8 replies to this topic

[André Neves]

Hello! I'm a chemical engineering student and I'm doing a final project. In this project (production of sodium hypochlorite) I have to design among other things two absortion Columns (absortion of chlorine in caustic soda) and two heat exchanger plates.

Can someone help me in the strategy to design this two types of equipment? I have already made the mass and heat balances so I know the mass flow that go trough these equipments. But I don't know for example how to know the global coeficient of heat transfer (the U of the equation Q=U.A.DTln)..

Best Regars and thanks,

André

If you know something that might help me please say something for the e-mail: grupo2.projecto@gmail.com

[JEBradley]

Just a few questions

1.) Did you really mean you have to design two heat exchanger plates or was it meant to be two Plate Heat Exchangers?

2.) The overall heat transfer co-efficient depends on the type of exhanger (I know you said plate - but this could be plate and frame, shell and plate etc.), materials of construction, and the chemicals involved in the heat transfer, also is there a phase change involved.

NB - with a bit more information it should be relatively easy to get a value of U so dont worry.

3.) You said to e-mail you any information - so will you still be reading this? If not why am I still typing

4.) You said you have to design two absorption columns - are they two identical columns?

5.) Do you have access to process simulation software - Aspen, HYSYS, Pro II or whatever? Or do you have to design it the long way (id est pen and paper and a Sherwood plot).

[Padmakar Katre]

Dear,
I will reply your query partly i.e. regarding the process design of the absoption columns.As you prtend that you have already calculations for mass and heat balance then just to design the columns should not be a big deal.Just refer to any of the process design handbook you will get the clearcut idea for how to proceed with.Anyways all the best.

[André Neves]

Just a few questions

1.) Did you really mean you have to design two heat exchanger plates or was it meant to be two Plate Heat Exchangers?

They are two equipment peaces indeed..of course that if I know how to do one the other is the same thing

2.) The overall heat transfer co-efficient depends on the type of exhanger (I know you said plate - but this could be plate and frame, shell and plate etc.), materials of construction, and the chemicals involved in the heat transfer, also is there a phase change involved.

The type of exhanger it's me who choose..I only need to a mixture with NaOCl,NaCl,H2O and NaOH from 22ºC to 18,5ºC..I know the heat to take of in the exchanger,all the temperatures (cooler fluid is water at 5ºC that goes out from the exchanger at 15ºC)..but I don't know how to find the U to calculate the Area..

NB - with a bit more information it should be relatively easy to get a value of U so dont worry.

3.) You said to e-mail you any information - so will you still be reading this? If not why am I still typing

I read here too


4.) You said you have to design two absorption columns - are they two identical columns?

yes they are similar to each other..the only thing it's diferent is the flow of the row materials.

5.) Do you have access to process simulation software - Aspen, HYSYS, Pro II or whatever? Or do you have to design it the long way (id est pen and paper and a Sherwood plot).

yes I have access to Aspen but I get errors all the time..don't really know how to introduce the data to Aspen give me the right results..so I was thinking in design it with pen and paper..but still didn't find the best strategy to do it..once I found this forum I decided to ask the bests to learn it the good way..

Greetings,
André

[André Neves]

Dear,
I will reply your query partly i.e. regarding the process design of the absoption columns.As you prtend that you have already calculations for mass and heat balance then just to design the columns should not be a big deal.Just refer to any of the process design handbook you will get the clearcut idea for how to proceed with.Anyways all the best.

Sorry but I didn't understand which handbook you talk about..Yes the mass and heat balances are done but I don't know how to design the absorption columns..you said "should not be a big deal"..can you please tell me how I can do it?

Best Regards and thanks,
André

[JEBradley]

So does it have to be a plate heat exchanger or could you maybe use a shell & tube??

Of the top of my head I would put a U-value of 1500-2000 W/m²K for a plate heat exchanger. But I think when you hand this to your lecturer you will need something more substantial (and reliable) than my word. If you can get a copy of Chemical Engineering Volume 1 by Coulson & Richardson then table 9.19 on p428 gives some U values. Actually they talk of U values up to 6000 W/m²K but I find this hard to believe.

I recently ordered a Shell and Plate exchanger and the U value was 100 W/m²K so there's clearly a big difference here (this was liq-liq too).

Overall heat transfer co-efficients for shell and tube exchangers seems to be a subject that has received more coverage in literature. Coulson&Richardson, Perry, Kern, etc. all give lots of tables of U values plus the method for calculating it yourself.

[Padmakar Katre]

Dear,
Just get any of the following process design book where you will find the procedure to design absorption column,
1.Chemical Engineering Vol 2 by Richardson And Coulson
2.Applied Process Design For Chemical Plant and Petrochemical Plants Vol 2 By Ernest E Ludwig.
3.Chemical Process Equipment Selection and Design By Stanley M Walas (Both Absorption and Plate Heat Exchangers Desgin is covered.)
4.Hnadbook of Chemical Processing Equipments By Nicholas P.(Plate Heat Exchangers)
There are number of books availabe and I think it will be available in your institute's library.
I hope now you will not have any problem.

[André Neves]

So does it have to be a plate heat exchanger or could you maybe use a shell & tube??

It should be plates because I visit a plant here that produces it and it uses plates heat exchanger because with the same eficiency in heat transfer we can have a smaller equipment..so I thought it would be best a plate heat exchanger to reduce the layout of the plant, once I would need three heat exchanger at the all process.

Of the top of my head I would put a U-value of 1500-2000 W/m²K for a plate heat exchanger. But I think when you hand this to your lecturer you will need something more substantial (and reliable) than my word. If you can get a copy of Chemical Engineering Volume 1 by Coulson & Richardson then table 9.19 on p428 gives some U values. Actually they talk of U values up to 6000 W/m²K but I find this hard to believe.

I recently ordered a Shell and Plate exchanger and the U value was 100 W/m²K so there's clearly a big difference here (this was liq-liq too).

Overall heat transfer co-efficients for shell and tube exchangers seems to be a subject that has received more coverage in literature. Coulson&Richardson, Perry, Kern, etc. all give lots of tables of U values plus the method for calculating it yourself.

Humm I will certainly see this books to see if some of them talk about the design of plates heat exchangers. Lots of thanks=)

[André Neves]

Dear,
Just get any of the following process design book where you will find the procedure to design absorption column,
1.Chemical Engineering Vol 2 by Richardson And Coulson
2.Applied Process Design For Chemical Plant and Petrochemical Plants Vol 2 By Ernest E Ludwig.
3.Chemical Process Equipment Selection and Design By Stanley M Walas (Both Absorption and Plate Heat Exchangers Desgin is covered.)
4.Hnadbook of Chemical Processing Equipments By Nicholas P.(Plate Heat Exchangers)
There are number of books availabe and I think it will be available in your institute's library.
I hope now you will not have any problem.

I will certainly look for that books at my institute's library!
Thank you very much for your help!
Best Regards,
André Neves