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Absorption of Carbon Dioxide by a Sodium Hydroxide Solution in a Packed Tower

Presentation Overview. Requested informationProject objectivesPlanning and executionUnit operation backgroundExperimental designResults and conclusionsRecommendations . For what purpose?. Request from Environmental Systems Design They need to finalize their tower design givenWaste gas contains 3% CO20.05N NaOH scrubbing solution at 40 mL/sEmpirical analysis of mass transfer coefficients and effluent compositions of CO2Theoretical analysis for comparison.

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Absorption of Carbon Dioxide by a Sodium Hydroxide Solution in a Packed Tower

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    1. Absorption of Carbon Dioxide by a Sodium Hydroxide Solution in a Packed Tower Trevor Carlisle Thad Ivey Sara York ChE 414 Winter 2005

    2. Presentation Overview Requested information Project objectives Planning and execution Unit operation background Experimental design Results and conclusions Recommendations

    3. For what purpose? Request from Environmental Systems Design They need to finalize their tower design given Waste gas contains 3% CO2 0.05N NaOH scrubbing solution at 40 mL/s Empirical analysis of mass transfer coefficients and effluent compositions of CO2 Theoretical analysis for comparison

    4. Objectives Verify calibration data Find the dependence of KGa and outlet compositions on gas flow Determine flooding points Theoretically calculate KGa Statistically analyze the data

    5. Action Items Understand unit operation Identify safety issues Calibrate flow meters DOE and gas sampling Organize and evaluate the data Identify appropriate mass transfer relations Calculate empirical results Compare with theoretical predictions Reach conclusions and present results

    6. Team member roles Sara- Operations Manager Run the GC Ensure Proper tower operation Responsible for data management Thad- Safety Manager Identify safety issues Develop the safety plan Monitor safe lab behavior Trevor- Team Leader Develop and the project plan Ensure lab work moves forward Coordinate group tasks

    7. Lessons Learned Do not rush experimental design Emphasize background information prior to lab work Do not leave any ambiguity in action items Perform theoretical calculations prior to experimentation

    8. The Gas Absorption Tower Add picture of TowerAdd picture of Tower

    10. Mass Transfer with Reaction Mechanism: liquid film controlling Fix mass transfer diagramFix mass transfer diagram

    11. The rapid, 2nd order irreversible reaction

    13. Theoretical calculation of KGa with the Onda Correlation

    14. Theoretical Kga continued . . .

    15. Experimental Design Prepare ~0.05N NaOH solution Standardize scrubbing solution Vary gas flowrate (100 – 1000 mL/s) Maintain 3% CO2 Constant liquid flow, 40 mL/s Add Picture of GC and needleAdd Picture of GC and needle

    16. More on experimental design Allow time to reach SS mass transfer Gas samples taken from top and bottom of tower GC used for analysis Peak areas used to determine CO2 composition Four samples taken per flow setting Add Picture of Gas ChromatographerAdd Picture of Gas Chromatographer

    17. Results: Flooding Theoretical calculation Superficial Gas flow rate at flooding =525 lbm/ft2-hr =6016 lbm/hr with our tower Add flooding correlationAdd flooding correlation

    18. Results

    19. Results

    20. Results

    21. What accounts for theoretical and empirical differences? kL is affected by the 2nd order reaction Rather, kL = c*kLo, where c is a reaction parameter and kLo is the transfer coefficient without reaction Wetted surface area, aW, may be decreasing with increased gas flow The set up is not completely liquid film controlling

    22. What accounts for theoretical and empirical differences?

    23. Conclusions Theoretical model needs to be re-evaluated by considering reaction effects The gas phase resistance is not negligible: KGa= -.0042G + .66 (lbmol/ft3-hr-atm) CO2 composition in liquid outlet is zero based on mass balance CO2 composition in the gas outlet varies as a natural log: %CO2= 1.6ln(G) – 5.2 Predictions of yCO2 in tower outlet are not reliable above flows of 150 ft3/hr Flooding will occur well above reasonable operating flows Gf= 6016 (lbm/hr) = 6.19x105 (mL/s)

    24. Recommendations Obtain more data closer to flooding Determine the relation between reaction kinetics and KGa Use previous experiments contained in journals to anticipate results and complications Include theoretical calculations as part of the lab work

    25. References Perry, Robert H. and Green, Don W. 1997. Perry’s chemical engineer’s handbook (7th Ed). United States of America: R.R. Donnelly and Sons Company. Nijsing, R.A.O.T., Hendriksz, R.H, and Kramers, H. 1959. Absorption of CO2 in jets and falling films of electrolyte solutions, with and without chemical reaction. Chemical engineering science, 10,88-103. Rorrer, Gregory L. 2004. Che 411 mass transfer operations lecture notes supplement. Corvallis, OR: Dept. of Chemical Engineering, Oregon State University. Spector, Norman and Dodge, Barnett F. (year?). Removal of carbon dioxide from atmospheric air. American institute of chemical engineers, (vol?), 827-848.

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