Acetone, Butanol, and Ethanol Fermentation
Prepared for:
Jaqueline Burgher
Separations 334
April 29th, 2016
Prepared by:
Group Project
Ryan Meech
Karissa Garcia
Jessica Leong
Jonathan Allyn
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Table of Contents I) History of ABE Fermentation ..........................................................................................3
II) Multicomponent Distillation .....................................................................................5
III) Methods of Equations ...............................................................................................8
IV) Assumptions ..............................................................................................................9
V) Hand Calculations ......................................................................................................15
VI) Pro II calculations ......................................................................................................19
VII) Pro/ll Manual .............................................................................................................28
VIII)Bibliography …………………………………………………………………………………………………………35
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Theory:
I) History of ABE Fermentation:
ABE fermentation is a process used to break down feedstock material into desired products. ABE
stands for acetone, butanol, and ethanol. This process uses bacteria to produce the above materials for
economical purposes such as biofuels production. We can trace this process back to 1861 when a
scientist by the name of Louis Pasteur first used fermentation to produce butanol. The more common
use for ABE fermentation began in 1916 when it became an industrial product during World War l1.
Chaim Weizmann used the process to mainly produce Acetone. ABE fermentation presently is not used
in industry. The reason it is not used in industry is due to the growing petrochemical industry out
competing the need for the solvents and became more economically viable than ABE fermentation.
However, with the increased interest in finding renewable fuel sources, ABE fermentation is being
considered as a possible source for solvent production and biofuels.
Based on literature, ABE fermentation is started in a batch reactor where water, feedstock, and
bacteria are introduced. After fermentation, acetone, butanol, and ethanol are produced in a 3:6:1 ratio.
From the batch reactor, the feed stream is then fed into a series of distillation columns where acetone,
ethanol, and butanol are separated from water. The primary goal in this process is to recover butanol for
the production of biofuels. Acetone and ethanol are also valuable co-products that can be sold. The
target separation is to have a 98% pure stream of butanol. In order to achieve a purity of 98% butanol,
specific multiple component distillation theories were explored in order to build our system for the
optimal separation.
1 See reference 13
4
II) Multicomponent Distillation:
Multicomponent distillation is a process in which a feed stream containing various components is
separated, utilizing their individual chemical properties, to separate one stream into its base
components. A very common way to separate components is by preforming a flash distillation on the
mixture or components. Flash distillation is used to separate these components with very different
boiling points and is widely used in the petroleum industry. This process also incorporates the use of
comparable volatility between species. The inlet feedstock to be separated is composed of water,
butanol, acetone, and ethanol. These chemicals are all toxic except water, and a water waste stream
containing the remaining product that would be treated, recycled, and then disposed of properly. 2
Key components are necessary to identify for the distillation process. A heavy and light key
characteristic for the feed stream will be chosen, both of which can be either gas or liquid. In
multicomponent distillation, there will be a heavy and light key in each stream which are chosen to
represent the composition of the stream. For each stream, the more volatile component is defined as
the heavy key and the less volatile component is defined as the light key. For a single distillation column,
a balance must be performed to calculate the number of trays contained within the column. The
number of trays is used to increase the liquid/gas contact resulting in an improved separation. During
this process of separation, the light key will go above the tray and the heavy key will pool below the
tray. At the bottom of the column, a pool of liquid is maintained. Within the system, there is also a re-
boiler that heats up the liquid in the bottom of the column to keep the vapor from continuously
generating. The heated vapor then passes through the pooled liquid which causes a heat transfer from
the vapor to the liquid. When the heat transfer occurs, a fraction of the vapor condenses and combines
2 See reference 4
5
with the liquid on the tray. However, the condensation is richer in the less volatile components than
when it is contained within the vapor.
This ratio of condensate returned to the column to overhead product is called the reflux ratio. Some
of the causes for reflux rations are that: the column can have a minimum reflux ratio which is the
minimum required to achieve the separation that is specified including the limiting case of total reflux
where your reflux is infinite this would give you a minimum number of trays, but the rates of your feed
and the overhead and bottom products are zero. A higher reflux ratio means you can achieve a larger
separation with a lower number of theoretical plates. To design a proper distillation system, these
aspects have to be optimized taking into account the time, cost and general practicality for the system.
III) Methods and Equations:
There are methods that can help one understand how to determine the separation process and
understand how to calculate each component.
Fenske Method
The Fenske method, found below as equation one, helps to calculate the number of minimum plates
required in the distillation column which is needed to maintain an infinite reflux ratio.
𝑁𝑚𝑖𝑛 =
𝐿𝑛[ (
𝑋𝐷𝑖𝑋𝐵𝑖
)
(𝑋𝐷𝑗𝑋𝐵𝑗
)
]
𝐿𝑛 �̅�𝑖𝑗 − 1 (1.)
Where,
�̅�𝑖𝑗 = √𝛼𝐷𝑖𝑗𝛼𝐹𝑖𝑗 𝛼𝑁𝑖𝑗3 (2.)
Along with 𝑋𝐷𝑖 , 𝑋𝐵𝑖 corresponding to the mole fractions of the light key in the distillate (D) and the mole
fraction in the bottoms (B). Similarly, 𝑋𝐷𝑗 , 𝑋𝐵𝑗 correspond the mole fractions of the heavy key in the
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distillate and bottoms. �̅�𝑖𝑗 is a ratio of the light and heavy key volatilities at the stream temperature
where it is assumed that the volatility does not change much in a typical column, and therefore a
constant temperature.
Thusly expressed below,
�̅�𝑖𝑗 =𝛼𝑖
𝛼𝑗3.)
Underwood Method
The method used to determine the minimum reflux ratio is the Underwood method. In order for
this method to be valid for use, there must be constant molal overflow and the relative volatility for
each of the components must be the same. When Rauolt’s law is applied to the system, the Underwood
equation can be seen below:
4.)
Where q represents the number of moles of flow in a stripping section and can have a value of 1 for a
liquid at the bubble point, 0 for a feed at the dew point temperature or is superheated vapor and a
value less than 1 when a cold feed below the bubble point is fed. The α value in this equation
represents the relative volatility for the different zones and is described as:
5.)
Then φ is the Underwood parameter that is determined by a solver using equation 5 and equation 3
which is then determine as the equation shown below:
𝑉𝑚𝑖𝑛
𝐷= 𝑅𝐷𝑚 + 1 = ∑
𝛼𝑖𝑥𝐷𝑖
𝛼𝑖−𝜑 6.)
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Once all of the parameters are found, the minimum reflux ratio (RDm) can be found by:
∑𝛼𝑖𝑋𝐹𝑖
𝛼𝑖−𝜑= 𝑅𝐷𝑚 + 1 7.)
Number of Ideal Trays
The number of actual trays is found best by computer methods but can be empirically solved for
by the correlation based on systems with a constant relative volatility. This correlation is known as the
Gilliland correlation and is found below as figure 1:
This figure uses equation 7 along the x axis
8.)
8
Then uses equation 8 along the y axis
9.)
Feed Tray Location
The optimum feed tray location can be found by the Kirkbride equation below:
𝑁𝑟𝑒𝑐𝑡𝑖𝑓𝑦𝑖𝑛𝑔
𝑁𝑠𝑡𝑟𝑖𝑝𝑝𝑖𝑛𝑔
= [(𝑍𝐻𝐾
𝑍𝐿𝐾
) (𝑋𝐿𝐾,𝐵
𝑋𝐻𝐾,𝐷
)
2𝐵
𝐷]
.206
10. )
Where, NT refers to the number of trays above the feed tray, NB refers to the number of trays found
beneath the feed tray, B is the total moles found in the bottoms and D is the total moles found in the
distillate. The total number of trays can be found by a tray balance noted in equation 10:
𝑁𝑟𝑒𝑐𝑡𝑖𝑓𝑦𝑖𝑛𝑔 + 𝑁𝑠𝑡𝑟𝑖𝑝𝑝𝑖𝑛𝑔 = 𝑁𝑡𝑜𝑡𝑎𝑙 11.)
Where, (𝑍𝐻𝐾
𝑍𝐿𝐾
) = the ratio of mole fraction heavy key per mole fraction light key, 𝑋𝐿𝐾,𝐵
𝑋𝐻𝐾,𝐷 = the ratio of
mole fractions of light key in the bottoms per mole fraction of heavy key in the distillate, and B and D =
both molar flow rates of bottoms and distillate.
lV) Assumptions:
In order to simplify and make hand calculations possible, certain assumptions had to be made for
the multicomponent distillation columns. The following assumptions include:
Rauolt’s Law applies to each tray of the system
Ideal methods applied to each column : constant pressure, constant volume, adiabatic and
isentropic parameters
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The change in volatilities in negligible because they do not change much in each column
In order to achieve an approximate minimum reflux ratio, we can assume that the mixture is
pseudo binary
Meaning that only the moles of the light key and heavy key make up the feed, where the
product compositions can be calculated along with a vapor-liquid equilibrium curve
based on 𝛼𝐿𝐾 −𝐻𝐾
In order for the Fenske method to be valid, the relative volatility of the components are to be
assumed constant
Constant relativity for the Gilliland correlation
V) Hand calculations:
Method:
To perform the hand calculations, a mass balanced was used on the first column, under the
assumption of 97% recovery of the light key in the distillate, and of the heavy key in the bottoms in the
first column, 93% recovery in the second, and 98% recovery in the third. These percent recoveries were
determined from Pro II data. A sample mass balance on the first column for the distillate is shown
below:
𝐴𝑐𝑒𝑡𝑜𝑛𝑒 𝐵𝑎𝑙𝑎𝑛𝑐𝑒 (𝑚𝑜𝑠𝑡 𝑣𝑜𝑙𝑎𝑡𝑖𝑙𝑒) = 𝐹𝑇 ∙ 𝑥𝑖,𝑎𝑐𝑒𝑡𝑜𝑛𝑒 = 1 ∙ 𝑥𝑎𝑐𝑒𝑡𝑜𝑛𝑒 𝑖𝑛 𝑑𝑖𝑠𝑡𝑖𝑙𝑎𝑡𝑒
𝐸𝑡ℎ𝑎𝑛𝑜𝑙 𝐵𝑎𝑙𝑎𝑛𝑐𝑒(𝐿𝐾) = 𝐹𝑇 ∙ 𝑥𝑖,𝐸𝑡ℎ𝑎𝑛𝑜𝑙 = .97 ∙ 𝐹𝑇 ∙ 𝑥𝑖,𝐸𝑡ℎ𝑎𝑛𝑜𝑙
𝑊𝑎𝑡𝑒𝑟 𝐵𝑎𝑙𝑎𝑛𝑐𝑒 (𝐻𝐾) = 𝐹𝑇 ∙ 𝑥𝑖,𝑊𝑎𝑡𝑒𝑟 = .03 ∙ 𝐹𝑇 ∙ 𝑥𝑖,𝑊𝑎𝑡𝑒𝑟
𝐵𝑢𝑡𝑎𝑛𝑜𝑙 𝐵𝑎𝑙𝑎𝑛𝑐𝑒(𝑙𝑒𝑎𝑠𝑡 𝑣𝑜𝑙𝑎𝑡𝑖𝑙𝑒) = 𝐹𝑇 ∙ 𝑥𝑖,𝐵𝑢𝑡𝑎𝑛𝑜𝑙 = 0 ∙ 𝐹𝑇 ∙ 𝑥𝑖,𝐵𝑢𝑡𝑎𝑛𝑜𝑙
Where 𝐹𝑇 is the total flow rate over the stream in 𝑘𝑔−𝑚𝑜𝑙
ℎ𝑟, and 𝑥𝑖 is the initial mole fraction of the
component in the feed. The mass balance for column 1 was performed with the assumption that the
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light key was 0.97 percent in the distillate and the heavy key was 0.03 in the bottoms. Below is the mass
balance:
𝐴𝑐𝑒𝑡𝑜𝑛𝑒 𝐵𝑎𝑙𝑎𝑛𝑐𝑒(𝑙𝑒𝑎𝑠𝑡 𝑣𝑜𝑙𝑎𝑡𝑖𝑙𝑒) = 𝐹𝑇 ∙ 𝑥𝑖,𝑎𝑐𝑒𝑡𝑜𝑛𝑒 = 0 ∙ 𝐹𝑇 ∙ 𝑥𝑖,𝑎𝑐𝑒𝑡𝑜𝑛𝑒
𝐸𝑡ℎ𝑎𝑛𝑜𝑙 𝐵𝑎𝑙𝑎𝑛𝑐𝑒 (𝐿𝐾) = 𝐹𝑇 ∙ 𝑥𝑖,𝐸𝑡ℎ𝑎𝑛𝑜𝑙 = .03 ∙ 𝐹𝑇 ∙
𝑊𝑎𝑡𝑒𝑟 𝐵𝑎𝑙𝑎𝑛𝑐𝑒 (𝐻𝐾) = 𝐹𝑇 ∙ 𝑥𝑖,𝑊𝑎𝑡𝑒𝑟 = .97 ∙ 𝐹𝑇 ∙ 𝑥𝑖,𝑊𝑎𝑡𝑒𝑟
𝐵𝑢𝑡𝑎𝑛𝑜𝑙 𝐵𝑎𝑙𝑎𝑛𝑐𝑒(𝑙𝑒𝑎𝑠𝑡 𝑣𝑜𝑙𝑎𝑡𝑖𝑙𝑒) = 𝐹𝑇 ∙ 𝑥𝑖,𝐵𝑢𝑡𝑎𝑛𝑜𝑙 = 1 ∙ 𝐹𝑇 ∙ 𝑥𝑖,𝐵𝑢𝑡𝑎𝑛𝑜𝑙
This process was repeated for each of the three columns in our system. With the mass balance
complete and all of the stream compositions known, the bubble point temperature for each stream then
was calculated using the following equation:
∑ 𝐾𝑖𝑋𝑖 = 1 12. )
Where, 𝐾𝑖 = 𝛼𝑖 =𝑃𝑖𝑠𝑎𝑡
𝑃𝑡𝑜𝑡𝑎𝑙, Is the vapor pressures. 𝑃𝑖𝑠𝑎𝑡 was found by using the Antoine equation and
with an initial guessed temperature. The Antoine coefficients are also needed and are found in the cited
sources (Smith, Appendix B).. 𝑃𝑡𝑜𝑡𝑎𝑙 is the total pressure, and 𝑋𝑖 is the liquid mole fraction of species i in
the feed. An iterative process was used, adjusting the initially guessed temperature until the vapor
pressure conditions was satisfied.
Next, the dew point temperature could be calculated in a similar fashion with the equation:
∑𝑦𝑖
𝐾𝑖
= 1 13. )
Where, 𝐾𝑖 =𝑃𝑖𝑠𝑎𝑡
𝑃𝑡𝑜𝑡𝑎𝑙, and 𝑦𝑖 = 𝑔𝑎𝑠 𝑚𝑜𝑙𝑒 𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛 𝑜𝑓 𝑠𝑝𝑒𝑐𝑖𝑒𝑠 𝑖 𝑖𝑛 𝑡ℎ𝑒 𝑓𝑒𝑒𝑑 . The inlet temperature was
then adjusted by the same iterative process until the condition were satisfied. In addition, temperature
information could be solved for as well, such as the flash point temperature, which is represented by the
equation below:
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∑𝑋𝑖
𝐹(𝐾𝑖 − 1) + 1= 1 14. )
Where, 𝐹 = 𝑚𝑜𝑙 𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛 𝑜𝑓 𝑓𝑒𝑒𝑑 𝑣𝑎𝑝𝑜𝑟𝑖𝑧𝑒𝑑. Again, an iterative process was used to until the
condition was satisfied. Below is a table of the bubble point, dew point, and flash point temperatures for
each of the three feed streams into the column, along with the calculated volatiles for each column.
STREAM 1 STREAM 2 STREAM 3
BUBBLE POINT( ͦC) 100.9245 64.41 105.6
DEW POINT( ͦC) 106.9122 77.47 108.237
FLASH POINT( ͦC) 101.789 77.47 107.15
Α(LK/HK) 2.243111292 2.313600332 1.88709181 Table 1: Bubble Point, Dew Point, and Flash Point temperatures for each column feed stream throughout the system
The minimum number of plates was calculated for each column using the Fenske method
outlined in the theory section with equation 1. The same 𝛼 from the bubble, dew, and flash point
calculations were used in the calculation of the minimum number of plates contained in each column.
The minimum reflux ratio for each column was calculated using the Underwood method, as
explained in the theory section. Before calculations could be done, a value of q was needed to be
calculated. The value q characterizes a ratio of moles of liquid moving to the stripping section per mole
of feed. The q value can range anywhere between 1, for a saturated feed, and 0 for a vapor feed. These
q values were calculated; one for each column because each feed was composed of all liquids. An
iterative process was used to vary the value of 𝜑, in the which satisfied the conditions of where the
value of 𝜑 needed to be in between the volatilities of the light and heavy key. Once the Underwood
parameter was determined, the minimum reflux ratio was calculated from equation 7.
Subsequently, using the calculated minimum reflux ratio, an estimated actual reflux ratio could
be found by multiplying the minimum reflux ratio by 1.5. Then, using the determined reflux ratio,
minimum reflux ratio, and the calculated minimum number of plates the Gilliand correlation shown in
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fig. 1 were used to solve for the actual number of plates. Below is a table of the calculated Underwood
parameters, q values, minimum number of plates, minimum reflux ratio, actual reflux ratio and actual
number of plates of each column.
COLUMN 1 COLUMN 2 COLUMN 3
ΑLK 2.243111292 2.313600332 1.88709181
ΑHK 1 1 1
Q 1 1 1
Φ 2.218977338 1.060461704 1.21572126
RDMIN 6.77958894 0.712982545 1.71943031
RD,ESTIMATED 10.16938341 1.069473818 2.57914547
NMIN 2.099354635 1.236072764 3.1246751
N,ACTUAL 4 3 6 Table 2: Underwood parameters, q values, minimum number of plates, minimum reflux, estimated reflux, and actual number of plates for each column in the system.
Finally, the Kirkbride equation (equation 9) was used to calculate the optimum feed trap. The
two unknowns 𝑁𝑟𝑒𝑐𝑡𝑖𝑓𝑦𝑖𝑛𝑔 and 𝑁𝑠𝑡𝑟𝑖𝑝𝑝𝑖𝑛𝑔 are both determined since 𝑁𝑡𝑜𝑡𝑎𝑙 has already been defined in
the previous step. With all the values known, it is then possible to estimate where the feed location
should be.
COLUMN 1 COLUMN 2 COLUMN 3
OPTIMUM FEED PLATE
1 2 3
Table 3: Tray number where the feed enters the column.
Feeding a column to a plate lower than the optimum feed plate could lead to some plates
operating with a reduced driving force, and increase the number of plates necessary to reach
conversion. Similar consequences are seen if the feed plate is placed too high in the column. The
optimum feed plates minimize the amount of plates needed to reach the required separation, and
maintain a large enough driving force throughout each plate.
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VI) Pro/ll Analysis:
l) Choosing A Schematic:
Our feed system is composed of an equimolar mixture of acetone, butanol, ethanol, and water. A
basis of 100 kg-mol/hr was chosen for simplicity. The inlet temperature was set to 25 degrees Celsius,
this is below the bubble point of the system at a total pressure of one atmosphere. What this did was
make matching hand calculations much simpler since when the feed is set below the bubble point, the
feed is all liquid so we can treat it as a cold feed. The first distillation column is specified such that the
reflux ratio is set to two which helps increase the separation of acetone and ethanol going to the
distillate from butanol and water going to the bottoms. The second specification was that the distillate
flow rate is 64 kg/hr, this would be correct if 100 percent of the acetone and ethanol separated
completely from the bottoms products. Ten trays needed in the first column in order to achieve a better
separation, this is including the re-boiler and condenser as trays.
The distillate stream comes off of the condenser on the bottom so that everything in the top stream
comes out as a liquid. The distillate product was then put through a second distillation column to
separate the acetone from the ethanol. For this column, a reflux ratio of six was chosen to help aid in
getting a good separation by allowing a large amount of the distillate stream to go back into the top of
the column to re- boil. A new specification was made in this column to specify the top tray temperature
to be around the boiling point of acetone. This resulted in only acetone having enough energy to be in
the gas phase by the time it reaches the top tray. This ensured all of the ethanol to be condensed by the
top tray and make its way back down the column. This makes the composition of the distillate stream
out of the second column have a high purity of acetone. We also chose to make this column have eight
trays since the separation of ethanol and acetone is not that difficult than the separation we did from
14
the first stream. In order to get the composition of ethanol in the bottoms to still be high, we set a third
specification so that acetone should be 97 mole percent in the top stream.
The bottoms product from the first distillation tower is handled in a similar way. It is fed into a third
distillation column, which is set at eight trays since these two components are a slightly easier to get a
fair separation for since their individual boiling points are far from each other. A reflux ratio of six is still
used since it helps in purifying both product streams allowing components to re-boil and separate more.
The third column had a set specification similar to that of column two. We specified that water must be
98 mole % in the distillate; this maximized the water composition into the top as much as it could.
Butanol was then sent into the bottoms of column three. In our Pro/II system we were able to choose
any thermodynamic properties to be solved for by the UNIFO1 package. The reason for choosing this
package is because of the Liquid-Liquid-Vapor equations used since we have two liquid components
running through all the columns.
According to the Pro/ll Student Manual,
“Liquid Activity (LACT) Methods in Pro/ll calculate K-values by starting with an ideal solution and
correcting the result with activity coefficients. The activity coefficients are calculated from a
model for the excess Gibbs energy of the liquid mixture. The most commonly used methods are
NRTL and UNIQUAC. Binary interaction parameters are usually necessary. They may be:
• Obtained from PRO/II’s databanks
• Estimated using the UNIFAC method
• Supplied by the user
• Fit to experimental data
15
Dissolved gases may be modeled with Henry’s Law, and a heat of mixing option may be used to
correct for non-ideality in the liquid enthalpy. If the necessary parameters are available, LACT
methods can successfully describe a wide variety of non-ideal mixtures (particularly mixtures of
components having similar volatility) including mixtures exhibiting two liquid phases.”3
This was very helpful information because we were able to wisely choose the thermodynamic
package for our system.
Unfortunately, we still cannot get the best separation in our third column because of an azeotrope
that forms with water and butanol. The top stream of a column will always display this azeotrope. As
stated by literature,
“Liquid mixtures having an extremum (maximum or minimum) vapor pressure at constant
temperature, as a function of composition, are called azeotropic mixtures, or simply azeotropes.
Mixtures that do not show a maximum or minimum are called zeotropic. Azeotropes in which the
pressure is a maximum are often called positive azeotropes, while pressure-minimum azeotropes
are called negative azeotropes. The coordinates of an azeotropic point are the azeotropic
temperature taz, pressure Paz , and liquid-phase composition, usually expressed as mole
fractions. At the azeotropic point, the vapor-phase composition is the same as the liquid-phase
composition.”(Azentropic Data For…)
2 Pro/ll, see reference 10
16
Below is a table that shows the azeotrope that forms between water and butanol at the following
parameters:
http://chemistry.mdma.ch/hiveboard/picproxie_docs/000506293-azeotropic.pdf
17
Comparison between Methods:
I) Hand Calculations:
Data
Using the procedure outlined above the following tables were calculated for each column.
Table 4: Mass balances for each Column in the system.
Mass Balances
Column 1 Balance Mols Fed Distillate Mol Fraction Distillate Bottoms Mol Fraction Bottoms Fraction recovery of light key/heavy key
Acetone 5 5 0.687757909 0 0 0.97
Ethanol (LK) 0.5 0.485 0.066712517 0.015 0.00016176
Water (HK) 59.5 1.785 0.245529574 57.715 0.622398361
Butanol 35 0 0 35 0.377439879
Sum 100 7.27 1 92.73 1
Column 2 Balance Mols fed Distillate Mol Fraction Distillate Bottoms Mol Fraction Bottoms
Acetone (LK) 5 4.65 0.992751844 0.35 0.135341544 0.93
Ethanol (HK) 0.485 0.03395 0.007248156 0.45105 0.174416581
Water 1.785 0 0 1.785 0.690241875
Sum 7.27 4.68395 1 2.58605 1
Column 3 Balance mols fed Distillate Mol F Distillate Bottoms Mol F Bottoms
Ethanol 0.015 0.015 0.000261891 0 0 0.98
Water (LK) 57.715 56.5607 0.987516521 1.1543 0.032557405
Butanol (HK) 35 0.7 0.012221588 34.3 0.967442595
Sum 92.73 57.2757 1 35.4543 1
Column 1 Temp C 100.9245 Pressure (Kpa) 101.325
Component Melting Point C Boiling Point C MW (g/mol) Vapor Pressure (atm) alpa respect to HK
Water (HK) 0 100 18.015 1.033491103 1
Acetone -95 56 58.07 3.736703225 3.615612377
Ethanol (LK) -114.14 78.29 46.06884 2.318235564 2.243111292
Butanol -88.6 117.6 74.1216 0.533271451 0.515990365
Column 2 Temp 65
Acetone (LK) 1.338030239 2.313600332
Ethanol (HK) 0.578332489 1
Water 0.247731103 0.428354117
Column 3 Temp 107.1550656
Ethanol 2.862169553 4.20765656
Water (LK) 1.283654368 1.88709181
Butanol (HK) 0.68022889 1
18
Table 5: Raw data used for Bubble Point, Dew Point, and Flash Point Calculations
Table 6: Underwood parameter calculation, Rdmin, Rd actual, minimum and actual number of plates for column 1
Feed
K(Psat/Ptotal) X(mol fractions) Fraction vaporized Bubble T Dew Point Flash Point
1.033491103 0.595 0.0727 100.9245 106.9122 101.789
3.736703225 0.05
2.318235564 0.005
0.533271451 0.35
Bubble T Dew Point Flash Point
1.338030239 0.687757909 0.644284732 64.41 77.47 77.47
0.578332489 0.066712517
0.247731103 0.245529574
Bubble T Dew Point Flash Point
4.20765656 0.00016176 0.617660951 105.6 108.237 107.15
1.283654368 0.622398361
0.68022889 0.377439879
Distillate
comp a fi phi 1 Rdmin +1
1 Acetone 3.615612 0.12944 2.218977 1.780469
2 Ethanol LK 2.243111 0.464721 6.200542
3 Water HK 1 -0.48811 q=1 Saturated feed -0.20142
4 Butanol 0.51599 -0.10605 0
sum 1.1E-07
phi 2.218977 sum 7.779589 Estimated actual reflux ratio
Rdmin 6.779589 Rd 10.16938
Component xF Moles D xD MolesB xB Actual Number of plates
1 0.05 5 0.687758 0 0 x axis 0.30349
2 0.005 0.485 0.066713 0.015 0.000162 yaxis 0.39
3 0.595 1.785 0.24553 57.715 0.622398 Number of plates 4.08 4
4 0.35 0 0 35 0.37744 Optimum feed plate 1
sum 1 7.27 1 92.73 1
Min number of plates
Column 1 Nmin 2.099355
Column 1
19
Table 7: Underwood parameter calculation, Rdmin, Rd actual, minimum and actual number of plates for column 2
Table 8: Underwood parameter calculation, Rdmin, Rd actual, minimum and actual number of plates for column 3
phi Rdmin+1
comp a fi 1.060462 2.087756
1 Acetone (LK) 2.021897 1.446354 -0.11988
2 Ethanol (HK) 1 -1.10338 q=1 saturated feed 0
3 Water 0.434834 -0.17065 sum 1.967876
sum 0.172317 Rdmin 0.967876 Estimated actual reflux ratio
phi 1.060462 Rd 1.451814
Actual number of plates Figure
Component xF Moles D xD Moles B xB x axis 0.19738
1 0.687758 4.65 0.992752 0.35 0.135342 y axis 0.48
2 0.066713 0.03395 0.007248 0.45105 0.174417 Number of plates 3.3 3
3 0.24553 0 0 1.785 0.690242 Optimum feed plate 2
Sum 1 4.68395 1 2.58605 1
Min number of plates
Column 2 Nmin 1.558676
Column 2
phi Rdmin+1
Comp a fi 1.215721 0.000368
2 Ethanol 4.207657 0.000227 2.775717
3 Water (LK) 1.887092 1.749441 q=1 Saturated feed -0.05665
4 Butanol (HK) 1 -1.74966 sum 2.71943
sum 3.3E-06 Rdmin 1.71943 Estimated actual reflux ratio
phi 1.215721 Rd 2.579145
Actual number of plates
Component xF Moles D xD Moles B xB x-axis 0.2513
2 0.000162 0.015 0.000262 0 0 y-axis 0.4
3 0.622398 56.5607 0.987517 1.1543 0.544034 number of plates 5.874 6
4 0.37744 0.7 0.012222 0.967443 0.455966 optimum feed plate 3
Sum 1 57.2757 1 2.121743 1
Min number of plates
Column 3 Nmin 3.124675
Column 3
20
VI) Pro II Calculations
Our system contains three distillation columns, each with a reboiler and condenser to achieve our
desired separation of Acetone, Ethanol, Water, and Butanol. The distillate from column one is fed to
column two, and the bottoms from column one is fed to column three. Below is the exact calculated
data from Pro II for each of the corresponding streams shown in the system diagram above.
System Diagram
Feed Stream
(S1) Column 1
Column 2
Column 3
Acetone (S7)
Ethanol (S6)
Water (S4)
Butanol (S5)
Reboiler
Condenser
(S2)
(S3)
21
Pro II results
22
23
24
25
Comparison of Methods:
Comparing our results between the hand calculations and our Pro/ll results, we came fairly close to
having the same answers. For our hand calculations we determined the exact number of trays and reflux
ratios of each column. We have less than 10 trays for each column and reflux ratios of two or below. For
the Pro/ll specifications, we needed 10 trays in the first column, and eight trays for the two other
columns. The actual reflux ratios used were two in the first and six for the other two columns. The
reason for the higher reflux ratios is because our desired separation required more rigorous parameters
to separate our species. Pro/ll takes into consideration actual real system parameters which we
assumed to be negligible in our hand calculations. Because of this assumption, our numbers differed in
Pro/ll slightly accounting for such realistic systems. Overall, we achieved 98 percent separation of
butanol which was our original goal. We couldn’t separate water completely from butanol because of
the azeotrope that forms between water and butanol. According to literature, water is about 70 percent
composition and butanol is 30 percent composition when forming the azeotrope. We can see that it is
very similar in column three that was separating the two. Acetone and ethanol originally had no
specifically preferred separation percentages. However, we were able to assume that they would
separate well from each other. As for our second column, we had 97 percent of acetone in the distillate,
which was a very good product yield; ethanol was not in the distillate but was 15 percent removed in
the bottoms stream.
26
VII) Manual use of Pro/ll:
Step 1:
When opening pro/ll, one must first select some of the basic information before setting up their reactors
or columns. We first want to choose our components for our system by selecting the chemistry button
displayed below:
27
Step 2:
We need to choose our unit of operations for our system and the thermodynamic package for which we
want to run our system. Please refer to the following image:
28
Step 3:
Now a system type can be chosen along with the entire set up. After selecting, say a distillation column,
you can add streams connecting them from the beginning of the column and then again coming out of
each column. The instructions are shown:
29
Step 4:
Now we must choose our molar feed rate and molar composition of our inlet stream into our first
column. After we choose that , then we must specifiy each column as follows:
30
The specifications are picked by double clicking on the column which will bring up the following window,
Select the boxes that are red and set the parameters that are desired for the column to operate at.
Below is the pressure profile that was chosen to be at atmospheric conditions:
31
Next, we chose the flow rates for which our bottoms and distillate streams ran at.
Finally, we set our specifications on our column:
Repeating the process for all other columns is necessary for them to converge and run correctly.
32
Once all parameters are set, click the run button and watch your columns turn blue which means
everything ran correctly and the results are shown in the “results window”. After being run, our system
is provided with observations below:
33
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34
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