5 replies to this topic

[gvdlans]

First comment is that if possible you should seek help from within your organization i.s.o. going to the Internet.

Second comment is that following book may be useful: Gas conditioning and processing : Vol II: the equipment modules / by John M. Campbell. - 7th ed. - Norman : Campbell, 1992. - 444 p. - (Campbell Petroleum Series).

Other reference is the GPSA Engineering Data Book, 11th edition, section 20 (Dehydration).

[Art Montemayor]

Rex:

I am presently not at my home office where I keep extensive information on Adsorption Drying. First, allow me to ask a few pertinent questions:

1. Since this is an Industrial Professionals Forum, I assume you are trying to process and mechanically design an adsorption dryer for use in your process plant. Is this true? The reason for this question is that almost all production and industrial-based engineers specify their adsorption dryer requirements to established and recognized companies that design and build the adsorption units on a warrented performance basis.

2. If you have no prior experience in designing and or modifying adsorption units, how are you (or your employer) going to put any confidence on the resulting product of your first attempt at this?

3. You state that you "have no idea what are the deliverable". I sincerely hope this statement is a product of your bad use of the English language, because if it is not then I offer this question: If you don't know what you are expected to deliver, how do you intend to design towards an unknown goal??? This simply doesn't make sense for an engineer; I hope this is just bad communications on your part.

4. What gas, what composition, and at what feed pressure, temperature and moisture content are you to dry?

5. What product moisture content do you require? -- this embarrassing question is related to what I stated in #3, above.

6. What heat source do you have available for the regeneration gas stream? -- steam (pressure & temperature)? electricity? thermal heating fluid?


Another source for gas dehydration (or adsorption drying) information is Kohl & Reisenfeld's book: Gas Processing.

I have designed and built a considerable amount of gas adsorption dryers for process pressure from 100 psig to 5,000 psig - for use on CO2, Oxygen, Nitrogen, Carbon Monoxide, air, methane, and others. What I can basically identify as first procedures you must do are the following:

1. Select your adsorbent; if you are only drying (removing H2O), then I strongly recommend you pick Activated Alumina.
2. Select your regeneration cycle; here there are many ways you can do the regeneration - with a pressurized, humid gas by-pass system or a sacrificial dry product gas recyle. There may be other options, depending on your needs and gas. Is the regeneration going to be based on thermal energy (TSA) or on pressure energy (PSA)?
3. Select the number of adsorption "towers".
4. Determine if the operation will be automatic or manual in changing out the towers.
5. Determine the TEMA cycle you will employ; sometimes this is based on how you operate the dryers themselves. For example, if you have a continuous process with shift operators, you may desire to have a tower regeneration per shift or per day - all depending how you want to run your operation.
6. If you are going to use a TSA regen cycle, then determine how you will cool the regen gas stream - with cooling water or with air?

There are many other points I could pass on to you, but I've already given you more written, specific and detailed information than the meager 5 short sentences you furnished as your query and basic data. I need much more (or all) basic data and scope of work to understand how and what you intend to do and what your query is based on in order to fully give you all you require to proceed forward. The quality of the response is directly proportional to the quality of the query. Perhaps if you furnish ALL the specific basic data and your scope of work, we may be able to help you out further.

I hope the above is enough to get you started in what you intend to do. Good Luck.

Art Montemayor
Spring, TX

[sskumar]

Art Montemayor:
I have a doubt regarding drying.
Normally people recommend Activated Alumina for drying. Why silica gel or molecular seives are not recommended. In our plant we are using activated alumina as adsorbent for dryers of compressed air plant and we are using TSA and dew point at the outlet is -40degC. In our nearby Captive Power Plant, they are using silica gel for their air dryers and they also use TSA. I heard people say that the crushing strength of silica gel is less and hence they are not recommended for high pressure operation. But in our plant and in Captive Power plant, the dryer operating pressure is the same , 9atm abs. Then where is the difference?

Also, in our Air separation plant, we have dryers for removing moisture and other impurities(like CO2,H2S, hydrocarbons etc ) from air. Dryer is divided into two portions. In the first portion, moisture will be removed by activated alumina and then in the second portion other impurties will be removed by Molecular Seives. People here say that inorder to reduce loading on Molecular Seives, activated alumina is used to remove the moisture. I think molecular seives can as well remove moisture. Then why activated alumina is provided? Here in this case both TSA and PSA are being used to get dew point of -100 degC.

Please tell me the advantages with activated alumina and disadvantages with silica gel and molecular seives for air drying.

Thank you,
Regards
sskumar

[Art Montemayor]

sskumar:

I can easily answer in great detail the specific questions you ask on your adsorption drying applications. However, in all fairness to Rex - who started this thread - and in order to avoid confusion and multiple responses on multiple subjects, please re-submit your query as a completely different thread. This way, we can all focus specifically on your query and address your specific concerns.

I believe this thread belongs to Rex and in fairness to him, I'm going to address his concerns if and when he responds.

I hope you understand the confusion that could result from trying to handle two different queries on the same thread.

I'll await your re-posting of your specific questions. Don't forget to submit all the available basic data you have at your disposal. The more details and data that you furnish, the more complete and detailed the response(s) will be.

Art Montemayor
Spring, TX