The purpose of producing graphite products with a binder is to bond various particles as aggregates, and to make the kneaded hot paste have good plasticity for molding. In the roasting process of the formed raw product, the pitch coke produced by the coking of the binder itself firmly connects the aggregate particles into a whole.
The quality and physical and mechanical properties of various graphite products depend to a large extent on the nature of the binder and the infiltration, penetration and bonding force of the binder to the carbon material particles. The binder used in graphite products are made of thermoplastic materials. Thermoplastic material is solid at room temperature, it melts into liquid when it is slightly heated, and can be adsorbed by carbon material particles to bond to each other into a paste. After the paste is press-formed, it can be hardened and fixed in shape after a little cooling, so it is easy to stack and Handling. The binder should have a higher carbon content and residual carbon ratio (that is, the percentage of coking residual carbon after roasting).
The surface of the particles of petroleum coke and pitch coke is a honeycomb structure, and the specific surface area is large, and the adsorption of pitch is good. Therefore, graphite products using petroleum coke and pitch coke as raw materials need more binders. Graphitized crushed and graphitized metallurgical coke have better adsorption of pitch. Therefore, when graphitized crushed or graphitized metallurgical coke is added to the ingredients, the amount of binder should be appropriately increased. The molding method of the product is directly related to the amount of adhesive. For example, extrusion molding requires the paste to have better plasticity, so the amount of binder should be more; on the contrary, the amount of binder for compression molding can be less. Coal pitch is generally used after melting. This is because the coal pitch entering the plant contains a lot of moisture and some mechanical inclusions. The coal tar pitch is unloaded in the melting tank, melted and stood for 3-7 days at a temperature of 120-150℃, so that the moisture in the pitch is reduced to less than 0.2%. Anthracene oil or coal tar should also be heated and dehydrated in the melting tank to less than 0.5%. While melting, the mechanical inclusions also settle to the bottom of the tank.
The temperature of the molten asphalt should not be too high, so as to prevent the volatiles in the asphalt from decomposing and volatilizing in advance and reducing the cohesiveness of the asphalt. In some cases, if the asphalt has little moisture, solid asphalt can also be used directly. Before use, the solid asphalt is broken into smaller particles.
Post time: Feb-28-2022