Introduction and application of artificial graphite
Synthetic graphite is a polycrystalline similar to crystallography. There are many kinds of artificial graphite and different production processes.
In a broad sense, all the graphite materials obtained after carbonization of organic matter and graphitization at high temperature can be collectively referred to as artificial graphite, such as carbon (graphite) fiber, pyrolytic carbon (graphite), foam graphite, etc.
In the narrow sense, artificial graphite usually refers to the bulk solid materials, such as graphite electrode, isostatic graphite, made by batching, mixing, molding, carbonization (known as roasting in industry) and graphitization, with low impurity content of charcoal raw materials (petroleum coke, asphalt coke, etc.) as aggregate, coal pitch as binder.
There are many forms of artificial graphite, including powder, fiber and block, while the narrow sense of artificial graphite is usually block, which needs to be processed into a certain shape when used. It can be regarded as a kind of multiphase material, including the graphite phase transformed by carbon particles such as petroleum coke or asphalt coke, the graphite phase transformed by coal pitch binder coated around the particles, the particle accumulation or the pores formed by the coal pitch binder after heat treatment, etc. Generally speaking, the higher the heat treatment temperature, the higher the degree of graphitization. Industrial production of artificial graphite, the degree of graphitization is usually less than 90%.
Compared with natural graphite, artificial graphite has weak heat transfer and electrical conductivity, lubricity and plasticity, but artificial graphite also has better wear resistance, corrosion resistance and low permeability than natural graphite.
The raw materials for producing artificial graphite mainly include petroleum coke, needle coke, asphalt coke, coal pitch, carbon microspheres, etc. Its downstream products mainly include graphite electrode, pre-baked anode, isostatic graphite, high purity graphite, nuclear graphite, heat exchanger and so on.
The product application of artificial graphite is mainly reflected in the following aspects:
1. Graphite electrode: With petroleum coke and needle coke as raw materials and coal pitch as binder, the graphite electrode is made by calcination, batching, mixing, pressing, roasting, graptitization and machining. It is widely used in electric furnace steel, industrial silicon, yellow phosphorus and other equipment by releasing electric energy in the form of arc to heat and melt the charge.
2. Pre-baked anode: made of petroleum coke as raw material and coal pitch as binder through calcination, batching, mixing, pressing, roasting, impregnation, graphitization and machining, it is generally used as conductive anode of electrolytic aluminum equipment.
3. Bearing, sealing ring: conveying corrosive media equipment, widely used artificial graphite made of piston rings, sealing rings and bearings, work without adding lubricating oil.
4. Heat exchanger, filter class: artificial graphite has the characteristics of corrosion resistance, good thermal conductivity and low permeability. It is widely used in the chemical industry to make heat exchanger, reaction tank, absorber, filter and other equipment.
5. Special graphite: with high quality petroleum coke as raw material, coal pitch or synthetic resin as binder, through raw material preparation, batching, kneading, pressing, crushing, mixing kneading, molding, multiple roasting, multiple penetration, purification and graphitization, machining and made, generally including isostatic graphite, nuclear graphite, high purity graphite, used in aerospace, electronics, nuclear industry sectors.