Using low pressure compressed air to filter process liquids from process solids in plastic vessel Answered
This is my first post here, and after many trails proving a concept method i am ready to scale up, but require a little guidance for safety purposes. This process is happening at a lab scale with the need to make a jump form 10 gal to 60 gallon per batch.
We are currently chemically processing concrete construction fines (roughly a gradation of sand and fine particles between 20 micron & 5 mm) with a water-based chemical. We are using a standard concrete mixer to process, and then filter the solids from the liquids using #50 mesh bags. Then we let the ultra-fines settle and decant as much of the remaining liquid as possible. With this process both the liquids AND the solids are of great value, so any valuable chemical in the liquids is important to get out of the solids with as much efficiency as possible.
The valuable chemical in the liquid easily volatilizes and is fairly corrosive, so there is a need to keep everything contained and in CHEAP non-corrosive materials as much as possible. From this i was thinking doing batches in 55 gallon plastic top sealing drums and using a drum mixing machine to stand-in for the concrete mix. This way everything is sealed and can be stored until separation.
Then i started thinking about filtration... we use kegs around the lab to process certain chemicals and started to think about putting a filter on the end of the stand pipe inside a corney keg and using 2 psi of air to force the liquid out form the solid. At first i used #100 poly mesh and wrapped the liquid outlet and though it took a while i was able to get a high degree of the liquid out, more than we ever have in gravity method. So then i made a filter using 1 micron mesh and wrapped it in #100 mesh and through a mass of very fine particles mixed with water. Again, it worked wonderfully, though i had to increase pressure to 20 psi to force more water out of the smaller fines.
Now i have started testing on plastic vessels, YES i know this can be dangerous, however i am working at very low pressures. I have a 7 gallon screw-top lid bucket (not the pop-on kind) and have mimicked a keg setup to see if i can force water out of an exit pipe, and it worked. I am about to make the jump of trying to process actual solid/liquid mixture with a similar filtered outlet.
Am i going in a completely wrong direction?
Can this be scaled to a 55 gallon drum under 5 psi or similar low pressure?
Because i am allowing an outlet (liquid), is this less dangerous than actually pressuring a drum with no outlet (i realize the filter itself with create back pressure)?
Are there pieces of process equipment that are made of cheap non-corrosive materials, can be used on a drum mixer, AND can be pressurized moderatly?