Chinese name: industrial kiln, also known as periodic kiln features: kilns produced intermittently, such as chamber kiln, trolley kiln, vertical kiln, etc. The history of industrial kilns, different types of kilns, controlled atmosphere kilns, towering kilns, coreless induction kilns, flame kilns, electric kilns and industrial kilns has played a very important role in human progress. In Shang Dynasty, a relatively perfect copper smelting kiln appeared in China, with a kiln temperature of 1200℃ and an inner diameter of 0.8m During the Spring and Autumn Period and the Warring States Period, people further mastered the technology of raising the temperature of copper smelting furnace, thus producing cast iron. 1794, a straight tube furnace for smelting cast iron appeared in the world. Later, in 1864, Martin, a Frenchman, built the first steel-making flat kiln heated by gas fuel by using the regenerative kiln principle of Siemens Company in Britain. He used the regenerator to preheat the air and gas at high temperature, so as to ensure the temperature above 1600℃ required for steelmaking. 1900 or so, the power supply is gradually sufficient, and various resistance furnaces, electric arc furnaces and cored induction furnaces are used. In 1950s, coreless induction furnaces developed rapidly. Later, electron beam kiln appeared, which can strengthen surface heating and melt high melting point materials by using electron beam to impact solid fuel. The furnace used for forging heating was originally a hand forging furnace, and its working space was a concave groove filled with coal. Air for combustion was supplied from the lower part of the groove, and the workpiece was buried in coal for heating. This kind of kiln has low thermal efficiency and poor heating quality, and can only heat small workpieces. Later, it was developed into a semi-closed or fully enclosed chamber kiln made of refractory bricks, which can use coal, gas or oil as fuel or electricity as heat source, and the workpiece is heated in the kiln chamber. In order to facilitate the heating of large workpieces, there are trolley furnaces suitable for heating steel ingots and billets, and there are also well furnaces for heating long bars. After the 1920s, various mechanized and automated kiln types appeared, which can improve the productivity of kiln and improve working conditions. With the development of fuel resources and the progress of fuel conversion technology, the fuel of industrial kilns has gradually changed from solid fuels such as lump coal, coke and pulverized coal to gas and liquid fuels such as producer gas, city gas, natural gas, diesel oil and fuel oil, and various combustion devices adapted to the fuels used have been developed. The structure, heating technology, temperature control and atmosphere of industrial kiln will directly affect the quality of processed products. In forging heating furnace, increasing the heating temperature of metal can reduce the deformation resistance, but too high temperature will cause grain growth, oxidation or overheating, which will seriously affect the quality of workpiece. In the heat treatment process, if the steel is heated above the critical temperature and then suddenly cooled, the hardness and strength of the steel can be improved; If it is heated to a point below the critical temperature and then cooled slowly, the hardness of steel can be reduced and the toughness can be improved. In order to obtain the workpiece with accurate size and smooth surface, or to reduce the metal oxidation protection mold and reduce the machining allowance, various less oxidation heating furnaces can be used. In an open-flame furnace with less oxidation heating, reducing gas is produced by incomplete combustion of fuel, and the oxidation loss rate can be reduced to below 0.3% by heating the workpiece. Different types of kilns control atmosphere Kilns control atmosphere Kilns can be used for gas carburizing, carbonitriding, bright quenching, normalizing, annealing and other heat treatments, so as to change the metallographic structure of the workpiece and improve the mechanical properties. In fluidized particle kiln, the combustion gas of fuel or other fluidizing agent applied from the outside forcibly flows through the graphite particles or other inert particles layer on the kiln bed, and the workpiece can be buried in the particle layer to realize intensified heating, and can also be subjected to various non-oxidation heating such as carburizing and nitriding. In salt bath kiln, using molten salt as heating medium can prevent the workpiece from oxidation and decarbonization. Cast iron smelting in Tian Chong kiln is often affected by coke quality, air supply mode, kiln material condition and air temperature, so it is difficult to stabilize the smelting process and obtain high-quality molten iron. The hot blast stove can effectively increase the temperature of molten iron, reduce the alloy burning loss and reduce the oxidation rate of molten iron, thus producing high-grade cast iron. Coreless Induction Kiln With the appearance of coreless induction kilns, Tian Chong kilns tend to be gradually replaced. The melting work of this induction furnace is not limited by any brand of cast iron, and it can be quickly switched from melting one brand of cast iron to melting another brand of cast iron, which is conducive to improving the quality of hot metal. Some special alloy steels, such as ultra-low carbon stainless steel, steel for rolls, steel for steam turbine rotors, etc., need vacuum degassing and argon stirring in a refining furnace to refine high-purity and large-capacity molten steel. Flame kiln The fuel source of flame kiln is wide and the price is low, which is convenient to adopt different structures according to local conditions and is conducive to reducing production costs. However, it is difficult to control the flame kiln accurately, resulting in serious environmental pollution and low thermal efficiency. Electric kiln Electric kiln is characterized by uniform kiln temperature, easy automatic control and good heating quality. According to the energy conversion mode, electric furnaces can be divided into resistance furnaces, induction furnaces and electric arc furnaces. The heating capacity of kiln calculated by unit time and unit kiln bottom area is called kiln productivity. Gases are liquefied gas, natural gas, coke kiln gas, city gas, rotary kiln gas, mixed gas, producer kiln gas, high kiln gas, etc. Industrial kiln is a thermal equipment that uses the heat of fuel combustion or electric energy conversion to heat materials or workpieces in industrial production. Broadly speaking, pot kilns are also industrial kilns, but they are not included in industrial kilns. There are towering kilns, induction kilns, resistance kilns, arc kilns, vacuum kilns, flat kilns and crucible kilns. Used for melting metal. There are sand drying kilns for baking sand molds, iron alloy drying kilns and casting annealing kilns. The forging workshop has various heating furnaces for heating steel ingots or billets before forging and heat treatment furnaces for relieving stress after forging. In the metal heat treatment workshop, there are various heat treatment furnaces for annealing, normalizing, quenching and tempering to improve the mechanical properties of the workpiece; The welding workshop has preheating furnace before welding and tempering furnace after welding for welding parts; In the powder metallurgy workshop, there is a heating kiln for sintering metal. Suitable for other industries, such as metal melting furnace, ore sintering furnace and coking furnace in metallurgical industry; Distillation kilns and cracking kilns in petroleum industry; Producers in the gas industry; Cement kilns and glass melting and annealing kilns in silicate industry; Baking kiln in food industry, etc. Gas industrial kilns Industrial kilns are divided into two types according to heating methods: one is flame kiln (or fuel kiln), which uses the combustion heat of solid, liquid or gas fuel in the kiln to heat the workpiece; The second type is electric kiln, where electric energy is converted into heat energy for heating. The working room of chamber flame kiln is called kiln chamber, which consists of kiln bottom, kiln wall and kiln top. When used as or, there are many types of kiln bottom structure, which can be called car bottom kiln, push plate kiln, stepping kiln, roller kiln, chain kiln, ring kiln and so on. The bottom of a flame furnace for smelting (such as copper smelting) is a concave molten pool for storing molten metal. The shape of the molten pool is rectangular, circular or elliptical. There is a liquid metal outlet at the bottom of the molten pool. There are kiln doors, peepholes and slag outlets on the kiln wall. There are two kinds of kiln roof structures: vault and ceiling. The former is used for furnaces with smaller widths, while the latter is used for furnaces with larger widths. In a high-temperature flame furnace, the flame directly enters the furnace. If lump coal is used as fuel, it is necessary to set up a solid fuel combustion chamber separately, and the flame will cross the crater and enter the furnace. If pulverized coal, gas or oil is used as fuel, a burner is needed. Rotary kiln Rotary kiln or rotary kiln is used in metallurgical industry for direct reduction of iron ore, roasting of alumina minerals, roasting of clay minerals and roasting, volatilization, segregation and drying of various bulk raw materials. The kiln body of rotary kiln is cylindrical, made of thick steel plate and lined with refractory material. The kiln body is horizontally installed on the roller of the support, slightly inclined (4 ~ 6%). The length-diameter ratio of the kiln body is between 12: 1 and 30: 1. During operation, the kiln body rotates at a uniform speed. Due to the inclination and rotation of the kiln body, the kiln material gradually moves from high to low. The kiln material gradually heats up during the movement, and the physical and chemical changes occur in turn. The temperature of rotary kiln is generally controlled below the melting point of kiln material. Electric Kiln Electric Kiln is a metallurgical kiln which provides heat by electric heating effect-Shen photoelectric kiln. Electric kiln equipment is usually complete, including electric kiln body, electrical equipment (electric kiln transformer, rectifier, frequency converter, etc. ), switches, auxiliary appliances (chokes, compensation capacitors, etc. ), vacuum equipment, detection and control instruments (electrical instruments, thermal instruments, etc. ), automatic adjustment system, kiln machinery and equipment (feeding and discharging machinery, kiln tilting device, etc. ). The power equipment and detection and control instruments of large electric furnaces are generally concentrated in the power supply room of electric furnaces. Compared with oil-fired kiln, electric kiln has the following advantages: the atmosphere in the kiln is easy to control, and even vacuum can be pumped; The material is heated quickly, the heating temperature is high, and the temperature is easy to control; The production process is easy to realize mechanization and automation; Good labor hygiene conditions; High thermal efficiency; Good product quality, etc. The heating capacity of industrial kiln calculated by the detection controller in unit time and unit kiln bottom area is called kiln productivity. The faster the heating rate of the kiln, the greater the loading capacity of the kiln and the higher the productivity of the kiln. Generally speaking, the higher the productivity of kiln, the lower the unit heat consumption per kilogram of material. Therefore, in order to reduce energy consumption, it is necessary to produce at full capacity, improve the productivity of the kiln as much as possible, and automatically adjust the ratio of fuel and combustion-supporting air to the combustion device to prevent excess or shortage of air. In addition, it is necessary to reduce the heat storage and heat dissipation loss of kiln wall, the heat loss of water cooling parts, the radiation heat loss of various openings and the heat loss taken away from kiln flue gas. The ratio of the heat absorbed by metal or material when heated to the heat supplied to the kiln is called the thermal efficiency of the kiln. The thermal efficiency of continuous kiln is higher than that of intermittent kiln, because continuous kiln has high productivity and continuous operation, the heating system of kiln is in a stable state, and there is no periodic heat storage loss of kiln wall. In addition, because there is a preheating kiln material in the kiln chamber, part of the residual heat of the flue gas is absorbed by the cold workpiece entering the kiln, which reduces the temperature of the flue gas leaving the kiln. The basic measures to improve the thermal efficiency of kiln are: fully improve the combustion efficiency and strengthen the heat transfer to the workpiece; Continuous production and full load work as much as possible; Set up a preheater to preheat air and gas and recover the waste heat of flue gas; Refractory materials with low specific heat capacity and low thermal conductivity are used to reduce the heat storage and heat dissipation losses of kiln walls. In order to keep the temperature of the kiln constant and realize the specified heating rate, besides determining the excellent kiln structure according to the technological requirements, the types of preheater and kiln furniture, the types of fuel and combustion device, and the smoke exhaust mode of industrial kiln, it is also necessary to adjust the controllable variables such as fuel and combustion-supporting air or electricity through various control units to realize the automatic control of kiln temperature, kiln atmosphere or kiln pressure. High-grade industrial products require high uniformity of temperature field in kiln and high stability and controllability of combustion atmosphere, which cannot be realized by traditional continuous combustion control. With the appearance of wide-section and large-capacity industrial kiln, pulse combustion control technology must be adopted to control the uniformity of temperature field in the kiln. The high-temperature coating for kiln is to make the constant temperature resistance reach the high temperature of kiln, and the temperature resistance should be improved to 1800℃. It has the properties of high temperature resistance, stable coating work, high temperature and fire resistance, corrosion resistance, oxidation resistance, fire resistance, heat insulation and energy saving, and continuous wear resistance and impact resistance in industrial production kilns. The specific high-temperature paint is as follows: kiln high-temperature heat insulation paint, using special high-temperature solution, which can reach 1800℃ and can be directly barbecued in front of the flame for a long time. The thermal conductivity of the coating is only 0.03W/m.K, which can effectively inhibit and prevent infrared radiation and heat conduction. The inhibition efficiency of thermal insulation can reach about 90%, which can inhibit the heat radiation and heat conduction loss of high temperature objects. Insulation, pressure resistance and curing can be reprocessed, and it is convenient to brush irregular objects. The functional coating can be directly coated on the object for several millimeters. The high temperature resistant anticorrosive coating for kiln can reach 1700℃. The functional coating can protect the substrate from corrosion, oxidation and sealing protection in high temperature gas (smoke), fire and high temperature liquid (seawater and sewage). The coating has high stability and wear resistance, and will react with other active molecules at high temperature, with long service life. Wear-resistant waterproof coating for kiln has a temperature resistance as high as 600℃, and its main component is pure corundum, and its strength at room temperature can reach above 2 10 MPa. The functional coating can be coated in a thin layer and can be used in industry, metallurgy, mining, construction, transportation, medicine, light industry and so on. It is not sticky in cavitation friction, hardness friction and impact friction. In addition, the functional coating is acid and alkali resistant, waterproof and has good adhesion. The invention has the advantages of high temperature resistance1700 DEG C, good waterproof and sealing performance, convenient painting, long service life, acid and alkali resistance, aging resistance, self-cleaning and wear resistance, and can well protect the substrate from corrosion by water, liquid and steam, thus prolonging the service life of the substrate. The coating with high-temperature sealing function can be directly painted on high-temperature flue, chimney, concrete, various metals, fiber surfaces, insulation bricks and the like. Furnace flue gas anticorrosion coating can be used for long-term anticorrosion: it has excellent corrosion resistance and corrosion resistance to H2S and other media in flue gas. Compared with the traditional glass flake anticorrosive functional coating, it has better ductility and firm adhesion. Super adhesion: The coating has strong adhesion to the substrate. The metal oxide nano-materials and rare earth oxide ultrafine powder contained in the functional coating composition help the coating to form a dense interface transition layer, so that its comprehensive thermodynamic properties match the matrix. High temperature resistance: the base material and filler of this product are composed of high temperature resistant inorganic materials, and the smoke-proof coating of the coating can withstand 600℃. A high-temperature resistant transparent anticorrosive heat-insulating coating for kiln is composed of high-purity silicate solution and ultrafine inorganic metal oxide. The temperature resistance can reach 1700℃, and the functional coating is completely transparent at room temperature and high temperature without any volatile odor. After coating functional paint, the original color of the object will not be affected. The functional coating can form an interpenetrating network structure with the surface of the object after being coated on the inorganic material substrate, and has good adhesion, and the transparent functional coating has certain heat insulation and flame retardancy. The high-temperature far-infrared radiation resistant coating for kiln is a kind of energy-saving functional coating with high temperature resistance (temperature can reach 1700℃), strong emissivity (0.95), corrosion resistance and high wear resistance. By coating infrared radiation with functional coatings, the heat exchange in the furnace is improved, the intensity and uniformity of the temperature field in the furnace are improved, and the fuel is burned more fully, thus improving the thermal efficiency, greatly improving the thermal efficiency of refractories, reducing energy consumption, saving energy and prolonging the service life of furnace lining. High temperature resistant inorganic adhesive coating for kiln is a new product with independent intellectual property rights. The temperature resistance can reach 1800℃, the high-temperature resistant inorganic adhesive has strong adhesion, is non-corrosive to metal matrix, can maintain good adhesion and corrosion resistance at high temperature, and has long service life. Ceramic insulating paint for kiln is resistant to high temperature, the temperature can reach 1700℃, and it can withstand strong electric field without breakdown. High temperature insulating coatings coating has high mechanical strength and good chemical stability, and can resist aging, water and chemical corrosion. At the same time, it also has the ability to resist mechanical shock and thermal shock. Pulse combustion control is an intermittent combustion mode, which uses pulse width modulation technology to control the temperature of the kiln by adjusting the duty ratio (on-off ratio) of combustion time. The fuel flow can be preset by pressure adjustment, and once the burner works, it will be in a full load state, ensuring that the gas outlet speed of the burner will not change. When the temperature needs to be raised, the combustion time of the burner is prolonged and the intermittent time is reduced; When cooling is needed, the combustion time of the burner is reduced and the intermittent time is prolonged. The main advantages of pulse combustion control are high heat transfer efficiency and greatly reducing energy consumption. The uniformity of the temperature field in the kiln can be improved. Accurate control of combustion atmosphere can be achieved without on-line adjustment. The load regulation ratio of the burner can be improved. The system is simple, reliable and low cost. Reduce the production of nitrogen oxides. The regulation ratio of common burners is generally around 1: 4. When the burner works at full load, the gas flow, flame shape and thermal efficiency can reach the best state. When the burner flow is close to its minimum flow, the heat load is minimum, the gas flow is greatly reduced, the flame shape can not meet the requirements, and the thermal efficiency drops sharply. When the high-speed burner works below 50% full load flow, the above indexes are far from the design requirements. This is not the case with pulse combustion. In any case, the burner has only two working states, one is working at full load, the other is not working, and the temperature can be adjusted only by adjusting the time ratio of the two states. Therefore, pulse combustion can make up for the defect of low regulation ratio of the burner, and the burner can still work in the best combustion state when low temperature control is needed. When the high-speed burner is used, the gas injection speed is fast, so that negative pressure is formed around it, so that a large amount of flue gas in the kiln is sucked into the main gas and fully stirred and mixed, which prolongs the residence time of flue gas in the kiln and increases the contact time between flue gas and products, thus improving the convective thermal efficiency. In addition, the flue gas and gas in the kiln are fully stirred and mixed, so that the temperature of the gas is close to the temperature in the kiln, the uniformity of the temperature field in the kiln is improved, and the direct thermal impact of the high-temperature gas on the heated object is reduced. Pulse combustion control technology is widely used in industrial kiln industry, which consists of high-speed burner and industrial kiln control system. Pulse combustion technology is used to complete the heating and temperature control of industrial furnaces. For gas kiln, the internal temperature field and temperature wave force are 2 C, for fuel (diesel) kiln, the internal temperature field and temperature fluctuation are 3 C, and the effect is better for kiln with heavy diesel as fuel. When the internal temperature of the common burner is lower than the spontaneous combustion temperature of the fuel, the flame of the burner will be extinguished immediately after the fuel is interrupted, and the combustion will not continue, and the temperature in the kiln will not be affected, thus solving the flameout problem. Using the most advanced atomization technology-bubble atomization technology, the atomization effect of the burner is better and less atomization medium is used. Kilns that used to burn light diesel oil can now burn heavy diesel oil. In practical application, when the duty ratio of combustion is adjusted by ordinary pulse width modulation, when the duty ratio is close to 0% or 100%, the intermittent or combustion time is too short, and the field operation effect is not ideal, so we introduce the concept of minimum time, set the minimum time of intermittent and combustion to 3 seconds, and extend the corresponding combustion and intermittent when the duty ratio is close to 0% or 100%. As a new technology, pulse combustion has broad application prospects and can be widely used in ceramics, metallurgy, petrochemical and other industries. It will play an important role in improving product quality, reducing fuel consumption and reducing pollution. It is an innovation of automatic control in industrial kiln industry and will become the development direction of industrial kiln combustion technology in the future.