Industrial furnace is a thermal equipment that heats materials or workpieces by using the heat from fuel combustion or electric energy conversion in industrial production.Broadly speaking, boiler is also an industrial furnace, but it is not traditionally included in the scope of industrial furnace.
Chinese name
Industrial furnace
Foreign name
Industrial furnace
Utilization
Heat from fuel combustion or electric energy conversion
Structure and composition of general industrial furnace:
1. Industrial furnace body, including frame support structurechamber of a stove or furnaceStructure, material conveying system, etc.
2. Heat supply system includes equipment system that provides heat source for materials in industrial furnace, such as energy medium pipeline and equipment system, power transmission system transformer equipment, etc.
3. Smoke exhaust system, including fluechimney, heat exchanger and smoke exhaust auxiliary equipment, etc.
4. Other supporting equipment.
Equipment classification
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Industrial furnaces can be divided into two types according to heating mode: one isFlame furnace(or fuel furnace), using solid, liquid orgaseous fuelThe combustion heat in the furnace heats the workpiece;The second category iselectric furnace, convert electric energy into heat for heating in the furnace.
Industrial furnaces can be divided into two categories according to the thermal system: one is intermittent furnace, also called periodic furnace, which is characterized by that there is no temperature zone in the furnace, the furnace is produced in one shift or two shifts, and the furnace temperature changes in each heating cycle, such asChamber furnaceTrolley furnacePit furnace、Hood furnaceEtc;SecondContinuous furnaceIt is characterized by that the furnace is divided into temperature sections, generally consisting of preheating, heating (high temperature) and soaking (insulation) sections. The furnace is continuously produced in three shifts. During the heating process of industrial furnace, the temperature in each section can be considered unchanged, such as two-stage or three-stage continuous heating furnace, pusher type heating furnace andHeat treatment furnace, annular furnaceWalking beam furnaceVibrating bottom furnaceCupolaAnd lime kiln, etc.
Fuel as energy has great particularity. First, the total amount of resources is limited, and the total amount of fuel is limited, and it will be exhausted one day.Section
2、 The use of fuel is non repeatable, and the use of fuel is unidirectional and irreversible.Third, the use of energy is inefficient.Some losses often occur in the use of fuel, and the degree of loss varies according to the use method and control level.Fourth, fuel will have a negative impact on the environment in the process of use, and waste will often be generated in the process of fuel use, which will cause varying degrees of environmental pollution.
The fuel is burned in the industrial furnace through the burner installed on the industrial furnace, so the performance of the burner is directly related to the fuel consumption of the industrial furnace.Therefore, the performance of the burner should be improved, because only the performance of the burner can meet the heating capacity of the industrial furnace, so that it has a low and stableExcess air coefficientSo that the fuel can be fully improved during usecombustion efficiency So that the burner can adapt to the combustion supporting air with high temperature.
2. Optimize furnace lining structure.
The furnace lining of industrial furnace can be divided into brick lining, charge burning lining and fiber lining.At present, most domestic heating furnaces are built with traditional internal fire bricks, and the heat dissipation and storage of furnace lining can account for 30% - 40% of the total energy consumption.The development trend of furnace building materials is high temperature, high strength and light weight.Reasonable selection of lining materials and optimization of composite lining structure can reduce heat dissipation of furnace body, reduce heat storage loss and achieve good results of energy saving.First of all, the thermal conductivity of the charging furnace lining is much smaller than that of the brick furnace lining, and the furnace body has good air tightness, which can extend the service life and achieve the purpose of energy conservation.In recent years, castables have made great progress in variety and quality, which can meet the requirements of high temperature, rapid cooling and heat resistance in the furnace. The use of castable lining can save about 3% of energy compared with brick furnace.Secondly, the internal fire fiber is an ultra light internal fire material with small basic performance density and thermal conductivity. The furnace building of this material can save energy, materials and improve the productivity of the furnace.useRefractory fiber liningIt can save 7% energy than brick furnace.The development of refractory fiber products, refractory fiber can be used in the high temperature of 1200 degrees, thus promoting the use of refractory fiber.
Refractory fibreThe construction method of the anchor can greatly affect its use effect and service life, and various problems often occur in the use of the traditional anchor method.The new construction method can send the high pressure air of fiber cotton out of the spray gun, and mix the binder with fiber cotton. This method eliminates the seam of the furnace lining, greatly improves its energy-saving effect, and can play the purpose of extending the life of the furnace.infra-redEnergy saving coatingThe energy-saving effect of the coating is very high. This coating can be used on various fuel furnaces with a furnace temperature of 1800 degrees. If it is sprayed on the furnace lining surface, a 0.5mm coating can be formed. The infrared radiation performance of the coating can play a good role in increasing heat efficiency and reducing energy consumption.
3. Improve control level.
Methods to improve control level: First, control fuel combustion.The computer control of industrial furnace should realize the reasonable ratio of furnace temperature, fuel supply, fuel quantity and air quantity. The core of controlling these quantities is the reasonable ratio of fuel.The ratio is controlled by measuring the oxygen content in the flue gas.Second, optimize the mathematical model.In order to control the temperature in the furnace, the mathematical model should be optimized reasonably. It is better to control the temperature in the furnace as a curve using the mathematical model, so as to improve the efficiency of fuel use in the furnace.[1]
Equipment use
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Industrial furnaces often involve heating processes such as smelting, drying, baking and chemical reaction in their production process.andIndustrial furnaceIt is the heating equipment used for these processes.The fuels that provide heat source for these equipment mainly includegaseous fuel, liquid fuelsolid fuelAnd electricity.Use theseheating equipment , easy to burn and electric shock accidents.If gas or liquid fuel is used, once leakage or overflow occurs, it may also constitute a fire and explosion hazard.
Industrial furnace
When industrial furnace is usedfire doorLifting mechanismIt must be intact, and the broken wire of the steel wire rope must not exceed the specified value.The heavy hammer shall be properly configured, and the exposed transmission part shall be equipped with a protective shield.If it is a water cooled furnace door, the pipeline shall be kept unblocked, and the pipeline shall not be frozen in winter.The furnace door shall be equipped with a limit device. When entering and exiting the furnace, there shall be an interlock device to cut off the power supplyPitchwithinBroken filamentThe number shall not exceed 10%, and the counterweight of balance furnace door shall be hung reliably.It is required that the protective device of the exposed transmission part should be kept in the correct installation position with reasonable structure.The steel wire rope pulley of furnace car shall be intact.All pulleys on the furnaceSprocketThe structure is intact and free from defects, and the rotation is flexible.
Industrial furnaceFurnace wall、liningIt shall be tight without leakage.It is required that the furnace wall of the furnace body shall be kept intact without any defect after the refractory materials are heated, corroded, rubbed and chemically etched;The joints between refractory materials and their products shall not leak;At the same time, the integrity of the furnace must be solid.The gas valve shall be able to stop the switch at any position according to the operation requirements, especially to cut off the fuel supply quickly when the flame goes out.The air valve shall be free of looseness and leakage, and its integrity and reliability shall be maintained.Tubing, air duct andHeating pipeThere shall be no crack or leakage.All pipelines for different purposes shall be kept free of leakage, cracks and unblocked, the nozzle shall be unblocked, and the oil temperature and oil (air) pressure shall be kept normal.
Thermometer
Industrial furnacefire doorThe circulating cooling water must be unblocked and the exhaust pipe must be installed on the valve.Temperature measuring instruments (as shown in the following figure "Temperature Measuring Instruments") and instruments shall be sensitive and reliable, and PE shall be reliable.It is required that the instruments and meters shall be sensitive, have correct indications, and be used within the inspection cycle.Ammonia cylinders shall not be exposed to heat, power or strong sunlight.Keep good ventilation, and arrange it on the downwind side of the personnel activity site.
hidden danger
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Industrial furnace is a kind ofHigh temperature equipment, which is connected with fuel oil, gaselectric energy, dust, etc. are closely linked together, which is easy to cause fire, burn, explosion, poisoning, electric shock and other accidents.Therefore, compared with general cold processing equipment, industrial furnaces have many unsafe factors.
Generally speaking, the high temperature during the operation of industrial furnaces is prone to burns, burns and burns;high temperatureMolten saltAnd molten metal will explode when encountering water;Gas andControllable atmosphereIt is explosive gas, and oil lines, oil tanks and oil depots are flammable and explosive facilities. If they are used improperly, explosion and poisoning accidents will occur;The safety protection device of the electric furnace fails, and electric shock will occur after contact;Cyanidation furnacecyanideHighly toxic;When the nitrate furnace is heated to more than 550 ℃, spontaneous combustion will occur;Nitrate andcharcoalCarbon black will explode after being combined.
The environment for industrial furnace repair is poor. Many repair operations are carried out in the furnace. The space is very crowded, the natural lighting is insufficient, and the ventilation condition is poor.Workers are not only injured by dust, but also directly exposed to high temperature, smokeToxic gasandChemical materialsCorrosion.Some furnaces (such asCupola）Up to 10m-20m, due toFurnace stackThe site is narrow, and the repair work is in the form of high altitude interchange and multi-layer operation, which is very dangerous.Therefore, when operating and maintaining industrial furnaces, great attention should be paid to safety issues.Especially when organizing industrial furnaces, great attention should be paid to safety issues.Especially when organizing emergency repair or hot repair of industrial furnaces, attention should be paid to the unfortunate accidents that may be caused by these unsafe factors.
fault analysis
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Electric furnace type industrial furnace
eachReversing valveIt is equipped with a pneumatic triplet, which shall be regularly refueled, cleaned and drained.When refueling, first close the front hand valve of the pneumatic triplet, and then remove the oil cup for refueling. The oil volume of the oil cup should not exceed the full scale.The oil is the atomizing oil specified for the pneumatic triplet, which can also be replaced by 32 # turbine hydraulic oil.The atomization speed of oil should be adjusted to atomize a cup of oil in 3-5 days, and ensure that oil is added once in 3-5 days.When refueling, if necessary, the slag can be removed and drained together.If the pneumatic triplet does not atomize oil, the triplet shall be repaired or replaced in time.
In case of fault alarm of reversing systemControl cabinetThe alarm indicator on the screen will find out the fault point, and deal with it in time after on-site inspection and confirmation to restore the normal operation of the reversing valve.If the gas pipe bursts or falls off, close the compressed air supply valve of the reversing valve and replace the corresponding gas pipe immediately.If the limit switch is loose, it cannot be contactedStemThe circular iron sheet on the can adjust the rotation angle of the limit switch immediately to ensureReversing valveNormal contact between the valve plate and the limit switch contact wheel when the valve plate is at the front and rear limit positions.If the alarm is not caused by 1) and 2) above, check whether the solenoid valve operates normally, and replace the solenoid valve if necessary.If it does not belong to the above 1), 2) and 3) fault alarm, check whether the cylinder leaks inside and whether the wiring of limit switch and solenoid valve is normal.
If the reversing system fails to remove the fault and resume operation in time after the alarm, the following treatment measures can be taken: for example, if the operator cannot remove the fault in time after closing the hand valve after the reversing system alarm, and the exhaust gas temperature exceeds the standard, shut down the induced draft fan and turn down the airGas control valveOrganize corresponding personnel to deal with the fault as soon as possible.The change-over valve shall open the manhole regularly (about a year) to check the use of the sealing ring, valve plate and connecting rod. If necessary, it can be opened at any time for inspection.
Energy saving technology
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1. Use energy-saving combustion technology
One of the main reasons for energy waste of industrial furnaces is the heat loss caused by incomplete combustion.It is caused by chemical incomplete combustion and mechanical incomplete combustion.Incomplete chemical combustion can cause heat loss due to incomplete combustion of carbon monoxide, hydrogen and ammonia combustible gases in exhaust gas, thus causing black smoke from industrial furnaces using loose coal as fuel.High temperature dust in this black smoke andsulfur dioxide、carbon dioxideWill cause pollution to the atmospheric environment.The heat loss of mechanical incomplete combustion is mainly reflected in the incomplete combustion of coal particles, ash and fly ash particles.These ash and particles will also cause great damage to the environment.The oxygen enriched combustion technology can greatly increase the combustion temperature and reduce the amount of combustion supporting air, so as to reduce the amount of flue gas and the loss of gas heat, which can not only save fuel, but also extend the service life of industrial furnace cellar and increase the output of industrial furnace.However, the oxygen enriched combustion technology will produce a large number of by-products such as nitrogen when separating air, which will not only fail to improve the air pollution, but can exacerbate the deterioration of air quality. At the same time, the related equipment will also increase power consumption, and its large-scale use needs to be improved and studied.In industry, we can also adoptHigh temperature air combustion technologyAnd magnetizing the fuel before entering the furnace to achieve the purpose of energy saving and consumption reduction.
2. Waste heat recovery and utilization technology of industrial furnace
A large amount of flue gas generated by industrial furnaces will take away a large amount of heat energy, which is called waste heat.The recovery and utilization of these waste heat can save energy and reduce air pollution at the same time.At present, we can assemble preheater to support combustion with flue gas.It can also be assembledWaste heat boilerTo use the waste heat of flue gas to burn hot water for industrial or domestic use.We can also use the waste heat of flue gas to preheat the already cooled devices or as the heat source of the low-temperature furnace.The most widely used and effective way is to use heat exchanger. When the discharge temperature is below 200 ℃, its energy-saving effect can reach more than 30%.At present, the heat exchangers widely used in China are chip mounted, jet flow type, combined type and cyclone tube type heat exchangers. After their application, the energy-saving benefits are greatly improved.
3. Thermal system and detection technology
At present, the serious energy consumption and pollution of industrial furnaces in China is mainly due to the inadequate or relatively backward regulation and detection technology of fuel and air.This situation puts forward higher requirements for the thermal detection and control technology of industrial furnaces.The use of advanced microcomputer control system and advanced automatic control technology can achieve accurate control and regulation of the system and its related components, such as controlling the furnace temperature and fuel flow of industrial furnace, controlling the oxygen content of flue gas, etc.
4. Improvement of furnace structure and furnace building materials
In order to achieve the purpose of energy conservation and emission reduction, we can improve the furnace structure of industrial furnaces or select new energy-saving materials to improve the efficiency of energy use.Generally speaking, if the furnace space cannot be increased, we can choose to increase the heat exchange area between the furnace and the devices, or use a round furnace body to reduce the area of the external wall of the industrial furnace so as to reduce the heat dissipation loss of the furnace wall.We can also set fans in the furnace of the industrial furnace to strengthen the convection heat transfer function in the industrial furnace.The flow of high-speed airflow in industrial furnace will destroy the surface of the workpiece and hinder the heat transfer to shorten the heating time of the workpiece, so as to quickly increase the temperature of the workpiece. This method will play a more obvious role in small heating furnaces.[2]
Green measures
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In the green development of industrial furnaces, the first problem to be solved is the conversion and absorption of heat energy.At present, the more advanced measures are as follows:
(1) The overall design of industrial furnace is optimized with strengthening heat transfer in furnace as the core.
(2) Strengthen preheating recovery technology and expand technology application fields.For example: use self preheating burner;Regenerative burnerThe preheating temperature shall be increased, or double preheating shall be adopted.
(3) Light lining materials are used to optimize the lining structure.For example, the refractory materials for the top and side walls of the heat treatment furnace are fiber modules and new nano materials, which not only fully meet the process requirements, but also are easy to install, saving the construction time of on-site installation personnel.
At present, the development mode of industrial furnace technology has undergone tremendous changes.From perceptual design to empirical design, experience plus theory, and now rational design, in fact, every step is on the track of "green road".[3]
