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Fractionation Research, Inc.RESEARCH – KEY TO BETTER DESIGN
Hydraulics of Kettle-ReboileryCircuit on Distillation Columns
Tony Cai, Mike Resetarits, and Ahmad Shariat y , ,Fractionation Research, Inc.
Distillation Honors Session: Professor Michael Schultes 2010 AIChE Annual Meeting, Salt Lake City, UT
November 9, 2010
Slide 2
Dr. Schultes at FRI Experimental Unit in 1998
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Slide 3
Dr. Schultes at FRI Experimental Unit in 2010
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Slide 4
Dr. Schultes at FRI Experimental Unit in 2010
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Slide 5
Captain Dr. Schultes
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Fractionation Research, Inc.RESEARCH – KEY TO BETTER DESIGN
Hydraulics of Kettle-ReboileryCircuit on Distillation Columns
Tony Cai, Mike Resetarits, and Ahmad Shariat y , ,Fractionation Research, Inc.
Distillation Honors Session: Professor Michael Schultes 2010 AIChE Annual Meeting, Salt Lake City, UT
November 9, 2010
Introduction 7
• Reboilers are commonly used heat exchangers on distillation columns, supplying most of the energy required for the columnrequired for the column
• It is very important to properly design and operate the overall reboiler circuito If too much heat is supplied, the tower will flood; too little
heat is available, separation performance decreases• Si ifi t b f f ti t bl b• Significant number of fractionator problems can be
attributed to either improper bottom circuit design or poor reboiler circuit layoutp y
• Reboiler problems are thought to be the second-most common cause of tower problems
AIChE Annual Meeting/Salt Lake City/November/2010 Reboiler Circuit
Typical Kettle Reboiler Circuit Slide 8
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Problems & Objectives 9
• Tower bottom hydraulics is not generally investigated as mush much as mass transfer is
• This paper focus on the hydraulics of kettle reboiler circuits
• Experimental results are compared to analytical predictionspredictions
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Approaches 10
• Pressure drops of vapor phase between the reboiler and the column were measured using differential pressure transmitter
• The liquid level at the bottom of the column was qmeasured using a bubbler
• Pressure drops of liquid and vapor phases acrossPressure drops of liquid and vapor phases across the reboiler circuit were calculated/estimated using basic fundamental fluid dynamicsusing basic fundamental fluid dynamics
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
FRI Experimental Unit Slide 11
HP ReboilerLP
Reboiler
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Kettle Reboiler Circuit Slide 12
Return Line
Reboiler
Line
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Locations of Pressure Drop Measurements 13
DP Line
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Location of Bubbler 14
DP Line
Bubbler Line
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Pressure Transmitter 15
DP Transmitter
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Results Slide 16
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Standard Kettle Reboiler Circuit Slide 17
PVapor
PLiquid
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Slide 18
Reboiler Pressure Drop (Vapor Phase) iC /nC 165 psia (11 4 bar)
5.0
Capacity Factor CS, m/s
iC4/nC4 165 psia (11.4 bar)
3.5
4.0
4.5
O
2.0
2.5
3.0
inch
H2O
0.5
1.0
1.5
0.00.00 0.05 0.10 0.15 0.20 0.25 0.30
Capacity Factor CS, ft/s
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Measured Reboiler DP
Slide 19
Reboiler Pressure Drop (Vapor Phase) iC /nC 165 psia (11 4 bar)
4 5
5.0
iC4/nC4 165 psia (11.4 bar)
3 0
3.5
4.0
4.5
O
1 5
2.0
2.5
3.0
inch
H2O
0.5
1.0
1.5
0.00.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00
Return Line Velocity, ft/s
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Measured Reboiler DP
Slide 20
Reboiler Pressure Drop (Vapor Phase) iC /nC 165 psia (11 4 bar)
4.5
5.0
iC4/nC4 165 psia (11.4 bar)
3 0
3.5
4.0
O
2.0
2.5
3.0
inch
H2O
0.5
1.0
1.5
0.00.00 0.05 0.10 0.15 0.20 0.25 0.30
Capacity Factor CS, ft/s
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Measured Reboiler DP Calculated Reboiler DP
Slide 21
Reboiler Pressure Drop (Vapor Phase) iC /nC 165 psia (11 4 bar)
4.5
5.0
iC4/nC4 165 psia (11.4 bar)
3.5
4.0
O
2.0
2.5
3.0
inch
H2O
0 5
1.0
1.5
0.0
0.5
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00
Return Line Velocity, ft/s
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
y,
Measured Reboiler DP Calculated Reboiler DP
Slide 22
Column Bottom Liquid LevelsiC /nC 165 psia (11 4 bar)
30.0
iC4/nC4 165 psia (11.4 bar)
20.0
25.0
id
10 0
15.0
h H
ot L
iqui
5.0
10.0
inch
0.00.00 0.05 0.10 0.15 0.20 0.25 0.30
Capacity Factor CS, ft/s
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Measured Column Bottom Level
Slide 23
Column Bottom Liquid LevelsiC /nC 165 psia (11 4 bar)
30.0
iC4/nC4 165 psia (11.4 bar)
20.0
25.0
id
10 0
15.0
h H
ot L
iqui
5.0
10.0
inch
0.00.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00
Return Line Velocity, ft/s
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Measured Column Bottom Level
Slide 24
Rise of Column Bottom Liquid LeveliC /nC 165 psia (11 4 bar)
12.0
iC4/nC4 165 psia (11.4 bar)
8.0
10.0
id
4.0
6.0
ch H
ot li
qui
0 0
2.0
inc
0.00.00 0.05 0.10 0.15 0.20 0.25 0.30
Capacity Factor CS, ft/s
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Rise of Column Bottom Level
Slide 25
Rise of Column Bottom Liquid LeveliC /nC 165 psia (11 4 bar)
12.0
iC4/nC4 165 psia (11.4 bar)
8.0
10.0
id
4.0
6.0
ch H
ot li
qui
0 0
2.0
inc
0.00.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00
Return Line Velocity, ft/s
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Rise of Column Bottom Level
Slide 26
Rise of Liquid Level and Reboiler Pressure Drop iC / C 165 i (11 4 b )
12.0
iC4/nC4 165 psia (11.4 bar)
8.0
10.0
id
4.0
6.0
ch H
ot li
qui
0.0
2.0
inc
0.00.00 0.05 0.10 0.15 0.20 0.25 0.30
Capacity Factor CS, ft/s
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Measured Reboiler DP Rise of Column Bottom Level
Slide 27
Rise of Liquid Level and Reboiler Pressure Drop iC / C 165 i (11 4 b )
12.0
iC4/nC4 165 psia (11.4 bar)
8.0
10.0
id
4.0
6.0
ch H
ot li
qui
0.0
2.0
inc
0.00.00 0.05 0.10 0.15 0.20 0.25 0.30
Capacity Factor CS, ft/s
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Measured Reboiler DP Rise of Column Bottom Level Caculated Total Pressure Drops
Slide 28
Reboiler Pressure Drop (Vapor Phase)
25.0C6/C7 5 psia (1.65 bar)
15.0
20.0
in H
2O
10.0
15.0
ssur
e D
rop,
5.0
Pres
0.00.00 0.10 0.20 0.30 0.40 0.50 0.60
Capacity Factor Cs, ft/s
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Calculated Measured
Slide 29
Reboiler Pressure Drops (Vapor Phase)
25.0
C6/C7 5 psia (1.65 bar)
15.0
20.0
in H
2O
10.0
ssur
e D
rop,
0 0
5.0Pres
0.00.00 0.10 0.20 0.30 0.40 0.50 0.60
Capacity Factor Cs, ft/s
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Calculated Measured Calculated (with estimated entrainment)
Conclusions 30
• Pressure drops across the reboiler circuit and liquid levels can be measured and monitored using diff ti l t ittdifferential pressure transmitters
• Measured pressure drops and liquid levels agree bl ll ith th l l t d/ ti t dreasonably well with the calculated/estimated
values P d f li id h b i ifi t• Pressure drop of liquid phase can be significant portion of total pressure drops, which needs to be considered and included in the reboiler circuitconsidered and included in the reboiler circuit designs
••Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
Acknowledgements 31
• Authors would like to extend their great appreciations to:o FRI memberships for their continuous support to FRI
research programso Professor Michael Schultes for his excellent work
and guidance to FRI research program as FRI h i l C i bTechnical Committee member
o Professor Olujic and Mr. Urbanski for their great k thi iwork on this session
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
32
Reboiler CircuitAIChE Annual Meeting/Salt Lake City/November/2010
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