11 replies to this topic

[Dragos]

Hello,

I am a student pursuing a Master's Degree in Env. Eng. and I have chosen for my final thesis SO2 reduction from a copper smelter using a packed tower. I want to do this design in Aspen Plus. I have chosen a mixture of air and SO2 (0.98, respectively 0.02 standard vol. fraction) and water/ammonia (0.8/0.2 mass-fraction) as feed streams entering a RadFrac column (see attachment). The problem is that I don't see the products of reaction in the liquid-out stream, despite defining the reaction. I am novice in Aspen Plus so please give me some advice. What do I do wrong?
Is there anything I need to add to the reactions? Products of reaction? Other flowsheet or column type? Why do I get so much ammonia in the gas stream leaving the absorber? Why don't I see the ammonium sulfite in the liquid-out stream?
Please any help is highly appreciated!

Attached Files

•  AMONIAC.zip   425.66KB   157 downloads

[Dazzler]

Hello Dragos

I'm at home so cannot open your Aspen+. But these things come to mind from your question.
1. Ammonia is very volatile. Higher flow and concentration will be exiting the column for higher air flow, higher temperature etc. Perhaps you should be scrubbing with something else less volative. I used to work with 33% NH3 solution. The vapours from this were so bad you could not breath at all. If using ammonia solution to scrubb, you may need a second water scrubber to then remove the ammonia. Perhaps a caustic solution (NaOH) would be better.
2. Are you sure you have appropriate physical properties package ? This may effect the resutls and reactions.
3. Products of reaction may be ionic sulphate SO4(-2) and ammonium NH4(+1) in solution, not just whole molecules.

Dazzler

[Dragos]

Hello Dragos

I'm at home so cannot open your Aspen+. But these things come to mind from your question.
1. Ammonia is very volatile. Higher flow and concentration will be exiting the column for higher air flow, higher temperature etc. Perhaps you should be scrubbing with something else less volative. I used to work with 33% NH3 solution. The vapours from this were so bad you could not breath at all. If using ammonia solution to scrubb, you may need a second water scrubber to then remove the ammonia. Perhaps a caustic solution (NaOH) would be better.
2. Are you sure you have appropriate physical properties package ? This may effect the resutls and reactions.
3. Products of reaction may be ionic sulphate SO4(-2) and ammonium NH4(+1) in solution, not just whole molecules.

Dazzler

Hello Dazzler, and thank you very much for your reply. How can I send you my Aspen Plus simulation? Perhaps uploading to an ftp would be helpful for you? Here are my answers based on your reply.
1. I want to try using ammonia just for my knowledge. Maybe I am wrong and I don't need than much ammonia in the solution. I would be interested in using NaOH as well.
2. No. That's why I needed an advice of a professional.
3. Only these besides SO2, air, water and ammonia?

[Dazzler]

Hi Dragos

Unfortunately I can't help any further with Aspen+, but I stress that scrubbing of the SO2 is best with a non-volatile alkaline solution. There are many of these, but a couple of traditional inorganic ones are noted in the first reference below.


http://en.wikipedia....desulfurization


In the next reference you'll see a well known process for capturing and converting the SO2 into a saleable product - sulphuric acid.

http://en.wikipedia....ic_acid_process


If you are still keen to use ammonia, then if you generate a very strong solution of ammonium sulphate then this may be useful as a fertiliser. You will still have to then treat the vent stream for ammonia.

Dazzler.

[milenkom]

Hello,

I am a student pursuing a Master's Degree in Env. Eng. and I have chosen for my final thesis SO2 reduction from a copper smelter using a packed tower. I want to do this design in Aspen Plus. I have chosen a mixture of air and SO2 (0.98, respectively 0.02 standard vol. fraction) and water/ammonia (0.8/0.2 mass-fraction) as feed streams entering a RadFrac column (see attachment). The problem is that I don't see the products of reaction in the liquid-out stream, despite defining the reaction. I am novice in Aspen Plus so please give me some advice. What do I do wrong?
Is there anything I need to add to the reactions? Products of reaction? Other flowsheet or column type? Why do I get so much ammonia in the gas stream leaving the absorber? Why don't I see the ammonium sulfite in the liquid-out stream?
Please any help is highly appreciated!

I was looking into your problem when I was disturbed by my ex-girlfriend and we had a big fight. Before that happened I managed to look into your simulation file. I noticed reaction you entered wasn't included in stage reactions at absorber unit. Also I'm not sure whether your mass balances are ok, because I'm not sure about the reaction itself is correct take a look at following link:

http://www.freepaten...03/0108469.html

Source quotes that final product of reaction is ammonia sulfate and not ammonia sulfite. Ammonia sulfite is further oxidized by oxygen to form ammonia sulfate which should be final product of reaction. Please take a look at documents I just can't do it right now since I'm still a bit shook up.

[Dragos]

Hello,

I am a student pursuing a Master's Degree in Env. Eng. and I have chosen for my final thesis SO2 reduction from a copper smelter using a packed tower. I want to do this design in Aspen Plus. I have chosen a mixture of air and SO2 (0.98, respectively 0.02 standard vol. fraction) and water/ammonia (0.8/0.2 mass-fraction) as feed streams entering a RadFrac column (see attachment). The problem is that I don't see the products of reaction in the liquid-out stream, despite defining the reaction. I am novice in Aspen Plus so please give me some advice. What do I do wrong?
Is there anything I need to add to the reactions? Products of reaction? Other flowsheet or column type? Why do I get so much ammonia in the gas stream leaving the absorber? Why don't I see the ammonium sulfite in the liquid-out stream?
Please any help is highly appreciated!

I was looking into your problem when I was disturbed by my ex-girlfriend and we had a big fight. Before that happened I managed to look into your simulation file. I noticed reaction you entered wasn't included in stage reactions at absorber unit. Also I'm not sure whether your mass balances are ok, because I'm not sure about the reaction itself is correct take a look at following link:

http://www.freepaten...03/0108469.html

Source quotes that final product of reaction is ammonia sulfate and not ammonia sulfite. Ammonia sulfite is further oxidized by oxygen to form ammonia sulfate which should be final product of reaction. Please take a look at documents I just can't do it right now since I'm still a bit shook up.

Thanks alot milenkom. I will check these out and if I don't manage I will let you know. What do you mean by: I noticed reaction you entered wasn't included in stage reactions at absorber unit.?

[Dragos]

Hello,

I am a student pursuing a Master's Degree in Env. Eng. and I have chosen for my final thesis SO2 reduction from a copper smelter using a packed tower. I want to do this design in Aspen Plus. I have chosen a mixture of air and SO2 (0.98, respectively 0.02 standard vol. fraction) and water/ammonia (0.8/0.2 mass-fraction) as feed streams entering a RadFrac column (see attachment). The problem is that I don't see the products of reaction in the liquid-out stream, despite defining the reaction. I am novice in Aspen Plus so please give me some advice. What do I do wrong?
Is there anything I need to add to the reactions? Products of reaction? Other flowsheet or column type? Why do I get so much ammonia in the gas stream leaving the absorber? Why don't I see the ammonium sulfite in the liquid-out stream?
Please any help is highly appreciated!

I was looking into your problem when I was disturbed by my ex-girlfriend and we had a big fight. Before that happened I managed to look into your simulation file. I noticed reaction you entered wasn't included in stage reactions at absorber unit. Also I'm not sure whether your mass balances are ok, because I'm not sure about the reaction itself is correct take a look at following link:

http://www.freepaten...03/0108469.html

Source quotes that final product of reaction is ammonia sulfate and not ammonia sulfite. Ammonia sulfite is further oxidized by oxygen to form ammonia sulfate which should be final product of reaction. Please take a look at documents I just can't do it right now since I'm still a bit shook up.

Thanks alot milenkom. I will check these out and if I don't manage I will let you know. What do you mean by: I noticed reaction you entered wasn't included in stage reactions at absorber unit.?

milenkom, what property methods&models should I choose for this app? Moreover, do these reactions occur in separate stages of the absorber?

[Dragos]

Hello,

I am a student pursuing a Master's Degree in Env. Eng. and I have chosen for my final thesis SO2 reduction from a copper smelter using a packed tower. I want to do this design in Aspen Plus. I have chosen a mixture of air and SO2 (0.98, respectively 0.02 standard vol. fraction) and water/ammonia (0.8/0.2 mass-fraction) as feed streams entering a RadFrac column (see attachment). The problem is that I don't see the products of reaction in the liquid-out stream, despite defining the reaction. I am novice in Aspen Plus so please give me some advice. What do I do wrong?
Is there anything I need to add to the reactions? Products of reaction? Other flowsheet or column type? Why do I get so much ammonia in the gas stream leaving the absorber? Why don't I see the ammonium sulfite in the liquid-out stream?
Please any help is highly appreciated!

I was looking into your problem when I was disturbed by my ex-girlfriend and we had a big fight. Before that happened I managed to look into your simulation file. I noticed reaction you entered wasn't included in stage reactions at absorber unit. Also I'm not sure whether your mass balances are ok, because I'm not sure about the reaction itself is correct take a look at following link:

http://www.freepaten...03/0108469.html

Source quotes that final product of reaction is ammonia sulfate and not ammonia sulfite. Ammonia sulfite is further oxidized by oxygen to form ammonia sulfate which should be final product of reaction. Please take a look at documents I just can't do it right now since I'm still a bit shook up.

Thanks alot milenkom. I will check these out and if I don't manage I will let you know. What do you mean by: I noticed reaction you entered wasn't included in stage reactions at absorber unit.?

milenkom, what property methods&models should I choose for this app? Moreover, do these reactions occur in separate stages of the absorber?

Did what you indicated but no use. I get the following error: ***SEVERE ERROR
REACTIVE FLASH FAILURE INSIDE LOOP RMSERR = 0.1938 OUTSIDE LOOP RMSERR
= 5.3079D-05 COMPOSITE FEED FLASH FAILED TO CONVERGE; SUPPLY T-EST,
X-EST AND Y-EST AS A WORKAROUND. What is wrong with my file? I attached the modified one.

Attached Files

•  New Folder.zip   416.59KB   88 downloads

[saeed.s]

Hi Dragos,
unfortunately , i could n't open your file because of incompatible version , anyway , i do n't know did u do this procedure or not ? if u did n't plz do it and try again.
Open radfrac block and select convergence and go to advanced , now, in front of absorber option change no to yes.
good job

[Dragos]

Hi Dragos,
unfortunately , i could n't open your file because of incompatible version , anyway , i do n't know did u do this procedure or not ? if u did n't plz do it and try again.
Open radfrac block and select convergence and go to advanced , now, in front of absorber option change no to yes.
good job

I know about this option. I will look home if I selected or not and let you know. Now I'm at work. Thanks.

[Dragos]

Hi Dragos,
unfortunately , i could n't open your file because of incompatible version , anyway , i do n't know did u do this procedure or not ? if u did n't plz do it and try again.
Open radfrac block and select convergence and go to advanced , now, in front of absorber option change no to yes.
good job

Hello again. Unfortunately it doesn't work this way either. I get the same error message.

[milenkom]

Hi Dragos,
unfortunately , i could n't open your file because of incompatible version , anyway , i do n't know did u do this procedure or not ? if u did n't plz do it and try again.
Open radfrac block and select convergence and go to advanced , now, in front of absorber option change no to yes.
good job

Hello again. Unfortunately it doesn't work this way either. I get the same error message.

Hi, Dragos. First of all I myself had a hugh problems with the simulation. What you need to do first of all is to calculate mass balances yourself until your know for sure they are as watertight as mermaid's brazeer. Once you've got mass balances worked out then you can move to simulation. I had problems with simulation since something was wrong with reactions. Yes reactions will occur on all stages I presume. Start reading more about it, I have found article which describes desing of the column in details I think. I just can't be bothered with simulation right now, but I am positive it can be simulated properly. About the property methods selected I'm really not sure yet. Try basic gas property methods like SRK, RK could be NRTL as well. Concentrace first on design do the simulation later when your mass and energy balances hold water.