| Manufacture of a High Temperature Structural Insulator
(HTSI) Using Electrofilter Powders Generated in the Bayer
Process |
José Sancho-Gorostiaga,a Antonio Bernardo-Sánchez,b José Pedro Sancho-Martínez,a Daniel
Fernández-Gonzáleza, * and Luis Felipe Verdejaa
Pages : 163-173
DOI : 10.1080/0371750X.2021.1915872 |
| Abstract |
| Electrofilter powder (EP) is a residue generated in large amounts during the calcination
of aluminium hydroxide in the Bayer process. The production of high temperature
structural insulator (HTSI) using EP is proposed. Different tests were made using
different proportions of the starting materials, although the optimal mixture contained
(in wt%) 52% EP, 14.7% silica fume (or quartz), 12% refractory aluminous cement and
21.3% water. Besides, 900 cm3 of polystyrene flakes were added to the mixture to
promote a fine structure of pores. The brick was formed using manual mixing and
vibration compacting in silicone molds. Then, it was dried at 100oC for 24 h, and after
that, subjected to pre-sintering by heating up to 1050oC, and finally it was sintered at
1400o or 1450oC for 2 h. At the end of the process, the brick comprised 63% mullite,
24% anorthite and 13% corundum, with the following properties: density values within
0.75 and 0.80 g.cm–3, thermal conductivity values within 0.25 and 0.29 W.m–1.K–1,
compressive strength values higher than 3.5 MPa, total porosity in the range 75-79%
and overheat stability at 1400oC for 24 h with no appreciable dimensional changes.
[Keywords: Bayer electrofilter powder (EP), High temperature structural insulator
(HTSI), Hot wall insulators, Mullite, Alumina, Waste, Circular economy] |
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