Solution

Equation (7.39) is used to find the diameter of the tower. Iw should be 0.08 or above, but for stripping column it is very difficult to obtain such a high Iw value and therefore it will be attempted to select Iw = 0.04. It implies that a cross sectional area of 4 m2 should be used according to equation (7.39), giving L = 2500 kg/h/m2, provided that a is about 60 1/ m. It is the case for 4 inch raschig rings (see Table 7.4), which are chosen. The minimum ratio air to water is about 3000, which is selected. It will correspond to 30 000 m3 / h air or 36 000 kg / h. It gives a flow rate 9 000 kg/h/m2 or 7 500 m / h, corresponding to about 2 m / s, which is fully acceptable see Table 7.4.

The flooding point is found from equation (7.40), using Figure 7.14. Q is found to be:

which will give a Z value of about 5. As pL is 0,001 kg / m*s and dh3/2 is 0,01 (see Table 7.4), Iw is therefore 0.05 or slightly more than found above, which is acceptable.

HtG is found from equation (7.38), as the constants are found in Table 7.3:

Sc for air at 15° C can be found from the the viscosity of air (0.0648 kg / m • h ), the diffusion coefficient ( 0.0392 m2 / h) and the specific gravity (1.2 kg / m3) to be 1.37. HtG is now found from equation (7.38):

R is found from equation (7.42).

Henry's constant i found from (7.11) to be 0.69 bar. Therefore R = 1.66, which by use of Fig. 7.16 is translated to 3 transfer units, as the fraction 0.9 is removed.

The height of the tower is calculated to be 3.9* 3 = 11. 7 m.

Was this article helpful?

0 0
Waste Management And Control

Waste Management And Control

Get All The Support And Guidance You Need To Be A Success At Understanding Waste Management. This Book Is One Of The Most Valuable Resources In The World When It Comes To The Truth about Environment, Waste and Landfills.

Get My Free Ebook


Post a comment