DP across Filter Increasing

[all2win]

Hi Everyone,

I have this problem of DP across the filter increasing.We are using Sulphuric acid to dry the Chlorine in a Drying tower (Packed bottom and Tray top). In the downstream , we have a Dry Chlorine Filter( 5 no of candle filters) to remove the carry over sulphuric acid.Nowdays the pressure drop across the filter increases rapidly no matter what we do. Its supposed to last for 3 yrs minimum. but we are replacing it in 4 months.The quality of filter( glasswool) is never in doubt.

The presuure drop in the drying tower is normal.The problem is encontered after the plant capacity expansion(more cl2 gas flow).we have modified the drying tower also to accomodate the increase in flow.

ANy soultions u can think of?.

tnx

 

[Ashereng]

I am assuming you have already done the low hanging fruit, like:
- check that the current Cl2 gas flow is same as calculated for expansion
- the Cl2 stream analysis is the same as the basis for the expansion calculation
- the "porosity" of the glasswool is the same as used in the expansion calculations
- the glasswool is the same chemically and physically as used in the expansion calculations

If nothing has changed, then, the DP should be the same. Usually, it is something that has changed that no one remembers, or thinks of, that is causing the problem.

One way is a systematic re-examination of all the numbers.

Hope this jogs something in your memory. Good Luck.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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[joerd]

Do you mean that you get more sulphuric acid carryover than before, or is something else fouling the filter?

Cheers,
Joerd

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[all2win]

Yes. The sulphuric acid carryover is more now .We tried to bypass one tray (bubble cap) in Drying tower.Still it doesnt work.

 

[joerd]

Probably the gas velocity in the tower is so high that a lot of fine droplets are entrained. Usually the column diameter is sized such that the maximum velocity as calculated by the Souders-Brown equation is not exceeded. The equation is:
[tt]V <= K*sqrt((liq.density - vap.density)/vap.density)[/tt]
The design K factor is about 0.15 ft/s if no mist eliminator is used, about 0.25 ft/s for a wiremesh mist eliminator, and higher for special designs.
So, to reduce carryover, the best solution for an existing column is to install/improve a mist eliminator. You can work with Koch/Otto York or one of their competitors to see what would be best in your application.

Cheers,
Joerd

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