Orifice mixers

Agitated Line Mixer See Fig. 18-32. This device, which combines the features of orifice mixers and agitators, is used extensively in treating petroleum and vegetable oils. It is available in sizes to fit V2- to 10-in pipe. The device of Fig. 18-33, with two impellers in separate stages, is available in sizes to fit 4- to 20-in pipe. 

The reaction mixture is pumped away from the reactor with an alkymer transfer pump, through a steam heater and an orifice mixer into the alkymer wash and surge tank. Dilute caustic solution is recirculated from the a.w.s. tank through the orifice mixer. Makeup of caustic is from a dilute caustic storage tank. Spent caustic is intermittently drained off to the sewer. The a.w.s. tank has an internal weir. The caustic solution settles and is removed at the left of the weir the alkymer overflows the weir and is stored in the right-hand portion of the tank until amount sufficient for charging the still has accumulated. 

Orifices and Mixing Nozdes Both liquids are pumped through constrictions in a pipe, the pressure drop of which is partly utilized to create the dispersion (see Fig. 18-34). Single nozzles or several in series may be used. For the orifice mixers, as many as 20 orifice plates... 

The difference in the dispersions of Colloid achieved in propeller and orifice mixers can be seen by examining Figure 4. 

Baffles. Baffle mixers have frequently been used in conjunction with each of the flow-mixer types described above to provide longer contact time in the dispersed condition with relatively little expenditure of power. They are essentially orifice mixers with the orifices replaced by segmental baffles, the opening representing to 3 of the cross-sectional area of the pipe in which they are installed, and they are placed downstream from the mixer. The more moderate turbulence they create will frequently maintain a dispersion sufflciently well to permit rapid extraction. Alternatively, the downstream pipe may be filled with tower packing such as Raschig rings to accomplish the same purpose (10, 30, 50). 

Tabls 10-10. Fkessure Drop through Orifice Mixers... 

Erample 10-1. Design of Orifice Mixer. Acid is to be mixed with 8,000 bbl per day of 53 API pressure distillate. A pressure drop of 25 psi is permissible. 

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