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Structure Types of Ceramic Fiber Lining

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The ceramic fiber lining is mainly made up with ceramic fiber products such as ceramic fiber blanket, ceramic fiber module or ceramic fiber board. There are mainly two structure types of ceramic fiber lining: layer structure and tile stacking composite structure.

The layer-structure lining is built by putting ceramic fiber products on the steel sheet of the furnace wall layer by layer and then fixing them with heat-resistant steel anchors or in other ways. According to the lining material, the layer structure can be divided into two types: layer structure with ceramic fiber blanket and layer structure with ceramic fiber felt or board.

The layer structure with ceramic fiber blanket can be classified into butt type and lap type, according to the installation method of the hot face of the blanket. The felt or board is mostly installed in the butt type. Both the two types of layer structure can be classified into anchoring-nail-exposed style and anchoring-nail-embedded style according to the fixed way of anchoring nails.

The anchoring-nail-exposed structure is built by tilting the blanket, felt or board on the wall and then fixing it with anchoring nails, fast cards, rotary cards or nuts. Different materials can be used in the lining according to the temperature along the direction of the lining thickness. This structure can greatly reduce the construction cost, improve the insulation performance and is easy to construct and repair. The drawback is its poor resistance to wind erosion. Since the anchors are exposed in the hot face, when the temperature is high, it puts higher requirements on the anchors. The anchor itself is a heat conductor and the ceramic fiber board (blanket or felt) can generate volume shrinkage when use, which may cause gaps in the butt joints and weaken its insulation performance. Therefore, this structure is suitable to low-temperature heat treatment furnace.

The anchoring-nail-embedded style can avoid the exposing of the hot face of the anchoring nails, reduce the heat loss and improve the insulation performance. But it is difficult to overcome the poor resistance to wind erosion. Meanwhile, if it adopts ceramic-cup structure, the ceramic cup is brittle and expansive, which increases the construction difficulty and the cost. If it adopts sinking-hole structure, when the temperature changes, the sinking hole may generate shrinkage and cracks and damage the anchors. Therefore, it is only suitable to the insulation of the low temperature furnace wall.

Currently the tile stacking composite structure can be categorized into ceramic fiber module + tile structure and polycrystalline bar + module + tile structure (from hot face to cold face). Given the actual conditions such as the speed of the burner flame and the composition of the fuel gas, a layer of coating with good resistance to erosion and high temperature may be brushed on the hot face of the ceramic fiber lining. This coating can form a dense protective layer with good resistance to erosion and high temperature.

The thickness of the ceramic fiber lining is up to the structure of the heating devices (flat wall or curved wall), the thermal conductivity of the materials, the average temperature of the cold and hot face and allowed unit heat loss. The material should be selected by taking into consideration many factors including the maximum temperature, the working conditions, the fuel, the atmosphere and the pressure. The selection of the anchor should be based on the temperature of its location and whether it is in direct contact with fuel gas.

The installation arrangement ways of the modules can be divided into parquet floor type and soldier row type. The parquet floor type is a traditional installation arrangement way and was very popular a few years ago. However, with the development of the development of the applied technology of ceramic fiber module, research and practice have proved that, the parquet floor type has some drawbacks. Therefore, it is only used in the bar pasted structure of the hot face. Currently, most programs adopt the soldier row type.

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