Focused beam reflectance measurement for monitoring the extent and efficiency of flocculation in mineral systems

Abstract

Focused beam reflectance measurement (FBRM), where a scanning laser focused through a sapphire window measures real‐time reflected chord distributions without solids dilution, is attractive for characterizing flocculation performance. An enhanced measurement principle in new FBRM instruments has implications for flocculation studies, demonstrated using hematite in synthetic Bayer liquor. Comparisons of previous (M500) and new (G400) instruments were complicated by the impact of their different physical dimensions upon flocculation hydrodynamics, but the G400 clearly measured larger chords. The original measurement principle based on a reflected intensity threshold counts large low‐density aggregates as multiple chords; in contrast, the change to “edge detection” (very low threshold) is more likely to see a single chord, an advantage for studying mineral systems (aggregates often >500 µm). The G400 also captures bimodal character in unweighted chord distributions, producing distinct peaks for aggregates and fines after suboptimal flocculation; such peaks are rarely well resolved in older FBRM. © 2013 American Institute of Chemical Engineers AIChE J, 60: 251–265, 2014

Water Soluble Polymer Flocculants: Synthesis, Characterization, and Performance Assessment

“…Aggregate Size : Aggregate size can be obtained by different methods such as laser diffraction spectroscopy, dynamic image analysis, optical imaging, and sensing zone techniques . We, however, focus our discussion here to focused beam reflectance measurement (FBRM) as a relatively new and effective aggregate sizing technique, that allows for on‐line and in situ characterization of aggregate size without the need for sampling and dilution even in very high concentration slurries (i.e., 20%) …”

“…FBRM also assigns several weightings on the chord lengths, with the square‐weighted counts in macro mode being more favorable for assessing the extent of flocculation with respect to the large aggregate formation. Unweighted counts in prime mode are more sensitive to fines and surface features …”

“…[233,242] We, however, focus our discussion here to focused beam reflectance measurement (FBRM) as a relatively new and effective aggregate sizing technique, that allows for on-line and in situ characterization of aggregate size without the need for sampling and dilution even in very high concentration slurries (i.e., 20%). [243,244] Figure 46 represents a schematic of FBRM. The optic elements, generating a focused laser beam (near infrared), rotates at a fixed speed of about 2-8 ms −1 scanning across aggregates in suspension close to the sapphire window.…”

Heterocoagulation of alumina and quartz studied by zeta potential distribution and particle size distribution measurements

“…These relatively coarse particles could not be reflected in the number weighted distribution as their number was too small (less than 0.01%), but they made up a large proportion in the volume-weighted distribution. It was proposed that the number weighted distribution is suitable when the small particles are focused while the volume-weighted distribution is suitable when the large particles are focused [29,30]. In this paper, both number and volume weighted distributions were analyzed and reported.…”

Aggregate structures formed by hyperbranched functionalized polyethylene (HBfPE) treatment of oil sands tailings

“…Deionized (DI) water was used to make a 1 % flocculant stock solution followed by gentle mixing at 150 rpm for 16 h. A 5 wt% MFT sample (200 g), diluted in DI water (pH = 7.0), was used in all experiments. The mixing set‐up comprised a pitched four‐blade impeller in a glass beaker equipped with a G400 focused beam reflectance measurement (FBRM) probe (Mettler Toledo). CaCl 2 was dosed to the diluted MFT (1 g Ca 2+ /1 kg solids) either before (in the case of A‐PAM) or simultaneously with polymer addition (in the case of HB f PE), as described in Botha et al A dosage of 1000 ppm (1 mg polymer/1 kg solids) was used in all flocculation tests.…”