SULFUR DIOXIDE REACTIONS WITH AQUEOUS SOLUTIONS OF MANGANESE AT HIGH TEMPERATURE AND WITH AMMONIA IN THE GAS PHASE A Thesis Presented to The Faculty of the Division of Graduate Studies and Research by Edwin M. Hartley, Jr. In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in The School of Chemical Engineering Georgia Institute of Technology September, 1973 SULFUR DIOXIDE REACTIONS ftlTH AQUEOUS SOLUTIONS OF MANGANESE AT HIGH TEMPERATURE AND WITH AMMONIA IN THE GAS PHASE Approved: > J * / Chairman 7 T z. Jk t /) . J *~ *' ' --? Date approved by Chairman; '*/''//£ ii Dedication To Barbara iii ACKNOWLEDGMENTS I am deeply indebted to my thesis advisor, Dr. Michael J. Matteson for his assistance with this endeavor. His expertise in the field, his constant activity in staying abreast of new developments and enquiring into innovative ideas and techniques have been a contin­ ual source of motivation. To Dr. G. L. Bridger, Director of the School of Chemical Engi­ neering, I am very grateful for his advice and assistance throughout my stay at Georgia Tech. His making available to me a part time instructorship is most appreciated as well as the other essential sources of assistance such as the Work Study Program, NSF Traineeship, Dow and DuPont Fellowships. The helpful and constructive critique of Reading Committee Member Dr. C. W. Gorton Is appreciated as well as his friendship during the past few years. The assistance received from Dr. Henry Neumann and Dr. W. T. Ziegler was essential to the completion of this work. Their liberal sharing of their time is acknowledged with gratitude as is the helpful comments of Dr. Joseph Smrekor. The Staff of the Price Gilbert Library were never too busy to provide help regardless of the time and effort required. To Jim Nabors many thanks for his technical competence and cooperation in maintaining the laboratory instrumentation and equipment and thanks also to Bob Shucker for his expert help with the Univac Computer, iv TABLE OF OONTENTS Page ACKNOWLEDGMENTS iii LIST OF TABLES vi LIST OF ILLUSTRATIONS vii SUMMARY ix Chapter I. INTRODUCTION 1 General Introduction Introduction to SO2 Reactions with Aqueous Solutions of Manganese Scope of this Work II. LITERATURE SURVEY 7 III. EXPERIMENTAL 14 Solubility of S02 in Dilute Sulfuric Acid IV. RESULTS AND DISCUSSION 28 Rate Constant Determinations Calculated vs. Experimental Results Humidity Effects V. CONCLUSIONS AND RECOMMENDATIONS 65 Conclusions Recommendations VI. INTRODUCTION TO SO REACTIONS WITH NH IN TOE GAS PHASE . 7 67 Scope of this Work VII. LITERATURE SURVEY 67 VIII. EXPERIMENTAL 77 V TABLE OF CONTENTS (Continued) Chapter Page IX. RESULTS AND DISCUSSION 88 X. CONCLUSIONS AND RECOMMENDATIONS 122 Conclusions Recommendations APPENDICES A. TEST DATA - SO REACTIONS WITH AQUEOUS SOLUTIONS OF MANGANESE 125 B. EQUILIBRIUM H S04 CONCENTRATION CALCULATION 131 C. SPECIFICATIONS OF GASES AND REAGENTS 135 D. EXPERIMENTAL EQUIPMENT DETAILS 136 E. PROCEDURE FOR NH - SO TEST AND SAMPLE CALCULATION . .. 138 F. SO -NH REACTION DETAILS 142 G. A MODEL CONSIDERED FOR THE REACTIONS OF SO + NH TO FORM AMMONIUM SULFATE . 153 H. ACCURACY OF RESULTS 159 BIBLIOGRAPHY 161 VITA 166 LIST OF TABLES e Page Slope-Intercept Data for k ' and K ' 35 Estimated Rate Constant k_ at Various Temperatures ... 37 Estimated Rate Constants k. and k ' at Various Temperatures 47 Calculated and Experimental Acid Concentration vs. Time for 1CC, 25°C and 38°C 49 Rate Constant Variations in Figure 15 54 Experimental Values of J and t Used in Figures 16, 17, and 18 56 Effect of Humidity on SO Absorption at 25°C 58 Initial Reactant Concentrations, NH -SO Reactions ... 88 Summary of X-Ray Diffraction Analysis 94 Series G-K Reactants and Products 100 Sulfur Dioxide - Ammonia Reaction Parameters 105 SO -NH Reaction Details 142 Slope Intercept Data for k ' and K 156 LIST OF ILLUSTRATIONS Figure Page 1. Experimental Apparatus for Kinetic Studies of SO Oxidation by Mn** Catalysis 16 2. SO Concentration in Reactor Off-gas, PPM 21 3. Solubility of SO Gas in Sulfuric Acid Solution at Various Temperatures . 26 4. Sulfuric Acid Concentration vs. Time For Various Temperatures 29 5. Sulfuric Acid Formation Rate vs. Time for Various Temperatures 30 6. HjSC^ Concentration vs. Time at 1°C, 25°C, and 38°C for Extended Periods of Time . 32 7. Inverse Initial Reaction Rate vs. Inverse Initial SO Concentration for Determination of Rate Constants k ' and K ' at 25°C 38 6 s 8. Log k/ vs. (r'K)"1 39 o 1 9. Log k? vs. (T^K)" 40 1 10. Log kx vs. (T^K)" 45 1 11. Log k2' vs. (T^K)" 46 12. Sulfuric Acid Concentration vs. Time, 38°C 51 13. Sulfuric Acid Concentration vs. Time, 25°C 52 14. Sulfuric Acid Concentration vs. Time, 1°C 53 15. Sulfuric Acid Concentration vs. Time at 25°C with Rate Constant Variations 55 16. (Sulfuric Acid Cone.)2 vs. Time for 1°C 60 17. (Sulfuric Acid Cone.)2 vs. Time, 25°C 61 LIST OF ILLUSTRATIONS (Continued) Figure Pige 18. (Sulfuric Acid Cone.)2 vs. Time for 38°C 62 19. Log K' vs. (T^K)"1 63 20. Effect of Gas Stream Humidity on SO Absorption at 25°C . 64 21. Flow Reactor for NH -SO Reactions 81 22. Experimental Apparatus for SO -NH Reactions .... 85 23. Integral Analysis of NH3-S02 Reaction 96 24. Series A Reactions - Prod. Cone. vs. Time Ill 25. Series B Reactions - Prod. Cone. vs. Time 112 26. Series C Reactions - Prod. Cone. vs. Time 113 27. Series D Reactions - Prod. Cone. vs. Time 114 2b. Series E Reactions - Prod. Cone. vs. Time 115 29. Series F. Reactions - Prod. Cone. vs. Time 116 30. Series G Reactions - Prod. Cone. vs. Time 117 31. Series H Reactions - Prod. Cone. vs. Time 118 32. Series I Reactions - Prod. Cone. vs. Time 119 33. Series J Reactions - Prod. Cone. vs. Time 120 34. Series K Reactions - Prod. Cone. vs. Time 121 35. Slope Intercept Data for k' and K 157 IX SUMMARY The kinetics of the reaction of SO in the aqueous phase forming sulfuric acid by manganous ion catalysis was investigated experimentally by dispersing a constant flow of air - SO gas mixture into a continu­ ous phase of water and dissolved manganese sulfate. Experimental tests were made with an SO gas concentration in the range of 3000 - 5000 PPM, .001 and .003 molar MnSO , and a temperature range from 1° to 65°C. A semi-empirical rate equation describing the reaction is given which rep­ resents the experimental results within the estimated 10% accuracy of the experimental data. The rate decrease observed with increasing sul­ furic acid concentration was found not to be caused primarily by the decrease in SO solubility as had been reported by others. A minor but observable decrease in initial absorption rate was found when the humidity of the gas stream was reduced from saturated air to dry air. The heterogeneous reaction of SO and NH gases in humid air at 23°C to form solid reaction products was studied experimentally. Results were similar to those reported by others on the reaction of anhydrous SO and NH gases to form solids in that a variety of products are formed depending on the concentrations of the reactants. With a large excess of HO vapor and 0 , e.g., air at 50% R.H., SO and NH gases in the ini­ tial concentration range of 4 to 60 millimoles per cu. meter and in th§ mole ratio of ^ |:|::[NH ]i[SO ] react to form crystalline ammonium sul­ fate. At equimolar concentration, a few percent of ammonium sulfamate is also formed. The reaction appears to be first order with respect to X both SO and NH and being irreversible, goes to completion. A differ­ ential rate equation and its integrated form are given which describes the experimental data within the estimated 1% accuracy of the experi- mental data. At lower concentrations of HO (trace to 31 mM-m ) the principle products are assumed to be NH *S0 and (NH ) «S0 with minor amounts of NH SO , (NH4) S 0?, NH4N , and N H?S04, Product identification of solid reaction products was by X-ray diffraction. At a lower con- _o centratio n of 0„ (16 mM-m ) the reaction product was primarily (NH ) 'SO^ wit h secondary products of N H SO and NH SO . The aerodynamic diameter of-particles produced from NH and SO gases in air containing a trace, 3-5 PPM water vapor, ranges from 1.2 ym to 2\im with a mean of 1.5 ^m. 1 CHAPTER I INTRODUCTION General Introduction This research consisted of a study of the kinetics of two types of reactions of sulfur dioxide. The first reaction, which is covered in the first part of this thesis, is the oxidation of SO to sulfuric acid in an aqueous solution of manganese sulfate. The second reaction type, which is covered in the second part, is the formation of solid reaction products from NH gas combining with SO gas in the presence of 0- gas and HO vapor in air. Both reactions are applicable to the general areas of the consequences of SO gas emissions to the atmosphere, control of those emissions, and recovery of sulfur as its compounds. These reactions can and do occur both in concentrated stack gases and in the atmosphere removed from the SO emitting sources where concentra­ tions are lower. The products of SO reactions (sulfates, sulfuric acid) compared to SO gas are usually many fold more toxic to plant, animal 45 and human life and more corrosive. In addition to the interest in the reactions which occur spontaneously, there is application to planned reactions in order to convert SO gas to its more easily handled compounds for recovery and control.