| 1. |
- Ahmed, Hesham, et al.
(author)
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Alternative Reducing Agents for Sustainable Blast Furnace Ironmaking
- 2017
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In: ESTAD 2017.
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Conference paper (peer-reviewed)abstract
- Lowering of CO2 emission from the integrated steel industry as well as minimizing theneed for landfill are important challenges in the focus for the integrated steel industry. With thisaim collaborative research projects have been conducted and are on-going on the possible useof renewable reducing agents or such with high content of H2 as well as for enabling recyclingof 1in-plant fines so far not possible to use. Due to contents of undesired impurities the blastfurnace (BF) sludge has to be pre-treated in an appropriate way before carbon and iron oxidecan be valorized. In order to understand the impact of alternative reducing agents as injectedthrough the tuyeres or part of top charged agglomerates containing iron oxide, samples oftorrefied biomass, plastic and in-plant fines have been analyzed by means of thermogravimetricanalyzer coupled with a mass spectrometer (TGA-MS).The results proved that effective utilization of carbon bearing BF dust and sludge as analternate reducing agent could be realized and can be implemented into BF after adequateupgrading. Plastic materials and biomass based reductants decomposition is associated with therelease of volatiles. The main contents of these volatiles are CO, H2 and hydrocarbon which areall known for their reduction potential. Moreover, injection of such materials is expected toimprove process efficiency and sustain the gas permeability along the BF cohesive zone. Onthe other hand, top charging of these materials would improve the energy and materialefficiency in the BF due to their higher reactivity compared to conventional carbon.
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| 2. |
- Ahmed, Hesham, et al.
(author)
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Effect of the Ash from H2‐Rich Carbonaceous Materials on the Physicochemical Properties of Raceway Slag and Coke Reactivity
- 2020
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In: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X. ; 91:11
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Journal article (peer-reviewed)abstract
- The iron and steel industry is one of the most important sectors worldwide, and it has a great impact on the global economy; however, this sector is still highly dependent on fossil carbon. To decrease this dependency, approaches to partially replace the injected pulverized coal with secondary, highly reactive, renewable (biomass) and H2‐rich materials have been studied. The injection of such materials is expected to significantly decrease the emitted CO2 from blast furnaces. However, due to the different ash composition of these alternative materials (especially alkali and alkaline earth metals) compared to that of ordinary injected coal, these materials are expected to alter the raceway slag properties and affect the coke reactivity. In the present article, the effect of the ash from different hydrogen‐rich carbonaceous materials on the raceway slag physicochemical properties as well as coke reactivity is reported. The melting characteristics of the ash briquettes in contact with the coke and wettability of the melted ash on the coke surface are determined visually using an optical heating microscope. The effect of the ash on the coke reactivity is studied by means of thermogravimetry under a continuous flow of CO2.
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| 3. |
- Ahmed, Hesham, et al.
(author)
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Reduction Behaviour of Self-reducing Blends of In-plant Fines in Inert Atmosphere
- 2015
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In: ISIJ International. - 0915-1559 .- 1347-5460. ; 55:10, s. 2082-2089
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Journal article (peer-reviewed)abstract
- Large amount of dust and sludge recovered during cleaning of iron and steel making process gases are annually put on landfill or intermediate storage. These by-products have high contents of iron (Fe) and carbon (C) that potentially could be utilized in the steel industry. However, due to the presence of impuritycompounds as well as the unsuitable physical properties, these by-products cannot be recycled directly. The main objective of the present study is to investigate the possibilities to recover the valuable components Fe and C in these by-products and thereby decrease the need of landfills at the steel plants as well as reduce the consumption of virgin materials, including fossil coal, and reduce CO2 emissions. A recycling route has been investigated by means of laboratory trials and FactSage thermodynamic modeling. Four different blends of BF and BOF dusts and sludges are prepared in predetermined ratios. Reduction behavior of each blend is studied using TG/DTA/QMS and in-situ high temperature X-ray diffraction. High temperature physical properties like softening, swelling and melting are also investigated by means of heatingmicroscope. The obtained results indicate the feasibility of both minimizing the impurity elements as well as recovering of valuable components.
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| 4. |
- Andersson, Anton, et al.
(author)
-
A holistic and experimentally-based view on recycling of off-gas dust within the integrated steel plant
- 2018
-
In: Metals. - Basel : MDPI AG. - 2075-4701. ; 8:10
-
Journal article (peer-reviewed)abstract
- Ore-based ironmaking generates a variety of residues, including slags and fines such as dust and sludges. Recycling of these residues within the integrated steel plant or in other applications is essential from a raw-material efficiency perspective. The main recycling route of off-gas dust is to the blast furnace (BF) via sinter, cold-bonded briquettes and tuyere injection. However, solely relying on the BF for recycling implicates that certain residues cannot be recycled in order to avoid build-up of unwanted elements, such as zinc. By introducing a holistic view on recycling where recycling via other process routes, such as the desulfurization (deS) station and the basic oxygen furnace (BOF), landfilling can be avoided. In the present study, process integration analyses were utilized to determine the most efficient recycling routes for off-gas dust that are currently not recycled within the integrated steel plants of Sweden. The feasibility of recycling was studied in experiments conducted in laboratory, pilot, and full-scale trials in the BF, deS station, and BOF. The process integration analyses suggested that recycling to the BF should be maximized before considering the deS station and BOF. The experiments indicated that the amount of residue that are not recycled could be minimized.
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| 5. |
- Andersson, Anton, et al.
(author)
-
Evaluation of evaporation kinetics of potassium from synthetic blast furnace slag using full factorial design of experiments
- 2021
-
Conference paper (peer-reviewed)abstract
- In the present work, a full factorial design of experiments with three factors was performed studying the evaporation of potassium (K) from synthetic blast furnace (BF) slag. The experiments showed that slag temperature and B2 basicity (%CaO/%SiO2) had the greatest effect on the evaporation kinetics, while the effect of the MgO content was comparatively less. The regression model developed based on the experimental design could describe the evaporation of K from actual BF slags fairly well, provided that they were within the experimental matrix of the design of experiments.
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| 6. |
- Andersson, Anton, et al.
(author)
-
Recycling of Blast Furnace Sludge to the Blast Furnace via Cold-Bonded Briquettes: Evaluation of Feasibility and Influence on Operation
- 2019
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In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 59:10, s. 1786-1795
-
Journal article (peer-reviewed)abstract
- Ore-based steelmaking generates various residues including dusts, sludges, scales and slags. Recycling of these residues within the process or via other applications is essential for sustainable production of steel. In blast furnace (BF) ironmaking, the gas-cleaning equipment generally recovers the particles in the off-gas as dust and sludge. Traditionally, the dry dust is recycled via the sinter or, in the case of pellet-based BF operation, via cold-bonded briquettes and injection. As the BF sludge mainly consists of iron and carbon, this residue is of interest to recycle together with the BF dust. However, depending on how the BF is operated, these two residues are more or less the major outlet of zinc from the furnace. Thus, to limit the recycled load of zinc, both materials cannot be recycled without dezincing the sludge prior to recycling. Dezincing and recycling of the low-zinc fraction of BF sludge via sinter have been reported whereas recycling via cold-bonded briquettes has not been performed. In the present study, cold-bonded briquettes containing the low-zinc fraction of dezinced BF sludge were charged as basket samples to the LKAB Experimental Blast Furnace (EBF). The excavated basket samples from the quenched EBF suggested that additions of up to 20 wt.% of upgraded BF sludge was feasible in terms of reducibility and strength. Based on these results, BF sludge were added to cold-bonded briquettes and charged in industrial-scale trials. The trials indicated that the annual generation of BF sludge, after dezincing, could be recycled to the BF.
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| 7. |
- Andersson, Anton
(author)
-
Recycling of Blast Furnace Sludge within the Integrated Steel Plant : Potential for Complete Recycling and Influence on Operation
- 2019
-
Doctoral thesis (other academic/artistic)abstract
- Ore-based steelmaking generates various residues including dust, sludges, scales and slags. Internal and external recycling has allowed for 68-90 % of the dust, sludges and scales to be recycled. However, several residues are landfilled despite containing elements valuable as raw material in the production of steel. One such residue is the blast furnace (BF) sludge which has a chemical composition dominated by iron and carbon. In 2008, the annual worldwide landfilling of BF sludge was estimated to 8 million metric tons in dry weight. Furthermore, as the iron production via the BF route has increased significantly since 2008, the landfilling of BF sludge could be even higher as of today. Thus, the potential to reclaim valuable iron and carbon while improving the raw material efficiency is substantial.Traditionally, in-plant recycling of residues generated in the integrated steel plant is conducted via the sinter or, in the case of pellet-based BFs, via cold-bonded briquettes and injection in the BF tuyeres. The challenges in recycling BF sludge via these routes are the fine particle size distribution, the high water content and the zinc content. Of these challenges, the latter is the main concern as too high zinc loads in the BF lead to increased reductant rates, reduced lining life of carbon-based bricks and scaffold formation, which may disturb the process. The challenge regarding zinc has previously been addressed by pretreating the sludge, generating a low-zinc and high-zinc fraction where the former has been recycled to the BF via the sinter or cold-bonded pellets. Although pretreatment and recycling of the low-zinc fraction have been achieved in industrial scale, the reported sludges are generally coarse in size and high in zinc. Furthermore, recycling of pretreated BF sludge to the BF utilizing cold-bonded briquettes has not been reported and the internal recycling of the high-zinc fraction has not been considered.In the present thesis, newly produced BF sludge with a fine particle size distribution and low zinc content was characterized finding that a majority of the zinc was present in weak acid soluble phases and that the finest fraction of the sludge carried most of the zinc. Based on these findings, the BF sludge was pretreated using sulfuric acid leaching, hydrocycloning and tornado treatment, respectively. Sulfuric acid leaching was the most effective method in selectively separating zinc from the iron, carbon and solids. However, both hydrocycloning and tornado treatment were successful in generating a fraction low in zinc.The low-zinc fraction of the tornado-treated BF sludge was incorporated in cold-bonded briquettes and tested for strength, swelling and intrinsic reducibility. Furthermore, the briquettes were charged as basket samples in the LKAB Experimental Blast Furnace (EBF) in order to study the behavior in actual BF conditions. The results suggested that the low-zinc fraction of the BF sludge could be added to the briquettes without negatively affecting the performance of the briquettes in the BF. The results were confirmed in industrial-scale trials where non-treated BF sludge was added to cold-bonded briquettes in an amount that would facilitate complete recycling of the low-zinc fraction. Charging these briquettes to the BF did not induce any negative effects on the process or the hot metal (HM) quality.The high-zinc fraction of the tornado-treated BF sludge was added in self-reducing cold-bonded agglomerates and studied in technical-scale smelting reduction experiments aiming at recycling to the HM desulfurization plant. The experiments suggested that melt-in problems could be expected when using either briquettes or pellets. Nonetheless, industrial-scale trials were performed aiming to study the feasibility of recycling cold-bonded briquettes to both the HM desulfurization plant and basic oxygen furnace (BOF). These trials suggested that a substantial amount could be recycled without affecting the final quality of the steel. However, additional experiments were identified to be required in order to enable 100 % recycling of the high-zinc fraction of the tornado-treated BF sludge.Based on the results from the experimental work, a holistic concept to completely recycle the BF sludge within the integrated steel plant was suggested.
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| 8. |
- Andersson, Anton, et al.
(author)
-
RECYCLING OF THE HIGH-ZINC FRACTION OF UPGRADED BF SLUDGE WITHIN THE INTEGRATED STEEL PLANT
- 2018
-
Conference paper (other academic/artistic)abstract
- Ore-based steelmaking generates a variety of residues and recycling of these within the existing process or via other applications is essential for sustainable production from mainly environmental aspects. In blast furnace (BF) ironmaking, the gas-cleaning equipment recovers the particles in the off-gas as BF dust and sludge. Traditionally, the dry dust is recycled back to the BF. In order to recycle the BF sludge together with the dust, the sludge has to be upgraded, removing zinc. The literature reports cases of recycling BF dust and the low-zinc fraction of upgraded BF sludge to the BF. However, research towards recycling of the high-zinc fraction of BF sludge within the ore-based steel plant is limited. In the present paper, the high-zinc fraction of tornado-treated BF sludge was incorporated in self-reducing cold-bonded agglomerates. The agglomerates were subjected to smelting reduction experiments aiming to study the feasibility of recycling the in-plant residues to the desulphurization plant. Difficulties in the melt-in of the agglomerates suggested that cold-bonded pellets were more suitable for recycling than the briquettes. However, full-scale trials suggested that cold-bonded briquettes can be used to recycle in-plant residues to the desulphurization plant without affecting the desulphurization process and final steel quality.
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| 9. |
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| 10. |
- Andersson, Anton, et al.
(author)
-
The Potential of Recycling the High-Zinc Fraction of Upgraded BF Sludge to the Desulfurization Plant and Basic Oxygen Furnace
- 2018
-
In: Metals. - : MDPI. - 2075-4701. ; 8:12
-
Journal article (peer-reviewed)abstract
- In ore-based steelmaking, blast furnace (BF) dust is generally recycled to the BF via the sinter or cold-bonded briquettes and injection. In order to recycle the BF sludge to the BF, the sludge has to be upgraded, removing zinc. The literature reports cases of recycling the low-zinc fraction of upgraded BF sludge to the BF. However, research towards recycling of the high-zinc fraction of BF sludge within the ore-based steel plant is limited. In the present paper, the high-zinc fraction of tornado-treated BF sludge was incorporated in self-reducing cold-bonded briquettes and pellets. Each type of agglomerate was individually subjected to technical-scale smelting reduction experiments aiming to study the feasibility of recycling in-plant residues to the hot metal (HM) desulfurization (deS) plant. The endothermic reactions within the briquettes decreased the heating and reduction rate leaving the briquettes unreduced and unmelted. The pellets were completely reduced within eight minutes of contact with HM but still showed melt-in problems. Cold-bonded briquettes, without BF sludge, were charged in industrial-scale trials to study the recycling potential to the HM deS plant and basic oxygen furnace (BOF). The trials illustrated a potential for the complete recycling of the high-zinc fraction of BF sludge. However, further studies were identified to be required to verify these results.
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| 11. |
- Andersson, Anton, et al.
(author)
-
The Quantitative Effect of Blast Furnace Slag Composition and Temperature on the Kinetics of Potassium Evaporation
- 2020
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In: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer. - 1073-5615 .- 1543-1916. ; 51:6, s. 2711-2723
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Journal article (peer-reviewed)abstract
- Increased in-plant recycling and lower quality raw material in terms of alkali content drive the alkali load in the blast furnace (BF) to higher levels. Excessive load of alkalis, primarily potassium, has several negative effects on the BF operation, which necessitates means to control the removal of potassium from the BF. One method to improve the removal is by increasing the potassium retention in the slag, which is controlled by the evaporation kinetics of potassium. Although several authors have studied factors affecting the evaporation rate, none of these studies have quantitatively investigated the effect of these parameters and attempted to relate these effects to slags from the industry. In the present work, a full-factorial design of experiments with three factors (B2 basicity, MgO content, and temperature) was performed, studying the evaporation of potassium from synthetic BF slag. The results suggested that multiple linear regression is suitable to describe the evaporation kinetics of potassium within the boundaries of the design of experiments. However, extrapolating to industrial slags of different compositions and additional slag components is best performed utilizing the corrected optical basicity. The corrected optical basicity showed a linear relation to the evaporation kinetics of potassium, which was related to the correlation between diffusivity and corrected optical basicity.
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| 12. |
- Andersson, Anton, et al.
(author)
-
Upgrading of Blast Furnace Sludge and Recycling of the Low-Zinc Fraction via Cold-bonded Briquettes
- 2019
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In: Journal of Sustainable Metallurgy. - : Springer. - 2199-3823 .- 2199-3831. ; :3, s. 350-361
-
Journal article (peer-reviewed)abstract
- Depending on the operation of the blast furnace (BF), the main outlet of zinc from the furnace is more or less via the BF dust and sludge. As the dust is recycled to the BF, the sludge has to be de-zinced prior to recycling to prevent the accumulation of zinc in the BF. De-zincing and recycling of the low-zinc fraction via sinter have been reported. However, no research con-cerning recycling of upgraded BF sludge via cold-bonded briquettes has been performed. In the present study, a fine-grained BF sludge with low zinc content, generated by a BF operating on a ferrous burden of 100% pellets, was upgraded using the tornado process. The process simultaneously dried and separated the BF sludge into a high-zinc and a low-zinc fraction. The feasibility of recycling the low-zinc fraction to the BF using cold-bonded briquettes was studied on a laboratory-scale BF shaft simulator. On comparison with a reference briquette, the experiments indicated that 10 wt% of the upgraded BF sludge can be added to the briquette without negatively affecting the reducibility. Higher additions were found to render the briquette less reduced compared to the reference under test conditions corresponding to the central part of the BF. The strength of the briquettes was not compromised with the addition of the upgraded BF sludge, and a decision to study the briquettes in the LKAB experimental blast furnace was made in order to evaluate the behavior under actual BF conditions.
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| 13. |
- El-Tawil, Asmaa A., et al.
(author)
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Devolatilization Kinetics of Different Types of Bio-Coals Using Thermogravimetric Analysis
- 2019
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In: Metals. - : MDPI. - 2075-4701. ; 9:2
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Journal article (peer-reviewed)abstract
- The interest of the steel industry in utilizing bio-coal (pre-treated biomass) as CO2-neutral carbon in iron-making is increasing due to the need to reduce fossil CO2 emission. In order to select a suitable bio-coal to be contained in agglomerates with iron oxide, the current study aims at investigating the thermal devolatilization of different bio-coals. A thermogravimetric analyzer (TGA) equipped with a quadrupole mass spectrometer (QMS) was used to monitor the weight loss and off-gases during non-isothermal tests with bio-coals having different contents of volatile matter. The samples were heated in an inert atmosphere to 1200 °C at three different heating rates: 5, 10, and 15 °C/min. H2, CO, and hydrocarbons that may contribute to the reduction of iron oxide if contained in the self-reducing composite were detected by QMS. To explore the devolatilization behavior for different materials, the thermogravimetric data were evaluated by using the Kissinger– Akahira–Sonuse (KAS) iso-conversional model. The activation energy was determined as a function of the conversion degree. Bio-coals with both low and high volatile content could produce reducing gases that can contribute to the reduction of iron oxide in bio-agglomerates and hot metal quality in the sustained blast furnace process. However, bio-coals containing significant amounts of CaO and K2O enhanced the devolatilization and released the volatiles at lower temperature.
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| 14. |
- El-Tawil, Asmaa A., et al.
(author)
-
Influence of Bio-Coal Properties on Carbonization and Bio-Coke Reactivity
- 2021
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In: Metals. - : Minerals, Metals & Materials Society. - 2075-4701. ; 11:11
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Journal article (peer-reviewed)abstract
- Coke corresponds to 2/3–3/4 of the reducing agents in BF, and by the partial replacement of coking coals with 5–10% of bio-coal, the fossil CO2 emissions from the BF can be lowered by ~4–8%. Coking coal blends with 5% and 10% additions of bio-coals (pre-treated biomass) of different origins and pre-treatment degrees were carbonized at laboratory scale and with a 5% bio-coal addition at technical scale, aiming to understand the impact on the bio-coal properties (ash amount and composition, volatile matter content) and the addition of bio-coke reactivity. A thermogravimetric analyzer (TGA) connected to a quadrupole mass spectroscope monitored the residual mass and off-gases during carbonization. To explore the effect of bio-coal addition on plasticity, optical dilatometer tests were conducted for coking coal blends with 5% and 10% bio-coal addition. The plasticity was lowered with increasing bio-coal addition, but pyrolyzed biomass had a less negative effect on the plasticity compared to torrefied biomasses with a high content of oxygen. The temperature for starting the gasification of coke was in general lowered to a greater extent for bio-cokes produced from coking coal blends containing bio-coals with higher contents of catalyzing oxides. There was no significant difference in the properties of laboratory and technical scale produced coke, in terms of reactivity as measured by TGA. Bio-coke produced with 5% of high temperature torrefied pelletized biomass showed a similar coke strength as reference coke after reaction.
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| 15. |
- El-Tawil, Asmaa A., et al.
(author)
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Self-Reduction Behavior of Bio-Coal Containing Iron Ore Composites
- 2020
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In: Metals. - : MDPI. - 2075-4701. ; 10:1
-
Journal article (peer-reviewed)abstract
- The utilization of CO2 neutral carbon instead of fossil carbon is one way to mitigate CO2 emissions in the steel industry. Using reactive reducing agent, e.g., bio-coal (pre-treated biomass) in iron ore composites for the blast furnace can also enhance the self-reduction. The current study aims at investigating the self-reduction behavior of bio-coal containing iron ore composites under inert conditions and simulated blast furnace thermal profile. Composites with and without 10% bio-coal and sufficient amount of coke breeze to keep the C/O molar ratio equal to one were mixed and Portland cement was used as a binder. The self-reduction of composites was investigated by thermogravimetric analyses under inert atmosphere. To explore the reduction progress in each type of composite vertical tube furnace tests were conducted in nitrogen atmosphere up to temperatures selected based on thermogravimetric results. Bio-coal properties as fixed carbon, volatile matter content and ash composition influence the reduction of iron oxide. The reduction of the bio-coal containing composites begins at about 500 °C, a lower temperature compared to that for the composite with coke as only carbon source. The hematite was successfully reduced to metallic iron at 850 °C by using bio-coal, whereas with coke as a reducing agent temperature up to 1100 °C was required.
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| 16. |
- El-Tawil, Asmaa, et al.
(author)
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Influence of Modified Bio-Coals on Carbonization and Bio-Coke Reactivity
- 2021
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In: Metals. - : MDPI. - 2075-4701. ; 12:1
-
Journal article (peer-reviewed)abstract
- Substitution of coal in coking coal blend with bio-coal is a potential way to reduce fossil CO2 emissions from iron and steelmaking. The current study aims to explore possible means to counteract negative influence from bio-coal in cokemaking. Washing and kaolin coating of bio-coals were conducted to remove or bind part of the compounds in the bio-coal ash that catalyzes the gasification of coke with CO2. To further explore how the increase in coke reactivity is related to more reactive carbon in bio-coal or catalytic oxides in bio-coal ash, ash was produced from a corresponding amount of bio-coal and added to the coking coal blend for carbonization. The reaction behavior of coals and bio-coals under carbonization conditions was studied in a thermogravimetric analyzer equipped with a mass spectrometer during carbonization. The impact of the bio-coal addition on the fluidity of the coking coal blend was studied in optical dilatometer tests for coking coal blends with and without the addition of bio-coal or bio-coal ash. The result shows that the washing of bio-coal will result in lower or even negative dilatation. The washing of bio-coals containing a higher amount of catalytic components will reduce the negative effect on bio-coke reactivity, especially with acetic acid washing when the start of gasification temperature is less lowered. The addition of bio-coal coated with 5% kaolin do not significantly lower the dilatation-relative reference coking coal blend. The reactivity of bio-cokes containing bio-coal coated with kaolin-containing potassium oxide was higher in comparison to bio-coke containing the original bio-coal. The addition of ash from 5% of torrefied bio-coals has a moderate effect on lowering the start of gasification temperature, which indicates that the reactive carbon originating from bio-coal has a larger impact.
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| 17. |
- El-Tawil, Asmaa
(author)
-
Influence of the properties of bio-coal as a substitute for fossil coal in carbon composite agglomerates and in coke
- 2022
-
Doctoral thesis (other academic/artistic)abstract
- The iron-ore-based blast furnace (BF) process is still the most dominant method for producing metallic iron units for steelmaking, and the BF is also the main contributor to the 7-9% of global CO2 emissions which, according to World Steel Association, originate from the steel industry. The steel industry is aiming to reduce CO2 emissions by different means. In the short term, replacing fossil coal with renewable carbonaceous material like bio-coal (pre-treated biomass) is possible and, in the longer term, by using hydrogen. The use of bio-coal as a part of top-charged self-reducing composites containing iron oxide (bio-agglomerates) or as part of coking coal blend producing bio-coke are potential ways to introduce bio-coal into the BF. The aim of this study is to understand the impact of bio-coal properties i.e., volatile matter, carbon structure and ash content ,and composition on the self-reduction of composites as well as on cokemaking and the quality of produced coke. In order to select a suitable bio-coal to be contained in agglomerates with iron oxide, the devolatilization behavior of different types of bio-coals was studied in thermogravimetric analyser (TGA) connected to a quadrupole mass spectrometer to monitor the weight loss and components in off-gases. The devolatilization was conducted at diffetrent heating rates: 5, 10 and 15°C/min in an inert atmosphere up to 1200°C. The obtained data were evaluated using the Kissinger-Akahira-Sonuse iso-conversional model and the activation energy was determined as a function of conversion degree. The main finding is that bio-coal pretreated at low or high temperatures produces reducing gases that can contribute to the reduction of iron oxide in bio-agglomerates. Torrefied bio-coal containing a higher content of ash and therefore higher content of catalytic oxide as e.g., alkali and alkaline earth metal oxides, releases the volatile matter at a lower temperature, when it cannot fully contribute to the reduction. The self-reduction behavior of composites was studied in a TGA in argon atmosphere using a BF-simulated temperature profile. To investigate the effect of added bio-coals in the reduction interrupted tests using similar temperature profile as in TGA were conducted in nitrogen atmosphere in a vertical tube furnace up to temperatures selected based on TGA test results. The contents of volatile matter, fixed carbon and composition of ash in the bio-coals influenced the self-reduction. X-Ray Diffraction (XRD) analysis of composites collected after interrupted tests shows that the self-reduction of bio-coal-containing composites started at 500°C, while it started at 740°C with coke as the only carbon source. The hematite was successfully reduced to metallic iron at 850°C with bio-coal present as a reducing agent, but not until 1100°C when coke was used. Bio-coal containing a high content of volatile matter, but with a low content of catalytic oxide, enhanced the reduction mostly and wusite was detected by XRD in the sample interrupted at 680°C.The possibility to introduce bio-coal into cokemaking was investigated by carbonization of coking coal blends with addition of various types of bio-coals in the laboratory and on technical scale. To understand the impact of bio-coal properties (ash composition, volatile matter and bio-coal structure) and addition in cokemaking, the thermal behavior of bio-coal was investigated under carbonization conditions in TGA and tests in an optical dilatometer were conducted to evaluate the impact on plasticity. The effect from bio-coal addition on coke reactivity was studied in TGA up to 1100°C in carbon dioxide atmosphere, and for technical-scale coke by using a standard test for coke reactivity index. The optical dilatometer results show that plasticity was lowered more with higher bio-coal addition, but pyrolyzed bio-coal had a less negative effect on plasticity compared to torrefied bio-coal with a high content of oxygen. Bio-coke has higher reactivity than reference coke and the bio-cokes containing bio-coal with higher content of ash with higher content of catalytic oxides had higher reactivity. Aiming to reduce the negative effect from bio-coal on coke reactivity related to e.g., bio-coal ash and reactive carbon, possible methods for countermeasures as removal of catalyzing ash oxides by water and acetic acid washing, binding alkaline oxides by kaolin coating, agglomeration to reduce reaction surface and use of a high fluidity coal in the coking coal blend to improve the coke quality were investigated. The coking coal blend containing washed bio-coal had lower dilatation than blends containing original bio-coal, but the bio-coke reactivity was lowered by washing for bio-coke containing bio-coal with higher content of ash and catalytic oxides and lowered more with acetic acid than water washing. The hydrolysis of bio-coal structures during washing increases the surface area and introduces oxygen, having negative effects on thermoplastic properties. The addition of bio-coal with 5% kaolin coating or bio-coal ash addition lowers the dilatation moderately relative to the reference coking coal blend, but the bio-coke reactivity is higher compared to bio-coke with original bio-coal, due to potassium oxide content in kaolin. The bio-cokes containing bio-coal ash have a higher temperature for start of gasification in comparison to introduction of the reactive carbon as present in the bio-coals. Coke containing high fluidity coal has lower reactivity than other reference cokes, and bio-coke containing high fluidity coal with agglomerated bio-coal has lower reactivity when compared with bio-coke produced from another base blend with a similar added amount of bio-coal. The reactivity of coke produced in technical scale measured in CRI/CSR tests shows a similar trend regarding reactivity as measured by TGA on coke produced in laboratory scale. Bio-coke containing agglomerated bio-coal and coking coal blend with high fluidity had the lowest reactivity.It is possible that a bio-coal product suitable for bio-coke production can be produced by combining washing of the raw biomass before torrefaction or pyrolysis with agglomeration before or after thermal treatment. The catalytic compounds in the ash and introduced oxygen during washing are thereby removed, and also the surface area for reaction with CO2 and high porosity for diffusion of reaction gases and products are blocked by compaction.
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| 18. |
- El-Tawil, Asmaa, et al.
(author)
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The Effect of Bio-Coal Agglomeration and High-Fluidity Coking Coal on Bio-Coke Quality
- 2023
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In: Metals. - : MDPI. - 2075-4701. ; 13:1
-
Journal article (peer-reviewed)abstract
- Metallurgical coke with high strength and low reactivity is used in the ironmaking blast furnace. Replacement of some coking coal with bio-coal was shown to result in lower strength and higher reactivity of produced coke due to introduction of reactive bio-coal carbon and ash components catalyzing the Boudouard reaction, but also due to lowering of the coking coal blend fluidity, which influences coke strength and reactivity negatively. The current study aims to investigate the possibility to counteract negative impact from bio-coal addition on fluidity and coke reactivity by using high-fluidity coking coal and by agglomeration of bio-coal before addition. Original bio-coal and micro-agglomerate of bio-coal was added at 10%, 15% and 20% to the coking coal blend. The influence of bio-coals on the coke reactivity was measured by using CO2 in a thermogravimetric analyzer. Selected cokes and bio-cokes were produced in technical scale, and their reactivity and strength were measured in standard tests. The effect on dilatation of adding bio-coal or crushed agglomerates of bio-coal to the coking coal blends was measured in an optical dilatometer. The results show that by using a coking coal blend containing high-fluidity coal with agglomerated bio-coal, the max. contraction is increased, whereas the opposite occurs by using original bio-coal. The results show overlapping between contraction occurring before dilatation and during dilation, which affects max. dilatation. The bio-coke containing high-fluidity coal with agglomerated bio-coal has lower reactivity in comparison to bio-cokes with original bio-coal or bio-coke with agglomerated bio-coal produced from a coking coal blend without high-fluidity coal. The reactivity of coke produced in technical scale, as measured in CRI/CSR tests, shows a similar trend regarding reactivity, as measured by thermogravimetric analysis, on coke produced in laboratory scale.
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| 19. |
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| 20. |
- Hellgren, Simon, et al.
(author)
-
The Characterization of Residues Related to the Roasting– Leaching–Electrowinning Zinc Production Route for Further Metal Extraction
- 2024
-
In: Metals. - : Multidisciplinary Digital Publishing Institute (MDPI). - 2075-4701. ; 14:1
-
Journal article (peer-reviewed)abstract
- Super-hot acid leach residue is generated during zinc production in the roasting–leaching–electrowinning route, where both primary and secondary resources are used as feed material. This residue may contain valuable metals, such as lead, zinc, and iron, as well as precious metals, such as gold and silver. Four materials, namely super-hot acid leach residue, a residue formed when super-hot acid leach residue is selectively leached for lead with triethylenetetramine, as well as flotation concentrate, and flotation tailings formed in a selective silver flotation process with super-hot acid leach residue as the feed material were characterized to obtain a deeper understanding of possible further metal extraction. These four materials were characterized for chemical composition, mineralogy, and mineral distribution via chemical analyses, X-ray diffraction, and energy-dispersive scanning electron microscopy, respectively. The scanning electron microscope images showed that the materials have large variations in particle size distribution and composition. The results showed that the main lead phase in super-hot acid leach residue is lead sulfate, whereas it is mostly converted to lead sulfide during the selective lead leaching of the super-hot acid leach residue. The remaining lead sulfate is found in a solid solution with barium sulfate. Extracting lead from super-hot acid leach residue via triethylenetetramine leaching resulted in increased concentrations of gold and silver by 41% and 42%, respectively. The identified silver phases in super-hot acid leach residue may correspond to silver sulfide, silver chloride, and elementary silver, where silver sulfide was the most commonly occurring silver phase. After leaching this selectively for lead with triethylenetetramine, similar silver phases were identified, but silver sulfide and silver chloride occurred to a similar extent. Additionally, silver copper sulfide was detected. The presence of different silver phases might pose a challenge to reaching high silver recovery during leaching as the optimum leaching conditions differ somewhat. Furthermore, elemental sulfur, with a tendency to coat gold and silver particle surfaces, which is indicated to be present in all materials except the silver flotation tailings, may hinder metal extraction.
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| 21. |
- Hu, Xianfeng, et al.
(author)
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Materials Properties and Liquid Flow in the Hearth of the Experimental Blast Furnace
- 2019
-
In: Metals. - : MDPI. - 2075-4701. ; 9:5
-
Journal article (peer-reviewed)abstract
- The materials’ properties in the hearth of the blast furnace are very crucial for the hearthconditions. In this study, a number of coke, slag, metal, and aggregate samples were collected fromthe hearth of the LKAB’s experimental blast furnace (EBF). Subsequently, the coke, slag, and metalsamples were chemically analyzed by X-ray fluorescence (XRF) or optical emission spectrometer(OES); the aggregate samples were analyzed by scanning electron microscope combined withenergy-dispersive X-ray spectroscopy (SEM/EDS). The possible flow field of the liquid in the EBFhearth before quenching is depicted according to Cu tracers in the metal samples. Selected elementsin the coke, slag, and metal were mapped for two sampling layers in the hearth, as well as in one crosssection of the flow field. The results indicate that there exists an area beneath, and in front of, tuyere 3,where the flow resistance of the liquid was high. The high flow resistance contributed to the formationof a cold zone in the close-to-wall region and at the bottom of the EBF hearth. The temperaturedistribution in the EBF hearth has significant impacts on the chemical properties of the materials indierent positions of the EBF hearth, as well as on the radial and vertical distributions of certainelements/components.
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| 22. |
- Hu, Xianfeng, et al.
(author)
-
Thermal Analysis Study on the Carbothermic Reduction of Chromite Ore with the Addition of Mill Scale
- 2016
-
In: Steel Research International. - : Wiley-VCH Verlag. - 1611-3683 .- 1869-344X. ; 87:5, s. 562-570
-
Journal article (peer-reviewed)abstract
- This paper presents a fundamental study on the carbothermic reduction of chromite ore with the addition of mill scale, which forms the basis for designing an alloying precursor, "chromite ore + mill scale + carbon," for direct chromium alloying. The reduction of chromite ore by petroleum coke with or without the addition of mill scale is investigated by Thermogravimetric Analysis (TGA) under non-isothermal conditions (from room temperature to 1823 K) in the argon atmosphere; the fractional reduced samples were characterized by SEM/EDS and XRD analyses. The experimental results show that the mill scale in the alloying mixture is reduced to high active iron first and disseminated around the chromite ore particles; the reduction of chromite ore is enhanced with the addition of mill scale especially at temperatures higher than 1623 K, and the enhancing effect increased with increasing mill scale addition. The enhancing effect is attributed to the presence of molten Fe-C alloy in the vicinity of chromite ore, which can decrease the thermodynamic activity of chromium by having chromium in situ dissolve into the melt. In this paper, the effect of mill scale addition on the reduction of chromite ore is investigated on the samples with three different amounts of mill scale addition (78 wt%, 38 wt%, and 0 for the samples #1b, #2b, and #3b, respectively) by thermogravimetric technique. The fractional reduced samples are characterized by SEM/EDS and XRD analyses. The mechanism of mill scale addition on the reduction of chromite ore is discussed and the industrial implications of the experimental results are also presented.
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| 23. |
- Hu, Xianfeng, et al.
(author)
-
Thermogravimetric study on carbothermic reduction of chromite ore under non-isothermal conditions
- 2015
-
In: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 42:6, s. 409-416
-
Journal article (peer-reviewed)abstract
- In this paper, the reduction of chromite ore by coke was investigated by means of thermogravimetric analysis under non-isothermal conditions (from room temperature to 1823 K). The fractional reduced samples were examined by SEM/EDS and X-ray diffraction analyses. The experimental results showed that the reduction of iron in the chromite ore started before that of chromium in the ore, and the reduction of chromium and iron in the ore overlapped to some degree. Chromium iron carbide (Cr,Fe)7C3, was found to be the intermediate phase during the reduction, and a chromium gradient was found in the spinel phase of the fractional reduced sample at 1673 K. A four-stage reduction process was proposed: one stage involving the reduction of iron in the chromite ore and three stages involving the reduction of chromium in the ore. The activity aspects of component FeCr2O4 and component MgCr2O4 in the chromite ore were considered. The difficulty in the reduction of the chromite ore is attributed to the fact that, as the reduction proceeds, the activity of the component MgCr2O4 in the fractional reduced ore will decrease to a very low level, which makes further reduction very difficult.
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| 24. |
- Hyllander, Gunilla, et al.
(author)
-
Innovative measurement technique for raceway monitoring
- 2012
-
In: 6th Int. Congress on the Science and Technology of Ironmaking 2012, ICSTI 2012 - Including Proceedings from the 42nd Ironmaking and Raw Materials Seminar, and the 13th Brazilian Symp. on Iron Ore. - 9781627480215 ; , s. 1732-1743
-
Conference paper (peer-reviewed)abstract
- When raceway conditions are changed, e.g blast parameters or selection of injection material, additional measurements and monitoring of raceway can support evaluation of the effects on raceway conditions. Two types of measurement methods have been tested during injection trials with BF flue dust at the SSAB EMEA BF in Oxelösund and the LKAB Experimental Blast Furnace (EBF®). The raceway depth was measured using microwave technique and a camera was installed for viewing the raceway when the peep hole was occupied by the depth measurements equipment. Temperature estimation was made on thermal radiation guided via an optical fibre from the raceway to a spectrometer. Evaluation methods were developed based on Planck radiation law. The measurement techniques and their use for monitoring of raceway conditions are discussed.
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| 25. |
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| 26. |
- Karhu, Marjaana, et al.
(author)
-
D4.3 Circular Economy and zero waste aspects and business models of production
- 2018
-
Reports (other academic/artistic)abstract
- This deliverable reports the survey done in SCRREEN project in Task 4.3 relating to environmental trends and CircularEconomy (CE) aspects of CRM production. For each CRM, the Circular Economy aspects were addressed in order to identifythe gaps that limit performance of the processing chains, hinder closing the loop and hinder a zero-waste CRM production.Information on processes, production, solutions and eco-design principles for closing the loop of raw materials in order tosupport the zero-waste point-of-view, resource efficiency and energy efficiency simultaneously were gathered. In addition, theaspects supporting Circular Economy were evaluated trying to resolve the identified challenges. Lastly, the environmentalissues e.g. toxicity related to CRMs production were reviewed.
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| 27. |
- Leimalm, Ulrika, et al.
(author)
-
Blast furnace pellet properties under different reduction conditions
- 2008
-
In: SCANMET III. - Luleå : MEFOS. - 9789163322693 ; , s. 591-600
-
Conference paper (peer-reviewed)abstract
- Tests in the LKAB Experimental Blast Furnace (EBF) were carried out under different pre-set process conditions. The choice of injection coal, an HV coal and an LV coal, affected the in-furnace conditions, which was assumed to contribute to the differences in reduction degree in pellets taken out with the upper shaft probe. A higher pellet reduction degree was attained during operation with the HV coal compared to injection of the LV coal. The differences in pellet reduction degree receded through the shaft and no correlation between pellet reduction degree and pre-set process conditions was observed in samples taken out with the lower shaft probe. For the HV coal, a higher pellet strength and an increase in Fe and C losses with the top gas were observed compared to operation with the LV coal. Blast-furnace-simulating laboratory reduction for simulated PCR, based on measurements in the EBF, was carried out. The increase in reduction potential and temperature level resulting from an increase in simulated PCR compensated for the decrease in reduction time between the simulated low and high PCR. Laboratory reduction under isothermal conditions showed an increased reduction rate at increased temperature as well as with an increased H2 content in the reduction gas.
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| 28. |
- Leimalm, Ulrika, et al.
(author)
-
Blast furnace pellet textures during reduction and correlation to strength
- 2010
-
In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 50:10, s. 1396-1405
-
Journal article (peer-reviewed)abstract
- The blast furnace is the most common means of producing hot metal. As the amounts of reduction agents increases, which influence in-furnace conditions such as ascending gas properties, temperature profiles and the ore-to-coke ratio, new demands are put on the iron-bearing material in terms of both reducibility and mechanical strength. To investigate the possibilities to use the Pellet Multi Press (PMP) equipment for compression strength measurements of reduced pellets and to gain a deeper understanding of the correlation between pellet texture and strength, an initial study of pellets taken from the LKAB Experimental Blast Furnace (EBF) was conducted. Furthermore, the pellet pieces generated after compression tests were characterized using light optical microscopy. In order to correlate the texture of pellet pieces to the pellet texture prior to breakage, a characterization of the chronological pellet texture development during reduction in the EBF was performed. The original pellet texture remained in the beginning of reduction and differences receded through the EBF shaft as wustite and Femet was formed. Occurrence of Femet in the pellet texture increased the compression strength, while less reduced and less sintered textures showed the reverse effect. So far, the results from compression strength tests indicate that disintegration of pellets takes place at a reaction front, at the transition between different texture types of iron oxide or at the location of a visible surface crack. © 2010 ISIJ.
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| 29. |
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| 30. |
- Leimalm, Ulrika, et al.
(author)
-
Effect of different PCI practice on the texture obtained during reduction of iron oxide pellets
- 2008
-
In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 48:12, s. 1686-1695
-
Journal article (peer-reviewed)abstract
- In modern blast furnace ironmaking, producers continuously strive to reduce coke consumption by replacing coke with e.g., an increased amount of injected pulverized coal. A change in pulverized coal injection rate (PCR) and injection coal type will influence the in-furnace conditions and thus the reduction of iron oxides. In the present study, the reduction behaviour of olivine pellets and textures formed were investigated in the LKAB Experimental Blast Furnace (EBF) and in laboratory scale. In the EBF, effects of injection of an low-volatile (LV) and an high-volatile (HV) coal type at different PCR while two types of oxygen supply methods were employed were investigated. The choice of injection coal type was conclusive for the Femet texture formed during reduction, extent of Femet carburization and K distribution in the pellets. The amount of volatile matters in the coal type had a greater effect on the reduction properties than the PCR and oxygen supply method. Laboratory experiments simulating PCR, based on measurements in the EBF, showed that the initial reduction conditions, in terms of temperature level and reduction gas composition, determined the pellet texture up to a reduction degree of at least 60%. The tests carried out in the EBF showed that the pellets were well suited for blast furnace reduction under all the investigated process conditions. The laboratory tests supported this conclusion. © 2008 ISIJ.
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| 31. |
- Leimalm, Ulrika, et al.
(author)
-
Effect of simulated PCI rate on olivine pellet reduction
- 2006
-
In: The 4th international congress on the science and technology of ironmaking (ICSTI '06). - Tokyo : The Iron and Steel Institute of Japan. - 4930980569
-
Conference paper (peer-reviewed)abstract
- Reduction behaviour and textures formed during laboratory simulated BF tests with olivine pellets are presented and discussed. Test design is based on gas and temperature profiles during operation at a high and a low pulverized coal injection (PCI) rate with a low-volatile coal in the LKAB experimental blast furnace (EBF). Texture differences, introduced prior to a reduction degree of 40 percent, are observed in the iron oxide in the pellet core and in the Femet pellet periphery. A simulated high PCI rate decreases the reduction time of the pellets. The olivine pellets investigated are well suited for blast furnace operation at different PCI rates and accordingly different production rates.
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| 32. |
- Leimalm, Ulrika, et al.
(author)
-
Off-gas dust in an experimental blast furnace part 1: Characterization of flue dust, sludge and shaft fines
- 2010
-
In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 50:11, s. 1560-1569
-
Journal article (peer-reviewed)abstract
- In blast furnace (BF) ironmaking, efforts are made to decrease coke consumption, which can be done by increasing the pulverized coal injection rate (PCR). This will cause changes in ¡n-furnace reduction conditions, burden distribution, demands on raw material strength, etc. In order to maintain stable operation, but also to obtain low amounts of material losses through the off-gas, it is important to understand fines generation and behaviour in the BF Off-gas dust and shaft fines generated in the LKAB Experimental Blast Furnace (EBF) were sampled during operation with olivine pellets and mixtures of acid pellets and sinter as iron-bearing materials. Characterization using XRD, SEM and LOM was focused on fines from iron-bearing materials, coke and slag formers. The results showed that flue dust, mainly <0.5 mm, was mechanically formed and created in the same manner for all investigated samples. Carbon-containing particles dominated in the fractions >0.075 mm and consisted mainly of coke particles from the shaft. Fe-containing particles, as Fe2O 3 from the top of the shaft, formed the major part of flue dust fractions <0.063 mm. Particles from slag formers such as quartzite and limestone were observed in flue dust when slag formers were utilized in the feed. Sludge consisted mainly of chemically formed spherical particles <1 μm precipitated from the ascending gas as the temperature decreased. © 2010 ISIJ.
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| 33. |
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| 34. |
- Lundgren, Maria, et al.
(author)
-
Coke reactivity under blast furnace condition and in the CSR/CRI test
- 2008
-
In: SCANMET III. - Luleå : MEFOS. - 9789163322709 ; , s. 125-134
-
Conference paper (peer-reviewed)abstract
- The present work aims to study the high-temperature strength of coke. Mechanisms of disintegration were evaluated using basket samples charged into LKAB's experimental blast furnace prior to quenching and dissection. Coke charged into basket samples were analysed with CSR/CRI tests and compared with treated coke from the blast furnace. Results from tumbling tests, chemical analyses of coarse and fine material, as well as light optical microscopy studies of original and treated coke have been combined and evaluated.The results indicate a correlation between the ash composition and the CSR values. Differences in the texture of the coke were noted with light optical microscopy, and a significant change in the coke texture during the CSR/CRI test conditions was found. The results suggest that the main reaction between coke and CO2 took place in isotropic areas, which was especially pronounced in coke with a low CSR. Signs of degradation were apparent throughout the coke pieces that have undergone CSR/CRI testing, but were less observable in coke reacted in the blast furnace. The results indicate that reaction with CO2 is generally limited by the chemical reaction rate in the CSR/CRI test, while in the blast furnace the reaction is limited by the diffusion rate. Coke degradation is therefore mostly restricted to the coke surface in the blast furnace.
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| 35. |
- Lundgren, Maria, et al.
(author)
-
Coke reactivity under blast furnace conditions and in the CSR/CRI test
- 2009
-
In: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 80:6, s. 396-401
-
Journal article (peer-reviewed)abstract
- The present work aims to study the high-temperature strength of coke. Mechanisms of disintegration were evaluated using basket samples charged into LKAB's experimental blast furnace prior to quenching and dissection. Coke charged into basket samples was analysed with CSR/CRI tests and compared with treated coke from the blast furnace. Results from tumbling tests, chemical analyses of coarse and fine material, as well as light optical microscopy studies of original and treated coke have been combined and evaluated. The results indicate a correlation between the ash composition and the CSR values. Differences in the texture of the coke were noted with light optical microscopy, and a significant change in the coke texture during the CSR/CRI test conditions was found. The results suggest that the main reaction between coke and CO2 took place in isotropic areas, which was especially pronounced in coke with a low CSR. Signs of degradation were apparent throughout the coke pieces that have undergone CSR/CRI testing, but were less observable in coke reacted in the blast furnace. The results indicate that reaction with CO2 is generally limited by the chemical reaction rate in the CSR/CRI test, while in the blast furnace the reaction is limited by the diffusion rate. Coke degradation is therefore mostly restricted to the coke surface in the blast furnace.
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| 36. |
- Lundgren, Maria, et al.
(author)
-
Coke reactivity under blast furnace conditions and in the CSR/CRI test
- 2009
-
In: Steel Research International. ; , s. 396-401
-
Conference paper (peer-reviewed)abstract
- The present work aims to study the high-temperature strength of coke. Mechanisms of disintegration were evaluated using basket samples charged into LKAB's experimental blast furnace prior to quenching and dissection. Coke charged into basket samples was analysed with CSR/CRI tests and compared with treated coke from the blast furnace. Results from tumbling tests, chemical analyses of coarse and fine material, as well as light optical microscopy studies of original and treated coke have been combined and evaluated. The results indicate a correlation between the ash composition and the CSR values. Differences in the texture of the coke were noted with light optical microscopy, and a significant change in the coke texture during the CSR/CRI test conditions was found. The results suggest that the main reaction between coke and CO 2 took place in isotropic areas, which was especially pronounced in coke with a low CSR. Signs of degradation were apparent throughout the coke pieces that have undergone CSR/CRI testing, but were less observable in coke reacted in the blast furnace. The results indicate that reaction with CO 2 is generally limited by the chemical reaction rate in the CSR/CRI test, while in the blast furnace the reaction is limited by the diffusion rate. Coke degradation is therefore mostly restricted to the coke surface in the blast furnace.
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| 37. |
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| 38. |
- Lundgren, Maria, et al.
(author)
-
High temperature coke characteristics in the blast furnace : evaluation of coke properties in the raceway area
- 2012
-
In: Scanmet IV. - Luleå : MEFOS. - 9789163708596 ; , s. 157-168
-
Conference paper (peer-reviewed)abstract
- Core-drilling into the coke bed of raceway and hearth has been performed in the LKAB Experimental Blast Furnace (EBF®) during short stoppages aiming to characterize raceway conditions corresponding to different operational conditions. All coke operation, injection of pulverized coal and injection of a mixture of coal and blast furnace flue dust (BFD) were evaluated and compared. The samples have been studied regarding particle size and distribution, coke have been evaluated with chemical composition and thermal history, i.e. coke graphitization degree. In addition, the results have been compared to drilled raceway core samples from SSAB industrial blast furnace in Luleå. Coke in drill-cores consists of bosh, raceway and deadman coke. In comparison with charged coke this coke has changed characteristics depending on the exposed conditions which vary along the radius of each drilled core. Coke in raceway area has increased ash content due to gasification of C and the ash composition is altered due to both reduction and gasification of ash minerals as e.g. SiO2 and alkalis in raceway and oxidation/condensation of gaseous compounds and uptake of compounds from the melt. Coke exposed to highest temperatures in the raceway area have increased the most in graphitization degree, and subsequent bird’s nest and deadman cokes graphitization degrees decreases. K2O-content in coke correlates to the graphitization degree as well as the SiO2/Al2O3 quotient which decreases at higher temperatures. Presence of slag and coke aggregates indicates the formation of bird’s nests at the end of the raceway. The end of raceway and position of a significant bird's nest in the industrial samples are indicated by the increasing content of K2O and increasing ratio of SiO2/Al2O3 in coke. In the industrial BF the pronounced formation of a bird’s nest redirect the gas from moving towards the BF center. As a result the coke in deadman cannot be heated and the temperature indicated by the graphitization degree decreases.Injection of BFD influences the raceway conditions as the combustion peak is moved further into the raceway when BFD and PC mix are injected. Analyze of fines shows remaining unreacted BFD, which contains iron oxide with oxidation degree between FeO and metallic Fe. Increased FeO-content in raceway will decrease the melting point of tuyere slag and therefore improve the permeability at raceway end and the fact that the core when drilled could be pushed further into the EBF than for the other cores indicates higher permeability after injection of PC and BFD mixture.
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| 39. |
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| 40. |
- Lundgren, Maria, et al.
(author)
-
Off-gas dust in an experimental blast furnace part 2: Relation to furnace conditions
- 2010
-
In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 50:11, s. 1570-1580
-
Journal article (peer-reviewed)abstract
- In the blast furnace process, material losses are caused by particles that are blown out of the furnace by the off-gas. In order to reduce these losses, it is important to understand the correlations between furnace conditions and off-gas dust formation. Off-gas dust, as flue dust and sludge, were collected during shaft probe sampling in LKAB Experimental Blast Furnace (EBF). Process data was used to evaluate the relationship between off-gas dust amounts and furnace conditions. The graphitization degree (Lc value) of shaft coke and coke in flue dust was determined using XRD measurements. Solution loss in the shaft had a negligible effect on coke degradation and the coke particles which ended up in the flue dust were mainly derived from abrasion at low temperatures. The amount of alkali and SiO2 in sludge increased with higher PCR and flame temperature, which confirmed that submicron spherical particles in sludge originated from the high temperature area around the raceway. Theoretical critical particle diameters of materials, which could be blown out with the off-gas, were estimated. Flow conditions in the top of the shaft as well as and the properties of fine particles in terms of size and density are important when outflow of mechanical dust, such as flue dust, is concerned. Low off-gas temperatures, and thus lower off-gas velocities, are favourable for low flue dust amounts expelled from the blast furnace. © 2010 ISIJ.
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| 41. |
- Lundgren, Maria, et al.
(author)
-
The Evolution of Structural Order as a Measure of Thermal History of Coke in the Blast Furnace
- 2014
-
In: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 45:2, s. 603-616
-
Journal article (peer-reviewed)abstract
- Investigations were carried out on cokes heat treated in the laboratory and on cokes extracted from the experimental blast furnace (EBF) raceway and hearth. X-ray diffraction (XRD) measurements were performed to investigate changes in structural order (Lc), chemical transformations in coke ash along with comparative thermodynamic equilibrium studies and the influence of melt. Three data processing approaches were used to compute Lc values as a function of temperature and time and linear correlations were established between Lc and heat treatment temperatures during laboratory investigations. These were used to estimate temperatures experienced by coke in various regions of EBF and estimated raceway temperatures were seen to follow the profile of combustion peak. The MgAl2O4 spinel was observed in coke submerged in slag during laboratory studies and in cokes found further into the raceway. Coke in contact with hot metal showed XRD peaks corresponding to presence of Fe3Si. The intensity of SiO2 peak in coke ash was seen to decrease with increasing temperature and disappeared at around 1770 K (1500 °C) due to the formation of SiC. This study has shown that the evolution of structural order and chemical transformations in coke could be used to estimate its thermal history in blast furnaces.
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| 42. |
- Mousa, Elsayed, et al.
(author)
-
Reduced Carbon Consumption and CO2 Emission at the Blast Furnace by Use of Briquettes Containing Torrefed Sawdust
- 2019
-
In: Journal of Sustainable Metallurgy. - : Springer. - 2199-3823 .- 2199-3831. ; 5:3, s. 391-401
-
Journal article (peer-reviewed)abstract
- Lowering the carbon consumption and fossil CO2emissions is a priority in blast furnace (BF) ironmaking. Renewablebiomass is one option that can play an important role in future low-carbon ironmaking particularly in the countries rich inbiomass resources. In this study, full-scale trials to investigate the impact of briquettes containing torrefied sawdust on theBF efficiency and process stability have been conducted. Briquettes containing 1.8% of torrefied pelletized sawdust (TPS),86.2% of steel mill residues, and 12% cement with sufficient mechanical strength have been produced on industrial scale. Thebio-briquettes were charged at two different rates: 37% ( ~ 39 kg/tHM) and 55% ( ~ 64 kg/tHM) bio-briquettes to the SSABBF No. 4 in Oxelösund. The gas utilization was higher during bio-briquette-charging periods without change in pressuredrop up to 55% bio-briquettes, indicating sustained shaft permeability. BF dust generation or properties did not change significantly.Measurements of the top gas composition using mass spectrometry did not indicate release of hydrocarbon fromTPS in connection to the charging of bio-briquettes. Evaluation of process data has been carried out using a heat and massbalance model. The evaluation of operational data in the model indicated lowering of thermal reserve zone temperature by45 °C and reduction in carbon consumption by ~ 10 kg/tHM when charging 55% bio-briquettes compared to the referencecase. The total CO2emission was reduced by about 33–40 kg/tHM when using 55% bio-briquettes.
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| 43. |
- Orre, Joel, et al.
(author)
-
Understanding of Blast Furnace Performance with Biomass Introduction
- 2021
-
In: Minerals. - : MDPI. - 2075-163X. ; 11:2
-
Journal article (peer-reviewed)abstract
- The blast furnace still dominates the production and supply of metallic units for steelmaking. Coke and coal used in the blast furnace contribute substantially to CO2 emissions from the steel sector. Therefore, blast furnace operators are making great efforts to lower the fossil CO2 emissions and transition to fossil-free steelmaking. In previous studies the use of pre-treated biomass has been indicated to have great potential to significantly lower fossil CO2 emissions. Even negative CO2 emission can be achieved if biomass is used together with carbon capture and storage. Blast furnace conditions will change at substantial inputs of biomass but can be defined through model calculations when using a model calibrated with actual operational data to define the key blast furnace performance parameters. To understand the effect, the modelling results for different biomass cases are evaluated in detail and the overall performance is visualised in Rist- and carbon direct reduction rate (CDRR) diagrams. In this study injection of torrefied biomass or charcoal, top charging of charcoal as well as the use of a combination of both methods are evaluated in model calculations. It was found that significant impact on the blast furnace conditions by the injection of 142 kg/tHM of torrefied biomass could be counteracted by also top-charging 30 kg/tHM of charcoal. With combined use of the latter methods, CO2-emissions can be potentially reduced by up to 34% with moderate change in blast furnace conditions and limited investments.
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| 44. |
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| 45. |
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| 46. |
- Robinson, Ryan, et al.
(author)
-
Recycling of by-product pellets as burden in the blast furnace process : a lab and pilot scale investigation
- 2004
-
In: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 75:2, s. 99-105
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Journal article (peer-reviewed)abstract
- Cold bonded by-product briquettes have been recycled in the blast furnace at SSAB Tunnplat in Lulea since 1993. Recently, much effort has been made to increase the recycling of by-products. One such project deals with the development of a cold bonded by-product pellet (CBP) agglomerated from very fine dusts. The pellets used in these tests are produced from a blend containing BF flue dust, filter dust, briquette fines and BOF coarse dust as well as cement binder. The pellets were tested in the laboratory by reduction tests, softening and melting tests, thermo gravimetric analysis, differential thermo analysis, and mass spectrometry measurements. The test results indicate that the CBPs can disintegrate during reduction in the BF shaft, are self-reducing to a high extent and, as a supplement to the normal ferrous burden, they show quite good softening and melting properties. A pilot scale test in LKAB's experimental blast furnace was performed. CBPs were charged with rates of 150 kg/tHM, 299 kg/tHM and 344 kg/tHM respectively during test periods 1, 2 and 3. The blast furnace operation was very stable during test period 1 with 150 kg CBP/tHM, but the burden descent and gas distribution were disturbed during the periods with greater CBP burden content. The rate of reducing agents was significantly decreased and slag amount was increased when CBPs were charged.
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| 47. |
- Sar, Suchandra, et al.
(author)
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Characterization of Double Leached Waelz Oxide for Identification of Fluoirde Mineral
- 2019
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In: Metals. - : MDPI. - 2075-4701. ; 9:3
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Journal article (peer-reviewed)abstract
- Double leached Waelz oxide (DLWO), with 76% zinc, is a secondary zinc containing raw materials obtained by the treatment of electric arc furnace dust. The content of fluoride in DLWO is still too high for direct leaching, as fluoride has a detrimental effect on electrowinning for zinc production. Knowledge of the characteristics of DLWO, and especially on how a fluoride mineral might exist, can contribute to further improvement of the selective leaching for the removal of fluoride. In this study, DLWO was characterized using analytical techniques, such as inductively coupled plasma-optical emission spectroscopy (ICP-OES), 19F liquid-state nuclear magnetic resonance (19F LS NMR), X-ray powder diffraction analysis (XRD), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) and 19F solid-state nuclear magnetic resonance (19F SS NMR). This study showed that DLWO mainly consisted of zincite (ZnO), cerussite (PbCO3) and a spinel containing zinc, iron and manganese. The fluoride mineral identified was calcium fluoride (CaF2). In SEM analysis, fluorine was found in larger grains together with calcium and oxygen, which was possibly calcium carbonate.
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| 48. |
- Sar, Suchandra, et al.
(author)
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Experimental Study on the Dissolution Behavior of Calcium Fluoride
- 2020
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In: Metals. - : MDPI. - 2075-4701. ; 10:8
-
Journal article (peer-reviewed)abstract
- The presence of halogens has an adverse effect on the zinc extraction process through electrowinning, the last phase of the RLE (Roasting, Leaching and Electrowinning) zinc extraction route. Fluoride (F−) may be present as calcium fluoride (CaF2) and this is, for example, the case in double leached Waelz oxide (DLWO). Efficient removal of F− from primary and secondary raw materials for zinc extraction results in a simplified process and increases flexibility in the selection of raw materials. Understanding of the solubility behavior of pure CaF2 can give valuable information on treatment for maximized halogen removal. Dissolution of CaF2 was studied with the addition of sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3). Dissolution studies were combined with thermodynamic calculations to understand the solubility behavior of CaF2 under different conditions. Results from the experiments and the thermodynamic calculations show that Na2CO3 and NaHCO3 have similar behavior if the pH is controlled at the same value. The available carbonate (CO32−) ion in the system limits the concentration of calcium (Ca2+) ion by precipitation of CaCO3, which enhances the dissolution of CaF2. At higher temperatures and pH, calcite, vaterite, and aragonite were formed and co-precipitation of CaF2 along with calcium carbonate (CaCO3) was observed. At lower temperatures and lower pH levels, only calcite and vaterite were formed and a coating by CaCO3 on CaF2 was found to hinder complete dissolution reaction. The results of this study indicate that the temperature along with the reagents used for the dissolution tests have a significant impact on the CaCO3 polymorph mixture (calcite, vaterite and aragonite) formation.
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| 49. |
- Sundqvist Ökvist, Lena, et al.
(author)
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Experiences of Bio-Coal Applications in the Blast Furnace Process—Opportunities and Limitations
- 2021
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In: Minerals. - : MDPI. - 2075-163X. ; 11:8
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Journal article (peer-reviewed)abstract
- Metal production, and especially iron ore-based steel production, is characterized by high fossil CO2 emissions due of the use of coal and coke in the blast furnace. Steel companies around the world are striving to reduce the CO2 emissions in different ways, e.g., by use of hydrogen in the blast furnace or by production of iron via direct reduction. To partially replace fossil coal and coke with climate neutral bio-coal products that are adapted for use in the metal industry, e.g., at the blast furnace, is a real and important opportunity to significantly lower the climate impact in a short-term perspective. Top-charging of bio-coal directly to the blast furnace is difficult due to its low strength but can be facilitated if bio-coal is added as an ingredient in coke or to the mix when producing residue briquettes. Bio-coal can also be injected into the lower part of the blast furnace and thereby replace a substantial part of the injected pulverized coal. Based on research work within Swerim, where the authors have been involved, this paper will describe the opportunities and limitations of using bio-coal as a replacement for fossil coal as part of coke, as a constituent in residue briquettes, or as replacement of part of the injected pulverized coal. Results from several projects studying these opportunities via technical scale, as well as pilot and industrial scale experiments and modelling will be presented. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
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| 50. |
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