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Other ____ University Microfilms international ELECTROCHEMICAL OXIDATION OF CARBONACEOUS MATERIALS DISPERSED IN MOLTEN CARBONATE DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By David George Vutetakis, B.S.Ch.E., M.S. ***** The Ohio State University 1985 Dissertation Committee: Approved by D. R. Skidmore J. F. Davis Adviser L. S. Fan Department of Chemical Engineering Copyright by David George Vutetakis 1985 To My Parents n ACKNOWLEDGEMENTS First, I want to thank my adviser, Professor Duane Skidmore, for his supervision of the Ph.D. project, his contributions concerning the experimental work, and his helpful suggestions in preparing this dissertation. Professor Robert Rapp is thanked for giving technical guidance in the area of high temperature molten salt electrochemistry. Dr. Harlan Byker, formerly of Battelle Memorial Institute, deserves credit for his effort in getting the Ph.D. project underway. Appreciation is given to Bob Canegali for helping with construction of the experimental apparatus, to Mike Kukla for assisting with equipment problems, and to Joe Baling for supplying alumina crucibles and other refractory items. Bud Farrar, Professor Karlis Svanks, and Professor Ron Tettenhorst are thanked for performing analytical measurements. The dissertation was typed by Pat Osborn, and her hard work is grate­ fully acknowledged. Financial assistance was graciously provided by the Department of Chemical Engineering, the Graduate School, Dupont, and Battelle Memorial Institute, and their support is gratefully acknowledged. I am deeply indebted to my wife, Liz, and our children for their patience and love, which counted more than words can say. Most of all I would like to thank the Lord God, who gave the motivation to accomplish what was set before me. i i i VITA August 10, 1957 ................... Born in Canton, Ohio 1975... ................................. Born of God through faith in Jesus Christ 1980 ................................. B.S.Ch.E., The Ohio State University, Columbus, Ohio 1981 ................................. M.S.Ch.E., The Ohio State University, Columbus, Ohio 1980-1984 ............................. Part-time Research at Battelle Memorial Institute, Columbus, Ohio 1981-1985 ............................. Ph.D. Candidate, Department of Chemical Engineering, The Ohio State University, Columbus, Ohio PUBLICATIONS D.O. Vutetakis, "Photoelectrolysis of Acetate Solutions Using Semiconductor Electrodes," M.S. Thesis, The Ohio State University, Columbus, Ohio (1981). IV FIELDS OF STUDY Major Field; Chemical Engineering Thermodynamics - Professor H. C. Hershey Heat Transfer - Professor T. L. Sweeney Mass Transfer - Professor C. J. Genakoplis Momentum Transfer - Professor R. S. Brodkey Chemical Kinetics - Professor E. R. Haering Unit Operations - Professor E. E. Smith Process Control - Professor R. D. Mohler Coal Processing - Professor D. R. Skidmore Minor Field: Corrosion and Electrochemistry Corrosion Engineering - Professors F.H. Beck and D. D. Macdonald Electrochemistry - Professor T. Kuwana TABLE OF CONTENTS PAGE ACKNOWLEDGMENTS......................................... H i VITA ...................................................... iv LIST OF T A B L E S ............................................. viii LIST OF F I G U R E S ........................................... x CHAPTER I. INTRODUCTION ................................... 1 CHAPTER II. LITERATURE REVIEW ............................. 3 2.1. Characteristics of Carbonaceous Materials .......... 3 2.2. Characteristics of Molten Alkali Carbonates .... 29 2.3. Previous Work Involving Electrochemical Oxidation of Carbonaceous Materials in Molten Electrolytes . 76 2.A. Related Literature................................... 96 CHAPTER III. EXPERIMENTAL METHODS ......................... 100 3.1. Objectives......................................... 100 3.2. Apparatus ......................................... 101 3.3. Feedstocks......................................... Ill 3.4. Procedures......................................... 114 CHAPTER IV. EXPERIMENTAL RESULTS ......................... 119 4.1. Overview of E x p e r i m e n t s ........................... 119 4.2. Open Circuit Potential D a t a ....................... 123 4.3. Current-Voltage Da t a ............................... 129 4.4. Gas Evolution D a t a ................................. 169 4.5. Surface Behavior of Gold A n o d e ..................... 172 CHAPTER V. DISCUSSION OF RESULTS ......................... 174 5.1. Thermodynamic Analysis of OCP D a t a ................. 174 5.2. Interpretation of I-V D a t a ......................... 180 5.3. Comparison of Data with Related Investigations . 190 5.4. Mechanism of Anodic Process ....................... 200 VI CHAPTER VI. CONCLUSIONS AND RECOMMENDATIONS .............. 210 6.1. Conclusions ....................................... 210 6.2. Recommendations................................... 216 CHAPTER VII. S U M M A R Y ..................................... 219 APPENDICES A. Analytical Data of Coal and Activated C a r b o n......... 221 B. Thermodynamimc Calculations .................... 227 BIBLIOGRAPHY ............................................. 231 v n LIST OF TABLES TABLE PAGE 1. Classification of Coals by R a n k ........................ 4 2. Analytical Data of Various American Coals .............. 12 3. Typical Limits of Ash Composition of U.S. Bituminous Coals ................................................. 13 1*. Comparison of Gasification Rates In C O ^ ................ 18 5. Alkali Carbonate Melting Points ........................ 31 6. Densities of Molten Alkali Carbonates .... .......... 33 7. Contact Angles of Ternary Carbonate Eutetlc with Various Materials at 4 0 0 ° C ............................. 3** 8. Viscosities of Molten Alkali Carbonates ................ 35 9. Electrical Conductivities of the Ternary Carbonate E u t e c t i c ............................................... 37 10. ûG^ of Selected Compounds............................... 46 11. Equilibrium Constants for Carbonate Dissociation .... 47 12. Experimental Equilibrium Constants of Carbonate Dissociation ........................................... 47 13. Summary of Fuel Cell Work Using Carbon Anodes In Molten Electrolytes ........................................... 78 14. Types of Working Electrodes ............................. 101 15. Types of Reference Electrode Sheaths .................. 103 16. Summary of Completed Experiments ...................... 120 17. OCP of Various Carbon Types at 700® C .................. 127 viii 18. Effect of Temperature History on OCP