Trays, stripping

Bourbon Distillation. The basic distiUation system for the production of bourbon and other straight whiskeys consists of a beer stiU and a beer heater, thumper, or doubler (Fig. 4). The whiskey stiU consists of between 14 and 21 stripping trays. The upper portion of the stiU is fitted with either a bubble cap section or a section packed with copper rings to enhance the removal of unwanted flavors and ethyl carbamate precursors. The reduction of carbamate precursors requites strict adherence to a cleaning protocol with a 5% caustic solution as often as twice a week. 

L - Liquid from bottom stripping tray = Liquid to top stripping tray (j)a = 1 - Ea, fraction not absorbed (jts = 1 - E5, fraction not stripped Vo = Vapor to bottom stripping tray... 

PRESS OPEN MOULDING EJECTED FORKED STRIPPING TRAY IN... 

Tray efficiency is calculated as previously demonstrated and will not be repeated, except that normally stripping tray efficiencies run lower than rectification efficiencies. For ammonia-water stripping such as this example most over-all efficiencies run 50-60%. 

Rehydrated strips are then placed onto a custom-made cooling plate or a commercially available strip tray of a horizontal-type electrophoresis apparatus. The strip tray is fitted with bars holding the electrodes. The bars fitted with sample cup onto the tray allow easy application of the... 

We can use this idea to calculate the percent of diesel oil that would actually vaporize across the stripping trays in the stripping tower. Let s assume the following thermal properties for a typical hydrocarbon mixture of diesel and gasoline ... 

High liquid levels in the bottom of the stripper will also reduce stripping efficiency. A liquid level above the steam inlet will cause the stripping trays to flood. Flooding vastly decreases tray efficiency, and hence stripping efficiency. 

The bottom product from the solvent recovery column is ethylene glycol with about 41 ppm of water, mole basis. By changing the number of stripping trays in the solvent recovery column, this water content can readily be decreased or increased. 

Particularly when the number of trays is small, the location of the feed tray has a marked effect on the separation in the column. An estimate of the optimum location can be made with the Under-wood-Fenske equation (13.116), by applying it twice, between the overhead and the feed and between the feed and the bottoms. The ratio of the numbers of rectifying A/, and stripping trays is... 

The effect of liquid leakage from the tray is more important for stripping trays than for rectifying trays. For stripping trays, liquid leakage carries more volatile components toward the draw point for the less volatile product, thus reducing the effectiveness of the stripper. Fortunately, for most bubble cap trays, there is no tray leakage of consequence. 

In a multi-component system, the optimum feed location depends on the light and heavy key components and their desired concentrations in the products. A feed location that is optimum for one set of specifications may be a poor selection for another. The number of rectifying trays must be sufficient to remove from the overhead as much of the components heavier than the light key as is needed to meet the required overhead composition. Similarly, the number of stripping trays must be sufficient to strip from the bottoms as much of the components lighter than the heavy key as is needed to meet the required bottoms composition. 

In selecting the feed tray for the main feed, it is desirable to maximize the number of stripping trays in order to minimize the reboiler duty required to achieve the specified methane stripping. However, the feed tray should not be too high. If it is, an excessive amount of ethane is lost in the overhead because of an insufficient number of rectifying trays. Table 9.2 shows reboiler duty requirements and ethane recoveries in the bottoms for different feed tray locations. The methane mole fraction in the bottoms is fixed in all cases at 0.001. The results indicate that the optimum feed tray is the third tray from the top. 

Measurement of internals is particularly important for those dimensions that change from one section of the column to another. Assembly errors can often result in internals being interchanged. If these are not detected, severe hydraulic problems can arise. One experience has been described (295) in which the rectifying trays were interchanged with the stripping trays. 

Vapor flow in the bottom of the stripping column below the lowest stripping tray, or... 

The crude rate was then increased by 3,000 B/SD to 195,000 B/SD. More importantly, the FCCU feed was no longer black. 1 asked the operators how long the gas oil had been black. One of the older men responded that the problem had started after a turnaround eight years ago. It was during this turnaround that the bottom of the tower had been modified. The three stripping trays had been replaced to increase capacity. Ever since, he concluded, the FCCU feed had been black. 

Two years later, I was working for ARCO on a vacuum tower problem in Ferndale, Washington, when my colleague at AXECO called again. He related that the tower on No. 2 crude unit had been opened for inspection and that they wanted me to fly down to their plant to inspect the stripping trays. Figure 1-2 shows what 1 found when I entered the column. 

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