Calibration of solids concentration optical fibre probes with solids‐polymer blocks

Abstract

Owing to the determinant effects of the local distribution of solids concentration on transport phenomena, particularly in gas‐solids flows in such processing units as gas‐solid fluidized beds and pneumatic conveying lines, its accurate measurement has received considerable attention. Despite the widespread applications of optical fibre probes for the measurement of local solids concentration, these instruments may create measurement uncertainties due to their structural designs and challenges in their accurate calibrations. Several calibration methods have been proposed in the literature, while they need to be further improved. In the present study, we calibrated in‐house, fabricated, solids concentration mixed parallel optical fibre probes by two sets of solids‐polymer blocks covering solids volume fractions in the range of 0‐0.30. The uniform blocks were produced by a twin‐screw extruder and an injection moulding machine. FCC particles, 86 μm in diameter, formed the dispersed solids in the blocks, while poly styrene and poly methyl methacrylate were separately acting as the transparent medium. They helped us investigate the effects of the refractive index of the medium and the probe tip design on the calibration curve. The blind distance (zone) in front of the adopted probes was determined, at about 0.70 mm, upon measuring their reflective curves. Two glass windows with 1.00 and 1.60 mm thicknesses were separately installed at the tip of a probe to study their effects on the calibration curve. Experimental results indicated that in the absence of a glass window, the probes' voltage readings varied nonlinearly with solids concentration, the voltage readings were higher for blocks with a higher refractive index of the transparent medium, while the normalized calibration curves were similar for both sets of solids‐polymer blocks. In addition, the extent of the uniform distribution of illuminating and reflecting fibre strands at the tip of a mixed parallel optical fibre probe can change the degree of nonlinearity of its calibration curve. The application of glass windows thicker than the blind distance decreased the degree of nonlinearity of the calibration curve, yet did not completely eliminate it.

Synthesis of Li4Ti5O12 negative electrode material in a fluidized bed thermogravimetric analyzer

“…From the data in Figure 3, we see that u cf decreases as the temperature is increased (0.83‐0.93 cm/s at 25°C; 0.78‐0.85 cm/s at 300°C; 0.65‐0.76 cm/s at 600°C). These results are in part due to the increase in dynamic viscosity and the decrease of the density of air used as fluidizing agent, [ 23,24 ] and the reduction in the agglomerate density as a result of the mass loss. The change in u cf is also the result of the growth of the agglomerates as the temperature increases and approaches the melting temperature of Li 2 CO 3 (723°C).…”

Special issue in honour of Professor Jamal Chaouki

“…We are pleased to report that 30 papers were initially submitted to the journal and after peer review, following the standard journal procedures, 28 papers were accepted. Due to the page limitation of each issue, we have decided to publish a full special issue with 16 papers as Part 1 [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] and a special section in the coming issue (vol. 99, issue 12) with 12 papers as Part II.…”

Bubble behaviour investigation in a wet fluidized bed using digital image analysis

“…[ 15 ] Shabanian and Chaouki found a moderate interparticle force, which could contain smaller bubbles, in a cohesive bed compared with a non‐cohesive bed. [ 16 ] Zhong et al reported that higher liquid viscosity resulted in higher fountain height and non‐uniform distribution in the fountain centre and provided an efficient method to simulate wet fluidization with the two‐fluid model. [ 17 ] Generally, wet particles are harder to fluidize due to the attenuation of kinetic energy during the process of particle collisions.…”