Bubble plates

Nonisothermal Gas Absorption. The computation of nonisothermal gas absorption processes is difficult because of all the interactions involved as described for packed columns. A computer is normally required for the enormous number of plate calculations necessary to estabUsh the correct concentration and temperature profiles through the tower. Suitable algorithms have been developed (46,105) and nonisothermal gas absorption in plate columns has been studied experimentally and the measured profiles compared to the calculated results (47,106). Figure 27 shows a typical Hquid temperature profile observed in an adiabatic bubble plate absorber (107). The close agreement between the calculated and observed profiles was obtained without adjusting parameters. The plate efficiencies required for the calculations were measured independendy on a single exact copy of the bubble cap plates installed in the five-tray absorber. 

Rate of Mass Transfer in Bubble Plates. The Murphree vapor efficiency, much like the height of a transfer unit in packed absorbers, characterizes the rate of mass transfer in the equipment. The value of the efficiency depends on a large number of parameters not normally known, and its prediction is therefore difficult and involved. Correlations have led to widely used empirical relationships, which can be used for rough estimates (109,110). The most fundamental approach for tray efficiency estimation, however, summarizing intensive research on this topic, may be found in reference 111. 

Moving Body Viscometers. In moving body viscometers, the motion of a ball, bubble, plate, needle, or rod through a material is monitored. 

Bubble plate A plate or cap used in ab sorption equipment. 

Air containing ammonia is contacted with fresh water in a two-stage countercurrent bubble-plate absorber. Ln and V are the molar flowrates of liquid and gas respectively leaving the nth plate. xn and yn are the mole fractions of NH3 in liquid and gas respectively leaving the nth plate. // is the molar holdup of liquid on the nth plate. Plates are numbered up the column. 

Much of this work was carried out using a special distilling column called a bubble-plate column (Fig. 141). Each plate really does act like a distilling flask with a very efficient column, and one distillation is really carried out on one physical plate. To calculate the number of plates (separation steps, or distillations) for a bubble-plate column, you just count them ... 

Unfortunately, the fractionating column you usually get is not a bubble-plate type. You have an open tube that you fill with column packing (see Class 3 Fractional Distillation ) and noplates. The distillations up this type of column are not discreet, and the question of where one plate begins and another ends is meaningless. Yet, if you use this type of column, you do get a better separation than if you used no column at all. It s as if you had a column with some bubble-plates. And if your distilling column separates a mixture as well as a bubble-plate column with two real plates, you must have a column with two theoretical plates. 

Well, all you can do is estimate that it falls at, say, a little more than half of the way along this second tie-line, eh (Point K) OK then. This column has been officially declared to have 1.6 theoretical plates. Can you have tenths of plates Not with a bubble-plate column, but certainly with any column that does not have discrete separation stages. 

Almost all the results reported in literature pertain to studies with horizontally oriented orifices, and the discussions in the preceding sections are applicable only to such orifices. In industrial applications, however, the orifices are usually oriented at various angles, the most common (as in the case of the bubble plates) being n/2 from the horizontal. 

Geddes, R. L. Trans. Am. Inst. Chem. Eng. 42 (1946) 79. Local efficiencies of bubble plate fractionators. 

The development of adsorption as a method of fractionation has been analogous to the development of distillation. In both cases the operation was originally carried out in a simple batch unit. After many years, rectification was added and close fractionation became possible. In the case of distillation this was done by adding a packed or bubble plate column to the still kettle. In the case of adsorption it involved the use of an adsorbent-packed column to obtain chromatographic separation, which gave a rectification effect. 

Air containing ammonia is contacted with fresh water in a two-stage countercurrent bubble-plate absorber. 

Bubble cap an inverted cup with a notched or slotted periphery to disperse the vapor in small bubbles beneath the surface of the liquid on the bubble plate in a distillation tower. 

Riser the part of the bubble-plate assembly which channels the vapor and causes it to flow downward to escape through the liquid also the vertical pipe where fluid catalytic cracking reactions occur. 

The objective of absorption equipment is to provide intimate contact between the liquid concerned and gas, thus facilitating the absorption process. When a large volume of gas is absorbed per unit volume of liquid, a marked rise in temperature may result and devices for the removal of the heat evolved are then an important feature of the equipment. Apart from packed towers, the types of equipment described here include agitated vessels, bubble-plate towers, cooler-absorbers and spray towers. 

FIG. 15-38 Extraction rates for sieve-plate and modified bubble-plate columns. System benzoic acid-water-toluene, except where noted. To convert feet to meters, multiply by 0.3048 to convert inches to centimeters, multiply by 2.54. [Allerton, Strom, and Treybal, Trans. Am. Inst. Chem. Eng., 39y 361 (1943) Row, Kojfolt, and Withrow, ibid., 37,559 (1941) Treybal and Dumoulin, Ind. Eng. Chem., 34, 709(1942).]... 

The fifth and final type of fluid-bed plate to be mentioned here is the so-called bubble plate type. Illustrated in Fig. 12-74, it is in principle a gill-type plate. The orifice is cut out of the plate, and the bub-... 

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