The Working Principle of a Rotary Furnace
A rotary furnace is a barrel-shaped instrument that is rotated around its axis when performing heat treatment. These instruments are tilted slightly to allow the sample under heat treatment to be passed from one end of the barrel to the other. This sample transfer occurs as the rotary furnace rotates, and this rotation can also induce some mixing or stirring of the sample.
When the rotary furnace is in operation, hot gases pass through the chamber to perform the heat treatment. Generally, the hot gases pass through in the opposite direction than the sample, but depending on the application requirements they can also pass through in the same direction.
Rotary Furnace Components
Rotary furnaces consist of some basic components, including the furnace body, the furnace lining, the drive gear, and internal heat source.
The furnace body in a rotary furnace is generally made from steel plate and welded to form the barrel, which can be up to 230 m in length. The length of the furnace body can vary dramatically depending on the application, however, it becomes harder to maintain a uniform temperature throughout the chamber the longer the furnace.
The furnace lining is generally made from a refractory material to ensure that the steel body is insulated from the extremely high temperatures generated inside the furnace. A refractory lining also provides the rotary furnace with protection against corrosion. The refractory used can be bricks, cement, or moldable, depending on the application requirements. Typically, all refractories can withstand temperatures of up to 1000oC.
The drive gear is the component that rotates a rotary furnace, although this can sometimes be replaced with driven rollers. For a rotary furnace to have a variable rotation speed, the drive gear needs to have a variable speed drive to control this.
Depending on the application requirements, the internal heat source can be gas or electric. These heat sources can be driven by conduction, convection, or radiation.
Rotary Furnace Applications
There is a range of heat treatments that can be performed in a rotary furnace, including oxidation, to reduce the number of electrons in a sample. Calcination is a popular application of rotary furnaces, which is the process of inducing thermal decomposition.
Rotary Furnaces from Thermcraft
Thermcraft have been manufacturing industrial furnaces since 1971. We have a range of quick-ship furnaces and can also build custom solutions.