Non-Catalytic Steam Hydrolysis of Fats and Oils by Richard Charles
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Non-catalytic steam hydrolysis of fats and oils by Richard Charles Archuleta A thesis submitted in partial fulfillment of the requirement's for the degree of Master of Science in Chemical Engineering Montana State University © Copyright by Richard Charles Archuleta (1991) Abstract: The hydrolysis of fats or oils with water produces fatty acids and glycerol. Currently, the countercurrent, continuous, high pressure, high temperature, liquid phase Colgate-Emery process, which uses a catalyst to promote the reaction, is the state-of-the-art method of fat hydrolysis. Non-catalytic steam hydrolysis is a possible alternative. Significant degrees of hydrolysis may be achieved by continuously sparging superheated steam through high temperature fat at atmospheric pressure. A "bench-scale" hydrolyzer was designed and constructed to investigate the feasibility of steam hydrolysis and was tested with soybean oil and beef tallow. Each of the five stages in the 316 Stainless Steel, 1.77 inch inside diameter, 18-3/4 feet high hydrolyzer included a riser, a downcomer, and a steam dispersion plate similar to a distillation column. Investigations of the degree of hydrolysis were conducted at various temperatures and fat/steam feed ratios. The compositions of the overhead and bottoms products as well as stage liquid samples were analyzed. Soybean oil was not a good feed source because its highly unsaturated fatty acids polymerized at high temperatures. The degrees of hydrolysis achieved using tallow were 15% at 280°C and 35% at 300°C at a tallow-to-steam feed ratio of 4.2. At a feed ratio of 9.2, the degree of hydrolysis was 21% at 300°C. Decomposition of glycerol was strongly evident at 325°C but not at lower temperatures. Over 95% fatty acids were present in the readily separated organic portion of the overhead product. NON-CATALYTIC STEAM HYDROLYSIS OF FATS AND OILS by Richard Charles Archuleta A thesis submitted in partial fulfillment of the requirement's for the degree of Master of Science in Chemical Engineering MONTANA STATE UNIVERSITY Bozeman, Montana June, 1991 i i APPROVAL of a thesis submitted by Richard Archuleta This thesis has been read by each member of the thesis committee and has been found to be satisfactory regarding content, English usage, format, citations, bibliographic style, and consistency, and is ready for submission to the College of Graduate Studies. Date 3 Chafrpersdn, Graduate Committee Approved for the Major Department <— c tT /f ____________ — Date Head, Maj or Department Approved for the College of Graduate Studies D & te Graduafte Dean iii STATEMENT OF PERMISSION TO USE In presenting this thesis in partial fulfillment of the requirements for a master's degree at Montana State University, I agree that the Library shall make it available to borrowers under rules of the Library. Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgement of source is made. Permission for extensive quotation from or reproduction of this thesis may be granted by my major professor, or in his/her absence, by the Dean of Libraries when, in the opinion of either, the proposed use of the material is for scholarly purposes. Any copying or use of the material in this thesis for financial gain shall not be allowed without my written permission. Signature Date ACKNOWLEDGEMENTS I would like to thank those who contributed to my efforts in completion of my research. My thanks to. Mr. Lyman Fellows, the Chemical Engineering technician who helped significantly in building and repairing the hydrolyzer. To Dr. Max Deibert, who impressed upon me the importance of maturity in conducting research. I would also like to thank Max for the guidance given to me, and the support I needed when things were not going as planned. To Rajesh Mirpuri, my graduate studies friend who made life easier when research Was not. My thanks to the rest of the Chemical Engineering Department for their continual support and persistence in educating my stressed mind. Finally, I would like to thank Rebekah Keene who helped me through this long process and gave me support when I most needed it. V TABLE OF CONTENTS Page 1. INTRODUCTION ............................................ I Industrial Uses for Fat and Oil Hydrolysis Products ............................................. I The Chemistry of Fat and Oil Hydrolysis ........... 2 2. CURRENT INDUSTRIAL HYDROLYSIS TECHNOLOGY ............. 5 The Colgate-Emery Process .......................... 5 Reaction Kinetics of Hydrolyzing FatS and Oils .... 6 3. THE FEASIBILITY OF STEAM HYDROLYSIS .................. 8 Steam Hydrolysis of Fats and O i l s ................. 8 Previous Experimental Results on Steam Hydrolysis . 10 Research Objectives.................................. 11 4. THE BENCH SCALE HYDROLYZER ............................ 12 Background............................................12 The Steam Feed System ................. 13 The Fat/Oil Feed System ............................ 19 The Hydrolyzer...................................... 2 3 The Bottoms Product Collection System ............. 28 The Overhead Product Collection System ............ 30 Temperature Monitoring Thermocouples .............. 33 Temperature Control ................................. 33 5. OPERATING THE HYDROLYZE R ...... ........................ 3 5 Start-Up Procedure .................................. 35 Operating Procedure.................................. 37 Shut-Down Procedure ................................. 38 6. CHEMICAL ANALYSIS OF HYDROLYZER FEEDS AND PRODUCTS ... 40 Product An a l y s i s ................................ 40 Degree of Hydrolysis......... 40 Acid Value Procedure................................4 2 Saponification Value Procedure............ 43 7. HYDROLYZER MATERIALS INVESTIGATION ................. ... 4 5 v i TABLE OF COMTENTS-Continued Page 8. DETERMINATION OF OPERATION PARAMETERS FOR TESTING .... 47 9. RESULTS OF HYDROLYZER INVESTIGATION ................. 52 10. DISCUSSION............................................... 59 Steady State Analysis of the Hydrolyzer ........... 59 Temperature Effects on the Rate of Reaction ...... 60 Steam Feed Effects on the Rate of Reaction ....... 60 Overhead and Bottoms Product Analysis ............. 61 Stage Product Analysis ............................. 62 Decomposition of the Reaction Products ...... .... 62 Commercial Feasibility of Steam Hydrolysis ....... 63 11. SUMMARY AND CONCLUSIONS................................ 64 12. RECOMMENDATIONS FOR FUTURE RESEARCH ................ .. 66 REFERENCES CITED ............................................ 68 v i i LIST OF TABLES Ie Page 1. Thermocouple Numbering on the Selector Switch ... 34 2. Corrosion Rates of Various Metal Alloys ......... 46 3. Investigated Flow Tests for the Hydrolyzer ..... 51 4. Overall Degree of Hydrolysis for Run I Measured During Reactor Operation Using Equation I ...... 52 5. Overall Degree of Hydrolysis for Run I from the Analysis of Collected Reactor Samples Using Equation 2 .......................................... 53 6. Overall Degree of Hydrolysis for Run 2 Measured During Reactor Operation Using Equation I ........ 54 7. Overall Degree of Hydrolysis for Run 2 from the Analysis of Collected Reactor Samples Using Equation 2 ........................................ 54 8. Overall Degree of Hydrolysis for Run 4 Measured During Reactor Operation Using Equation I ....... 55 9. Overall Degree of Hydrolysis for Run 4 from the Analysis of Collected Reactor Samples Using Equation 2 ......... 55 10. Overall Degree of Hydrolysis for Run 5 Measured During Reactor Operation Using Equation I . 56 11. Overall Degree of Hydrolysis for Run 5 from the Analysis of Collected Reactor Samples Using Equation 2 ........................................ 56 12. Residence Time of the Tallow and Steam in the Reactor ............................................ 57 13. Degree of Hydrolysis for Stages One Through Four 58 v i i i LIST OF FIGURES Figure Page 1. The Bench Scale Hydrolyzer ............... ......... 14 2. The Steam Feed System .............................. 15 3. Needle Valve Calibration of Steam Feed ..... ...... 18 4. The Fat/Oil Feed System ............................ 2 0 5. Feed Pump Calibration for Tallow F e e d ............ 22 6. Hydrolyzer Stage Design................. * . ......... 25 7. Hydrolyzer Stage Disperser Plate .............. 26 8. Bottoms Product Collection System ................. 29 9. Overhead Product Collection System ................ 31 10. Hydrolyzer Operation Range for Nitrogen/Water Feed 49 i x ABSTRACT The hydrolysis of fats or oils with water produces fatty acids and glycerol. Currently, the countercurrent, continuous, high pressure, high temperature, liquid phase Colgate-Emery process, which uses a catalyst to promote the reaction, is the state-of-the-art method of fat hydrolysis. Non-catalytic steam hydrolysis is a possible alternative. Significant degrees of hydrolysis may be achieved by continuously sparging superheated steam through high temperature fat at atmospheric pressure. A "bench-scale" hydfolyzer was designed and constructed to investigate the feasibility of steam hydrolysis and was tested with soybean oil and beef tallow. Each of the five stages in the 316 Stainless Steel, 1.77 inch inside diameter, 18-3/4 feet high hydrolyzer included a riser, a downcomer, and a steam dispersion plate similar to a distillation column. Investigations of the degree of hydrolysis were conducted at various temperatures and fat/steam feed ratios. The compositions