Tube Reactor, Normal Flow

Tube Reactor, Normal Flow An alternative arrangement for such a reactor would be to align it vertically, and place the wafer on a pedestal normal to the flow direction. Such a system is shown in Figure 18. 

Normally, it makes little sense to apply such systems in lab-scale ozonation experiments, since the high mass transfer rates are only achieved at high gas flow rates which because of the typical operation characteristics of EDOGs accordingly means low ozone gas concentrations. An appropriate field of application was, however, presented in the study of Sunder and Hem pel (1996) who operated a tube-reactor for the ozonation of small concentrations of perchloroethylene. An injector nozzle coupled with the highly efficient Aquatector ozone-absorption unit was installed in front of the tube-reactor. Both the gas and liquid were partially recycled in this system. According to the authors more than 90 % of the ozone produced was absorbed in demineralized water and dissolved ozone concentrations ranged up to 100 pmol L-1 (cL = 5 mg L-1, T= 20 °C). 

Bell Jar Reactor, Barrel Susceptor, Radial Flow In much the same way that we extended the tube reactor with parallel flow to a bell jar geometry, we can do the same with the tube reactor with normal flow. Consider Figure 22. Since the flow is entering radially from the outside, one way to heat the susceptor is with high powered lamps within the central cavity. Again, the susceptor could be rotated to improve uniformity. 

Pancake Reactor The tube reactor with normal flow leads to another type of bell jar reactor referred to as the pancake reactor. It is shown in Figure 23. Here the susceptor is a disc placed horizontally and heated by induction by coils placed below it. The reactive gas flow could be introduced from above, but the favored approach is to introduce it from below at the center of the susceptor disc. Gas exhaust is at the periphery between the disc and the bell jar. 

These reactors normally consist of a microchannel or even a larger sized tube, where both phases stream in the form of a multiphase flow in the same encasing. 

During the process of heating the coolant and fuel to operating coolant temperature, it is necessary to withdraw 5.I per cent k of control rods. Thus, sufficient horizontal control rods are available to counteract the reactivity increase due to flooding. Flow monitoring instruments on each process tube would sense any gross water loss to the reactor core and would scram the horizontal control rods in 1.2 seconds. For a leakage rate equal to the normal flow to one process tube, 15O seconds would be required... 

Two types of continuous flow solid oxide cell reactors are typically used in electrochemical promotion experiments. The single chamber reactor depicted in Fig. B.l is made of a quartz tube closed at one end. The open end of the tube is mounted on a stainless steel cap, which has provisions for the introduction of reactants and removal of products as well as for the insertion of a thermocouple and connecting wires to the electrodes of the cell. A solid electrolyte disk, with three porous electrodes deposited on it, is appropriately clamped inside the reactor. Au wires are normally used to connect the catalyst-working electrode as well as the two Au auxiliary electrodes with the external circuit. These wires are mechanically pressed onto the corresponding electrodes, using an appropriate ceramic holder. A thermocouple, inserted in a closed-end quartz tube is used to measure the temperature of the solid electrolyte pellet. 

Equation (8.4) defines the average concentration, Ugut, of material flowing from the reactor. Omit the V ir) term inside the integral and normalize by the cross-sectional area, Ac = ttR, rather than the volumetric flow rate, Q. The result is the spatial average concentration a patiai, and is what you would measure if the contents of the tube were frozen and a small disk of the material was cut out and analyzed. In-line devices for measuring concentration may measure a panai rather than Uout- Is the difference important ... 

The nature of dispersion. The effect which the solid packing has on the flow pattern within a tubular reactor can sometimes be of sufficient magnitude to cause significant departures from plug flow conditions. The presence of solid particles in a tube causes elements of flowing gas to become displaced randomly and therefore produces a mixing effect. An eddy diffusion coefficient can be ascribed to this mixing effect and becomes superimposed on the transport processes which normally occur in unpacked tubes—either a molecular diffusion process at fairly low Reynolds... 

Catalyst batches were activated under two different activation conditions H2/CO (with 3% Ar) = 2.6 3.87 xmol/s (FT synthesis reaction mixture with H2/CO = 0.7) for 2 h at (1) 523 K and (2) 543 K. These conditions are based on temperatures and gases used by PETC to activate these catalysts for testing prior to a large scale pilot plant run. After activation, reactions were carried out over the catalyst samples in the same reactor tube at 523 K with H2/CO = 0.7 and a total gas flow rate of 6.47 pmol/s (with Ar as internal standard) at a pressure of 83.8 kPa (normal atmospheric pressure in Albuquerque). Two sets of samples were made, one for each of the two activation conditions. Each set consisted of three samples after activation, activation followed by FT reaction for 10 h, and activation followed by FT reaction for 45 h. In the case of the activation at 523 K, the first 2 h of the run were considered the activation step. Therefore, the activation in this case was at 523 K. For activation at 543 K, the catalyst bed was cooled to 523 K in the syngas mixture of activation. 

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