Bubble-cap distributors

Guo Q, Werther J (2004) Flow Behaviours in a Circulating Fluidized Bed with Various Bubble Cap Distributors. Ind Eng Chem Res 43 1756-1764 Hartge E-U, Li Y, Werther J (1986) Analysis of the local structure of the two phase flow in a fast fluidized bed. In CFB Technology, Pergamon press, pp 153-160... 

The fourth type of liquid distribution device is a bubble cap tray, originally designed for application in fractionation towers. This device employs a number of bubble caps laid out on a regular pitched pattern on a horizontal tray. The bubble cap distributor works on a vapor-assist principle that offers a relatively stable operation compared to a chimney device. The bubble cap is a cap centered concentrically over a standpipe. The sides of the cap are slotted for vapor flow. Liquid flows under the cap and is aspirated by the vapor, flowing upward in the aimular area between the cap and the standpipe, and then down through the standpipe. 

A comparison of the performance characteristics of a typical multi-port chimney type distributor and a standard bubble cap distributor is illustrated in Figure 2. 

Multi-port Chimney Distributor Bubble Cap Distributor... 

Fnr stripping service, as in a glycol or amine contactor (see Chapt 7 a bubble cap trays are the most common. In recent years, there has b growing movement toward crimped sheet structured packing. Improved vapor and liquid distributor design in conjunction with struc-... 

Adsorbers, distillation colunuis, and packed lowers are more complicated vessels and as a result, the potential exists for more serious hazards. These vessels are subject to tlie same potential haz. uds discussed previously in relation to leaks, corrosion, and stress. However, llicse separation columns contain a wide variety of internals or separation devices. Adsorbers or strippers usually contain packing, packing supports, liquid distributors, hold-down plates, and weirs. Depending on tlie physical and chemical properties of the fluids being passed tlirough tlie tower, potential liazards may result if incompatible materials are used for llie internals. Reactivity with llie metals used may cause undesirable reactions, which may lead to elevated temperatures and pressures and, ullinialely, to vessel rupture. Distillation columns may contain internals such as sieve trays, bubble caps, and valve plates, wliicli are also in conlacl with tlie... 

The differences in behavior between small laboratory beds and larger demonstration units can, in part, be attributed to a switch from porous plate distributors in the small bed to discrete hole or bubble caps in... 

There are three basic types of clean inlet gas distributors (1) a perforated plate distributor, (2) a bubble cap type of distributor, and (3) a sparger or pipe-grid type of gas distributor. The perforated plate distributor (Fig. 17-10d) is the simplest type of gas distributor and consists of a flat or curved plate containing a series of vertical holes. The gas flows upward into the bed from a chamber below the bed called a plenum. This type of distributor is easy and economical to construct. However, when the gas is shut off, the solids can sift downward into... 

Turndown. Moving valve and bubble-cap trays normally give better turndown than packings. Unless very expensive distributors are used, packed tower turndown is usually limited by distributor turndown. 

Figure 4. Industrial gas distributors (A) perforated plate (B) nozzle plate (C) bubble-cap plate.

Tray costs are shown in Fig. 16-26 for conventional installations. The approximate prices for various types and sizes of the most common industrial packings are indicated in Table 7. Costs for other packing materials are listed in Table 8. For rough estimates, the cost for a distributor plate in a packed tower can be assumed to be the same as that for one bubble-cap tray. 

As shown in Figure 12-18 the containing vessel is usually cylindrical, though not necessarily so. At the bottom of the bed is a distributor plate — porous, pierced with holes, or perhaps containing bubble caps—which acts as a support for the bed and distributes the gas evenly over the vessel cross section. Above the bed is a space, termed the disengaging section, which allows the solids caught in the gas stream to fall back into the bed. 

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