Experimental results and discussion

1 Analysis results of thermal reactivity of pitch

From the experimental results Table 4, it can be seen that the low-quinoline refined pitch treated by the scheme 1, scheme 2, and scheme 3 has relatively good coke quality, while scheme 4 and scheme 5 have unsatisfactory coke quality to view the high quality graphite electrode information.

The high QI content of 5^# raw material pitch affects the growth and fusion of the mesophase small spheres. Although the QI content decreases with the addition of 6^# soft pitch, the quality of coke is improved, but even if the QI drops to 0.78 %, the quality of the coke is not ideal.

4^# raw pitch contains more aliphatic hydrocarbons. In the carbonization process, the polymerization reaction begins at a lower temperature, with the temperature range of 440~450 °C. Moreover, the reaction is rapid, so it is difficult for the small spheres to grow and fuse, resulting in more coke inset structures.

2 Differences in pitch thermal reactivity and coking structure

(1) Observing the range of sensitive temperature mutations and the duration of time, scheme 3 is the best, followed by scheme 2, scheme 1;

(2) From the point of view of the coke formation structure, scheme 2 has the best coke quality, followed by scheme 1, scheme 3.

3 The influence of different raw material ratios on thermal reactivity

(1) Add anthracene oil and heavy oil to the medium temperature pitch

It can be seen from Table 4 that adding anthracene oil and heavy oil to the 3* pitch for co-carbonization reaction, there is no big difference in the results of coking, because this experiment is a normal pressure experiment, which can be seen from the raw material data analysis table at 400°C, most of the components of anthracene oil and heavy oil have been distilled out, and only a few of them are coked, so it has little effect on coking.

From the results of the thermal reaction, the addition of anthracene oil and heavy oil can delay the mutation onset temperature, increase the solvation between the TI-QS, QI and TS components in the pitch, and provide a better liquid phase environment for the coking reaction. Therefore, it is better to have a wider temperature abrupt range, and a higher starting point of the abrupt temperature is more beneficial to the growth of the mesophase.

(2) The effect of adding different proportions of 4^# pitch to 6^# refined pitch on thermal reactivity and coking quality

It can be seen from the experimental results in Table 4 that adding 15% to 20% of low-temperature pitch has little effect on the sensitive reaction time range of refined pitch, but the sensitive reaction temperature range is reduced. When the proportion of low-temperature pitch is continued to be added to 30%, the sensitive reaction time range has been further reduced, and the onset temperature of the temperature abrupt change has also been reduced by 5 °C, mainly because the low-temperature tar pitch sensitive reaction is between 440~450 °C, and the range has been narrowed by 10 °C, so the entire coking reaction is advanced, and the reaction speed is also accelerated.

It can be seen from the yield that as the proportion of low-temperature pitch added increases, the yield also decreases simultaneously. This is because the low-temperature pitch component is lighter, and the distillate increases as the temperature rises, and the amount of coke formation is relatively small, resulting in a low yield.

From the perspective of coke formation, the addition of low-temperature pitch affects the quality of coke formation. Under the electron microscope, the color is dark and there are more mosaic structures, mainly because the sensitive reaction temperature of low-temperature pitch is between 440~450°C and mesophase spherules fail to grow and fuse but become focal, resulting in a poor structure for forming focal^[1-2].

(3) The effect of adding different proportions of untreated soft pitch to the refined pitch on the quality of coke

Adding different proportions of soft pitch to the refined pitch after pretreatment is mixed to obtain raw materials with different QI content, and then conduct a thermal reactivity test. It can be seen from Table 4 that with the continuous increase of QI content in the pitch, the coke quality becomes worse and worse. When 29% 5^# pitch is mixed with 71% 6^# pitch, a good wide-area streamlined structure can be seen in some areas after coking, and 100% 5^# pitch is directly used for coking, which has many mosaic structure and the formation of focal structure is very poor.

4 Experimental conclusions 

(1) Under the conditions of this experiment, the coke quality of scheme 1, scheme 2, scheme 3 with low QI pitch is better than scheme 4 and scheme 5.

(2) Under the conditions of this experiment, the coking quality of scheme 2 is the best, scheme 1 is the second, scheme 3 is the third, scheme 4 and scheme 5 are of poor coke quality.

(3) In the case of normal pressure experiment, adding a certain proportion of anthracene oil and heavy oil to the medium temperature pitch has little effect on the coke structure, but has a certain effect on the thermal reactivity.

(4) Adding a certain proportion of 4^# pitch to 6^# refined pitch has a certain influence on the coke quality.

(5) Adding different proportions of 5^# soft pitch to 6^# refined pitch, the structure after being coked is very poor, and a large amount of tree scar structure is observed under the electron microscope.

(6) By controlling the mutation temperature range of the polymerization reaction, appropriately increasing the mutation starting point temperature and prolonging its reaction time, it is conducive to generate more β resin, make the mesophase small spheres grow larger, melt better, and make the quality of coke better contact us to get more technical news.