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36 / July 2020 powderbulk.com stream that has significantly different physical proper- ties than a stream without the recycled material? An experiment was conducted to answer these ques- tions and demonstrate if strategic reintroduction of the captured material would produce a compacted flake that maintains the original blend homogeneity without significantly changing the final product. The process efficiency of blend uniformity was studied by simulating recycle feeds and observing the resulting output. This was achieved using a dual-chamber feed hopper design available on some production-scale roller compactors. The dual-chamber feed allows recycled material to be directed to the feed stream using a segmented compartment in the main feed hopper where recycled material is combined with raw material process feed. The experiment used lactose powder as the raw material and red extrafine sugar as the simulated recycled material. The intent was to produce a quali- tative, visual representation of how well the captured and redirected material could be reintroduced to the feed stream. During normal dry granulation operation, the fines generated are commonly recycled into the feed hopper. Utilizing a feed system that allows for controlled, even delivery of the recycled material is critical to main- taining the efficient mixing of a recycle stream. The functionality of this type of feed system eliminates the potential of nonhomogeneous product mix from affecting the compaction process. In other words, the system shouldn't process raw material and recycled material differently. Rather, the recycled material should be evenly mixed into the raw material feed to create a homogeneous process feed stream that can be maintained for the process run. Test methodology A stream of red, extrafine granulated sugar represent- ing the segregated and captured fines was dosed into the recycle section of the feed hopper at three differ- ent rates: 5.0 kg/h, 10.0 kg/h, and 20.0 kg/h. The roller compactor was configured to run at approximately 100 kg/h of total throughput. The objective criteria for the testing was to generate a uniform red granule (sugar) distribution in the flake exiting the compaction rollers of the machine. Over a period of several minutes, the sugar distribution pattern was observed and evaluated for consistency and homogenous distribution. The pro- cess was repeated at the different speed setpoints and the results were compared. A consistent uniform dis- tribution indicated efficient mixing action of raw and recycled material from the feed assembly. cessfully, the resulting granulated material will have a particle size distribution that meets the final material specification and can be reliably and predictably han- dled and delivered to a tablet press for transformation into a stable oral solid dosage form. The significance of this process is that it helps in maintaining powder blend homogeneity. For example, a powder comprised of three ingredients that differ in size and mass will separate based on those parameters if no action is taken to prevent the segregation. By compressing the homogeneously blended powder in this process, the powder's homogeneous makeup is locked using Van Der Waals forces to create granules that are a blend of all three ingredients. Depending on the particular characteristics of the powder blend and depending on the final product's particle size distribu- tion requirements, additional mechanical separation techniques can be employed to separate and capture fines that have escaped the rollers or been sieved out of the final material. This yields a granulated powder with a tight particle size distribution of the homogeneous granules. Reintroducing (recycling) off-size granules into the raw material feed What happens to the segregated material that was screened out of the final material? Does it become waste? The answer to that question varies from product to product and from company to company. In general, however, a reasonable assumption would be that the desired objective would be to capture the material and find a way to reintroduce it back into the process to eliminate waste. Taking this step, however, raises the question of whether the captured material can be rein- troduced to the raw material process feed in a way that continues to maintain the desired content homogene- ity. Would this reintroduction produce a process feed KEEP THE LATEST INFORMATION AT YOUR FINGERTIPS. WWW.POWDERBULK.COM/SUBSCRIBE