FBRM probe

Figure 6.8 Schematic of the FBRM probe tip (a), and chord lengths (b). (Reproduced, with permission, from www.lasentec.com.)...

Several attempts were made to evaluate the use of FBRM particle size analyzer as a potential tool for granulation end-point determination. Dilworth et al.f have compared power consumption, FBRM, and acoustic signals in a study of a wet granulation process in Fielder PMA 200 mixer. It was found that these techniques were complimentary, with FBRM probe capable to follow median granule size growth even when the power consumption curve showed a plateau. 

R"", respectively and the set U is compact subset of R" . We suppose that the full state X may be measured using an ATR-FTIR probe in the liquid and an FBRM probe for the solid phase the control input applied to the system in the interval is... 

Polythermal methods have in common that a suspension containing known amounts of solvent and solute in excess is heated and the temperature where last particles dissolve is detected. For detection, visual observation (e.g., under a microscope), turbidity measurements, particle-detecting inline probes (e.g., FBRM probe (Lasentec , Mettler Toledo GmbH)), or calorimetry may be used. Since it is a dynamic method, the results depend on dissolution kinetics of the particular system. In general, polythermal measurements are easier to automate since just a temperature has to be followed and no special analytical technique is required. The above-mentioned Crystall6 multiple reactor system can also be used to perform such kind of measurements. To detect both the dissolution process for derivation of saturation temperatures (clear points) and the formation of particles (cloud points) for determination of the metastable zone width, the... 

Figure 8.20 A seeded costal lization process monitored by an FBRM probe. It can be seen that while the temperature is decreased slowly from 75 °C to 60 C, the number of particles only increases moderately while the average particle size increases. Upon further decrease of...

CSM has coupled the FBRM with a second probe, the particle video microscope, PVM (Lasentec/Mettler Toledo), which consists of six illuminating near-infrared lasers (850 nm) that are transmitted into the sample. While the FBRM provides precise quantitative tracking of the chord lengths, the PVM probe provides qualitative images of the hydrate particle size and degree of agglomeration. The size range scale of hydrate particles that can be measured with the PVM probe is 10-300 i,m. 

Fig. 8 Crystallization apparatus showing in-situ sensors (FBRM at upper right, PVM at upper left, FTIR spectrometer with ATR probe at left in the background). Antisolvent pump not shown.

Tadayyon, A. Rohani, S. Control of fines suspension density in the fines loop of a continuous KCl crystallizer using transmittance measurement and a FBRM(R) probe. Can. J. Chem. Eng. 2000, 78 (4), 663-673. 

A major disadvantage of the FBRM method is that the measured CLD does not directly represent a PSD. Conversion of CLD to PSD is not straightforward and requires sophisticated mathematical software that is not easy to validate. Moreover, CLD depends on optical properties and shape of the particles, as well as the focal point position. The total number of counts measured is a function both of solids concentration and probe location. 

With the advancement of online measurement techniques such as focused beam reflectance measurement (FBRM) and Fourier transform infrared (FTIR), it is now possible to obtain particle size distribution and solution concentration information rapidly through these in-situ probes. In one experiment, hundreds of data points can be generated. With proper experiment design, the model-based experimental design for crystallization is capable of obtaining high-quality crystallization kinetic data with a small number of experiments. This approach can thus save significant experimental effort and time in the development of crystallization processes. 

A similar method to PVM and FBRM is BVI (bulkvideo imaging), wherein a video camera is used through an observation window of the reaction vessel or a process endoscope employed. Simon et al. [26] used this technique coupled with UV-vis spectroscopy, FBRM, and calorimetry to monitor the crystallization of caffeine and palm oil. UV-vis spectroscopy and calorimetry were used for validation. BVI was shown to detect the boundaries of the metastable zone with comparable or better performance than FBRM and UV-vis probes. 

Commercially available FBRM and PVM probes can provide information concerning particle dimension and morphology, but provide none of the indispensable chemical information (structure, oxidation state, and coordination) necessary to elucidate active states and evolving catalyst species. 

The process analytical technology described by Simon et al. [26] consists of a combination of an ATR UV-vis probe (Hellma Analytics) and a probe for FBRM (Mettler Toledo). The bulk phase is also monitored by BVI using a Sony video camera that captures 25 frames s . This system is well suited for studying the changes in solid particles. For monitoring the reactions driven by solid catalysts, additional Raman and ATR-FTIR spectroscopic probes can be immersed in the reaction mixture as shown in Figure 3.1. In principle, this concept is also applicable to reactions under pressure however, for such applications, stainless... 

---