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 flow 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 materials, carbon fiber and its composite materials.
According to the different production materials, the needle coke can be divided into oil series and coal series two kinds of needle coke. The needle coke produced with petroleum residue as raw material is oil series needle coke. The coal measure needle coke produced from coal tar pitch and its fraction is called coal measure needle coke.
The indexes that affect the quality of needle coke include true density, sulfur content, nitrogen content, volatile content, ash content, thermal expansion coefficient, electrical resistivity, vibration-solid density, etc. Due to the different specific index coefficients, needle coke can be divided into super grade (superior grade), first grade and second grade.
The performance difference between coal measure needle coke and oil measure needle coke includes the following points.
1. Under the same conditions, the graphite electrode made of oil series needle coke is easier to be formed than coal series needle coke in terms of performance.
2. After graphite products are made, the graphitized products of oil series needle coke have a slightly higher density and strength 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 products with oil needle coke have a lower coefficient of thermal expansion.
4. In terms of physical and chemical indexes of graphite electrode, the specific resistance of graphitized products of oil series needle coke is slightly higher than that of coal series needle coke products.
5. The most important thing is that coal measure needle coke expands in the process of high temperature graphitization, when the temperature reaches 1500-2000 ℃, so the temperature rise speed should be strictly controlled, not fast heating up, it is best not to use series graphitization process production, coal measure needle coke by adding additives to control its expansion, expansion rate can be reduced. But it is more difficult to achieve the oil – based needle coke.
6. The calcined oil system has more small coke content and finer grain size, while the coal measure needle has less coke content and larger grain size (35-40 mm), which can meet the grain size requirement of the formula, but brings difficulty to the user’s crushing.
7. According to Japan Petroleum Coke Company, it is considered that the composition of oil series needle coke is simpler than that of coal series needle coke, so it is easy to control during the coking process.
From the above point of view, the oil system needle coke has four low: low specific gravity, low strength, low CTE, low specific resistance, the first two low on graphite products, the last two low on graphite products is favorable. Generally speaking, the performance indexes of oil series needle coke are better than those of coal series needle coke, and the application demand is more.
At present, graphite electrode is the main demand market of needle coke, accounting for about 60% of the total application of needle coke, and electrode enterprises have clear demand for needle coke quality, without personalized quality demand. Lithium ion battery anode materials have more diverse demand for needle coke, high-end digital market prefers oil cooked coke, power battery market is more dependent on more cost-effective raw coke.
The production of needle coke has a certain technical threshold, so there are few domestic enterprises. At present, the mainstream domestic oil series needle coke manufacturers include Shandong Jingyang, Shandong Yida, Jinzhou Petrochemical, Shandong Lianhua, Bora Biological, Weifang Fumei New Energy, Shandong Yiwei, Sinopec Jinling Petrochemical, Maoming Petrochemical, etc. The main producers of coal measure needle coke are Baowu Carbon Material, Baotailong Technology, Anshan Kaitan, Angang Chemical, Fang Daxi Kemo, Shanxi Hongte, Henan Kaitan, Xuyang Group, Zaozhuang Zhenxing, Ningxia Baichuan, Tangshan Dongri New Energy, Taiyuan Shengxu, etc.
Post time: Dec-02-2022