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Residue In Graphite Electrodes

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

The carrier weight loss includes two aspects of loss

Oxidation starts from the surface of the graphite electrode, oxidation causes the surface structure to be loose, and a small amount of graphite particles on the surface is dropped. At this time, the weight loss is not only the weight loss of oxidation, but also the weight of the graphite particles falling, which is collectively referred to as the weight loss of the carrier.
 

The meaning of the beginning of oxidation temperature

The initial oxidation temperature means that the weight loss is 1% after 24 hours of oxidation at this temperature.


 

The temperature at which graphite undergoes oxidation

At normal temperature, the carbon does not undergo an oxidation reaction. When heated to about 350 ° C, there is a significant oxidation reaction, and the graphite is heated to about 450 ° C to undergo an oxidation reaction.
 

Factors affecting the rate of oxidation reaction

The rate of oxidation reaction is related to the size of the reaction area at that time, the porosity of the material, and the gas pressure.
 

The lattice parameter can measure the degree of graphitization

The closer the lattice parameter of artificial graphite is to the lattice parameter of ideal graphite, the higher the degree of graphitization. When high-quality raw materials (such as needle coke) are used to increase the graphitization temperature, artificial graphite with a lattice parameter very close to ideal graphite can be obtained.


 

Method for determining the degree of graphitization of graphite electrode

Ray diffraction analysis. It uses X-ray diffraction on the crystal plane of the crystal to obtain the relevant lattice parameters. It plays an important role in the study of graphite crystal structure. Common methods include X-ray powder photography or X-ray diffractometry.
 

Indirect speculation of the degree of graphitization

The degree of graphitization can be indirectly estimated by measuring the true density.
The degree of graphitization is indirectly estimated by measuring the resistivity.


 

Petroleum coke is closely related to residual oil

Petroleum coke is a solid product obtained by coking reaction of residual oil. The quality of petroleum coke is closely related to the type and composition of raw material residue.
 

Definition and type of residue

Residues come from crude oil processing, crude oil properties and processing processes, and the resulting residue properties are different. There are vacuum residue (straight-flow residue), secondary processing residue (thermal cracking oil, catalytic cracking residue, light oil cracking residue).
 

Conditions for generating a sponge-like structure

If the content of aromatic hydrocarbons in the vacuum residue is small, the content of colloid and asphaltene is large, and a honeycomb or sponge-like structure is mainly formed during coking.

Parameter of UHP graphite electrode

Item Unit UHP
300-600mm 650-800mm
Electric resistivity Electrode μΩm 4.8-5.8 4.6-5.8
Nipple 3.8-4.5 3.8-4.5
Flexural strength Electrode Mpa 10.0-14.0 10.0-14.0
Nipple 20.0-26.0 22.0-26.0
Elastic modulus Electrode Gpa 9.0-13.0 10.0-14.0
Nipple 15.0-18.0 15.0-18.0
Bulk density Electrode ≥g/cm3 1.68-1.74 1.70-1.74
Nipple 1.77-1.82 1.78-1.84
CTE(100-600℃) Electrode x10-6/℃ 1.1-1.4 1.1-1.4
Nipple 0.9-1.2 0.9-1.2
Ash   0.3 0.3

 

Method for improving the quality of petroleum coke

The thermal cracking residue has a higher aromatic content than the vacuum residue. Therefore, adding a part of the thermal cracking residue as a coking raw material in the vacuum residue can improve the quality of the petroleum coke.
 

Residue that can produce needle coke

The raw materials for producing needle coke are low-sulfur, aromatic-rich and less asphaltene-containing and colloid-containing residual oils, such as thermal cracking residual oil, catalytic clarifying oil, light oil cracking residue oil, and oil extraction oil.
 

Residue formation of coke

The coking reaction of the residue in the coking tower to form coke is an extremely complicated process of thermal decomposition and thermal polycondensation. When the residue enters the coking tower, various complex decomposition and fracture reactions and dehydrogenation reactions occur under the influence of temperature. And polycondensation reaction.

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