Gravity decanter

Another nickel cataly2ed process is described ia a Tolochimie patent (28). Reaction conditions claimed are 1—2.4 MPa (150—350 psi) at 100°C minimum. The combination continuous stirred reactor and gravity decanter uses density-driven circulation between the two vessels to recirculate the catalyst to the reaction 2one without the use of filters or pumps. Yield and catalyst usage can be controlled by varying the feed rates. 

FIG. 15-24 Gravity decanters, (a) External jackleg, side view, (h) Straight weirs, side view, (c) Circular weirs, side view, (d) Circular weirs, top view. 

Check gravity decanters for liquid seal and vapor equalizing line (syphon breaker). 

Figure 4-12. Gravity decanter basic dimensions. Adapted by permission, Schweitzer, P.A., McGraw-Hill Book Co. (1979) [32].

Gravity decanter, illustration, 243, 244 Happel/Jordan method, 241 Horizontal gravity, 239 Lamella classifiers, 239 Settler vessel, illustration, 240 Time planning and scheduling, process design, 36... 

Steady-state control of a continuously fed extraction column requires maintenance of the location of the liquid-liquid interface at one end of the column. The main interface will appear at the top of the column when the light phase is dispersed and at the bottom of the column when the heavy phase is dispersed. If needed, extraction columns can be designed with an expanded-diameter settling zone to facilitate liquid-liquid phase separation by reducing liquid velocities. If sufficient clarification of the phases cannot be achieved, then it may be necessary to add an external device such as a gravity decanter or centrifuge. (See Liquid-Liquid Phase Separation Equipment. ) Sometimes a column is built with expanded ends at... 

The ability to separate a mixture of two liquid phases is critical to the successful operatiou of mauy chemical aud petrochemical processes. Besides its obvious importauce to liquid-liquid extractiou aud washing operations, liquid-liquid phase separation can be a critical factor in other operations including two-liquid-phase reaction, azeotropic distillation, and industrial wastewater treatment. Sometimes the required phase separation can be accomplished within the main process equipment, such as in using an extraction column or a batch-wise, stirred-tank reactor but in many cases a stand-alone separator is used. These include many types of gravity decanters, filter-type coalescers, coalescers filled with granular media, centrifuges, and hydrocyclones. 

Design Considerations Gravity decanters normally are specified as horizontal vessels with a length-to-diameter ratio greater than 2 (and often greater than 4) to maximize the phase boundary (cross-sectional area) between the two settled layers. This provides more effective utilization of the vessel volume compared to vertical decanters, although vertical decanters may be more practical for low-flow applications or when space requirements limit the footprint of the vessel. 

The gravity decanter shown in Figure 16 is employed to separate three immiscible liquids. Calculate the heights of the two adjustable overflow legs and express the answer in feet. 

CONTINUOUS GRAVITY DECANTER. A gravity decanter of the type shown in Fig. 2.6 is used for the continuous separation of two immiscible liquids of differing densities. The feed mixture enters at one end of the separator the two liquids flow slowly through the vessel, separate into two layers, and discharge through overflow lines at the other end of the separator. 

Assume that the heavy liquid, of density p, overflows the dam at radius r, and the light liquid, of density pg, leaves through ports at radius r. Then if both liquids rotate with the bowl and friction is negligible, the pressure difference in the light liquid between fg and f must equal that in the heavy liquid between and (. The principle is exactly the same as in a continuous gravity decanter. 

A continuous gravity decanter is to separate chlorobenzene, with a density of 1109 kg/m , from an aqueous wash liquid having a density of 1020 kg/m. If the total depth in the separator is 1 m and the interface is to be 0.6 m from the vessel floor, (a) what should the height of the heavy-liquid overflow leg be (b) how much would an error of 50 mm in this height affect the position of the interface ... 

AUXILIARY EQUIPMENT. The dispersed phase in an extraction tower is allowed to coalesce at some point into a continuous layer from which one product stream is withdrawn. The interface between this layer and the predominant continuous phase is set in an open section at the top or bottom of a packed tower in a sieve-plate tower it is set in an open section near the top of the tower when the light phase is dispersed. If the heavy phase is dispersed, the interface is kept near the bottom of the tower. The interface level may be automatically controlled by a vented overflow leg for the heavy phase, as in a continuous gravity decanter. In large columns the interface is often held at the desired point by a level controller actuating a valve in the heavy-liquid discharge line. 

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