Tower Diameter

The tower diameter depends on the vapor and liquid flow rates and their properties up and down the tower. The tower diameter is computed to avoid flooding, where the liquid begins to fill the tower and leave with the vapor because it cannot flow downward at the required rate. 

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The number of variables that are known to influence the rate of extraction is exceedingly large, and includes at least the following Size, shape, and material of packing Tower diameter Packing depth... 

FIG. 15 53 Effect of pulsing on extraction in a packed column methyl isobutyl ketone-acetic acid-water (continuous). Tower diameter = 1.58 in, 27-in depth of V4-in Raschig rings. = Vc = 7.5 to 10. To convert inches to centimeters, multiply by 2.54. [Data of Chanhy, von Berg, and Wiegandt, Ind. Eng. Chem., 47, 1153 (1.9.55), with permission. ... 

Calculation/Procedure for Ballast Tray Minimum Tower Diameter... 

Using and GPM (column liquid loading in gallons per minute), obtain approximate tower diameter for calculating flow path length. Use... 

This is the author s correlation of a nomograph in the Glitsch Manual. It gives results within 5% of the nomograph for diameters 4 feet or greater and within 15% for smaller diameters. This is adequate for this first approximation of tower diameter. It applies for... 

ATM = Minimum column cross-sectional area, tV. Further detailed design calculations may result in a change in tower diameter. 

ADM = Minimum downcomer area, fT ATM = Minimum column cross-sectional area, fr CAF = Vapor capacity factor CAFo = Flood capacity factor at zero liquid load CFS = Vapor rate, actual ftVsec DT = Tower diameter, ft DTA = Approximate tower diameter, ft FF == Flood factor or design percent of flood, fractional FPL = Tray flow path length, in. 

For checking designs one can roughly relate tower diameter to reboiler duty as follows ... 

If the tower diameter is <3 ft use a packed tower instead of plates... 

Reduetion in top reflux permits a reduction in the tower diameter in the section above the pump-around, thereby reducing investment. However, the reduction in reflux requires the addition of more fractionating plates to maintain the same separation efficiency. 

Random packing has traditionally been used in small diameter ( t in.) towers. This is because it is easier and le.ss expensive to pack t small diameter towers. However, random packed beds are prone to c neling and have poor turndown characteristics when compared i trays. For these reasons, trays were preferred for tower diameters greater than 20 in. In recent years an improved understanding of the impact of... 

However, low velocities require towers with large cross-sectional areas to handle a given gas flow, and allow the wet gas to channel through the desiccant bed and not be properly dehydrated. In selecting the design velocity therefore, a compromise must be made between the tower diameter and the maximum use of the desiccant. Figure 8-22 shows a maximum design velocity. Smaller velocities may be required due to pressure drop considerations. 

Once the operating conditions are established for a tower, its diameter and height can be chosen using data available from tray and packing manufacturers. The details of tower diameter selection, tray spacing, and internal design are beyond the scope of this text. 

Determine the tower diameter based on the flows of (6) above. See Chapter 9, this volume for packed tower design. 

These downcomers are suggested only where liquid flow is relatively small for the required tower diameter, allowing a maximum of space for bubble caps. 

Tower Diameter, Ft Seal, Outlet Weir Hei t minus Distance Downcomer OH Tkay Floor, In. 

The tower diameter may be calculated for first approximation by the Souders-Brown method however, this has been found to be conservative, since it is based on no liquid entrainment between trays. Actually, some entrainment can be tolerated at negligible loss in efficiency or capacity. 

In general, a better first approximation and often a more economical tower diameter is determined using Figure 8-121 [33],... 

Choose tower diameter that will give the desired approach to flooding. Or, if dealing with an existing tower, calculate the approach to flooding. 

The design velocity for selection of the holes also sets the minimum tower diameter. To take advantage of as much flexibility in operation as possible throughout the expected operating range, the following points should be considered in setting this velocity. 

A tower diameter is selected based on Souders-Brown (20-50 percent conservative, usually) or Hunt s relation, Equation 8-250. 

Estimated Tower Diameter Souders-Brown method W = C[p,(pi.-pv)]i/2... 

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