14 replies to this topic

[prateek1991]

hello guys

i am a student.. i have been asked to design a caustic scrubber system to purify a flue gas so that the final amount of so2 in d flue gas can be reduced to 50mg/nm3 h2...
i hv to solve it through aspen plus.. i have tried to find a lot on google about the same bt i am not able to find much about this process.. maximum data available is by using lime/limestone as the reagent...
i need to know the basic layout of the process as in what components will be installed in the process... what all reactions will take place.. and the basic theory of the process.. so that i can start my work over the simulation...

[Shivshankar]

Prateek,

The topic can be found in below book
CONTROL OF POLLUTANTS IN FLUE GASES AND FUEL GASES
by Ron Zevenhoven & Pia Kilpinen

http://users.abo.fi/...ho/SulphOH1.PDF
http://users.abo.fi/...ho/SulphOH2.PDF

Regards
Shivshankar

[prateek1991]

hi shivshankar...

m glad that u r tryng to help me.. but i couldnt find what i was asking in the link that u have posted..
the above link describes the process for sulphur dioxide treatment using lime/limestone. it just has brief things aboutcaustic scrubbber technique... i would need more detailed data than this... if you could help me than it would be great...

thanks
prateek

[Art Montemayor]

Prateek1991:

After seeing the positive and helpful response Shivshankar gave you, I would have thought you would have the basic education and manners to give him more than just a “token” thanks.

I have seen many lazy students come through our Forums and I had to try for myself to see how lazy this post is, so I Googled and in 0.20 seconds I got over 34,000 responses to “Sulfur Dioxide Removal Caustic Soda”.

And yet you state (in horrible and unintelligible writing: “i hv to solve it through aspen plus.. i have tried to find a lot on google about the same bt i am not able to find much about this process.. maximum data available is by using lime/limestone as the reagent...”

You have not even tried to solve your own problem. Proof of this is the attached copy I made the effort to detail out just the first two pages of Google results in order to show how lazy you are. There is so much excellent information available to you and other students on this subject that it should be embarrassing to you to have to read this result.

We on this Forum always try to help students who try to help themselves. But we will not do other people’s work for them. If you persist on depending on others to do your work for you, you are destined to fail as a student and will never become an engineer – especially a chemical engineer. I hope you take this criticism as an attempt to show you where you lack a proper engineering work ethic and you seek improvement. Good luck.

Attached Files

•  Google Results on SO2 Removal with Caustic Soda.doc   47.5KB   124 downloads

[Shivshankar]

Prateek,

Hope this helps.

http://www.ontla.on....5005/310108.pdf

Regards
Shivshankar

Attached Files

•  7 John Hatley.pdf   1.82MB   146 downloads

Edited by Shivshankar, 21 June 2012 - 01:53 AM.

[prateek1991]

hello sir...
m really sorry but i was actually obliged for shivshankar sir's help... i never meant to offend you or him in anypossible way... sir i tried to google but may be my internet skills arent that good that i could have found something related to using just caustic solution and nothing else... i never meant that i didnt find anything... i was able to understand the chemistry of the entire process.. i found the data regarding the same..

but sir what i wanted to know was that what all parts should the design consist of.. pictures foe other processes are available on google itself.. but i couldnt find the same for my project so that i could have got a basic idea for the design part..

i am a hardworking student sir and i have already completed my project... using the data that i could get i worked hard and designed the process to whatever efficiency i could have done it...

i wasnt able to find exact data on google... so i checked out for help on this website.. when i checked various posts on the same topic i found that many other students also had trouble finding the data... so i thought that maybe enough data isn't available on the net... and thats when i wrote this topic for help.. i continued my research although.. its not that i stopped working and got lazy... and finally i was able to complete the project.. i am not a lazy student sir...

once again i would like to appologise to you n shivshankar sir.. but i actually didnt mean to offend anyone of you sir...

Edited by prateek1991, 24 June 2012 - 04:21 AM.

[prateek1991]

thanks a lot shivshankar sir... i hope i didnt offend you in anyway... i am really sorry sir if i did... but i never intended to...
i definitely got a lot of help in understanding various aspects of the project in detail with your help... it helped me clear out some of my doubts.. i am really thankful for that...

regards
prateek

[Art Montemayor]

Prateek:

Well, I’ve returned after a weekend with my grandchildren at the beach, and I have found a very pleasant surprise in your positive response to my last post. I am very glad and happy to see that you obviously recognize what our Forum is trying to accomplish: to help you form a solid and positive base of learning for your future success in your career as a professional engineer. Although I can’t speak for shivshankar, I can assure you that just like me, he does not feel offended by your posts. Mature and professional engineers do not take criticism or corrections as negative inputs. Anything that helps us improve our thinking and our ability to resolve problems now and in the future is more than welcomed. The only thing that an engineer takes personally is the challenges that confront him – not the individuals.

Bear in mind that we are always subject to being taught and corrected – especially when our solutions and calculations are wrong. This occurs early on when our teachers and supervisors try to teach us the basics, when our mentors instruct us and critique us in our first assignments, when our peers check our calculations and solutions, and finally when our clients check and correct our work product and our engineering solutions. We cannot take these corrections and criticisms as nothing but positive input during our career. And we are supposed to learn by our mistakes. This is called Lessons Learned. And we should never repeat prior mistakes.

I hope that you have learned how easy it was to find a large amount of detailed and specific data on what you are working on. As you have seen it took me less than a minute to find it through Google. You should now be prepared to start the specific and step-wise presentation of your assignment: detailed schematic diagrams, detailed heat and mass balances, detailed sketches of the major equipment (packed tower, etc.) and a complete and detailed discussion of the process.

Please feel free at any time to consult with our Student Forum if you have need for advice or have specific questions on this project or anything else. I hope you now know that we are here to help you – but not on your conditions. We know better what confronts you and what you need to do to succeed. That is why our conditions should prevail in assisting and helping you identify the real problem and how to obtain the solution(s).

Good luck to you and happy engineering.

[Shivshankar]

Art,
Thanks for your encouraging and positive words and guidance to new member/student Prateek.

Prateek
You are most welcome. I hope you can learn many things through our chE forum and the guidance you recieve from experienced member like Art.

Regards
Shivshankar

Edited by Shivshankar, 26 June 2012 - 02:40 AM.

[prateek1991]

sorry sir i got busy with the report making process of my project. i just saw your reply to the post. I am glad sir that i've been able to change your opinion about me. And yes i took your criticism positively. I understand sir that whatever you told me was for my benefit only. Being a student i would be lucky if i'll keep getting help from our seniors. once again sir thanks a lot to both of you.

regards
prateek

[Ra v]

Dear Shivashakar,

In our Co2 plant we have DCc/So2 removal unit where we use to remove Sox with Na2co3. As i dont know how much sulfur content present in the fuel we are using (Diesel).

What are the parameter we need to look for 90-95 Percent Sox removal. As we are just depending on the PH of the Surubber outlet. IS that sufficent . and what happen if the PH will go high/low in flue gas .

Rgs
A Ravi

[Santoshp9]

Dear Alamuri Ravi,
Find attached my FGD system design calculation sheet, may be it will help you.

Rgds,
Santosh

Attached Files

•  Process calc 21.02.2011 FGD.xls   537.5KB   132 downloads

[Ra v]

Dear Santosh,

Thanks for the reply , but the data is not rleated to my question.

i just want to know what are the parameters we need to look in for maitaining the system in good performance.

rgs
A Ravi

[kkala]

1. Let us first assume washing water to contain only SO2, 0.1 % w/w, and having temperature t=60 oC (so t= 60 oC for gases out of scrubber too). Under such conditions partial SO2 at equilibrium over washing water is 13.5 mm Hg (Perry, 7th ed - 1997, Table 2-11 (*), p. 2-77). Partial pressures of rest gases out are H2O = 149.4 mm Hg (from steam table **) and dry air = 760 - 149.4 - 13.5 = 597.1 mm Hg. Emitted SO2 (dry basis) would be higher than 13.5/(597.1+13.5)=0.0221 kmol SO2 /kmol, that is 0.0221x64000/22.414 = 63 g SO2 per Nm3 of dry gas out. Local emission standards for large combustion plants call for 1.7 g SO2 / Nm3 (dry basis) or much lower. At any case mentioned 63 g SO2 / Nm3 would be too high to be acceptable.
2. You can adjust above calculation to actual plant data (even by estimate, if something not known) and see result, most probably similar. This can verify that pH of washing water has to be maintained in the alkaline region (to pH value probably recommended by scrubber supplier) to assure low enough vapor pressure of SO2. Low SO2 concentration in wash water is obtained by converting most of its SO2 content to SO3^-. Otherwise you would need excessive make-up of washing water (and blow down) to keep emission standards.
Example not needing pH adjustment of wash water is HF scrubbing in phosphoric acid reactors. But 0.1% w/w HF solution has about 0.016 mm Hg vapor pressure of HF at 60 oC (F Riesenfeld - A Kohl, Gas Purification, Gulf, 1974).
3. Low efficiency can be the result of inefficient contact between SO2 and washing water, but it is assumed that the scrubber has been tested and has satisfactory operation as long as it is not charged with scales or low water circulation. Among operating parameters pH of wash water is judged as most important for this case. Variation of wash water / exit gas temperature (60 oC in the example) is usually not wide. Higher pH is not bad concerning efficiency, yet more alkali is waisted.
Notes:
(*) Table 2-11 seems to report only partial pressures of SO2, not of "H2O and SO2" (typo). Concluded from Perry, 4th ed (1963), Table 3-12 (p. 3-61).
** Actually partial H2O vapor pressure is expected a bit lower to steam table value, but this is insignificant for such low SO2 concentrations.

Edited by kkala, 28 December 2012 - 04:18 PM.

[Ra v]

Thanks for the reply

Rgs
A Ravi