Growing concerns over greenhouse gas emissions have driven extensive research into new power generation cycles that enable carbon dioxide capture and sequestration. In this regard, oxy-fuel combustion is a promising new technology in which fuels are burned in an environment of oxygen and recycled combustion gases.In this paper, an oxy-fuel combustion power cycle that utilizes a pressurized coal combustor is analyzed. We show that this approach recovers more thermal energy from the flue gases because the elevated flue gas pressure raises the dew point and the available latent enthalpy in the flue gases. The high-pressure water-condensing flue gas thermal energy recovery system eliminates the low-pressure steam bleeding which is typically used in conventional steam cycles and enables the cycle to achieve higher efficiency. The pressurized combustion process provides the purification and compression unit with a concentrated carbon dioxide stream. For the purpose of our analysis, a flue gas purification and compression process including de-SOx, de-NOx, and low temperature flash unit is examined.We compare a case in which the combustor operates at 1.1 bars with a base case in which the combustor operates at 10 bars. Results show nearly 3 percentage point increase in the net efficiency for the latter case.

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Thermodynamic property relations for liquid [3][4] He mixtures between temperatures of 0.15 K and 1.8 K are determined. The relations are valid over the entire concentration range. Thermodynamic properties are first calculated at saturated pressure (which is more or less equal to zero pressure) in the two-phase region, and then extended to the single-phase He-II (up to 1.8 K) and He-I (up to 1.5 K) regions. The calculations at saturated pressure are based on available specific heat data and previously determined sub-0.15 K properties. The property relations are then extended to higher pressures (up to 10 bar) between 0.15 K and 1.5 K, using available molar volume data. The results are largely in good agreement with some other 3 He-4 He mixture property data, though the scarcity of experimental data in large parts of the region of interest precludes a more thorough comparison. Applications of the derived properties to components of sub-Kelvin refrigerators, specifically He-II mixture heat exchangers and He-II mixture throttles, are also discussed.