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Educator system, powder and liquid mixing

  • 1.  Educator system, powder and liquid mixing

    Posted 01-18-2020 07:40

    Hi fellow engineers!

    I am tasked with improving a powder mixing system in our facility. Right now we convey the powder into a hopper (300-400# at a time), then we start a liquid circulation pump to/from the liquid storage tank, a ball valve is opened where the powder can be "sucked" into the liquid feed via vacuum (through an educator). 

    One issue we have is the liquid stream will sometimes back up into the hopper. This is likely an operator error but I can't blame them for a system that requires too much attention when we need them to multitask to get their job done! I was considering a check valve between the liquid line and the ball valve/hopper but I'm assuming that will ruin the vacuum effect of conveying the powder. Any thoughts or suggestions? The valve is set to automatically close if the weight in the hopper stops moving for >5 minutes or the total weight transferred has reached its set point.

    Also I was just reading the requirements for an eductor system to work properly and they recommend a continuous feed, whereas we are introducing a bulk of 300-400# all at once. I don't really want to change our whole system but I'm not sure if we can achieve a continuous feed since the hopper also serves as the scale to determine how much powder we are adding. 

    FYI the powder we are adding is fumed silica and the liquid is resin. 

    Any systems that work well and are relatively low cost to integrate into the kind of set up I have now? 

    Amber Manzi EIT
    Process engineer
    INEOS Composites
    Pittsburgh PA

  • 2.  RE: Educator system, powder and liquid mixing

    Posted 01-21-2020 14:55
    Hi Amber,
    If space is available between the hopper and the fluid pipe. you may consider adding a rotary valve.  The rpm of the rotary valve can be manipulated either manually or automatically, based on the rate of adding solids.
    Good luck,
    Sankar Raghavan

    Sankar Raghavan
    Eastman Professor of Practice
    University of Tennessee-Knoxville
    Knoxville TN