10 replies to this topic

[BluesGirl]

Hi,

 

I'm designing an absorber with a neutralisation process but would like to know what approach I would use to find or design with an appropriate temperature and pressure of an absorber (packed column).

 

I know that the operating temperature of the absorber is 70C. NaOH entering is at ambient temperature and 0 kPag. Please tell me if there are any assumptions made.

 

Thank you.

[breizh]

Hi,

Consider this paper from Perry (7th edition) .

 

Hope this helps

 

Breizh

[BluesGirl]

Hi Breizh,

 

Thanks for your help and I appreciate it. I didn't seem to find much on what I was after. I will try using Aspen Plus for now.

[fallah]

BluesGirl,

 

To specify the DT and DP of the equipment, refer to the relevant process design criteria. In general they are maximum operating values plus a reasonable margins...

Edited by fallah, 28 August 2014 - 12:24 PM.

[BluesGirl]

Thanks Fallah,

 

That's the problem because it is a new design. I have been looking for past patents for pressures and temperatures and the only range was for the absorber's operating temperature. 

[PingPong]

Make absorber mechanical design temperature equal to that of the incoming gas, or of the incoming NaOH, whichever is highest.

[BluesGirl]

Thanks PingPong. I've adjusted my design so that it is now less complicated but the trade-off is the duty to remove heat from the absorber.

 

Is it possible to put a cooling stream into a packed column? I've attached a simple diagram of what I mean and thanks for everyone's help so far.

 

 

 

 

 

Attached Files

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[PingPong]

It is possible to remove heat from a packed column by including a Pump Around section, or by drawing all liquid from some point in the column, cool it, and return it to the column just below the drawoff point.

 

In the mean time we still have no idea what this process is about.

What is the flowrate, composition, pressure and temperature of the incoming gas?

What is the flowrate, concentration and temperature of the incoming NaOH solution?

What neutralisation reaction(s) are intended to take place?

[BluesGirl]

I've decided to change the design again. Instead I will use a falling film evaporator. This way the cooling is taken in the shell side and does not interfere with the reactions in the tube. My design involves absorbing or reacting HCN with NaOH to give NaCN as the product. I haven't got the numbers at this point since my part is the last stage of the design while my team members are upstream. 

[breizh]

Bluesgirl ,

Certainly  good to read + MSDS of HCN, NaOH and NaCN .

 

Very hazardous materials !  

 

I don't understand your assignment .

 

Breizh

Edited by breizh, 31 August 2014 - 09:35 PM.

[BluesGirl]

My design involves HCN gas absorbed into NaOH. There will be two reactions: HCN+NaOH>NaCN+H2O and CO2+2NaOH>Na2CO3+H2O. You've got the right paper that I used breizh!

 

I'm now stuck at the stage of calculating the duty of the absorber. I know that it requires the heat of reactions but wouldn't I need to find the heat of reaction of HCN and CO2 in NaOH to find the 'deltaH reaction'? I eventually want that multiplied with mass flowrates to get my duty in KJ. 

Edited by BluesGirl, 02 September 2014 - 11:47 AM.