8 replies to this topic

[ahmadqq]

Hi 

 

i am chemical engineering student, i have done a complete material balance and energy balance for a re boiler my project is CO2 removal by using a-MDEA 

 

after do balance required i have to do a design for it 

 

 

 

i have to do the following

 

[img http://im85.gulfup.com/Wf7swV.jpg]

 

 

so how to define the duty of a reboiler ? 

 

thanks in advanced  

 

[AlertO]

hi ahmadqq

 

you said you have done the m&e balance for all streams. So, the reboiler duty can be detemined by doing the energy balance for stream no. 9,10 and 11.

[Art Montemayor]

If you have done "a complete heat and material balance" (which is the basic, first step in a process design), then you have the answer to your question (how to define the duty of the reboiler).

 

What is the problem?

[ahmadqq]

AlertO & Art Montemayor 

 

thanks to you both for the help , 

 

yes i did the complete material and energy balance ,, so do you mean by doing these work i already answer it the question ? 

 

if that so i will go for the second part which is 

 

2- physical properties and chose the best type and estimate the heat transfer area ?

 

i need your help or hints from where to start

 

thanks dears  

[Art Montemayor]

_Ahmad:

 

_{Are you aware that the duty for the aMDEA reboiler in your flow diagram is equal to the enthalpy difference between streams 10 and 9?  Since you have done a complete heat and material balance, then you have the answer.}

 

_{I am concerned that you are able to do a complete heat and material balance and yet don't know where the reboiler duty contributes to the balance.  I am also concerned that even given the duty, you don't know where to start in designing the proper size of the required reboiler tube bundle.}

 

_{Have you decided what type of reboiler to use?}

_{Have you done the required process research and study by reading and studying such texts as Kohl & Neilsen's "Gas Purification", the GPSA Engineering Handbook, Campbell's "Gas Conditioning and Processing"?  The Internet also has much material on the matter and you can find it by using the Google search engine.}

[ahmadqq]

Thanks for you answer , 

 

i know its sounds weird but i really did all of that balances ,, actually i am excellent in math i just followed the examples in my handout without knowing the concepts, thats why iam in big trouble  

 

anyway 

 

yes i got the enthalpy of the 3 stream 9,10,11 ,, what i did now o took the different between stream 9 - (10+11) as the following

 

₍H _S-10 + H _{S-1) – (}H _{S-9) = Duty} 

 

 

about the type of the re boiler i believe they mentioned the type i have to take a look to the detail  then i will back to you , 

 

and i will download the books you advised , thank you  

  

[AlertO]

hi ahmadqq

 

as per you simplified diagram, it seems that you've already decided to use kettle type. what is your reference for this heating configuration?

[ahmadqq]

the instructor told me to choose any type i would like 

 

so whats the easiest rebolier type  to start design with ? 

[xavio]

Hi ahmadqq,

 

How did you perform the mass and energy balance of the column? By hand calculation or computer simulation?

 

At first glance I thought you used McCabe graphical method combined with Winn-Underwood-Gilliland shortcut method.

But, I feel weird that you were able to obtain some internal flows of the column, namely stream 9 and 10, by using above methods.

So, in that case, you must have performed rigorous calculation using some kind of simulator, am I right?

I am now wondering how the simulator doesn't report column heat duty to you.

 

Anyway, if you know how to get the mass flow and enthalpy of those streams around the reboiler, then you should be able to get the reboiler duty.

 

As to the reboiler, if your stream 10 is 100% vapor, then your calculation has assumed a kettle type from the beginning.

In fact, kettle reboilers are the easiest to design, they're well studied and don't required complex hydraulic balancing.

I assume that you only want to find the estimate of required heat transfer area, instead of issuing equipment datasheet.

First try to find a representative U value for your system under "pool boiling" mode, then area calculation is straightforward.

Q = U . A. LMTD

 

Good luck.

 

xavio