The Length Wise Graphitisation furnace is an internally heated tandem graphitisation furnace, invented by the American Castner, and is divided into horizontal internal series and three-dimensional internal series.
The main difference between the Length Wise Graphitisation process and the Acheson graphitisation process is that the product is heated directly through the electrode itself, without the need for resistive materials to generate heat. This is also the main feature of the Length Wise Graphitisation process compared to the Acheson graphitisation process. Since the Length Wise Graphitisation process has no fillers, it can reduce the heat output, which can reduce the heat output by 10% and reduce the power consumption by 20%~35%.
Diagram of a Castner lengthwise graphitization furnace. a - Mixture of Coke and Sand, b - Bricks, c - Carbon Electrodes, d - Refractory Material, e - Rods to Graphitize, f - Granulated Coke.
The Length Wise Graphitisation furnace has the characteristics of high thermal efficiency and short power transmission time. It only takes 1~2 h in the high temperature stage. When the product is directly heated, the resistance is uniform, and the product yield is high. Since the 1980s, most carbon plants in Germany, the United States, Japan and other countries have adopted the Length Wise Graphitisation process to produce large-scale ultra-high-power graphite electrodes. The furnace type of Length Wise Graphitisation furnace can be divided into I type, U type, W type and plum blossom type. Among them, there are many U-shaped furnaces, including single-column and multi-column ones, including two-fold, four-fold and even multiple-fold ones.
Developing LWG furnace is the trend. Because the current density of the column is the same, the difference of the electrode resistivity is very small; secondly, the resistivity of the two ends of the LWG product is slightly lower than that of the middle part (the resistivity of the two ends of the Acheson furnace graphitized product is higher than that of the middle part), which is conducive to reducing the resistance of the connection and alleviating the reddening phenomenon of the connection when users use it. Therefore, the quality uniformity of electrodes produced by LWG furnace is better than that of Acheson furnace, and it is more suitable for the production requirements of electric arc furnace steelmaking.
The Length Wise Graphitisation furnace needs to be heated quickly in the early stage of power transmission, so as to achieve the purpose of energy saving. The specific heating rate should be controlled in accordance with the characteristics of the blanks of each manufacturer. Controlling the temperature at about 2000 ℃, that is, the temperature at which the graphitization process starts, is beneficial to use the latent heat released by the graphitization process to accelerate the completion of graphitization. The larger the transformer capacity and the higher the furnace core temperature, the faster the graphitization process will proceed, and the high-power operation time is relatively short, the heat loss is low, and the unit power consumption is relatively low. The constant power output rectifier transformer can effectively increase the temperature of the furnace core. Adding a certain amount of graphite powder in the batching has certain benefits to reduce the unit consumption of graphitization, and the unit consumption of long electrode is lower than that of short electrode.