4 replies to this topic

[Ross1994]

Hey all,

 

I've been tasked to design a molecular sieve in order to separate water from a liquid mixture comprising of: Ethane; Ethylene; Water and Hydrogen. 

 

System Parametres

 

System pressure = 300kPa

System temperature = 292.5K

 

Inlet Stream

 

Ethane: Mole fraction = 0.035             Molar flow = 54.495 kmol/hr

Ethylene: Mole Fraction = 0.4788      Molar flow = 745.4916 kmol/hr

Water: Mole Fraction = 0.0074            Molar flow = 11.5218 kmol/hr

Hydrogen: Mole Fraction = 0.4788     Molar flow = 745.4916 kmol/hr

 

Outlet Stream 01

 

Water: Mole fraction = 1     Molar flow = 11.59 kmol/hr

 

Outlet Stream 02

 

Ethane: Mole fraction = 0.0352          Molar flow = 54.4192 kmol/hr

Ethylene: Mole fraction = 0.4824       Molar flow = 745.7904 kmol/hr

Hydrogen: Mole fraction = 0.4824     Molar flow = 745.7904 kmol/hr

 

The above information is the information surrounding the molecular sieve and if anyone could point me into the right direction in terms of the chemical / thermodynamic calculations and equations that would be greatly appreciated.

 

If any more information is needed please let me know and I will fill in the gaps as best as possible.

 

Cheers!

[Art Montemayor]

Are you stating that your feed stream exists in the LIQUID phase at 300 kPa and 292 K?

[Ross1994]

Hey Art,

 

The inlet stream enters as a gas and exits as a gas as the system pressure and temperature remains constant through out the adsorption process.

 

Cheers!

[Art Montemayor]

Ross 1994:

 

First and foremost I want to draw your attention to the existence of our SEARCH MACHINE.  By use of this feature, you will find numerous threads where this very adsorption drying subject is discussed and a lot of useful information is given as well as helpful tips and literature on the methods and steps used to calculate the design of an adsorption dryer.  Additionally, some of our experienced and knowledgeable members, like Ankur Srivastava, have even written blogs and submitted spreadsheets on calculations and design of adsorption dryers on this website.  Zauberberg is another veteran member who has a rich background of hands-on adsorption dryers regarding their design and operation and has contributed useful information in many past threads.  You should peruse through our website where you will find much information on adsorption drying.

 

In your opening sentence in your initial post, you wrote: "I've been tasked to design a molecular sieve in order to separate water from a liquid mixture".  Now you have changed the important basic data, stating that the feed stream is in the gaseous phase.  Please accept some valuable advice: as a future professional engineer, you must communicate with your peers in a concise, accurate manner or your career will suffer.  You should be careful of stating the correct phase of a mixture stream.

 

You request us to point you in the right direction in terms of the chemical / thermodynamic calculations an equations involved in adsorption drying and the best advice I can offer you is to obtain, read, study, and fully understand the materials found in the following texts and documents:

• Kohl & Nielsen, "Gas Purification", Chapter 12
• John Campbell's "Gas Conditioning and Processing"
• The GPSA Engineering Databook
• John M. Campbell's Tip of the Month (found at: http://www.jmcampbel...-of-the-month/)

Also download and study the documents and literature I am attaching to this thread.  Besides keeping you busy learning useful and profitable information on the adsorption Unit Operation, you will acquire an indepth method of learning the way an adsorption unit is designed.  Basically, the design of an adsorber tower must consider:

• Cycle time;
• Allowable gas flow rate;
• Desiccant type, identification, and capacity;
• Required outlet water dewpoint (which you have failed to even mention);
• Total amount of water to be removed;
• Regeneration type, cycle, and requirements.

I hope this helps you in your assigned task.

 Adsorption Design Guide - US Army Corp of Engrs.pdf   754.64KB   56 downloads

 Ankur Mol Sieve Water Adsorption - Natural Gas.xlsx   290.86KB   55 downloads

 How-To-Guide for Adsorber Design.pdf   510.39KB   55 downloads

[Ross1994]

Art Montemayor

 

Thank you for all the information you've sent my way. I'll aim to read and understand everything and will make sure I'm in contact with yourself and the other members you have suggested.

 

Once again thank you for taking the time out to respond to my query.

 

Kind Regards,

 

Ross.