5 replies to this topic

[21abi]

hello sir
i m abhijit from bsc chemistry student i need to know related to calculation of scrubber design n i m having totally new subject so sir pls help which books should i refer. one of my friend given me this sheet http://www.scribd.co...scrubber-design how this calculation done pls help i m totally in mess.
i m desperately need some help pls i m waiting sir,,,,,,,,,,,,,,,,need some basic knowledge about scrubber n sheet
thank u sir

Attached Files

•  scrubber design from cheresources (Autosaved).xls   712.5KB   1069 downloads

[kkala]

Do not allow panic, but try to be systematic and assimilate as much as possible. Clarification on the time allowed for this project of scrubber elementary design should have been given.
1. First start with basics. Read e.g. the Chapter on "Gas Absorption" from the book "Unit Operations of Chemical Engineering" by W McCabe, J Smith, P Harriot (McGraw-Hill, several editions); or from your book of Unit Operations, if you are familiar with it. Good books on the subject have been also published in India, using SI units. This may be the most important step.
2. Then go to something more specific, e.g. "Gas Purification" by A Kohl and F Riesenfeld (several editions and probably several publishers, 2nd edition is by Gulf publishing Co in 1974) and study "Hydrogen Chloride Absorption" in the Chapter "Water as an Absorbent". Probably you can easily find the book in the University library, since it is well known. It is true that supplied data is limited compared to e.g. HF in the same book.
You can find almost nothing about HCl in another book, "Gas Purification Processes" by G. Nonhebel (Butterworths, 1972).
3. Look at http://www.cheresour...n-hcl-scrubber/ '> http://www.cheresour...n-hcl-scrubber/ . Note that enthalpy concentration diagram for aqueous HCl can be found in Perry, if needed (Fig 2-11 in the 7th edition of 1997).
4. Searching the Web, you can find more information, useful or not (e.g http://cr4.globalspe...71/HCL-scrubber '> http://cr4.globalspe...71/HCL-scrubber , or http://www.aat.cc/store.asp?pid=26896 '> http://www.aat.cc/store.asp?pid=26896 ). Mists of hydrochloric acid need higher pressure drop, but you can have simplifying assumptions for a student project.
5. Attachment to your post indicates a packed tower containing intallox saddles. After the above, you can be familiar with terminology and use the example of the attachment for a preliminary design, assuming you select a similar packed tower.

Having worked in fertilizers in the past (1975-81), we had elaborated process duty specs for HF / SiF4 scrubbers for bidders; but we had not used packed towers due to scales.

[breizh]

Abi ,
Consider this resource it should help.
Take some time to read the material attached.

Breizh

Edited by breizh, 21 June 2012 - 05:59 PM.

[Mark-TR]

Hi

I found this article in this site with some information that may be interesting for you.

http://www.cheresour...ckle-lines?pg=1

I'm also involved in a job designing an HCl scrubber for removing the HCl discharged from safety valves in a Process Unit. The safety valves discharge to the scrubber and the scrubber overhead vapor discharges to the flare system.

The scrubbing media used is water with 6% NaOH and the fluid to be scrubbed is a HC with a MW of 36.6 at 111 ºC and 1,000 ppm of HCl. The operating pressure varies between 0.3 - 0.9 barg. The scrubber is a packed tower with Intalox saddles and is made of Carbon Steel.

I lack the experience designing this kind of equipment, in the sense that I do not know the typical efficiencies and the HETP that should be considered for this design nor the safety factor or key points to note in the datasheet.

I´m currently modeling the tower with ASPEN, using the electrolytic NRTL and radfrac block design models.

Furthermore, our client is requesting an internal coating of the scrubber to avoid internal corrosion. Does anyone have any experience with internal coating in a packed tower? it seems to me that this might not be a good approach.

Any advice would be of great help.

Kind regards,

Edited by Art Montemayor, 29 June 2012 - 07:39 AM.

[Art Montemayor]

<sup>Marcos,

Normally I would advise you to post your query on your scrubber design in a new, independent thread within this Forum in order to address it separately from the topic in this thread. But since you have responded to the OP’s request, I’ll go ahead and comment on your query. In the future, however, always start your own query in a new thread. That way, we don’t confuse issues within the same thread.

I have designed and operated a lot of SO₂ and SO₃ water scrubbers in the past. The corrosion was terrible and we tried all sorts of coatings. The results were worse than the corrosion because of the continued corrosion, downtimes, and the coating maintenance. We finally resolved the problem by making the scrubbers out of large, ceramic pipe that had a hard, porcelain-type internal fired coating. We did this in South America where I obtained the fabrication of the pipe in a kiln factory owned by an old Spaniard who started his business in the country making tile and drainage pipe. This is just an idea, but if you are located in Spain, the source of considerable tile and porcelain technology, you might try this approach. The 2 meter diameter pipe was constructed as “bell-and-spigot” joints and the pipe lengths were stacked one on another.</sup>

[Mark-TR]

thanks art,

I take your advise, for future threads I will post in a new subject. I really appreciate your advise. I think I´ll propose to keep the design in carbon steel. this because in normal conditions no HCl should go to the scrubber. it is only under emergency scenarios where HCl goes to the scrubber. as you state I think I will propose to avoid the coating and therefore is better to increase the corrosion allowance to avoid maintenance problems

I have some other query, but I will start a new thread as advised.

regarding the subject of this post I will also advise to study chapter 14 of perry´s chemical engineering handbook. If somebody is interested in absorption with chemical reaction. This chapter is also good to read.

kind regards