Exercises proposed reactors

Calculate the volume of the CSTR under the same conditions. 

Plot the curve of reaction rate and conversion as a function of volume. 

If the density of the catalyst is 0.8 g/cm, calculate the ratio rate/mass Calculate the amount of mass required to achieve the same conversions of the item 3. 

Is it possible to determine the average residence time in each reactor Calculate and compare the space-time values. 

2 Summarize the residence times to the batch system in CSTR and PFR, considering the different cases  

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For a given system, the necessary requirements for any proposed reactor design are that the desired capacity, selectivity, and purity be achieved. The exercise should also include pertinent aspects of environmental load and safety. 

In the previous section we indicated how various mathematical models may be used to simulate the performance of a reactor in which the flow patterns do not fit the ideal CSTR or PFR conditions. The models treated represent only a small fraction of the large number that have been proposed by various authors. However, they are among the simplest and most widely used models, and they permit one to bracket the expected performance of an isothermal reactor. However, small variations in temperature can lead to much more significant changes in the reactor performance than do reasonably large deviations inflow patterns from idealized conditions. Because the rate constant depends exponentially on temperature, uncertainties in this parameter can lead to design uncertainties that will make any quantitative analysis of performance in terms of the residence time distribution function little more than an academic exercise. Nonetheless, there are many situations where such analyses are useful. 

Exercise 7,1.7, The only available storage tank is of 10,000 1 capacity. It is therefore proposed to start up the reactor as in the previous questions and to start filling up the storage tank at such a time that when it is just filled, the mean concentration of A in it is 6% of the feed concentration. What volume of the process stream would have to be wasted under this plan of operation ... 

Exercise 7.7.3. It is proposed to carry out a reaction 2A P 4- g in one or more stirred tank reactors at a uniform flow rate of 125 cu ft per hr. The initial concentration of A is 3 Ib-mole per cu ft and that of P and Q is zero. The velocity constant of the forward reaction is 12 ft (lb-mole) hr , and the equilibrium constant has a value of 16. If the final concentrations of P and Q are to be 85 % of the equilibrium values, what size of vessel will be needed if only one is used If the available vessels are limited to 5% of the capacity of the single vessel, how many smaller vessels will be needed for the same conversion when operated in series ... 

Exercise 9,5,4, Laboratory experiments on the dehydration of ethyl alcohol indicate that the reaction, C2H5OH —> C2H4 + H O, is second order with respect to the alcohol concentration. The rate constant is 0.52 1 gm-mole" sec at 150 C. It is proposed to construct a small scale tubular reactor which will operate at 2 atm and 150"C to give 35% conversion of the alcohol when the feed rate is 9.9kg/hr. If the reactor has a diameter of 10cm, what length will be required Ideal gas behavior and piston flow through the reactor may be assumed and... 

An extrapolation of the results of the previous sections to consider the case of a power producing reactor is certainly premature, due to the existing uncertainty on a number of assumptions that have been made. However an exercise in this direction could be useful in order to gain a qualitative acquaintance with the nature of the physical and engineering problems involved. The most surprising result is that, it is possible to foresee D- He reactors with power densities at least of the same order of that of currently proposed D-T reactors. ... 

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