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Thermodynamic Equilibrium Calculations (thermodynamic + equilibrium_calculation)
Selected AbstractsThermodynamic Equilibrium Calculations for the Reforming of Coke Oven Gas with Gasification GasCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2007B. Li Abstract Thermodynamic analyses of the reforming of coke oven gas with gasification gas for syngas were investigated as a function of coke oven gas-to-gasification gas ratio (1,3), oxygen-to-methane ratio (0,1.56), pressure (25,35,bar) and temperature (700,1100,°C). Thermodynamic equilibrium results indicate that the operating temperature should be approximately 1100,°C and the oxygen-to-methane ratio should be approximately 0.39, where about 80,% CH4 and CO2 can be converted at 30,bar. Increasing the operating pressure shifts the equilibrium toward the reactants (CH4 and CO2); increasing the pressure from 25 to 35,bar decreases the conversion of CO2 from 73.7,% to 67.8,%. The conversion ratio of CO2 is less than that in the absence of O2. For a constant feed gas composition (7,% O2, 31,% gasification gas, and 62,% coke oven gas), a H2/CO ratio of about 2 occurs at temperatures of 950,°C and above. Pressure effects on the H2/CO ratio are negligible for temperatures greater than 750,°C. The steam produced has an effect on the hydrogen selectivity, but its mole fraction decreases with temperature; trace amounts of other secondary products are observed. [source] Temperature and Impurity Concentration Effects on Degradation of Nickel/Yttria-stabilised Zirconia Anode in PH3 -Containing Coal SyngasFUEL CELLS, Issue 1 2010M. Zhi Abstract Degradation of the Ni/yttria-stabilised zirconia (YSZ) anode of the solid oxide fuel cell has been evaluated in the coal syngas containing different PH3 concentrations in the temperature range from 750 to 900,°C. Thermodynamic equilibrium calculations show that PH3 in the coal syngas gas is converted mostly to P2O3 at 750,900,°C. The phosphorous impurity reacts with the Ni-YSZ anode to form phosphates. The P-impurity poisoning leads to the deactivation of the Ni catalyst and to the reduction in the electronic conductivity of the anode. The impurity poisoning effect on the anode is exacerbated by increase in the temperature and/or the PH3 concentration. [source] Emission of trace toxic metals during pulverized fuel combustion of Czech coalsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2003P. Danihelka Abstract A study of the trace elements emission (As, Se, Cd, Co, Cr, Cu, Zn, Hg, Tl, Pb, Ni, Sn, Sb, V, Mn and Fe) from pulverized coal combustion has been made at six heating and power stations situated in the Czech Republic. The amount of chlorine in coal has considerable influence on volatilization of some elements such as Zn, Cu, Pb, Hg and Tl, which is explained by the formation of thermodynamically stable compounds of these elements with chlorine. Generally, the affinities for Cl follows the order Tl > Cu > Zn > Pb > Co > Mn > Sn > Hg. The experimental data indicates enrichment of some of the trace toxic elements in the emissions (Cu, Zn, As, Se, Cd, Sn, Sb, Hg and Pb) and good agreement was obtained by thermodynamic equilibrium calculations with a few exceptions. In the case of Fe, Mn, Co, Cr and Sn calculated values are overestimated in the bottom ash and there are zero predicted amounts of these elements in the fly ash. In comparison, the results from experiments show up to 80% of these elements retained in fly ash. This implies that there exist additional steps leading to the enrichment by Fe, Mn, Co, Cr and Sn of small particles. Such mechanisms could include the ejection during devolatilization of small inorganic particles from the coal of bottom ash particles, or disintegration of the char containing these metals to small particles of fly ash. On the other hand, there are slightly overestimated or similar values of relative enrichment factors for As, V, Cu, Cd, Sb, Tl and Pb in the fly ashes and zero predicted values for bottom ashes. Our experimental results show about 5% or less of these elements are retained in bottom ashes, so they probably remain in the bottom ash inside unburned parts of coal. Copyright © 2003 John Wiley & Sons, Ltd. [source] Neon abundances in normal late-B and mercury,manganese starsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2000M. M. Dworetsky We make new non-local thermodynamic equilibrium calculations to deduce the abundances of neon from visible-region echelle spectra of selected Ne i lines in seven normal stars and 20 HgMn stars. We find that the best strong blend-free Ne line that can be used at the lower end of the effective temperature Teff range is ,6402, although several other potentially useful Ne i lines are found in the red region of the spectra of these stars. The mean neon abundance in the normal stars (log A=8.10) is in excellent agreement with the standard abundance of neon (8.08). However, in HgMn stars neon is almost universally underabundant, ranging from marginal deficits of 0.1,0.3 dex to underabundances of an order of magnitude or more. In many cases, the lines are so weak that only upper limits can be established. The most extreme example found is , Her with an underabundance of at least 1.5 dex. These underabundances are qualitatively expected from radiative acceleration calculations, which show that Ne has a very small radiative acceleration in the photosphere, and that it is expected to undergo gravitational settling if the mixing processes are sufficiently weak and there is no strong stellar wind. According to theoretical predictions, the low Ne abundances place an important constraint on the intensity of such stellar winds, which must be less than 10,14 M, yr,1 if they are non-turbulent. [source] | ||||||||||