Exercises

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some tasks on kinetics, RTD, reactions and reactor design:

1. The kinetics of a 'simple isothermal homogeneous fluid reaction A + ... -> products' has been measured in a CSTR by changing the residence time. (Separation method: the concentrations of the other components are kept constant). The data is: C_A,0 = 1 (mol/l)
   

   tau (sec)	0.1	0.5	2	12	90
   Cstat(mol/l)	0.92	0.73	0.5	0.25	0.1

   C_stat = stationary concentration in the CSTR
   Calculate: conversion of A, reaction rate r_(A), reaction order concerning A, and rate constant.
   take my help
   
   
2. * Can you solve the following task by computing and simulation: an irreversible first order consecutive reaction A -> B -> C with the 1st order constants k1 = 1 (1/sec) and k2 = 0.1 (1/sec) with C_A0 = 1 (mol/l) is carried out in a batch STR and/or a TFR and alternatively in a CSTR. Which B_max can be reached at which space times in each (fundamental) type ? Why shouldn't you choose 98 % conversion of A ? First give an overview of how you are going to manage it ! 'my proposal'
   
   
3. * Find the equilibrium concentrations for a (both sides) 1st order reversible reaction A<->B with k1 = 1 (1/sec) and k2 = 0.1 (1/sec) and with C_A0 = 1 (mol/l) in a batch reaction. How long does it take till 90 % of the equilibrium concentrations are reached. Solve it by simulation and computation! First give an overview of how you are going to manage it ! 'procedure'
   
   
4. * Can you, starting from the differential equation(s), derive the logistic equation(s) for the real-time simulation of an autocatalytic reaction of the type A-> B with r = k C_A * C_B
   a.) as batch reaction and
   b.) running in a CSTR.
   How will the plots look like ? Do you know autocatalytic reactions ? What about the reactor choice ? First give an overview with sketches etc. of how you are going to manage it ! For the concrete task take: k = 1 (l*mol^-1*sec^-1), C_A0 = 1 (mol/l), C_B0 = 0 (mol/l) (??), mass flow: 0.5 (l/sec), conversion U = 99 %. Try to carry out the simulations and the optimization. 'first aid!'
   
   

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see some simple 'realtime' simulations on (homogeneous) reaction kinetics :

1. Compare a 1st order reaction with a 2nd order reaction see snapshot !: At the value of c = 1 mol/liter there is for c¹ and c² an 'intersection' that influences the value of r(1) and r(2) at constant numerical values for k (remember r is the product of k and cⁿ). Below this intersection the rate of the 1st order reaction is faster than that of the second order reaction and vice versa for the section over c = 1. You have to pay a bit attention when regarding the concentration curves, higher values mean a slower 'decay'. You need these facts for the discussion of parallel reactions. Regard the same simulation but showing additionally the reaction rates (next term in the catalogue list!) scroll down to next image: see snapshot !
   
   
2. look at a simple consecutive reaction A-> B-> C and think about the task of getting a maximum of Product B (reactor type) :see snapshot.
   
   
3. look at a simple (irreversible) competitive parallel reaction A-> B and A-> C with 1st order and 2nd order branches, think of the reactor choice : see snapshot
   

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see some 'realtime' simulations of the RTD of basic reactors :

1. RTD of one and two CSTRs see static snapshot of simulation
2. RTD of an ideal TFR snapshot
3. RTD of a series of one TFR and one CSTR snapshot
4. RTD of a CSTR with 'bypass' snapshot ( 2 pics)
5. RTD of a 'cascade' of n equal vessels snapshot
6. RTD, comparison of a laminar TFR with a series combination of ideal TFR and CSTR snapshot

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tasks concerning the heat balance:

1. The simulation of a 1st order (exothermal) reaction running in an adiabatic STR --> see snapshot .When starts the solvent to boil? Can you describe the procedure of solving the heat and material balance (quasi 'simultaneous').
   
2. Take the same reaction as above but 'carry it out' in a reactor with a thermostatting jacket.
   
3. How can you calculate and visualize the course of temperature with time in an adiabatic STR ? already well known!!

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