| 1. |
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| 2. |
- 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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| 3. |
- 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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| 4. |
- El-Tawil, Asmaa A., et al.
(author)
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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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| 5. |
- 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
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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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| 6. |
- El-Tawil, Asmaa
(author)
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Bio-coal as an alternative reducing agent in the blast furnace
- 2020
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Licentiate thesis (other academic/artistic)abstract
- The steel industry is aiming to reduce CO2 emissions by different means; in the short-term, by replacing fossil coal with highly reactive carbonaceous material like bio-coal (pretreated biomass) and, in the longer term, by using hydrogen. The use of bio-coal as part of top charged briquettes also containing iron oxide has the potential to lower the thermal reserve zone temperature of the Blast furnace (BF) and, due to improved gas efficiency, thereby give a high replacement ratio to coke.In order to select a suitable bio-coal to be contained in agglomerates with iron oxide, the current study aims at investigating the devolatilization behavior and related kinetics of different types of bio-coals. In addition, the aim is to investigate the self-reduction behavior of bio-coal-containing iron ore composite under inert condition and simulated blast furnace thermal profile.In the BF the temperature of the top-charged material will increase rather quickly during the descent in the upper part. Ideally, all the carbon and hydrogen contained in the top-charged bio-coal should contribute to the reduction. The devolatilization of bio-coal is thus important to understand and to compare between different types of bio-coal.To explore the devolatilization behavior for different materials, a thermogravimetric analyzer equipped with a quadrupole mass spectrometer was used to monitor the weight loss and off-gases during non-isothermal tests for bio-coals having different contents of volatile matter. The samples were heated in an inert atmosphere up to 1200°C at three different heating rates: 5, 10 and 15°C/min. The thermogravimetric data were evaluated by using the Kissinger–Akahira–Sonuse (KAS) iso-conversational model and the activation energy was determined as a function of the conversion degree. Bio-coals with both low and high content of volatile matter can produce reducing gases that can contribute to the reduction of iron oxide in bio-agglomerates. Bio-coals containing a higher content of catalyzing components such as CaO and K2O will enhance the devolatilization and release of volatile matter at a lower temperature. The self–reduction of composites was investigated by thermogravimetric analyses in argon atmosphere up to 1100°C and evolved gases were monitored by means of quadrupole mass spectroscopy. Composites with and without 10% bio-coal and sufficient coke breeze to keep the C/O molar ratio equal to one were mixed and Portland cement was used as a binder. To explore the effect of added bio-coals, interrupted vertical tube furnace tests were conducted in a nitrogen atmosphere at temperatures selected based on thermogravimetric results, using a similar thermal profile as for the thermogravimetric analyzer. The variation between fixed carbon, volatile matter contents and ash composition for different types of bio-coal influences the reduction of iron oxide.The results showed that the self-reduction proceeds more rapidly in the bio-coal-containing composite and that the volatile matter could have contributed to the reduction. 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 using coke.Use of bio-coal with high content of volatile matter but low content of catalyzing elements as potassium, sodium and calcium in bio-agglomerates for the BF can be recommended because it enhances the self-reduction of iron oxide, e.g., wustite was detected by XRD analysis in samples treated up to 680°C. Bio-coal with low content of volatile matter, low alkalis, low phosphorous and high content of fixed carbon will also be suitable to use in the BF.
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| 7. |
- 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
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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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| 8. |
- El-Tawil, Asmaa
(author)
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Influence of the properties of bio-coal as a substitute for fossil coal in carbon composite agglomerates and in coke
- 2022
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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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| 9. |
- 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
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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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| 10. |
- Mousa, Elsayed, et al.
(author)
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Reduced Carbon Consumption and CO2 Emission at the Blast Furnace by Use of Briquettes Containing Torrefed Sawdust
- 2019
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In: Journal of Sustainable Metallurgy. - : Springer. - 2199-3823 .- 2199-3831. ; 5:3, s. 391-401
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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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