Each oven includes a heat source and a compartment delimited by a coating is usually suitable to prevent or limit the loss of heat towards the outside.
Depending on the function are distinguished reheating furnaces for industrial, ovens for cooking food, incineration furnaces for the destruction of waste, etc.
Depending on the physical principle used to generate heat, stand combustion furnaces, electric furnaces and ovens to plasma; solar ovens.
The ovens are burning all those using, as the source of heat, liquid, solid or gaseous include a fireplace and a heating chamber.
They can be a direct or indirect heating.
In ovens in direct heating, the materials are more or less in contact with the heat source; the fireplace is located, generally, at the base of the chamber: in those with inner hearth the material is lapped by the products of combustion (for example ovens for bread, the ovens of the countryside, etc.) or even is mixed with the fuel (for such as metallurgical furnaces); in those with hearth outside the combustion products reach the material indirectly as the latter is held raised with respect to the hearth (for example the ovens of the household kitchens, etc.).
In ovens with indirect heating, the materials are placed within a heating chamber completely isolated from the hearth (which can also be placed laterally) but lapped combustion products (for example, muffle furnaces, retort furnaces, etc.).
According to the draw will have ovens aspirated, in natural or forced circulation, or wind blown furnace, where the combustion air is blown to slight pressure through special nozzles.
The ovens combustion can be continuous or discontinuous. In the first loading and unloading of the material to be treated take place continuously without having to suspend the operations of the oven; the discontinuous furnaces instead require at least a reduction in the activity cyclically to allow the extraction of the whole charge of the treated material. A special category is that of the reverberatory furnaces, in which the heating is obtained in a chamber, said laboratory, by the effect of the time which is lapped by the hot flames.
Electric ovens are those that use the heat produced by a heat source that uses electricity.
The ovens in plasma are those that exploit the thermal energy produced by a plasma jet that invests the material to be heated or to be melted. The plasma may be argon, hydrogen, nitrogen, oxygen, and can reach temperatures of 20,000 ° C.
In addition to the simple ovens for cooking food, which can be combustion (employing coal, wood, petroleum products, city gas) or electric, all constructionally very simple, and the blast furnaces and the converters, there exists a wide range of industrial furnaces of which the most important are the metallurgical furnaces.