The crown of an oxygen fuel glass furnace is exposed to the conditions of e rosion of high temperature alkali vapor and batch dusts, and load. A better high temperature creep resistance is key for the crown blocks of the Oxy-f uel glass furnaces. Fused cast alumina block has been now used as crown ref ractories in oxy-fuel furnaces for several years.
Oxy-fuel technology involves the replacement of the combustion air with oxy gen (>90 % purity). The technique can be used with either natural gas or oi l as the fuel, although the use of gas is more common. In the glass industr y, oxy-fuel technology offers advantages including increased productivity, noise reduction, reduced melting times, and glass quality improvements. How ever, it may increase refractory wear, which may affect the product quality by increasing silica corrosion at the crown of the furnace, and decrease f urnace life, oxygen production costs, and potential problems related to con versions from regenerative furnaces.
Fused cast alumina block for crown application in glass industry is commerc ially available in two types, alpha-beta and beta alumina. Fused cast alumi na blocks have high refractoriness, spall resistance, and low levels of por osity and possess low levels of glassy phase in their structure, making the m less susceptible to deformation by the mechanisms of creep.
Due to their high thermal conductivity, heat flow through a furnace crown c omposed of fused cast alumina is higher than through traditional silica cro wns, affecting back-up insulation designs and cooling methods employed on t he exterior of the furnace.
In conventional(air-fuel-fired) furnaces, alpha-beta alumina has been used primarily in glass contact applications in applied exclusively in superstru cture application. In oxy-fuel furnaces both types of refractories have bee n used for crown and superstructure applications. The alpha-beta alumina bl ocks have been exposed to a much wider range of temperature, stress(span), atmospheric chemistry, and length of campaign than beta alumina blocks. Fus ed cast Alpha-beta alumina block has been used for oxy-fuel furnaces crowns in specialty, float and container glass furnaces.
Sunrise Refractory