Performance of High Thermal Conductivity Dense Silica Bricks and Their High Thermal Conductivity Mechanism

doi:10.19691/j.cnki.1004-4493.2022.01.005

China's Refractories ›› 2022, Vol. 31 ›› Issue (1): 30-34.DOI: 10.19691/j.cnki.1004-4493.2022.01.005

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Performance of High Thermal Conductivity Dense Silica Bricks and Their High Thermal Conductivity Mechanism

SUN Yang^*(), ZHANG Xiuhua, HU Hao, LIU Xiang, LIU Ying, CHEN Bo

China Metallurgical Research Institute Co., Ltd., Beijing 100088, China

Online:2022-03-15 Published:2022-04-02
Contact: SUN Yang
About author:Sun Yang received his Ph.D degree of material science in University of Science and Technology Beijing in 2021. His research interests include metal composite refractories, non-oxide composite refractories and low creep Al₂O₃-SiO₂ refractories. Since 2021, he has been working in China Metallurgical Research Institute Co., Ltd.

Abstract

Abstract:

High thermal conductivity dense silica bricks have the higher thermal conductivity than ordinary silica bricks, which is conducive to the realization of energy saving and emission reduction in the iron and steel industry. The performance of ordinary silica bricks and high thermal conductivity dense silica bricks was compared, and the high thermal conductivity mechanism was analyzed. The results show that (1) compared with ordinary silica bricks, high thermal conductivity dense silica bricks have the characteristics of higher thermal conductivity, lower apparent porosity, higher tridymite content, higher compressive strength, and higher thermal expansion; (2) by increasing the tridymite content and reducing the porosity, the close packing of honeycomb α-tridymite improves the density and continuity of the SiO₂ frame structure of the silica bricks, and the larger area perpendicular to the heat transfer direction improves the thermal conductivity of the bricks; (3) the densification of the silica bricks also increases the thermal expansion of the bricks, but they still meet the standard requirements.

Key words: high thermal conductivity dense silica bricks, performance, thermal conductivity mechanism

SUN Yang, ZHANG Xiuhua, HU Hao, LIU Xiang, LIU Ying, CHEN Bo. Performance of High Thermal Conductivity Dense Silica Bricks and Their High Thermal Conductivity Mechanism[J]. China's Refractories, 2022, 31(1): 30-34.

Figures/Tables 12

Fig. 1 Thermal conductivity (1 000 ℃) of high thermal conductivity dense silica bricks

Fig. 2 Apparent porosity of two kinds of silica bricks

Fig. 3 Pore size distribution of two kinds of silica bricks

Table 1 Stable temperature and crystallization habits of tridymite variants

Tridymite variants	Stable temperature /℃	Crystallization habits
γ-tridymite	Room temperature-117	Spearhead
β-tridymite	117-163	-
α-tridymite	870-1 470	Honeycomb

Fig. 4 XRD patterns of two kinds of silica bricks

Fig. 5 SEM images of high thermal conductivity dense silica brick

Fig. 6 Cold compressive strength of two kinds of silica bricks

Table 2 SiO2 crystal transition temperature and relative thermal expansion

Phases	Transformation	Temperature /℃	Thermal expansion /%
Quartz	β-α	573	+0.82
Cristobalite	β-α	180-270	+2.80
Tridymite	γ-β	117	+0.20
Tridymite	β-α	163	+0.20
β-quartz — β-tridymite		870	+16.00
Quartz glass — β-cristobalite		1 000	+0.90

Fig. 7 Relationship between thermal expansion of silica bricks and temperature

Fig. 8 Relationship between deformation rate of silica bricks and temperature under pressure

Fig. 9 Thermal expansion and apparent porosity of two kinds of silica bricks and their linear fitting

Fig. 10 Linear thermal expansion distribution of two kinds of silica bricks

References 10

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