Needle coke is a high quality variety vigorously developed in carbon materials. Its appearance is a porous solid with silver gray and metallic luster. Its structure has obvious flowing texture, with large but few holes and slightly oval shape. It is the raw material for producing high-end carbon products such as ultra-high power electrode, special carbon material, carbon fiber and its composite material.
According to the different raw materials, needle coke can be divided into oil needle coke and coal needle coke. Needle coke produced from petroleum residue is oil needle coke. The needle coke produced from coal tar pitch and its fraction is coal series needle coke.
The indexes that affect the quality of needle coke include true density, sulfur content, nitrogen content, volatile matter, ash content, thermal expansion coefficient, resistivity, vibration density, etc. Because of the different specific index coefficient, needle coke can be divided into super grade (excellent grade), first grade and second grade.
The performance differences between coal and oil needle coke include the following points.
1. Under the same conditions, the graphite electrode made of oil needle coke is easier to shape than coal needle coke.
2. After making graphite products, the density and strength of graphitized products of oil-series needle coke are slightly higher than that of coal-series needle coke, which is caused by the expansion of coal-series needle coke during graphitization.
3. In the specific use of graphite electrode, the graphitized product of oil needle coke has a lower coefficient of thermal expansion.
4. In terms of physical and chemical indexes of graphite electrode, the specific resistance of graphitized product of oil needle coke is slightly higher than that of coal needle coke product.
5. The most important is that coal measure needle coke expands when the temperature reaches 1500-2000 ℃ in the process of high temperature graphitization, so the temperature rise rate should be strictly controlled, not fast temperature rise, it is best not to use the series graphitization process production, coal measure needle coke by adding additives to control its expansion, the expansion rate can be reduced. But it is more difficult to achieve oil needle coke.
6. Calcined oil needle coke has more small coke and fine particle size, while coal needle coke has less content and large particle size (35 — 40 mm), which can meet the requirements of formula particle size, but it brings difficulties to users.
7. According to the introduction of Japan Petroleum Coke Company, it is believed that the composition of oil needle coke is simpler than coal needle coke, so it is easy to control the coking and heating time.
From the above, oil needle coke has four low: low false specific gravity, low strength, low CTE, low specific resistance, the first two low to graphite products, the last two low to graphite products is favorable. Overall, the performance indexes of oil series needle coke are better than coal series needle coke, and the application demand is also more.
At present, graphite electrode is the main demand market for needle coke, accounting for about 60% of the total application of needle coke, while electrode enterprises have clear quality demand for needle coke, without personalized quality demand. The needle coke demand of lithium ion battery anode material is more diverse, high-end digital market favors oil cooked coke, power battery market is more dependent on coke with higher cost performance.
Needle coke production has a certain technical threshold, so domestic enterprises are relatively rare. At present, the domestic mainstream production enterprises of oil needle coke include: Weifang Fumei new Energy, Shandong Jingyang, Shandong Yida, Jinzhou Petrochemical, Shandong Lianhua, Bora Biological, Weifang Fumei new energy, Shandong Yiwei, Sinopec jinling Petrochemical, Maoming petrochemical, etc. Coal series needle coke mainstream production enterprises Baowu carbon material, Baotailong technology, Anshan open carbon, Anshan Chemical, Fang Daxi ke Mo, Shanxi Macro, Henan open carbon, Xuyang Group, Zaozhuang revitalization, Ningxia Baichuan, Tangshan Dongri new energy, Taiyuan Shengxu and so on.
Post time: Oct-19-2021