TITLE:
Evaluating the Technical and Economic Feasibility of Adding a Power Recovery System to the Steam Condenser of a Lignite Coal-Fired Power Plant
AUTHORS:
Joshua Wilmer, Wayne Seames, Dimitri Bazile, Kay Lee Smith, Benjamin Koster, Grady Mauch, Lucas Weimer
KEYWORDS:
Lignite Coal, Heat Recovery, Power Plant, Organic Rankine Cycle, Bottoming Cycle
JOURNAL NAME:
Journal of Power and Energy Engineering,
Vol.10 No.11,
November
29,
2022
ABSTRACT: Steam is the typical working fluid to drive turbo-generatorsin coal-fired power plants. It is an effective working fluid, but some of its energy is extracted in an unusable form when condensed. A Power Recovery Cycle (PRC) using a more volatile Secondary Working Fluid (SWF) added to the steam cycle could improve energy efficiency. PRCs have been applied to the flue gas and for combined cycle systems but not to traditional plant steam cycles. This paper details an analysis of adding a steam cycle PRC to a 500 MW lignite coal-fired power plant. A validated model of the plant was developed and PRCs using the three most attractive SWFs, benzene, methanol and hydrazine, were then added to the model. Adding a benzene, methanol, or hydrazine steam cycle PRC will produce an additional 59, 34, and 49 MW, respectively. An AACE Class 4 factored broad capital cost estimate and comparable operating costs and revenue estimates were developed to evaluate PRC feasibility. The benzene, methanol, and hydrazine processes had 2019 Net Present Values (NPVs) @12% of -$32, -$59, and +$35 million ± 40%, respectively. Thus, a PRC may be profitable at current or modest increases to U.S. Upper Midwest electricity prices of around $0.0667/kWh.