Orifice velocity/pressure - requirements for mixing powder into brine 1

[DevonH]

Hi I was wondering if anybody has any insight in figuring this out. This is the background: we want to mix and hydrate a starch powder into a salt saturated brine. The way we would like to do this is by using an orifice in a pipe with a powder induction hopper connected to the pipe right after the orifice (I know there might be better ways to do this but this is a quick setup). As the fluid flows through the orifice, this will create a vacuum, which will then pull the starch powder into the pipe and mix it into the brine. As the brine velocity increases, the ability of the starch to mix into the brine should be more favorable.

The problem is that we don’t know how to figure out how much pressure drop or liquid velocity is required in order to effectively shear this powder into the liquid. I’m guessing that as your pressure drop decreases, the suction of powder into the pipe is going to decrease as well, but I’m wondering if there is some sort of relationship that will give more details on this. One thing that is important to know as well is that as the starch powder comes in contact with brine, it will form fish eyes or clumps of starch powder that are hard to disperse or mix. Therefore it is desirable to obtain the best shear as possible in order to prevent these fish eyes from forming as soon as the powder contacts the brine.

Here is some more info on the setup:

Pipe inlet: 4”
Orifice size: to be determined
Brine specific gravity: 1.2
Brine viscosity: 2 cp
Final brine/starch solution viscosity: 200 cp
Desired Flowrate: 1000 gpm (this could be changed)
The pump we have currently can put 120 psi on the line, but this could be changed as well if required.

Thank you in advance for any help!

 

[m777182]

It seems from your description that you are going to use a sort of injector(or eductor or whatever) to suck the powder into the brine. To my experience the design will make troubles because there will be allways an area where powder will become partly moist but will be not splashed by liquid. At those points it will become sticky and will probably clog the flow. That was the system that was proposed to us to make a solution of flocculants but did not work.We used instead a system where powder was fed by a vibrating device into a cone. The cone had an injector(or ejector or eductor however you call it- sorry for my linguistic problems) at the bottom, but a part of the liquid was tangentialy introduced into the top of the cone, so that the wall of the cone was thoroughly wet providing a thick liquid layer that splashed powder particles easily down to the bottom into injector. The tangential inlet pipe was equiped with a hand valve to adjust the ratio of liquid to solid.Though very simple it worked more then 20 years without any problem.
m777182