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Mixing & Blending Q&A

  •   I need to add upwards of 20+ kilograms of a chemical powder that has very similar consistency to flour to a large (~5,000 L) processing tank. The problem lies with the fact that when the powder is currently poured in bag form, things get messy. The stuff can fly everywhere, it’s difficult to handle, and when it is poured into the tank we’re having trouble making sure that the powder even makes it into the solution (it goes all over the walls). (Please note, making a liquid molar solution and adding it to our tank is not viable for our process). This is all biotech, so the amount of chemical needed to be added is very precisely calculated. Having a loss due to spillage or the chemical not reaching the solution means failed quality test results. What I want to know is if there is a practical lifting system (remember these tanks are huge and you must currently climb a staircase to reach the top of the tank and pour this stuff) along with a practical and a decent way to make sure the powder will make it all the way inside the tank and into the solution?

    There are a number of different potential methods to feed 20 kg of your fine powder into a processing tank. Depending upon the powder flow properties and precision of the dose required, you could use a mechanical or pneumatic conveying system to deliver (“lift”) the powder to a surge bin with a volumetric or gravimetric feeder located above the processing vessel to provide a more automated addition process. An alternative would be to measure out the powder increments precisely into a drum and use a drum inversion system to lift and then dose the powder into the processing vessel. Both these methods would provide an improved level of powder containment and reduction in dust generation compared to manually pouring the material into the processing vessel from a bag.

    With respect to reducing the amount of material coating the walls of the processing tank, providing a more controlled material stream into the vessel at a consistent (and potentially lower) addition rate may help to reduce the dust generation within the vessel and powder sticking to the walls. Measuring the flow properties of your powder is a recommended first step in designing a reliable feed system to the processing tank. Please contact us directly if we can assist you further.

  •   I make custom blends for a hot chocolate mix. I am used to blending only powders, but I want to use a little concentrate liquid flavoring. I was told that I should be ‘plating’ the liquid onto salt or sugar. What does that mean and how do I do it?

    We have commonly heard the term “plating” refer applying a minor liquid on a coarse particle and at least partially coating the particles to distribute the liquid rather than have it cohere preferentially to the fines fraction of a blend. This is often done in a high shear mixing process via a liquid addition nozzle. There are other common terms used to describe the state of saturation as a liquid is introduced to a powder/solid particles, including the common states during agglomeration (pendular, funicular, capillary). Please contact us if we can provide any further information.

  •   We are trying to mix fine and sticky powder with abrasive larger particles. To break the segregation of fine powder, we mix in solvent and dry them afterward. After drying, we have to grind it down and pass the sieve. They are will mixed but we lost part of fine powder during the sieving. As a result, we don’t have a consistent process. Is there a better way for mixing? Or is there a way to dry the paste without needs of grinding and sieving?

    We would need more information about your current process to assist further, but there are methods of mixing, including wet granulation in combination with fluid bed drying that may reduce the need for post-blending milling. In addition, there are agitated drying processes that may reduce the need for additional milling. Also, it may be possible to improve your milling and sieving process to reduce the creation and loss of fines, including processes where the fines are recirculated. Please feel free to contact me if we can assist you further.

  •   When I see variation in my product, how do I know if I have a problem with my mixer performance or segregation in the mixer-to-packaging system?

    As a starting point, collecting and analyzing stratified samples from the mixer and final product can provide an initial basis for focusing on whether the variation source is the mixer or the product. If the variation of the mixer samples is high, the key mixing process parameters (mixing time, mixer capacity, etc.) will first need to be investigated. If the variation of the mixer samples is low, focus on reducing the segregation potential in the mixer-to-packaging transfer system. Reducing the segregation in the transfer system may include conducting flow and segregation tests on the material, reviewing the stratified product samples to establish a root cause of the variation and potentially collecting additional process samples, after which you can begin to develop corrective process and equipment modifications to address the segregation.