Model, multi-component reactors

LPCVD reactor modeling involves many of the same issues of multi-component diffusion reactions that have been studied in the past decade in connection with heterogeneous catalysis. Complex fluid-flow phenomena strongly affect the performance of atmospheric-pressure CVD reactors. Two-dimensional and some three-dimensional flow structures in the classical horizontal and vertical CVD reactors have been explored through flow visual-... 

Although we restrict ourselves here to the coke formation reactions, the cracking reaction has to be modelled as well. This is mandatory in order to obtain proper values of concentrations of the coke precursors and the actual residence times of liquid and vapour. In addition, a proper description of the vapour-liquid equilibria (VLE) in the reactor is required. The model for the (thermal) cracking reaction involves multi-component kinetics and has been described before [8,9]. For the validation of the model on coke formation we refer to [9],... 

The model. A multi-component and multi-reactor system, arranged according to the general model depicted in Hg.5-1, is considered, which extends the scheme in Fig.4-1. It covers numerous flow arrangements and processes encountered in Chemical Engineering. 

In reactor modeling only the ordinary concentration diffusion term j° is generally considered. The rigorous kinetic theory model derivation for multi-component mixtures is outlined in chap 2. Meanwhile, the Tick s law for binary systems is used. 

Mitsubishi Heavy Industries computer code CHAMPAGNE is a multi-phase, multi-component thermodynamics model originally created for the assessment of severe accidents in fast breeder nuclear power reactors. It was recently modified to also treat the formation and spreading of hydrogen gas clouds. CHAMPAGNE has been successfully applied both as a 2D and 3D version to the NASA LH2 spill tests from 1980 (Fig. 8-9) [30]. 

Figure 7.7 Schematic diagram of the compartments in a multi-component finishing reactor model.

Multi-environment presumed PDF models can also be easily extended to treat cases with more than two feed streams. For example, a four-environment model for a flow with three feed streams is shown in Fig. 5.24. For this flow, the mixture-fraction vector will have two components, 2 and 22- The micromixing functions should thus be selected to agree with the variance transport equations for both components. However, in comparison with multi-variable presumed PDF methods for the mixture-fraction vector (see Section 5.3), the implementation of multi-environment presumed PDF models in CFD calculations of chemical reactors with multiple feed streams is much simpler. 

Very often in DCS-operated batch polymer reactors the primary process variables such as pressure, temperature, level, and flow (Section 12.2.1-12.2.4) are recorded during the batch as well as the quality variables at the end of the batch. However, it may be very difficult to obtain a kinetic model of the polymerization process due to the complexity of the reaction mechanism, which is frequently encountered in the batch manufacture of specialty polymers. In this case it is possible to use advanced statistical techniques such as multi-way principal component analysis (PCA) and multi-way partial least squares (PLS), along with an historical database of past successful batches to construct an empirical model of the batch [8, 58, 59]. This empirical model is used to monitor the evolution of future batch runs. Subsequent unusual events in the future can be detected during the course of the batch by referencing the measured process behavior against this incorrective action during the batch in order to bring it on aim. 

Remember that the volume Flows and chemical reactions comprised three parts 1. Fluid media with a single component, 2. Reactive mixtures, and 3. Interfaces and lines, that the volume Flows and Chemical Reactions in Homogeneous Mixtures comprised 1. Pipe flows, 2. Chemical reactors, and 3. Laminar and turbulent flames, and that the volume Flows and Chemical Reactions in Heterogeneous Mixtures comprised 1. Generation of multi-phase flows, 2. Problems at the scale of a particle, 3. Simplified model of a non-reactive flow with particles, 4. Simplified model of a reactive flow with particles, and 5. Radiative phenomena. 

Higher-order responses are the result of multi-capacitance processes that contain vessels in series, fluid or mechanical components of a process that are subjected to accelerations causing inertial effects to become important, or tbe addition of controllers to a system. In a chemical plant, higher-order systems that result from a combination of capacities and controllers are very common. Typical examples are reactors in series, heat exchangers and distillation columns. In the case of distillation columns, when controllers are attached to the column, very high-order, nonlinear differential equations result when the system is mathematically modelled. Mechanical conqtonent time constant and natural frequencies are very small relative to the process time constants and frequencies, and, as such, the resultant effects are typically minor. 

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