Batch Isothermal Perfectly Stirred Reactor

Knowledge of these types of reactors is important because some industrial reactors approach the idealized types or may be simulated by a number of ideal reactors. In this chapter, we will review the above reactors and their applications in the chemical process industries. Additionally, multiphase reactors such as the fixed and fluidized beds are reviewed. In Chapter 5, the numerical method of analysis will be used to model the concentration-time profiles of various reactions in a batch reactor, and provide sizing of the batch, semi-batch, continuous flow stirred tank, and plug flow reactors for both isothermal and adiabatic conditions. 

The concept of a batch reactor assumes that the reaction is instantaneously charged (i.e., filled) and perfectly homogenized in the reactor. Also, its temperature is immediately adjusted to that of the heat transfer medium. Therefore, the chemical reaction takes place at the temperature of the heat transfer medium under perfect mixing. The process is stopped as soon as the degree of conversion is achieved. 

When larger sizes are required, the design may include multiple units of batch reactors arranged in parallel. 

In small industrial pilot plants, a batch system may be employed for preliminary information. Also, batch reactors can be used in these plants to obtain small quantities of the new product for further evaluations such as purity, yield, and sales. At the industrial level, batch 

An important purpose of agitation or mixing is to bring a number of materials together in a physically homogeneous mixture. Two or more fluids are either blended or dispersed as emulsions fluids and finely divided solids are dispersed as suspensions, gases dispersed as fluids, or soluble substances dissolved. Mixing of process fluids is reviewed in Chapter 7. 

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Batch isothermal perfectly stirred reactor (the reaction mixture is at equilibrium with the heat transfer medium). 

Example 9.11 Which type of isothermal reactor would produce the narrowest possible distribution of chain lengths in a free-radical addition polymerization continuous stirred tank reactor (CSTR, or backmix), batch (assume perfect stirring in each of the previous), plug-flow tubular, or laminar-flow tubular ... 

An ideal batch reactor is a perfectly stirred tank of constant volume with no mass transfer from or to the outside. There is a single residence time, which is simply the duration of the reaction. Generally, a batch reactor is operated isothermally and therefore the reaction temperature may be considered as an independent variable. 

Reactor design usually begins in the laboratory with a kinetic study. Data are taken in small-scale, specially designed equipment that hopefully (but not inevitably) approximates an ideal, isothermal reactor batch, perfectly mixed stirred tank, or piston flow. The laboratory data are fit to a kinetic model using the methods of Chapter 7. The kinetic model is then combined with a transport model to give the overall design. 

Example 9.12 Consider the isothermal, free-radical batch polymerization of a monomer with [M]o= 1.6901 gmoI/L and [7]o= 1.6901 x 10 gmol/L. At the reaction temperature, k kt = 26.1 L/mol/s and 4.369 x 10 /s. This particular polymer terminates by disproportionation ( = 2). Neglect chain transfer. Assume perfect reactor stirring and/= 1. Because this reaction is carried out in a rather dilute solution, volume change is negligible. Calculate and plot x , ,x , ,and/ versus conversion for this system. 

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