Energy and Economic Optimization of Regenerative Organic Rankine Cycle with in Energy Recovery System of a Steel Plant

Davood  Atashbozorg ¹ ( Department of Energy system Engineering, NT.C., Islamic Azad University, Tehran, Iran )
Afshin  Mohseni Arasteh ² ( Department of Physical oceanography. NT.C., Islamic Azad University, Tehran Iran )
Gholamreza Salehi ³ ( Department of Mechanical Engineering, CT.B., Islamic Azad University, Tehran, Iran )
Masoud  Torabi Azad ⁴ ( Department of Physical oceanography. NT.C., Islamic Azad University, Tehran Iran )

Submited date : 2025-05-15 Accepted date : 2025-06-09

Keywords: Energy recovery, Organic Rankine Cycle, Regenerative, Steel Plant, Optimization, NSGAII,

Abstract :

This paper is to provide the design, analysis, and optimization of regenerative ORC for the waste heat recovery in a steel-works facility. A feedwater heater is installed in the system to further increase thermal efficiency. The system is examined by energy, exergy, and thermos-economic approaches. To achieve the highest performances, the selection of various parameters is carried out by using NSGA-II optimizing both exergy efficiency and total annual cost at the same time. The software MATLAB interface with REFPROP library is used for modeling and design variables include turbine inlet pressure, superheat temperature difference, condenser pressure, and the isentropic efficiencies of the rotating components. Thus, it has been shown that a proper tuning of some of these parameters may bring a satisfactory compromise between thermodynamic and economic performance. The optimum design gave a maximum exergy efficiency of 64.88%, an energy efficiency of 38.23%, a net power output of 1756.2 kW, and an estimated annual cost of $14.88 million. These results suggest that optimization of ORC systems could be a viable and practical solution for better energy utilization in heavy industries.

References:

Lan, Y., Wang, S., Lu, J., Zhai, H., & Mu, L. (2022). Comparative analysis of Organic Rankine Cycle, Kalina Cycle and Thermoelectric Generator to recover waste heat based on energy, economic and environmental analysis method. Energy, 254, 124158. https://doi.org/10.1016/j.energy.2022.124158
Elahi, A. E., Mahmud, T., Alam, M., & Biswas, B. N. (2022). Exergy Analysis of Organic Rankine Cycle for Waste Heat Recovery Using Low GWP Refrigerants. Energy Reports, 8, 2976–2985. https://doi.org/10.1016/j.egyr.2022.01.034
Atashbozorg, D., Arasteh, A. M., Salehi, G., & Azad, M. T. (2022). Analysis of Different Organic Rankine and Kalina Cycles for Waste Heat Recovery in the Iron and Steel Industry. ACS Omega, 7(50), 46099–46109. https://doi.org/10.1021/acsomega.2c03922
Lan, S., et al. (2023). Fuel saving potential analysis of bifunctional vehicular waste heat recovery system using thermoelectric generator and organic Rankine cycle. Heliyon, 9(4), e05118. https://doi.org/10.1016/j.heliyon.2023.e05118
Kaşka, Ö. (2013). Energy and exergy analysis of an organic Rankine for power generation from waste heat recovery in steel industry. Energy Conversion and Management, 77, 108–117. https://doi.org/10.1016/j.enconman.2013.09.019
Chen, H., et al. (2022). Energy, exergy, sustainability, and economic analysis of a waste heat recovery system using organic Rankine cycle and Kalina cycle. Energy Conversion and Management, 254, 115245. https://doi.org/10.1016/j.enconman.2022.115245
Fergani, Z., & Morosuk, T. (2023). Advanced exergy-based analysis of an organic Rankine cycle (ORC) for waste heat recovery. Entropy, 25(10), 1345. https://doi.org/10.3390/e25101345
Sohrabi, M., et al. (2023). A comparative thermodynamic analysis of ORC and Kalina cycles for waste heat recovery: A case study for CGAM cogeneration system. Case Studies in Thermal Engineering, 38, 102347. https://doi.org/10.1016/j.csite.2023.102347
Behzadi, A., & Behbahaninia, A. (2021). Multi-objective optimization and exergoeconomic analysis of waste heat recovery from Tehran’s waste-to-energy plant integrated with an ORC unit. Energy, 160, 1055–1068. https://doi.org/10.1016/j.energy.2018.10.190
Nemati, A., et al. (2017). Comparative exergy analysis of organic Rankine and Kalina cycles in a CGAM system. Energy Procedia, 129, 292–298. https://doi.org/10.1016/j.egypro.2017.09.151
Lawan, S.M. and W.A.W.Z. Abidin, A review of hybrid renewable energy systems based on wind and solar energy: modeling, design and optimization. Wind Solar Hybrid Renewable Energy System, 2020.
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Hajabdollahi, H., A. Saleh, and M. Shafiey Dehaj, A multi-generation system based on geothermal driven: energy, exergy, economic and exergoenvironmental (4E) analysis for combined power, freshwater, hydrogen, oxygen, and heating production. Environment, Development and Sustainability, 2023: p. 1-33.

Full-Text:



 

Research Article

Energy and Economic Optimization of Regenerative Organic Rankine Cycle with in Energy Recovery System of a Steel Plant

 

Davood Atashbozorg1

Afshin Mohseni Arasteh2

Gholamreza Salehi3

Masoud Torabi Azad4

 

1.       Department of Energy system Engineering, NT.C., Islamic Azad University, Tehran, Iran, Email: [e-mail]

2.       Department of Physical oceanography. NT.C., Islamic Azad University, Tehran Iran, Email: [e-mail]

3.       Department of Mechanical Engineering, CT.B., Islamic Azad University, Tehran, Iran, Email: [e-mail] (Correspond Author)

4.       Department of Physical oceanography. NT.C., Islamic Azad University, Tehran Iran, Email: [e-mail]

 

ABSTRACT

DOI: https://doi.org/10.71584/MGMT.2025.1206908
Abstract: This paper is to provide the design, analysis, and optimization of regenerative ORC for the waste heat recovery in a steel-works facility. A feedwater heater is installed in the system to further increase thermal efficiency. The system is examined by energy, exergy, and thermos-economic approaches. To achieve the highest performances, the selection of various parameters is carried out by using NSGA-II optimizing both exergy efficiency and total annual cost at the same time. The software MATLAB interface with REFPROP library is used for modeling and design variables include turbine inlet pressure, superheat temperature difference, condenser pressure, and the isentropic efficiencies of the rotating components. Thus, it has been shown that a proper tuning of some of these parameters may bring a satisfactory compromise between thermodynamic and economic performance. The optimum design gave a maximum exergy efficiency of 64.88%, an energy efficiency of 38.23%, a net power output of 1756.2 kW, and an estimated annual cost of $14.88 million. These results suggest that optimization of ORC systems could be a viable and practical solution for better energy utilization in heavy industries. Keywords: Energy recovery, Organic Rankine Cycle, Regenerative, Steel Plant, Optimization, NSGAII	Article Info:
	Received Date: 2025/05/15 Accepted Date: 2025/06/09   Published Online: 2025/07/14

 

How to Cite: Atashbozorg,D, et. al,(2025).Energy and Economic Optimization of Regenerative Organic Rankine Cycle with in Energy Recovery System of a Steel Plant. Journal of Industrial Strategic Management, 9(1): 23-39.

1.       Introduction

Waste heat recovery in steel production via new thermodynamic cycles such as the Organic Rankine Cycle (ORC), Kalina Cycle (KC), and thermoelectric generators (TEG) has been of great interest in recent years. For the work done by Elahi et al., ORC performance for waste heat recovery was compared based on low Global Warming Potential (GWP) working fluids such as R1233zd(E). By a thermodynamic exergy-based approach, the authors demonstrated that the use of these environmentally friendly fluids would have a significant effect on exergy efficiency and reduce environmental harm (Elahi et al., 2022).

Lan et al. conducted comparative assessment of ORC, KC, and TEG technologies for steel industry waste heat recovery at temperatures from 50–200°C. They utilized energy, exergy, economic, and environmental assessment with the EES program and concluded that ORC and KC are significantly superior to TEG for temperatures above 100°C (Lan et al., 2022).

Atashbozorg et al. also analyzed the hot rolling and electric arc furnace parts of a steel plant in another study. They modeled ORC and KC systems by thermodynamic simulation and exergy-economic assessment. According to their findings, Kalina KCS34 cycle had a higher performance both in terms of exergy efficiency and cost-profit ratio (Atashbozorg et al., 2022).

Lan et al. also investigated the integration of TEG and ORC systems in a two-stage heat recovery system for industrial vehicles. Based on their studies, they were able to establish that the hybrid configuration improved fuel saving and efficiency in electricity generation, including low-temperature operating conditions (Lan et al., 2023).

Kaşka did a real-world exergy and energy analysis for an ORC system for power generation from flue gases within a Turkish steel factory. Using actual operating conditions, the study recognized major exergy loss areas, primarily in the evaporator and recommended improvement strategies (Kaşka, 2013).

Chen et al. conducted an extensive comparison of ORC and Kalina cycles in a waste heat recovery setting. They utilized MATLAB modeling for comparing energy, exergy, sustainability, and economical parameters. The results identified that combining the two cycles would enhance overall system efficiency (Chen et al., 2022).

Fergani and Morosuk applied an exergy-based analysis method to an ORC system for industrial waste heat recovery. They separated avoidable and unavoidable exergy losses through components and thereby identified potential areas of substantial thermodynamic improvement (Fergani & Morosuk, 2023).

Sohrabi et al. also compared Kalina cycle and ORC in a Combined Generation of Electricity, Heating and Cooling (CGAM) system. Thermodynamic modeling using MATLAB revealed that at some operating conditions, ORC was more efficient than the Kalina cycle (Sohrabi et al., 2023).

Behzadi and Behbahaninia developed a multi-objective optimization model for an ORC waste-to-energy facility in Tehran. Their work used exergy-economic analysis and illustrated the immense improvement both exergy and economic efficiency can attain with the proper selection of working fluid and optimization parameters (Behzadi & Behbahaninia, 2021).

Lastly, Nemati et al. also conducted a comparative exergy analysis of Kalina and ORC cycles with a CGAM configuration. Based on their simulations by employing Engineering Equation Solver (EES), ORC performed better under part load and normal industrial operating conditions (Nemati et al., 2017).

These researches in total illustrate the increasing importance of exergy analysis as a tool for optimizing waste heat recovery in the steel industry and call for the fact that recovery cycles should be chosen based on heat source properties, system complexity, and environmental objectives.

By examining the research background, it can be seen that in past research, various cycles such as Rankine Organic and Kalina types have been studied. Most of the research has examined the thermodynamic and economic or simultaneous aspects of these cycles. However, in the research background, the Rankine organic cycle with a turbine exhaust has not been subjected to dual-objective optimization, and thermo-economic and exergy analysis as two objective functions have not been studied in it.

 

2.       Cycle description

Power generation and conversion of thermal energy into electrical energy were carried out in power generation cycles of power plants. In recent years, cycles have been introduced that can convert waste heat from sources such as furnaces into power. In an industry such as steel, these waste energy sources are high and for this reason they are classified as energy-intensive industries. The energy system used in the present study includes the organic Rankine and power generation cycles. Their operation is presented in order below. The organic Rankine cycle (ORC) is an energy system that is used to generate electricity from low-temperature thermal sources, making it particularly suitable for applications such as waste heat recovery, renewable energies such as geothermal energy and solar thermal energy. The organic Rankine cycle has the same function as the conventional Rankine cycle (steam power plant), except that it uses an organic working fluid instead of water [4]. The main components of a simple Rankine cycle include an evaporator, organic turbine, condenser and a pump. In addition, in the present work, a feed water heater has been added to increase the cycle efficiency. The organic Rankine cycle schematic of the present work is shown in Figure 1

 

.

Figure 1. ORC cycle in study

 

First, the organic fluid, upon receiving heat in the evaporator, exits with the thermodynamic characteristics of flow 1 and enters the turbine to produce power. After its expansion, it leaves the turbine with the characteristics of flow 2. It should be noted that a part of the working fluid flow enters the feedwater heater as a sub cooler from the turbine. The working fluid appears in a condensed liquid state in flow 3 after passing through the condenser. In the next step, by pump 2, the working fluid pressure at point 4a is increased to the feedwater heater pressure. Then, its temperature is increased by the feedwater heater and it leaves it in flow conditions 3c1a until its pressure is increased by pump 1 to the working pressure of the cycle. This cycle is repeated to produce power.

 

3.       Thermodynamic Modeling and Analysis

3-1. Mass and energy balance

The main energy and mass equations used in the analysis of the first law of thermodynamics for the control volume are given in equations (1) and (2):

ORC systems generally consist of five main components: evaporator, turbine, condenser, pump, and feed heater. In this section, we will describe and analyze the mass and energy equations for each component. By solving these equations, the first law of thermodynamics efficiency can be obtained.

Relations (3) to (5) are the turbine mass and energy equations:

(1)
(2)

Equations (6) and (7) are the mass and energy equations for the condenser, respectively:

(3)
(4)
(5)

Pump mass and energy equations:

(6)
(7)

Mass and energy equations of the evaporator:

(8)
(9)
(10)

Feed heater mass equation:

(11)
(12)
(13)

The mass fraction going to SRORC power supply can be expressed as follows:

(14)
(15)

The thermodynamic efficiency of the first law is known as thermal efficiency. To calculate the thermal efficiency of the cycle, we must calculate the power output and the heat input to the system. The thermal efficiency equation of the system is calculated from equation:

(16)

Where Wnet is obtained from equation 18:

(17)

 

3-2. Exergy balance

The exergy loss equations for each component of the system are written below:

 

(18)

 

3-3. Exergy efficiency

Based on the second law of thermodynamics, the exergy efficiency of systems can be calculated using the following equation:

	evaporator	(19)
	Condenser	(20)
	Pump	(21)
	Turbine	(22)
	Feed heater	(23)
	Internal HX	(24)
	Separator	(25)
	Expansion valve	(26)
	mixer	(27)

T0 is the ambient temperature and Tm is the average temperature of the heat source, which can be calculated as follows:

(28)

Analyzing different systems from a thermodynamic perspective does not necessarily imply that a system with higher efficiency is the best system in terms of cost. In order to examine systems with thermodynamic and economic factors simultaneously, the concept of thermo-economics has been defined. Thermo-economics combines empirical principles and economic analysis at the level of system components. Various methods for thermo-economic analysis have been proposed, including exergy cost theory, average cost approach, and specific exergy cost (SPECO). For the analysis of energy conversion systems, the SPECO method provides a simple scheme and increases the calculation time by using a matrix formula. Therefore, the specific exergy cost (SPECO) method was used in this study.

 

3-4. Cost equation

Thermo-economics relies on the concept that exergy is the only rational basis for allocating costs to the interactions that a thermal system exchanges with its surroundings and is a source of inefficiency within it. Thus, for the input and output material flows with exergy transfer rates (exergy flows) and the power and the exergy transfer rate associated with heat transfer, we write:

(29)

Here, ci, ce, cw, and cq denote the average unit costs of each component, and I, e, w, and q are the cost streams associated with the waste streams. Exergy costing involves cost balances formulated separately for each component of the system. The cost balance applied to the component shows that the sum of the cost rates associated with all available exergy streams is equal to the sum of the input cost rates to all exergy streams plus the appropriate costs (cost rates) resulting from investment and operation and maintenance costs. The sum of the last two terms is denoted by . Accordingly, for an example of a reversible component that receives a heat transfer and produces power, we write:

(30)	i=cii
(31)	e=cee
(32)	w=cww
(33)	q=cqq

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