Processes To Produce Graphite Electrodes

　　Processes to produce impregnated shapes

　　Impregnation is an optional stage carried out in order to improve the properties of the final product. Tars, Pitches, resins, molten metals and other reagents can be added to the baked shapes (in special applications graphite shapes can also be impregnated) and other reagents are used to fill the voids formed in the carbonised material. Soaking with hot coal tar pitch with or without vacuum and autoclaving are used. Various impregnating techniques are used depending on the product such as but batch or quasi-continuous operations are used. The impregnation cycle usually involves preheating the shapes, impregnation and cooling. A hardening reactor may also be used. Electrodes that shall be impregnated can be preheated by the waste heat of the thermal oxidiser. Only speciality carbons are impregnated with various metals. The baked or graphitised components may be impregnated with other materials, e.g. resins or metals. Impregnation is carried out by soaking, sometimes under vacuum and sometimes under pressure, autoclaves are used. Components that have been impregnated or bonded with coal tar pitch are rebaked. If resin bonding has been used, they are cured.

　　Processes to produce rebaked shapes from impregnated shapes

　　Baking and re-baking Re-baking is only used for impregnated shapes. Green shapes (or Impregnated shapes) are rebaked at temperatures up to 1300 °C using a variety of furnaces such as tunnel, single chamber, multiple chamber, annular and push rod furnaces depending on the size and complexity of the product. Continuous baking is also carried out. The furnace operations are similar to those used for electrode shapes baking process, but the

　　furnaces are usually smaller.