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Modelling and Analysis of Oxygen Enrichment to Hot Stoves
Available online at www.sciencedirect.com
ScienceDirect Energy Procedia 105 (2017) 5128 – 5133
The 8th International Conference on Applied Energy – ICAE2016
Modelling and analysis of oxygen enrichment to hot stoves Chuan Wanga,d,*, Jonas Zetterholmb, Magnus Lundqvista, Jürgen Schlimbachc b
a Swerea MEFOS, Box 812, Luleå, 97125, Sweden Energy Science/Energy Engineering, Luleå University of Technology, Luleå, 97187, Sweden c DK Recycling und Roheisen GmbH, Werthauser Straße 182, 47053 Duisburg, Germany d Thermal and Flow Engineering Laboratory, Åbo Akademi University, Åbo, Finland
Abstract The paper presents some research work on applying the oxygen enrichment technique to hot stoves that was carried out in one European RFCS project. In the presented work, both theoretical and practical work was studied. A dynamic model was used to investigate the effects of oxygen enrichment on hot stoves’ performance under the condition that only blast furnace gas was used as the fuel gas. The modelling results showed that SOE will enhance the combustion process in hot stoves by increasing hot blast temperature and shortening the on-gas time, which were further verified by industrial trials performed at an iron-making plant. In addition, CFD modelling was performed by simulating different oxygen levels and lance positions at the burner to avoid the hot spot formation during the combustion. Keywords: Stove oxygen enrichment; Blast furnace; hot blast; dynamic model; CFD
1. Introduction For the ore based iron-making process, hot stoves are very important auxilary equipment to the blast furnace (BF), providing hot blast to the process. The blast provides thermal energy and reducing gas to the BF process through combustion of coke and injected fuel at the tuyere level. The target for hot stoves is to provide a high and stable temperature of the blast. Higher blast temperature leads to lower coke and pulverized coal/natural gas consumption in BF. Recent years, more attention has been paid on improving stoves’ performance. For instance, one hot stove project was granted by the research program EU RFCS in 2012, and parts of research work can be found in [1-4]. Usually a system of three or four stoves is operated for a BF in either serial or parallel in order to provide a constant flow of blast. Fig 1 illustrated a schematic view of a hot blast stove system operating in
* Corresponding author. Tel.: +46 920 245223 E-mail address: [email protected]
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the 8th International Conference on Applied Energy. doi:10.1016/j.egypro.2017.03.1041
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Chuan Wang et al. / Energy Procedia 105 (2017) 5128 – 5133
a serial mode where the first two stoves are on-gas (combusting fuel gas) and the third stove is on-blast (providing blast to the BF). The hot stove is a thermal regenerator and a simple structure of hot stove is also presented in Fig.1. An individual stove can be divided into three sections: combustion chamber, dome, and chequerwork chamber. During the period of on-gas, the blast furnace gas (BFG) often together with an enrichment gas is combusted and the hot flue gas flow through the combustion chamber, the dome, and then the chequerwork chamber. The chequerwork chamber is filled with refractory bricks with channels to provide a large surface area for heat transfer as well as a large volume for energy storage. The chequerwork brick is heated and stores the thermal energy. After on-gas, the stove is switched to on-blast where the cold blast is heated by flowing from the bottom of the chequerwork, through the dome and a part of the combustion chamber. When the hot blast leaves the stove, it is often mixed with a certain amount of the cold blast to produce a constant flow with a stable temperature before it is injected into the BF as shown in the figure. Dome
Combustion chamber
Check chamber
Hot blast
Cold blast
Fig. 1. Schematic view of a hot stove-blast furnace system (left) and an individual stove (right)
2. Modelling of stove oxygen enrichment 2.1 Stove oxygen enrichment Traditionally the combustion air is used in hot stoves for fuel combustion. For the stove oxygen enrichment (SOE), the combustion air is be enriched with gaseous oxygen. Compared to air-fuel combustion, oxygen enrichment requires less fuel due to the reduction in heat losses to the flus gas associated with reduction or elimination of nitrogen from the combustion air. There are also some other advantages of using oxygen-enrichment combustion technologies, such as lower NOx emissions, higher productivity, improved temperature stability and heat transfer [5-9]. The SOE concept is illustrated in Fig. 2.
Fig.2. The layout of stove oxygen enrichment
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2.1 CFD modelling CFD has been used to model mixing of oxygen and combustion air [1]. A 3D-model of the burner and part of the air channel was created. A lance is inserted at the back of the burner where oxygen is injected. Fig.3 illustrates both burner and oxygen lance in reality and 3D model.
Fig.3. Burner, air channel and oxygen lance. Left: real burner with oxygen lance; Right: burner in 3D model
The overall results show that the airflow is strongly affected by the 90 degree bend which can be seen in Fig.4. The flow will not be uniform at the position of BF-gas injection. Because of this it is even more important that the oxygen is well mixed with the airflow to avoid streams of high oxygen level that might damage the downstream equipment.
Fig. 4. Mixture of oxygen and combustion air at the outlet. Left: Velocity [m/s] at the centre plane; Right: Oxygen level [-] for enrichment up to 23% (left) and 22% (right) with different lance insertion depths
The mixture of oxygen with combustion air is decided by looking at how uniform the oxygen level is at the outlet of the model, i.e. where the fuel is mixed with the air stream. Fig.4 clearly shows how the lance position affects mixing. Even though the oxygen amount is higher in the left figure compared to the right figure, the mixing is better in the left case because of a more favorable lance position. 2.2 Mathematic model of the oxygen enrichment to hot stoves
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In our previous work, a mathematic model was developed using a finite difference approximation for the heat transfer inside the stove during operation to evaluate the performance of the hot stove system [4]. The model showed a good agreement with the measured process data. In this presented work, the model was used to simulate the effects of SOE on hot stoves’ performance under the circumstance that hot stoves are combusted by only BFG. The modelling cases are described below: x Reference case: the conventional air-fuel hot stoves x Case 1: SOE case with oxygen level up to 25% in the combustion air with the same firing time as the reference case; x Case 2: SOE case with oxygen level of 25% in the combustion air but with reduced firing time to get the same hot blast temperature as the reference case at the end of the blast cycle. For all cases, blast and BFG volume flow rate was kept constant. Consequently, for the SOE cases, the flue gas flow rate is lowered, due to reduced N2 content in the combustion air. Fig. 5 shows the modelling results in different cases. Compared to the reference case, a higher dome temperature can be achieved with SOE when the firing time is kept the same, meanwhile, the flue gas temperature in Case 1 becomes lower. Low heat loss in the flue gas will lead to high energy efficiency in the hot stove. In Case 2, a higher dome temperature can also be achieved, at the same time the firing time is shortened about 4.5 minutes. With the shortened on-gas time in case 2 compared to Case 1, a lower specific fuel gas usage and lower flue gas temperature is obtained, which shows an increase in the energy efficiency. Ref. DT Case 1 DT Case 2 DT
Ref. HBT Case 1 HBT Case 2 HBT
Ref. Grid T Case 1 Grid T Case 2 Crid T
Ref. FGT Case 1 FGT Case 2 FGT
Fig. 5. Modelled temperatures for dome and hot blast (left), the grid and flue gas (right) for difference cases DT: dome temperature; HBT: hot blast temperature; Grid T: grid temperature; FGT: flue gas temperature
3. Industrial testing of stove oxygen enrichment at an ironmaking factory DK Recycling und Roheisen GmbH is a German company and the world's biggest recycler of ferrous waste materials. The iron content of the supplied waste materials is recovered as pig iron in the blast furnace. The pig iron, the main product from DK Recycling, is delivered to the foundry industry. The zinc content of the waste materials is also recovered as a zinc oxide concentrate. Slag from the blast furnace is used in the building industry. As shown in Fig. 6, the main process route at DK Recycling
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Chuan Wang et al. / Energy Procedia 105 (2017) 5128 – 5133
consists of sinter plant and blast furnace, combined with a power plant for utilization of blast furnace. DK recycles approx. 500,000 tons ferrous waste materials per year, and approximately 300,000 tons of pig iron is delivered to the customers per year. Sinter Coke Batteries Quartzite PCI Scrap
Sinter
Legends BFG Natural gas Oxygen
Hot metal
BFG
NG
O2 El. internal
El. sold
Fig. 6. Schematic process layout at DK Recycling
SOE test was performed at hot stove No. 2 at DK Recycling in March, 2016. For the oxygen enrichment, the oxygen was added into the combustion air flow, and the oxygen is controlled as an individual flow to the hot stove. The stoves control system is responsible for the control of the ambient air flow and oxygen enrichment flow at the hot stove No. 2. For the performed test, the lance was positioned in the center of the main combustion pipe line in front of the combustion chamber inlet burner and BFG gas burner. During the test, for the safety reason the oxygen level in the combustion air was gradually increased from 21% to 25%, which can be seen from Fig. 7. The figure shows that a higher dome temperature was obtained during the three cycles for SOE testing, marked with the red dash line. Meantime, it was noticed that the hot stove was heated up faster, which was in a good agreement with the modelling results presented in Fig. 5. For the case of hot stove No. 2 at DK Recycling, it was observed a shortened time in rang of 10-20 minutes compared to the previous cycles.
Fig. 7. Process data from the control system for Hot Stove No.2. Left: Illustration of the oxygen control [upper green is the speed of combustion air fan, rpm; upper red is the dome temperature; middle green is actuating variable (% of maximum speed of the combustion air fan; lower black: O2-content in the off gas of hot stove.] Right: Changing pattern of hot blast temperature
Chuan Wang et al. / Energy Procedia 105 (2017) 5128 – 5133
4. Concluding remarks In this paper, some modelling work on the oxygen enrichment to hot stoves was presented. In the presented work, the hot stove was heated up by BFG generated from the blast furnace during the hot metal production. SOE can improve hot stove’s performance, for instance, increasing dome temperature, hot blast temperature and shorten the firing time. The testing results from an industrial trial were in a good agreement with the modelling results. In addition, CFD modelling work indicated that the oxygen lance position is one important factor to achieve a uniform mixture of oxygen and combustion air for the combustion process. Acknowledgements The authors gratefully acknowledge the European Commission for financial support of this research work (OptiStove, Contract No. RFSR-CT-2012-0003). In addition, the Swedish partners would like to express their thanks to the Swedish Energy Agency (Energimyndigheten) for the financial support in this research work (Project number: 36278-1). DK Recycling would like to thanks for the donation of O2 control equipment from AirLiquide. References [1] Wang C, Lundqvist Magnus, Orre Joel, Bialek Sebastian, Schlimbach Jürgen. CFD modelling of Oxy-fuel combustion of a hot stove at an iron-making factory. Proceeding of Nordic Flame Days, 6th-7th of October 2015 in Copenhagen, Demark. [2] Orre J, Zetterholm J, Lindström D, Schlimbach J, Kotzich S, Wang C. Development of an empirical model for hot stove system at the iron-making plant. Conference proceeding of METEC & 2nd ESTAD 2015, Düsseldorf, Germany, 15-19 June, 2015. [3] Wang C, Olsson Erik, Larsson J, Sundelin B, Lundqvist M. Practical and research experiences on hot stoves’ operation at SSAB EMEA No. 4 Blast Furnace. Conference proceeding of AISTech 2014 - The Iron & Steel Technology Conference and Exposition is scheduled for 5–8 May 2014 at the Indiana Convention Center in Indianapolis, Ind., USA. [4] Zetterholm J, Ji X, Sundelin B, Martin P. M. and Wang C. Dynamic modelling for the hot blast stove. International Journal of Applied Energy. 2016. doi:10.1016/j.apenergy.2016.02.128 [5] Kramer, H. The effect of oxygen enrichment on radiative heat transfer. Fuel Efficiency and NOx Emissions, TOTeM17:IFRF, 2000. [6] Wang C, Cameron A, Bodén A, Karlsson J, Hooey L. Hot stove oxygen-enriched combustion in an iron-making plant. Oral presentation at Swedish-Finnish Flame Days, January 26-27, 2011, Piteå, Sweden. [7] Wang C, Karlsson J, Hooey L, Bodén A. Application of oxygen enrichment in hot stoves and its potential influences on the energy system at an integrated steel plant. International conference of World Renewable Energy Congress 2011 - Sweden 8-11 May 2011, Linköping, Sweden. [8] Michelsson K, Geach M, Niemi T, Martin PM. Improved Blast Furnace Stove Operation With the Use of Oxygen Enriched Combustion Air. Conference proceeding of AISTech 2014 - The Iron & Steel Technology Conference and Exposition is scheduled for 7–10 May 2012, Atlanda, USA. [9] Blostein, Ph., Devaux, M., Grant, M. Use of industrial gases in blast-furnace operation. Metallurgist 2011; 55 (7): 552–557.
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ScienceDirect Energy Procedia 105 (2017) 5128 – 5133
The 8th International Conference on Applied Energy – ICAE2016
Modelling and analysis of oxygen enrichment to hot stoves Chuan Wanga,d,*, Jonas Zetterholmb, Magnus Lundqvista, Jürgen Schlimbachc b
a Swerea MEFOS, Box 812, Luleå, 97125, Sweden Energy Science/Energy Engineering, Luleå University of Technology, Luleå, 97187, Sweden c DK Recycling und Roheisen GmbH, Werthauser Straße 182, 47053 Duisburg, Germany d Thermal and Flow Engineering Laboratory, Åbo Akademi University, Åbo, Finland
Abstract The paper presents some research work on applying the oxygen enrichment technique to hot stoves that was carried out in one European RFCS project. In the presented work, both theoretical and practical work was studied. A dynamic model was used to investigate the effects of oxygen enrichment on hot stoves’ performance under the condition that only blast furnace gas was used as the fuel gas. The modelling results showed that SOE will enhance the combustion process in hot stoves by increasing hot blast temperature and shortening the on-gas time, which were further verified by industrial trials performed at an iron-making plant. In addition, CFD modelling was performed by simulating different oxygen levels and lance positions at the burner to avoid the hot spot formation during the combustion. Keywords: Stove oxygen enrichment; Blast furnace; hot blast; dynamic model; CFD
1. Introduction For the ore based iron-making process, hot stoves are very important auxilary equipment to the blast furnace (BF), providing hot blast to the process. The blast provides thermal energy and reducing gas to the BF process through combustion of coke and injected fuel at the tuyere level. The target for hot stoves is to provide a high and stable temperature of the blast. Higher blast temperature leads to lower coke and pulverized coal/natural gas consumption in BF. Recent years, more attention has been paid on improving stoves’ performance. For instance, one hot stove project was granted by the research program EU RFCS in 2012, and parts of research work can be found in [1-4]. Usually a system of three or four stoves is operated for a BF in either serial or parallel in order to provide a constant flow of blast. Fig 1 illustrated a schematic view of a hot blast stove system operating in
* Corresponding author. Tel.: +46 920 245223 E-mail address: [email protected]
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the 8th International Conference on Applied Energy. doi:10.1016/j.egypro.2017.03.1041
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Chuan Wang et al. / Energy Procedia 105 (2017) 5128 – 5133
a serial mode where the first two stoves are on-gas (combusting fuel gas) and the third stove is on-blast (providing blast to the BF). The hot stove is a thermal regenerator and a simple structure of hot stove is also presented in Fig.1. An individual stove can be divided into three sections: combustion chamber, dome, and chequerwork chamber. During the period of on-gas, the blast furnace gas (BFG) often together with an enrichment gas is combusted and the hot flue gas flow through the combustion chamber, the dome, and then the chequerwork chamber. The chequerwork chamber is filled with refractory bricks with channels to provide a large surface area for heat transfer as well as a large volume for energy storage. The chequerwork brick is heated and stores the thermal energy. After on-gas, the stove is switched to on-blast where the cold blast is heated by flowing from the bottom of the chequerwork, through the dome and a part of the combustion chamber. When the hot blast leaves the stove, it is often mixed with a certain amount of the cold blast to produce a constant flow with a stable temperature before it is injected into the BF as shown in the figure. Dome
Combustion chamber
Check chamber
Hot blast
Cold blast
Fig. 1. Schematic view of a hot stove-blast furnace system (left) and an individual stove (right)
2. Modelling of stove oxygen enrichment 2.1 Stove oxygen enrichment Traditionally the combustion air is used in hot stoves for fuel combustion. For the stove oxygen enrichment (SOE), the combustion air is be enriched with gaseous oxygen. Compared to air-fuel combustion, oxygen enrichment requires less fuel due to the reduction in heat losses to the flus gas associated with reduction or elimination of nitrogen from the combustion air. There are also some other advantages of using oxygen-enrichment combustion technologies, such as lower NOx emissions, higher productivity, improved temperature stability and heat transfer [5-9]. The SOE concept is illustrated in Fig. 2.
Fig.2. The layout of stove oxygen enrichment
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Chuan Wang et al. / Energy Procedia 105 (2017) 5128 – 5133
2.1 CFD modelling CFD has been used to model mixing of oxygen and combustion air [1]. A 3D-model of the burner and part of the air channel was created. A lance is inserted at the back of the burner where oxygen is injected. Fig.3 illustrates both burner and oxygen lance in reality and 3D model.
Fig.3. Burner, air channel and oxygen lance. Left: real burner with oxygen lance; Right: burner in 3D model
The overall results show that the airflow is strongly affected by the 90 degree bend which can be seen in Fig.4. The flow will not be uniform at the position of BF-gas injection. Because of this it is even more important that the oxygen is well mixed with the airflow to avoid streams of high oxygen level that might damage the downstream equipment.
Fig. 4. Mixture of oxygen and combustion air at the outlet. Left: Velocity [m/s] at the centre plane; Right: Oxygen level [-] for enrichment up to 23% (left) and 22% (right) with different lance insertion depths
The mixture of oxygen with combustion air is decided by looking at how uniform the oxygen level is at the outlet of the model, i.e. where the fuel is mixed with the air stream. Fig.4 clearly shows how the lance position affects mixing. Even though the oxygen amount is higher in the left figure compared to the right figure, the mixing is better in the left case because of a more favorable lance position. 2.2 Mathematic model of the oxygen enrichment to hot stoves
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Chuan Wang et al. / Energy Procedia 105 (2017) 5128 – 5133
In our previous work, a mathematic model was developed using a finite difference approximation for the heat transfer inside the stove during operation to evaluate the performance of the hot stove system [4]. The model showed a good agreement with the measured process data. In this presented work, the model was used to simulate the effects of SOE on hot stoves’ performance under the circumstance that hot stoves are combusted by only BFG. The modelling cases are described below: x Reference case: the conventional air-fuel hot stoves x Case 1: SOE case with oxygen level up to 25% in the combustion air with the same firing time as the reference case; x Case 2: SOE case with oxygen level of 25% in the combustion air but with reduced firing time to get the same hot blast temperature as the reference case at the end of the blast cycle. For all cases, blast and BFG volume flow rate was kept constant. Consequently, for the SOE cases, the flue gas flow rate is lowered, due to reduced N2 content in the combustion air. Fig. 5 shows the modelling results in different cases. Compared to the reference case, a higher dome temperature can be achieved with SOE when the firing time is kept the same, meanwhile, the flue gas temperature in Case 1 becomes lower. Low heat loss in the flue gas will lead to high energy efficiency in the hot stove. In Case 2, a higher dome temperature can also be achieved, at the same time the firing time is shortened about 4.5 minutes. With the shortened on-gas time in case 2 compared to Case 1, a lower specific fuel gas usage and lower flue gas temperature is obtained, which shows an increase in the energy efficiency. Ref. DT Case 1 DT Case 2 DT
Ref. HBT Case 1 HBT Case 2 HBT
Ref. Grid T Case 1 Grid T Case 2 Crid T
Ref. FGT Case 1 FGT Case 2 FGT
Fig. 5. Modelled temperatures for dome and hot blast (left), the grid and flue gas (right) for difference cases DT: dome temperature; HBT: hot blast temperature; Grid T: grid temperature; FGT: flue gas temperature
3. Industrial testing of stove oxygen enrichment at an ironmaking factory DK Recycling und Roheisen GmbH is a German company and the world's biggest recycler of ferrous waste materials. The iron content of the supplied waste materials is recovered as pig iron in the blast furnace. The pig iron, the main product from DK Recycling, is delivered to the foundry industry. The zinc content of the waste materials is also recovered as a zinc oxide concentrate. Slag from the blast furnace is used in the building industry. As shown in Fig. 6, the main process route at DK Recycling
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Chuan Wang et al. / Energy Procedia 105 (2017) 5128 – 5133
consists of sinter plant and blast furnace, combined with a power plant for utilization of blast furnace. DK recycles approx. 500,000 tons ferrous waste materials per year, and approximately 300,000 tons of pig iron is delivered to the customers per year. Sinter Coke Batteries Quartzite PCI Scrap
Sinter
Legends BFG Natural gas Oxygen
Hot metal
BFG
NG
O2 El. internal
El. sold
Fig. 6. Schematic process layout at DK Recycling
SOE test was performed at hot stove No. 2 at DK Recycling in March, 2016. For the oxygen enrichment, the oxygen was added into the combustion air flow, and the oxygen is controlled as an individual flow to the hot stove. The stoves control system is responsible for the control of the ambient air flow and oxygen enrichment flow at the hot stove No. 2. For the performed test, the lance was positioned in the center of the main combustion pipe line in front of the combustion chamber inlet burner and BFG gas burner. During the test, for the safety reason the oxygen level in the combustion air was gradually increased from 21% to 25%, which can be seen from Fig. 7. The figure shows that a higher dome temperature was obtained during the three cycles for SOE testing, marked with the red dash line. Meantime, it was noticed that the hot stove was heated up faster, which was in a good agreement with the modelling results presented in Fig. 5. For the case of hot stove No. 2 at DK Recycling, it was observed a shortened time in rang of 10-20 minutes compared to the previous cycles.
Fig. 7. Process data from the control system for Hot Stove No.2. Left: Illustration of the oxygen control [upper green is the speed of combustion air fan, rpm; upper red is the dome temperature; middle green is actuating variable (% of maximum speed of the combustion air fan; lower black: O2-content in the off gas of hot stove.] Right: Changing pattern of hot blast temperature
Chuan Wang et al. / Energy Procedia 105 (2017) 5128 – 5133
4. Concluding remarks In this paper, some modelling work on the oxygen enrichment to hot stoves was presented. In the presented work, the hot stove was heated up by BFG generated from the blast furnace during the hot metal production. SOE can improve hot stove’s performance, for instance, increasing dome temperature, hot blast temperature and shorten the firing time. The testing results from an industrial trial were in a good agreement with the modelling results. In addition, CFD modelling work indicated that the oxygen lance position is one important factor to achieve a uniform mixture of oxygen and combustion air for the combustion process. Acknowledgements The authors gratefully acknowledge the European Commission for financial support of this research work (OptiStove, Contract No. RFSR-CT-2012-0003). In addition, the Swedish partners would like to express their thanks to the Swedish Energy Agency (Energimyndigheten) for the financial support in this research work (Project number: 36278-1). DK Recycling would like to thanks for the donation of O2 control equipment from AirLiquide. References [1] Wang C, Lundqvist Magnus, Orre Joel, Bialek Sebastian, Schlimbach Jürgen. CFD modelling of Oxy-fuel combustion of a hot stove at an iron-making factory. Proceeding of Nordic Flame Days, 6th-7th of October 2015 in Copenhagen, Demark. [2] Orre J, Zetterholm J, Lindström D, Schlimbach J, Kotzich S, Wang C. Development of an empirical model for hot stove system at the iron-making plant. Conference proceeding of METEC & 2nd ESTAD 2015, Düsseldorf, Germany, 15-19 June, 2015. [3] Wang C, Olsson Erik, Larsson J, Sundelin B, Lundqvist M. Practical and research experiences on hot stoves’ operation at SSAB EMEA No. 4 Blast Furnace. Conference proceeding of AISTech 2014 - The Iron & Steel Technology Conference and Exposition is scheduled for 5–8 May 2014 at the Indiana Convention Center in Indianapolis, Ind., USA. [4] Zetterholm J, Ji X, Sundelin B, Martin P. M. and Wang C. Dynamic modelling for the hot blast stove. International Journal of Applied Energy. 2016. doi:10.1016/j.apenergy.2016.02.128 [5] Kramer, H. The effect of oxygen enrichment on radiative heat transfer. Fuel Efficiency and NOx Emissions, TOTeM17:IFRF, 2000. [6] Wang C, Cameron A, Bodén A, Karlsson J, Hooey L. Hot stove oxygen-enriched combustion in an iron-making plant. Oral presentation at Swedish-Finnish Flame Days, January 26-27, 2011, Piteå, Sweden. [7] Wang C, Karlsson J, Hooey L, Bodén A. Application of oxygen enrichment in hot stoves and its potential influences on the energy system at an integrated steel plant. International conference of World Renewable Energy Congress 2011 - Sweden 8-11 May 2011, Linköping, Sweden. [8] Michelsson K, Geach M, Niemi T, Martin PM. Improved Blast Furnace Stove Operation With the Use of Oxygen Enriched Combustion Air. Conference proceeding of AISTech 2014 - The Iron & Steel Technology Conference and Exposition is scheduled for 7–10 May 2012, Atlanda, USA. [9] Blostein, Ph., Devaux, M., Grant, M. Use of industrial gases in blast-furnace operation. Metallurgist 2011; 55 (7): 552–557.
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