Guideline on the Applications of Ceramic Fiber in Industrial Furnaces

Ceramic fiber is a new lightweight insulation material made of industrial alumina. It has light weight, low thermal conductivity and good thermal shock resistance, so it is widely used in industrial furnaces. 

(1) Soaking furnace

A soaking furnace is a furnace used to heat steel ingots in blooming plants. Before rolling, ingots should be heated and soaked in a soaking furnace to meet the required temperature. The soaking furnace is pit-shaped. The heating temperature of ingots is 1200-1250℃. The temperature in the furnace can reach up to 1350-1400℃. A soaking furnace is a type of periodically thermal system. 

Traditional soaking furnaces are built with refractory bricks. The middle part is built with silica bricks. The bottom and the wall are built with high alumina bricks, but sometimes, the bottom is built with magnesia bricks. The movable cover is built with shaped fire clay bricks. Since the monolithic materials are widely used, soaking furnaces trend to be built with refractory castables instead of refractory bricks. This has achieved good results. 

Ceramic fiber products can be used in the permanent insulation layer of the cold face, cover sealing groove and the wall linings in the furnace.

(2) Pusher continuous furnace

The ingots produced by steel plants are heated in a soaking furnace and then rolled into blooming billets with different shapes and sizes with billet rolling mills. In the pusher continuous furnace, the blooming billets or continuous casting billets are heated to the required temperature of hot rolling. According to the thermal system, temperature system and the shape of the hearth, pusher continuous furnaces can be divided into two-stage, three-stage and multi-point continuous furnaces. 

Ceramic fiber modules can be used in the wall lining of the preheating zone, the back lining of the heating and soaking zone, the wall lining of the flue system and the wrapped materials of the hot air pipes. 

(3) Walking Beam Furnace

A walling beam furnace is a mechanized furnace which moves the billets with a dedicated stepper machine. Its basic characteristic is that the movement of the billets relies on the rectangular reciprocating motion of the movable walking beam. It moves the billets on the fixed beam from the feeding end to the discharging end step by step. 

Ceramic fiber modules are used in the preheating zone, the back lining of the heating and soaking zone, the wall lining of the flue system and the wrapped materials of the hot air pipes.

(4) Rotary Hearth Furnace

A rotary hearth furnace is also a type of continuous furnace. It is constituted of an annular hearth and rotary hearth. It is mainly used to heat round billets and other shaped billets and sometimes square billets. Generally, it is used to heat the billets before forging and rolling. 

The inner walls will expand after heated in the direction of the inner shell. The masonry is easy to collapse and should be reinforced. Since ceramic fiber has no expansion at high temperature and good thermal stability, it is widely used in the wall linings. 

(5) Bogie hearth Furnace

A bogie hearth Furnace is an intermittent variable temperature furnace. During the operation, the temperature in different parts varies over time. The hearth is not divided into different zones. The temperature varies over time according to the predetermined temperature heating system. It is used to heat the ingots before forging or for heat treatment. 

Traditional heavy refractory materials have large heat loss and regenerative loss, so the thermal efficiency is low. The thermal efficiency of the bogie hearth Furnace built with bricks is 15%, while the thermal efficiency of the furnace built with ceramic fiber can reach up to 40%. This can greatly reduce the cost and make the furnace lighter. 

(6) Bell Furnace

The bell furnace is a type of intermittent variable temperature furnace. The hearth is not divided into different zones. During the operation, the temperature in different parts varies over time. It is mainly used for the bright annealing and general heat treatment of the workpiece. The bell resistance furnace is mainly used for high temperature heat treatment. 

When using ceramic fiber in the lining, the outer shell is lighter. 

(7) Shaft Furnace

A shaft Furnace has a vertical circular hearth with a diameter of 0.5-4.5 m and a max depth of 30m. Its thermal system is similar to the bogie hearth Furnace. It is used for the heat treatment of long rod-shaped workpieces, such as barrels, turbine shaft, generator rotor and marine diesel engine spindles. 

It is built with fire clay bricks as the inner lining and ceramic fiber as the back insulation lining. During operation, it is important to ensure the vertical degree of the workpieces when loaded and released. Keep the workpieces from dashing on the wall lining. The wall lining and cover can be built with ceramic fiber. 

(8) Drying kiln

Common chamber drying furnaces refer to the sand drying furnaces. After the sand is heated, the moisture it contains will be vaporized and diffuse into the surrounding media so as to achieve the result of drying. 

The chamber drying furnace is a type of low-temperature intermittent furnace. A layer of ceramic fiber pasted on the hot face of the red brick wall significantly improves the thermal efficiency and drying rate of the drying furnace. 

(9) Tunnel kiln

A tunnel kiln is a type of modern industrial furnace widely used in the building material industry, ceramic industry and refractory industry. It is a type of continuous thermal equipment. Along the longitudinal direction, it can be divided into the preheating zone, firing zone and cooling zone. Ceramic fiber can be used as the lining in the preheating zone and cooling zone and the back lining of the firing zone. 

(10) Shuttle kiln

A shuttle kiln is a type of car bottom kiln. It can have two kiln doors set on the two ends along the longitudinal direction. Sometimes, there is only one door. All kiln cars pass in and out through this door. This type of shuttle furnace is also called a drawer kiln. Since the products are loaded and released outside the furnace, it greatly reduces the labor intensity and improves the labor conditions. 

The shuttle furnace always adopts a thin-wall structure with good insulation. A shuttle kiln used in the ceramic industry is built with 230mm thick lightweight bricks and 30mm ceramic fiber.