In the graphite electrode industry, it is well known that the raw materials for the production of graphite electrodes are mainly petroleum coke, needle coke, and coal pitch. Among them, low-sulfur petroleum coke and coal-based needle coke are aggregates, coal pitch is used as a binder and an impregnating agent.
Raw Materials for Different Power Graphite Electrodes
RP, HP, UHP graphite electrodes have different aggregate requirements due to particular quality, and the selection demand for raw materials are also different.
In general, regular power graphite electrodes’ aggregates are petroleum coke. High-power graphite electrodes raw materials are composed of 70% high-quality petroleum coke and 30% needle coke. And, ultra-high-power graphite electrodes are 100% needle-shaped coke used.
Strictly Select Graphite Electrode Raw Materials
Rongsheng Group in the raw materials selection is exacting, in order to produce high quality graphite electrode products.
Petroleum coke
Petroleum coke is a petroleum product obtained by thermal cracking of heavy oil such as diesel oil or wax oil.
The petroleum coke color is black and porous, the carbon content accounts for more than 80%, and the ash content is generally below 0.5%. It is widely used in chemical and metallurgical industries, and is the main raw material for producing artificial graphite products and carbon products for electrolytic aluminum.
Petroleum coke can be divided into high sulfur coke (containing more than 1.5% sulfur), medium sulfur coke (containing 0.5% to 1.5% sulfur), and low sulfur coke (containing less than 0.5% sulfur). The production of graphite electrodes and other artificial graphite products is generally produced using low sulfur coke.
Rongsheng Group produces rp graphite electrodes, generally using low sulfur coke (such as petroleum coke with sulfur below 0.5%).
Needle coke
Needle coke is obtained by delayed coking and calcination of coal or oil feedstock.
The anisotropy of physico-mechanical properties of needle coke is very obvious. It has good electrical and thermal conductivity parallel to the long axis direction of the particle, and the coefficient of thermal expansion is low. When extrusion molding, the long axis of most particles is arranged in the extrusion direction.
The manufacture of high-power (hp) or ultra-high-power (uhp) graphite electrodes is generally based on needle coke. The finished graphite electrodes with low resistivity, small thermal expansion coefficient and good thermal shock resistance.
Coal pitch
The coal tar is obtained by refining or modifying the residual part of the coal tar after distillation.
Coal tar is one of the main products of coal tar deep processing. It is a mixture of various hydrocarbons, black high viscosity semi-solid or solid at normal temperature, no fixed melting point, softens after heating, and then melts, and the density is 1.25-1.35g/cm3.
According to its softening point, it is divided into low temperature, medium temperature and high temperature asphalt. The medium temperature asphalt productivity is 54-56% of coal tar.
Coal tar is used as a binder and impregnant in the carbon industry, and its performance has a great impact on the production process and product quality of carbon products. Rongsheng Group’s graphite electrodes binder asphalt uses medium or medium temperature modified asphalt with moderate softening point, high coking value and high β resin. The impregnating agent uses a medium temperature asphalt having a low softening point, a low QI, and good rheological properties.