Refractories performance affects glass manufacture in the production cost a nd the quality of the glass. Refractories in different areas of a glass fur nace suffer different operating environment. So different types of refracto ry are used in the different parts of the glass furnaces.
Crown Refractories
Crown of glass furnaces are subjected to long-term thermal attack and chemi cal corrosion due to alkali vapor. It also need to be heavily insulated to reduce the energy loss. So it requires volume stability, low permeability, low conductivity, and high refractoriness of refractories in this area.
Silica refractories are the preferred material for crown construction due t o its affordability, low stoning potential, insulating capability, resistan
batch material. They have been used for the construction of glass melting furnace for over a century. Although today the use of silica bricks is rest ricted to crown and superstructure, the steady improvement in production of silica bricks has led to greater chemical purity and stricter dimensional tolerances over a wide range of shape and sizes. To meet the demanding requ irement of oxygen-fuel furnaces, fused cast alumina block is used due to it s excellent resistance against acid slag, chemical corrosion and alkali vap or.
Superstructure Refractories
The superstructure of the furnace will suffer from high temperature and che mical attacks by volatile products and dust which settle on the walls and a ttack refractory products characterized by a progressive wear of refractory in contact with the glass. Refractories in this part are required to have a high thermal shock resistance and corrosion and erosion resistance.Fused cast AZS block, Zirconia-Mullite brick and Mullite brick with high density, low porosity, good hot strength and good sag resistance are used in this a rea.
Bottom and Lower Side wall Refractories
In contact with melt glass, refractories in those areas suffer high Tempera ture, and glass corrosion. Chemical reactions also take place between refra ctories and molten glass, fluxing agents, and/or volatile components. Erosi on can follow; washing away refractory grains after the original bond has d issolved. With a high refractoriness, high thermal resistance, a low reacti on with melt glass, a very strong glass corrosion and vapour resistance, Zi rconia-Mullite bricks and Fused Cast AZS are installed on the bottom or in direct contact with sidewalls.
Regenerator Refractories
These areas of the furnaces are subject to special intense aggression in th e long campaigns because of the chemical reactions between refractory mater ial and hot gas. A higher performance of the refractory and insulating mate rial is required in these cases in order to attain better heat efficiency. A regenerator consists of a regenerator chamber in which a checker work (or just checkers) of refractory bricks has been stacked. Due to high stabilit y, high thermal shock resistance, low thermal expansion, high refractorines s and the high resistance to basic slags, Magnesia bricks are normally used in the regenerator including area above checker work and crown. With a hig h alkali resistance and creep resistance, fireclay bricks are particularly suitable for the lower parts of regenerator.
Besides refractories mentioned above, insulating refractories with low cond uctivity and good mechanical strength are used to reduce heat loss in areas where abrasion and wear by aggressive slag and molten metal are not severe . The insulating materials can lead to savings in fuel cost and a more rapi d heat-up. After the furnaces are installed, unshaped refractories such as special ramming &patching masses are used to repair some parts of the furna ces to extend the furnace's life until the end of the campaign.
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