Graphite electrode production technology
Raw materials: in carbon production, the commonly used raw materials can be divided into solid carbon raw materials, binder and impregnating agent two categories.Solid carbonaceous materials include petroleum coke, bituminous coke, metallurgical coke, anthracite, natural graphite and graphite crushing.Binders and impregnators include coal pitch, coal tar, anthracene oil and synthetic resins.In addition, the production also used quartz sand, metallurgical coke powder, coke powder and other auxiliary materials.Other special materials are used to produce some special carbon and graphite products (such as carbon fiber, activated carbon, pyrolytic carbon and pyrolytic graphite, glass carbon).
Calcination: the process of heat treatment of carbon raw materials in isolated air at high temperature (1200≤1500℃) is called calcination.Calcination is the first heat treatment process in carbon production.As a result of calcination, the structure and physicochemical properties of various materials containing carbon have undergone a series of changes.
Anthracite and petroleum coke contain a certain amount of volatile, need to calcination.Asphaltene coke and metallurgical coke coking temperature is higher (more than 1000℃), equivalent to the temperature of the calciner in the carbonization plant.It can't burn any more. Just dry it out.However, if asphalt coke and petroleum coke are mixed before calcination, they should be fed into the calcination furnace together with petroleum coke.Natural carbon black and graphite do not need to be calcined.
Kneading: The purpose of kneading is to obtain a uniform, plastic paste.However, due to the change of some factors, the kneading quality will change greatly, resulting in the instability of product quality.The test shows that when the softening point of hard asphalt is 80 ~ 90℃, the temperature of paste should be raised to 168 ~ 174℃.In this temperature range, the best improvement of wettability and bonding property of dry materials by asphalt is that the paste obtained has good plasticity and extrusion properties.Mix dry for 30 minutes, wet for 40 minutes.If the stirring time is too long, the large particles will be destroyed, the original particle composition will be destroyed, so that the volume density of the product is reduced, the plasticity becomes poor, the porosity increases, the mechanical strength decreases
Graphite electrode. PNG
Molding: extrusion molding, vibration molding and molding.Our factory adopts 3500T extruder molding.Before forming, the resulting paste was reduced from 168-174℃ to 116℃ in the cooler.The cooling time should not be less than 8 minutes.After the heat preservation platform is kept for 20 minutes, put the heat preservation paste into the extruder barrel body, and the pressure is generally not less than 25MPa.The product is extruded through a mouth installed in front of the extruder. The extruder is usually produced intermittently. The production is divided into three stages.In the second stage, the electrode density increases gradually as the indenter continues to apply pressure.When the density reaches a certain value, the pressure continues to increase and the density increases slowly.In the third stage, the pressure reaches the limit value and the density tends to be uniform.The electrode is then extruded from the nozzle
Roasting: Roasting is a heat treatment process in which the pressed product is heated at a certain rate in the protective medium in the heating furnace under the condition of air isolation.
The purpose of roasting is:
The main results are as follows :(1) the release of volatiles after calcination of products using coal pitch as binder is about 10%.Therefore, the roasting yield is generally less than 90%.
（2）Coking raw materials are roasted according to certain technological conditions, the binder is coking, and the coke network is formed between the aggregate particles, so that the aggregates with different particle sizes are firmly connected together, and the products have certain physical and chemical properties.Under the same conditions, the higher the coke rate, the better the product quality.The residual carbon content of medium-temperature asphalt is about 50%
(3) During the roasting process, the products with fixed geometry softened and the binder migrated.As the temperature increases, a coking network forms, making the product hard.Therefore, the shape does not change with increasing temperature