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Research Papers

# Exergetic, Thermal, and Externalities Analyses of a Cogeneration Plant

[+] Author and Article Information
Margaret B. Bailey1

Rochester Institute of Technology, Department of Mechanical Engineering, Rochester, NY 14623-5604margaret.bailey@rit.edu

Peter Curtiss

Curtiss Engineering, Boulder, CO 80305peter@petercurtiss.com

CPT Paul H. Blanton

United States Army, 305 Longfellow Ave., Worthington, OH 43085

CPT Thomas B. McBrayer

United States Army, Springmeadow #5, Midland, TX 79701

1

Corresponding author.

J. Sol. Energy Eng 128(1), 98-103 (Feb 02, 2005) (6 pages) doi:10.1115/1.2148973 History: Received July 23, 2003; Revised February 02, 2005

## Abstract

A thermodynamic study of an $88.4MW$ cogeneration plant located in the United States is presented in this paper. The feedstock for this actual plant is culm, the waste left from anthracite coal mining. Before combustion in circulating fluidized bed boilers, the usable carbon within the culm is separated from the indigenous rock. The rock and ash waste from the combustion process fill adjacent land previously scared by strip mining. Trees and grass are planted in these areas as part of a land reclamation program. Analyses based on the first and second laws of thermodynamics using actual operating data are first presented to acquaint the reader with the plant’s components and operation. Using emission and other relevant environmental data from the plant, an externalities study is outlined that estimates the plant’s effect on the local population. The results show that the plant’s cycle performs with a coefficient of utilization of 29% and an approximate exergetic efficiency of 34.5%. In order to increase these values, recommended improvements to the plant are noted. In addition, the externality costs associated with the estimated $SO2$ and $NOX$ discharge from the culm fed plant are approximately $1mil∕kWh$ produced. This is considerably lower (85–95%) than those associated with a similarly sized coal fed plant. The plant’s cycle efficiencies are lower than those associated with more modern technologies; such as an integrated gas turbine combined cycle. However, given the abundant, inexpensive supply of feedstock located adjacent to the plant and the environmental benefit of removing culm banks, the plant’s existing operation is unique from an economical and environmental viewpoint.

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## Figures

Figure 1

Culm is separated from rock and stored in piles before it is taken up to the plant via a conveyor belt

Figure 2

Schematic of cogeneration plant with all state points and devices shown

Figure 3

Example of data and modeling requirements for externalities study

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