Parameters Affecting Reactor Performance

The term reactor performance usually refers to the operating results achieved by a reactor, particularly with respect to fraction of reactant converted or product distribution 

At this stage, type (1) is more apparent than type (2), and we provide some preliminary discussion of (2) here. Flow characteristics include relative times taken by elements of fluid to pass through the reactor (residence-time distribution), and mixing character- 

---

In this introductory chapter, we first consider what chemical kinetics and chemical reaction engineering (CRE) are about, and how they are interrelated. We then introduce some important aspects of kinetics and CRE, including the involvement of chemical stoichiometry, thermodynamics and equilibrium, and various other rate processes. Since the rate of reaction is of primary importance, we must pay attention to how it is defined, measured, and represented, and to the parameters that affect it. We also introduce some of the main considerations in reactor design, and parameters affecting reactor performance. These considerations lead to a plan of treatment for the following chapters. 

There are different parameters associated with the set of algebraic/differential equations describing the non-isothermal CSTR and they are shown in Table 10.1. To have a clearer vision and see how each such parameter affects the performance of the process, you may attempt to increase or decrease its value and see how soon the non-isothermal reactor evolves to steady-state conditions in terms of C, r, and Tj. Alternatively, you may monitor as a function of time. For example, if the molecular weight of B is 40 g/mol, then the following set of commands can be added at the end of... 

The major process parameters at selected periods in the four experiments are listed in Tables II, IV, VII, and VIII. Carbon recoveries ranged from 63 to 91%. Most of the losses occurred in connection with the recycle compressor system, and they decreased correspondingly the volume of product gas metered. Such losses, however, did not affect significantly the incoming gas to the main reactor or reactor performance. 

The amount of the immobilized biocatalyst is an important parameter and strongly affects the reactor performance, enzymes in fact, are not able to work at high concentration. 

The above discussion on previous experimental studies in trickle-bed reactors suggests that both liquid-solid contacting and mass transfer limitations play a role in affecting trickle-bed reactor performance. Except for a few isolated cases, the reactor models proposed in the literature for gaseous reactant limiting reactions have not incorporated particle-scale incomplete contacting as paft of their development. For cases where it was used, this parameter served as an adjustable constant to match the observed conversion versus liquid mass velocity data so that the true predictive ability of the model... 

The choice of the above three modes of catalyst placement relative to the membrane can significantly affect the reactor performance. From the analysis of catalytically active and passive (inert) membrane reactors [Sun and Khang, 1988], it appears that the critical parameter determining the choice is the reaction residence time. At low residence times, the difference between a catalytically active and a catalytically passive membrane is not significant. However, as the reaction residence time becomes high, the catalytically active membrane shows a higher reaction conversion. 

Recently, the fluidized bed membrane reactor (FBMR) has also been examined from the scale-up and practical points of view. Key factors affecting the performance of a commercial FBMR were analysed and compared to corresponding factors in the PBMR. Challenges to the commercial viability of the FBMR were identified. A very important design parameter was determined to be the distribution of membrane area between the dense bed and the dilute phase. Key areas for commercial viability were mechanical stability of reactor internals, the durability of the membrane material, and the effect of gas withdrawal on fluidization. Thermal uniformity was identified as an advantageous property of the FBMR. 

Although it is not essential to understand the chemistry of cyanoacrylate polymerization to be able to use these adhesives, knowing that a chemical reaction is taking place helps the user to understand how application conditions affect their performance. Consider the fact that the common polymers, such as polyethylene, polystyrene, and poly(vinyl chloride) (PVC), are made in sophisticated reactors. Parameters such as temperature, monomer concentration, and amount of activator are carefully controlled. 

FBTR has 36 neutronic and process parameters initiating reactor trip and has encountered large number of trips since first criticality. The paper also highlights several modifications affected in safety related systems for improved performance and safety reviews to reduce the parameters initiating reactor trip. 

In this chapter it was shown that the major engineering parameters which might affect the performance of a FT slurry reactor can be estimated from rather reliable correlations. There are, however, some controversial results in the literature which concern gas holdup and interfacial area (bubble diameter). Additional studies would be valuable for further clarification of this point. However, one can state, at least, that gas holdup and interfacial area are surprisingly large in the... 

The US DOE had a major effort to understand the many variables affecting the performance of a bubble column reactor. Dudukovic and Toseland [75] outlined the cooperative study by Air Products and Chemicals (APC), Ohio State University (OSU), Sandia National Laboratory (SNL), and Washington University in St. Louis (WU). The efforts of this group have developed valuable unique experimental techniques for the measurement of gas holdup, velocity, and eddy diffusivities in bubble columns. They have obtained data that allows improved insight in churn-turbulent flow and have assessed the impact of various effects (internals, solid concentration, high gas velocity, pressure, etc.). General ideal flow pattern-based models do not reflect bubble column reality to date the models are based on a combination where some parameters are evaluated from first principles and some from the database. 

The effect of operating conditions of the reformer and the carbon monoxide clean-up reactors on their individual performance was discussed in Sections 5.1 and 5.2. However, the operating parameters of the reformer also affect the performance of the clean-up reactors. Increasing the reformer temperature increases the load on the water-gas shift reactors downstream, because the carbon monoxide content is higher... 

The performance of a chemical reactor, i.e., the relation between output and input, is affected by the properties of the reactional system (kinetics, thermodynamics,...) and by the contacting pattern. The importance of this contacting pattern is quite obvious in the case of multiphase reactors like trickle-bed reactors. Reactants are indeed present in both fluid phases and reactions occur at the contact of the catalytic solid phase. Unfortunately the description of the fluid flow pattern is very difficult because of the high number of intricate mechanisms that can control this pattern. The situation is so complex that, in many cases, we do not even know the essential hydrodynamic parameters that may affect the performance of the reactor. 

A. 1618. A detailed analysis of the core and system performance shall be given. The methods used to characterize the reactor core and system performance under accident conditions shall be discussed and the important results of the analysis presented. The discussion should include, where appropriate, an evaluation of the parameters that may affect the performance of barriers restricting the transport of radioactive material from the fuel to die environment (e.g. fuel cladding, primary cooling system and building/systems providing confinement). 

In the reactor, the clad is subjected to a very complex set of phenomena, particularly when the power is cycled. The most important parameters alfecting clad performance are thermal stress cycling and stress concentrations caused by nonuniform axial and nonaxisymmetric fuel behavior. Both these factors are expected to be less damaging in sodium-cooled reactors than in gas- or water-cooled systems, because high coolant pressures force the clad to collapse onto the fuel and follow its movements as the power varies. They can, however, still significantly affect fuel pin life. 

Based on experimental results and a model describing the kinetics of the system, it has been found that the temperature has the strongest influence on the performance of the system as it affects both the kinetics of esterification and of pervaporation. The rate of reaction increases with temperature according to Arrhenius law, whereas an increased temperature accelerates the pervaporation process also. Consequently, the water content decreases much faster at a higher temperature. The second important parameter is the initial molar ratio of the reactants involved. It has to be noted, however, that a deviation in the initial molar ratio from the stoichiometric value requires a rather expensive separation step to recover the unreacted component afterwards. The third factor is the ratio of membrane area to reaction volume, at least in the case of a batch reactor. For continuous opera-... 

We have presented a general reaction-diffusion model for porous catalyst particles in stirred semibatch reactors applied to three-phase processes. The model was solved numerically for small and large catalyst particles to elucidate the role of internal and external mass transfer limitations. The case studies (citral and sugar hydrogenation) revealed that both internal and external resistances can considerably affect the rate and selectivity of the process. In order to obtain the best possible performance of industrial reactors, it is necessary to use this kind of simulation approach, which helps to optimize the process parameters, such as temperature, hydrogen pressure, catalyst particle size and the stirring conditions. 

In this paper, we will first illustrate the mathematical models used to describe the coke-conversion selectivity for FFB, MAT and riser reactors. The models also include matrix and zeolite contributions. Intrinsic activity parameters estimated from a small isothermal riser will then be used to predict the FFB and MAT data. The inverse problem of predicting riser performance from FFB and MAT data is straightforward based on the proposed theory. A parametric study is performed to show the sensitivity to changes in coke selectivity and heat of reaction which are affected by catalyst type. We will highlight the quantitative differences in observed conversion and coke-conversion selectivity of various reactors. 

---