Have received some comments asking me to calculate the vapor line height of a batch reactor. Usually everybody will ask about the dia calculation, but this is something that caught my focus, because being frank i too donno the exact way to calculate the height of vapor line.

So here today, i'll demonstrate my idea to calculate the height. If you are a new reader and searching for Dia calculation of vapour line, then follow this,

This post is requested by Mr. Ram prasad.

**How to calculate the column dia required for a reactor ?**How to calculate the dia of vapour column

But before going in depth calculation, i want you to know that this is just my way of calculation, there may be a direct calculation or something, but i donno those all, and openly speaking i don't like remembering all the equations, if required i'll try to derive those equations.

*Is there any relation between the height and dia of vapour column ?*There is nothing like that, if there is something like that earlier i should have demonstrated you, As vapour column is meant for vapour / gas transferring from reactor to condenser, and the dia depends on the boil-up that is generated in the reactor, height should be designed based on the vapour density, if the vapour density of a solvent that i need to distill out is high then automatically the vapour won't reach much height and in between it will get condensed.

Anyhow, i think this knowledge is enough for getting started, if anything you need to grab just comment in the below section.

The relation between pressure, density, height / head is given by

P ressure = D ensity x G ravitional constant x H eight

simply, P = ꝭ x g x h.

Here today i'll calculate the vapour column height required for distilling methanol in a batch reactor.

Now lets calculate the vapour density

Lets make use of ideal gas law,

P x V = n x R x T.

P x V = ( w / W ) x R x T.

( P x W ) / ( R x T ) = w / V

ꝭ = ( P x W ) / ( R x T ).

W - boilup, R - universal gas constant, T - Boiling point or any other temp.

P - Vapour pressure.

Lets need to calculate the vapour pressure ( P ) and boil up ( W ),

Vapour pressure from Antonie equation,

Antonie equation: Log P = A - B / ( T + C ).

A, B, C are antonie constants.

These constants can be retrieved from google, anyway i'll provide those here,

Open this in new tab for antonie constants.

As the old calculation is creating some controversies, i've decided to add a new way to calculate the height of vapour line required.

Lets the case be, a 5 KL SSR with 60% methanol inside and we need to calculate the vapour line size.

The heat transfer area of 5 KL SSR is ~ 12.5 Sq.m,

The effective heat transfer area will be 12.5 x 0.6 = 7.5 Sq.m [with 60% occupancy],

Lets say the utility temp will be 80 C, and

Initial reaction mass temperature will be 30 C,

Final reaction mass temperature will be 64 C,

Lets consider 3 C of temperature difference between jacket utility in and out,

So out let temperature will be 77 C.

LMTD = ((80 - 30)-(77-64)) / Ln((80-30)/(77-64)) = 27.46 C.

Overall Heat transfer coefficient will be ~200 KCal/Hr.Sq.m.C,

Learn how to calculate overall Heat transfer coefficient

Latent heat of Methanol is 264 KCal/Kg,

Density of Methanol is 0.79 Kg/L, Mol wt. of methanol is 32.05 g/mol.

Boil up rate based on effective heat transfer area is 155.97 Kg/hr,

Learn how to calculate the boil-up rate of solvent in reactor

Volumetric boilup is Mass boilup / Density = 197.43 L/hr,

Lets calculate the relevant vapour pressure using volumetric flow rate from the ideal gas law,

P x V = n x R x T,

P = n x R x T / V,

P = ( 155.97 / 32.05 ) x 8.314 x ( 64 + 273.15 ) / 197.43

P = 69.09 KPas = 69092.71 Pas.

**You may like this:**

How to calculate Vent size for vessels ?

What is vacuum steam technology ?

Lets calculate height based on the above mentioned relation, P = ꝭ x g x h.

h = P / ( ꝭ x g ),

h = 69092.71 / ( 1.1 x 1000 x 9.81 ) = 6.40 m.

1.1 is the vapour density of methanol

Above mentioned 1000 is to convert density from Kg/L to Kg/cu.m.

That's it......!!!

Now you got the height of vapour column that need to be arranged for a 5KL SS reactor for getting a boil up of 197 L methanol with 60% occupancy,

Hope you enjoyed the calculation here....!!!

Any queries most welcome, reach me through message / comments,

Comments are most appreciated.....!!!!

*[**Calculation is slightly modified, thanks to Bhaskar for pointing out the error in unit conversion]*

*** The case study is changed a the previous is based on antonie equation and it'll slightly cause controversies, thats why i've modified with a fresh calculation.*

**Related Articles:**

How to calculate Heat transfer area theoretically ?

How to produce steam at 60 C ?

How to Design a chiller plant ?

*How to calculate U (Overall Heat Transfer Co-efficient) value ?***A**bout The Author

What is lowest and highest withstand temperature for GLR....

ReplyDeleteDear Anand,

Deleteas per my experience, its -50 to 250 degC

Regards,

AJAY K

please how u got lambda value

ReplyDeletemethanol latent heat is 264 KCal / Kg

DeleteRegards,

AJAY K

how got P,Lamda and Lmtd values please provide clear calculations for better understanding

ReplyDeleteThank you

Latent heat (lamda) you can google it, LMTD value i've considered averagely instead of calculating

DeleteDear Anonymous,

pl comment next time with identity as your comments were getting detected as spam.

Regards,

AJAY K

How we got p value 84119 ?

ReplyDeleteconvert 630.95 mmHg to Pascals, it shall be 84119pas

DeleteRegards,

AJAY K

Good work...

ReplyDeleteThank you

Thanks Dheeraj

DeleteAJ.. Im having one doubt reg no of moles = w/W i.e weight / molecular weight. How u considered Molecular weight W as Boilup parameter ? U done boilup calc r8, bt how molecular weight will b related to boilup.. Pl gve me proper justification.. Thank you

ReplyDeleteDear Jai,

DeleteFor a gas or a liquid the molecular weight will remain same and the chemical formula will also remain the same, but density varies, that's how i've taken the the molecular weight for boilup.

Any queries feel free to comment.

Regards,

AJAY K

Mathematical justification please

DeleteBoil up ( W ) = U x A x LMTD / ƛ,

ReplyDeleteAjay please simplify this formula ,if this is M*lemda=U*A*Lmtd then

how Mass (M) Consider as a boil up

regards

raj

Dear Raj,

DeleteM is nothing but the amount of mass that is distilled out, that's how i meant it as boil up, and what you have mentioned is correct, i've just changed the terminology, don't mind it.

Regards,

AJAY K

Hello ajay,

ReplyDeleteI don"t know the process, but i can say clearly that the entire calculation is wrong. Once check the unit consisttancy and also try to find the mistake by calculating it with using units for each and every value you have taken.

Dear Sai,

DeleteGlad to receive a comment like this, pl spot out the section where i went wrong, so that i will change it, and as these post's were of my own knowledge there may be chance for mistakes, so pl don't mind.

Regards,

AJAY K.

1. while you are calculating boilup value "U" value you have taken as 200 w/m.k and at the same time latent heat as 264 kcal/kg. Here you have to convert watts to KCal.

Delete2. And once check unit consistancy for density caluculation.

3. And finally for height calculation something went wrong.

Dear Sai,

DeleteAnswering to your queries,

1. in this whole blog, when ever i consider something as U value, the units that i consider shall be KCal/hr.Sq.m.K, and the units(w/m.K) you have mentioned belongs to thermal conductivity not overall heat transfer coefficient.

2. coming to density calculations, i'm pretty sure, the units were just perfect, once follow this link for reference, http://www.science.uwaterloo.ca/~cchieh/cact/c120/idealgas.html

3. In the height calculation, i've extended calculating the height in m, may be i should have ended it in the main formula itself, now i've edited, just check it now.

Regards,

AJAY K

Ohh sorry, Thank you for clarrifying me.

DeleteNo issue Sai, no need of sorry, keep on visiting

DeleteRegards,

AJAY K

Great article.

ReplyDeleteThanks for landing on this page and reading this post.

DeleteHello there! Do you know if they make any plugins to

ReplyDeleteprotect against hackers? I'm kinda paranoid about

losing everything I've worked hard on. Any tips?

Thanks for reaching me, but this is not the perfect page for your query, reach me at

Deletewww.computerinnovations.info

Regards,

AJAY K

Spot on with this write-up, I honestly believe this

ReplyDeleteweb site needs much more attention. I'll probably be returning to see

more, thanks for the info!

Dear,

DeleteBy the next time you visit, kindly add comments with your name, if any hurdles were there while commenting with you real name, lemme know those.

Regards,

AJAY K

Are you saying that if the boil up is increased then height of vapor column will come down ? At least the formula says so. Do the calcs by considering 75% reactor filling and boil up there of.

ReplyDeleteDear Joshi,

DeleteAs the boil-up decreased then the line size should be reduced in order to enhance the pressure inside the line and for effective transfer of the boil up towards the condenser.

And what are you have mentioned is a inverse relation and that cant be done practically.

Regards,

AJAY K

I’m not that much of a internet reader to be honest but your sites really nice, keep it up!

ReplyDeleteI'll go ahead and bookmark your website to come back

in the future. Many thanks

Good, land again with pleasure.

DeleteDear Ajay Kumar , u have written that PV= nRT

ReplyDeleteP*V= (Weight/molecular weight)*R*T

(Weight/volume) = (pressure* molecular weight)/(R*T)

BUT ( Weight/volume)=density

i dont understand this

plz let me know what temp u have taken in while calculating LMTD for methanol?

u have taken value is 28

Very good but can you find vacuum pump requirement for 3kl SSR using methanol as solvent.

ReplyDeleteDear ,

DeleteUsually vacuum pump shall be selected based on the system capacity and leakage rate irrespective of solvent.

follow the link : http://pharmacalc.blogspot.com/2016/03/how-to-select-required-pump-capacity.html

Regards,

AJAY K

Thanks

ReplyDeleteBut I need brief calculation of heat load calculation Q=mcpdt+m*lamda

Here can we take m constant

Dear,

DeletePl read this full post,

http://pharmacalc.blogspot.com/2016/03/theoretical-way-to-determine-time.html

M you cannot take constant everytime, because hour to hour during distillation it will vary.

Next time, kindly comment with your good name plz.

Regards,

AJAY K

What about the R value? u have taken it as 62

ReplyDeleteR value.. Can you tell me how you got the Universal gas constant value?

ReplyDeleteDear Abdul Haleem,

DeletePl refer the below link,

http://www.cpp.edu/~lllee/gasconstant.pdf

Regards,

AJAY K

helloo ajay

ReplyDeletei am installing 5 kl reactor & 20m2 condesor (temp of cooling water is 25 25 deg avg. )to cool down vapor of VAM at time of vam & catalyst reaction.

is this installation ok to cool down VAM vapor ?

Dear ,

DeleteWhat does this VAM means exactly ?

Next time kindly comment with your name,

Thanks,

AJAY K

Dear sir,

ReplyDeleteDoesn't the height of vapor column change with size of vapor column? Please explain me.

Dear ,

DeleteYeah, it may change inversely, because as the dia increases the built in pressure will decrease.

Next time kindly comment with your name,

Regards,

AJAY K

Dear sir,

ReplyDeleteHow to calculate the size of vapor column for a batch reactor?

Dear ,

DeleteThere is no mystery behind the size calculation, its so simple,

What ever the boilup that is generated during distillation should pass through the column, that's it,

Boilup rate ( V ) = A x v,

where, A is cross sectional area, v is velocity of vapour,

usually the velocity during,

Normal distillation shall be considered as 1 to 3 m/sec, if its a

Vacuum distillation, the velocity should be considered as 65 to 70 m/sec.

if the boil up rate is known, you can calculate the dia from the above mentioned equation, still any queries pl feel free to contact / comment,

Regards,

AJAY K

Sir,By taking velocity of vapor 2m/s ,vapor line size is 0.0059m(just 5.9mm) very low...? Check it once please...

DeleteHello Sravani,

DeleteWhat the required boilup rate that you have considered & whats the solvent ?

Best Regards,

AJAY K

Dear sir,

ReplyDeleteWhy steam is given from top of the reactor jacket and others from bottom?

Dear Venkat,

DeleteUsually the steam condensate will have more density than the steam, so if steam is given from bottom the condensate will create some pressure on the incoming steam, so the steam will loose its efficiency,

If liquid utilities were given from top then there wont be any pressure buildup in the jacket as the incoming utility will get discharged from the jacket through gravity and also will result in air locks generation, hence liquid utility shall be given from bottom and the steam shall be given from top.

Regards,

AJAY K

Dear sir,

ReplyDeleteDoes boil up change for vacuum distillation and normal distillation? If yes, how? Please explain me.

Dear Venkat,

DeleteUse the formula P x V = n x R x T,

In case of normal distillation, P = 760 mmHg, T = boiling point of respective solvent,

if its vcuum distillation, P = desired / maintained pressure, T = maintained temperature,

V = volumetric boil-up.

Regards,

AJAY K

Ajay why used 1000 in density calculation

ReplyDeleteDear sir,

ReplyDeleteNice information provide you to all.

My self Dheeraj, in this case at the time of density calc.

=(630.95 mmHg*132.15 Kg)/[62.363(L mmHg/mol K)*(333.15 K]

= 4.013 Kg mol/L

= 4013 Kg mol/ cub. m

in that you say unit is Kg/ cub m

please explain.

am prakash.

ReplyDeleteHow to calculate the vapor pressure? please provide clear calculations for better understanding.

log P = 8.08 - 1582.27 / ( 60 + 239.73 ),

P = 630.95 mmHg.

Dear Prakash,

DeleteFollow the below link, http://pharmacalc.blogspot.com/2016/12/how-boiling-point-varies-with-vapor.html

Regards,

AJAY K

Dear sir,

ReplyDeletethrough your calculation MeOH vapor density was 4010Kg/m3, is it practically true? please justify for me.

Thanks and Regards,

P.B.Pradeep

Dear Pradeep,

DeleteModified the calculation slightly, as the existing calculation which uses antonie equation is creating some sort of controversies.

Best regards,

AJAY K

Dear sir,

ReplyDeleteAm ok with the calculation part. i tried it by my own applying it to our reactors also. My doubt is can we have the height less than we calculated also. Because above the calculated height we may experience self condensation. But i think height lesser may also be used. Its right or wrong? please clarify.

Thanks and Regrds,

Rakeshkumar

Exactly, you got it,

DeleteThis post will be modified slightly to make it clear, as currently it is creating some controversies.

Best Regards,

AJAY K

Dear Sir

ReplyDeleteI am Bala Raju Kinjangi

i have doubt in Antonic eqn calculation ,how the P value is coming 630.95 mm hg,please reply sir. any conversion is there.

Dear Bala,

DeletePl refer this post, http://pharmacalc.blogspot.com/2016/12/how-boiling-point-varies-with-vapor.html

Regards,

AJAY K

Dear Sir,

ReplyDeleteI am BalaRaju Kinjangi,

in Boil up Calculation why r u not taken Q=SENSIBLE HEAT+LATENT HEAT. PLEASE REPLY SIR.

Regards,

K.BalaRaju

Dear Bala,

DeleteIn the boil up calculation, we need to determine the amount of vaporization, so i've considered only latent heat.

Regards,

AJAY K

Thank you very much sir,Ajay Garu

ReplyDeleteRegards,

K.BalaRaju

Dear Sir,

ReplyDeleteI want P & ID software for Pharma industry.atleast Names sir.

Regards,

K.BalaRaju

Dear Bala,

Deleteshare me your mail id, through contact me page, i'll share you the equipment symbols.

Best Regards,

AJAY K

Dear sir

ReplyDeleteThank you sir for your information. my Mail id is : kinjangi.balaraju@gmail.com

Regards,

K.BalaRaju

why you have used liquid methanol density in height calculation. i think it should be vapor density

ReplyDeleteDear ,

DeleteGreat point you made here, thanks, actually it need to be considered, correcting the post now.

Keep on visiting, next time kindly comment with your good name.

Best Regards,

AJAY K

Please post the operating procedure for vacuum tray drier

ReplyDeleteHi I am Prabhakar

ReplyDeleteHow did you get boil up rate as 159.7 kg/hr?

Kindly let me know

Dear Prabhakar,

DeleteIt's 155.97 Kgs/hr, not 159.7 Kg/hr, kindly check the above calculation.

Boil-up = U x A x LMTD / Latent heat = 200 x 7.5 x 27.46 / 264 = 155.97 Kgs/hr.

Regards,

AJAY K

the units are wrong for the pressure calculation

ReplyDeleteP=nRT/V

Unit is coming as J/Lts but how it went as Kpas

Give us a proper Justification

Dear ,

DeletePl go through the values of gas constant,

https://www.cpp.edu/~lllee/gasconstant.pdf

Next time kindly comment with your good name please

Best Regards,

AJAY K