1. Packed Column Experiment
Chris Ford
University of Kentucky
Department of Chemical Engineering

2. Packed Column Experiment Packed Column Design Project
Overview
Packed Column Experiment
Introduction
Objectives
Theory
Equipment and Materials
Laboratory Procedures
Data Analysis Methods
Data Collected
Results and Discussion
Packed Column Design Project
Introduction
Methods
Results
Conclusion

3. Introduction Packed Column Function Applications of Packed Columns
Increase Contact Surface Area
Increase Contact Time
Applications of Packed Columns
Chemical Reaction
Physical Separation
Design of Packed Column
Structured vs. Dumped Packing
Packing Type, Material
Gas Flow Rate vs. Liquid Flow Rate
Loading, Channeling Considerations
Figure 1: Packed Column DN400 at Montz-Pac Type B1-250 Installation

4. Experimental Objectives
Overall Objective
Measure the pressure drop across a foot of packing as a function of vapor and liquid flow rates for three kinds of packing: plastic Pall rings, ceramic Intalox saddles, and ceramic Raschig rings
Specific Objectives
Measure pressure drop across a foot of packing for each packing type using dry air only and varying the flow rate. Record at least 3 trials for one packing type for error analysis. Compare to theoretical values.
Measure pressure drop across a foot of packing for each packing type using a water-air two phase system and varying both gas and liquid flow rates. Compare to theoretical values.

5. Theory Interfacial Contact Provides surface area for mass transfer
Geometry/size of packing (ring, saddle, etc…)
Composition of packing (metal, plastic, ceramic)
Slows interaction, increases interface time
Liquid flow rate
Gas/vapor flow rate
HETP
Result: significant pressure drop per column height
Figure 2: Interfacial contact in a binary system.

6. Modeling Pressure Drop in a Packed Bed
Theory
Modeling Pressure Drop in a Packed Bed
Dry Packed Bed Model: Ergun Equation
ΔP/Z = pressure drop per column height, G’ = superficial gas mass velocity, ρg = gas density, gc = gravitational constant, dp = effective packing particle diameter, and  = fractional void volume
Wet Packed Bed Model: Leva Equation
ΔP/Z = pressure drop per column height, G’ = superficial gas mass velocity, L’ = superficial liquid mass velocity, ρg = gas density, and  and  = packing constants specific to the packing material

7. Operational Influences on Packed Columns
Theory
Operational Influences on Packed Columns
Loading
Liquid buildup in void spaces
Reduces interfacial contacting surface
Flooding
Entrainment of liquid
Liquid surface continuous across top of packing
Disturbance of packing
Figure 3: A log-log plot of pressure drop per unit height of packing vs. superficial gas velocity for Fleximax® 400 packing material

8. Equipment and Materials
List of Components
Columns: C1-C3
5’ tall, Inner diameter of 6.5’
C1 Packing = 5/8” plastic Pall rings
C2 Packing = 1/2” ceramic Intalox saddles
C3 Packing = 1/2“ ceramic Raschig rings
Pressure Transducers: PT1-PT6
Solenoid Valves: SV1 (C1-C3) & SV2 (C1-C3)
Control vapor inflow (SV2) and outflow (SV1)
Ball Valves: V (C1-C3)
Control fluid outflow
Exit Valve: EV-3
Figure 4: Packed column apparatus schematic

9. Equipment and Materials
Open column to air
Transducer pressure readings (inches H2O)
Air flowmeter (SCFM), regulating valve
Water flowmeter (gal/min)
Water regulating valve
Water pump on/off
Tank level control
Figure 6: Computer display for packed column controls and data collection
Figure 5: Air and water flow meters, regulating valves

10. Equipment and Materials
Diagram 1: Various dumped packing materials.

11. Laboratory Procedures
Dry Column Data Collection
Collect transducer pressure data at a frequency of 10 hz for 3 minutes for a selected air flow rate. Repeat for 4 flow rates per column. Repeat for a second data set over each column (same flow rates). Acquire a third data set for one column for error analysis.
Wet Column Data Collection
Collect transducer pressure data at a frequency of 10 hz for 3 minutes for a selected air and water flow rate. Repeat for 3 air flow rates per water flow rate. Repeat for 2 water flow rates per column.

12. Data Analysis Procedures
Dry Column Data Analysis
Pressure data averaged at each transducer for each flow rate.
Drop between average transducer pressures calculated for each flow rate.
Pressure drops between transducers averaged to one pressure drop for each flow rate.
Average pressure drops per foot packing averaged between repeated data sets.
Ergun equation for pressure drop per unit height of packing provides theoretical values
Standard deviation calculated for pressure drop per foot packing in column 2 (three data sets)
Wet Column Data Analysis
Pressure data averaged at each transducer for each air/water flow rate.
Drop between average transducer pressures calculated for each air/water flow rate.
Pressure drops between transducers averaged to one pressure drop for each air/water flow rate.
Average pressure drops per foot packing averaged between repeated data sets.
Leva equation for pressure drop per unit height of packing provides theoretical values

13. Results and Discussion
Table 1: Summary of Dry Column Data
ΔP/Z = pressure drop per unit height of packing, G’ = superficial mass velocity of gas phase. Ergun calculations based on literature values of void fractions and effective particle diameters for each packing material and reference values for properties of air at 20°C.
Table 1.a: Packing Parameters
 = fractional void volume, dP = effective packing diameter

14. Results and Discussion
Dry Packed Column Data
Figure 7: Pressure drop per foot packing (ΔP/Z) as a function of gas flow rate for column 1 (Dry). Red squares indicate experimental data. Blue diamonds indicate Ergun calculations.
Figure 8: Pressure drop per foot packing (ΔP/Z) as a function of gas flow rate for column 2 (Dry). Red squares indicate experimental data. Blue diamonds indicate Ergun calculations.
Figure 9: Pressure drop per foot packing (ΔP/Z) as a function of gas flow rate for column 3 (Dry). Red squares indicate experimental data. Blue diamonds indicate Ergun calculations.

15. Results and Discussion
Table 2: Summary of Wet Packed Column 2 Data
Qgas, Qliquid = gas, liquid flow rate. G’, L’ = superficial mass gas and liquid flow rates, Pavg = average experimental pressure drop, ΔPLeva = calculated pressure drop using Leva equation. For Leva calculations, literature packing coefficients of  = 1.04 and  = 0.37 were used. All gas and liquid properties referenced at 20°C

16. Results and Discussion
Wet Packed Column 2 Data
Figure 10: Average pressure drop (ΔPavg) per foot packing vs gas flow rate for liquid flow rate of 2 gallons/min
Figure 11: Average pressure drop (ΔPavg) per foot packing vs gas flow rate for liquid flow rate of 3.5 gallons/min

17. Results and Discussion
Table 3: Summary of Wet Packed Column 3 Data
Qgas, Qliquid = gas, liquid flow rate. G’, L’ = superficial mass gas and liquid flow rates, Pavg = average experimental pressure drop, ΔPLeva = calculated pressure drop using Leva equation. For Leva calculations, literature packing coefficients of  = 3.1and  = 0.41 were used. All gas and liquid properties referenced at 20°C

18. Results and Discussion
Wet Packed Column 3 Data
Figure 12: Average pressure drop (ΔPavg) per foot packing vs gas flow rate for liquid flow rate of 2 gallons/min
Figure 13: Average pressure drop (ΔPavg) per foot packing vs gas flow rate for liquid flow rate of 3.5 gallons/min

19. Results and Discussion
Table 4: Summary of Wet Packed Column 1 Data
Qgas, Qliquid = gas, liquid flow rate. G’, L’ = superficial mass gas and liquid flow rates, Pavg = average experimental pressure drop, ΔPLeva = calculated pressure drop using Leva equation. For Leva calculations, literature packing coefficients were unavailable. Reduced sum of squared error approach yielded iterated values of  = 0.33 and  = All gas and liquid properties referenced at 20°C

20. Results and Discussion
Figure 14: Average pressure drop (ΔPavg) per foot packing vs gas flow rate for column 1 experimental data

21. Experiment Conclusions
For Wet Packed Columns…
Ceramic Intalox saddle packing offered the lowest pressure drops at highest liquid flow rates and lowest gas flow rates.
Higher liquid flow rates result in flooding at lower gas flow rates.
Ceramic Intalox saddle packing had the closest Leva equation correlation.
Plastic Pall rings had almost no correlation with Leva equation predictions
For Dry Packed Columns…
Plastic Pall ring packing offered strongest Ergun equation correlation.
Plastic Pall ring packing caused the lowest average pressure drop per foot of packing material.
Ceramic Raschig rings had almost no correlation with Ergun equation predictions
Future Suggestions
Experiment with other binary system components
Experiment with liquid-liquid systems

22. Design Project: Overview
Packed Columns as Mass Transfer Equipment
An air stream carrying mole fraction of ammonia is fed to each packed column used in the experiment with water as the counterflow.
Objective: Determine the separation potential of each column. Evaluate the best conditions for mass transfer to occur.
Diagram 2: Basic mass transfer contactor column

23. Design Project: Methods
Approach
AspenPlus® design software was used to model the mass transfer behavior in each column.
Assumptions
Both vapor and liquid streams were assumed to be at 20°C
Polar protic solvent (water), and polar solute (ammonia) required the ideal gas law equation for modeling vapor-liquid interaction with henry’s law components.
The cyclic nature of the building air supply was neglected.
Water flow rates of 2 and 4 gallon per minute were used based on the limitations of the equipment encountered in the experiment.

24. Design Project: Results
Table 5: Summary of Aspen® Modeling Results
Qgas, Qliquid = gas, liquid volumetric flow rate. Yellow cells indicate highest separation potential, red cells indicate flooding

25. Design Project: Results
Figure 15: Percent ammonia recovered vs gas flow rate for Column 1. Blue diamonds indicate liquid flow rate of 2 gal/min, red squares indicate 4 gal/min
Figure 16: Percent ammonia recovered vs gas flow rate for Column 2. Blue diamonds indicate liquid flow rate of 2 gal/min, red squares indicate 4 gal/min
Figure 17: Percent ammonia recovered vs gas flow rate for Column 3. Blue diamonds indicate liquid flow rate of 2 gal/min, red squares indicate 4 gal/min

26. Design Project: Conclusion
Packed Columns as Mass Transfer Equipment
All three columns and packing material demonstrated substantial separation ability for removing a water-soluble dilute species.
The ceramic Raschig® ring packing experienced significant flooding.
Optimal ammonia recovery occurred at higher liquid flow rate and lowest gas flow rate for both Intalox® and Pall ® packing.
Minimizing loading maximizes contact time, resulting in better performance.

27. References
Wankat, P.C. (2007). Separation Process Engineering (2nd). Prentice Hall; Massachusetts. Henley, E.J. & Seader, J.D. (2006). Separation Process Principles (2nd). John Wiley & Sons: New York University of Kentucky Department of Chemical Engineering. “Packed Column Experiment.” CME 433 (2011) department-editor.html honeycombs.com/ceramic/Ceramic_Raschig_Ring_Tower_Packing.htm Demister-Filters.html