Flat distributor plate

Figure 4. Summary of gas bypassing data for a conical and a flat distributor plate.

The gas bypassing results obtained from tracer gas injection studies for a flat and a conical distributor plate are shown in Fig. 4. Theflow ratio, FR, is defined as the total gas flow supplied through the draft tube gas supply and the concentric solids feeder divided by the total gas flow supplied through the downcomer gas supply. The A and Y are the actual amounts of gas passing up the draft tube and the downcomer, respectively, determined from the tracer gas injection studies. If FR equals A Y. there is no gas bypassing. If FR is less than A Y. some of the flow supplied through the downcomer gas supply passes into the draft tube. If FR is larger than A/7, the reverse is true. 

Packed-tower efficiency and turndown are strongly dependent on the quality of initial liquid distribution. Uneven distribution may cause local variations in the liquid/gas ratio, localized pinch conditions, and reduced vapor-liquid contact. Figure 14 shows two common liquid distributor types, the ladder type (shown as the top distributor) and the orifice type (shown as the redistributor). The ladder type is a horizontal header of pipes, which are perforated on the underside. The orifice type is a flat perforated plate equipped with round or rectangular risers for gas passage. Other common types of distributors are a header equipped with spray nozzles (spray distributor) and a header of horizontal channels, with V notches cut in the vertical walls of the channels (notched-trough distributor). 

A vapor-distributing support (Fig. 3.10) is a flat perforated plate containing perforated vapor risers. Liquid descends through the floor perforations, while vapor rises through the riser perforations. The bottom portion of the vapor risers is unperforated, so that vapor is injected above the liquid pool on the plate. Sumps are optional and recommended (289) where liquid inventory is to be reduced. The vapor-distributing support combines two internals (a vapor distributor and a support plate) into one. Compared to a vapor distributor, this saves both vertical space and internals costs. On the other hand, obstruction of perforations by pieces of packing and possible liquid overflow into risers may make its vapor distribution quality somewhat lower. 

A perforated plate can be flat, concave, convex, or double-dished. The main advantages of the perforated plate are that it is simple, inexpensive, easy to modify, and easy to clean. The disadvantages of a perforated plate are the possibiUty of soflds leaking, ie, weeping through it into the plenum lower turndown capabiUty than other distributors the requirement of a peripheral seal and a relatively high pressure drop requited for good distribution. 

When both solids and gases pass through the distributor, such as in catalytic-cracldng units, a number of variations are or have been used, such as concentric rings in the same plane, with the annuli open (Fig. 17-9a) concentric rings in the form of a cone (Fig. 17-9b) grids of T bars or other structural shapes (Fig. 17-9c) flat metal perforated plates supported or reinforced with structural members (Fig. 17-9d) dished and perforated plates concave both upward and downward (Fig. 17-9e and f). The last two forms are generally more economical. 

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... 

Production of permeation-proof plastic fuel tanks can be realized using coextrusion with mbular die systems, followed up by hollow article extrusion blow molds. Using slit dies, multiple-layer, flat films or plates can be produced, which can then be deep-drawn. When the melt is united before the die, oxidizing gas can be blown into the airstream as an adhesion promoter, or adhesion promoter layers can be extruded into the material by means of coextrusion. Using a rotating mass distributor, sheathing with spiral markings can be made for switch wires, tubes and marbled profiles. 

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