Simple batch reactor

The relatively low capital cost of the simple batch reactor is its most enticing feature. The inabiUty to operate under pressure typically limits the simple batch reactor to use with the higher alkenes ie, octenes, nonenes, and dodecenes. For mainly economic reasons, these reactors are usually mn at phenol to alkene mole ratios of between 0.9 and 1.1 to 1. 

The same four operating steps are used with the complex batch reactor as with the simple batch reactor. The powerhil capabiUties of the complex batch reactor offset their relatively high capital cost. These reactors can operate at phenol to alkene mole ratios from 0.3 to 1 and up. This abiUty is achieved by designing for positive pressure operation, typically 200 to 2000 kPa (30 to 300 psig), and for the use of highly selective catalysts. Because these reactors can operate at low phenol to alkene mole ratios, they are ideal for production of di- and trialkylphenols. 

Unrefined alkylphenols are generally produced in the simple batch reactors described eadier. An alkene with between 8 and 12 carbon atoms reacts with phenol to produce a mixture of reactants, mono alkylphenols, and dialkylphenols. These mixtures usually do not free2e above 25 °C and so are Hquid at production and storage conditions. The product is generally used in the same factory or complex in which it is produced so shipment typically consists of pumping the material from the reactor to a storage tank. 

The ideal tank reactor is one in which stirring is so efficient that the contents are always uniform in composition and temperature throughout. The simple tank reactor may be operated in a variety of modes batch, semibatch, and continuous flow. These modes are illustrated schematically in Figure 8.1. In the simple batch reactor the fluid elements will all have the same composition, but the composition will be time dependent. The stirred tank reactor may also be... 

It should be noted that there are cases in which some selectivity will be lost in choosing a semi-batch mode over a simple batch reactor. If the desired product decomposes by a consecutive reaction, the yield will be higher in the batch reactor [177]. If, on the other hand, the reactants are producing by-products by a parallel reaction, the semi-batch process will give the higher yield. In any case, if the heat production rate per unit mass is very high, the reaction can then be run safely under control only in a semi-batch reactor. 

The programs are as follows BATSEG for a simple batch reactor, SEMISEG for a semi-continuous reactor that fills up and becomes continuous and COMPSEG for the complex reaction in a semi-continuous reactor. This example was developed by J. Baldyga., Dept of Chem. and Proc. Eng., Warsaw University of Technology, Poland. 

The maximum conversion of reactants which can be achieved in an isothermal batch reactor is determined by the position of thermodynamic equilibrium. If this conversion is regarded as unsatisfactory, the use of a simple batch reactor may be abandoned in favour of a reactor which permits removal of products from the reaction mixture. Alternatively, the reactor temperature may be changed to obtain a more favourable equilibrium however, this may result in an unacceptable reduction in the net reaction rate. Such conflicts are often resolved by the use of optimisation procedures (see Sect. 8). 

Then we switched topics completely to consider the chemical reactors that have always dominated the chemical engineering industries. These are extremely complicated and appear to have little relation to the simple batch reactors that you have seen previously. 

An interpretation of batch or flow reactor data is used to fit an empirical rate expression. For example, in a simple batch reactor, concentration is measured as a function of time. Once the experimental data are available, two methods can be used to fit a rate expression. 

Batch Reactor Bach reactors are easy to scale-up. The conversion of sugars with yeast in a simple batch reactor can achieve 75 to 95% and final ethanol concentrations of 10-16 vol.%. The productivity is usually 1.8 to 2.5 g of ethanol/1 h. Recycling the yeast can reduce the initial yeast growth period and increase the productivity. Due to low productivity and high operation costs, the batch reactors were replaced by continuous reactors. 

Three forms of the reactor operator, R(Y), are shown in Figure 3. These are generally differential operators which operate on each monomer and polymer species to describe the effects of accumulation and the physical processes which move material in and out of the reactor or reactor element. The concentration of a specific species is given by the variable Y. In a simple batch reactor, the reactor operator, RB, is merely defined as the rate of accumulation of a certain species with time per unit volume of reactor—i.e., the rate of change of concentration of the species. 

Comma, P. J. Beck, A. K. Seebach, D., A Simple Batch Reactor for the Efficient Multiple Use of Polymer-bound a,a,a ,a -Tetraaryl-l,3-dioxolane-4,5-dimethanol Titanates in the Nucleophilic Addition of Dialkylzinc Reagents to Aldehydes. Org. Process Res. Dev 1998, 2,18. 

Many batch experiments are of course not conducted in reactors as elaborate as that described above. When centrifuge tubes or Erlenmeyer flasks are used as simple batch reactors, mixing is normally accomplished by vor-icxing, reciprocal shaking, or end-over-end shaking in the case of tubes or by rotational or wrist-action shaking in the case of flasks. 

The simple batch reactor for homogeneous reactions is the most common type. From this kind of reactor, many kinetic data have been obtained. AU the reactants are charged in at the beginning of the reaction, with no mass transfer occurring until the reaction is complete. Examples of batch reactions are the ammonolysis of nitrochlorobenzenes, hydrolysis of esters, and polymerization of butadiene and styrene in aqueous suspension. These will be treated in more detail in later chapters. 

For a simple batch reactor, the fractional conversion of metal-ion is given by ... 

The simple batch reactor was considered in Chapter 4, A modified version in which the electrolyte is recirculated, however, is the preferred mode of operation in the electrochemical industry because it provides flexible batch volume and also enhances the mass transfer characteristics of the cell due to circulation. Further, with recirculation, the reactor can be operated either in the plug-flow or mixed-flow mode. We consider all three cases here along with a few other common modes of operation. 

This is the simple batch reactor control problem (see Example 2.10, p. 45) for which the augmented functional is... 

APPENDIX 4 — ASSESSING FIRE AND EXPLOSION HAZARDS IN A SIMPLE BATCH REACTOR (See Figure 7.1, page 127)... 

The simple batch reactor generally consists of a cooled, agitated mixing tank designed for operation at ambient pressure. Figure 3.1 shows a type of a simple batch reactor arrangement. There are four basic operating steps for this type of reactor used in alkylphenol service. 

FIGURE 3.1 Flow sheet of simple batch reactor. 

The complex batch reactor is a specialized pressure vessel with both excellent heat transfer and gas-liquid contacting capability. As a result, the lower-molecular-weight olefins (i.e., C4) may be processed, higher concentrations of olefins may be utilized, and the more complex di- and tri-alkylations may be carried out in addition to more efficient monoalkylations. Despite a significantly higher investment as compared to the simple batch reactor, the more varied and powerful capabilities of the complex batch reactor are causing them to become more common in the industry. Figure 3.2 illustrates a flow sheet of the complex batch reactor. 

The operating steps are the same as for the simple batch reactor. However, a pressure letdown step to a flare may be included at the completion of the reaction to bum off unreacted olefin or trace hydrocarbons. These reactors can operate at phenol to alkene mole ratios as low as 0.3 1 by designing for positive pressures in the range 30-300 psig. The use of more highly selective catalyst systems for ortho alkylations is also ideal with this reactor type. 

Throughout this process, there will be tradeoffs between the levels of detail included in the different aspects of the model. For example, in a simple batch reactor model, one can include thousands of chemical species and reactions, whereas in a detailed three-dimensional fully coupled model of fluid flow, heat transfer, and chemical reactions, one might be limited to less than 20 chemical species and a similar number of reactions. With continuous advances in both computational hardware and... 

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