2 replies to this topic

[chemperson]

Dear all

I have some doubts while working on SWS simulation

-What is the benefit of using pump around rather that reflux in the h2s and nh3 column.
-Why two feed locations specified in NH3 column what type of flexibility we expect while doing like that
-When we are going for single column for stripping H2S and ammonia . Please let me know the limitations of
SRU because that will be governing I think.
- How to control the pH of stripped water.



Thanks

[Technical Bard]

The benefit of a pumparound for reflux is that an overhead condenser will see very high concentrations of NH4SH in the condenser, and risks salt deposition and corrosion. This is particularly true if you have cyanide (CN-) or formate (HCOO-) present in the system.

The dual feed locations are to allow operations to change the feed tray if they are having trouble meeting the stripper water spec, or if they are not having trouble to attempt to reduce the reboiler steam requirement. This is because the simulations of such units are difficult to get completely right due to the influence of species in the water that you may not have included in the model.

If you are running a significant NH3 concentration to the SRU, the SRU must be designed for ammonia destruction - this may require special burners, reaction furnace design to obtain the required combustion temperatures to convert NH3 to N2. Failure to do so will result in ammonium salts depositing in the sulfur condensers and fouling the unit.

The pH of stripped water is usually controlled via caustic addition in the bottom 3-4 trays of the column to ensure that the ammonia spec can be met.

[chemperson]

Thanks for replying....

One more thing I have to know that normally I am putting ammonia column bottom water as wash water to H2S column above feed tray to avoid ammonia escaping from H2S column top.

Now whether I can directly add that wash water in pump around because it will further reduce my reboiler duty . Any suggestion you can give