SuperPro Designer: Modeling a Batch Reactor

SuperPro Designer: Modeling a Batch Reactor


The goal of this screencast is to show you
how to use a reactor simulation in SuperPro Designer to solve problems involving reactions.
So we’re going to use the following example in which we’re forming acid from salicylic
acid and acetic anhydride, and you’re given reaction stoichiometry, as well as the kinetic
rate expression and other relevant data for our reactor system. Our goal is to determine
the amount of salicylic acid after two hours of this reaction. So here’s our form for SuperPro, and I’ve chosen a batch setup since we’re doing a batch reaction. So the first thing
to do is to designate our components that are going to participate in this simulation.
So we could go to pure components under tasks and register, and we could look for the components
that are involved, the salicylic acid, acetic anhydride, acetic acid. Here acetic acid is
available, and we click on register and add it to our list. However, the other three components
are not, so we have to create them. So if we go to this magic want up here we could
type in the name of the components that we’re using, and we just click OK, and so I’ll do
this for the other two, and now we have our list of components. Since they’re not in the
original data base that we’re using we have to add certain properties to them to help
us solve this system. So if we click on salicylic acid, either twice or through the edit button
in the top right, we could open up certain properties that we’d like to enter in. So
we go to the physical constants and we could type in a molecular weight of 138.11, and
a normal boiling point of 211. We could type in other physical properties, but for this
simulation it’s not necessary. So we could go ahead and click on the physical t dependent
since we do need the density, and we’re going to use a density of 1440, and a b value of
0, and say that it’s not temperature dependent in this simulation, and click OK. We’re going
to go ahead and do the same thing for aspirin, using molecular weight of 180.16, and a boiling
point of 140, again we go to the physical t dependent tab and click a density of 1400,
again these are in grams per liter, and say it’s not temperature dependent, so we set
a value of 0, and then lastly the acetic anhydride. It’s important as you enter in this information
to make sure you’re using the right values for the right units, and since SuperPro has
built in units with each of these it’s good to check those. So now we’ve entered in all
our components, so we could click OK. So the next thing to do is go to unit procedures
and enter in our reactor. So we’ll go to batch vessel and reactor and add it to our sheet.
So now we could also start connecting lines, this top line up here is our default input,
and the bottom one on the right side is our default output. We’re going to want to double
click on these lines and add the components to each line. So we know we have acetic anhydride
coming in, so we add this to our line, and we have salicylic acid coming in. So at this
point we want to set our mass composition for our flow rate, and in this case in the
problem statement we’re told that they’re entering at an equal molar ratio. So we’ll
click and make sure that we have the button for mass composition entered, so using the
molecular weights and equal molar ratios we could calculate what the mass fraction of
each we’d be entering, and we could enter that in here. Now this button up here also
can use specific concentrations of components to calculate concentrations of other components
if there are multiple species. So use that when you know the concentration
of a component. So the other thing we want to do is set the volumetric flow, we’re told
that it’s 2000L per batch, and we’ll use the temperature and pressure and everything else
set as default. So we set our incoming line, we now want to set the operations for the
reactor, so if we double click on the reactor itself we have our whole list of available
operations we could use for this reactor. So we want to charge the system, so we click
on charge and add it, and after charging we want to heat the reactor, and then react using
kinetic information, and then lastly transfer all of it out. So now what we’re going to
do is right click on the reactor, go to operation data, charge 1, and start entering in information.
Now it’s really important that you click on charge using, and then set r line, we’re
telling the reactor what’s coming into it. The other thing we’re going to do is say that
our set up time is 0, and we’re going to calculate the process time based on our volumetric flow
rate entering into the system. It’s best to click on the units first, since that will
automatically change. So we’re going to use 2 meters cubed per second of volumetric flow
rate entering our process. So at this point there are obviously other tabs that we could use,
but for simplicity we’ll just go to the next operation, which is our heating, and we’re
told in the problem statement that our final temperature is 350 K, we also are going to
use our default heating utility of steam, with 90 percent efficiency, and a heating
rate of 1 degree Celsius per minute. We click on the next button down here to go to our
next operation, and this is where it starts getting interesting. We have our reaction.
So let’s set our operating temperature for the reaction at 350 K, we’re going to select
steam as the heat transfer agent, so going down here double clicking on steam, so that’s
going to control the temperature of the reactor, and then our reaction time of two ours, since
that is what the problem statement asked us to determine. We have to set what our reaction
looks like, let’s click on the reaction tab up top, and this icon that looks like a flask
allows us to edit the stoichiometry. We know that acetic anhydride and salicylic acid are
our reactants, and our products are acetic acid and aspirin. Now for the stoichiometric
coefficients you could either use mass of molar, the molar coefficients here and here
should all be 1 to 1. So at this point we click OK, and then we want to enter in the
kinetic information. So we could click on the r. We’re told what the reaction rate is,
which is 0.0059 for our k value, and then we’re told it’s first-order in acetic anhydride
and salicylic acid. So if we go over to the reaction order for acetic anhydride we click
on 1, for sylicylic acid we click on 1, and that’s it for our reaction rate, and you could
see that our reaction molar stoichiometry is shown down below, so we could double check
it, and if we cared we could enter in what our reaction heat would be so that we could
start doing our energy balances. Since we’re just concerned with our material balance on
the statement we’ll keep it basic. Last thing we have to react is our transfer out, so again
click on the next operation, and it tells us that aspirin there’s no rate reference
component, so I’ve missed the fact that under r we have to say that our rate is referenced
to some component, since our k value is specific to something. So this is for aspirin. So that
should fix our error. So lastly on transfer out pick our line, which is our product, we’re
going to set it, our set up time is again 0, and then we’re going to say our process
time is calculated based on our volumetric flow rate, which we said was 2 meters cubed
per second. So you see that there’s no next operation tab, so we’re just going to click
OK, we have everything designated. This point I would save the file, and then click “Solve
ME Balances”, and as long as no errors showed up then you have at least the proper setting
to run your simulation, it doesn’t necessarily mean it’s correct, so it’s always good to
check the values that you’re getting, but we’re interested in is looking at the product
stream so we could double click on that, and you could see what comes our of our reactor
after two hours of our reaction. You see what the temperature and pressure are, you could
also see the flow rates. Based on that information we could see that our salicylic acid, roughly
6 kilograms per batch, and we started with 1450 kilograms, so we could determine how
much reacted, and obviously answer the question of how much was left. So hopefully this gives
you a basic idea of how to set up a reactor, you could see that there’s a lot of tabs and
buttons to enter in more information as you get more precise.


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