It was found from the study that the major influential parameters were moisture content in coal, steam pressures throughout a turbine system, boiler efficiency, temperature of preheated air, and temperatures of both main steam and reheated steam. The obtained parametric effects were quantified and translated into a series of empirical correlations of the net efficiency that could be readily utilized by power industries and engineers. Besides the net efficiency, the magnitude of the energy penalty due to the CO2 capture integration was evaluated and also the optimal level of the CO2 capture target was identified. The sensitivity analysis for cost of electricity was also performed in this study based on different scenarios, i.e., base subcritical pulverized coal-fired power plant without the CO2 capture, subcritical pulverized coal-fired power plant with the CO2 capture using alkanolamine solvent, base supercritical pulverized coal-fired power plant without the CO2 capture, and supercritical pulverized coal-fired power plant with the CO2 capture using alkanolamine solvent.

Coal constitutes an important source of fuel for the production of power in the United States. For instance, in January 2009, pulverized coal (PC) power plants alone contributed to over 45 percent of the Nation's total electric power production. However, PC power plants also contribute to increased emissions of greenhouse gases principally carbon-dioxide (CO2). Recently, various carbon capture strategies have been under active investigation so as to make these plants compete with the more environmental friendly renewable energy sources. One such technology that has received considerable success is the capture of CO2 by an amine-based solvent extraction process. However, an aqueous absorption/stripping technology when used in a PC power plant can reduce the net power output of the plant by as much as 20-40%. The energy penalty comes from heating up the solvent in the regenerator, balancing the enthalpy of reaction, and water stripping. This energy penalty poses considerable limitations on commercial viability of the solvent extraction process and, as a result, various energy-saving modifications have been proposed in the literature ranging from the use of hybrid solvents to novel stripper configurations. In this paper, we show that the energy penalty can be further reduced by heat integration of various PC plant components with the carbon capture system. In addition to the release of greenhouse gases to the environment, PC plants also consume a large amount of freshwater. It is estimated that subcritical and supercritical PC plants have water losses of 714 gal/MWh and 639 gal/MWh, respectively. Water loss is based on an overall balance of the plant source and exit streams. This includes coal moisture, air humidity, process makeup, cooling tower makeup (equivalent to evaporation plus blowdown), process losses (including losses through reactions, solids entrainment, and process makeup/blowdown) and flue gas losses. The primary source of water used in PC power plants is the closed-loop steam-based (Rankine) power cycles. These plants need to condense large quantities of low-pressure steam back to water so that it can be reused to produce high pressure steam. However, this requires the removal of large quantities of heat from the low pressure steam in the condensation process. This is usually done by transferring the heat to cooling water, which in turn transfers this heat to the environment by evaporation to the atmosphere. Also, the inclusion of a carbon capture process can increase the raw water usage by as much as 95 percent. In this work, we use heat exchanger network synthesis followed by an optimization approach to process synthesis for developing strategies for reducing water use in a supercritical PC power plant with a carbon capture and compression system. Uncertainties associated with dry bulb temperature, relative humidity, and demand will also be considered in this analysis.