Hello guyzzz..........!!!
Back after many months and sorry for not being regular here, i've received a query from one of the visitor, and i think many of you too have the same question i.e., How to calculate the rate of distillation in a batch reactor....??
And for this query today i gonna put a end mark, i'll explain you with an example here,
but, before that you need to know some basics like, when are we going to do distillation in a batch reactor during a product manufacturing......!!
Most commonly there are 2 cases,
1) after completion of reaction, for impurity removals we will do some workups with solvents like water, which is followed by product layer concentration, simply called as product concentration,
2) The 2nd one will be removal of Moisture from the raw materials, for this the raw materials should be made soluble in a suitable solvent and then the solvent medium is distilled off under vacuum, which will remove the water molecules from the raw materials and make them suitable for carrying out reaction, this is usually done for moisture sensitive products.
So, here now i'll demonstrate an example case study,
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Our case is, we need to calculate the distillation rate in a reactor having a product layer of Ethyl Acetate, and the distillation should be carried out with vacuum NLT 650 mmHg, and temperature NMT 40 deg C,
Let suppose our reactor capacity is 10 KL with MOC SS316, and the product layer volume is around 5 KL say,
Now we need to collect some raw data like HT area of SSR, Specific heat & Density of Solvent, etc.
10 KL SSR will have an HT area of 19.82 Sq.m, but the effective HT area for this operation will be equals to Total HT area x Occupancy of reactor,
Occupancy of reactor = Reaction mass volume / Reactor volume = 5 KL / 10 KL = 0.5,
Effective HT Area = 19.82 x 0.5 = 9.91 Sq.m,
For More info on calculating HT area of reactors, Read this:
[How To] Calculate Reactor HT Area
Density of Ethyl Acetate is 897 Kg/cu.m, Specific heat : 0.454 KCal/Kg. K , Latent Heat of vaporisation is 87.6 KCal/Kg,
As the MOC of the reactor is SS316, the Overall Heat Transfer Coefficient can be considered as 250 KCal/Sq.m. Hr. K.
If you want to calculate the Overall Heat Transfer of a reactor with more accuracy, then read this post,
[How To] Calculate Overall Heat Transfer Coefficient
So now, getting into our calculation we need to calculate the amount of energy that our HT area is going to transfer per hour, and that we can calculate as follows,
Q = U x A x LMTD,
Sorry guys, i forgot to calculate the LMTD previously, anyway now i'll do it for you,
for calculating the LMTD we need two streams, one is utility stream and the other one is batch volume,
So , coming to Hot water utility, now you may have one doubt that why i've used Hot water as utility, the reason is we have a Specification that reaction mass temperature shouldn't exceed 40 deg C, thats why i've considered Hot water instead of Steam, and now another question may arise in your mind, what can be the hot water set point, usually we will maintain a Delta T of 10 deg C, so the Hot Water Set point will 40 deg C + 10 = 50 deg C.
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so now Th1 = 50 deg C, Th2 = 45 deg C (say), Trxn = 25 deg C [ i've considered the reaction mass temperature as 25 deg C because at 650 mmHg of vacuum, the boiling point of ethyl acetate will be hardly 25deg C, this can be calculated from antonie equation],
LMTD = ( ( Th1 - Trxn ) - ( Th2 - Trxn ) ) / Ln [ ( Th1 - Trxn ) / ( Th2 - Trxn ) ]
= ( ( 50 - 25 ) - ( 45 - 25 ) ) / Ln [ ( 50 -25 ) / ( 45 - 25 ) ]
= 5 / Ln [ 1.25 ] = 22.727 Deg C,
Now, lets resume our calculation,
Q = U x A x LMTD
= 250 x 9.91 x 22.727 = 56306.143 KCal.
Now we need to know what is the Heat load of the Reaction mass i.e., summation of Sensible heat & Latent heat,
Qhl = Sensible heat + Latent heat
= M x Cp x dT + M1 x Lambda
= ( V x Rho ) x Cp x dT + M1 x Lambda
= 5 x 897 x 0.454 x ( 30-25) + M1 x 87.6
= 10180.95 + M1 x 87.6
Now, we need to equate the overall heat load to the reactor supply load i.e., 56306.143 Kcal,
10180.95 + M1 x 87.6 = 56306.143
M1 x 87.6 = 46125.192
M1 = 526.54 Kgs of Ethyl Acetate = ( 526.54 / 0.897 ) Lts of ethyl acetate
M1 = 587 Lts of Ethyl Acetate.
If you guys understood the above done calculation clearly, Then say Cheers :)
And if any doubts were there, please ask us, we are happy to help you,
Comments are most appreciated :)
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About The Author
Hi! I am Ajay Kumar Kalva, Currently serving as the CEO of this site, a tech geek by passion, and a chemical process engineer by profession, i'm interested in writing articles regarding technology, hacking and pharma technology.
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