Integrated gasification combined cycle (IGCC) processes have the potential for high thermal efficiency with a low energy penalty for carbon capture. Many researchers have proposed various innovations to improve upon the efficiency of the IGCC process. However, the analysis methods of most publications are generally not transparent and these published results are exceedingly difficult to reproduce.

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.

Oxy-fuel combustion technology is an attractive option for capturing carbon dioxide (CO2) in power generation systems utilizing hydrocarbon fuels. However, conventional atmospheric oxy-fuel combustion systems require substantial parasitic energy in the compression step within the air separation unit (ASU), the flue gas recirculation system and the carbon dioxide purification and compression unit (CPU). Moreover, a large amount of flue gas latent enthalpy, which has high water concentration, is wasted. Both lower the overall cycle efficiency.Pressurized oxy-fuel combustion power cycles have been investigated as alternatives. Our previous study showed the importance of operating pressure for these cycles. In this paper, as the extended work of our previous study, we perform a pressure sensitivity analysis to determine the optimal combustor operating pressure for the pressurized oxy-fuel combustion power cycle. We calculate the energy requirements of the ASU and the CPU, which vary in opposite directions as the combustor operating pressure is increased. We also determine the pressure dependence of the water-condensing thermal energy recovery and its relation to the gross power output. The paper presents a detailed study on the variation of the thermal energy recovery rate, the overall compression power demand, the gross power output and the overall net efficiency. 2

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Reactive absorber columns Sulfuric acid and nitric acid production Sensitivity analysis and parametric studies NO, NO 2 and SO 2 removal a b s t r a c t Oxy-coal combustion has great potential as one of the major CO 2 capture technologies for power generation from coal. In oxy-coal combustion, the oxygen source is a high concentration oxygen stream and the product flue gas consists primarily of CO 2 and H 2 O with contaminants like nitrogen oxides (NO X ), sulfur oxides (SO X ) and non-condensable gases like argon, oxygen and nitrogen. NO X and SO X removal can be achieved via traditional selective catalytic reduction (SCR) and flue gas desulfurization (FGD). These traditional methods however result in relatively high capital cost and energy requirement and face complex material handling challenges. White et al. proposed a different approach to NO X /SO X removal based on the nitric acid and lead-chamber chemistry process (White et al., 2010). This two-column design utilizes an intermediate and a high-pressure reactive absorption column connected in series to respectively remove SO X and NO X from the high CO 2 -concentration flue gas. In this study, we propose a modification to this two-column process that achieves the complete removal of SO X and NO X from the CO 2 stream in a single column. We demonstrate by means of pressure sensitivity studies that this new design can meet the same separation targets as the two-column process in fewer column stages and half the feed water requirement by exploiting the pressure dependence of the rate determining NO oxidation reaction. Furthermore, we make use of parametric studies to analyze the dependence of NO X /SO X removal on key design and operating parameters for the proposed system: pressure, vapor hold-upper stage and water flow rate. Results show that the process is strongly pressure dependent, with a 3-order of magnitude decrease in required residence time when the operating pressure is varied from 4 bars to 30 bars. Vapor holdup volume and feed water flow rate have a significant impact on NO X /SO X removal up to a point -about 20 m 3 and 2 kg/s respectively for the case analyzed. Beyond these values, column performance shows substantially less sensitivity to increasing holdup volume or water flow rate. The analysis presented in this paper also shows that recycling bottoms liquid can reduce the feed water requirement by up to 40% without significantly affecting the exit gas purity.