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research-article

Combined Pinch and Exergy Evaluation for Fault Analysis in a Steam Power Plant Heat Exchanger Network

[+] Author and Article Information
Howard O. Njoku

Department of Mechanical Engineering University of Nigeria Nsukka, Enugu State 410001 Nigeria howard.njoku@unn.edu.ng

Linus C. Egbuhuzor

Egbin Power Plc Ijede, Lagos State 104102 Nigeria sacraeslinus@gmail.com

Mkpamdi N. Eke

Department Of Mechanical Engineering Nsukka, Enugu 410001 Nigeria mkpamdi.eke@unn.edu.ng

Samuel O. Enibe

Department of Mechanical Engineering Nsukka, Enugu state 042 Nigeria samuel.enibe@unn.edu.ng

Esther A. Akinlabi

Kingsway Campus Auckland Park Johannesburg, Gauteng 2006 South Africa etakinlabi@uj.ac.za

1Corresponding author.

Contributed by the Advanced Energy Systems Division of ASME for publication in the Journal of Energy Resources Technology. Manuscript received December 1, 2018; final manuscript received May 8, 2019; published online xx xx, xxxx. Assoc. Editor: Luis Serra.

ASME doi:10.1115/1.4043746 History: Received December 01, 2018; Accepted May 08, 2019

Abstract

This study demonstrates comparative applications of the standard pinch and exergy analysis and the combined pinch-exergy analysis methodologies to a gas-fired steam power plant's heat exchanger network. The extent to which each methodology could be used for pin-pointing the location of performance deteriorations in the network and their relative criticality were shown. Using a 12°C minimum temperature difference, the network minimum hot utility requirement in current operation was determined by a pinch analysis as 539,491 kW, at a supply temperature of 549°C. This represented a 6% (30,618 kW) increase in the utility requirement when compared with the design minimum requirement (508,873.7 kW). The combined exergy pinch analysis showed the severity of performance deteriorations more clearly, determining a 25% increase in global plant exergy losses with respect to design conditions. With a standard exergy analysis, additional information on the actual network components responsible for the changes was obtained – there were general declines in component performances except for two heaters and the deaerator, whose operation performances improved slightly. Furthermore, avoidable and inevitable exergy losses (Ξ̇d,AVO and Ξ̇d,INE, respectively) were determined for network components. Whereas both were highest for the boiler, the values of the ratio Ξ̇d,AVO / Ξ̇d,INE showed that higher potentials for performance improvement existed in the other network components. This indicates the ratio Ξ̇d,AVO / Ξ̇d,INE as an appropriate measure for deciding equipment in the heat exchanger network that are in need critical attention.

Copyright © 2019 by ASME
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