Packed-Tower Reactors

We consider the problem of determining the height, h, of a tower (i.e., of the packing in the tower) and its diameter, D, for a reaction of the model type  

G = total molar mass flow rate of gas, mol m-2 s-1 L = total liquid volumetric flow rate, m3 m-2 s 1 

The second term on the right is the flux of A at the gas-liquid interface, NA(z = 0). Thus, the continuity equation may be written as 

That is, since the rate of diffusion of B in the liquid film is = bNA for counter-diffusion, 

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Figure 243 Plow diagram and notation for packed-tower reactor for reaction A(g)+hB(f) - ...

Figure 3 shows the ozonation for two different types of reactors the 1500-ml. bottle reactor and the 1500-ml. packed tower reactor. There is no marked difference in the reaction rate constants, although the packed tower has a slightly lower rate constant than the bottle. If mass transfer were controlling in the reaction, the great deal of agitation in the packed tower would be expected to increase the value of K, The results, however, do not indicate this. It can be concluded that the ozonation does not need to be conducted in a packed tower type of reactor, and that the rate of solution of ozone is very fast compared to the rate of its reaction with cyanide, and that the rate of reaction is controlling. 

All actual reactors would operate in the shaded area between the two lines. Tubular reactors would be close to the upper line, stirred-tank reactors would be close to the lower line, and packed-tower reactors would be approximately halfway between. 

After the SO converter has stabilized, the 6—7% SO gas stream can be further diluted with dry air, I, to provide the SO reaction gas at a prescribed concentration, ca 4 vol % for LAB sulfonation and ca 2.5% for alcohol ethoxylate sulfation. The molten sulfur is accurately measured and controlled by mass flow meters. The organic feedstock is also accurately controlled by mass flow meters and a variable speed-driven gear pump. The high velocity SO reaction gas and organic feedstock are introduced into the top of the sulfonation reactor,, in cocurrent downward flow where the reaction product and gas are separated in a cyclone separator, K, then pumped to a cooler, L, and circulated back into a quench cooling reservoir at the base of the reactor, unique to Chemithon concentric reactor systems. The gas stream from the cyclone separator, M, is sent to an electrostatic precipitator (ESP), N, which removes entrained acidic organics, and then sent to the packed tower, H, where SO2 and any SO traces are adsorbed in a dilute NaOH solution and finally vented, O. Even a 99% conversion of SO2 to SO contributes ca 500 ppm SO2 to the effluent gas. 

Flow Reactors Fast reactions and those in the gas phase are generally done in tubular flow reaclors, just as they are often done on the commercial scale. Some heterogeneous reactors are shown in Fig. 23-29 the item in Fig. 23-29g is suited to liquid/liquid as well as gas/liquid. Stirred tanks, bubble and packed towers, and other commercial types are also used. The operadon of such units can sometimes be predicted from independent data of chemical and mass transfer rates, correlations of interfacial areas, droplet sizes, and other data. 

Reaction in a Centrifugal Pump In the reaction between acetic acid and gaseous ketene to make acetic anhydride, the pressure must be kept low (0.2 atm) to prevent polymerization of ketene. A packed tower with low pressure drop could be used but the required volume is very large because of the low pressure. Spes (Chem. Ing. Tech., 38, 963-966 [1966]) selected a centrifugal pump reactor where... 

In this chapter, we focus on the characteristics of the ideal-flow models themselves, without regard to the type of process equipment in which they occur, whether a chemical reactor, a heat exchanger, a packed tower, or some other type. In the following five chapters, we consider the design and performance of reactors in which ideal flow occurs. In addition, in this chapter, we introduce the segregated-flow model for a reactor as one application of the flow characteristics developed. 

Figure 24.1 Types of tower or column reactors for gas-liquid reactions (a) packed tower, (b) plate tower, (c) spray tower, (d) falling-film tower, (e) bubble column...

Figure 17.11. Types of contactors for reacting gases with liquids many of these also are suitable for reacting immiscible liquids. Tanks (a) with a gas entraining impeller (b) with baffled impellers (c) with a draft tube (d) with gas input through a rotating hollow shaft, (e) Venturi mixer for rapid reactions, (f) Self-priming turbine pump as a mixer-reactor, (g) Multispray chamber. Towers (h) parallel flow falling film (i) spray tower with gas as continuous phase (j) parallel flow packed tower (k) counter flow tray tower. (1) A doublepipe heat exchanger used as a tubular reactor.

To increase the yield of triethoxysilane, it is necessary to eliminate the hydrogen chloride formed from the reaction zone as soon as possible. It is hardly conceivable in periodical bubble reactors with a small phase contact surface. Because it is difficult to bring large amounts of heat for HCI desorption to the reactive mixture, packed towers do not allow for a continuous process either. The most convenient apparatus for the etherification of trichlorosilane is film-type, which allows for a continuous process. 

Fig. 48. Production diagram of tris ro-butoxyoligo[(propyleneoxy)(ethyleneoxy)-(dimethylsiloxy)] ethylsilane 7, 2, 9,11,12 - batch boxes 3, 10- reactors 4, 21 -coolers 5, 6, 8, 16, 17, 19, 22 - receptacles 7, 18 - pressure filters 13 - packed tower 14 - refluxer 75 - Florentine flask 20 - distillation tank 23 - container...

The target oligomer is synthesised in reactor 10. For this purpose, Laprol is loaded from batch box 11, and toluene is loaded from batch box 12. The agitator is switched on, the temperature in the reactor is increased to 110-130 °C (to 85-110 °C in vapours) by sending vapour into the jacket and at this temperature toluene is subjected to azeotropic drying. The vapour of the azeotropic mixture (toluene + water) rises up packed tower 13 and condenses in refluxer 14. The condensate splits in Florentine flask 15. Toluene from the top part of the apparatus is sent back (through a side choke) to reflux tower 13, and toluene-containing water is collected in receptacle 16. Thus the toluene solution of Laprol is dehydrated until moisture content is not more than 0.01%. 

Enameled reactor 4 with inverse cooler 5, an agitator and a jacket is filled with a solution of quinoline in chlorobenzene from agitator 3 and loaded with ammonia chloride and phosphorus pentachloride through a hatch. The synthesis is conducted at 128-130 °C until the quantity of released hydrogen chloride is noticeably reduced. Hydrogen chloride is absorbed with water in packed tower 7. After the process is finished, the reactive mixture is cooled and filtered in nutsch filter 8 to separate muriatic quinoline and the excess of ammonia chloride. Phosphonitrilechloride can also be conducted in tetrachloroethane medium in this case the process is carried out at 135-140 °C. 

The catalytic dehydrogenation of propane is carried out in a continuous packed-bed reactor. One thousand kilograms per hour of pure propane is preheated to a temperature of67(TC before it passes into the reactor. The reactor effluent gas. which includes propane, propylene, methane, and hydrogen, is cooled from 80(fC to lllfC and fed to an absorption tower, where the propane and propylene are dissolved in oil. 

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