Kettle-Type Reboilers

The liquid level on the shellside of kettle-type reboilers should be sufficient 

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Kettle-type reboilers, evaporators, etc., are often U-tube exchangers with enlarged shell sec tions for vapor-liquid separation. The U-tube bundle replaces the floating-heat bundle of Fig. 11-36. ... 

Kettle-type-reboiler costs are 15 to 25 percent greater than for equivalent internal-floatiug-head or U-tube exchangers. The higher extra is applicable with relatively large kettle-to-port-diameter ratios... 

The function of reboilers has already been discussed. These components are essentially heat exchangers that are used to transfer heat to bring the liquid at the bottom of the column to its boiling point (refer also to discussions in Chapter 1). The principle types employed are jacketted kettles, simple kettle type reboilers, internal reboilers, and thermo-syphon reboilers. Examples of each type are illustrated in Figure 7. 

G is a split flow. The fluid comes in and goes both way.s around the longitudinal baffle and then exits. H is very rare a double split flow. J is a divided flow. K is a kettle type reboiler, which is a special type and is best explained by looking at the example AKT in Figure 3-9. Kettle types are common where there is a boiling liquid or where gas is liberated from shell fluid as it is heated. The weir controls the liquid, making sure the tubes are always immersed in liquid. Gas that flashes from the liquid can exit the top nozzle. 

A pull-through, floating head, kettle-type reboiler having stationary head integral with the tubesheet, 23-in. port diameter and 37-in. inside shell diameter with tubes 16 ft long is denoted as SIZE 23/37-192 TYPE CKT,... 

When MEA is used in the presence of COS and CS2, they react to form heat-stable salts. Therefore, MEA systems usually include a reclaimer, The reclaimer is a kettle-type reboiler operating on a small side stream of lean solution. The temperature in the reclaimer is maintained such that the water and MEA boil to the overhead and are piped back to the stripper. The heat-stable salts remain in the reclaimer until the reclaimer is full. Then the reclaimer is shut-in and dumped to a waste disposal. Thus, the impurities are removed but the MEA bonded to the salts is also lost. 

Fischer formula, 4 697 a-Ketoxime, reduction, 2 572 Kettle soap making, 22 723, 736-737 Kettle-type reboilers, 79 510 Kevlar, 70 211, 212 79 742 20 79, 399 TD resins in, 22 589 Kevlar fibers, 73 373-376 26 760 Kew laboratories, 77 248—249 Key-and-lock principle, 7 574 Keyword-in-context (KWIC) index, 78 239 KF alumina, 5 337 Kharasch process, 79 114 Kidney, citric acid in, 6 632t Kidney Disease Outcome Quality Initiative (K/DOQI), 26 823 Kidney failure, 26 813 Kidney function, normal, 26 813 Kielselguhr 22 402... 

The partially vaporized refrigerant flows into the evaporator. In Fig. 22.1, the evaporator shown is similar to a kettle-type reboiler (see Chap. 5). The process fluid flows through the tube side of the kettle evaporator. The refrigerant liquid level is maintained by the letdown valve. The refrigerant vapor flows from the top of the kettle, to the compressor suction. 

Figure 8.4. Example of tubular heat exchangers (see also Fig. 8.14). (a) Double-pipe exchanger, (b) Scraped inner surface of a double-pipe exchanger, (c) Shell-and-tube exchanger with fixed tube sheets, (d) Kettle-type reboiler, (e) Horizontal shell side thermosiphon reboiler, (f) Vertical tube side thermosiphon reboiler, (g) Internal reboiler in a tower, (h) Air cooler with induced draft fan above the tube bank, (i) Air cooler with forced draft fan below the tube bank.

Evaporators employ heat to concentrate solutions or to recover dissolved solids by precipitating them from saturated solutions. They are reboilers with special provisions for separating liquid and vapor phases and for removal of solids when they are precipitated or crystallized out. Simple kettle-type reboilers [Fig. 8.4(d)] may be adequate in some applications, especially if enough freeboard is provided. Some of the many specialized types of evaporators that are in use are represented on Figure 8.16. The tubes may be horizontal or vertical, long or short the liquid may be outside or inside the tubes, circulation may be natural or forced with pumps or propellers. 

Reboilers need to be located next to the tower they serve, except for the pump-through types, which can be located elsewhere. Fired heater reboilers are always located away from the associated tower and use a pump to circulate the bottoms. Kettle-type reboilers are preferred from an operational and hydraulic standpoint because they can be designed without the worry of having to ensure sufficient head for circulation required by thermosyphon reboilers. However, kettle reboilers require a larger-diameter shell that is more cosdy, and the reboiler must be supported at a sufficient elevation to get the product to the bottoms pump with adequate NPSH. 

MAXIMUM HEAT FLUX FOR KETTLE-TYPE REBOILER 7.60... 

Horizontal tube evaporators may be susceptible to vapor-binding, and foaming liquids cannot usually be handled. The short tube variety is seldom used today except for preparation of boiler feed water. The kettle-type reboiler is frequently used in chemical plant applications for clean fluids. 

A kettle type reboiler produces high evaporation rates. For this reboiler, a large diameter return line might be necessary. The process flow diagram, of course, should indicate flow rates and the physical properties of the flowing fluid. 

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