Orifice plate liquid distributor

Unfortunately, packing does not redistribute liquid, or internal reflux. Unless the initial reflux distribution is good, the liquid flow distribution through the entire packed bed will be poor. Figure 7.1 shows a common orifice plate liquid distributor. Vapor flows up through the large chimneys, and liquid drains through the smaller distribution holes in the tray deck. 

Let s further assume that the orifice plate distributor is 1 in out-of-level. This could easily happen in a 14-ft 0-in-ID tower. Figure 7.2 shows the results. The flow of internal reflux or liquid through the higher portion of the tray deck falls to zero. Worse yet, vapor starts to... 

Packed-tower efficiency and turndown are strongly dependent on the quality of initial liquid distribution. Uneven distribution may cause local variations in the liquid/gas ratio, localized pinch conditions, and reduced vapor-liquid contact. Figure 14 shows two common liquid distributor types, the ladder type (shown as the top distributor) and the orifice type (shown as the redistributor). The ladder type is a horizontal header of pipes, which are perforated on the underside. The orifice type is a flat perforated plate equipped with round or rectangular risers for gas passage. Other common types of distributors are a header equipped with spray nozzles (spray distributor) and a header of horizontal channels, with V notches cut in the vertical walls of the channels (notched-trough distributor). 

The main problem associated with falling film units is the need to distribute the liquid evenly to all tubes. All tubes must be wetted uniformly and this may require recirculation of the liquid unless the ratio of feed to evaporation is relatively high. Recirculation can only be accomplished by pumping. Distribution can be achieved with distributors for individual tubes, with orifice plates above the tubes and tubesheet, or by spraying. Updraft operation complicates the liquid distribution. 

Figure 8-5 shows the configuration at the top of the tower. The reflux was distributed by an orifice plate chimney type, pan liquid distributor. Vapor flowed up through the chimneys reflux was supposed to be evenly distributed by the /2-in. holes drilled in the pan across the top of the packed bed. To determine if the reflux was truly being equally distributed across the structured bed, I proceeded as follows ... 

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