Tower flooding

There are dozens of other types of reboilers, but these four represent the majority of applications. Regardless of the type of reboiler used, the following statement is correct—almost as many towers flood because of reboiler problems as because of tray problems. 

As a result, the tower flooded above the holddown plate. To fix this problem, the packing holddown was dropped 15 in below the chimney, orifice plate, distributor. As a result, the tower fractionated properly. 

Packed tower Flooding velocity is obtained with Figure 14.17. For 1 in. metal pall rings,... 

Packed Tower Flooding velocity is obtained using Equations 14.42-14.43. For one inch metal Pall rings,... 

Above the limiting liquid load, the vapor is entrained downward in the downcomer, the tray liquid level builds up, and the liquid becomes entrained into the vapor stream. The tower floods with the liquid. 

Prediction. Prediction methods for packed tower flooding are available in most standard distillation texts (e.g., 51, 193, 257, 319, 386, 404, 409) and in packing manufacturers literature. 

Refinery Vaporchctkingafalonglinefromcol-umn to rdboiler caused premature tower flooding. To solve the problem, the draw pan was converted to a degassing pan and the line was sloped and vented. As for 703. 

Premature tower flooding occurred when level in the bottom of the column rose above rdxnler return nozzle and badqnessured a uniquely designed bottom surge drum. Level rose either because v xrr was present in liquid line to beater or liquid was entrained in drum vapor. Provisions which lowered surge dr level solved the problem. 

Perforated-plate Towers. Flooding of these towers may occur either because of inability to maintain an interface at the end of the tower or because of thickening of the layers of dispersed phase on the plates. Tend-... 

Improperly operating level controls can cause tower flooding. In the example just discussed, the level controller is the type that uses a separate float chamber, with displacers to sense the liquid level in the chamber (Fig. 12-8). These types of controllers can sense, incorrect level. 

For most once-through and many circulating thermosyphon reboilers (see Figs. 18-1 and 18-2), a high liquid level covering the reboiler vapor return nozzle will retard thermosyphon circulation and cause a precipitous loss in reboiler duty, instead of tower flooding. 

The plugged top tray will prevent the reflux from cascading down to the lower trays. The liquid reflux will just overflow into the condensers and circulate back to the reflux drum. The tip-off to this problem is that neither the reboiler duty nor the bottoms temperature is affected in the normal way by raising reflux. The tower s heat balance appears as if the reflux rate had never been increased. This is not much different from the signs of normal tower flooding, except that the AP on all but the top tray is not excessive. 

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