Jason W. Picou

Noncatalytic Reformation of JP-8 Fuel in Supercritical Water for Production of Hydrogen

Abstract A novel process is developed where hydrogen is generated via direct noncatalytic reformation of liquid hydrocarbon fuels such as diesel and JP-8 fuel in supercritical water. In this process, supercritical water functions as a reforming agent and as a solvating reaction medium. The high enthalpy level of supercritical water and the extraordinary solubility of hydrocarbon fuel components in supercritical water allow the reformation reaction to proceed without a heterogeneous catalyst that is typically required for the conventional reformation process. Typical operating temperature and pressure ranges for this reformation process are: 650°C–825°C and 22–33 MPa. The process feasibility of the supercritical water reformation of JP-8 fuel was demonstrated in a tubular reactor (Generation-I SWR Reactor) made of Inconel-625 alloy (Grade 1) whose dimensions are 2.54-cm internal diameter and 183-cm internal length. The following scientific and technological issues were investigated in-depth: (a) long-term continuous reactor operability, (b) capability of handling high sulfur containing liquid fuel without cumbersome pre-desulfurization, (c) potentially varying supercriticality of the reactant and product mixtures along the reactor length, (d) principal reactions in the process chemistry, (e) coke formation and its prevention, (f) competitive productivity between H2 and CH4 and its significance, (g) feasibility of autothermal mode of operation by co-feeding air or oxygen into the reactor, (h) effects of fuel components on the overall process efficiency, and (i) desired mechanical properties of the reactor material of construction.

Kinetic Modeling of Supercritical Water Reformation of JP-8 Fuel

Abstract A global first-order kinetic study is conducted for a novel supercritical water reformation process of JP-8 fuel. The process uniquely employs supercritical water both as a homogenizing reaction medium and also as a highly energetic reactant of reformation. The complex reaction chemistry is mathematically modeled using two simplified reaction mechanisms involving two different reaction sequences and routes between pyrolysis and reformation reaction steps. First-order kinetics are assumed for all mechanistic reaction rates. The mathematical models are analyzed using the kinetic data obtained on a Generation-I reactor made of Inconel 625 Grade I alloy. The crossover temperature is defined and computed as the temperature above, which the mechanistic rate of reformation of JP-8 overtakes that of the pyrolysis of JP-8 hydrocarbons. The Arrhenius kinetic parameters for both pyrolysis and reformation reactions are found based on the two mechanistic routes proposed. It is found that the two mechanistic models adequately analyze the reaction kinetics and predict the crossover temperature in a close vicinity of each other. The study not only helps elucidate the complex reaction phenomena of the novel process, but also points to the right direction of the process optimization and design of a Generation-II reactor.

Kinetics of the Non-catalytic Water Gas Shift Reaction in Supercritical Water

A kinetic analysis of the noncatalytic water gas shift reaction in a supercritical water medium was investigated using a specially designed 383 mL Haynes Alloy 230 tubular reactor at a constant pressure of 24.12 ± 0.04 MPa, water to carbon monoxide molar feed ratios of 5 to 37 moles of water per mole of carbon monoxide, and at temperatures varying from 768 to 1,048 K. The carbon monoxide concentration in the effluent gas reached a minimum of one mole-percent at 1,048 K, which corresponds to a 98% carbon monoxide to carbon dioxide conversion. Using global first-order kinetics a frequency factor of 105.76 ± 1.42 s−1 and an activation energy of 139.8 ± 24.5 kJ/mol was determined. It was also found that the developed kinetic rate model closely fits the experimental reaction data, with a coefficient of determination of R2 = 0.95, over a wide range of temperatures and reactant concentrations.

A Kinetic Model Based on the Sequential Reaction Mechanism for the Noncatalytic Reformation of Jet Fuel in Supercritical Water

Abstract An experimental kinetic study was performed on the supercritical water reformation of jet fuel to account for the interactive contributions of three principal reactions that are taking place, viz., non-catalytic reformation of original and fragmented hydrocarbon molecules, pyrolysis of hydrocarbon molecules, and water gas shift reaction. Experiments were conducted non-catalytically using supercritical water and jet fuel in a specially designed 926 mL Inconel 625 Grade-1 tubular reactor at temperatures varying from 803 to 972 K at a pressure of 24.15 ± 0.06 MPa. The Arrhenius activation energies and frequency factors were obtained for each of the three principal reactions.