Horizontal extractors

Early extractor designs based on solvent percolation were basket-type extractors in which flaked seeds were placed in baskets with perforated bottoms. These systems looked like an enclosed bucket elevator. The baskets were supported by endless chains in a sealed housing and continuously raised and lowered at a slow rate (1 revolution/h). Each basket was filled with flaked seeds by an automatic feed hopper at the top. As the basket started descending solvent is sprayed over the baskets. The spent flakes in baskets ascended to the top of the housing on the opposite side of the feed hopper. At the top baskets were automatically inverted and spent seeds were discharged into a hopper, from which they were transferred to a meal desolventizer on a conveyor belt. Basket type extractors were bulky and hard to maintain. The newer extractor designs are horizontal and rotary type. The design principle for horizontal extractors is similar to the basket-type extractors but the baskets rotate in a... 

Tipping pan and horizontal filters are also used for leaching the modus operand of the Rotocel extractor resembles that of a tipping pan filter, although the details of its design differ slightly. 

The De Danske Sukkerfabriker (DDS) diffuser extractor (Fig. 6) is a relatively simple version of this family of machines, employing a double screw rotating in a vessel mounted at about 10° to the horizontal. The double screw is used to transport the soHds up the gradient of the sheU, while solvent flows down the gradient. Equipment using a single screw in a horizontal sheU for countercurrent extraction of soHds under pressure has been described (19). 

The Oldshue-Rushton (Mixco) extractor is similar in construction to the RDC in the fact that it is a relativelv open design, consisting of a series of compartments separated by horizontal stator baffles. The major difference from the RDC is that the height/diameter ratio of the compartments is greater, each compartment is fitted with vertical baffles, and the mixing is accomplished by means of a turbine impeller rather than a disc. 

FIG. 15-45 Second ScLeiLel extractor witL horizontal baffles and no wire-mesh packing between stages. [Repiinted with peimission of Am. Inst. Chem. Eng. J.,2, 74 (1956)]. 

Quadronics (L,iquid Dynamics) Extractor (Doyle et al., U.S. Patent 3,114,707, 1963, and others paper at AlChE meeting, St. Louis, February 1968) This is a horizontally rotated device, a variant of the Podbielniak extractor, in which either fixed or adjustable orifices may be inserted as a package radially. These permit control of the mixing intensity as the liquids pass radially through the extractor. Flow capacities, depending on machine size, range from 0.34 to 340 mVh (1.5 to 1500 gal/min). 

The endless-belt percolator (Wakeman, loc. cit.) is similar in principle, but the successive feed, solvent spray, drainage, and dumping stations are hnearly rather than circulany disposed. Examples are the de Smet belt extractor (uncompartmented) and the Lurgi frame belt (compartmented), the latter being a kind of linear equivalent of the Rotocel. Horizontal-belt vacuum filters, which resemble endless-belt extractors, are sometimes used for leaching. 

In the De Danske Sukkerfabriker, the axis of the extractor is tilted to about 10° from the horizontal, ehminating the necessity of two screws at different angles of inchnation. 

A more recently developed continuous extractor is the horizontal perforated belt extractor, probably the simplest percolation extractor from a mechanical view point. Here... 

The arrangement used is shown in Fig. 12(a). The horizontal plates are pierced with holes of small diameter (approximately J -in. diameter), whose total cross section may be 20 to 25% that of the column. No downspouts are provided, as for ordinary perforated-plate extractors, and both liquids must pass through the same holes. The plate spacing is usually small, 2 in. in large-diameter columns, for example. Columns of this sort may be pulsed at amplitudes of 1 in. and frequencies up to 150 cycles/min., depending upon the circumstances. 

Fig. 1— Horizontal separator employs four basic mechanisms to liberate gaa from liquid. Inlet diverter imposes a sudden direction and momentum change on the flowstrearn, causing heavier liquids to drop out. Gravity settling section provides opportunity for smaller droplets to leave gas stream, and mist extractor coalesces remaining liquids as gas exits vessel. In addition, entrained gas escapes In liquid collection section.

Another type of separator used in certain high-gaa/low-liquid flow applications is a filter separator. These can be either horizontal or vertical in configuration. Fig. 4 shows a horizontal design. Filter tubes in the initial separation section coalesce liquid mist into larger droplets as gas passes through the tubes. A secondary section, consisting of vanes or other mist extractor elements, removes these coalesced droplets. 

Such an assembly of mixing and separating equipment is represented in Figure 14.3(a), and more schematically in Figure 14.3(b). In the laboratory, the performance of a continuous countercurrent extractor can be simulated with a series of batch operations in separatory funnels, as in Figure 14.3(c). As the number of operations increases horizontally, the terminal concentrations E1 and R3 approach asymptotically those obtained in continuous equipment. Various kinds of more sophisticated continuous equipment also are widely used in laboratories some are described by Lo et at. (1983, pp. 497-506). Laboratory work is of particular importance for complex mixtures whose equilibrium relations are not known and for which stage requirements cannot be calculated. 

Figure 14.15. A horizontal rotating extractor and two kinds of centrifugal extractors, (a) The RTL (formerly Graesser raining bucket) horizontal rotating extractor both phases are dispersed at some portion of the rotation RTL S. A., London). (b) Operating principle of the Podbielniak centrifugal extractor it is made up of several concentric perforated cylinders (Baker-Perkins Co.), (c) The Luwesta centrifugal extractor (schematic diagram) Luwa Corp.).

FIG. 14-110 Typical impingement separators, (a) Jet impactor. (b) Wave plate, (c) Staggered channels. (Blaw-Knox Food 6- Chemical Equipment, Inc.) (d) Vane-type mist extractor. (Maloney-Crawford Tank and Mfg. Co.) (e) Peerless line separator. (Peerless Mfg. Co.) (/) Strong separator. (Strong Carlisle and Hammond.) (g) Karbate line separator. (Union Catbide Corporation) (h) Type E horizontal separator. (Wright-Austin Co.) (0 PL separator. (Ingersoll Rand.) (/) Wire-mesh demister. (Otto H. York Co.)... 

Podbielniak Extractor (Podbielniak, U.S. Patent 2,044,996, 1935, and other patents) This is the most important of the group. Refer to Fig. 15-55. Rotation is about a horizontal shaft. The body of the extractor is a cylindrical drum containing concentric perforate cyhnders. The hquids are introduced through the rotating shaft with the help of specid mechanical seals the light liquid is led internally to the drum periphery and the heavy liquid to the axis of the drum. Rapid rotation (up to several thousand revolutions per minute. 

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