Total tray

Fenske Equation Overall Minimum Total Trays with Total Condenser... 

For a condition of overall total trays allowance is to be made for feed tray effect, then add one more theoretical tray to the total. As demonstrated in the tabulation to follow, allowance should be made for the reboiler and condenser. 

Total trays = 7 (from diagram plus (1.71 - 1) = 7.7 theoretical, plus a reboUer or 8.7 including a reboiler. 

Generally, practice would be to select a colunm allotving a few extra trays, making column total trays = 45. 

Although Sutherland did not obtain an equation for total tray pressure drop, correlation at this time indicates that it follows the effective head concept of Hughmark. This is a limited evaluation because the data available did not indicate any clear liquid heights over about 0.75 in. 

Uneven vapor flow bubbling-up through the tray deck will promote vapor-liquid channeling. This sort of channeling accounts for many trays that fail to fractionate up to expectations. To understand the cause of this channeling, we will have to quantify total tray pressure drop. 

The sum of the dry tray pressure drop (APdry) plus the hydraulic tray pressure drop (APhyd) equals the total tray pressure drop (AP, ) ... 

An increase in reflux rate, assuming that the reboiler is on automatic temperature control, increases both the tray weir loading and the vapor velocity through the tray deck. This increases both the total tray pressure drop and the height of liquid in the tray s downcomer. Increasing reflux rates, with the reboiler on automatic temperature control, then will always push the tray closer to, or even beyond, the point of incipient flood. 

A correction also can be applied for the ratio of perforated and total tray areas. For the case of Example 14.10, the depth of coalesced layer is 1.6 in. according to this equation. 

TOWER INSIOE DIAM. (SEE NOTE 1) TOTAL TRAYS IN SECTION TRAY SPACING (INCHES) (SEE NOTE 1) NO. OF LIQUID PASSES (SEE NOTE I) MAX. Zip ( > /TRAY... 

Item No. or Service. . Tower diameter, I.D.., Tray spacing, inches. . Total trays in section. .. 

The total tray pressure drop HDC2 (inches of liquid) is calculated with preceding factors installed in Eq. (3.60). 

Residual pressure drop, i.e., total tray pressure drop less diy pressure drop less dear liquid height, in of liquid. 

WT = average width of tray normal to direction of liquid flow, ft, computed as average of total tray width at each row of caps... 

Calculated results for the solvent recovery column with nine total trays having the feed inlet on tray five are given in Table VII. The reboiler pressure has been taken as 14.7 psia. The pressure drop per tray has been set at 0.09 psi. A drop of 1.7 psi from the top tray to the con-... 

Total tray requirements for the three entrainers are compared in Figure 9. The least number of trays is required when n-pentane is used the most are required when diethyl ether is the entrainer. If benzene is used as entrainer at higher pressure than 14.7 psia, the corresponding curve in Figure 9 is shifted to the right, more trays being required. 

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