Thermal stressing of Jet-A was conducted in a flow reactor on iron- and nickel-based metal surfaces at a fuel flow rate of 1 mL/min for 5 h at a wall temperature of 350 °C and 3.5 MPa (500 psig) so that both liquid-phase autoxidation and thermal decomposition of autoxidation products contribute to the formation of carbonaceous deposits. The deposits produced were characterized by field emission scanning electron microscopy (FESEM) and temperature programmed oxidation (TPO). The effect of metal surface on deposit formation increases in the following order: AISI316 < AISI 321 ≈ AISI 304 < Inconel 600 < AISI 347 < Inconel 718 < FecrAlloy < Inconel-750X. The variation in the activity of the metal substrates is attributed to their reaction with reactive sulfur compounds in the fuel and interaction of oxygenated intermediates formed by autoxidation during thermal stressing.
Thin films of alumina, zirconia, tantalum oxide, and platinum were deposited on AISI304 by metal–organic chemical vapor deposition to investigate the effectiveness of these coatings in inhibiting carbon deposition and sulfide formation from thermal oxidative degradation of jet fuel. Coated AISI304 foils were heated in a laboratory scale flow reactor with a commercial jet fuel (Jet-A) flowing at 1 mL/min at a wall temperature of 350 °C and reactor pressure of 500 psig (3.4 MPa) for 5 h. Under these conditions, both liquid phase autoxidation and thermal decomposition of jet fuel contribute to carbon deposition. The surface composition of the metal oxide coatings was found by X-ray photoelectron spectroscopy. The morphology of the coating and the carbonaceous deposits formed during thermal stressing were examined by field emission scanning electron microscopy. The amount of solid carbonaceous deposits on the coated and uncoated surfaces was measured by temperature-programmed oxidation. The effectiveness of the coatings in mitigating carbon deposition was found to decrease in the following order: platinum > Ta2O5 > alumina from acetyl acetonate > ZrO2 > alumina from aluminum trisecondary butoxide > AISI304. The coatings cover the metal surface by forming a protective layer that inhibits the formation of metal sulfides from the reaction of sulfur compounds in jet fuel with iron and nickel on stainless steel and inconel surfaces, respectively. The variation in the activity of the coatings can be attributed to the interaction of oxygenated intermediates formed by autoxidation during thermal stressing with coating surfaces having different degrees of acidity.
The global warming potential of carbon dioxide (CO 2) emphasizes more the sequestration of CO 2 otherwise emitted from coal-fired power plants in the future. This study is focused on pairing a coal-fired Integrated Gasification Combined Cycle (IGCC) plant with Enhanced Geothermal System (EGS) for simultaneous sequestration of CO 2 and extraction of geothermal heat energy for subsequent electricity generation by an Organic Rankine Cycle (ORC) in enhanced geothermal systems (EGS). By assuming the reservoir characteristics for two different geothermal source temperatures 200 °C and 300 °C, heat transfer calculations show that larger reservoir volume (> 1 km 3) is necessary for the sustained extraction of geothermal heat energy over a period of 25 years. The temperature and pressure profiles of CO 2 in the injection well and the production well, the corresponding power output from the ORC for five different working fluids, are simulated by ASPEN Plus Version 7.3. The reservoir conditions and the type of working fluid selected determine the power output in the ORC. The temperature and the pressure of the CO 2 at the outlet of the production well are greater than that at the injection well due to the heating of CO 2 in the reservoir during the extraction of geothermal heat energy. Therefore, a
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