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Packed Column Design

packed column distillation column column height

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#1 Skylar

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Posted 10 June 2019 - 11:12 AM

Hi all,

I am currently doing a column design assignment and is required to calculate the column height. From literature, it states that packing height = HETP * Number of theoretical stages. However, I would also like to know if there is a general rule of thumb to approximate the height for liquid and vapor flow at the top and bottom of the packing respectively to obtain the total column height. 

 

Thank you and looking forward to responses

 

Best regards,

Skylar


Edited by Skylar, 10 June 2019 - 11:18 AM.


#2 Pilesar

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Posted 10 June 2019 - 12:54 PM

The liquid sump is sized for vapor disengagement and for liquid holdup. Sizing depends on where you send the liquid and how the level is controlled. You will need somewhere between one and seven minutes of liquid residence time in the sump. If you have no clue, guess five minutes. The vapor space at top depends on the space required for your liquid distributor. If you feed to the middle of the column, you will have at least two packed beds and will need space between them to fit the redistributor. For your column design assignment, you should probably do the column design to find out what heights you need! You will likely need a manway at the top, bottom, and middle also, so take that into account. So allow three feet height as minimum to include manway space unless you are using body flanges instead of manways. Don't scrimp on the height as a foot or two extra won't matter much on cost. If expressing height in relation to column diameter (D), I would expect your final design to have 1 to 1.5 D between the top bed and top column tangent, 1.5 to 2 D between beds. There also should be vapor space above a reboiler return to allow the vapor to distribute. Give the sump about 1.5 feet of vapor space above the reboiler return and at least 1 foot of vapor space below the reboiler return. Size the remainder of the sump based on required liquid residence time. These numbers are what you might find to be ballpark results, but they do not take the place of calculations and reasoned sizing criteria. See if you can locate similar designs for comparison with yours. Your column will also have a skirt to raise the bottom of the column above the ground. Skirts are generally 6 to 20 ft high to provide the pump with extra suction pressure above the liquid boiling pressure. A 10 foot skirt is common. Add another foot at the top of the column if you need room for a demister pad. 



#3 breizh

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Posted 10 June 2019 - 06:45 PM

https://www.chemical...random-packing/

 

Hi ,

Using my favorite search engine , please consider the link above .

 

most probably you should get hints using Perry's chemical engineer's handbook , Coulson Richardson , Ludwig or other bibles

 

Good luck

Breizh 



#4 breizh

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Posted 11 June 2019 - 08:44 PM

hi ,

About hydraulic it could be worth to read this guideline .

 

good luck .

 

Breizh

 

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#5 breizh

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Posted 11 June 2019 - 08:49 PM

hi ,

another document about absorption supplied by EPA ,available on internet .

hope this is helping you and others

Breizh

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