Home Physical Sciences EAF Gas Waste Heat Utilization and Discussion of the Energy Conservation and CO2 Emissions Reduction
Article Open Access

EAF Gas Waste Heat Utilization and Discussion of the Energy Conservation and CO2 Emissions Reduction

  • Ling-zhi Yang , Rong Zhu EMAIL logo and Guo-hong Ma
Published/Copyright: April 11, 2015
Download Article (PDF)
High Temperature Materials and Processes
From the journal High Temperature Materials and Processes Volume 35 Issue 2

Abstract

As a large number of energy was taken away by the high temperature furnace gas during the EAF smelting process, a huge economic and environmental benefits would obtained to recycle and utilize. In this paper, the energy of the EAF was analyzed theoretically with the hot metal ratio of 50%. Combined with the utilization of the gas waste heat during the scrap preheating, electricity generation, production of steam and production of coal gas processes, the effect of the energy saving and emission was calculated with comprehensive utilization of the high temperature furnace gas. An optimal scheme for utilization of the waste heat was proposed based on the calculation. The results show that the best way for energy saving and carbon reduction is the production of coal gas, while the optimal scheme for waste heat utilization is combined the production of coal gas with the scrap preheating, which will save 170 kWh/t of energy and decrease 57.88 kg/t of carbon emission. As hot metal ratio in EAF steelmaking is often more than 50%, which will produce more EAF gas waste heat, optimizing EAF gas waste heat utilization will have more obvious effect on energy saving and emission reduction.

Keywords: electric arc furnace; waste heat recovery; furnace gas; energy saving; CO2 emissions reduction

Introduction

With global warming becoming increasingly serious, governments and industries have attached greater importance to the reduction of greenhouse gas emissions. Modern iron and steel plants focus on “2 high and 2 low” in the production process, that is, high-efficiency process, high value of steel, low emissions of CO2, low dependence on fossil fuels [1, 2]. There are many works to study on energy saving and CO2 emissions reduction for steel mills.

Metallurgical workers have already made a mass of work in the optimization of oxygen and electric supply, improvement of EAF composition control to save energy and reduce CO2 emissions during EAF steelmaking process. Nowadays, with changes in the structure of material in the electric arc furnace, the EAF waste heat increases and EAF waste heat utilization has become the main research object of EAF energy saving and emission reduction [3–7].

The most common hot metal ratio is 30–60% during the EAF steelmaking process for the serious shortage of scrap in our country. With the increase of hot metal ratio and the application of carbon oxygen lance, the furnace gas in EAF increased dramatically. A lot of energy, about 15% of the total EAF energy and sometimes as high as 30% or above, was taken away by the high temperature furnace gas, which has great potential for energy conservation and emissions reduction. Therefore, effective utilization of the EAF high temperature furnace gas will produce great economic and environmental benefits [8–11]. The article focuses on the current situation of EAF gas waste heat utilization, so as to find a reasonable way to make full use of the EAF gas waste heat.

Analysis of the energy condition in EAF

Cold scrap is the main raw material of traditional EAF steelmaking. However, more and more hot metal is used during the EAF steelmaking process in recent years. With the increase of hot metal ratio and oxygen supply intensity as well as the application of carbon oxygen lance, the smelting intensity is increased significantly, and the structure of EAF steelmaking changes as well.

  1. The smelting efficiency is improved obviously, as the supply of physical and chemical heat is greatly increased to reduce the electric energy supply in EAF steelmaking.

  2. The increase of hot metal results in the increase of the furnace gas, the physical and chemical heat taken away by the gas increases as well.

In this paper, the energy balance in the EAF is analyzed with the hot metal ratio of 50%, the utilization of furnace gas waste heat and the effect of energy saving and CO2 emissions reduction was analyzed. The following analysis of the energy budget is on the basis of tons of steel.

The items of energy input in EAF

The input energy in EAF includes physical heat of the hot metal, chemical reaction heat, electric energy and potential chemical heat.

The solid specific heat of pig iron and liquid specific heat of hot metal is 0.745 kJ/kg°C and 0.837 KJ/kg°C, respectively, the latent heat of fusion of the hot metal is 218 kJ/kg. Then the physical heat of 550 kg hot metal is calculated, that is 181 kWh. About 170 kWh in average is supplied by the electric energy during the EAF melting.

Vast potential chemical heat is contained in CO, the incomplete combustion product, which is up to 134 kWh. Reaction heat in the EAF, the average of which is 253 kWh, mainly includes chemical heat released by oxidation of the metal and combustion of other auxiliary fuel.

The items of energy output in EAF

The output energy in EAF consists of chemical and physical heat of the furnace gas, physical heat of the slag, physical heat of the molten steel, heat taken away by the cooling water and so on.

Chemical heat of the furnace gas is the energy contained in CO, a constituent of the incomplete combustion furnace gas after decarburization reaction, which is the same as the potential chemical heat (134 kWh).

Physical heat of the furnace gas in EAF is the energy taken away by the high temperature gas. Given the quantity (200–400 Nm3), the temperature (1200°C), and the specific heat (1.137 KJ/kg°C) of the furnace gas, physical heat is obtained and the value is 140 kWh. Similarly, physical heat of the slag and molten steel is calculated, which is 43 and 397 kWh, respectively. The heat taken away by the cooling water and other output heat is about 24 kWh.

Above all, the energy budget in the EAF can be described as the schematic shown in Figure 1. It is easy to find that all of the output energy in EAF except physical heat of the molten steel can be recycled, that is 341 kWh. The chemical and physical heat of furnace gas accounts for a major portion (274 kWh) of the waste–heat utilization.

Figure 1: Energy balance during the steelmaking process in the EAF with 50% hot metal ratio.
Figure 1:

Energy balance during the steelmaking process in the EAF with 50% hot metal ratio.

Ways of EAF gas waste heat utilization

High temperature furnace gas contains huge physical and chemical heat that can be recycled. Actual utilization of the EAF gas waste heat is analyzed as the following.

Scrap preheating

Scrap preheating is the way that raises the temperature of steel scrap by the exchange of heat between the high temperature furnace gas and cold scrap before entering to the electric arc furnace. About 140 kWh of energy can be recycled theoretically during this process.

Statistics suggest that the temperature of the cold scrap can be heated to 400–600℃ by the high temperature furnace gas. And the electric energy will decrease 15 kWh per 100°C increment of the scrap temperature per ton steel. Thus about 75 kWh of electric energy in average will be saved per ton steel by using the high temperature furnace gas to preheat the steel scrap.

Electricity generation

Electricity generation is the way that physical heat of the furnace gas is converted to electric energy by the electricity generation device. 140 kWh of energy can be converted to electric energy in theory.

In fact, about 91 kWh of energy in average per ton steel is saved by generating the electricity in certain EAF steel plant of the country which can produce 57.60 × 106 kWh of electrical energy of two electric arc furnaces with capacity of 150 tons yearly [12].

Steam production

Steam production is the way to provide high temperature steam by exchange of the heat between high temperature furnace gas and cold water, during which the physical heat of furnace gas is recycled. Recyclable energy of steam production is 140 kWh theoretically.

334 × 103 tons of saturated steam with 2.0 MPa, which is equivalent to the stream amount produced by 2365 t standard coal, can be obtained annually by recycling the high temperature furnace gas discharged from the EAF with capacity of 100 tons. Thus 24 kWh of energy can be saved per ton steel during actual EAF production process [13].

Coal gas production

In early EAF steelmaking, steel scrap is the main raw material, coal gas is not recycled. Nowadays the raw materials of the EAF and the BOF are similar, content of CO in the gas released by EAF has increased, and the coal gas can be recycled for EAF. Recycling of coal gas is mainly to use the chemical heat of furnace gas, and 134 kWh of energy can be saved theoretically.

Discussion

Energy efficiency analysis

In order to analyze energy efficiency of EAF gas waste heat utilization, theoretical assumptions are made as follows:

  1. The hot metal is 550 kg, reaction heat in the EAF is 253 kWh, electric energy in average is about 170 kWh, and potential chemical heat contained in CO is 134 kWh.

  2. The quantity of the furnace gas in EAF is 200–400 Nm3, the temperature of the furnace gas is 1200°C, physical heat of the slag and molten steel is 43 kWh and 397 kWh, respectively, and the heat taken away by the cooling water and other output heat is about 24 kWh.

In conclusion, statistics of four kinds of the EAF gas waste heat utilization as are shown in Table 1.

Table 1:

Contrast of the four kinds of utilization of furnace gas waste heat.

WaysScrap preheatingElectricity generationSteam productionCoal gas production
Object of energy recoveryPhysical heatPhysical heatPhysical heatChemical heat
Theoretical energy saving (kWh/t)140140140134
Actual energy saving (kWh/t)75912495
Recovery efficiency (%)53.5765.0017.1470.90

According to the analysis of the above four ways of waste heat utilization in the EAF, the following conclusions can be obtained: scrap preheating and steam production can save 75 and 24 kWh/t of energy, respectively; electricity generation saves energy as 91 kWh/t, which is better than the former two for gas waste heat utilization; coal gas production saves 95 kWh/t of energy, which is the best way to recycle the gas waste heat.

Discussion of waste heat utilization

After analyzing the energy saving effect of the furnace gas waste heat utilization, different system boundaries are established to analyze the change of material and energy in the four ways of gas waste heat utilization. The processes of gas waste heat utilization are regard as the boundaries, then the high temperature furnace gas enters the boundary, the rest of the furnace gas and the products of gas waste heat utilization leave away from the boundary. System boundaries of gas waste heat utilization are shown in Figures 2–5 [14].

Figure 2: System boundaries of scrap preheating for EAF gas waste heat utilization.
Figure 2:

System boundaries of scrap preheating for EAF gas waste heat utilization.

Figure 3: System boundaries of electricity generation for EAF gas waste heat utilization.
Figure 3:

System boundaries of electricity generation for EAF gas waste heat utilization.

Figure 4: System boundaries of steam production for EAF gas waste heat utilization.
Figure 4:

System boundaries of steam production for EAF gas waste heat utilization.

Figure 5: System boundaries of coal gas production for EAF gas waste heat utilization.
Figure 5:

System boundaries of coal gas production for EAF gas waste heat utilization.

Scrap preheating and coal gas production are effective ways for gas waste heat utilization. An integrated optimization way (Figure 6) was proposed to improve the efficiency of recycling in this paper, which integrates scrap preheating (recycling physical heat of high temperature furnace gas) and coal gas production (recycling chemical heat of high temperature furnace gas). The optimization way can recycle 170 kWh of energy.

Figure 6: System boundaries of the integration scheme of EAF gas waste heat utilization.
Figure 6:

System boundaries of the integration scheme of EAF gas waste heat utilization.

Discussion of carbon emissions

CO2 as a major greenhouse gas has been attached great importance to the whole society due to the huge emissions. Steel industry as one of the heaviest carbon dioxide emitters is facing problems, such as poor energy efficiency, high pollution and carbon emissions. Therefore, the effects of CO2 emission reduction also need to be analyzed.

Carbon emission is a collective name or abbreviation of greenhouse gas emissions. CO2 is one of the main greenhouse gases. Emission factor is the discharge of CO2 of raw materials or products per unit mass. First, coefficient of interface between each working procedure needs to be calculated. And the total products are calculated based on the defined system boundaries. Then the total CO2 emissions of the system are got [15–17]. The results are converted to values on the basis of tons of steel. Carbon emissions are calculated on the basis of energy of the standard coal as shown in eq. (1) [2].

(1)MCarbon = MScoal×EFScoal
MCarbon, Carbon emissions of material or energy; MScoal, The equivalent value of standard coal converted by the material or energy; EFScoal, Carbon footprint of standard coal.

Calorific value of standard coal is 7,000 kcal/kg (1 CAL = 4.1868 J). It can be expressed in terms of the international system units based on eq. (2),

(2)QScoal=7,000 kcal/kg=7000×4.1868 kJ/kg=29.307 MJ/kg

According to the IPCC database, carbon content of standard coal such as lignite is 25.8 kg/GJ. Carbon emission factor of standard coal is calculated as shown in eq. (3):

(3)EFScoal=4412CScoal×QScoal=2.772 kg/kg

According to the results of energy conservation condition of furnace gas waste heat utilization in the chapter 4.2, effects of carbon emission reduction (the energy is converted to standard coal, and then the carbon emissions of standard coal are calculated) are calculated as follows:

  1. Calculation for carbon emissions of scrap preheating

    (4)MCarbonPreheat=MScoalPreheat×EFScoal=9.21 kg/t×2.772 kg/kg=25.54 kg/t

  2. Calculation for carbon emissions of electricity generation

    (5)MCarbonElectric=MScoalElectric×EFScoal=11.18 kg/t×2.772 kg/kg=30.99 kg/t

  3. Calculation for carbon emissions of steam production

    (6)MCarbonSteam=MScoalSteam×EFScoal=2.95 kg/t×2.772 kg/kg=8.17 kg/t

  4. Calculation for carbon emissions of coal gas production

    (7)MCarbonGas=MScoalGas×EFScoal=11.67 kg/t×2.772 kg/kg=32.35 kg/t

  5. Calculation for carbon emissions of the integration way

    (8)MCarbonIntegration=MScoalIntegration×EFScoal=20.88 kg/t×2.772 kg/kg=57.88 kg/t
According to the above calculation, effect of energy saving and emission reduction is summarized in Table 2.

Table 2:

The effect of energy saving and emission reduction for EAF gas waste heat utilization.

WaysScrap preheatingElectricity generationSteam productionCoal gas productionIntegrated way
Actual energy saving75.0091.0024.0095.00170.00
Theoretical energy saving(kWh/t)140.00140.00140.00134.00274.00
The energy recovery efficiency(%)53.5765.0017.1470.9062.04
Standard coal saved(kg/t)9.2111.182.9511.6720.88
Carbon emissions (kg/t)25.5430.998.1732.3557.88

25.54 kg/t, 30.99 kg/t, 8.17 kg/t and 32.35 kg/t of carbon emissions were reduced during the scrap preheating, electricity generation, steam production and coal gas production process, respectively.

In order to improve the utilization efficiency of the physical and chemical heat of high temperature furnace gas in EAF, integrated optimization way (integration of scrap preheat and coal gas production) for EAF waste heat utilization has been proposed, which saves 170 kWh/t of energy, and reduces 57.88 kg/t of carbon emissions.

The integrated optimization way for EAF gas waste heat utilization will save 510 × 106 kWh of energy and reduce 173.6×106 kg of carbon emissions every year in the EAF plant whose annual output amounts to 3 million tons.

EAF gas waste heat utilization was analyzed as the hot metal ratio is 50% in this paper. However, hot metal ratio in EAF steelmaking is often more than 50%, which will produce more EAF gas waste heat. And optimizing EAF gas waste heat utilization will have more obvious effect on energy saving and emission reduction.

Conclusion

  1. The chemical and physical heat of furnace gas is the major portion (274 kWh) of the waste–heat utilization in the EAF with the hot metal ratio of 50%.

  2. The energy saves 75 kWh/t, 24 kWh/t, 91 kWh/t and 95 kWh/t and CO2 emission reduces 25.54 kg/t, 30.99 kg/t, 8.17 kg/t and 32.35 kg/t during the scrap preheating, electricity generation, steam production and coal gas production process, respectively. Coal gas production is the most effective way for energy saving and emission reduction.

  3. Integration of the preheating scrap and production of coal gas for EAF waste heat utilization has been proposed, which saves 170 kWh/t of energy, and reduces 57.88 kg/t of carbon emissions.

  4. Optimizing EAF gas waste heat utilization will have more obvious effect on energy saving and emission reduction when the hot metal ratio is higher than 50%.

Funding statement: Funding: National Natural Science Foundation of China (No. 51334001).

Acknowledgments

The authors wish to thank the National Natural Science Foundation of China (No. 51334001) and National Key Technology R&D Program of the 12th five-year plan (No. 2012BAC27B01) for the financial support to carry out on this research.

References

[1] J.X.Fu, C.Zhang, W.S.Hwang, Int. J. Greenhouse Gas Control, 6 (2012) 143–149.10.1016/j.ijggc.2012.02.012Search in Google Scholar

[2] J.X.Fu, G.H.Tang, R.J.Zhao, J. Iron. Steel Res.,26 (2014) 275–281.10.1016/S1006-706X(14)60042-XSearch in Google Scholar

[3] R.Y.Yin, ISES’03 Proc. Iron Steel, 38 (2003) 1–12.Search in Google Scholar

[4] PaykanSafe, SamMatson, RickFranco, SEAISI Q, 36 (2007) 56–65.Search in Google Scholar

[5] SundayAbraham, S.J.Chen. Iron Steel Technol., 5 (2008) 32–40.Search in Google Scholar

[6] Y.Li, L.Zhu, Appl. Energy, 130 (2014) 603–616.10.1016/j.apenergy.2014.04.014Search in Google Scholar

[7] L.Z.Yang, R.Zhu, K.Dong, Adv. Mater. Res., 881–883 (2014) 1540–1544.10.4028/www.scientific.net/AMR.881-883.1540Search in Google Scholar

[8] H.F.Wang, C.X.Zhang, C.Q.Hu, J. Iron Steel Res., 20 (2008) 1–4.Search in Google Scholar

[9] Y.Yang, L.Liu, F.H.Feng, J. Iron Steel Res., 24 (2012) 5–9.Search in Google Scholar

[10] X.Y.Deng, J.C.Ma, W.J.Zhao, J. Iron Steel Res., 25 (2013) 14–18.Search in Google Scholar

[11] M.D.Zheng, W.F.Yan, J. Iron Steel Res., 13 (2001) 61–64.Search in Google Scholar

[12] L.B.He, Ind. Furnace, 35 (2013) 16–17 (Chinese).Search in Google Scholar

[13] B.Yang, S.X.Shen, F.R.Wang, Gongye Guolu, 27 (2011) 20–22 (Chinese).Search in Google Scholar

[14] C.Q.Hu, C.X.Zhang, X.X.Zhang, J. Iron Steel Res., 19 (2007) 16–20.Search in Google Scholar

[15] Sandeep G.Kotakar, Ravindra R.Navthar,Appl. Mech. Mater., 110–116 (2012) 2049–2053.Search in Google Scholar

[16] BetteHileman,Chem. Eng. News, 81 (2003) 16.Search in Google Scholar

[17] J.J.Wang, L.Li, Adv. Mater. Res., 869–870 (2014) 636–683.Search in Google Scholar

Received: 2014-10-13
Accepted: 2015-1-27
Published Online: 2015-4-11
Published in Print: 2016-2-1

©2016 by De Gruyter

This article is distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Articles in the same Issue

  1. Frontmatter
  3. Numerical Simulation to Study the Effect of Arc Travelling Speed and Welding Sequences on Residual Stresses in Welded Sections of New Ferritic P92 Pipes
  4. Microstructural Evolution and Compressive Properties of Two-Phase Nb-Fe Alloys Containing the C14 Laves Phase NbFe2 Intermetallic Compound
  5. Optimization of Microwave Roasting for Dechlorination of CuCl Residue under Oxygen-Enriched Condition
  6. Evaluation of High Temperature Properties and Microstructural Characterization of Resistance Spot Welded Steel Lap Shear Joints
  7. Microstructural Changes of a Creep-Damaged Nickel-Based K002 Superalloy Containing Hf Element under Different HIP Temperatures
  8. Effect of Ultrasonic Treatment on the Solidification Microstructure of GCr15 Bearing Steel
  9. Effects of Ultrasonic Treatment on Microstructure and Properties of Al-Based Composites Reinforced by In Situ Al2O3 Nanoparticles
  10. High-Temperature Oxidation Behavior of Fe-Si-Ce Alloys
  11. Reaction Mechanism of Siderite Lump in Coal-Based Direct Reduction
  12. EAF Gas Waste Heat Utilization and Discussion of the Energy Conservation and CO2 Emissions Reduction
  13. Numerical Parametric Analysis of Bond Coat Thickness Effect on Residual Stresses in Zirconia-Based Thermal Barrier Coatings
  14. The Marker Conservation Law in Multiphase Systems
  15. Synthesis and Characterization of Strontium Carbonate Nanostructures via Simple Hydrothermal Method
https://doi.org/10.1515/htmp-2014-0183
Keywords for this article
electric arc furnace; waste heat recovery; furnace gas; energy saving; CO2 emissions reduction
Creative Commons
BY-NC-ND 3.0

Articles in the same Issue

  1. Frontmatter
  3. Numerical Simulation to Study the Effect of Arc Travelling Speed and Welding Sequences on Residual Stresses in Welded Sections of New Ferritic P92 Pipes
  4. Microstructural Evolution and Compressive Properties of Two-Phase Nb-Fe Alloys Containing the C14 Laves Phase NbFe2 Intermetallic Compound
  5. Optimization of Microwave Roasting for Dechlorination of CuCl Residue under Oxygen-Enriched Condition
  6. Evaluation of High Temperature Properties and Microstructural Characterization of Resistance Spot Welded Steel Lap Shear Joints
  7. Microstructural Changes of a Creep-Damaged Nickel-Based K002 Superalloy Containing Hf Element under Different HIP Temperatures
  8. Effect of Ultrasonic Treatment on the Solidification Microstructure of GCr15 Bearing Steel
  9. Effects of Ultrasonic Treatment on Microstructure and Properties of Al-Based Composites Reinforced by In Situ Al2O3 Nanoparticles
  10. High-Temperature Oxidation Behavior of Fe-Si-Ce Alloys
  11. Reaction Mechanism of Siderite Lump in Coal-Based Direct Reduction
  12. EAF Gas Waste Heat Utilization and Discussion of the Energy Conservation and CO2 Emissions Reduction
  13. Numerical Parametric Analysis of Bond Coat Thickness Effect on Residual Stresses in Zirconia-Based Thermal Barrier Coatings
  14. The Marker Conservation Law in Multiphase Systems
  15. Synthesis and Characterization of Strontium Carbonate Nanostructures via Simple Hydrothermal Method
Sign up now to receive a 20% welcome discount
Institutional Access
How does access work?
Have an idea on how to improve our website?
Please write us.
© 2026 De Gruyter Brill
Downloaded on 1.3.2026 from https://www.degruyterbrill.com/document/doi/10.1515/htmp-2014-0183/html
Scroll to top button