Furnaces are enclosed structures that produce high heat for a number of commercial, residential and industrial purposes. Compared to ovens, they are able to produce or emit much higher temperatures, and are therefore used in heating larger spaces or for reaching a maximum temperature.
Modern businesses utilize an impressive variety of different types of industrial furnaces. While all of these furnaces offer the capability to generate high temperatures, not all industries utilize the same types of designs. Different industrial furnaces suit the needs of specific manufacturers.
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The History of Industrial Furnaces
Ancient peoples discovered that high heat would melt metal, but for thousands of years, manufacturers possessed only a limited ability to control and regulate heating temperatures and metal quality consistently. The Romans created furnaces that used charcoal to smelt ores, and this practice continued in Europe for hundreds of years. During the 1600s, following increased deforestation in England, coke made from coal became a popular fuel for furnaces and ovens.
Manufacturing capabilities increased significantly during the 1800s as the Industrial Revolution spread. In 1837, Richardson & Boynton Company began offering commercial furnaces for sale in the USA. A major breakthrough occurred with the development of the Bessemer converter in 1856 in England. It ultimately led to the construction of blast furnaces designed for the mass production of iron. A French inventor named Paul Heroult received the first patent for an electric arc furnace in 1907. Innovations in industrial furnace design continued throughout the Twentieth Century into the modern era.
Some Advantages of Using Industrial Furnaces
Industrial furnaces offer several advantages. First, this equipment permits the generation of high temperatures safely. Second, modern furnaces usually enable an operator to control the temperature level with precision. Third, the furnace may permit the production of certain materials requiring a sustained exposure to high temperatures over the course of designated periods of time.
Industrial Furnace Operations
An industrial furnace frequently transforms material directly from one state to another. For example, a furnace may change iron or copper from a solid to a molten form. Industrial furnaces also perform a second function by enabling manufacturers to heat treat materials to obtain desired reactions. This equipment plays an important role in some metal surface treatments intended to enhance corrosion resistance and product wear resistance.
Today, individual furnaces also display versatility. Manufacturers have developed a number of specialized products, including continuous furnaces and electric arc furnaces. Elements such as the maximum temperature, the use of a heat exchanger, or the fuel source may vary. Additionally, the sizes and designs of industrial furnaces currently run the gamut from small, portable units to large, multi-story blast furnaces intended to remain permanently in a single location.
Industrial furnaces come in many different specifications and designs according to their specific function. Some are compact and portable, with shelving and a swing-open door. These are common in laboratories during product or material testing. In large metallurgy facilities, furnaces are often composed of large, continuous conveyor systems that handle extremely high volumes of parts or products. These furnaces are fully automated and usually CAD/CAM operated. For facilities with smaller runs, manually loaded/unloaded furnace chambers are employed. Small furnaces usually require the use of handling tools and crucibles, which are containers that can withstand direct contact with molten metal. Depending on the material's melting point or the desired product results, all furnaces have differing process temperatures, which are the maximum temperatures at which the furnace will effectively and safely operate. Many industrial furnaces that contain multiple chambers include a loading/unloading chamber, heat zone chamber and cooling chamber. The heat zone can reach temperatures upwards of 3000º F for the most extreme applications. Therefore, all components are made of silicon carbide or a nickel chromium alloy, both of which are extremely heat resistant, refractory materials that are able to withstand long term use. The cooling chamber uses either cold water or air to lower the material's temperature. Some contain cold water baths, which are used for the quenching process.
- Continuous Furnaces
- The operation of a particular furnace frequently depends upon its intended purpose. The development of the continuous furnace illustrates this situation. This type of industrial equipment permits manufacturers to heat certain materials used during production on an ongoing basis to achieve nearly 24/7 productivity. Steel mills which utilize continuous casting operations benefit from the availability of this technology for the operation of their blast furnaces. The industrial rotary hearth furnace and the pusher furnace represent just two specialized examples of specialized continuous furnaces employed by metal parts manufacturers.
- Electric Arc Furnaces
- Companies engaged in scrap metal recycling usually rely upon electric arc furnaces. Powered with the assistance of electricity, these specialized furnaces permit manufacturers to break down and melt smaller quantities of metal at one time economically using electricity. They offer a cost-effective alternative to large blast furnaces in some settings.
- Annealing Furnaces
- Use hydrogen to protect materials from oxidation, relieving the residual stresses produced during the processing of steel strips, tubes and rods. The hydrogen also has high heat transfer properties that aid in the reduction of production cycles.
- Batch Furnaces
- Heat treat one load at a time. Batch furnaces are used in applications in which large parts and complex alloy grades must be treated.
- Belt Furnaces
- Continuous-type furnaces that move parts using a mesh-type or cast-link belt.
- Blast Furnaces
- Large towers or cylinders that have a heat resistant lining and force gusts of hot air and gases up through the furnace load.
- Car Furnaces
- Batch-type furnaces that are used for lower stress-relieving ranges. Car furnaces utilize a car on rails for entering and exiting the furnace area.
- Continuous Type Furnaces
- Heat-treating furnaces through which materials continuously enter one door and are discharged through another.
- Direct-Fired Tunnel-Type Furnaces
- Continuous-type furnaces in which the parts are conveyed through a tunnel-like heating area on hooks or fixtures, in order to minimize distortion.
- Electric Furnaces
- Machines that use electricity to heat.
- End Port Regenerative Furnaces
- Used to melt glass, have burner ports and the checkers on the same end. While end port regenerative furnaces are initially energy efficient, the checker volume eventually decreases through plugging, resulting in the gradual decrease of melting efficiency over the life of the furnace.
- Gas-Fired Furnaces
- Burn gas to create heat.
- Heat Treating Furnaces
- Heat the material and cool it to bring it to a desired point for increased strength, aging or manipulation.
- Induction Furnaces
- Use combined electrical resistance and hysteresis losses to heat metal by exposing it to the varying magnetic field around a coil-carrying alternating current.
- Pusher Furnaces
- Continuous-type furnaces in which parts are charged into the furnace in containers on a periodic basis. These containers are pushed against a line of containers that have already been heated, advancing the containers towards the discharge end of the furnace, where they are put into use.
- Rotary Retort Furnaces
- A type of continuous furnace that utilize an internal screw to advance the parts, giving good control of the retention time within the heated chamber.
- Shaker-Hearth Furnaces
- A type of continuous furnace that advances the parts along the hearth using a reciprocating shaker motion.
- Side Port Regenerative Furnaces
- Used to melt glass, have burner ports on opposite ends and incorporate a greater checker volume than the end port regenerative furnace, resulting in higher pull rates.
- Sintering Furnaces
- Heat materials below their melting point to make them more dense or compact and solid, which can lead to shrinkage.
- Slot Furnaces
- Furnaces in which stock is charged and removed in batches through a slot or opening.
- Vacuum Furnaces
- Airtight and use low atmospheric pressure as the atmosphere for heating.
Applications For Industrial Furnaces
All industrial furnaces share a common purpose: they permit manufacturers to generate high temperatures. While the design of the furnace, the raw materials, the preferred fuel, and even the use of heating resources may vary, the capability to safely produce high temperatures has contributed to the popularity of this vital equipment. Industrial furnaces contribute value to numerous manufacturing processes.
All industrial furnaces offer the ability to generate high temperatures. Yet some manufacturers also employ the heat from industrial furnaces to synthesize chemicals or perform heat treatments. Additionally, industrial furnaces allow some power companies to generate sufficient heat in order to heat water to operate big steam turbines in thermal power stations or to incinerate landfill waste.
Customers choose to use an industrial furnace for many different reasons. This equipment performs a valuable role in the mining industry by assisting metal manufacturers in extracting some types of raw metals from crushed ores. Both ferrous and non-ferrous metal manufacturers also frequently employ industrial furnaces in high volume smelting and casting operations.
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.
Scrap metal producers rely heavily upon electric arc furnaces to process steel and other materials. Landfill companies use incinerators (some of which qualify as industrial furnaces) to transform certain waste products into non-toxic materials. Glass manufacturers also often require access to industrial furnaces during their operations. Brick and ceramic products manufacturers widely utilize industrial heating ovens. Other firms engaged in the construction materials fabrication business also sometimes depend upon industrial furnaces, including chemical manufacturers and oil refineries.
The varied applications of industrial furnaces today testify to the complexity and sophistication of this marketplace. Both your industry and your specific enterprise needs may dictate the type of heat generating assets you require, from reverberatory to nearly continuous furnace operations.
The Components of an Industrial Furnace
While the individual designs of industrial furnaces often differ markedly, all of these units do possess certain basic features in common. Some important elements in an industrial furnace include:
- Furnace Power Source and Fuel
- Every industrial furnace requires some type of power source or combustible fuel in order to generate heat. In general, this equipment relies upon either electricity (for an electric furnace) or a combustible source of power such as coal or natural gas (for a blast furnace). Today many industrial furnaces closely resemble ovens or kilns; they may include a blower motor or even a heat pump within the assembly.
- There are many different furnace heat sources available today. They include radiant, natural gas, induction, conduction, electrical and dielectric, and each method has its specialized benefits, limitations and applications. Radiant heat furnaces are similar to wood stoves and portable heaters. They use a flame to heat an object, commonly a ceramic plate. This object gives off heat that transfers throughout the area. Natural gas furnaces are very common. Compared to electric furnaces, they are an economical method of creating a high heat environment. They burn natural gas or propane in order to generate heat, and are used for their high temperature abilities.Induction furnaces use a combination of electrical resistance and hysteresis losses to heat metal parts. They are exposed to a magnetic field around a coil-carrying alternating current. Induction furnaces are the first choice in metal melting applications and are often used by iron foundries. Electric furnaces are also popular for melting metal. The most common type is an electrical arc furnace, which uses high amounts of electrical current, which travels through a metal arc and is conducted onto large amounts of scrap metal. The current heats the scrap to a high enough degree to melt it completely. These furnaces are mostly used for recycling metal parts to be formed into new products.
- Access to Heat
- Industrial furnace designers need to consider ways to provide access to ensure items undergoing transformation within a furnace come into contact with heat. Just as the burners on a stove top make contact with kettle surfaces in order to boil water, even huge industrial furnaces must have a way to direct heat under controlled conditions. Whether the furnace melts metal into a molten mixture, heat treats a chemical compound to generate a desired reaction, or burns massive amounts of coal to help power a mill assembly, the furnace must offer a mechanism for the heat to impact its intended target. In some designs, a furnace utilizes a heat exchanger to transmit heat from the furnace through liquids. A blower fan protected by a furnace filter may help circulate hot air generated by the furnace.
- Industrial furnaces heat materials to temperatures of 1000 degrees Fahrenheit or more. Capable of reaching higher temperatures than industrial ovens, this equipment typically supplies intense heating capabilities sufficient to cause a transformation in ores, metals, plastics, glass, paper, trash and other types of raw materials. The Industrial Quick Search Manufacturer Directory lists an impressive variety of industrial furnace design, engineering and manufacturing companies.
- Furnace Emissions
- Industrial furnace designers must also give careful consideration to the emissions produced during furnace operations. The furnace configuration should help direct the carbon dioxide resulting from the burning of wood or coal away from a combustion chamber. The incomplete combustion of some fuels generates toxic carbon monoxide. Today, many jurisdictions tightly regulate the quantity and type of emissions released into the air by industrial furnace operators.
- Furnace Insulation
- Finally, every industrial furnace requires insulation. By heating materials to high temperatures, the furnace also creates a searing hot artificial environment. Manufacturers use insulation materials, such as refractory brick or liquids, to help protect the areas immediately surrounding the furnace from the impacts of high temperatures.
The installation of an industrial furnace depends upon manufacturer specifications. The design and size of the furnace, the power source and fuel supply, the specific environmental conditions in the installation location, the maximum temperature capacity, and other engineering specifications may all enter into individual furnace requirements. One especially important consideration relates to the insulation of the furnace; a blast furnace may require the extensive use of refractory brick or other layers of protective material to ensure the high heat generated inside the furnace does not pose a fire hazard.
Standards and Specifications for Industrial Furnaces
In the United States, several government agencies promulgate regulations which influence the operation of industrial furnaces in certain settings. The Occupational Safety and Health Administration (OSHA) issues extensive regulations governing safety in the workplace. Many of these provisions address furnace operations. Additionally, enterprises seeking to design and build industrial furnaces for some purposes, such as waste incineration, need to comply with environmental testing and permit requirements implemented by the Environmental Protection Agency (EPA). State and local regulatory bodies, including land use, planning, building code and zoning departments, also issue rules impacting the safe operation of industrial furnaces.
How to Select a Good Industrial Furnace Manufacturer
Your enterprise can depend upon the Industrial Quick Search Manufacturer Directory website to obtain contact information for a variety of excellent industrial furnace suppliers. Use this resource to enhance your daily operations. You may find it helpful to discuss your unique requirements for this important business asset in depth with a variety of manufacturers in order to identify a firm capable of assisting you with your project. The IQS Directory offers valuable assistance to companies in many industries as they seek to identify a suitable industrial furnace manufacturing firm.
Variations on Industrial Furnaces
One important variation on industrial furnaces, the vacuum furnace, has gained popularity within research and development settings. A high temperature vacuum furnace differs from a conventional furnace design. It heats and cools materials within a vacuum, usually with the assistance of inert shielding gases. Heating applied through a vacuum furnace won't subject materials to oxidation.
Common Machine Accessories For Industrial Furnaces
The design, size and daily operation of an industrial furnace impact the selection of machine accessories. Many industrial furnace operators in the past employed large metal crucibles to help transport molten materials to and from a blast furnace. In low tech environments, such as some traditional glass blowing factories, workers use long poles to retrieve material from an open hearth furnace. Large magnets often help carry scrap metals into an electric furnace. The variety of transport accessories hinges to a great extent upon the industry and the manufacturing facility. Today, most manufacturers have largely automated industrial furnaces through the use of mechanical or robotic accessories.
Equipment required to transport fuel to a large industrial furnace may include natural gas pipelines. Sometimes production facilities adjoin transportation hubs (such as railway terminals) to facilitate easier access to coal or other fuel sources. Chutes and conveyor systems help automate this process.
If an industrial furnace helps heat treat production materials, it may function in close association with gaseous or liquid baths or tanks. Nitriding and many other surface treatments may require these types of accessories. Conveyor belts help transport some materials to and from industrial furnaces in certain industrial settings. Potentially, a wide array of additional equipment supports furnace operations. The individual design specifications of the furnace and the specific industry impact the selection of these commercial products.
- The processes of heating, holding temperature and cooling in order to accomplish a specific objective with the material being heated.
- Banded Structure
- A structure that can be developed from the hot rolling of steel, resulting in a layering effect.
- Bright Annealing
- Annealing done in an extremely hot atmosphere that prevents the occurrence of discoloration and may reduce oxides.
- Heating the surface of steel in contact with carbon-rich solids, liquids or gases in order to add carbon to the material.
- Case Hardening
- Making the surface layer of a steel material substantially harder through heat treating.
- Control Zone
- The separate sensor or instrument of a piece of thermal processing equipment which controls its own temperature individually.
- Controlled Cooling
- A process that is used to deter cracking or hardening or to achieve a desired microstructural result. The controlled cooling process involves cooling the material from an elevated temperature in a selected method.
- Cooling Stresses
- Stresses resulting from irregular temperature distribution during cooling.
- Industrial Ovens
- Enclosures that are used for a wide variety of process heating applications.
- Heating material or products prior to a subsequent thermal or mechanical treatment.
- Quickly cooling from a high temperature.
- Placing parts on a rack or tray prior to heat treatment in order to prevent heat-related distortions and to keep the parts separated.
- A term describing materials that have a very high melting point, making them ideal for linings of furnaces and kilns.
- Surface flaking or chipping resulting from improper heat treatment or material dissociation.
- Spray Quenching
- A quick cooling process in which spray nozzles are used to spray water or other liquids on a part.
- Stabilizing Treatment
- The process of heating a part to slightly above its normal operating temperature and then cooling it to room temperature. Stabilizing treatments are done prior to finishing the part to final dimensions and for the purpose of ensuring dimensional stability.
- Stress Equalizing
- A heat treatment done at low temperatures in order to balance stresses in a cold-worked part without decreasing the mechanical strength imparted to the product through the cold-working process.
- Stress Relieving
- Heating and holding the desired temperature long enough to reduce residual stresses, then slowly cooling.
- Heating at a temperature above the point where equilibrium phase transformation should occur but without actually making a transformation.
- A device that measures temperature through thermal electromotive force.
- Transformation Temperature
- The temperature equilibrium at which a change in the phase occurs.
- Water Quenching
- A quick cooling process using water as the quenching medium. Water quenching is inefficient at the beginning, or hot, stage of the quenching process.