Design of a Small-Scale Supercritical Water Oxidation Reactor. Part I: Experimental Performance and Characterization

Abstract

<p>A small-scale supercritical water oxidation reactor is designed and fabricated to study the destruction of hazardous wastes. The downward bulk flow is heated with the introduction of pilot fuel (ethanol/water mixture), and oxidant (H<sub>2</sub>O<sub>2</sub>/water mixture). Both streams are introduced coaxially. The fuel dilution is varied from 2 to 7 mol% ethanol/water, and the oxidant-to-fuel stoichiometric equivalence ratio (Φ<sub>AF</sub>), is varied from 1.1 to 1.5. Higher ethanol concentrations in the pilot fuel stream and operation near-stoichiometric results in a more stratified temperature profile, i.e., highest local fluid temperatures near the top and the lowest temperatures at the bottom of the reactor. Steady operation at 603.5 °C is achieved with a nominal residence time of 25.3 s at 7 mol% fuel dilution and Φ<sub>AF</sub> of 1.1. At the lowest pilot fuel dilution (2 mol%), the temperature profile is nearly uniform, approaching a distributed reaction regime.</p>

Design of a Small-Scale Supercritical Water Oxidation Reactor. Part II: Numerical Modeling

“…The 2D axisymmetric CFD domain matches the geometry of the SCWO reactor described in the adjacent paper. 50 The computational domain comprises a fluid volume representing the reactor zone and the solid volumes to simulate the heat transfer through the reactor's walls, as shown in Figure 1. The fluid domain includes two coaxial, inlet tubes for fuel and the oxidant injection.…”

“…A series of SCWO experiments were performed to study the oxidation of ethanol. 50 The cases considered in this study are presented in Table 3. The fuel inlet flow is a mixture of ethanol diluted with water.…”

“…The study reports the results of numerical simulations of a bench-scale SCWO reactor operated with ethanol as a fuel and H 2 O 2 as an oxidant. 50 In experiments reported in the joint manuscript, fuel dilution was varied, and the fluid and wall temperatures were measured in multiple locations. The reactor operation is modeled for the range of operating conditions in a 2D axisymmetric domain.…”

Design of a Small-Scale Supercritical Water Oxidation Reactor. Part II: Numerical Modeling and Validation

“…The CFD domain is designed to correspond with the dimensions of the SCWO reactor described in the adjacent paper. 73 The computational domain comprises a fluid mesh representing the reactor zone and a solid mesh to simulate the heat transfer through the walls of the reactor and insulation, as shown in Figure 1…”

“…A series of SCWO experiments were performed to study the oxidation of ethanol. 73 The cases considered in this study are presented in Table 4. The fuel inlet flow is a mixture of ethanol diluted with water.…”