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The purpose of this study is to assess the feasibility of incorporating a Humid Air Turbine (HAT) into a coal-based, indirectly fired High Performance Power System (HIPPS). The HIPPS/HAT power plant exhibits a one percentage point greater thermal efficiency than the combined-cycle HIPPS plant. The capital costs for the HIPPS and HIPPS/HAT plants with identical net power output are nearly equivalent at $1380/kW. Levelized cost of electricity (COE) for the same size plants is 5.3 cents/kWh for the HIPPS plant and 5.4 cents/kWh for the HIPPS/HAT plant; the HIPPS/HAT plant improved thermal efficiency is offset by the higher fuel cost associated with a lower coal/natural gas fuel ratio. However, improved environmental performance is associated with the HIPPS/HAT cycle, as evidenced by lower CO2, SO2, and NOx emissions. Considering the uncertainties associated with the performance and cost estimates of the yet unbuilt components, the HIPPS/HAT and HIPPS power plants are presently considered to be comparable alternatives for future power generation technologies. The Department of Energy’s Combustion 2000 Program will provide revised design specifications and more accurate costs for these components allowing more definitive assessments to be performed.

An analytical model of a n isothennalJuc gas desu firization moving-bed reactor has been developed. The INTRODUCTIONReactors used to reduce the concentration of sulfur dioxide in flue gas through contact with solid adsorbents are generally classified as either fixed bed 151. fluidized bed [12, 131, or moving-bed reacTors [9,161. Although continuous operation can be achieved with either the fluidized bed or moving bed reactors. the reduced amount of sorbent attrition associated with Correspondence concerning this paper should he addressed to Robert Enick. E-mail: enick~enffmn~.pitt.edil. the moving bed reactors has led to increased interest in their application. Solid particles used in moving bed absorbers are typically dry, regenerable metal oxide-impregnated sorbents. such as silica or alumina. These sorbent particles are gravity fed to the reactor. where they are contacted by a cross-flowing flue gas. The sulfur dioxide in the gas stream reacts with the copper oxide on the surface of the sorbent, yielding copper sulfate. After exiting the moving bed reactor, the copper sulfate-rich sorbent particles are subsequently heated and regenerated with a reducing gas.Two geometries have been proposed for moving-bed reactors. Axicylindrical moving bed absorbers are characrerized by the radial, horizontal flow of the gases and doa-nward, vertical, annular flow of the copper oxide adsorbent particles. Gases can be collected along both the axis and the outer perimeter of the reactor, thereby permitting gas flow either toward or away from the reactor axis [Carson, 19841. Simkar reactors have been used for the desulfurization of flue gas using activated carbon [71. Reactors with rectilinear geometries are characterized by the horizontal flow of flue gases through a copper oxide bed moving in a downward. vertical direction [9,10,141. Yeh and coworkers [131 developed an analytical model of the isothermal counterflow fluidized bed reactor. ms model was later extended to the rectilinear cross-flow moving-bed reactor [161 by modeling the moving bed as a two-dimensional army of interconnected nlicroreactors. The equations governing the performance of these microreactors were derived from a differential model for gas-solid counterflow rather than the cross-flow that actually occurs in the moving bed as the downflowing sorbent removes SO2 from the gases flowing in a MATHEMATICAL MODEL OF THE ISOTHERMAL MOVING BED REACTORThe moving bed desulfurization model used in tlu study is provided in Figure 1. The flue gas enters the side of the reactor, while the sorbent particles are gravity fed into the reactor from the top. It is assumed that the horizontal gas flow is distributed over the entire side of the reactor as it passes through the screen that retains the sorbent particles. The slowly moving sorbent bed is assumed to exhibit plug flow, therefore the downward velocity of each sorbent particle is equivalent. Reaction KineticsThe desulfurization reactants include the SO, and 0, in the The SO, concentration in the flue gas ent...

The next generation of coal-fueled power plants must be efficient, clean, and cost-effective. The U.S. Department of Energy (DOE) sponsors a program to develop an advanced, coal-based power system called HIPPS, or High Performance Power System, to meet these requirements. In the HIPPS cycle, air from a gas turbine compressor is indirectly heated in a coal-fueled furnace and then further heated directly with natural gas to power a gas turbine. Indirect heating of the gas turbine working fluid avoids the problems associated with expansion of a corrosive, coal-derived gas through a turbine. Steam is also generated to power a bottoming Rankine cycle. This paper presents an analysis of the performance of HIPPS that is achievable using current technology and projects the level of performance as technology advances. The HIPPS cycle using current technology produces electricity from coal at a thermal efficiency that is more than 40 percent higher than that of today’s average coal-based power plants. The effect of advanced gas turbines, a novel gas turbine cycle, high performance steam cycles, and advanced coal-fueled furnace materials/designs is estimated with the use of computer-based engineering tools. Promising system configurations for future generations of HIPPS are identified with cycle efficiencies as high as 49.3 percent on a higher heating value basis.