Batch adiabatic

Figure 1.7 Temperature change for a batch adiabatic reaction.

Finely dispersed catalyst particles in a bed are used to promote the irreversible nth order gas-phase reaction in a batch, adiabatic reactor of constant volume... 

An Isolated System does not exchange matter or energy with the surroundings. Thermodynamically it tends to the state of thermodynamic equilibrium (maximum entropy). An example is a batch adiabatic reactor. 

Figure 6-5a Concentration versus time in an adiabatic batch reactor.

Figure 6-5b Temperature versus time in an adiabatic batch reactor. Fig ure 6-5. Simulation of a non-isothermal batch reactor.

Section 1.5 described one basic problem of scaling batch reactors namely, it is impossible to maintain a constant mixing time if the scaleup ratio is large. However, this is a problem for fed-batch reactors and does not pose a limitation if the reactants are premixed. A single-phase, isothermal (or adiabatic) reaction in batch can be scaled indefinitely if the reactants are premixed and preheated before being charged. The restriction to single-phase systems avoids mass... 

Example 7.6 Suppose a liquid-solid, heterogeneously catalyzed reaction is conducted in a jacketed, batch vessel. The reaction is A B. The reactants are in the liquid phase, and the catalyst is present as a slurry. The adiabatic temperature rise for complete conversion is 50 K. The reactants are charged to the vessel at 298 K. The jacket temperature is held constant at 343 K throughout the reaction. The following data were measured ... 

The temperature rise due to this exothermic reaction then approaches the adiabatic temperature rise. The final steady state is always characterized by conditions T = T, and c = 0. A batch reactor, in which a zero order reaction is carried out, always has a unique and stable mode of operation. This is also true for any batch and semibatch reactor with any order or combination of reactions. 

A semi-batch reactor is used to convert reactant, A, to product, B, by the reaction A —> 2B. The reaction is carried out adiabatically. The reaction kinetics are as before... 

The liquid phase hydrolysis reaction of acetic anhydride to form acetic acid is carried out in a constant volume, adiabatic batch reactor. The reaction is exothermic with the following stoichiometry... 

Figure 5.15. The adiabatic batch reactor with variables of concentration and temperature.

BATCH HYDROLYSIS OF ACETIC ANHYDRIDE EXAMPLE OF REACTION WITH HEAT EFFECTS UNDER ADIABATIC CONDITIONS... 

There are a variety of limiting forms of equation 8.0.3 that are appropriate for use with different types of reactors and different modes of operation. For stirred tanks the reactor contents are uniform in temperature and composition throughout, and it is possible to write the energy balance over the entire reactor. In the case of a batch reactor, only the first two terms need be retained. For continuous flow systems operating at steady state, the accumulation term disappears. For adiabatic operation in the absence of shaft work effects the energy transfer term is omitted. For the case of semibatch operation it may be necessary to retain all four terms. For tubular flow reactors neither the composition nor the temperature need be independent of position, and the energy balance must be written on a differential element of reactor volume. The resultant differential equation must then be solved in conjunction with the differential equation describing the material balance on the differential element. 

ILLUSTRATION 10.1 DETERMINATION OF REQUIRED REACTOR VOLUMES FOR ISOTHERMAL AND ADIABATIC OPERATION IN A BATCH REACTOR... 

We now consider operation of the batch reactor under adiabatic conditions. We will assume that we need not worry about reaching the boiling point of the liquid and that the rate of energy release by reaction does not become sufficiently great that an explosion ensues. 

Pure phosphine is to be admitted to a constant volume batch reactor and allowed to undergo decomposition according to the above reaction. If pure phosphine enters at 672 °C and the initial pressure is 1 atm, determine the times necessary to decompose 20% of the original phosphine for both isothermal and adiabatic operation. 

The standard heat of reaction is — 11.63 kJ/mole. Determine the times necessary to achieve 90% conversion in a constant volume batch reactor under adiabatic conditions and under isothermal conditions. 

Alt batch decomposed exothermally, then detonated at 220°C, dining distillation at 160°C/2.5 mbar. No cause was found, and similar batches had previously distilled satisfactorily. The multiple N-N bonding would tend to cause instability in the molecule, particularly in presence of heavy metals, but these were absent in this case [1]. It is shock sensitive (probably not very) [2], Benzotriazole is an endothermic compound (AH°f (s) +249.8 kJ/mol, 2.1 kJ/g) and this energy on release would attain an adiabatic decomposition temperature approaching 1100°C, with an 18 bar pressure increase in the closed system [3],... 

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