3 replies to this topic

[Nishith Sahoo]

Hi everyone,

I am working on a NH3 scrubber that is connected to an ammonolysis reactor. After the reaction unreacted NH3(g) is vented to a scrubber. Scrubber media is H2O.

 

The formulas available in books for the design of the same are for the following conditions:

1. The feed contains the contaminant in a mol fraction <<1

2. The volumetric flow rate remains effectively same (assumption)

 

The scrubber which I am designing is for:

1. Feed mol fraction of contaminant= 1. (only ammonia is vented)

2. Complete absorption of ammonia is required. Hence volumetric flowrate of gas would decrease  significantly from the tower bottom to top. A blower is present at the outlet of scrubber to decrease the ppm level of the unabsorbed contaminant.

 

Please help me or provide me with some link on the design of this kind of scrubber.

Edited by Nishith Sahoo, 27 October 2015 - 06:50 AM.

[breizh]

Hi,

 

Consider the resources attached to support your work.

 

Hope this helps

 

Breizh

[Nishith Sahoo]

Dear Breizh,

First of all thanks for such quick response.

 

I had already gone through this file before I posted here. My doubts still remain the same. The points I have written in my first post are based on this document and Mass Transfer Operation by Treybal. The difference is that in the scrubber I am designing, its going to scrub the entire feed of pure ammonia gas. Hence the gas flow rate is going to decrease by, say about 90-95%. Also in my case Y is not defined due to the fact that its pure NH3 gas (mole fraction of air=0).

The opposite of these two conditions are what the derivations are based on in this file.

 

If possible please explain me how can the specific points that I had mentioned in the first post can be taken care of if we are going to design by this file? Or is there any separate method for design for the case I want to work on?

 

Thank you.

Edited by Nishith Sahoo, 30 October 2015 - 05:07 AM.

[breizh]

Hi ,

It seems to me that you will have to perform heat and mass balances along your column . It's not so simple .

 

How to proceed, : assume a thermal profile and perform the calculations on height dz of the column . Iterative calculation.

 

Probably 2 beds with recirculation loop of liquid passing through a cooler ( HX ) to maintain a temperature profile . The top bed will be fed by fresh water to recover the ppm of NH3  .

 

Good luck

Breizh