STAGED COLUMN DESIGN

K. M. Tanvir AhmmedLecturer, ChE, BUET

TYPES OF TRAY

• Bubble cap tray : old

• Sieve tray : simple

• Valve tray : modern usage

BUBBLE CAP TRAY

BUBBLE CAP TRAY• Advantages

– flexible : operates satisfactorily at very high and low liquid flow rates

• Disadvantages– high entrainment:

requires higher tray spacing

– significant liquid gradient

– problems with coking, high fouling mixtures

– expensive– Poor turndown

performance

BUBBLE CAP TRAY (CONT’D)

SIEVE TRAY

SIEVE TRAY (CONT’D)• Advantages

– easy to manufacture– inexpensive– considerable design

information is available

– efficiency is good at design condition

– very good in fouling applications

• Disadvantages– turndown is poor

(efficiency falls below the design condition)

– not flexible

VALVE TRAY

VALVE TRAY (CONT’D)• Advantages

– better turndown ratio

– more flexible– new industrial

columns are more likely to have valve trays

• Disadvantages– Higher pressure

drop than sieve tray– 20% more

expensive than sieve tray

– more likely to foul or plug in case of dirty mixtures

VALVE TRAY (ONE-PIECE VALVE)

VALVE TRAY

VALVE TRAY

VALVE TRAY (CAGED VALVE)

VALVE TRAY (CAGED VALVE)

VALVE TRAY (FIXED VALVE)

VALVE TRAY