Technical Briefs

Performance Entitlement of Supercritical Steam Bottoming Cycle

[+] Author and Article Information
S. Can Gülen

Principal Engineer
GE Power and Water,
Schenectady, NY 12345

In other words, if the RBC were a Carnot cycle utilizing the heat extracted from the GT exhaust by cooling it to the reference temperature To its efficiency would be 50%. A modern 3PRH system with an advanced ST is capable only of about 35–38%, i.e., roughly 75% of the entitlement imposed by the second law of thermodynamics.

Currently, duct firing up to ∼750–815 °C is possible in HRSGs equipped with internal lining with insulation and metallic alloy sheet retainers. Above that and up to 925 °C, HRSG walls are lined with refractory materials. Higher temperatures would require water-cooled walls.

1Current address: Bechtel Power, Frederick, MD 21703.

Contributed by the Cycle Innovations Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received September 4, 2012; final manuscript received July 16, 2013; published online September 20, 2013. Assoc. Editor: Wolfgang Sanz.

J. Eng. Gas Turbines Power 135(12), 124501 (Sep 20, 2013) (4 pages) Paper No: GTP-12-1348; doi: 10.1115/1.4025260 History: Received September 04, 2012; Revised July 16, 2013

A supercritical steam bottoming cycle has been proposed as a performance enhancement option for gas turbine combined cycle power plants. The technology has been widely used in coal-fired steam turbine power plants since the 1950s and can be considered a mature technology. Its application to the gas-fired combined cycle systems presents unique design challenges due to the much lower gas temperatures (i.e., 650 °C at the gas turbine exhaust vis-à-vis 2000 °C in fossil fuel-fired steam boilers). Thus, the potential impact of the supercritical steam conditions is hampered to the point of economic infeasibility. This technical brief draws upon the second-law based exergy concept to rigorously quantify the performance entitlement of a supercritical high-pressure boiler section in a heat recovery steam generator utilizing the exhaust of a gas turbine to generate steam for power generation in a steam turbine.

Copyright © 2013 by ASME
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Grahic Jump Location
Fig. 1

Combined cycle bottoming cycle heat release diagram for a typical 3PRH system

Grahic Jump Location
Fig. 2

Improvement in the RBC exergetic efficiency requisite for improved CC efficiency with supplementary firing (for the GT exhaust of 638  °C (3PRH) and 553  °C (2PRH))




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