Tubular reactors power

The hydrodynamic factors that influence the plasma polymerization process pose a complicated problem and are of importance in the application of plasma for thin film coatings. When two reaction chambers with different shapes or sizes are used and when plasma polymerization of the same monomer is operated under the same operational conditions of RF power, monomer flow rate, pressure in the reaction chamber etc., the two plasma polymers formed in the two reaction chambers are never identical because of the differences in the hydrodynamic factors. In this sense, plasma polymerization is a reactor-dependent process. Yasuda and Hirotsu [22] systematically investigated the effects of hydrodynamic factors on the plasma polymerization process. They studied the effect of the monomer flow pattern on the polymer deposition rate in a tubular reactor. The polymer deposition rate is a function of the location in the chamber. The distribution of the polymer deposition rate is mainly determined by the distance from the plasma zone and the... 

Figure 27. Profile of radiant power in a tubular reactor [111].

Caro s acid, an equilibrium mixture of sulfuric acid, water, and peroxymono-sulfuric acid, is used in the metal-extraction industry. It is manufactured by reacting concentrated sulfuric acid with hydrogen peroxide. Caro s acid is a powerful oxidizing agent and decomposes readily. A process was developed to manufacture 1000 kg/day of Caro s acid in a tubular reactor with a volume of 20 ml and a residence time of less than one second, with the product immediately mixed with the solution to be treated (16). 

Note that not all velocity profiles in a tubular reactor are parabolic. Power law fluids have the profile... 

Design of experiments where hydrodynamic conditions are perfectly controlled small stirred reactors with high power input (no macromixing effects, circulation time tc << t, no spatial variation of e), multijet tubular reactors with a diameter large enough for pure homogeneous isotropic turbulence to be achieved. 

In stirred tanks, the power input to agitate the tank will depend on the physical properties of the liquid. In tubular reactors, the axial dispersion in empty tubes may be estimated [e.g., Wen in Petho and Noble (eds.), Residence Time Distribution Theory in Chemical Engineering, Verlag Chemie, 1982] as... 

Figure 19 Distribution of spectral volumetric absorbed power inside a tubular reactor illuminated by a 90° rim angle parabolic trough solar concentrator. Wavelength 325 nm and catalyst concentration 0.15 gL (Reprinted from Arancibia-Bulnes and Cuevas, 2004, with permission from Elsevier).

In order to examine the elfect of flow pattern in a reactor, which is a crucially important design factor of an LCVD reactor, it is necessary to examine the profile of deposition in a simple reactor first. A tubular reactor with an external radio frequency power coupling is ideally suited to the study of the distribution of polymer deposition. In such a reactor, 100% of the monomer passes through the luminous gas phase in the reactor, and the situation is very close to the case in which no bypass of monomer occurs. The experimental setup used for... 

The effects of the discharge power on the distribution of polymer deposition in a tubular reactor (Fig. 20.1) are shown in Figures 20.19-20.22. Figure 20.19 depicts the change in polymer deposition pattern due to the discharge power observed in the plasma polymerization of styrene at a fixed flow rate of 5.6 seem. 

For ease of fabrication and modular construction, tubular reactors are widely used in continuous processes in the chemical processing industry. Therefore, shell-and-tube membrane reactors will be adopted as the basic model geometry in this chapter. In real production situations, however, more complex geometries and flow configurations are encountered which may require three-dimensional numerical simulation of the complicated physicochemical hydrodynamics. With the advent of more powerful computers and more efficient computational fluid dynamics (CFD) codes, the solution to these complicated problems starts to become feasible. This is particularly true in view of the ongoing intensified interest in parallel computing as applied to CFD. 

In addition, the use of electrodless glow discharge will produce different results than those with internal electrodes. In the former case, rare gases such as He, Ar was introduced from one end of the tubular reactor and the plasma was sustained by a rf coil outside the reactor. Gaseous monomer was fed into the afterglow of a rare gas and polymer film deposited on the substrate placed downstream. Yasuda, et. al. (18) observed that the deposition rate in electrodeless discharge was independent of the power input and increased in proportional to the square of the monomer pressure. 

Fig. 8.10 Selectivity Sr of the undesired byproduct R in carrying out a reaction in a tubular reactor with a jet mixer as a function of the concentration ratios ca/cs and the dimensionless throughput-related propulsion jet power F oc Ap = P/rb for three different throughput ratios < a/< b from [638, 639]...

Five reactor designs are commonly used in the chemical processing industry stirred reactors, fixed-bed reactors, fluidized-bed reactors, tubular reactors, and furnace reactors. Nuclear reactors are also used to produce steam for power generation. 

Simulation of the adiabatic tubular reactor consists of the solution of the partial differential equations which describe the system. The nonlinear nature of these equations makes solution difficult. A powerful technique developed in recent years for the solution of nonlinear partial differential equations is that of quasilinearization. 

Figure 7.34 Dual stage preferential oxidation tubular reactor with 10 kWei power equivalent as developed by Lee et al. [545],...

For the integral method, the concentrations of the products and reactants are measured as a function of reaction or residence time, respectively. The integrated form of the rate equation is then plotted as a diagram. For example, in the case of a tubular reactor, we obtain for a power law rate equation by integration of Eq. (4.11.6) ... 

For turbulent flow in pipes the velocity profile can be calculated from the empirical power law design formula (1.360). Similar balance equations with purely molecular diffusivities can be used for a fully developed laminar flow in tubular reactors. The velocity profile is then parabolic, so the Hagen Poiseuille law (1.359) might suffice. It is important to note that the difference between the cross section averaged ID axial dispersion model equations (discussed in the previous section) and the simplified 2D model equations (presented above) is that the latter is valid locally at each point within the reactor, whereas the averaged one simply gives a cross sectional average description of the axial composition and temperature profiles. 

In a tubular polyethylene reactor, the high-pressure valves are an important part of the process technology. For example, the difference in pressure at the release valve at the end of the tubular reactor can amount to 3000 atm. The temperature difference across the valve can be up to 60°C. When the release valve is opened, the flow increases severalfold and the regulating power of the valve must be very high and can be 100 megapounds. The valve adjusting must take place in milliseconds and must be exact to 10 mm [7]. 

---