Packed towers loading point

This is only slighdy lower than good practice, but because the operating point is at the lower loading point, continue with this selection. A smaller diameter tower might calculate to be a better choice. However, extreme caution must be used in designing too close to limits with packed towers. Very litde of the data are exact, and often the range is not known. 

The suitable control range of differential pressure controllers may be narrow, especially with valve trays (Fig. 19.126). In the valvethrottling range of a valve tray, and below the weep point of a sieve tray, pressure drop may be insensitive to vapor loads. Differential pressure control may therefore be difficult to apply imder turned-down conditions. Packed towers are not prone to this limitation (44), because pressure drop tends to be sensitive to vapor load over the entire operating range (Fig. 14.3). 

Buchanan,J.E. "Hold-up in irrigated ring packed towers below the loading point". Ind.Engng.Chem.Fund. 6 (1967) 400. 

What is the maximum capacity of this absorber if the effluent liquid contains 0.45 mol C02/mol DEA The tower will be packed with 2 Hy-Pak packing, and because of the foaming tendency of this system, the pressure drop is not to exceed 0.25 in. H20/ft at the point of maximum loading. 

---