An Evaluation of Hybrid Coal Combustion Technology for Repowering H.F. Lee Unit 2

Abstract

Combustion-based hybrid systems use coal as fuel, and employ combustion technologies in combination with a gas turbine in a number combined cycle configurations. One of these hybrid systems is known by its acronym: CHIPPS, for: ‘combustion-based high-performance power system.’ CHIPPS is a coal-fueled technology that is suited for repowering units that have boilers in good condition, as it continues the use of the existing furnace and steam tubes. This paper describes a conceptual evaluation to establish the feasibility of using CHIPPS technology to repower an existing coal-fired steam plant. The H.F. Lee power plant, owned by CP&L Progress Energy, is located on the Neuse River, just outside Goldsboro, North Carolina. CHIPPS would repower Unit 2, a 1950’s era non-reheat steam unit, one of the three units at this site. If CHIPPS repowering proved feasible for Unit 2, it would likely be a good choice for a wide range of other similar units throughout the U.S. CHIPPS retains the use of the existing Unit 2 furnace and steam turbine/generator, but adds a combustion turbine to increase energy efficiency in a way that makes this coal-fired plant nearly as efficient as a combined cycle power plant that would otherwise use more expensive natural gas. The CHIPPs technology concept used employs a Foster Wheeler circulating fluidized bed partial gasifier that would supply syngas to a General Electric 6B combustion turbine. Only a portion of the coal is gasified to syngas. The remaining coal energy is transferred as char to the lower of three boiler burner rows of the existing Unit 2 furnace that would be fitted with special burners for the char. The upper two rows are not changed and continue to burn coal from the existing mills. With CHIPPS: • Output is expected to increase from 78,520 kW to 139,750 kW, • 7 percent less fuel would be needed per kWh generated, • Environmental improvement would become exemplary, however, • Cost is high, about $214,606,000; Unit 2 is too small for attractive economics, and a non-reheat unit leads to only modest efficiency improvement. Future CHIPPS repowering might be better suited for a larger reheat steam plant instead of at H.F. Lee Unit 2. This paper summarizes the CHIPPS repowering power plant concept and describes: • An overview of the CHIPPS process; • A description of the existing H.F. Lee Unit 2; • An estimate of the performance improvements expected with Unit 2 repowered with CHIPPS; • An estimate of the environmental performance expectation from the unit with CHIPPS; and, • An estimate of the expected costs to upgrade the unit. Significant conclusions and suggestions for where this class of hybrid combustion technologies might best be applied.