Date of Award

11-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

First Advisor

Dr. Nayef Mohamed Ghasem

Second Advisor

Prof. Mamdouh Ghannam

Third Advisor

Dr. Yaser E. Greish

Abstract

Natural gas consists primarily of methane (CH4) but it also contains considerable amounts of contaminating compounds mainly carbon dioxide (CO2). The presence of CO2 reduces the heating value of the gas and due to its acidic character causes several operational problems. Hence the removal of CO2 from natural gas is crucially important. The focus of this research work is to investigate the potential for the energy efficient and effective separation of CO2/CH4 gas mixture via lean solvent and regenerating of the rich solvent through absorption/stripping mechanism taking place in a hollow fiber gas liquid membrane contactor process (GLMC) which combines the advantages of membrane technology with those of absorbent liquid. In a gas liquid membrane contactor the microporous membrane acts only as an interface between the gas and liquid phases. In this study primarily polyvinylidene fluoride (PVDF) hollow fiber membranes were fabricated via thermally induced phase separation (TIPS) method and the fabricated membranes were characterized using several membrane characterization techniques in order to optimize the membrane fabrication conditions. Then the membrane that had optimal performance was used in GLMC and absorption/stripping experiments were carried out in order to find the optimum operation window that gives higher absorption/stripping performance. Various absorbent liquids like different amino acid salts (AAS) and aqueous ammonia solutions were used as absorbent liquid other than conventional absorption liquids. To improve the stripping performance, enhanced CO2 desorption (based on pH-shift) was studied. Furthermore, a comprehensive mathematical model of GLMC was developed. viii The characterization studies revealed 28% PVDF membrane extruded at high temperature provides the optimum performance and addition of ethanol to the coagulation bath reduces the performance of the membrane. The absorption/stripping studies revealed module configurations and adopted operating parameters have great influence in absorption/stripping performance of GLMC. Further it has been identified AASs are potential absorption liquids in GLMC applications because it have lower potential of membrane wetting due to its high surface tension and good recyclability than the conventional absorption liquid while providing the same absorption performance. The absorption/stripping studies using aqueous ammonia revealed it can be used in GLMC applications. However the two main problems extensive membrane wetting and ammonia slip from the solution have to be overcome successfully. Enhanced CO2 desorption (based on pH-shift) studies revealed by reducing the CO2 rich solution pH the absorption liquid can be regenerated effectively. Finally the developed mathematical model well describes the GLMC process

Acknowledgments

First and foremost I would like to thank God, for giving me the power to believe in myself and lots of blessings to pursue my dreams. All the praises and thanks are to almighty Allah. Next, I would like to extend my acknowledgment and utmost appreciation to all those people who lend a hand to me directly or indirectly for completion of my PhD at UAEU. My heartfelt thanks and salutation go to UAEU for providing enormous resources and financial support to complete this thesis research work. I express my gratitude to Department of Chemical and Petroleum Engineering for providing me the graduate teaching assistantship during my PhD period at UAEU. It is immense pleasure to express my sincere and deep sense of gratitude to my supervisor and mentor, Dr. Nayef Mohamed Ghasem for his sustained enthusiasm, creative suggestions, motivation and exemplary guidance throughout the course of my doctoral research. I have been extremely lucky to have a supervisor who cared so much about my work, and who responded to my questions and queries so promptly. I solemnly submit my honest and humble thanks to him for bringing my dreams into reality. My heart is indebted to my co-supervisor, Prof. M.H. Al-Marzouqi. He gave me the freedom to use his research lab and the research assistantship provided by him enabled me to start my PhD in UAEU. My discussions with him and his insights always inspired and motivated me to get back on the right track. I deem it as my privilege to express my sincerest gratitude and heartfelt thankfulness to him for encouraging remarks throughout the course of this thesis research work. xi Further I would like to thank all the past and present membrane of UAEU community who provided me technical assistance and various other supports during the past few years of my life in UAE. Particularly I would like to express thanks to my friend Zahoor Ismail, she helped me lot to be familiar with UAEU and experimental work related to my research topic. I know that this work could not have been completed without the tremendous support of my family. I want to pay tribute to parents, parents-in-law, brother, brothers-in-law, sister, sisters-in- law and their families. My gratitude to my parents is beyond measure – all through my life, they have always sacrificed to ensure that I had the best opportunities possible and they have constantly believed in me and encouraged me to dream big and to pursue those dreams. They not only have shown their unconditional love, fidelity, endurance on me but also on my daughter also, as I was blessed with my little daughter in my second year of PhD. My parents took most of my parental responsibilities and encouraged me to finish this research work successfully. I can barely find words to express all the wisdom, love and support given for me by my parents, for that I am dedicating this thesis work to my parents. Last, but never least, I must thank my unbelievably supportive husband Ashar and our daughter Fathima Zahraa. I want to thank my husband for his endless understanding, patience and unconditional support he extended throughout my academic endeavors over the past several years and to pursuit my academic career to this level. The last word goes for my baby girl Zahraa, who has been the light of my life for the last two years and her pretty innocent face and cute smile given me the extra strength and motivation to get things done. Many special thanks to my little daughter for her childhood patience and sacrifices.

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