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40 / January 2020 powderbulk.com THE PRACTICALITIES AND BENEFITS OF INLINE TECHNOLOGY FOR MONITORING MIXING This article examines the practicalities and benefits of inline technology for monitoring mixing processes, focusing on the technique of drag force flow measurement, which provides highly sensitive, real-time data. Experimental studies illustrate the capabilities of this process monitoring technique for a range of mixing and blending applications. John Yin, Freeman Technologies Dr. Valery Sheverev, Lenterra informational flow from a single analysis every hour or two to a continuous data stream tracking the pro- cess minute by minute. Offline analyses are not only infrequent but also temporally offset from the process due to delays introduced by sampling, transferring the sample to the lab, analyzing the sample, and delivering the results. These delays significantly complicate the challenge of maintaining optimal operations. In con- trast, with real-time data it's possible to: • immediately detect deviations from a given pro- cess setpoint to consistently maintain the process in the preferred operating range, • reduce overprocessing by stopping at a precisely defined, optimal endpoint, • and minimize any downtime associated with waiting for results, such as with a batch release, thereby maximizing unit throughput. Understanding the generalized benefits of inline processing can be helpful in making the most of your mixing and blending processes. However, it's also important to be aware of the downsides of relying solely on offline measurement techniques to find your materials' homogeneity specifications. The reality of offline measurements' impact on the process The goal of mixing or blending is typically to process materials to an acceptable level of homogeneity, which happens at a very specific period in the process. Pro- cessing time is influenced by the physical properties of the particles or powders, including particle size, mor- phology, surface texture, and cohesion. Processing time can also be controlled by manipulating critical process- ing parameters, including the geometry and design of the vessel and impeller, and, once these are fixed, impeller speed. In the absence of inline measurements, T he need to blend multiple powders or mix pow- ders with liquids is commonplace across the bulk powder processing industries. The asso- ciated processes that come with blending and mixing are energy-intensive and have the potential to damage primary particles depending on the particles' friabil- ity and the processing conditions applied. Just enough processing to reach a satisfactory endpoint is highly desirable from the perspective of minimizing variable costs, as minimal processing will mitigate the negative impacts of overprocessing and will maximize equip- ment usage (material throughput). Achieving this goal of a satisfactory endpoint relies on the timely detection of homogeneity, and one of the best ways to do that is with real-time process monitoring. The benefits of real-time monitoring Over recent decades, real-time process monitoring using inline instrumentation has become increas- ingly prevalent across the processing industries, and there are sound reasons for this trend. For starters, such measurements typically involve minimal process disruption, if any at all, since they eliminate sample- removal requirements. Measuring materials in situ, meaning within the process, captures data for a much larger proportion of the process stream than is feasible via discrete sampling and offline analysis. Addition- ally, inline systems measure materials under process conditions, which is particularly beneficial for powders, since powder properties are dependent on the stress and strain rates applied to the material. For these rea- sons, inline powder measurements can be significantly more representative than offline and at-line testing. Above all, the greatest benefit of inline technology is its ability to deliver better representative data in real time. Switching to real-time measurements transforms