Monitoring Filtration in Trickle Beds Using Electrical Capacitance Tomography

Abstract

Experiments were carried out to monitor the evolution of the deposition of fine particles in trickle-bed reactors during the flow of nonpolar hydrocarbon oil-like liquid suspensions using electrical capacitance tomography (ECT) imaging. The accuracy of the ECT rendition was validated in the pristine (i.e., deposit-free) bed state by comparing the liquid holdup measurements from ECT with the liquid holdup from residence time distribution (RTD) measurements. The pulse-flow characteristics (pulse velocity and frequency) estimated from the ECT signals were in agreement with existing literature data. For filtration experiments, the effects of the initial liquid suspension distribution, the gas and liquid superficial velocities, and single-phase flow (i.e., zero gas velocity) on the structure of the deposition in the bed were studied. ECT imaging successfully tracked the unsteady-state progression of bed plugging throughout the trickle bed. It was found that increasing the liquid or gas superficial velocity resulted in increased local deposition. The transition, due to deposition, from trickle to pulse flow was also determined from ECT. In the case of stagnant gas, a filter cake formed on top of the bed.

Hydrodynamics of cocurrent two‐phase flows in slanted porous media—Modulation of pulse flow via bed obliquity

“…The Tikhonov algorithm was among the most successful reconstruction approaches. Moreover, application of ECT along with this reconstruction algorithm to determine liquid saturations in trickle-bed reactors was recently validated by Hamidipour et al 27 The same procedure was therefore used in this study to generate normalized permittivity maps from the measured capacitance data.…”

“…The dominant pulse frequency was extracted from the estimated averaged power spectral densities of the liquid saturation data assembled into [40 packets of 2048 data points each. 27 For all conditions, pulse flow history was recorded by ECT for 30 min at 50 Hz for straight and inclined configurations alike. Time series of liquid saturation which contained more than 2000 pulses were analyzed.…”

Modulation of suspension electrical conductivity to counter fines plugging in trickle-bed reactors

“…For clean conditions, the ECT sensor was calibrated between drained prewetted (as 0%) and flooded (as 100%) bed to provide liquid saturations. 25 Figures 8b-d illustrate these patterns corresponding to the previous experiments, i.e., no ECI injection, injection each 60 min, and each 30 min, respectively. For the same operating conditions, slightly different liquid patterns could arise from one bed filling to another depending on the microscopic structure of the bed and the forming flow paths.…”

“…3 mm over the column cross-section. 25 Moreover, the qualitative information unveiled about the structure of deposition under two-phase flow filtration conditions proved extremely rich and useful. 25 …”

“…The deposition pattern was shown to depend on the initial suspension distribution. 25 Here, the sensitivity to initial distribution is analyzed in the presence of ECI. For each experiment (i.e., each bed filling), the bed cross-section was divided into four quadrants (Figure 8a) and radial liquid distribution was measured in each quadrant using clean kerosene flow just before the switch to suspension flow (Figure 8a, Region 2).…”