Design, Fabrication, and Operational Parameters of a Supercritical Water Oxidation Reactor Stuart J. Moore A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science University of Washington 2020 Committee: Igor Novosselov, Chair John Kramlich Per Reinhall Program Authorized to Offer Degree: Mechanical Engineering © Copyright 2020 Stuart J. Moore University of Washington Abstract Design, Fabrication, and Operational Parameters of a Supercritical Water Oxidation Reactor Stuart J. Moore Chair of the Supervisory Committee: Igor V. Novosselov Department of Mechanical Engineering Supercritical Water Oxidation (SCWO) has been shown to efficiently destroy wet organic wastes. The process, iterations, and lessons learned during the design and fabrication process of a continuous, inverted SCWO reactor are described. Ethanol is oxidized in a continuous inverted supercritical water oxidation reactor at 25 MPa, with oxidant and fuel preheat temperatures of 380 to 450 °C. Optimal conditions for future operation are found by operating at various premixed fuel concentrations of 0-7 mol% ethanol in water, varying the air to fuel equivalence ratio from 1.1 to 1.8, and utilizing air and hydrogen peroxide as the oxidant. Experimental conditions are chosen for analysis of reactor temperatures during complete oxidation of pilot fuel, where ethanol will rapidly oxidize. Higher premixed concentrations of ethanol produce a more localized, higher temperature reaction occurring closer to the nozzle with longer residence times. Preliminary results find the use of air results in lower reaction temperatures than hydrogen peroxide at similar operational conditions due to nitrogen loading; the experiments with air are still on-going. The results are used to determine the capability of the reactor for the destruction of toxic organic compounds. TABLE OF CONTENTS: TABLE OF FIGURES: .............................................................................................................................. 3 ACKNOWLEDGEMENTS: ....................................................................................................................... 5 1. INTRODUCTION ................................................................................................................................ 6 1.1 The Problem and Proposed Solution .................................................................................. 6 1.2 Scope of the Thesis ................................................................................................................. 8 2. REVIEW OF SUPERCRITICAL WATER OXIDATION REACTORS ........................................ 9 2.1 History and Background of Supercritical Water Oxidation Reactors ........................ 9 2.2 Challenges ................................................................................................................................. 9 2.2.1 Corrosion ........................................................................................................................... 9 2.2.2 Salt Precipitation and Clogging ................................................................................. 11 2.2.3 High Operational Costs ................................................................................................ 11 3. DESIGN 1 .......................................................................................................................................... 12 3.1. Design Concept ...................................................................................................................... 12 3.1.1 Tubing, Fittings, and Material Selection .................................................................. 12 3.1.2 Reactor Section .............................................................................................................. 13 3.1.3 Pump Selection and Pressure Generation .............................................................. 15 3.1.4 Heater Subsystem .......................................................................................................... 16 3.2 Safety and Design 1 Amendments .................................................................................... 16 3.3 Experimental Parameters ..................................................................................................... 17 3.4 Procedure and Results ......................................................................................................... 18 3.5 Observations & Lessons Learned ..................................................................................... 21 3.5.1 Inadequate Sheath Flow Cooling ............................................................................... 21 3.5.2 Nozzle to Reactor Diameter Ratio .............................................................................. 22 3.5.3 Fuel Dilution .................................................................................................................... 23 3.5.4 Back Pressure Regulator Failure ............................................................................... 23 4. DESIGN 2 .......................................................................................................................................... 25 4.1 Design 2.1 – Upright Hydrothermal Flame Reactor ...................................................... 25 4.1.1 Reactor Section .............................................................................................................. 26 4.1.2 Insulation .......................................................................................................................... 28 4.1.3 Back Pressure Regulator ............................................................................................. 29 1 4.2 Upright Reactor Analysis ..................................................................................................... 29 4.3 Design 2.2 – Inverted Supercritical Water Oxidation Reactor .................................... 31 4.3.1 Air and Oxidant Lines ................................................................................................... 32 4.3.2 Reagent Line ................................................................................................................... 33 4.3.3 Back Pressure Regulator and Additional Heat Exchanger ................................. 34 4.3.4 Pumps ............................................................................................................................... 34 4.3.5 Insulation and TCs ......................................................................................................... 34 4.3.6 Solenoids and Controls ................................................................................................ 35 5. RESULTS .......................................................................................................................................... 36 5.1 Operation with H2O2 ............................................................................................................. 36 5.1.1 Preignition Operation .................................................................................................... 36 5.1.2 Effects of Air Fuel Ratio ............................................................................................... 40 5.1.3 Effects of Fuel Dilution ................................................................................................. 43 5.1.4 Pump Troubles................................................................................................................ 48 5.2 Operation with Air .................................................................................................................. 48 6. CONCLUSION .............................................................................................................................. 53 REFERENCES ......................................................................................................................................... 55 A. APPENDIX .................................................................................................................................... 59 A.1 Standard Operating Procedure (SOP) .............................................................................. 59 A.2 Supplementary Figures ........................................................................................................ 66 2 TABLE OF FIGURES: Figure 1: Density and specific heat properties of water at 25MPa [30]. ............................................ 7 Figure 2: Design 1 reactor schematic, with hydrogen peroxide as oxidant..................................... 15 Figure 3: Inverted hydrothermal flame reactor assembly. Not pictured for clarity: Heating tape, insulation from the heaters through the reactor section. .................................................................... 17 Figure 4: Thermocouple data from autoignition experiment: fuel EtOH30% in water, oxidant 30% H2O2 in water. The x-axis is representing time in hours: minutes. The spike in Reactor Section TC denotes the time and presence of a flame. .................................................................................... 20 Figure 5: Left: Titanium liner melted during operation. Right: Oxidizer nozzle. Note that only the surrounding oxidant line melted while the center fuel line saw only minor discoloration. ............. 21 Figure 6: Schematic of Design 2.1, an upright hydrothermal flame reactor. ................................... 26 Figure