Classical and advanced exergy-based analysis of a 750 MW steam power plant

ABSTRACT

Both the conventional (classic) and advanced exergetic analytical methods were used to investigate the improvement potentials of a pulverised coal-fired 750 $MW$ supercritical steam power plant. The results show that the subsystem that contributed the most to exergy destruction is the condenser (CND) at about 1.25% and closely followed by the boiler at 1.23%. Furthermore, the data obtained from the present study show that the dominant contributor to the overall exergy destruction in each of the subsystems was the endogenous part of exergy destruction, ${\dot{E}}_{D,k}^{EN}$. In addition, the results show that steam turbines, especially TB1, TB4, TB5, TB6, TB7 to TB17, the condenser and the boiler would benefit immensely by improving their avoidable endogenous exergy destructions${\dot{E}}_{D,k}^{AV,EN}$. This investigation also shows that the overall unavoidable exergy destruction within the entire power plant was about 42.8%, while the potential for improving the entire power plant was approximately 2.5%. Other important results from this study are comprehensibly documented in the conclusion section.

KEYWORDS:

• Advanced exergetic analysis
• classic exergetic analysis
• avoidable exergy destruction
• unavoidable exergy destruction
• endogenous exergy destruction
• exogenous exergy destruction
• relaxation factor
• fuel-air equivalence ratio

Nomenclature

$\dot{E}$	=	Rate of change of exergy $\left(W\right)$
${\dot{E}}_D$	=	Rate of global exergy destruction $\left(W\right)$
$e$	=	Specific exergy $\left(kJ/kg\right)$
$h$	=	Specific enthalpy $\left(kJ/kg\right)$
$\dot{m}$	=	Mass flow rate $\left(kg/s\right)$
$n$	=	Number of subsystems
$p$	=	Pressure $\left(\mathrm{b}\mathrm{a}\mathrm{r}\right)$
$\dot{q}$	=	Rate of heat transfer $\left(W\right)$
${\dot{S}}_{gen}$	=	Rate of entropy generation $\left(kJ/kg\cdot K\cdot s\right)$
T	=	Temperature $\left(K\right)$
$y_D$	=	Exergy destruction ratio

Greek Symbol

$\mathrm{\Delta }$	=	Difference
$\epsilon$	=	Exergetic efficiency
${\eta }_s$	=	Isentropic efficiency of the pumps and turbine
${\eta }_m$	=	Mechanical efficiency of the pumps and generator
$\varphi$	=	Fuel-air equivalence ratio

Subscripts

$D$	=	Destruction
$F$	=	Fuel
$kth$	=	Plant subsystem, $k$
$P$	=	Product
$P$	=	State point of a process with unavoidable exergy destruction
$0$	=	Thermodynamic environment

Superscripts

$AV$	=	Avoidable
$EN$	=	Endogenous
$EX$	=	Exogenous
$real$	=	State point of a real process
$UN$	=	Unavoidable

Acknowlegements

The authors also wish to express their sincere gratitude to Mr Milton Venetos of EBSILON for providing answers to some questions concerning EBSILON and the reviewers for their insightful and constructive remarks, which led to improving the clarity of this paper considerably.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work reported herein was graciously supported by the Nigerian Defence Academy, Kaduna, Nigeria, Texas Southern University, Houston, Texas, USA, and Kwara State University, Ilorin, Nigeria.

Notes on contributors

Lucky Anetor

Lucky Anetor received his B.Sc. degree (First Class Honors) in Mechanical Engineering from the University of Lagos, Nigeria, M.Sc. degree in Marine/Mechanical Engineering from the University of London, United Kingdom and his PhD degree in Mechanical Engineering (With specialization in Internal Combustion Engines and Computational Fluid Dynamics) from the University of British Columbia, Vancouver, Canada. Furthermore, he obtained a Master’s degree in Mathematics from the University of Houston, Texas, USA, with a GPA of 3.973/4.0. He was the pioneer Dean, Faculty of Engineering, Nigerian Defence Academy, Kaduna, Nigeria. Dr. Anetor is presently an Adjunct Professor at Texas Southern University, Houston, Texas, USA. Prior to now, he was a former Professor of Mechanical Engineering at Kwara State University, Nigeria. Professor Anetor has also worked as an Adjunct Faculty at the ITT Technical Institute, Houston, Texas and Wharton County Junior College, Wharton, Texas, USA. He is actively engaged in research and consulting in the areas internal combustion engines and cyber-security of industrial control systems. Professor Anetor has published numerous peer reviewed academic works in local and international journals. He is a member of the Council for the Regulation of Engineering in Nigeria (COREN) and a Licensed Professional Engineer in the State of Texas, USA.

Edward E. Osakue

Dr. Edward E. Osakue is a Professor in the Department of Industrial Technology, Texas Southern University, Houston; Texas, USA with a concentration in Design Engineering and Technology. He is also graduate Faculty and the coordinator of the Design Technology concentration at the Department. Dr. Osakue joined the Faculty at Texas Southern University in 2005. He worked previously at ITT Technical Institute, Houston South campus as Education Supervisor and Program Chair for CAD Program and School of Design from 1999 to 2005. Dr. Osakue was a Faculty member in the Department of Production Engineering, University of Benin from 1984 to 1992.Dr. Osakue received his doctoral degree in mechanical engineering from the University of New Brunswick, Fredericton, Canada, in 1999. He obtained his Bachelor of Engineering degree in 1983 from the University of Benin, Benin City, Nigeria. His research interests include economical design of mechanical, structural, and piping systems, internal combustion engines, renewable energy, low-velocity impact with friction, and effective curriculum delivery methods. Dr. Osakue is a frequent attendee and presenter at National and International conferences. He is a member of several professional organizations including American Society of Mechanical Engineers (ASME) and American Society for Engineering Education (ASEE).

Christopher Odetunde

Dr. Christopher Odetunde is the Chair and Professor of Aeronautics and Astronautics Engineering Department at the Kwara State University, Malete, Kwara State, Nigeria. He was formerly a Faculty at the Department of Aviation Science and Technology, Texas Southern University, Houston, Texas, USA.  Professor Odetunde obtained his Bachelor of Science degree in Aeronautical Engineering from Embry-Riddle Aeronautical University and his Master of Science degree in Aerospace Engineering/Mechanical Engineering from Iowa State University both in the USA. Furthermore, he was bagged his Doctor of Philosophy degree in Aerospace Engineering from Texas A&M University, College Station, Texas, USA. Professor Odetunde also has a Master of Science degree in Project Management which was conferred on him by the Southeastern Institute of Technology Huntsville, Alabama, USA. Dr. Odetunde’s areas of interest include but not limited to; Thermo-fluids, Combustion, Orbital and Attitude Control, Subsonic, Aircraft structure, Transonic, Supersonic and hypersonic Aerodynamics, Aviation Safety, Unmanned Aerial Vehicle (UAV), Transportation methods and theory. Professor Odetunde is a registered engineer with the Council for the Regulation of Engineering in Nigeria (COREN). He is also a Member of Board of trustees of Aviation Accreditation International, AABI.  Dr. Odetunde has more than 35 years of aerospace/aviation experience.