Analysis of the Alkali Flow in Ironmaking Reactors by a Thermochemical Approach: Blast Furnace

Self Cite

The furnace campaign of a blast furnace represents an important factor for the iron-making industry due to the fact that maintenance such as relining is not only costly but also time consuming. The furnace campaign is largely determined by the functionality of the lining, which is influenced by wear mechanisms and the damaging behavior of certain elements.To these unwanted elements that may attack the lining belong, for example, Zinc (Zn), Lead (Pb), Potassium (K), and Chlorine (Cl). In this paper, the distribution of Zn, Pb, K, and Cl within the lining of a blast furnace at the end of its furnace campaign is investigated and discussed. The results demonstrate that the content of some elements (Zn, Cl, Pb) in the lining and also their penetration depth significantly varies over the blast furnace height. For Zn and Pb, the highest contents (43 g Zn kg À1 and 0.14 g Pb kg À1 ) are observed in the inner lining stones (adjacent to the hot metal), whereas for Cl, a contrary distribution pattern is observed. The highest contents are detected in the outer stones of the lining at the top of the blast furnace.

Section: Resultsmentioning

confidence: 52%

Distribution of Zn, Pb, K, and Cl in Blast Furnace Lining

Trinkel

Aschenbrenner

Thaler

et al. 2016

Self Cite

“…As shown in Equation (1), K can continue to react to form KAlSiO 4 , resulting in a volume expansion of 39%, which is similar to the 36% volume expansion in Anton Pichler. [ 19 ] Therefore, the occurrence of reactions 1, 2, 5, 6, and 8 will cause volume expansion and destroy the carbon brick structure. In the erosion of harmful elements in blast furnaces, leucite (KAlSi 2 O 6 ) and sodium‐nepheline (NaAlSiO 4 ) are often found in carbon bricks, so the local volume expansion degree is calculated by this method to be 44% and 45%.

$$2 \text{K} \left(\right.

…”

Section: Resultsmentioning

confidence: 99%

Formation Mechanism of the Brittle Layer in Carbon Brick of Blast Furnace Hearth

Cao

Kidane

Zhang

et al. 2023

The brittle layer of carbon brick in a Chinese 4000 m3 blast furnace hearth is investigated in detail, and its formation mechanism is proposed correspondingly. The occurrence form of the brittle layer in carbon brick is characterized by chemical analysis, X‐ray diffraction, and scanning electron microscopy–energy dispersive spectroscopy. The results show that obvious harmful element (K, Na, and Zn) erosion on the sidewall of the blast furnace hearth is observed, in which Zn erosion is dominant. The K2O, Na2O, and KCl produced in the carbon brick by K and Na are the inducement of the brittle layer formation, and the ZnO formed by Zn is the main reason for the brittle layer formation. The thermal stress caused by temperature gradients in carbon brick is greater than its bending strength, which will increase the microcracks in carbon brick. The brittle layer has a lower thermal conductivity due to higher porosity, resulting in a large temperature difference. The resulting thermal stress will aggravate the embrittlement degree.

“…The generation of new phases caused the volume expansion of the carbon brick. Previous studies have shown that the transformation from liquid potassium to kalsilite is accompanied by a volume expansion of about 36%, [ 22,24 ] which provides more favorable conditions for the generation of cracks and formation of the brittle zone.

2 K (l) + CO (g) + {3 Al}_{2} {normalO}_{3} \cdot {2 SiO}_{2} (s) = {2 KAlSiO}_{4} (s) + {2 Al}_{2} {normalO}_{3} + C (s)

…”

Section: Resultsmentioning

confidence: 99%

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

Guo

Zhang

Jiao

et al. 2021

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.