Furnace Industry Information

Furnaces are an enclosed structure that produces heat for industrial purposes. They are made with several kinds of heat resistant (refractory) elements to withstand long term use. The enclosed space holds the materials, gas or air being heated until the desired temperature is reached. Furnaces can come with varying temperature control options or set for a single temperature, depending on the process for which the furnace will be used. Furnaces commonly have one of the following atmospheres: air or oxidizing, inert, reducing, salt bath and vacuum. Over temperature protections, service or entry holes, three-zone or multi-zone, view ports, computer interface and application software are some of the features available on these furnaces. Heat sources can be infrared or radiant, natural gas, induction, conduction, electrical or dielectric.
 
Furnace designers produce furnaces that are used for various heat treatments of materials. Heat treating adds billions of dollars per year in value to metal products, especially steel and nonferrous products, by imparting specific properties to the parts. These properties are critical to the proper function of the parts. Basically, heat treating involves three steps. The part is first heated to a specified temperature up to 2400.25ºF. It is then held at that temperature for the required amount of time, which may be as little as a few seconds or as much as 60 hours. Finally, the parts are cooled either in the furnace or by quenching methods, which quickly cool the parts.
 
While furnaces are similar to industrial ovens, they usually have higher temperature capacities than ovens, as well as differing uses. Furnace designers create industrial furnaces that can be used to heat air or gas as part of a process or heating system; ovens typically cannot. Furnaces can be used to alter or simply heat the material involved. Other uses for furnaces include ageing, annealing, atmosphere control and sterilization. It is important to consider the temperature requirements, pressure involved and makeup of the material when looking for furnaces. The internal width, length and height of the furnace are factors that are determined by furnace designers and the size of parts or materials to be processed.
 
The steel industry, among others, uses high-temperature, natural gas-fired furnaces, which produce large amounts of nitrous oxide (NOx) per unit of processed material. To meet increasingly stringent emissions regulations, oscillating combustion technology has been developed and is continuing to be improved. This technology provides efficiency, productivity and reduced NOx emission from all types of furnaces. A valve is used to oscillate the fuel flow rate to the burner. Oscillation creates fuel-rich and fuel-lean zones within the flame that retard the formation of NOx, increasing heat transfer to the load. Another project is underway to reduce NOx emissions and carefully control flame temperatures of natural-gas furnaces with flame image sensing techniques. Flame data will be collected with either fiber-optic detectors or spectrometers and video cameras. The data will be used to develop control strategies for the most efficient control of these furnaces.