CO2 content

Abstract: A Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) based cathode intermediate temperature solid oxide fuel cell (IT-SOFC) was fabricated and tested. The effect of carbon dioxide on the performance of BSCF cathode was evaluated at temperatures ranging from 450 to 750 °C. The current density was recorded at a constant discharge of voltage value and the electrochemical impedance spectra (EIS) measurements were carried out in the absence and in the presence of CO2 in the oxidant gas line (cathode). It was found that the presence even of relatively small quantities (0.28–3.07%) of CO2 negatively affects the H2-IT-SOFC performance. It was shown that as the CO2 content in the cathode side increases and as the operation temperature decreases, the fuel cell performance is seriously aggravated up to 550 °C in a reversible way. A further decrease of the operation temperature deteriorates the SOFC performance irreversibly. However, the cell performance can be recovered after treatment at 800 °C in pure oxygen. It was also shown that as the CO2 content increases, the rate of oxygen electrochemical reduction decreases and the corresponding apparent activation energy increases linearly. The EIS results show that the interface resistance increases dramatically after carbon dioxide is added into the oxidant gas line. It is believed that carbon dioxide and temperature, acting in a synergetic way, decrease at least the cathode activity for oxygen reduction. This behaviour could be attributed to the strong carbon dioxide adsorption on the BSCF surface and to the formation of carbonates at temperatures as low as 500 and 450 °C.

Abstract: The Dongfang gas field, located in a diapir structure zone, is the largest gas field found in the Yinggehai Basin. A strong thermal anomaly caused by hydrothermal fluid flows occurs in the gas field, as evidenced from drill-stem test and fluid inclusion homogenization temperatures, Rock-Eval Tmax, vitrinite reflectance, and clay-mineral transformation profiles. Such a thermal anomaly suggests focused, rapid flow of deeply sourced hydrothermal fluids, which has shifted the threshold depth to the onset of hydrocarbon generation upward by about 500 m. The Dongfang gas field shows considerable variation in nitrogen and carbon dioxide content, with nitrogen content ranging from less than 5 to 31.2% and carbon dioxide content ranging from less than 1 to 88.9%. Hydrocarbon gases and associated condensates show high maturities and have been generated most probably from the Meishan and Sanya formations of Miocene age. Carbon dioxide in gases with CO2 content less than 10% is organic in origin, whereas carbon dioxide in gases with CO2 content higher than 10% is inorganic in origin and has been generated from high-temperature decomposition of carbonates. Most gases display negative d15N values. Gases with nitrogen content higher than 15% always contain organic CO2 (CO2d13C values lighter than -10o/oo,), and the nitrogen contents decrease as the d13C values for methane and ethane become heavier, suggesting an organic origin of the nitrogen gas generated in the catagenetic stage (source rock Ro <2.0%), before the significant thermal decomposition of carbonate took place. Systematic interreservoir compositional heterogeneities occur in the gas field, which, along with the thermal regime and fluid-inclusion homogenization-temperature measurements, give a clear suggestion of the reservoir-filling history: methane-dominated gases with relatively high nitrogen content and a small amount of organic CO2 accumulated first, and carbon dioxide-rich gases with hydrocarbon components of higher maturity injected into the reservoir later. Interreservoir compositional heterogeneities, which have the advantage of being unaffected by in-reservoir mixing processes, can be effective indicators of the field-filling history, especially when they are studied in combination with fluid-inclusion and reservoir-diagenesis analyses. The short-lived, transient nature of the thermal effect of fluid flow and the wide variation of the toluene/n-heptane values seem to suggest episodic fluid injections from the overpressured systems into the reservoirs.

Abstract: Carbon dioxide is removed from CO 2 and hydrocarbon containing gaseous streams. In the instance where the hydrocarbons and CO 2 are such that hydrocarbons would condense out during CO 2 removal, the gas stream is treated in one or more stages to accomplish hydrocarbon composition control.