Spatially resolved inline measurement of liquid velocity in trickle bed reactors

The flow pattern in trickle bed reactors is of an inhomogeneous nature due to a random packing structure. Thus, the local values for liquid phase ratio and velocity are spread over the whole cross-section and a global determination of these values ignores the fact that local phenomena dominate mass and heat transfer and eventually the reactor efficiency. Only if both parameters can be locally quantified, can a realistic picture of the flow fields be drawn.A new wire-mesh sensor (WMS) setup based on the measurement of electrical permittivity of fluids was used, which can be applied to the packings of porous catalyst particles. A calibration method is proposed to get access to the liquid saturation. Axial velocity distributions are measured via a method based on the spatial tracer pulse time-of-flight between sensing points of two WMSs installed at a distance of few millimeters. The effects of gas and liquid flow rates on local liquid velocities were analyzed.The proposed technique was validated against liquid collector data, which showed very good agreement. For this purpose, distributions of the volumetric flow rate were calculated by applying the continuity equation to the saturation and velocity data obtained from WMS.