scrubber tower sizing

[nuig]

Not having Perry's handbook, can anyone give me the basic equations to size a gas liquid absorption scrubber tower?
All gas properties are known and the constituent to be removed is H2S.

Thanking you in advance....

 

[PeterAB]

Sorry nuig, but looking at the lack of replies you got, silence in speaking volumes. Packing / scrubber manufacturers measure and hoard the information required to answer your question. Your best bet is to get and compare a few quotes from scrubber manufacturers.

 

[nuig]

PeterAB,

Thanks for the reply, but had figured as much. But like to have an idea myself of the calculations if possible.
Quotes are coming as we speak...

 

[PeterAB]

Nuig,
If all you want is an "idea" of the calculations, I can summarize that the height of the tower tends to be proportional to the logarithm of (inlet concentration/outlet concentration), while the cross-sectional area will be proportional to the quantity (volume per unit time) of the gas treated. Actual numbers will be specific to the packing used.

 

[nuig]

PeterAB,

That is usually the case with dilute gases and fast chemical reaction in the absorption?
My application is biogas, which is formed from the biological breakdown of wastewater sludge.
I'm under the impression that biogas isn't a dilute gas, having a composition of 60% CH4, 38% CO2 and ~2% H2S?
(35deg C, 1 atm)

 

[sewerguy]

Packing vendors give away the correlations you are looking for, Koch and Glitsch had good old manuals as well as a recent favorite - Jaeger. Ask these sizing techniques will give you a good ballpark diameter based on gas and liquid flows.

A little leg work will get you in the right ball park, also get you to the right range of L/G ratios.

 

[kenvlach]

I agree with above comments, scrubber mfrs. guard their data (unless you are a customer), but you should be able to get help from the packing media mfrs.
Maybe have someone request a Scrubber Tech Bulletin for you from Harrington:

http://www.harringtonplastics.com/Catalog/catalog12pdf_files/Section14/14_3.pdf

P.S. Try shopping for reference books like Perry's on eBay, Half.com and addAll

http://www.addall.com/Used/

 

[PeterAB]

An important difference between dilute and concentrated gas is that for concentrated gases, heat effects can become significant. In your application, my prime concern would be the high CO2 concentration consuming the base chemical intended for H2S absorption.
You may want to check with amine manufacturers like Dow for products to preferentially absorb H2S over CO2.
Note also that CO2 absorption is a slower process than H2S absorption. Hence a scrubber that minimizes liquid-gas contact time, such as a spray scrubber, will also minimize chemical consumed by CO2.

 

[nuig]

PeterAB,

A scrubber manufacturer pointed out that fact about the CO2 to me already actually.
He suggested using a selective H2S scrubbing liquid with a tradename of Sulftrol.

I was going to go with liquid distribution via spray nozzles all along, now I have another good reason to!

Thanks to all with all your posts, you've all certainly helped a great deal.