Microstructure and Phase of Carbon Brick and Protective Layer of a 2800 m&lt;sup&gt;3&lt;/sup&gt; Industrial Blast Furnace Hearth

Niu, Qun; Cheng, Shusen; Xu, Wenxuan; Niu, Weijun

doi:10.2355/isijinternational.isijint-2019-029

Cited by 16 publications

(22 citation statements)

References 25 publications

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“…As shown by XRD results, the formation of leucite led to the destruction of the coke structure due to the volume expansion caused by the reaction. Previous studies have shown that this reaction is accompanied by a volume expansion of 15–36% . The three-dimensional morphology of the deadman coke sample is shown in Figure .…”

Section: Discussion and Analysismentioning

confidence: 90%

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Graphitization and Performance of Deadman Coke in a Large Dissected Blast Furnace

et al. 2021

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The graphitization and performance of deadman coke in the blast furnace hearth have an essential influence on the longevity of the blast furnace. In this paper, coke samples were obtained from various heights in a hearth during the overhaul of the blast furnace. The voidage, particle size, graphitization degree, microstructure, and structure evolution of multiple cokes were analyzed through digital image processing, XRD, Raman spectra, scanning electron microscopy, and energy-dispersive X-ray spectroscopy (SEM-EDS). The graphitization results were compared with feed coke, tuyere coke, cohesive zone coke, and deadman coke in reference, and the main findings were analyzed. The following results were obtained. First, the voidage of deadman coke increased and then decreased with the increase of the depth while the particle size continued to decrease. In addition, the consumption rate of coke as a carburizer, reductant, and heart source was 8.47, 30.95, and 60.58%, respectively. Second, the graphitization degree of deadman coke was extremely high and showed a trend of first increasing and then decreasing. Finally, the evolution mechanism of coke graphitization was proposed. Molten iron, alkali metal, temperature, and mineral were the crucial factors that affect the graphitization of coke. The turning point of the graphitization degree was related to the buoyancy of the hearth.

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Section: Discussion and Analysismentioning

confidence: 90%

“…Previous studies have shown that this reaction is accompanied by a volume expansion of 15−36%. 35 The three-dimensional morphology of the deadman coke sample is shown in Figure 10. The samples were not polished, the actual microstructure and fracture morphology was reflected.…”

Section: Discussion and Analysismentioning

confidence: 99%

Graphitization and Performance of Deadman Coke in a Large Dissected Blast Furnace

et al. 2021

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“…Deng et al [ 12 ] proved that molten zinc flows to the brittle layer of carbon bricks and solidifies; the carbon bricks become easy to break at the brittle layer. Niu et al [ 13 ] analyzed the minerals of the hot surface of the carbon brick and proposed that the macrocracks that resulted from KAlSiO 4 , KAlSi 2 O 6 , Zn 2 SiO 4 , and ZnAl 2 O 4 are the inducements of the formation of the brittle layer, and the main reason for the formation of macrocracks and brittle layer in carbon brick is the continuous accumulation of ZnO in microcracks. Fan et al [ 14 ] proved that the local expansion of volume caused by the introduction of harmful elements leads to the erosion of the refractory, whereas the enhanced erosion from the throat to the bottom of the furnace can be explained by the increasing temperature.…”

Section: Introductionmentioning

confidence: 99%

Occurrence State and Behavior of Carbon Brick Brittle in a Large Dissected Blast Furnace Hearth

Guo

Zhang

Jiao

et al. 2021

steel research int.

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The thickness of the carbon bricks is one of the important factors of the longevity of the blast furnace. Herein, a large number of brittle carbon bricks in the hearth sidewall and the continuous rectangle‐shape floating refractory in residual iron are found during the blast furnace hearth dissection. The occurrence state of the carbon brick is characterized through chemical analysis, X‐ray diffraction (XRD), and scanning electron microscope (SEM)–energy‐dispersive X‐ray spectroscopy (EDS). The contents of K, Na, Cl, Zn, and Fe in brittle carbon bricks are relatively high, and a large number of large‐scale Al2O3 phases and nepheline appear in the floating carbon brick. It indicates that K, Na, Cl, Zn, and Fe are major causes for the serious erosion of the carbon brick, and the floating carbon brick may come from brittle carbon bricks on the sidewall. In addition, the source of Al2O3 and the consumption pathway of SiO2 and ZnO in floating refractory in residual iron are analyzed. Finally, the disappearing mechanism of carbon brick is proposed, which is that the carbon bricks floated up to the tuyere and burnt.

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“…Willemite (Zn 2 SiO 4 ) and zinc aluminate (ZnO•Al 2 O 3 ), which are considered as furnace accretions, are formed when zinc oxidizes on the surface of the lining. [4][5][6] Zinc atoms have a large particle weight and a small particle radius, which allow them to enter into the lining of the furnace at high temperatures and oxidize, resulting in the expansion of the lining. The zinc circulation induces heat transfer from high temperature zones to low temperature zones.…”

Section: Introductionmentioning

confidence: 99%

Erosion of Carbon Brick by Zinc in Hearth of Blast Furnace

et al. 2020

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The service life of a blast furnace (BF) is affected by the accumulation of zinc. To clarify the erosion mechanism of the carbon bricks, due to the zinc action, a dissection investigation of a commercial BF was carried out. The results show that the zinc content reaches up to 10.59% in the tuyere coke. The carbon bricks were sampled in a region characterized by high erosion levels and molten iron was detected. More interestingly, zinc was detected between the molten iron and the carbon bricks: the high zinc content of the bosh gas of the BF induces the zinc vapor to penetrate into the molten iron surface. The zinc vapor and the molten iron mix together, and zinc migrates from the molten iron into the carbon bricks. The thermodynamic behavior of zinc was analyzed and the volume expansion rate (56.94%) was calculated when Zn oxidizes into ZnO. The oxidation process may be the main reason behind the carbon brick erosion. The results show that molten zinc flows to the brittle layer of the carbon bricks, and finally solidifies, the carbon bricks become easy to break at the brittle layer. Countermeasures to reduce the harm of zinc have been suggested based on the zinc balance calculation.

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Microstructure and Phase of Carbon Brick and Protective Layer of a 2800 m<sup>3</sup> Industrial Blast Furnace Hearth

Cited by 16 publications

References 25 publications

Graphitization and Performance of Deadman Coke in a Large Dissected Blast Furnace

Graphitization and Performance of Deadman Coke in a Large Dissected Blast Furnace

Occurrence State and Behavior of Carbon Brick Brittle in a Large Dissected Blast Furnace Hearth

Erosion of Carbon Brick by Zinc in Hearth of Blast Furnace

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