Graphitization catalyst: some substances with catalytic effect are added to the ingredients to promote the graphitization of roasted products at a lower temperature or in the phase

The graphitization degree is improved at the same temperature. The graphitization of products is generally measured by measuring the graphite lattice constant D or calculated by Franklin
P value indicates. Scholars at home and abroad have carried out excessive research work on catalytic graphitization, such as observation by electron microscope,
Some other generic particles that can form intercalations promote the regular arrangement of carbon atoms in the hexagonal network plane, forming a graphite structure. can
It promotes the continuous growth of graphite crystal and reduces the layer Yang J distance of graphite character. Table 3 14 lists some research results.
It shows that certain metal oxides do have different catalytic effects, and the better ones are the oxidation of titanium and iron
Things. High sulfur petroleum coke (l_48% sulfur per unit) was used as raw material, and iron oxide powder was added into the formula
See table 3.15 for analysis results. Foreign carbon factories add a small amount of titanium dioxide to the proportion of graphite electrodes for experiments,
The resistivity of the finished electrode obviously drops, but the melting point of titanium is high, it is difficult to cut, there are more residual components and the product is hard
It is difficult to machine the finished electrode. Petroleum coke with very low sulfur content is used to produce graphite electrodes abroad. About 1.0% Fe: 03 was added to the mixture,

It mainly suppresses the gas expansion in the graphitization process, which is conducive to reducing crack scrap.
The blank is installed in the graphitization furnace. When the temperature rises above 1400 ℃, hydrogen, nitrogen, sulfur and other elements will be expressed as H:, H: s, CS2,
N：，NH。 A large number of studies show that nitrogen is released at 1400 ~ 1900 ℃, and sulfur is released at 1400 ~ 1900 ℃
The element is released in the range of 1700-2100 ℃. At this time, the plastic coke pore wall is subjected to the pressure of the exhaust gas,
The volume expands. It can be inferred that the expansion is mainly caused by the escape of sulfur, nitrogen and their compounds. Therefore, in the
The expansion of the electrode during 1700 ~ 2100 ℃ is called gas expansion. The mechanism of inflation is still under in-depth study, and most scholars
It is believed that the gas expansion of petroleum needle coke is caused by sulfur. A small amount of inflation inhibitor is added during batching to delay impurities
For the release of qualitative gas, the expansion inhibitor usually uses iron oxide powder, and the inhibitor reacts with sulfur to form sulfide, then at a higher
It decomposes elemental sulfur at a relatively low speed at the temperature of. The effect of metal oxide on preventing gas expansion is due to the stability of its sulfide
Qualitatively, when iron oxide is used as the inflation inhibitor, the sulfur escape is delayed to 2100 ~ 2500 ℃.