Reactor design, commercial models

At the first level of detail, it is not necessary to know the internal parameters for all the units, since what is desired is just the overall performance. For example, in a heat exchanger design, it suffices to know the heat duty, the total area, and the temperatures of the output streams the details such as the percentage baffle cut, tube layout, or baffle spacing can be specified later when the details of the proposed plant are better defined. It is important to realize the level of detail modeled by a commercial computer program. For example, a chemical reactor could be modeled as an equilibrium reactor, in which the input stream is brought to a new temperature and pressure and the... 

The viability of one particular use of a membrane reactor for partial oxidation reactions has been studied through mathematical modeling. The partial oxidation of methane has been used as a model selective oxidation reaction, where the intermediate product is much more reactive than the reactant. Kinetic data for V205/Si02 catalysts for methane partial oxidation are available in the literature and have been used in the modeling. Values have been selected for the other key parameters which appear in the dimensionless form of the reactor design equations based upon the physical properties of commercially available membrane materials. This parametric study has identified which parameters are most important, and what the values of these parameters must be to realize a performance enhancement over a plug-flow reactor. 

The objective of the following model is to investigate the extent to which Computational Fluid Mixing (CFM) models can be used as a tool in the design of industrial reactors. The commercially available program, Fluent , is used to calculate the flow pattern and the transport and reaction of chemical species in stirred tanks. The blend time predictions are compared with a literature correlation for blend time. The product distribution for a pair of competing chemical reactions is compared with experimental data from the literature. 

Figure 1 shows a computational framework, representing many years of Braun s research and development efforts in pyrolysis technology. Input to the system is a data base including pilot, commercial and literature sources. The data form the basis of a pyrolysis reactor model consistent with both theoretical and practical considerations. Modern computational techniques are used in the identification of model parameters. The model is then incorporated into a computer system capable of handling a wide range of industrial problems. Some of the applications are reactor design, economic and flexibility studies and process optimization and control. 

Chemical vapor deposition and heterogeneous catalysis share many kinetic and transport features, but CVD reactor design lags the corresponding catalytic reactor analysis both in level of sophistication and in scope. In the following we review the state of CVD reactor modelling and demonstrate how catalytic reactor design concepts may be applied to CVD processes. This is illustrated with an example where fixed bed reactor concepts are used to describe a commercial "multiple-wafers-in-tube" low pressure CVD reactor. 

Most commercial bioreactions are carried out in batch reactors. The design of a continuous bioreactor is desired since it may prove to be more economically rewarding than batch processes. Most desirable is a reactor that can sustain cells that are suspended in the reactor while growth medium is fed in, without allowing the cells to exit the reactor. Focus mixing modeling, separations, bioprocess kinetics, reactor design. 

This article attempts to unify the vast hterature on PTC chemistry with a comprehensive review of kinetic studies and mathematical modeling of PTC systems, which necessarily involve the role of intraphase and interphase mass transport. This coupling of knowledge from chemistry with engineering should prove useful in developing rational methods of reactor design and scale-up for commercial PTC applications. 

Kinetics models are useful for designing commercial reactors and for studying the fundamental mechanisms of the important reactions. The free-radical polymerization that takes place in emulsion systems is characterized by three main reactions initiation, propagation, and termination. Various radical transfer reactions can also be important. The rate of polymerization for bulk, solution, and suspension processes can be expressed as shown by Equation 2 ... 

Research supporting the development of a compact water gas shift (WGS) reactor subsystem included catalyst screening studies, kinetic model development, and test reactor design and performance evaluation. Water gas shift catalysts obtained from commercial and other developers were converted into an engineered form and tested versus temperature, space velocity, and steam-to-gas ratio in single-channel reactors. Both base metal and precious metal catalyst formulations were included in the studies. 

A comparison of Equations 5 and 7 illustrates some significant differences. First, the rate of initiation does not influence the number of particles formed in a steady-state CSTR even though it does influence particle concentration in a batch reactor. Second, the influence of surfactant concentration is stronger in the continuous reactor. Third, a new variable, 0, appears when a CSTR is used. These striking differences in behavior patterns result because of reactor differences. Both models are based on the same fundamental chemical and physical mechanisms. Such performance differences are significant for those involved in the utilization of batch reactor data to design commercial continuous systems. 

The above data analysis and model comparisons demonstrate the potential for using CSTR systems for fundamental kinetic studies. Clearly a great deal more needs to be done in both experimental and theoretical areas. Once reaction mechanisms are posulated and model components developed one can produce reactor models for batch, semi-batch and continuous reactors. If such models can successfully simulate experimental data from each of the various reactors one can gain the confidence necessary for design of commercial reactor systems. 

The improvement of the FCC technology was carried out via several types of reactors. In fact, the first one was an up-flow Model I FCC, followed by the down-flow Model II FCC. Also, stacked FCC design, Esso model 4 and the straight-riser design were developed. Eventually, the side-by-side design with straight riser, better for large units, was commercialized in 1950. 

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