Refractory materials are of the greatest importance to the glass manufacturer. When selecting refractory materials for any kiln or furnace, the properties that refractories must have in order to face the operating factors should be taken into account.

The feeder of the glass furnaces is made up of spouts, spout burners, spout covers, plungers, tubes, orifice rings.

Spouts

Spouts work at constant temperature. Operating factors that should be taken into account are the temperature and the glass corrosion at the operation temperature. The temperature is the first factor to consider since it is limiting the application of some refractories. The glass corrosion is, actually, related to the temperature and this is why it is necessary to fix the temperature limit of the refractories and choose the right ones for not reducing the normal campaign life.

When glass is in contact with any refractory material at high temperature, the chemical reaction is a dissolution process. To increase the glass corrosion resistance, spouts must obviously have the right porosity and density, but the chemical composition and the mineral crystal structure are the most important factors. The glassy phase content must be as low as possible because it is a week point in a refractory material. The zircon mullite brick and fused cast alumina block are used as spouts in the glass furnaces due to their good corrosion resistance and high temperature strength. Moreover, Fused cast Alumina block has a very small amount of glass phase.

Plungers and tubes

The operating factors of plungers and tubes are the temperature, glass corrosion and thermal shock. When any refractory material is in contact with glass at high temperature, the chemical reaction is a dissolution process too. In short plungers and tubes in contact with glass must have a crystalline structure and a very low glassy phase content for a strong glass corrosion resistance. Plungers and tubes are exposed to sudden temperature variations when installed, thus their structure must be crystalline and with very low glassy phase which is the week point for thermal shocks. Zircon mullite brick is always used as plungers and tubes in the feeder of the glass furnaces.

Orifice rings

The operating factors are the temperature, glass attack and thermal shock like for plungers and tubes. Actually even a very small corrosion of the holes has an influence in the gob weight. This is not a problem when glass articles are produced in small series but for long article series special inserts (metallic or ceramic) are used to prolong the orifice ring life. Low thermal expansion and low thickness of orifice rings help for the thermal shock resistance. Zircon mullite brick is used in long-life orifice rings.

Spout covers and burners

The only operating factor for spout covers and burners is the temperature. Silimanite bricks with good corrosion resistance, dense structure and good thermal shock are used as spout covers and burners.

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