hygroscopic properties of sodium phosphates

[fvincent]

I am concerned with the operation of a bag filter designed to remove dry sodium phosphates from dryer exhaust gases.
Exit temperature is from 120 to 140oC and water dew point is 65oC. As far as I know the presence of sodium phosphates (specially NaH2PO4 and Na2HPO4) which are very hygroscopic can lead to a high water absoption on the bags cake under certain conditions.

Do you think that under the temperature and humidity above there will be intense absorption of water by the salts

How can I be sure that this will not bring problems?

Should I select a hygrophobic fabric for the bags?
Keep the filter heated during standstill operation?
Insulate the filter?

Is that all enough to avoid filter plugging?

Thanks a lot

fvincent

 

[m777182]

In a similar situation we are using hygrophobic fabric for the bags and the air for the backflush of the bags is heated mainly because by the very rapid expansion it is cooled to cause condensation.
m777182

 

[fvincent]

Thanks m777182

Can you tell me the gas temperature and the fabric material you have selected?

Is the filter a pulse jet? So you mean the compressed air is heated? How and how much?

Is there any heating device in the hopper?


Thnaks again


fvincent

 

[m777182]

The fabric material is polyester with hydrophobic treatment. The incoming gas/dust temperature to the filter is the temperature of surrounding air: -15 in winter, +35oC during summer. Compressed air is heated by electric heaters to 70...110oC. Filter is thermaly insulated.The backwash is a strong pressure pulse of compressed air. There is no heating device in the silo but occasionally a small flow of dry air from the bottom of the silo is switched on- when it is very warm and humid.
m777182