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Impurity Content of Graphite Electrode

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

Salt in crude oil remains in coke

The salt in the crude oil is mostly enriched in the residue after distillation or cracking, and a small portion is deposited in the furnace tube, vessel, and equipment, and most of the salt in the residue remains in the coke.

Ash content in graphite products

The petroleum coke content of graphite products should generally be less than 0.5%, and the petroleum coke content used to produce high-purity graphite should not exceed 0.15%.


The sulfur content of petroleum coke depends on the sulfur content of the residue.

Sulfur is one of the impurities affecting the quality of petroleum coke. The sulfur content of petroleum coke depends on the sulfur content of the residue, and 30% to 40% of the sulfur in the residue remains in the petroleum coke.

Method for reducing sulfur content in residual oil

The residue containing higher sulfur content is hydrodesulfurized in advance, and the sulfur content in the residue is reduced, thereby reducing the sulfur content of the petroleum coke.

The sulfur content of petroleum coke can be divided into 2 kinds

The sulfur in petroleum coke can be divided into two types: 1. sulfur reefer compounds, such as thioethers, mercaptans, sulfonic acids, and the like. 2. Inorganic compounds of sulfur, such as iron sulfide, sulfate.


Temperature at which the desulfurization effect is achieved

Generally, the desulfurization effect is not large after calcination to about 1300 °C. Only when the calcination temperature is raised to above 1450 °C, the desulfurization effect can be more obvious. A part of the sulfide needs to be discharged at a high temperature of graphitization.

Sulfur is the cause of harmful substances

For the production of graphite products, sulfur is a harmful element. The graphite electrode produced by petroleum coke with a large sulfur content produces a “flat” phenomenon in the graphitization process, which easily leads to product cracking and affects the electrical resistivity of the product.

Petroleum coke volatiles are temperature dependent

The size of the petroleum coke volatiles has a large relationship with the coking temperature, the coking temperature is higher, and the volatile matter is lower. Among them, the kettle type has a lower volatile content than the delayed coking.


Conditions affecting volatiles in petroleum coke produced

The volatiles of petroleum coke produced by delayed coking are not only dependent on the coking temperature, but also related to the charging time of the residue into the coking column and the conditions for blowing steam into the coke layer.

True density measures the quality of petroleum coke

The true density of petroleum coke after calcination at 1300 ° C is the main item to measure the quality of petroleum coke. The higher the true density after calcination, the easier the graphitization of this coke, and the lower the resistivity after graphitization, and the density is proportional to the mechanical strength.

Size of RP Graphite electrode

Item Unit RP
300-500mm 550-800mm
Electric resistivity Electrode μΩm 7.5-8.6 7.5-8.8
Nipple 4.5-6.0
Bending strength Electrode Mpa ≥7.5 ≥6.5
Nipple ≥16.0
Elastic modulus Electrode Gpa ≤9.0
Nipple ≤13.0
Bulk density Electrode g/cm3 1.54-1.62
Nipple 1.70-1.78
CTE(100-600℃) Electrode 10-6/℃ 2.20-2.60
Nipple 1.50-1.90
Ash % ≤0.3


Resistivity and calcination temperature

The unburned green coke resistivity is very high, close to the insulator. After satin burning, the resistivity drops sharply, and the resistivity of the petroleum coke is inversely proportional to the calcination temperature.

Linear expansion coefficient depends on the nature of the residue

The linear expansion coefficient of petroleum coke mainly depends on the nature of the residue. The needle coke is the petroleum coke with low linear expansion coefficient. It is also needle coke. The linear expansion coefficient of petroleum needle coke is slightly higher than that of asphalt needle coke.