## Please help! HTU of random packing saddle #1

## Please help! HTU of random packing saddle #1

(OP)

Hi Guys,

I need your help on absorption HTU. Please refer to attached. It's related to base system HTU from KGa curve. How do I get HTU using formula HTU= G/ Kga?

Below is the test conditions:

Bed height 3.05m

Liquid concentration: 4% NaOH

Conversion to carbonate:25%

Inlet CO2 concentration: 1%

Gas rate: 900 lb/hr ft3 atm, divide by air density 29 lb/lbmol= 31 lbmol/hr ft3 m

Pressure: 1 am

Assumptions:

1) This is chemical absorption so consider gas phrase only.

2) Assume at liquid rate 8 gpm/ft2 using Saddle #1. The Kga value is ~ 3 lbmol/hr ft3 atm

3) Using HTU= G/Kga= 31/3= 10.3 ft!

4) This HTU value is very high and not reasonable.

Thanks for attention and please help !

I need your help on absorption HTU. Please refer to attached. It's related to base system HTU from KGa curve. How do I get HTU using formula HTU= G/ Kga?

Below is the test conditions:

Bed height 3.05m

Liquid concentration: 4% NaOH

Conversion to carbonate:25%

Inlet CO2 concentration: 1%

Gas rate: 900 lb/hr ft3 atm, divide by air density 29 lb/lbmol= 31 lbmol/hr ft3 m

Pressure: 1 am

Assumptions:

1) This is chemical absorption so consider gas phrase only.

2) Assume at liquid rate 8 gpm/ft2 using Saddle #1. The Kga value is ~ 3 lbmol/hr ft3 atm

3) Using HTU= G/Kga= 31/3= 10.3 ft!

4) This HTU value is very high and not reasonable.

Thanks for attention and please help !

## RE: Please help! HTU of random packing saddle #1

For dilute concentrations of the solute in the gas ( which is the case here), I dont see any error in your calculation.

## RE: Please help! HTU of random packing saddle #1

## RE: Please help! HTU of random packing saddle #1

1 atm = 10.3326 m H20 column.

Good Luck,

Latexman

Pats' Pub's Proprietor

## RE: Please help! HTU of random packing saddle #1

Gas rate: 900 lb/hr ft3 atm, divide by air density [u]29 lb/lbmol= 31 lbmol/hr ft3 atm

Pressure: 1 atm

2) Assume at liquid rate 8 gpm/ft2 using Saddle #1. The Kga value is ~ 3 lbmol/hr ft3 atm

3) Using HTU= G/Kga= 31/3= 10.3 ft!

## RE: Please help! HTU of random packing saddle #1

Stronger chemical reaction than this case leads to higher Kga which translates to lower Hog or HTU.

Also these reported values are for overall Kga, so no need to add a correction factor for liquid phase resistance ie Hg or HTU = Gm/Kga.

## RE: Please help! HTU of random packing saddle #1

## RE: Please help! HTU of random packing saddle #1

So these graphs for Hog you have posted later are the wrong comparison basis, since it is not for the CO2-NaOH system at the same operating conditions as that for the first graph posted.

There is some abnormality in the Norton Kga numbers (or so it seems to me too) for this 900lb/hr ft2 gas rate for 25mm Intalox ceramic packing in this CO2 - NaOH system. The Kga value published is almost the same as that for 500lb/hr/ft2 gas rate. Extrapolating from the 500lb/hr/ft2 data, the Kga at 900lb/hr/ft2 ought to be approx ((900/500)^0.7) * 56 = 84kgmoles/hrm3 at 1 atm. The basis for this approximate numerical extrapolation is found in Perry. But the published value is only 59kgmoles/hr.m3.atm. The authors in Perry have commented on this anomaly and have not offered an explanation why this is the case. You may query Norton why this is the case.