Experimental Study and Modeling of Mass Transfer in the Membrane Based Gas Absorption Process

摘要

A study on membrane based absorption process has been done in order to better characterize mass transfer as a function of various parameters, such as membrane characteristic features, the shell side hydrodynamics conditions and the type of absorption taking place. The impact of these parameters on mass transfer has been experimentally investigated, analyzed, modeled and explained in this thesis.This is a two-part study. Part 1 deals with transient CO2 absorption using a flat sheet membrane module where the influence of membrane porosity on mass transfer has been presented. It further clarifies the seemingly conflicting viewpoints from other previous investigators as to whether the whole membrane area or the total area of the pores should be used for membrane based absorption mass transfer calculations. The results have indicated that depending on the rate of absorption process, whether physical or chemical,effective mass transfer area may not be the whole membrane area and nor the total area of the pores but somewhere in between.The second part explores the effect of shell side hydrodynamic conditions on steady-state mass transfer in a hollow fiber membrane. A mathematical model has rigorously been generated to predict the improved SO2 absorption performance due to an increased number of inlet channels into the shell side at various liquid velocities. In this model, a hollow fiber module has been treated as a cascade of numerous discrete stirred tank reactor (STR) cells. The model predictions reasonably agree with the experimentally determined mass transfer coefficients. Minor deviations have been attributed to complex combinedeffects of multi-inlet channels and the liquid flow velocity, which were no texplicitly incorporated into the model.Tracer experiments were also done to further validate the model. RTD curves became narrower and more symmetrically regular as the number of inlet channels increased. This also showed that flow maldistribution due to channeling, backmixing, and 'dead zones' can further be eliminated at higher liquid flow velocity when the liquid stream is introduced into the shell side from three inlet channels.

目录

英文文摘

论文说明：Nomenclature

声明

CHAPTER 1: INTRODUCTION

1.1 Membrane technology

1.2 Mechanism of contacting phases

1.3 Membrane contactors, a viable alternative

1.4 Membrane separation compared to conventional contactors.

1.5 Advantages of membrane contactors

1.6 Some drawbacks of membrane contactors

1.7 Membrane gas absorption.

1.8 Mass transfer mechanism in membrane contactors

1.9 Resistance to mass transfer

1.10 Outline of this study

PART 1 CHAPTER 2: Effects of Membrane Porosity on Membrane Absorption Process

2.1 Problem statement

2.2 Conflicting points of views

2.3 Objective of this study

PART 1 Chapter 3: Theory

3.1 Calculation of k(ε)

3.2 Calculation of Φ(ε)

PART 1 CHAPTER 4: Experimental

4.1 Membrane geometric parameters

4.2 Procedure for the unsteady state CO2 absorption experiment using ePTFE flat membrane

PART 1 CHAPTER 5: Results and discussion

5.1 Experimental results

5.1.1 Physical Absorption Using Pure Water

5.1.2 Chemical Absorption Using 0.1 NaOH Aqueous solution

5.2 The model analysis of the Experimental results

5.2.1 The Actual membrane porosity is less than the efficacious porosity

5.2.2 The Actual membrane porosity is almost equal to the efficacious porosity

5.2.3 The actual membrane porosity is less than the efficacious porosity

5.3 Simulation by model

5.3.1 Calculation of the model parameter “1”

5.3.2 The simulation results by the model

5.3.3 Comparison of theoretical predictions with the experimental results

5.4 Conclusions

PART 2 CHAPTER 6: Mathematical model for mass transfer in a multi-inlet hollow fiber module

6.1 Introduction

6.2 Numerous shell side mass transfer correlations

6.3 Phase flow configuration

6.4 Shell side flow maldistribution

6.5 Objective of the study

PART 2 CHAPTER 7: Model Development

7.1 Continuous stirred tank reactor

7.2 Gas-liquid interface and calculation of SO2 Equilibrium Concentration in the liquid

7.3 Physical Absorption with Pure water

7.4 Chemical Absorption using NaOH Aqueous Solution

PART 2 CHAPTER 8: Experimental

8.1 SO2 Absorption

8.2 Experimental Residence Time Distribution (RTD)

PART 2 CHAPTER 9: Results

9.1 Experimental Results

9.2 Calculated results:

9.3 RTD Curves

PART 2 CHAPTER 10: Discussion and Conclusion

10.1 Model results compared with experimental mass transfer.

10.2 Analysis of RTD Curves

10.3 Conclusion

References

Appendix

Acknowledgements