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Graphitized power supply

Release time:2019-11-04 From: Zhengnai Industry in China

Graphitized resistor

Use metallurgical coke or graphitized metallurgical coke as resistance material
The resistance material acts as “resistance heating”, and metallurgical coke or graphitized metallurgical coke particles are usually used as the resistance material. In the whole graphitization process, the calcined product is mainly heated by the heat generated by the electric current through the electric resistance material, so the initial resistance of the electric resistance material and the electric resistance change of the electric resistance material in the whole electrification process are very important for the operation of the graphitization furnace. When the graphitized metallurgical coke with lower resistance is used as the resistance material, the core resistance is lower when the current is started, and the range of the resistance of the furnace core is smaller during the energization process, which is beneficial to reduce the temperature difference between the various parts of the furnace core. It can be energized with a faster rising power without increasing the crack waste, but at the same time has a certain influence on the resistivity of the product. In order to increase the resistivity of the product, metallurgical coke and graphitized coke are mixed in a certain ratio and used as a resistive material (must be uniformly mixed).


 

Graphitization insulation

Graphitization insulation material plays the dual role of insulation and electrical insulation in the graphitization furnace. Under normal conditions, the temperature on both sides and the top of the furnace core is lower than the temperature in the middle of the furnace core. If the insulation effect is not good, the furnace temperature difference is greater. The requirements for the insulation are: 1. The thermal conductivity is low (ie, the insulation performance is good). 2. High resistivity and good electrical insulation performance. 3. Although there is a certain chemical change in use, it is formed of a porous material and does not hinder the discharge of gas in the furnace. 4. Generally do not react with the products in the furnace at high temperatures. 5. Cheap and easy to purchase in large quantities. At present, the Acheson graphitization furnace uses quartz sand and coke powder as the heat preservation material, and the effect of adding some wood chips is better because the heat preservation effect and the gas permeability of the heat preservation material are enhanced.
 

Bottom material

In order to protect the furnace bottom made of clay refractory bricks, it is necessary to lay a layer of heat insulation and insulation on the masonry to prevent overheating and leakage of the furnace bottom. The large graphitization furnace firstly deposits quartz sand with a thickness of about 600 mm on the refractory brick masonry as an insulating layer and compacts it, and then lays a layer of furnace bottom material composed of coke powder and quartz sand on the tamping quartz sand.


 

Power curve

The energization curve is an electric power rise curve when the graphitization furnace is energized. The method of obtaining high temperature for various types of graphitization furnaces is to use the thermal effect generated by the current passing through the conductor. The work (heat generation) of the current passing through the conductor is proportional to the resistance of the conductor and proportional to the square of the passing current.
 

Effective core section

The space occupied by baking products and resistors in graphitizing furnace is called furnace core, which includes upper and lower cushions and resistors on both sides. Its vertical cross section is called furnace core section. The annual production capacity of a group of graphitizing furnaces is mainly determined by the capacity of power supply units, and is also related to the length of the selected graphitizing furnaces and the effective cross section of the hearth, which is restricted by the current density of the selected hearth.
An increase in the effective cross-section of the furnace core means an increase in the amount of furnace charge, that is, an increase in production.

Size of HP graphite electrode


Item Unit HP
300-500mm 550-700mm
Electric resistivity Electrode μΩm 5.5-6.8 5.5-7.0
Nipple 4.0-5.5
Bending strength Electrode Mpa ≥10.0 ≥8.5
Nipple ≥18.0
Elastic modulus Electrode Gpa ≤13.0
Nipple ≤15.0
Bulk density Electrode g/cm3 1.62-1.70
Nipple 1.72-1.80
CTE(100-600℃) Electrode 10-6/℃ 1.80-2.20
Nipple 1.50-1.80
Ash % ≤0.3

 

Furnace current density

The current density through the unit cross section of the furnace core during the energization of the ink furnace is expressed in A/cm2. The core current density is the main factor that restricts the final furnace temperature of the graphitization furnace. The higher the current density of the furnace core, the higher the final temperature of graphitization, and the lower the resistivity of the produced graphite electrode.
 

Graphitized electricity consumption

The amount of electricity consumed per ton of roasting product during the graphitization process is expressed in kW·h. There are two calculation methods for graphitization power consumption: one is to calculate the amount of electricity consumed per ton of roasting products in the graphitization furnace, and the other is to combine the process yield rate and count the amount of electricity consumed per ton of qualified products after graphitization.


 

Graphitization consumption

The graphitization consumes the average energization time (in min) per ton of roasting product in a graphitization furnace.
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