Preparation of high strength and low thermal conductivity mullite refractories based on reconstruction of fly ash

Abstract

The preparation of refractories with both low thermal conductivity and high strength are continuously pursued in industrial furnaces. In this work, mullite refractories with low thermal conductivity and high strength were developed using fly ash as main raw material, and the influence of the quantity of fly ash and sintering temperature on the structure and properties of mullite refractories were investigated. The results show that mullite refractories with low thermal conductivity and high strength could be prepared by using fly ash in large proportion; the thermal conductivity of the samples decreased with the addition of the fly ash and increased with the increase of sintering temperature; the cold compressive strength and modulus of rupture of samples all are enhanced with the increase of sintering temperature, which is attributed to the formation of more elongated mullite by the reconstruction of fly ash at high temperature. For the mullite refractory using 65.04 wt% fly ash treated at 1600 • C, the thermal conductivity was .732W/(m⋅k) at 1000 • C, and the cold compressive strength and modulus of rupture could reach 143.5 ± 5.7 MPa and 47.0 ± 4.1 MPa respectively. It can be considered to use as a prospective work lining in industrial furnaces to meet energy saving requirements.

Fabrication of porous mullite‐based ceramic bricks from Al‐rich water treatment sludge and kaolinitic‐based clay

“…For instance, mullite refractories are widely used as furnace lining material and kiln slabs due to their high refractoriness under load, low thermal expansion coefficient, and excellent thermal shock resistance. 15,16 Again, researchers have attracted much attention to porous mullite refractories used as insulators in industrial furnaces owing to the excellent combination of low density and low thermal conductivity. 17 The chemical makeup suggests that WTS can be mixed with kaolinitic clay to enhance mullitization through liquid phase formation.…”

“…The porous mullite bricks produced in the current work can be used as insulation material in industrial furnaces owing to their low thermal conductivity and relatively high strength. 15…”

“…Due to the chemical makeup of WTS, it is possible to produce mullite refractories with a good combination of properties for varied applications by carefully selecting a kaolinitic clay source. For instance, mullite refractories are widely used as furnace lining material and kiln slabs due to their high refractoriness under load, low thermal expansion coefficient, and excellent thermal shock resistance 15,16 . Again, researchers have attracted much attention to porous mullite refractories used as insulators in industrial furnaces owing to the excellent combination of low density and low thermal conductivity 17 .…”

“…The effect of Al‐rich sludge on the mullitization and physical and mechanical properties of the porous mullite ceramics have been discussed. The porous mullite bricks produced in the current work can be used as insulation material in industrial furnaces owing to their low thermal conductivity and relatively high strength 15 …”

Preparation of microporous mullite refractories with high strength based on low‐grade bauxite and coal gangue

“…Significant progress has been made in the development of microporous mullite materials over the past several years. For example, in situ decomposition synthesis, [8][9][10] gel-casting, 11,12 and foaming methods, 13,14 among others, have been utilized to produce mullite refractory materials with high porosity and low thermal conductivity. By decomposing carbonate, hydroxide, and silicate minerals in raw materials, generating gas, and removing water at high temperatures, in situ decomposition is one of the most prevalent methods of pore formation, 15 producing pores with small sizes and uniform distribution.…”