recovery of GLAUBERS salt from waste water

[kam2002]

I have to recover GLAUBERS salt from a textile waste containg 3.5 percentage Na2So4. The waste water generation rate is 1000liters per hour. I have to design the waste treatment system for zero effluent discharge. Steam is avialable at 8 barg pressure and cooling water supply is available at 20 degree celcius. chilled water is not available will it be economical to conduct the crystallaization process under vaccum or to generate chilled water and use it for crystallaization process. Up to what concentration the feed shall be concentrated before entering the crystallaization step. kindly send your valuable suggestions.

 

[saxon]

kam2002, You might want to take a look at ultrafilitration coupled to spary/flash dryer. Run the waste water to a waste concentration tank, pump through an ultrafilter, recycle the UF permeate back to the front end of the process for reuse. The UF concentrate is returned to the waste concentrate tank. From this point the concentrated waste is pumped to the spray/flash dryer where the salt and liquid are separated.

Now mind you, this is an experimental process requiring lab bench study for feasibility and then a scale up to operating conditions. According to my conversion you're only dealing with flow rate of 4.4 gpm so the the scale up won't be massive.

Hope this helps.
saxon

 

[mohunta]

The solution is very dilute. You have to concentrate it using RO or by vacuum evaporation. When a saturated soluttion is formed. Cool it 20 C. glauber salt will crystallize out as na2so4.1o.h2o. Heat the salt. It will melt and anhydrous salt will precipitate. centrifuge and dry. Recycle the mother liq. The permeate from RO plant can be used as good quality water.

 

[mjh127]

Electrodialysis may be an alternative to RO or evaporation. As with RO you will end up with a concentrate stream and an essentially salt-free diluate stream. Electrodialysis may be economically favorable depending on the price of electricity. You will have to do some long term experiments in order to find out if the membranes (both in RO and ED) will be blocked due to fouling.