An industrial furnace refers to equipment which is used to provide heat for a certain process or reaction. Industrial furnaces are indispensable devices for metal casting and other processes in the iron and steel industry, for instance. They are also used in glassmaking and chemical manufacturing. Numerous designs of industrial furnaces exist, but most have some features and purposes in common.
In a typical industrial furnace, fuel flows into a burner and is burned with the help of an air blower leading into it. The flames from the burner rise to heat the radiant section of the furnace. This section is also known as the firebox. Along the walls of the radiant section are metal tubes containing a fluid called heat transfer fluid (HTF). Industries commonly use their furnaces to heat this secondary fluid which is then carried around the plant to wherever heat is needed as a part of production.
The use of HTF is particularly useful when the material being heated is volatile or especially sensitive to high temperature. In addition to the tubes carrying HTF, insulation lines the walls of a typical industrial furnace, in order to avoid excessive heat loss. Above the radiant section is the convection section. It also has HTF tubing in it and is there to recover additional heat.
This part of an industrial furnace serves much the same purpose as the radiant section. The difference lies in the lower temperature of the convection section, and the fact that the heat is transferred by convection rather than by radiation from the burning fuel. At the top of the convection section is a small hole called a sightglass. The sightglass allows personnel to monitor the inside of the furnace. An industrial furnace must be monitored from time to time to ensure safety of operation.
One common problem which can be detected through a sightglass is flame impingement. This occurs when flames from the burner are either too close to, or are touching the metal tubing. Isolated spots of very high temperature can occur with flame impingement, and this can pose a hazard if not remedied.
At the top of an industrial furnace is the stack, a cylindrical structure that expels waste gas from the furnace. The stack is necessary to move hazardous gases away from personnel, but it also serves another purpose. Inside the stack is what is called a damper blade, a valve which regulates the amount of heat lost through the stack. It also keeps the pressure inside the furnace within a range that is safe for those working around it.