Detailed explanation of graphitization furnace and auxiliary equipment
Feb 17,2023
The graphitization furnace is a resistance furnace designed according to the principle of Joule's law, heated directly and operated intermittently. For the graphitization furnace, the furnace core is composed of products installed in the furnace and a small amount of resistive material. It is a heating resistor and a heated object. For the inner tandem furnace, the product loaded in the furnace is the furnace core, which is graphitized by its own heat.
Graphitization furnace generally includes furnace bottom groove, furnace end wall, conductive electrode, furnace side wall, channel steel, etc. Generally, the bottom refers to the bottom of the rectangular trough between the two end walls of the graphitizing furnace. On the concrete foundation of the high-temperature graphitization furnace, lay 1~3 layers of red bricks first, then lay a layer of ordinary refractory bricks, and use refractory bricks to surround the end wall ash carbon block. If the movable side wall type is adopted, a row of tiger head bricks shall be laid on both sides to form the furnace bottom groove.
The conductive end wall is built at both ends of the furnace to become the end wall of the furnace, and the outer wall is made of gray carbon brick or refractory clay brick, high alumina brick, etc. The inner wall is constructed with graphitized blocks. In order to strengthen the protection of the burner so that it will not be deformed and damaged under the impact of thermal expansion or mechanical force, there are brackets made of channel steel or angle steel on both sides of the burner, which are fixed with steel braces. The gap between the inner wall and the outer wall should be filled with graphite powder and compacted. It is required that the moisture content of the graphite powder is less than 0.5%, the particle size is 0-5mm, the ash content is less than 1.5%, and the powder resistivity is not more than 35010-6 ohm-m.
The purpose of loading graphite powder is:
(1) sealing insulation.
(2) At the same time, there are some average flow effects.
Many manufacturers choose to stick a layer of refractory brick or waste anode to cover the graphite powder on the furnace head. The main function of the cover is to enhance the sealing effect and prevent the thermal insulation material of the upper cover from mixing with the graphite powder of the furnace head. When graphite powder is mixed in the heat-insulating material of the upper cover, hard lumps are easily formed.
Conductive electrodes pass through the inner and outer end walls to form an integral body with the end walls. The electrode is provided with a copper plate, and the copper plate is connected with the electrode through a clip. Use multiple thin copper sheets to buffer the connection between the copper plate and the aluminum bus bar. The electrode is connected to an electrically conductive end wall within the furnace near one end of the furnace. The conductive electrode may be a graphitized electrode or a graphite block. If the graphitized electrode is used as the conductive electrode, it will bring great difficulties to the masonry of the graphitization furnace. Therefore, the graphitized block is often used as a conductive electrode, which should have high conductivity, and the allowable current density should be more than 11 A/cm2. So many manufacturers now use secondary fired graphitized blocks as conductive electrodes.
Take into account various reasons such as the degree of contact. As a result, the conductivity of each conductive electrode is uneven. In order to prolong the service life, the number and cross-section of the graphitized conductive electrode should be selected, and the current density should be below 10 amperes per square centimeter. Otherwise, it is easy to break, which will easily lead to the fire accident of the conductive end wall of the furnace head (tail) in the later stage of power transmission.
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