Batch reactor performance

Compare the batch reactor performance at constant Cp with that for variable Cp. Do this by setting both Cp values constant at a temperature Tj... 

As with continuous processes, the heart of a batch chemical process is its reactor. Idealized reactor models were considered in Chapter 5. In an ideal-batch reactor, all fluid elements have the same residence time. There is thus an analogy between ideal-batch reactors and plug-flow reactors. There are four major factors that effect batch reactor performance ... 

For batch reactors the four major factors that effect batch reactor performance are ... 

Batch Reactor. Figure 18.15 sketches the main features of an experimental reactor which uses a batch of catalyst and a batch of fluid. In this system we follow the changing composition with time and interpret the results with the batch reactor performance equation. 

The experimental study of solid catalyzed gaseous reactions can be performed in batch, continuous flow stirred tank, or tubular flow reactors. This involves a stirred tank reactor with a recycle system flowing through a catalyzed bed (Figure 5-31). For integral analysis, a rate equation is selected for testing and the batch reactor performance equation is integrated. An example is the rate on a catalyst mass basis in Equation 5-322. 

The kinetic modelling of complex multiphase catalytic reactions needs a careful consideration of various complexities of adsorption and desorption of reactants and products. In such cases the kinetic model developed based on the initial rate data may not be adequate to explain the integral batch reactor performance. Hence it was thought appropriate to use mainly the integral rate data for developing a suitable kinetic model. Different rate equations were derived based on various Langumir-Hinshelwood mechanisms and a few of them are given below. 

Fig. 5.2 Batch reactor performance with MichaeUs-Menten kinetics...

Fig. 5.4 Batch reactor performance for sequential ordered kinetics (as = 500IU/g Ka ImM Kb = 2mM = 2mM Kg = 4mM) with A as limiting substrate (ai = lOmM bj 20mM) or B as limiting substrate (ai = 20mM bi = lOmM)...

From Eq. 5.6, the model for a batch reactor performance considering one-substrate reactions (Eq. 5.3) and one-stage first-order inactivation mechanism (Eq. 5.46) is ... 

Nys 2002 Pan and Syu 2005 Giordano et al. 2006). We developed a model for describing batch reactor performance with immobilized penicillin acylase for the KCS of cephalexin from 7ADCA and PGME based on the kinetic mechanism proposed by Nam et al. (1985). The rate of cephalexin synthesis can be expressed as ... 

As a first step, based on laboratory-scale data at different times, a rate equation can be developed and then the batch reactor performance equation... 

For a constant volume reaction, a batch reactor performs as a PFR if the reaction time equals the residence time (for a reaction with a changing volume see Topic 4.10.1). 

Batch reactors often are used to develop continuous processes because of their suitabiUty and convenient use in laboratory experimentation. Industrial practice generally favors processing continuously rather than in single batches, because overall investment and operating costs usually are less. Data obtained in batch reactors, except for very rapid reactions, can be well defined and used to predict performance of larger scale, continuous-flow reactors. Almost all batch reactors are well stirred thus, ideally, compositions are uniform throughout and residence times of all contained reactants are constant. 

A useful classification of lands of reaclors is in terms of their concentration distributions. The concentration profiles of certain limiting cases are illustrated in Fig. 7-3 namely, of batch reactors, continuously stirred tanks, and tubular flow reactors. Basic types of flow reactors are illustrated in Fig. 7-4. Many others, employing granular catalysts and for multiphase reactions, are illustratea throughout Sec. 23. The present material deals with the sizes, performances and heat effects of these ideal types. They afford standards of comparison. 

Selectivity A significant respect in which CSTRs may differ from batch (or PFR) reaclors is in the product distribution of complex reactions. However, each particular set of reactions must be treated individually to find the superiority. For the consecutive reactions A B C, Fig. 7-5b shows that a higher peak value of B is reached in batch reactors than in CSTRs as the number of stages increases the batch performance is approached. 

Suppose the reaction is performed in a batch reactor of constant volume V(m ) at a constant temperature T(K), beginning with pure A... 

The effect of physical processes on reactor performance is more complex than for two-phase systems because both gas-liquid and liquid-solid interphase transport effects may be coupled with the intrinsic rate. The most common types of three-phase reactors are the slurry and trickle-bed reactors. These have found wide applications in the petroleum industry. A slurry reactor is a multi-phase flow reactor in which the reactant gas is bubbled through a solution containing solid catalyst particles. The reactor may operate continuously as a steady flow system with respect to both gas and liquid phases. Alternatively, a fixed charge of liquid is initially added to the stirred vessel, and the gas is continuously added such that the reactor is batch with respect to the liquid phase. This method is used in some hydrogenation reactions such as hydrogenation of oils in a slurry of nickel catalyst particles. Figure 4-15 shows a slurry-type reactor used for polymerization of ethylene in a sluiTy of solid catalyst particles in a solvent of cyclohexane. 

The following details establish reactor performance, considers the overall fractional yield, and predicts the concentration profiles with time of complex reactions in batch systems using the Runge-Kutta numerical method of analysis. 

From diese various estimates, die total batch cycle time t(, is used in batch reactor design to determine die productivity of die reactor. Batch reactors are used in operations dial are small and when multiproducts are required. Pilot plant trials for sales samples in a new market development are carried out in batch reactors. Use of batch reactors can be seen in pharmaceutical, fine chemicals, biochemical, and dye industries. This is because multi-product, changeable demand often requues a single unit to be used in various production campaigns. However, batch reactors are seldom employed on an industrial scale for gas phase reactions. This is due to die limited quantity produced, aldiough batch reactors can be readily employed for kinetic studies of gas phase reactions. Figure 5-4 illustrates die performance equations for batch reactors. 

Biocatalysts in nature tend to be optimized to perform best in aqueous environments, at neutral pH, temperatures below 40 °C, and at low osmotic pressure. These conditions are sometimes in conflict with the need of the chemist or process engineer to optimize a reaction with respect to space-time yield or high product concentration in order to facilitate downstream processing. Furthermore, enzymes and whole cells are often inhibited by products or substrates. This might be overcome by the use of continuously operated stirred tank reactors, fed-batch reactors, or reactors with in situ product removal [14, 15]. The addition of organic solvents to increase the solubility of substrates and/or products is a common practice [16]. 

In order to be economically viable, a continuous emulsion polymerization process must be able to produce a latex which satisfies application requirements at high rates without frequent disruptions. Since most latex products are developed in batch equipment, the problems associated with converting to continuous systems can be significant. Making such a change requires an understanding of the differences between batch and continuous reactors and how these differences influence product properties and reactor performance. 

A summary of the nine batch reactor emulsion polymerizations and fifteen tubular reactor emulsion polymerizations are presented in Tables III IV. Also, many tubular reactor pressure drop measurements were performed at different Reynolds numbers using distilled water to determined the laminar-turbulent transitional flow regime. 

Reactor Performance Measures. There are four common measures of reactor performance fraction unreacted, conversion, yield, and selectivity. The fraction unreacted is the simplest and is usually found directly when solving the component balance equations. It is a t)/oo for a batch reaction and aout/ciin for a flow reactor. The conversion is just 1 minus the fraction unreacted. The terms conversion and fraction unreacted refer to a specific reactant. It is usually the stoichiometrically limiting reactant. See Equation (1.26) for the first-order case. 

Example 12.8 The batch reactor in Example 12.7 has been converted to a CSTR. Determine its steady-state performance at a mean residence time of 4 h. Ignore product inhibition. 

A binary polycondensation of AMA and BNB is to be performed in a batch reactor. A number average chain length of at least 100 is required. What minimum accuracy is required for weighing the two components ... 

The choice of the material is also strategic for two reasons to obtain an apparatus resisting to the corrosion of the different chemical products, like glass for glass-lined batch reactors, but also to keep high heat transfer performances, like aluminum in the case of HEXs. Steel and more so SiC appear to be very interesting compromises for both aspects. 

Suppose we perform an organic synthesis in a batch reactor where the desired molecule is the intermediate and not the end product. It is then very important that we know how long we should let the reaction run to obtain the highest yield of the intermediate. Setting the differential d[I]/dt in Eq. (99) equal to zero and substituting Eq. (102) into Eq. (99) we find the time, at which the maximum is reached - and by inserting Wx in Eq. (102) the corresponding optimal concentration of the intermediate ... 

Figure 4.50 Comparison of isomeric ratios for 1,5- and 1,8-dinitronaphthalene. Reaction was performed in a macroscopic batch reactor and micro reactors of different types and from different suppliers [37],...

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