art than science. Accurate temporal and spatial measurements of the two-phase flow parameters in bubble columns are very useful for developing numerical simulation models. Hence in the present work, an attempt has been made to perform temporal and spatial measurements of the void fraction and bubble size distributions in a 30 cm diameter cylindrical bubble column.

A pair of Wire Mesh Sensors and five pressure transducers were employed to quantify the hydrodynamic parameters in the air-water bubble column reactor operated in a homogenous flow regime. The Wire Mesh Sensor system used in the present work was manufactured by HDZR Innovation (Germany). It consisted of two layers of mesh 50 mm apart. Each mesh, in turn, consisted of two layers of 64 stainless steel wires of 0.4 mm diameter. These layers were separated by a vertical gap of 3.15 mm and rotated 90 degrees relative to each other, to form a square mesh. These Wire Mesh Sensors were installed at two axial locations which were 70 cm apart, one close to the air sparger at the bottom of the bubble column and the other located in the fully developed region. Experiments were performed to capture the steady state gas-liquid flows and the transient gas injection and gas disengagement processes. The transient data was acquired at a sampling frequency of 1000 Hz for both pressure transducers and Wire Mesh Sensors.

The principle of Wire Mesh Sensor measurements and algorithms for estimating the void fraction and analyzing the bubble properties from the raw experimental data have been discussed in detail in our previous publications. The void fraction results obtained from the WMS are compared against the void fraction results obtained from the Pressure Transducers. The bubble size data is compared against the theoretical bubble size data reported in the open literature. The measurement uncertainty of the WMS for air-water two-phase flows is investigated by repeating the experiments. The effect of superficial gas velocity (range: 6-60 mm/s) on the transient/steady state void fraction data and bubble size distribution has been analyzed. These experimental investigations disclose the quantitative measurements of the transient and steady state flow parameters which have not been reported so far, and this data can also be used in validation of CFD models developed for bubble column simulations.