Issue link: https://www.e-digitaleditions.com/i/1197147
January 2020 / 45 and particles beginning to coalesce, as observed in Case Study 2. Liquid addition continues during Phase 2, but at this point, the choppers in the mixer have been switched on. These break down larger agglomerates, reducing particle size and decreasing FPM. Phase 3 coincides with switching off the choppers, which allows the particles to further grow and densify as mixing continues. By the beginning of Phase 4, liquid addition has ceased, and more friable agglomerates are being broken down, limiting the potential for any further increase in FPM; the process has essentially reached its endpoint with little further bene t associ- ated with additional processing. Indeed, there is some evidence of a slight reduction in FPM, particularly with the low water-content sample, a trend associated with agglomeration breakdown. This data clearly shows the DFF sensor's ability to differentiate the impact of varying levels of water addition and to elucidate different phases of the water-addition process. It's worth noting that real-time process monitoring using inline instrumentation isn't meant to replace of ine measurements completely. Inline instrumen- tation, such as DFF sensors, should be tested via experiments, such as the ones presented here, until the preferred inline instrument has been proven to match of ine measurements. At that point, the inline instrumentation can be used as the primary method for monitoring processes with the of ine tool being used as necessary, particularly with nal quality check product speci cations, which are subject to routine of ine checks. Case Study 3: Investigating the impact of liquid addition in a vertical single-shaft mixer In the nal study, a DFF sensor was used to investigate the impact of adding different quantities of liquid to a powdered food blend. Measurements were made with a vertical single-shaft mixer, adding liquid to a level of 1, 2, and 4 weight percentage (wt%). The liquid addition rate was adjusted to maintain a consistent liquid addi- tion time across all three measurements. The FPM data displayed in Figure 9 for all three liquid concentrations shows similar trends and four clear phases of the wet massing process. At the start of liquid addition, Phase 1, FPM values rise. This can be attributed to the capillary bonds growing in strength FIGURE 9 Real-time force pulse magnitude data closely tracks liquid addition, clearly differentiating the mixtures and identifying different phases of the wet massing process. FPM moving average data for batches with varied liquid content FPM (moving average, n = 35), N Time, seconds 1 wt% 2 wt% 4 wt% Phase 1 Phase 2 Phase 3 Phase 4 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 0 20 40 60 80 100 120 FIGURE 8 There is close agreement between the drag force ow and potentiometric titration data with both indicating that the blend reaches a state of homogeneity after approximately 24 to 25 seconds of mixing. FPM moving average data, Formulation 1 FPM (moving average, n = 30), N Mixing time, seconds Measurement 1 Measurement 2 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0 6 12 18 24 30 36 42 48 54 60 NaCl content of Formulation 1 NaCl content, % Mixing time, seconds NaCl content location 1 NaCl content location 2 Target NaCl content 70 65 60 55 50 45 40 12 18 24 30 36 42 a. b.