We are producing a powder product in batch and the problem is there are lumps in the final product. When I check the raw material, it is in powder form and most of it can pass through Mesh 810 micron. The lump isn't made up of all raw materials in the mix. It comes from one raw material that does not have hydroscopic problem. Even though that raw material is crushed before mixing, the lumps still happen. Also, I would like to know how long the mix time should be when we are dealing with raw material that has hydroscopic. Can heat be generated if the time of mixing is longer? Does the sequence of mixing of raw material affect the final product?
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Tom Blackwood Forum Moderator 19 Posts
Re: Why are there lumps during mixing?3 January 2012 at 1:29pmIt sounds like you have the wrong type of mixer for this application. I can't be specific without knowing the chemicals involved, but hydroscopicity may be a factor. Also, one material may be of a much finer size than the other one or have a highly conductive surface (i.e., metal). The October 2009 issue of Chemical Processing has an article entitled "Clamp Down on Clumping." The factors that lead to clumping are outlined and techniques to avoid clumping are described. The leading cause is moisture. The article doesn't go into detail about equipment types and how they may be prone to clumping, but most mixers that result in clumps should be modified to have a high shear section mounted at right angles to the mixer shaft to break up the lumps. Mixing time and intensity needs to be determined experimentally. There are no theoretical models.