Batch reactors second order irreversible

The time necessary to achieve 90% conversion in a batch reactor for an irreversible first-order reaction in which the specific reaction rate is 10 s is 6.4 h. For second-order reactions we have... 

This lime is the reaction time t (i.e., Jr) needed to achieve a conversion X for a second-order reaction in a batch reactor. It is important to have a grasp of the order of magnitudes of batch reaction times. Jr, to achieve a given conversion, say 90%, for different values of the product of specific reaction rate. k. and initial concentration. AO-. Table 4-1 shows the algorithm to find the batch reaction limes. Jr. for both first- and a second-order reactions carried out isothermaliy. We can obtain these estimates of Jr by considering the first- and second-order irreversible reactions of the form... 

Consider the consecutive second order, irreversible reactions occurring in a batch reactor [6] ... 

Table 5-2 gives the oMer of magnitude of lime to achieve 90% conversion for first- and second-order irreversible batch reactions. Flow reactors would be used for reactions with c/iaracferisO c reaction times, Jr, of minutes or less. 

Another question is important for the safety assessment At which instant is the accumulation at maximum In semi-batch operations the degree of accumulation of reactants is determined by the reactant with the lowest concentration. For single irreversible second-order reactions, it is easy to determine directly the degree of accumulation by a simple material balance of the added reactant. For bimolecular elementary reactions, the maximum of accumulation is reached at the instant when the stoichiometric amount of the reactant has been added. The amount of reactant fed into the reactor (Xp) normalized to stoichiometry minus the converted fraction (A), obtained from the experimental conversion curve delivered by a reaction calorimeter (X = Xth) or by chemical analysis, gives the degree of accumulation as a function of time (Equation 7.18). Afterwards, it is easy to determine the maximum of accumulation XaCfmax and the MTSR can be obtained by Equation 7.21 calculated for the instant where the maximum accumulation occurs [7] ... 

This is the most common mode of addition. For safety or selectivity critical reactions, it is important to guarantee the feed rate by a control system. Here instruments such as orifice, volumetric pumps, control valves, and more sophisticated systems based on weight (of the reactor and/or of the feed tank) are commonly used. The feed rate is an essential parameter in the design of a semi-batch reactor. It may affect the chemical selectivity, and certainly affects the temperature control, the safety, and of course the economy of the process. The effect of feed rate on heat release rate and accumulation is shown in the example of an irreversible second-order reaction in Figure 7.8. The measurements made in a reaction calorimeter show the effect of three different feed rates on the heat release rate and on the accumulation of non-converted reactant computed on the basis of the thermal conversion. For such a case, the feed rate may be adapted to both safety constraints the maximum heat release rate must be lower than the cooling capacity of the industrial reactor and the maximum accumulation should remain below the maximum allowed accumulation with respect to MTSR. Thus, reaction calorimetry is a powerful tool for optimizing the feed rate for scale-up purposes [3, 11]. 

Repeat the analysis in Example A.2 for the differential equation describing a second-order, isothermal, irreversible reaction in a constant-volume batch reactor... 

From experiments in a constant volume batch reactor at 791K, it is known that the time required for a 50% increase in total pressure is 197 s. The initial pressure is 1 bar. The reaction is known to be second-order in acetaldehyde. Determine the volume of a plug flow reactor necessary to achieve 80% conversion of 120 L/min of pure acetaldehyde gas. The feed pressure is 1 atm. The reaction is essentially irreversible. The pressure drop along the length of the reactor is negligible. 

E5.2 A reaction A 2 R + S is carried out in a tubular reactor, and the reactant A is introduced with 30% of inert. The reaction is irreversible and of second order. The reactor of 0.2 L is isothermal, and the reaction occurs at 800 K and pressure of 10 atm. It is known that the outflow of the product R is 0.034 mol/s and the conversion was 10%. Calculate the reaction rate constant. If this reaction would be further carried out in a batch reactor, calculate the reaction time for the previous conditions. 

An irreversible second-order reaction A + B - C + D with rate equation (-r ) = kC Cg is carried out in a constant-volume batch reactor at constant temperature. The reactor contains 1 kmol/m of A and 2 kmol/m of B at the time of start-up. Variation of concentration of A with time is measured and reported in the table below. 

Program to design batch reactor/CSTR/PFR for second-order endothermic irreversible reaction operating at adiabatic condition... 

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