Sulzer Chemtech

Efficiency Benefits of High Performance

Structured Packings

Kevin Bennett, Sulzer Chemtech

Mark Pilling, Sulzer Chemtech

Prepared for Presentation at

Department of Energy
Texas Technology Showcase 2003
Separation & Distillation Technology Session
Introduction Sulzer Chemtech

• Structured Packing is the Internal of

Choice for Low Pressure and Low
Liquid Rate Systems

• High Capacity

• High Efficiency

• Low Pressure Drop

• Proper Distribution is Critical

Mechanical Construction Sulzer Chemtech

• Thin Sheet Metal

• Angled Corrugation

• Textured & Perforated

• Layers are Segmented

& Rotated
Mechanical Construction - Base Material Sulzer Chemtech

• Sheet Metal Typically 0.004” - 0.008”

– Larger Crimp Packings May Require
More Thickness
– Essentially No Corrosion Allowance
• Material Selection is Critical

• Gauze Packings Made From Woven

Metal Cloth
– Usually for Very High Efficiency
Applications
Mechanical Construction - Surface Treatment Sulzer Chemtech

• Typically Textured & Perforated

– Texturing Promotes Spreading of Liquid

on Surface

– Perforation Allows Equalization of Flows

and Pressures Between Sheets

– Lack of Texture and/or Perforation

Reduces Efficiency
 Mechanical Construction - Corrugation Angle Sulzer Chemtech

• Most Commonly 45o

(Sulzer Y Designation)

– Usually the Optimum Angle for

Efficiency, Capacity & Cost

• Second Most Commonly 60o

(Sulzer X Designation)

– More Often Used in Absorption

& Heat Transfer Applications
Where Surface Area is More
Important
Mechanical Construction - Surface Area Sulzer Chemtech

• Typically Expressed in Units of m2/m3

– Normal Range (40 - 900 m2/m3)

– Benchmark M250.Y

– Lower Surface Area Packing (40 - 90 m2/m3)

Often Grid Type

• Heat Transfer & Scrubbing

– High Surface Area > 500 m2/m3

• Air Separation & Fine Chemicals

When To Use Structured Packing Sulzer Chemtech

• System Pressure & Liquid Rates

• Vessel Diameter

• Number of Stages

• Presence of Two Liquid Phases

• Thermal Degradation
System Pressure & Liquid Rates Sulzer Chemtech

• Structured Packing Works Has its

Greatest Advantage with Low Liquid
Rates and High Vapor Velocities

– In Distillation Systems, Low Pressure

Means Low Liquid Rates and High
Vapor Velocities. Ideal for Structured
Packing

– High Pressure Absorption with Low

Liquid Rates are also Good Structured
Packing Applications
Number of Stages Required Sulzer Chemtech

• Structured Packing’s High Efficiency

Makes it Ideal for Applications
Requiring Many Stages

– Exception: Superfractionators with High

Pressures and High Liquid Rates
Performance Characteristics - Efficiency Sulzer Chemtech

• Mainly a Function of:

– Packing Geometry

• Surface Area

• Crimp Angle

– Distribution Quality

– Process System Properties

Performance Characteristics - Efficiency Sulzer Chemtech

• Packing Geometry

– Surface Area: Efficiency Increases With

Surface Area

– Crimp Angle: Efficiency Increases with

Decreasing Crimp Angle
Performance Characteristics - Efficiency Sulzer Chemtech

• Things Requiring Special Consideration:

– High Liquid Rates

• Rates Above 20-25 gpm/ft2 May Have Lower

Efficiencies

– High Relative Volatility (α > 3)

– High Liquid Viscosity & High Stripping Factors

– Absorption & Stripping Applications

– High Surface Tension

• All These Systems Have Been Packed with Structured

Packing. Special Design Considerations are Needed
 Sulzer Chemtech

Performance Characteristics - Hydraulic

Loading

• Beyond the Loading Point, Liquid Holdup

in Conventional Structured Packing
Begins at the Interface Between Layers
 Sulzer Chemtech

1. MellapakPlus: Background, Performances & Potential

Development steps

! Concept: modify transition

between the packing layers

! CFD Analysis

! Mechanical issues
 Sulzer Chemtech

Product

Mellapak® MellapakPlus®
 Sulzer Chemtech

Close Up Mellapak 252.Y

 Sulzer Chemtech

Sulzer Chemtech Testing

• Facility: Winterthur, Switzerland

• Column Diameter: 3.3 ft (1 m)
• Bed Depth: 9.9 ft (3.03 m)
• Distributor Type: Sulzer Chemtech VKG
• Test System: Chloro/Ethyl Benzene at
75mm Hg (100 mbar)
 Sulzer Chemtech

FRI Testing

• F.R.I. 2000 Category 1 Packing Test

• Industrial Scale Test Facility

• Measure efficiency, capacity, pressure

drop, holdup
 Sulzer Chemtech

FRI Testing

• Facility Stillwater, OK
• Column Diameter: 4 ft (1.2 m)
• Bed Depth: 12 ft (3.7 m)
• Distributor Type: Sulzer Chemtech VKG
• Test Systems: Ortho/Para-Xylene at
100mm Hg (133 mbar)
C6/C7 at 5 & 24 psia
(345 & 1650 mbar)
Sulzer Chemtech
 Sulzer Chemtech
Figure 3. Mellapak Plus 252.Y Efficiency
o/p Xylene System, 100 mm Hg (FRI)
&
Chloro/Ethyl Benzene, 77 mm Hg (Sulzer CT)
Capacity Factor Cs, m/s
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18
32 0.80

30 0.75
M252Y (FRI) M250Y (FRI)
28 Optiflow (FRI) M250Y (WT) 0.70
M252Y (WT)
26 0.65

24 0.60
HETP, inches

HETP, m
22 0.55

20 0.50

18 0.45

16 0.40

14 0.35

12 0.30

10 0.25
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60
Capacity Factor Cs, ft/s
 Sulzer Chemtech

Figure 4. Mellapak Plus 252.Y Efficiency

12 foot (3.67 m) Bed Depth
C6/C7 System, 5 psia (0.34 bar)

Capacity Factor Cs, m/s

0.00 0.02 0.04 0.06 0.08 0.10 0.12
32 0.80
M252.Y VKG 5.3 mm (Midbed 16-38%C6)
30 M252.Y VKG 5.3 mm (Midbed 45-52%C6) 0.75
M252.Y VKG 5.3 mm (Midbed 83-91%C6)
28 M250.Y 1988 TDP (midbed 40-66%C6) 0.70
M250.Y 1988 TDP (midbed 90-96%C6)
26 0.65

24
HETP, inches

0.60

HETP, m
22 0.55

20 0.50

18 0.45

16 0.40

14 0.35

12 0.30

10 0.25
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
Capacity Factor Cs, ft/s
 Sulzer Chemtech

Figure 5. Mellapak Plus 252.Y Efficiency

12 foot (3.67 m) Bed Depth
C6/C7 System, 24 psia (1.65 bar)

Capacity Factor Cs, m/s

0.00 0.02 0.04 0.06 0.08 0.10 0.12
32 0.80

30 M252.Y VKG 6.7 mm (Midbed 34-58%C6) 0.75

M250.Y 1988 TDP (midbed 44-53%C6)
28 0.70
M250.Y 1988 TDP (midbed 61-79%C6)
26 M250.Y 1988 TDP (dc-reflux)
0.65

24
HETP, inches

0.60

HETP, m
22 0.55

20 0.50

18 0.45

16 0.40

14 0.35

12 0.30

10 0.25
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
Capacity Factor Cs, ft/s
 Sulzer Chemtech

Figure 6. Mellapak Plus 252.Y Efficiency

Effect of Pressure on HETP

Capacity Factor Cs, m/s

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18
32 0.80

30 0.75
100 mm Hg xylene
28 5 psia (0.34 bar) C6/C7 0.70
24 psia (1.65 bar) C6/C7
26 0.65
75 mm Hg CB/EB
24
HETP, inches

0.60

HETP, m
22 0.55

20 0.50

18 0.45

16 0.40

14 0.35

12 0.30

10 0.25
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60
Capacity Factor Cs, ft/s
 Sulzer Chemtech

Efficiency Conclusions
• M252.Y HETP 14 -16 inches (0.35-0.4 m) as good
or better than M250.Y & Optiflow
• Maximum useful capacity 100 mm Hg: 40% above
M250.Y, 15% above Optiflow
• Maximum useful capacity 5 psia (0.34 bar): 25%
above M250.Y
• Maximum useful capacity 24 psia (1.65 bar): 18%
above M250.Y
 Sulzer Chemtech

Figure 7. Mellapak Plus 252.Y Pressure Drop

12 foot (3.67 m) Bed Depth
o/p Xylene System, 100 mm Hg
Total Reflux

10.000
M252.Y
M250.Y 1988 TDP
Optiflow VEP
Sulpak
Pressure Drop, in H2O/ft

1.000

0.100

in H2O/ft x 8.167 =
mbar/m

0.010
0.01 0.10 1.00
Capacity Factor Cs, ft/s
 Sulzer Chemtech

Figure 8. Mellapak Plus 252.Y Pressure Drop

12 foot (3.67 m) Bed Depth
C6/C7 System, 24 psia (1.65 bar)
Total Reflux

10.000
Top
Bottom
Overall-Measured
Overall-Calculated
Sulpak
1.000 M250.Y 1988 TDP
Pressure Drop, in H2O/ft

0.100

0.010

in H2O/ft x 8.167 =
mbar/m

0.001
0.01 0.10 1.00
Capacity Factor Cs, ft/s
 Sulzer Chemtech

Figure 9. Mellapak Plus 252.Y Pressure Drop/Stage

12 foot (3.67 m) Bed Depth
o/p Xylene System, 100 mm Hg
Total Reflux

100.000

M252.Y

M250.Y 1988 TDP

Optiflow VEP
10.000
Inch H2O/stage

1.000

0.100

in H2O/stage x 2.5 = mbar/stage

ft/s x 0.3048 = m/s

0.010
0.01 0.10 1.00
Capacity Factor Cs, ft/s
 Sulzer Chemtech

Pressure Drop Conclusions

• M252.Y pressure drop less than M250.Y

• Good agreement with Sulpak predictions

• Lowest pressure drop per stage

measured in 100 mm Hg xylene at F.R.I.
 Sulzer Chemtech

Other MellapakPlus Data

separation efficiency separation efficiency

0.5 0.4

0.4
0.3

HETP [m]
HETP [m]

0.3
0.2
0.2
0.1
0.1

0 0
0 1 2 3 4 0 1 2 3
0.5 0.5
gas load F-factor [Pa ] gas load F-factor [Pa ]

pressure drop pressure drop

10 10

∆p [mbar/m]
∆p [mbar/m]

1 1

MellapakPlus 752.Y MellapakPlus 752.Y

Mellapak 750.Y Mellapak 750.Y

Mellapak 500.Y Mellapak 500.Y

0.1 0.1
0 1 2 3 4 0 1 2 3
0.5 0.5
gas load F-factor [Pa ] gas load F-factor [Pa ]

100 mbar 960 mbar