In this video we're going to practice simulating a process in which we need to design a reactor
and a separation unit for the specific process of obtaining biodiesel from soy bean oil.
We want to react soybean oil with methanol to create biodiesel and glycerin, and we're
given specific parameters for the amounts of each of these components, and certain temperatures
and pressures that we're going to operate at, and this is known as a transesterfiication
reaction, and so we could look up this information in published articles and pull out information
in terms of operating conditions.
We're told that we're going to do this in a reactor that's going to use some kind of
agitation and a specific amount of power, and that we're going to obtain an 83% conversion
with respect to the soybean oil.
Now obviously there's other information we need, such as our centrifuge that we're going
to use to separate out most of the biodiesel and soybean oil from the other products, as
well as how much power that's going to be consumed from this.
Now this is information that we would probably gather through hand calculations, or other
information that we've obtained for this type of equipment.
A little bit of useful information that we're going to need for our simulation is parameters
regarding the soybean oil, as well as biodiesel, and the sodium methoxide that's used in this
process.
So the first place to start is opening SuperPro Designer, and we're going to create a new
file, and we're going to operate in batch mode.
This will give us a blank worksheet, and always the first thing to do is set our components
that we're using in our list, so we go to "Tasks", "Pure Components", "Register Edit",
and we're going to make sure that we use all components that are in this process.
So we're going to add methanol, and just register that in our data base.
We could type in soybean, and soybean oil is here, so we add that , and it's missing
a vapor pressure, but if you recall that's information that we we're given in the problem
statement, so for soybean oil we're going to click on the ""View Edit Properties" and
we're going to change the molecular weight to 885.45, as well as the pressure to 4.7
bar.
So then we're going to add sodium methoxide, and you could see that it's not in here, so
we're going to go to the wand and create a new component.
So we type in sodium methoxide and we click on the edit properties for sodium methoxide
so that we could enter in certain things.
Now we could enter the actual formula, but more importantly we need to add in information
such as the molecular weight, 54.02, the density, and for density we go to the temperature dependent
tab, and we were given a density of 2,043 grams per liter, so we get rid of the b component
so that it's not temperature dependent.
We go back to physical and the normal boiling point was given at 68, the critical temperature
as 234, and the critical pressure as 26.69, and click OK.
Now we do the same thing for our biodiesel.
That is all our components, we click OK to exit.
Now for this process we're going to want to operate with a CSTR, some kind of continuous
reaction, so let's go to the unit procedures, we go to continuous reaction, we'll go to
stoichiometric, and a CSTR, we'll add that to our sheet.
The other thing that mentioned in the problem statement was the use of a centrifuge.
Go back to unit procedures, we'll go to centrification, we'll use a decanter, so we have our two pieces
of equipment, we need to add our streams, so if we click on the stream button up here
we'll add two inlets into our reactor, we have to use the default one which is signified
here by this empty arrow, so we'll use one outlet that goes straight into our centrifuge,
then we're going to use the two outlets up top for our centrifuge, and you could look
up the information on specific pieces of equipment to see what the default values for each of
these arrows would be.
We have our streams, it's important to designate what's in our streams.
So let's click on our first streamline.
If we double click it will open up a composition window.
This is where we can enter in the specific components that are coming in to our reactor,
and in what amounts.
Sometimes it matters whether or not they're coming in as a top stream or a bottom stream,
in this case we're not going to care.
So let's add our one stream that contains methanol, it also contains a sodium methoxide,
it's used as a catalyst in this process, and then we're going to add water.
The water's already been added, so we have methanol, sodium methoxide, and water.
Now we could either type in composition percentages, or actual flow rates, and that's what I prefer
in this case, so we click on ingredient flows, and we could type in based on this statement
how much is coming in to our process, and then we're going to set the temperature of
the stream to 42.3 degrees Celsius, and our pressure to 64.7 psi.
Everything is designated for the stream, we click OK.
Now we're going to do the same thing for the second stream, and based on the problem statement
this is the information I've typed in, flow rate of soybean oil, as well as the temperature
and pressure, and click OK to save.
So we designated our two components into our reactor, now we have to decide what our reactor's
going to do.
So let's right click on the reactor and click on "Operation Data", that will open up the
following menu.
So in the problem statement we we're told that it was going to use a specific amount
of power for agitation, and you could see that power consumption over here can be designated.
We we're told 1.4 kW per meter cubed.
Now under the "Reactions" tab the more important aspect of this we need to type in what the
extent is, which was given from literature, and it was based on a reference component
of soybean oil.
So we have that information entered, now we could go to the stoichiometry of our reaction,
which is this flask up here, and make sure we set up what goes in, which is methanol
and soybean oil, and what comes out, which is biodiesel and glycerol, which is not entered
in here, as something I totally forgot to add.
So let's go back and enter in glycerol.
It's pretty easy to go back and add this, we could just go back to our "Tasks", "Pure
Components", "Register", and type in "Glycerol" to see if it's here, which it is, and we could
continue.
So let's go back to where we were, "Operation Data", and the "Reactions" tab.
So go back to our stoichiometry, where we have methanol and soybean oil entering, which
produces biodiesel and glycerol.
Importantly we want to enter in the stoichiometry, so we click on this molar button, and we could
say that we're going to enter in 3 moles of methanol per mole of soybean oil, which produces
3 moles of biodiesel and 1 mol of glycerol.
So that's our stoichiometry, and that's all we really need in our reactor.
So we need to do the same kind of thing for our centrifuge, so right click "Operation
Data", and we want oil/fat removal since we're producing an oily substance.
We're going to keep everything else as a default, that's information you could look up for the
specific system, but we'll keep it as default for here.
Click on material balances and we can change certain parameters to what was designated
in the problem, such as the oil concentration, and the oil strength, as 850 grams per liter.
We could also say that we want the centrifuge to remove 99.99% of the biodiesel and the
soybean oil, and the last thing is our power consumption, so clicking on the "Utilities" tab allows
us to enter in our power consumption.
We can set by user, and then we could type this in as 18.9 kW, and click OK.
One of the important things to look at also, which we might not have done, is going back
to the reactor under the operating conditions, you could see that the heat transfer agent
use is chilled water, and since we're working at an elevated temperature we want something
that's going to be able to heat the system up if necessary.
Well let's double click on steam.
Therefore now we could operate adiabatically and use steam as a heating agent.
Our whole system should be defined at this point, click on the material balances, and
as long as there are no errors they've done them successfully and converged, again it's
important to check all those parameters, just because it converges doesn't mean that you've
set this up properly, so if we take a look at our two exiting streams we could double
click on them, and you could see that we've removed a ton of the biodiesel and soybean
oil in this stream, whereas in the other stream there's very little of those two components
and a lot of glycerol and methanol.
At this point you would design some kind of system to split the glycerol and methanol
apart, and some of the other impurities, as well as in this system what we could do is
you could see that there's still a lot of soybean oil that's unreacted, so we could
somehow separate that from the biodiesel and recycle it back into our reactor to get a
higher overall conversion.
We'd also want to remove some of the glycerol, methanol, and other impurities that are in
here.
The last thing you could do is always click on "Reports" and "Materials and Streams",
and " Overall Report Window" that gives you information about each stream and operating
unit.
On thing you can see from this is that our batch time is 4 hours, so as we go around
our entire process and start collecting information on how long each piece of equipment runs, and
whether or not we'd be operating in a batch or a semi-batch, or a continuous manner.
This would allow us to produce a Gant chart which gives us an idea of the scheduling of
each piece of equipment, and the overall operating time to produce a certain amount.
That's definitely something you would need to consider.
So hopefully this gives you a little bit of a flavor for setting up a reactor, some separation
units, and calculating material and energy balances for a straight forward reaction such
as this one.