Tube Reactor, Parallel Flow

Tube Reactor, Parallel Flow A sketch of this reactor configuration is shown in Figure 17. Here the reactant gas or gas mixture flows axially down a tube (circular or rectangular cross section) over a heated susceptor... 

The ideal tubular reactor is one in which elements of the homogeneous fluid reactant move through a tube as plugs moving parallel to the tube axis. This flow pattern is referred to as... 

In order to design an efficient reactor using a faUing film reactor, we would need to have many small tubes in parallel so that the interfacial area can be large. This is difficult to accomphsh with flow down tubes, but it is easy to accomplish with rising bubbles or faUing drops. The interfacial area is not now the area of the cyYilid T between gas... 

As with the falling film reactor, the rate of mass transfer to the catalyst goes as R, while the size of the reactor goes as R, so this reactor becomes very inefficient except for very small-diameter tubes. However, we can overcome this problem, not by using many small tubes in parallel, but by allowing the gas and liquid to flow (trickle) over porous catalyst pellets in a trickle bed reactor rather than down a vertical wall, as in the catalytic wall reactor. 

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.

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. 

The lowest resistivity silicide film of the four we are considering is the TiSi2 film, so such films have always been of interest. A recent study14 has shown that these films can also be deposited by low-pressure CVD. For these experiments, a cold-wall reactor similar to the parallel-flow tube reactor sketched in Figure 17 of Chapter 1 was used. The wafer was heated by heating the susceptor from below by optical radiation. 

The research at MIT has been done in the cold-wall vertical tube reactor shown in Figure 14. The wafer is aligned almost parallel to the flow on a vertical silicon carbide-coated susceptor. The wafer is heated by optical radiation from high-intensity lamps to a temperature of 775°C. Silane was introduced... 

The pyrolysis reactor can be simulated in Aspen Plus as PFR with power-law kinetics and temperature profile or heat duty. To validate the kinetic data, we consider an initial flow rate of 73000kg/h EDC at a reaction temperature of 530°C and 18 bar. The reactor consists of 16 tubes in parallel with an internal diameter of... 

Figure 16. Heat transfer medium control in tube-bundle fixed-bed reactors. A) Cross flow B) Parallel flow C) Multiple cooling sections.

Tn the multitubular cross-flow reactor, one or more baffles are used to force the coolant to flow across the tubes, and some parallel flow arises where the coolant flow direction reverses. 

The most common type of tubular flow reactor is the single-pass cylindrical tube. Another type is one that consists of a number of tubes in parallel. The reactor(s) may be vertical or horizontal. The feed is charged continuously at the inlet of the tube, and the products are continuously removed at the outlet. If heat exchange with surroundings is required, the reactor setup includes a jacketed tube. If the reactor is empty, a homogeneous reaction—one phase present—usually occurs. If the reactor contains catalyst particles, the reaction is said to be heterogeneous. 

The shell of this reactor is a 50 cm long glass tube with an inside diameter of 8 cm. The reactor end plates are lucite and are sealed with 0-rings to the glass tube. Two parallel plate copper electrodes, having exposed surfaces of 6.5 cm by 15 cm and separated by a gap of 3.5 cm, are located in the center of the glass tube. The lower electrode is water cooled and is grounded. Teflon inserts upstream and downstream of the electrodes create a smooth flow path across the electrodes and minimize boundary layer separation near the reaction zone. 

The process was carried out in flow with a pilot multi-tube reactor at Novocherkassk s plant (Russia). Each tube was combined with a separator and heating trap to collect a mix of liquid and solid products. To produce the suitable hydrocarbon amount for their analysis and to convert to the further industrial scale, 100 g of catalyst was placed into each reactor tube. Three series of 4 samples of 10% C0-M/AI2O3 catalysts with different amounts of the second metal have been parallel tested. The commercial synthesis-gas with CO/H2 = 1/2.2 was used. Temperature and space velocity were increased step by step from 150 until 200°C and from 100 to 300 hr respectively. Pressure was 0.9-1.0 MPa. The duration of each experiment over the bimetallic catalysts was at least 10 days maximum duration of continuous catalyst testing was 3 months. For comparison, also the monometallic 10%Co/Al2O3 has been tested for 100 hours. 

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