What Is an Industrial Furnace?
An industrial furnace is a device used to heat a material.
It is generally used to create high temperature conditions and heat materials or objects. Materials are often metals, such as iron.
Two typical types of industrial furnaces are electric furnaces and combustion furnaces, with combustion furnaces basically being referred to as heating furnaces. Combustion furnaces use air or oxygen mixed with fuel to maintain high temperatures while combustion takes place and heat is transferred to the furnace.
Electric furnaces often use electric heaters or electrodes to heat materials, and some industrial furnaces use induction heating or other non-contact heating methods.
Uses of Industrial Furnaces
Industrial furnaces are used in a variety of industrial fields. Examples include metal processing, glass manufacturing, and waste treatment.
1. Metal Processing
Furnaces are used in metalworking processes such as forging, sintering, and surface treatment. By heating metals to appropriate temperatures, it is possible to change their shape, increase their strength, and perform other processes. It may also be used in heat treatment processes to improve the properties of metals and alloys.
2. Glass Production
Furnaces are also used in glass production. Glass is formed or blow molded by heating glass materials to high temperatures and melting them. They are also used in the firing process of ceramics, where materials are held at a predetermined temperature to allow them to crystallize and harden.
3. Waste Treatment Facilities
Stoker furnaces are also used in waste treatment facilities. Incineration of waste materials at high temperatures will result in weight reduction and decomposition of hazardous substances. Industrial furnaces for waste treatment may also be equipped with ancillary facilities to recover valuable metals.
Principle of Industrial Furnaces
Combustion industrial furnaces heat the inside of the furnace through an oxidation reaction between fuel and oxygen. A combustion, industrial furnace is composed of the following elements:
1. Furnace Body
The furnace body is the space where combustion takes place and is generally constructed of heat-resistant materials such as bricks. In case of extremely high temperatures, the metal structure supporting the furnace body may reach its melting point, so the furnace body is operated with a water-cooled jacket to keep it warm.
2. Fuel Supply System
This system is used to supply fuel to the inside of the furnace. When the furnace temperature drops, the fuel supply is increased to add more heat.
It includes fuel tanks, burners, fuel supply pipes, valves, and ignition devices. Fuel is temporarily stored in the fuel tank and supplied to the burner via supply lines and control valves. The ignition system generally uses a high-voltage arc to create a spark, similar to that of an automobile plug.
3. Oxygen Supply System
This system supplies the oxygen necessary for combustion. It includes an air inlet, blower, etc. The amount of oxygen supplied is adjusted to match the fuel for complete combustion. To increase combustion efficiency, oxygen is supplied directly by liquefied oxygen or other means.
4. Temperature Control Device
This is a mechanism for managing and controlling the temperature inside the furnace. A thermocouple or other temperature sensor is used to read the current temperature, and a controller or other device is used to calculate the target temperature and give instructions to the fuel supply system.
5. Exhaust System
This is a device for discharging combustion gases and waste generated by combustion. It consists of exhaust ducts, exhaust fans, and exhaust gas treatment equipment. Exhaust gases generated by combustion may contain soot and sulfur, so exhaust fans are used to keep negative pressure inside the exhaust ducts to prevent leakage, and flue gas desulfurization treatment is performed to exhaust the gases.
Structure of an Industrial Furnace
Industrial furnaces consist of various devices such as heat exchangers,” “blowers, fuel controls, burners, pilots, igniters, control circuits, and thermostats, and their specifications are modified according to the required application and function. The main factors that affect changes are the type of fuel and the method of starting combustion.
The materials and construction of industrial furnaces also change depending on the temperature at which they are used. For example, if an industrial furnaces are not selected with the right material, volume, and shape for the production volume, the amount of fuel used, and the heating temperature, the furnace insulation may be damaged, the walls may deteriorate, and furnace damage may be accelerated, or the heating efficiency may decrease, leading to higher operating costs.
Industrial Furnace Burners
Burners are essential for industrial furnaces that use fuels such as gas or oil. Different types of burners are available depending on the operating temperature of the industrial furnaces, the application, and the type of fuel used.
Energy-saving burners are sold to reduce the heat loss of burners. An example of an energy-saving burner is a burner with an integrated heat exchanger, called a recuperative burner. Normal burners have piping that radiates heat when preheated air is sent to the burner, but recuperative burners have no piping, so heat radiation can be prevented.
Another energy-saving burner is called a regenerative burner. This burner combines the burner and the heat storage unit into a single unit, resulting in a high exhaust heat recovery rate. This type of burner has two sets of burners with integrated burner and heat storage unit that burn in alternating cycles.
Fuel for Industrial Furnaces
Recently, in order to meet environmental and cost reduction requirements, carbon dioxide emissions from combustion have been reduced, and low-carbon industrial furnaces are being developed as part of the deoxygenation effort. One example of a low-carbon industrial furnaces are one that uses hydrogen or ammonia, which does not produce carbon dioxide when combusted.
On the other hand, hydrogen has a high combustion rate and high temperature, while ammonia has a low combustion rate and low temperature, and not all of these issues have yet been solved. Because they require different equipment than natural gas or city gas, they are still under development.
Types of Industrial Furnaces
In addition to combustion industrial furnaces, there are also electric furnaces and vacuum furnaces. Electric furnace is a type of industrial furnace that heats a heating element using air energy. Heat is generated by electrical resistance and transferred to the heating object. Induction furnaces, which generate an induction current in a metal object and heat it, are also sometimes used for metal heating.
Vacuum furnaces are industrial furnaces that heat under a high vacuum or controlled atmosphere. Heating in a vacuum can control material properties and prevent oxidation and contamination.
Other Information About Industrial Furnaces
Steel Material Changes in an Industrial Furnace
Steel materials tend to take a long time to cool down after abstraction, resulting in a less uniform composition and making it difficult to use the material as it is. Therefore, heating in an industrial furnace activates the movement of metal elements and alleviates the non-uniformity of composition.
In addition, the performance of steel materials is optimized by precisely controlling crystal grains of a few micrometers and precipitates of a few nm in size. Grains and precipitates are non-uniform and coarse in the ingot state. Therefore, by repeating proper heating and cooling in an industrial furnace, the microstructure is prepared to be fine and uniform.