Reheating furnace of an integrated steel plant consumes intensive fuel as input energy to heat up stocks prior to hot rolling process. In current scenario, the elevated cost of productivity due to increasing fuel price is emerging as a key concern for the steel industry. A continuous improvement in reduction of fuel consumption is one of the key objectives for the manufacturing units. Numerous research work is going on worldwide to increase the energy efficiency of reheating furnaces. Computational Fluid Dynamics (CFD) and numerical modelling are mostly being used for predicting thermal and reactive fluid characteristic inside a furnace. However, the said methods are very expensive and require a huge infrastructure to compute the results. In addition, these results are not available on real time basis to take corrective action due to high computational time. In this article, an alternative approach has been adopted where complete heat and mass balance of entire tunnel type reheating furnace has been carried out. This study includes first principle-based model where heat conduction, convection and radiation with combustion reactions of the fuel components have been considered. Based on these theoretical calculations, the model is used to identify heat losses at various locations of the furnace. Moreover, a method to optimize the mixing ratio of air and fuel (mixed gas) along with monitoring of heat recovery from combined recuperator have been covered. Based on the model outcome, a significant improvement in furnace efficiency has been achieved, leading to reduction in fuel consumption in the range of 12%.
References
[1]
Jang, J. and Huang, J. (2015) Optimization of a Slab Heating Pattern for Minimum Energy Consumption in a Walking-Beam Type Reheating Furnace. AppliedThermalEngineering, 85, 313-321. https://doi.org/10.1016/j.applthermaleng.2015.04.029
[2]
Zhang, C., Ishii, T. and Sugiyama, S. (1997) Numerical Modeling of the Thermal Performance of Regenerative Slab Reheat Furnaces. NumericalHeatTransfer, PartA: Applications, 32, 613-631. https://doi.org/10.1080/10407789708913909
[3]
Jong Gyu Kim, Kang Y. Huh, Il Tae K, (2000) Three-Dimensional Analysis of the Walking-Beam-Type Slab Reheating Furnace in Hot Strip Mills. NumericalHeatTransfer, PartA: Applications, 38, 589-609. https://doi.org/10.1080/104077800750021152
[4]
Huang, M., Hsieh, C., Lee, S. and Wang, C. (2008) A Coupled Numerical Study of Slab Temperature and Gas Temperature in the Walking-Beam-Type Slab Reheating Furnace. NumericalHeatTransfer, PartA: Applications, 54, 625-646. https://doi.org/10.1080/10407780802289475
[5]
Hsieh, C., Huang, M., Lee, S. and Wang, C. (2010) A Numerical Study of Skid Marks on the Slabs in a Walking-Beam Type Slab Reheating Furnace. NumericalHeatTransfer, PartA: Applications, 57, 1-17. https://doi.org/10.1080/10407780903529308
[6]
Han, S.H., Chang, D. and Kim, C.Y. (2010) A Numerical Analysis of Slab Heating Characteristics in a Walking Beam Type Reheating Furnace. InternationalJournalofHeatandMassTransfer, 53, 3855-3861. https://doi.org/10.1016/j.ijheatmasstransfer.2010.05.002
[7]
Gu, M., Chen, G., Liu, X., Wu, C. and Chu, H. (2014) Numerical Simulation of Slab Heating Process in a Regenerative Walking Beam Reheating Furnace. InternationalJournalofHeatandMassTransfer, 76, 405-410. https://doi.org/10.1016/j.ijheatmasstransfer.2014.04.061
[8]
Morgado, T., Coelho, P.J. and Talukdar, P. (2015) Assessment of Uniform Temperature Assumption in Zoning on the Numerical Simulation of a Walking Beam Reheating Furnace. AppliedThermalEngineering, 76, 496-508. https://doi.org/10.1016/j.applthermaleng.2014.11.054
[9]
Emadi, A., Saboonchi, A., Taheri, M. and Hassanpour, S. (2014) Heating Characteristics of Billet in a Walking Hearth Type Reheating Furnace. AppliedThermalEngineering, 63, 396-405. https://doi.org/10.1016/j.applthermaleng.2013.11.003
[10]
Han, S.H., Baek, S.W. and Kim, M.Y. (2009) Transient Radiative Heating Characteristics of Slabs in a Walking Beam Type Reheating Furnace. InternationalJournalofHeatandMassTransfer, 52, 1005-1011. https://doi.org/10.1016/j.ijheatmasstransfer.2008.07.030
[11]
Yang, B.Y., Wu, C.Y., Ho, C.J. and Ho, T.Y. (1995) A Heat Transfer Model for Skid Mark Formation on Slab in a Reheating Furnace. Journal of Materials Processings and Manufacturing Science, 3, 277-295.
[12]
Han, S.H. and Chang, D. (2012) Optimum Residence Time Analysis for a Walking Beam Type Reheating Furnace. InternationalJournalofHeatandMassTransfer, 55, 4079-4087. https://doi.org/10.1016/j.ijheatmasstransfer.2012.03.049
[13]
Fan, H., Feng, J., Hu, W., Li, W. and Gao, J. (2021) Effect of Excess Air Coefficient on the Combustion Characteristics of a Multi-Stage Dual Swirl Burner. JournalofPhysics: ConferenceSeries, 2009, Article ID: 012076. https://doi.org/10.1088/1742-6596/2009/1/012076
[14]
Han, S.H., Lee, Y.S., Cho, J.R. and Lee, K.H. (2018) Efficiency Analysis of Air-Fuel and Oxy-Fuel Combustion in a Reheating Furnace. InternationalJournalofHeatandMassTransfer, 121, 1364-1370. https://doi.org/10.1016/j.ijheatmasstransfer.2017.12.110
[15]
Zhang, K., Zheng, Z., Feng, L., Su, J. and Li, H. (2023) A Byproduct Gas Distribution Model for Production Users Considering Calorific Value Fluctuation and Supply Patterns in Steel Plants. AlexandriaEngineeringJournal, 76, 821-834. https://doi.org/10.1016/j.aej.2023.06.063
[16]
Kangvanskol, K. and Tangthieng, C. (2014) An Energy Analysis of a Slab Preheating Chamber for a Reheating Furnace. EngineeringJournal, 18, 1-12. https://doi.org/10.4186/ej.2014.18.2.1
[17]
Moran, M.J. and Shapiro, H.N. (2004) Reacting Mixtures and Combustion. Fundamentals of Engineering Thermodynamics, 13, 661-664.
[18]
Chakravarty, K. and Kumar, S. (2020) Increase in Energy Efficiency of a Steel Billet Reheating Furnace by Heat Balance Study and Process Improvement. EnergyReports, 6, 343-349. https://doi.org/10.1016/j.egyr.2020.01.014
[19]
Trinks, W., Mawhinney, M.H., Shannon, R.A., Reed, R.J. and Garvey, J.R. (2004) Industrial Furnaces Book with chapter Furnace, Kiln and Oven Heat Losses. 6th Edition, John Wiley & Sons, Inc. Hoboken, New Jersey, 189-191.
[20]
Steinboeck, A., Wild, D. and Kugi, A. (2013) Energy-Efficient Control of Continuous Reheating Furnaces. IFAC Proceedings Volumes, 46, 359-364.
[21]
Adeniji, T.A. and Waheed, M.A. (2021) Evaluation of the Energy Efficiency of an Aluminum Melting Furnace for a Nigerian Cast-Coiled Plant. FuelCommunications, 9, Article ID: 100027. https://doi.org/10.1016/j.jfueco.2021.100027
[22]
Seong, B.G., Hwang, S.Y. and Kim, K.Y. (2000) High-temperature Corrosion of Recuperators Used in Steel Mills. SurfaceandCoatingsTechnology, 126, 256-265. https://doi.org/10.1016/s0257-8972(00)00523-5
