Precautions and common problems of muffle furnace

Maintenance and repair of muffle furnace:
1. When using the muffle furnace for the first time or reusing it after long-term shutdown, the furnace should be dried first, and the furnace temperature should be between 200 ℃ and 600 ℃ for four hours
2. During long-term use, the furnace temperature of the muffle furnace shall not exceed the maximum furnace temperature.
3. The muffle furnace and controller should be operated in a place with an ambient temperature of 0-50 ℃, a relative humidity of not more than 90%, and no conductive dust, explosive gas, and corrosive gas.
4. It is prohibited to inject various liquids and molten metals into the furnace of the muffle furnace.
5. When replacing the muffle furnace wire, first remove the chimney behind the furnace, open the baffle behind the furnace, take out the intermediate insulation brick, and then extract the furnace core. After replacing the furnace wire, install it as usual
6. When using, the door of the muffle furnace should be gently closed and opened to prevent damage to the machine parts.
In order to extend the service life of the muffle furnace, it is necessary to take samples from the muffle furnace in a timely manner after the muffle furnace is used, exit the heating, and turn off the power supply.
How should the constant temperature zone of the muffle furnace be measured?
Insert a thermocouple into the muffle furnace so that its thermal node is located in the center of the muffle furnace as a reference, and insert another thermocouple or tree thermocouple into the furnace as a measuring appliance. Heat the muffle furnace to its operating temperature (900 ℃ or 815 ℃), and use a temperature controller to stabilize the furnace temperature at this temperature according to the instructions of the reference thermocouple. Move the measuring thermocouple along the front and rear, left and right, and up and down directions. The moving distance depends on the temperature gradient of the muffle furnace. The distance can be larger when the gradient is small, and smaller when the gradient is large, generally 1 to 2cm each time. After each movement, maintain a constant temperature for 3 to 5min at the predetermined temperature, Read the temperature indicated by the millivolt measurement thermocouple, and finally find out the constant temperature zone of the muffle furnace based on the temperature of each measurement point.
Service conditions and user provided materials of muffle furnace:
• Temperature: 0 ℃~40 ℃
• Relative humidity: ≤ 85%
Power supply: AC220V ± 22V, 50Hz ± 1Hz.
The use environment should be free of strong corrosive gases, strong electromagnetic equipment, and strong magnetic fields, with good ventilation.
• The product should be firmly placed on the workbench in the laboratory, with a spacious indoor area and moderately bright light.
Before starting up and working, carefully inspect the muffle furnace and other instruments and facilities used, especially check that the wiring of the electrical system is correct and reliable, and promptly handle any abnormalities found.
• Operators are professionally trained personnel who are familiar with the operating instructions and related supporting electromechanical, instrument, facilities, etc. Unqualified operators are not allowed to work.
• Self equipped air switch or knife switch above 40A.
• Self prepared ash dishes, ash racks, volatile crucibles, and volatile crucible racks.
The principle of muffle furnace:
A rectangular integral furnace lining made of refractory material. A heating element made of resistance wire wound into a spiral shape is threaded through the wire grooves on the upper, lower, left, and right sides of the inner furnace lining. The furnace is of a sealed structure. The furnace mouth brick and furnace door brick of the electric furnace are made of lightweight refractory materials. The refractory fiber and expanded perlite products are used to build the insulation layer between the inner furnace and the furnace shell. The heating element is heated with high temperature iron chromium aluminum electrical resistance wire, which can effectively protect the resistance wire from being damaged by being wound outside the furnace. However, the supporting temperature controller should be protected from vibration and should not be placed too close to the electric furnace to prevent overheating that may affect the normal operation of the control part.
Classification of muffle furnaces:
The classification of muffle furnaces can be based on their heating elements, operating temperatures, and controllers, as detailed below:
1) According to heating elements, there are: electric furnace wire muffle furnace, silicon carbon rod muffle furnace, silicon molybdenum rod muffle furnace;
2) According to the use temperature, it is generally divided into: muffle furnaces below 1000 degrees Celsius (XL-1 box type high-temperature furnace), muffle furnaces between 1100 degrees Celsius and 1300 degrees Celsius (SRJX-4-13 silicon carbon rod muffle furnace), and muffle furnaces above 1600 degrees Celsius are silicon molybdenum rod muffle furnaces.
3) According to the controller, there are the following types: PID regulation control table (SWK-B type thyristor digital display temperature controller), program control table (WSWK-5 microcomputer time temperature programmable controller);
4) According to thermal insulation materials, there are two types: ordinary refractory brick (XL-1 box type high-temperature furnace) and ceramic fiber (JXL-620 energy-saving fast intelligent muffle furnace).
Installation, use and precautions of muffle furnace:
The muffle furnace is a periodic operation type used by laboratories, industrial and mining enterprises, and scientific research institutions for elemental analysis and determination, as well as for heating during heat treatment such as quenching, annealing, and tempering of ordinary small steel parts. The high-temperature muffle furnace can also be used for high-temperature heating such as sintering, dissolution, and analysis of metals and ceramics.
1. It should be placed on a solid cement table top, and there should be no flammable and explosive substances around it
2. When using alkaline substances to melt the sample or burn the sediment in the furnace, the operating conditions should be strictly controlled. It is best to lay a layer of refractory plate on the furnace bottom in advance to prevent corrosion of the furnace.
Installation and use of muffle furnace:
1. After opening the package, check whether the muffle furnace is intact and whether the accessories are complete. Ordinary muffle furnaces do not require special installation, but only need to be placed flat on a flat indoor floor or shelf. The controller should avoid vibration and should not be placed too close to the electric furnace to prevent overheating from causing internal components to not work properly.
2. A thermocouple is inserted into the furnace for 20-50mm, and the gap between the hole and the thermocouple is filled with asbestos rope. It is best to use compensation wires (or insulated steel core wires) to connect thermocouples to the control. Pay attention to the positive and negative electrodes, and do not connect them in reverse.
3. Additional power switches need to be installed at the power cord entry point to control the main power supply. To ensure operation, the electric furnace and controller are reliably grounded.
4. Before use, adjust the thermometer indicator to zero. When using compensation wires and cold junction compensators, adjust the mechanical zero point to the reference temperature point of the cold junction compensators. When not using compensation wires, adjust the mechanical zero point to the zero scale position, but the indicated temperature is the temperature difference between the measurement point and the cold junction of the thermocouple. Source: Exam University
5. After checking the wiring and confirming it is correct, cover the controller housing. Adjust the set pointer of the temperature indicator to the desired operating temperature, and then turn on the power supply. Turn on the power switch. At this time, the green light on the temperature indicator is on, the relay starts working, the electric furnace is powered on, and the ammeter displays current. As the internal temperature of the electric furnace increases, the pointer of the temperature indicating instrument gradually rises, indicating that the system is operating normally. The temperature rise and constant temperature of the electric furnace are indicated by the traffic lights of the temperature indicator, with the green light indicating the temperature rise and the red light indicating the constant temperature.
6. Video operation:
Smart muffle furnace installation click="Smart muffle furnace installation instructions (video);";
Installation and Operation Instructions for Ordinary Muffle Furnace and Controller (Video)
Maintenance and precautions:
1. When the muffle furnace is used for the first time or is used again after long-term shutdown, the furnace shall be dried. The oven drying time should be four hours at room temperature of 200 ℃. 200 ℃ to 600 ℃ for four hours. During use, the maximum furnace temperature should not exceed the rated temperature to avoid burning down the electric heating elements. It is prohibited to inject various liquids and easily soluble metals into the furnace. It is best for the Maofu furnace to operate below the maximum temperature of 50 ℃, where the furnace wire has a longer service life.
2. The muffle furnace and controller operate in a place where the relative temperature does not exceed 85% and there is no conductive dust, explosive gas, or corrosive gas. When metal materials such as grease are heated, a large amount of volatile gas will affect and corrode the surface of the heating element, causing it to be destroyed and shorten its life. Therefore, during heating, it is necessary to timely prevent and properly seal the container or properly open a hole to eliminate it.
3. The muffle furnace controller should be limited to use within the ambient temperature range of 0-40 ℃.
4. According to technical requirements, regularly and regularly check whether the wiring of the electric furnace and controller is in good condition, and whether the pointer of the indicator is stuck or stuck during movement. Use a potential difference meter to calibrate the error increase of the instrument caused by magnetic steel, demagnetization, wire expansion, fatigue of spring pieces, and balance damage.
5. Do not pull out the thermocouple suddenly at high temperatures to prevent the jacket from exploding.
6. Always keep the furnace clean and timely remove oxides and other things from the furnace.
7. The box furnace and controller are placed on a flat indoor ground or workbench. The controller should avoid vibration and its position should not be too close to the resistance furnace to prevent overheating and prevent electronic components from working properly.
8. Insert the thermocouple into the resistance furnace and fill the gap with asbestos rope.
9. When using a silicon carbide rod high temperature resistance furnace at normal power, the temperature rises to about 800 ℃. You can appropriately increase the furnace power (adjust the controller output knob). After reaching the required temperature, adjust it to standard power. Do not use the furnace with excessive power for a long time.
10. Install the ground wire.
11. Pay attention to the furnace door opening structure, and be careful when loading and unloading materials to avoid damaging the silicon carbide rod.
12. Pay attention to the fastening of the silicon carbide rod and the carbon rod clamp in the silicon carbide rod muffle furnace, and regularly check the contact of the wire clamp and the tightness of the screws.
13. Alkaline substances, such as alkali, alkaline earth, oxides of heavy metals, and low melting point silicates, can oxidize silicon carbide rods at high temperatures.
14. The oxidation reaction of air and carbonic acid gas on silicon carbide rods in a muffle furnace at high temperatures is mainly manifested in increasing the resistance of the silicon carbide rods and isolating the intrusion of water vapor. Chlorine and hydrogen chloride decompose silicon carbide rods at high temperatures.
15. Silicon carbide rods age due to long usage. The resistance value increases relatively, and the controller knob is adjusted to the maximum output, but the rated power still cannot be reached. At this time, you can contact our company to change the connection method or replace the silicon carbide rod with a new one.
16. If the silicon carbon rod muffle furnace breaks during the use of the silicon carbon rod, it is necessary to replace the silicon carbon rod with the same resistance value or the silicon carbon rod with a resistance error of 20%.
Analysis of the influence of ash and volatile matter in coal on boiler equipment by muffle furnace
1、 Muffle Furnace Analysis of the Impact of Ash and Volatile Matter in Coal on Boiler Equipment (JXL-620 Energy Saving Fast Intelligent Muffle Furnace)
"The ash content of coal refers to the production of ash, commonly referred to as ash, as the residue left after a series of complex reactions such as decomposition and combination of minerals occur when all combustibles in coal are completely burned down at a certain temperature.". Ash is one of the harmful impurities in coal. The higher the ash content, the lower the calorific value. When burning high ash coal, the impacts on the operation of power plant boilers include:
1. Affecting normal combustion and increasing accidents. As the ash content increases, the combustion temperature in the furnace decreases. If the ash content increases from 35% to 55%, the theoretical combustion temperature decreases by an average of about 5% for each 1% increase in ash content, which makes it difficult for the pulverized coal to ignite, causing poor combustion, and even flameout. At the same time, it increases the wear of the heating surface, which also brings adverse effects on economic operation.
2. Affect the economy of the unit. Burning high ash coal can also increase ash accumulation on the heating surface of the boiler, increase thermal resistance, reduce the utilization of heat energy, and increase mechanical incomplete combustion heat loss and physical heat loss caused by ash removal. On the other hand, the increase in ash content also increases the power consumption of the coal mill.
3. Severe environmental pollution increases the workload and difficulty of ash and slag treatment systems. Burning ash rich coal increases the amount of ash, resulting in an increase in dust and ash discharged from power plants. Ash is an industrial waste residue, which can seriously pollute the environment and damage ecology if not handled properly.