Trays selecting

From values of Sj calculated (=Sg), read Ej, values from Figure 8-58 at the number of theoretical trays assumed in Step 2. Note that the Sg corresponds to the number of trays selected, hence will give a value for performance of the system under these particular conditions. 

Only tray-type columns were considered because of the difficulty of incorporating an effective cooling circuit into a packed column. Sieve trays (as opposed to bubble or valve-type trays) were preferred because of the ease of installing cooling coils and also their low unit cost. Details of tray selection are included in Appendix G.l. 

These dynamic simulations confirm that the control tray selection criteria discussed earlier yield reasonably effective control systems. 

For new tower design, without overriding process factors, the cheapest overall system (tower, foundation, internals) is normally a sieve or a valve tray. Both have essentially the same capacity. The driving force behind valve tray selection is the flexibility benefit of the valve tray at little additional cost. However, for larger diameters and higher liquid rates, the flexibility advantage of the valve tray is more illusory than factual.f ... 

In this chapter, methods are presented for determining capacity (or column diameter) and efficiency of some commonly used devices for vapor-liquid and liquid-liquid contacting. Emphasis is placed on approximate methods that are suitable for preliminary process design. Tray selection, sizing, and cost estimation of separation equipment are usually finalized after discussions with equipment vendors. 

Temperature Control Tray Selection. There are a number of methods for selecting the best tray for temperature control. The easiest and most frequently used is to simply look at the temperature profile and select a tray where temperamres are changing significantly from tray-to-tray. 

All level controllers are proportional only with a gain of 2. The trays selected for temperature control are located near the bottom of the columns, where the temperatures are changing the most rapidly from tray to tray (see Figure 7.9). A 1-min deadtime is inserted in each temperature loop. Relay-feedback tests and Tyreus-Luyben tuning are used to obtaining... 

A function (f) based on the bubble points of the light and heavy key components (Tuc and Thk) would also be worth considering if other approaches fail. The bubble points (at normal operating pressure) are derived from the Antoine Equation. For the HK inferential Tis the temperature on the tray selected in the upper section of the column. 

For the LA), inferential Lis the temperature on the tray selected in the lower section of the column. 

Stable column temperature control, from the tray selected by the foregoing static considerations, depends on the dynamic measuring lag or response of the tray temperature with respect to the manipulated energy source used to control the temperature. Based on experimental tests, the following observations are cited for use as guides ... 

M. A. Perazella and K. Tray, Selective cyclooxygenase-2 inhibitors a pattern of nephrotoxicity similar to traditional nonsteroidal anti-inflammatory drugs. Am. J. Med., 2001, 111, 64-67. 

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