PROCESS EQUIPMENT UPDATE
not only eliminate the need for key blends, but also produce a better distribution of active ingredients.
THE LIMITATIONS OF TRADITIONAL MIXING EQUIPMENT Traditional equipment such as plough, ribbon and paddle mixers, which use blades or paddles to push material, are limited to moving the material within the confines of their active area. Te mechanics force the material bed outward, leaving dead spots inside the vessel where material moves more slowly or remains stationary. A stationary port at the bottom of such machines further isolates the material.
Another issue lies in the positioning of the intensifier bars, which should ideally be located in the mixing zone, where every particle passes through. Many times, however, traditional mixers position intensifier bars in dead zones, resulting in material not being fluidised properly and active ingredients getting incorporated throughout the batch. Traditional mixers also waste expensive
additives. Because additives initially contact only a very small portion of material in the vessel, they get quickly absorbed into the material bed, so more additives are usually needed to achieve the desired mix concentration, which increases cost.
THE BENEFITS OF TUMBLE BLENDING AND VACUUM TUMBLE DRYING To address the deficiencies of traditional mixers, a growing number of nutraceutical manufacturers use tumble blending. As a low-impact processing technique for handling sensitive or abrasive solids, tumble blending is commonly used to create precise nutraceutical blends that contain trace ingredients (<1%) that are vastly dissimilar in size and density. In contrast to traditional mixing, to eliminate dead spots, tumble blenders apply even turbulence in all corners of the mix through a combination of macro and micro blending. Tis can eliminate the need for key blends and produce a better distribution of active ingredients. Macro blending is achieved by rotating the shaped vessel, allowing the material bed to fall away from the vessel’s walls. Tumble blender vessel shapes are engineered to create a repeatable pattern in which the entire bulk material moves to form a homogenous mixture. Te blender moves at a precise speed, with the vessel wall at a
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precise angle, so that the material cascades over itself. Tere is no additional force from paddles, ploughs or spiral ribbons – just gravity.
While this occurs, micro mixing (if needed) simultaneously proceeds via agitator blades located in the mixing zone centre of the vessel, where fine processing in the material transpires. Tis allows for a gentle repeatable pattern that maintains a superior blending design while preserving the product’s physical characteristics. Together, the macro and micro mixing evenly expose each particle to six times more active blending per revolution than traditional mixers.
CASE STUDY
As an example, when APS worked with a large nutraceutical manufacturer in Nevada with a 40 component blend, the company was not using an agitator and had a laborious, overly complex blend process. “To make about 1,000 kilos of product a few times a year involved six or seven separate steps with key blends that had to be lab tested after each step to reach a final blend with the necessary traceability, materials and active components,” says Paffendorf. Trough onsite analysis of the manufacturer’s process, including examination of the physical characteristics of the powders used, APS determined that all of the components could be mixed in one step. Tis involved both macro and
micro mixing using a GEMCO tumble blender with an agitator to complete the process in a fraction of the time without key blends or excessive lab testing. “If you turn on the tumble blender
agitator, it can fluidise the entire bed of material and you get great product distribution because it helps to spread it out through the micro-mixing zone. According to the customer, the new process using a tumble blender with an agitator saves them about US$875,000 a year by eliminating the need for key blends and all the intermediate testing,” says Paffendorf. Douglas Van Pelt, a former part owner of a nutraceutical company, has also benefited from tumble blending. Van Pelt, who is now senior director of Operations at Sigmapharm Laboratories, a pharmaceutical company based in Philadelphia that develops, manufactures and markets generic and branded products, had successfully used tumble blenders at a previous company and trusted their capabilities. “At my previous employer, I made a product that had a narrow therapeutic range using a 30ft3
tumble
blender by GEMCO,” says Van Pelt, who notes that blend uniformity specification was a very stringent 95.0% to 105.0%, not a typical 90.0% to 110.0%. “Te potency was 0.125mg inside a 125mg tablet, and we were able to achieve blend uniformity in 15 minutes, with good repeatable results every time.”
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