3 replies to this topic

[anina]

Hi,

Can you tell me please how to choose the stripping factor for column stripping of water by air.

Thank you

[Zauberberg]

I assume you are already familiar with Kremser-Brown equation, and the stripping factor defined as S = K*V/L. I also believe you are familiar with each term in this equation.

Since you can essentially describe your system as highly diluted and isothermal, Kremser-Brown equation should work. By changing the Stripping Factor value, the number of theoretical plates required will change as well, so I would suggest you to develop a simple spreadsheet and evaluate number of theoretical plates, and stripping air flow for several cases (the quality of air is known), with the Stripping Factor ranging from 1.15 to 1.50 (most common figures). Somewhere in between is the optimum design, probably much closer to the 1.15 figure.

Best regards,

[anina]

I assume you are already familiar with Kremser-Brown equation, and the stripping factor defined as S = K*V/L. I also believe you are familiar with each term in this equation.

Since you can essentially describe your system as highly diluted and isothermal, Kremser-Brown equation should work. By changing the Stripping Factor value, the number of theoretical plates required will change as well, so I would suggest you to develop a simple spreadsheet and evaluate number of theoretical plates, and stripping air flow for several cases (the quality of air is known), with the Stripping Factor ranging from 1.15 to 1.50 (most common figures). Somewhere in between is the optimum design, probably much closer to the 1.15 figure.

Best regards,

Hi Zauberberg

Thank you very much for your explanations, in fact I'm working with random packing not plates, and the spreadsheet is exactly what I'm doing, so can I use the factor between 1.15 and 1.50 for my calculations even for towers with random packing or is there other Values. I found in various documents that the stripping factor is generaly between 12 and 15 but for me it's too high!! and in others between 2.5 and 3 so I'm lost, Can you guide me please and can you tell me what equation do you use for the calculation of the air flow because I find diffrent equations for this too.

[Zauberberg]

Anina,

I have to correct myself for what was written in the previous post, as the stripping factor (defined as S = K*V/L) can have a wide range of values, depending on the system in question, while I was referring (as many resources do) to the stripping factor which is the ratio of stripping air flow at given number of theoretical plates, and the stripping air flow at infinite number of theoretical plates in the stripper. The value between 15-50% higher than the minimum theoretical value, is probably the optimum one. I apologize if I have confused you with my previous post.

As for the stripping factor defined by Kremser-Brown equation, you can try to use averaged K-value and Henry's Law since (if) the system is highly diluted and isothermal. Depending on the air flow you use for stripping, the stripping factor will vary as well: higher air flow results in higher stripping factor and less number of plates required, but probably bigger diameter tower, and vice versa.

Jaeger give some interesting guidelines with respect to Air Stripping (attached below).

Attached Files

•  Air Stripping.pdf   819.54KB   131 downloads