akbarnejad
Harmless
Posts: 2
Registered: 11-11-2010
Member Is Offline
Mood: No Mood
|
|
Manufacturing of sodium sulfate from “salt cake”
Manufacturing of sodium sulfate from “salt cake”
The Mannheim process is a well known process for manufacturing of sodium sulfate from sulfuric acid and salt as:
NaCl + H2SO4 NaHSO4 + HCl
NaHSO4+ NaCl Na2SO4+HCl
As the second reaction is done in very elevated temperature, in some factories that HCl is the main product, they do not raise the temperate as needed
to complete the second reaction because of high corrosion problems. The solid from these furnaces is about 50% Na2SO4 and 50% NaHSO4 known as salt
cake.
I tried to put this salt cake in direct fire to convert the NaHSO4 to Na2SO4 as follow:
2 NaHSO4 Na2S2O7 +H20
Na2S2O7 Na2SO4+SO3
The problem is that the SO3 does not evolve from the salt cake unless severe mixing which is not practical in direct fire system and the second
problem is the absorption of hot SO3 mixed with hot fuel gas. The gas is very pollutant and absorption or distillation is very hard because the high
temperature.
I tried heating salt cake for 5 hours in 700 C but the sodium sulfate content has risen just from 50% to 87%.
Can anyone help me with this problem? Is there any other way to recover sodium sulfate from salt cake?
Thank you
|
|
|
hissingnoise
International Hazard
Posts: 3940
Registered: 26-12-2002
Member Is Offline
Mood: Pulverulescent!
|
|
Check both salt's solubility to see if fractional crystallisation might work?
|
|
|
bbartlog
International Hazard
Posts: 1139
Registered: 27-8-2009
Location: Unmoored in time
Member Is Offline
Mood: No Mood
|
|
Seems likely that the problem is mechanical, in the sense that the gas products can't escape the system easily enough. Maybe bubble through a carrier
gas (even air could work) to help the SO3 to the surface of the melt? There are other solutions I can think of (including the obvious one of
neutralizing with NaOH) but I assume you're looking to do this in the most economical way possible, not use sacks of other feedstocks to achieve your
goal...
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Possibly, the bisulphate is considerably more soluble than the sulphate. If the bisuphate is the minority component, circumstances that favour
sulphate crystallising and bisulphate staying in the mother liquor arise. At 87 % sulphate that should be feasible but you'll always lose quite a bit
of sulphate to the liquor...
|
|
|
mr.crow
National Hazard
Posts: 884
Registered: 9-9-2009
Location: Canada
Member Is Offline
Mood: 0xFF
|
|
Why? Sodium sulfate is worthless and easy to make
Double, double toil and trouble; Fire burn, and caldron bubble
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
True but if I had acess to fairly large amounts of this salt cake for free, I'd want to recover the chemicals in it too...
|
|
|
hissingnoise
International Hazard
Posts: 3940
Registered: 26-12-2002
Member Is Offline
Mood: Pulverulescent!
|
|
I got the impression that the bisulphate was the salt of interest - for its decomposition products.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
