Use of a Fiber-Optic Turbidity Probe to Monitor and Control Commercial-Scale Unseeded Batch Crystallizations

Abstract

This article describes how a fiber-optic turbidity probe may be used as an inferential sensor to aid in the control of commercial-scale batch crystallizations. The discussion focuses on several unseeded crystallization examples involving cooling or cooling plus addition of antisolvent. In a typical control scheme, the fiber-optic probe is used to detect an initial nucleation event, to control a subsequent digestion step for fines dissolution with the potential for modification of nuclei size, number, and purity, and then to monitor a growth period. During the digestion step, temperature is increased and adjusted to achieve a desired reduction in the fiber-optic signal in order to control the extent of digestion. Within Dow, this approach has proven to be robust and cost-effective for numerous commercial-scale batch crystallizations including those with highly fouling or corrosive environments.

Solid–Liquid Suspension in Pilot Plants: Using Engineering Tools to Understand At-Scale Capabilities

“…Turbidity is caused by absorption and scattering mechanisms that reduce the amount of light traveling in a straight line. 1 Turbidity meters are typically used to monitor 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 crystallizations and determine the "cloud point," or the point at which crystals begin to formi.e. when the batch turns from clear to opaque.…”

Process Characterization of Polyvinyl Acetate Emulsions Applying Inline Photon Density Wave Spectroscopy at High Solid Contents

“…Due to the high turbidity already at low polymer solid contents, commonly used inline Process Analytical Technologies (PAT) to monitor reaction progress or even particle size (distributions), like turbidity probes or optical inline microscopy are limited in their application and are less suitable to investigate polymerization processes [ 19 , 20 , 21 ]. To monitor the reaction processes or particle growth in turbid emulsion polymerization processes, Photon Density Wave (PDW) spectroscopy has shown to be a reliable method under certain conditions [ 22 , 23 ] by measuring the optical scattering properties.…”

Shear‐induced crystallization of isotactic polypropylene studied by simultaneous light intensity and rheological measurements

“…We fabricated a bifurcated optical fiber probe similar to those previously used in injection molding studies [75, 76] and in the pharmaceutical and specialty chemical industries [77]. As shown in Fig.…”