Abstract: It is widely used in various laboratories, industrial and mining enterprises, scientific research institutions for element analysis and determination, as well as general small parts quenching, annealing, tempering and other heat treatment operations.

Calcination:

Heat treatment at a certain temperature in air or inert gas flow is called calcination or roasting

Calcination is the process of thermal dissociation or crystal transformation of natural or synthetic compounds; At this point, the compound dissociates into a simpler component or undergoes a crystal transformation when heated. The thermal dissociation of carbonates is called roasting. Calcination operations can be used to directly process mineral raw materials to meet subsequent process requirements, or to produce chemical concentrates through chemical beneficiation post-processing to meet user requirements for products.

The main physical and chemical changes that occur during the calcination process are: (1) thermal decomposition. Excluding volatile impurities such as chemically bound water, CO2, NOx, etc., at higher temperatures, oxides may undergo solid-phase reactions to form active chemical compounds; (2) Recrystallization can obtain a certain crystal shape, crystal size, pore structure, and specific surface area; (3) Microcrystals are appropriately sintered to improve mechanical strength.

The main factors affecting the calcination process are:

Calcination temperature, gas phase composition, thermal stability of compounds, etc. Therefore, based on the different thermal stability of various compounds (such as carbonates, oxides, hydroxides, sulfides, oxygen-containing acid salts, etc.), controlling the calcination temperature and gas phase composition can selectively change the composition of certain compounds or undergo crystal transformation. Then, corresponding methods can be used to remove impurities and separate and enrich useful components.

Muffle furnace: It is translated from English Muffle furnace. Muffle means package, furnace means stove, and melting pot means furnace. The common names for muffle furnaces in China are as follows: electric furnace, resistance furnace, Maofu furnace, and muffle furnace. A muffle furnace is a universal heating device According to its appearance, it can be divided into box furnace tube furnace crucible furnace. MaFu furnaces are divided into domestic MaFu furnaces and imported MaFu furnaces according to nationality. Divided by heating elements, there are electric furnace wire muffle furnace, silicon carbon rod muffle furnace, and silicon molybdenum rod muffle furnace; According to the rated temperature, it is generally divided into: 900 degree series muffle furnace, 1000 degree muffle furnace, 1200 degree muffle furnace, 1300 degree muffle furnace, 1600 degree muffle furnace, and 1700 degree muffle furnace. According to the controller, there are several types: pointer table, ordinary digital display table, PID regulation control table, program control table; There are two types of insulation materials: ordinary refractory bricks and ceramic fibers. The muffle furnace system operates in a periodic manner and is used for element analysis and determination in laboratories, industrial and mining enterprises, and scientific research institutions. It is also used for heating small steel parts during quenching, annealing, tempering, and other heat treatments. The high-temperature muffle furnace can also be used for high-temperature heating such as sintering, dissolution, and analysis of metals and ceramics

Features:

(1) This product has a wide range of applications and can be used for weight analysis, including determination of organic matter and ash content in coal.

(2) The heating element is set on the inner four walls to accelerate the temperature rise and provide uniform heating.

(3) The heating element is made of special refractory materials and concealed inside the inner wall to avoid contact with corrosive gases, steam, etc., thereby extending its service life.

(4) The muffle furnace and control part are set separately, so that even under long-term operation, the electronic temperature controller can accurately grasp the temperature.

(5) The shell of the muffle furnace is double layered, and the circulation of air between them can maintain a low temperature on the surface, so there is no need to worry about scalding people.

(6) The temperature indicated by the digital settings and display panel.

Maintenance and precautions:

When the muffle furnace is used twice or after a long period of disuse, it must be dried. The baking time should be four hours at room temperature of 200 ℃. 200 ℃ to 600 ℃ for four hours. When in use, the furnace temperature should not exceed the rated temperature to avoid burning out the electric heating elements. It is prohibited to pour various liquids and easily soluble metals into the furnace. The Maofu furnace operates at temperatures below 50 ℃, which means that the furnace wire has a longer lifespan.

2. The muffle furnace and controller must be operated in a location with a relative humidity not exceeding 85%, free from conductive dust, explosive gases, or corrosive gases. When metal materials containing oil or grease need to be heated, a large amount of volatile gases will affect and corrode the surface of the electric heating element, causing it to be destroyed and shorten its lifespan. Therefore, timely prevention and proper sealing of containers or appropriate openings should be taken during heating to eliminate the problem.

3. The muffle furnace controller should be limited to use within the ambient temperature range of 0-40 ℃.

4. According to technical requirements, regularly check whether the wiring of the electric furnace and controller is in good condition, whether there is any jamming or retention phenomenon when the pointer of the indicator moves, and use a potential difference meter to calibrate the instrument for errors caused by fatigue, balance failure, etc. of magnetic steel, demagnetization, wire expansion, and spring fragments.

5. Do not suddenly pull out the thermocouple at high temperatures to prevent the jacket from exploding.

6. Keep the furnace clean regularly and promptly remove oxides and other substances inside the furnace.

Usage precautions:

Flammable and explosive materials should not be baked inside the furnace to avoid danger! Do not heat volatile corrosive substances, otherwise it will affect their service life