Case Study Reactor Data

From a chemical reactor, agitator current, temperatures and some analytical data was collected. The example was briefly discussed in the example of section 22.2. In that section only the mechanism of calculating the PCA model was explained. Let us look at the model of Eqn. (22.12). 

It is apparent that measurement Xi and measurement X2 have approximately the same coefficient in calculating the first score ti. It can also be seen in Fig. 22.3 that two principal components capture close to 70% of the variation in the data set. Let us therefore create a PCA model with two principal components. The loading plot for this model is shown in Fig. 22.8. 

Therefore measurement XI was deleted from the data set, because it did not provide additional information that was not captured by variable X2. Subsequently, a new PCA model was created and in this case 2 principal components explained more than 64% of the variance in the data set (Table 22.2). 

Although it might seem that the latter PCA model is not as good as the first one, the model between the reactor output variable (the conversion) and the reactor input variables (stored in the X5 matrix) will be better. 

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Rase Case Studies and Design Data, vol. 2 of Chemical Reactor Design for Process Plants, Wiley 1977) has these items ... 

A tempered water system has been specified for the reactor. It will be assumed that a 10°F rise in cooling water temperature is typical. Using data from the Case Study section of Chapter 5. 

The case study involves a well published multipurpose facility which is commonly known as BATCH1 in literature (Kondili et al 1993). It mainly consists of 3 chemical reactions which take place in 2 common reactors. In addition to the 2 common reactors, the flowsheet also entails the heater and the separator, before and after the reactors, respectively as shown if Fig. 6.6. The STN and SSN for the literature example are given in Figs. 6.7a and b, respectively. The data for this example appears in Table 6.5. 

This chapter contains a discussion of two intermediate level problems in chemical reactor design that indicate how the principles developed in previous chapters are applied in making preliminary design calculations for industrial scale units. The problems considered are the thermal cracking of propane in a tubular reactor and the production of phthalic anhydride in a fixed bed catalytic reactor. Space limitations preclude detailed case studies of these problems. In such studies one would systematically vary all relevant process parameters to arrive at an optimum reactor design. However, sufficient detail is provided within the illustrative problems to indicate the basic principles involved and to make it easy to extend the analysis to studies of other process variables. The conditions employed in these problems are not necessarily those used in current industrial practice, since the data are based on literature values that date back some years. 

The material on catalysis and heterogeneous reactions in Chapters 6, 1%, and 13 is a useful framework for an intermediate level graduate course in catalysis and chemical reactor design. In the latter course emphasis is placed on developing the student s ability to analyze critically actual kinetic data obtained from the literature in order to acquaint him with many of the traps into which the unwary may fall. Some of the problems in Chapter 12 and the illustrative case studies in Chapter 1 3 have evolved from this course. 

The second case study corresponds to an existing pyrolysis reactor also located at the Orica Botany Site in Sydney, Australia. This example demonstrates the usefulness of simplified mass and energy balances in data reconciliation. Both linear and nonlinear reconciliation techniques are used, as well as the strategy for joint parameter estimation and data reconciliation. Furthermore, the use of sequential processing of information for identifying inconsistencies in the operation of the furnace is discussed. 

Restrictions which may exist for the choice of a commercial reactor need not be imposed at the development stage. In some cases, a reactor of one type may be best for acquiring data in model characterisation, whereas a reactor of another type might be more suitable for full-scale production. (The cautions expressed in Sect. 4 must be taken into account.) Continuous flow back-mixed reactors can be very useful for kinetic studies because the absence of concentration gradients can reduce uncertainties in concentration measurements. When these reactors have attained a steady state, many of the problems associated with stiffness (see above) can be avoided. 

Then, a survey of micro reactors for heterogeneous catalyst screening introduces the technological methods used for screening. The description of microstructured reactors will be supplemented by other, conventional small-scale equipment such as mini-batch and fixed-bed reactors and small monoliths. For each of these reactors, exemplary applications will be given in order to demonstrate the properties of small-scale operation. Among a number of examples, methane oxidation as a sample reaction will be considered in detail. In a detailed case study, some intrinsic theoretical aspects of micro devices are discussed with respect to reactor design and experimental evaluation under the transient mode of reactor operation. It will be shown that, as soon as fluid dynamic information is added to the pure experimental data, more complex aspects of catalysis are derivable from overall conversion data, such as the intrinsic reaction kinetics. 

Rase, H. F., Chemical reactor design for process plants, vol II Case studies and design data, John Wiley Sons, New York, 1977. 

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... 

To assess the feasibility of the BSR as a competitor of the monolithic reactor, the parallel-passage reactor, and the lateral-flow reactor, it is necessary to do case studies in which the performance and price of these reactors are compared, for certain applications. To allow such case studies, two tools are needed (1) mathematical models of the reactors that predict the reactor performance, and (2) an optimization routine that, given a mathematical reactor model and a set of process specifications, finds the optimum reactor configuration. Furthermore, data are needed on costs, safety, availability, etc. In this section, five mathematical models of different complexity for the bead-string reactor (BSR) are presented that can be numerically solved on a personal computer within a few hours down to a few minutes. The implementation of the reactor models in an optimization routine, as well as detailed cost analyses of the reactor, are beyond the scope of this text. 

Doraiswamy (1974) on a particular variety of silica gel in a fixed-bed reactor. The role of catalyst deactivation was stndied by obtaining kinetic data at various times. Fortunately, by-products were negligible. This case study describes the reaction-deactivation kinetics and proposes a complete model using appropriate statistical methods. The emphasis will be on the use of a suitable algorithm for sequential updating of the models until one of them emerges as the best. ... 

Suppression of the mutual correlation between parameters will be illustrated by a case study. Rates of catalytic reactions are very frequently measured in gradientless and differential reactors, and the rate expressions of the Langmuir-Hinshelwood type are frequently used in the interpretation of experimental data. The rate expression has the general form... 

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