Graphite is an allotrope of carbon, containing only carbon, and it is very common in everyday life. For example, pencils are made of graphite.
Graphite is made up of layers of carbon planes stacked in a hexagonal layered structure. In the same layer, the individual carbon atoms are hand in hand with each other and are closely connected, but there is almost no connection between the layers.
Coal used in daily use, charcoal after burning wood is also carbon, and even expensive diamonds (ie diamonds) are also composed of carbon. Graphite, diamond, coal, etc. are different only because of the different arrangement of carbon atoms.
To make an image metaphor, each carbon (C) atom has 4 small hands. When these 4 small hands and the small hands of other carbon (C) atoms are connected hand in hand in different ways, graphite, diamond and coal are formed. and other substances.
Graphitization is the process of generating graphite. In layman’s terms, it is the process of converting carbon materials of other crystal structures into graphite crystal structures.
Graphitization improves the bulk density, electrical conductivity, thermal conductivity, corrosion resistance and machinability of the product, and it is a key process in the production of artificial graphite anodes.
Due to the different molecular structures, the aggregation states of these atomic groups are different, and the degree of difficulty of graphitization is also different. Anthracite, petroleum coke, needle coke atomic groups are roughly oriented in parallel, with few cross-connections, which belong to easily graphitized coke. The aggregation of the internal structure of sugar carbon and carbon black is messy, and these materials are microporous and contain a large amount of oxygen and hydrogen-oxygen groups, so it is difficult to graphitize. Pitch coke, metallurgical coke, etc. are between the above two cases.
The selection of easily graphitized raw materials is a prerequisite for the production of high-quality artificial graphite. The artificial graphite produced by petroleum coke has low ash content and good electrical conductivity. The graphite obtained from pitch coke at the same temperature is harder and has a slightly higher specific resistance. Metallurgical coke has higher ash impurities and higher specific resistance, both of which are inferior to petroleum coke.
High temperature is the main external condition for the transformation of carbon into graphite. For the same carbon material, the higher the temperature, the better the degree of graphitization. Different carbon materials start graphitization at different temperatures. The residence time at high temperature is also related to the degree of graphitization, but the effect is far less obvious than that of increasing the temperature.
For example, petroleum coke generally begins to graphitize at 1700°C, and does not approach the ideal graphite structure until above 2300°C, while pitch coke begins to graphitize at about 2000°C.
The graphitization process mainly includes laying the furnace bottom, building the furnace core, loading the furnace, sending electricity, cooling, releasing the furnace and packaging.
A production cycle of graphitization usually takes 20-30 days, and the power transmission time during this period is about 40-100 hours. In order to make full use of the transformer, one transformer will be combined with several furnaces for cyclic production to ensure the continuous operation of the power supply device.
The construction period of graphitization capacity generally takes one to two years.