Two-zone reactor

Constrained optimization in a two-zone reactor where the wall temperature is prescribed as two constant temperature regions, the zone lengths being equal. 

The two-zone reactor has wall temperatures of the bang-bang type where... 

Simple methods have been presented to study constrained and free optimization in two-zone reactor systems and in systems with a continuous wall temperature profile. 

Ohkita et al.43 have used a two-zone reactor for the catalytic degradation of PE at 400 °C over amorphous silica-alumina and ZSM-5 zeolite. The polyolefin... 

Figure 5.17 GC-MS analysis of the oils produced by thermal-catalytic PE degradation at 400 °C in a two-zone reactor with assignments of the peaks corresponding to aromatic hydrocarbons.43...

Figure 5.18 Yields of styrene monomer and dimer obtained in the thermal-catalytic degradation of PS at 350 °C in a two-zone reactor over various metal oxide catalysts,44...

For the integrated, two-zone, reactor design with differing catalyst compositions. Figure 2 illustrates the unit set-up. Here the first and second catalyst beds (A and B) are of different composition. 

The continuous solution processes are usually carried out between 120-160 C at 400-500 Ib/in pressure. The diluents may be cyclohexane or isooctane. In one-zone reactors the solid catalyst is evenly dispersed throughout the reactor. In the two-zone reactors (specially constructed) the polymerizations are conducted with stirring in the lower zone where the catalysts are present in concentrations of 0.2-0.6% of the diluent. Purified ethylene is fed into the bottom portions of the reactors. The polymers that form are carried with small portions of the catalyst to the top and removed. To compensate for the loss, additional catalysts are added intermittently to the upper quiescent zones. 

In order to solve the problem caused by precipitates in reactors, a two-zone technique involving supercritical and subcritical chambers was exploited. A flow-chart of an SCWO process (MODAR process) featuring a two-zone reactor is shown in Fig. 21 [66]. In the upper zone, which is for sew at 600°C, the wastes are decomposed and the products are neutralized. In the lower zone (subcritical), in which the temperature of water is 200°C, the precipitates which formed in the upper zone are dissolved. 

Fig. 21. Flow diagram of SCWO process ( MODAR process ) featuring two-zone reactor [66].

Figure 12.3 Schematic diagram of a two-zone reactor for the preparation of graphite intercalation compounds.

To reduce the pressure drop, a batch reactor with a half-pipe jacket of length L and flowrate W can be partitioned into a two-zone jacket, each with a length L/2 and each supplied with W jacket flowrate. This doubles the jacket flow at a lower pressure drop in each zone. The flow in each zone can then be increased to increase the outside and overall heat transfer coefficients, which is similar to those of the single-zone jacket. 

Carbon Laydown. The potential for carbon laydown is readily estimated from the thermodynamics of Reactions 4 and 5. The areas where carbon laydown, according to these reactions, is thermodynamically possible were developed by Gruber (36). It is readily seen that carbon laydown via Reaction 4 is thermodynamically favorable at the reactor inlet for practically any commercially conceivable feed gas composition. As noted by Gruber (36), carbon laydown is thermodynamically unfavorable at the reactor outlet for practically all commercially conceivable methanator conditions. The methanation reactor will therefore, in practice, have two zones—the first is a finite zone between the inlet and some way down the catalyst bed where carbon laydown is thermodynamically possible, and the second zone is the balance of the reactor. 

Extend Problem 6.12 to a two-zone shell-and-tube reactor with different shell-side temperatures in the zones. 

For rocket processing, the ERH is divided into two zones. The first part of the reactor, nominally 10 feet, is initially fed 4 M (14 weight percent) NaOH with the temperature kept at 105°C to accommodate the relatively quick dissolution of the aluminum and burster... 

There are two mass transport equations - the main reactor and the dead-zone reactor - that need to be solved for the reactor combination given in Figure 6.9. These are... 

Two-phase gaslwater injector nozzles are mostly used in pilot- or full-scale bubble column applications (Krost, 1995) or in specialized, newly developed reactor types. An example is the Submerged Impinging Zone Reactor (IZR) (Gaddis and Vogelpohl, 1992 Air Products, 1998), which is constructed for very high mass-transfer rates. 

Figure 3 shows the flow pattern in the bottom part of the screw reactor along the vertical panel of baffles. Flow in the bottom zone is mostly rotational, with strong backflow observed in this area. Figure 4 shows the flow pattern in the horizontal panel along the baffle. Apparently, the flow along this panel can be divided into two zones, each of which moved along the reactor wall, met, and then moved downward. 

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