Deodorization semicontinuous

Semiconductor surfaces, 9 730-731 Semiconductor technology, 19 127 Semiconductor transport, 22 237-239 Semiconductor-vacuum interface, 22 241 Semicontinuous deodorizer, 10 815 Semicontinuous dyeing, 9 211-213 Semicontinuous ion-exchange systems, 14 403... 

Deodoiization or steam stripping is used to remove objectionable odors resulting from peroxides, aldehydes, and ketones as well as characteristic rice oil odors and flavors (12). The oil is heated to 220-250°C under 3-5-mm Hg vacuum. Semicontinuous deodorizer units are the most common types used. Other designs have been evaluated (43). After deodorization, the oil is cooled to 60°C and filtered. Storage of deodorized rice ban oil is the same as for other oils. 

Semicontinuous deodorization with scrub cooler, barometric condenser with atmospheric cooling tower. 

Figure 12. Indirect heat recovery systems used in semicontinuous deodorizers (thermosiphon systems) (De Smet). LP low-pressure steam HP high-pressure steam.

Semicontinuous deodorizers are basically batch systems designed for larger capacities. Their main application is in plants with frequent feedstock changes of oils sensitive to cross contamination. In most designs, a batch of oil is transferred into... 

Figure 21. Semicontinuous deodorizer for frequent stock changes (Multistock-De Smet).

Today, even for small capacity plants (10-50 TPD), semicontinuous deodorizers are clearly more suitable than conventional batch deodorizers. The shorter hold-up time in a semicontinuous deodorizer is a good argument in its favor, even in cases when small capacities with very frequent feedstock changes are required. Compared with continuous systems, the main advantages of semicontinuous deodoriza-tion are its shorter time for feedstock change as well as its much lower cross contamination. Heat recovery is, however, less efficient than in continuous operation. 

Fig. 4. Votator semicontinuous deodorizing plant (with heat recovery). Courtesy of Chemetron Process Equipment, Inc., Louisville, Kentucky.

Most suppliers of semicontinuous deodorizing processes also offer process versions suitable for continuous operation. In addition, there are processes such as that by Wurster and Sanger (Mattil, 1964) designed for continuous operation only. 

The temperature of the oii during steaming is the most critical process parameter during deodorization, and if the temperature falls below 340°F (170°C) very little deodorization actually occurs. For batch deodorization the typical operating temperature ranges from 360 to 465°F (180-240°C). For semicontinuous deodorizers... 

Figure 3 Conventional vertical semicontinuous deodorizer (Girdler type).

Figure 4 Horizontal semicontinuous deodorizer (De Smet MTD type).

There are two basic configurations of continuous deodorizers. The first, shown in Figure 5, is very similar to the design of the semicontinuous units with a number of trays or compartments in which the oil is deodorized. As distinct from the semicontinuous deodorizers, the flow of oil through the unit is continuous, with the oil retention time on each tray or in each compartment simply being a function of the volume of the tray or compartment. Valve or sieve trays are most commonly employed in this deodorizer configuration. Typically tray or compartment residence times are comparable with those of semicontinuous units. 

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