During the long-term operation of glass melting furnace, due to the atmosphere and high temperature impact in the furnace, the refractory lining in the furnace is prone to loss. The use of gunning material repair has achieved good results. In glass melting furnaces, the most commonly used gunning material is zirconium gunning material, which is mainly used for the repair of breast walls and pool wall bricks. The so-called gunning material is to repair the furnace lining or apply various coatings (protective coatings, high-radiation coatings, etc.) by spraying. The former is more common, hence the name.
How to use gunning material
The refractory material used for gunning material should be determined according to the use conditions (such as temperature, atmosphere, erosion conditions) and the properties of the furnace lining. It should be similar to the chemical properties and thermal expansion of the furnace lining. The material particle size depends on the thickness of the gunning layer, the spraying method (wet or dry) and the equipment. It affects the adhesion and rebound loss. The wet material is mostly 0.5mm, and the dry material can reach 6~7mm. The binder is usually sodium silicate or phosphate, and sometimes a small amount of flux is added to facilitate sintering. The amount of water added should take into account the spraying operation and the volume stability, structural density, strength and thermal shock resistance of the sprayed layer.
The moisture content of the sprayed material should be determined based on the requirements for the quality and thickness of the sprayed layer, the performance of the spraying equipment and the operating technology. The high content can reach more than 25%, and the low content is about 16%. Even dry mixtures are completely used and only a small amount of water is mixed at the end of the nozzle for spraying.
Wet materials must be mixed in advance, the spraying operation is simpler, the rebound loss is small, the structural density of the sprayed layer is low, the erosion resistance is poor, and the thickness of the sprayed layer is thinner (20~25mm). Dry materials do not need to be mixed in advance, the spraying operation is more complicated, the rebound loss is more, the structure of the sprayed layer is denser, the erosion resistance is better, and the thickness of the sprayed layer is large (up to 50~60mm).
Spraying construction improves the strength of refractory materials and has better erosion resistance. The lining of the flame space, small furnace and regenerator of the glass kiln can be repaired with gunning materials. When the erosion surface of the furnace lining is large, it is better to use wet method for hot spraying, while dry method is mostly used to fill the local severe erosion areas.
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