The bottlenecks in the production of needle coke in our country

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1 Analysis of the main bottlenecks faced by domestic needle coke manufacturers. Although industrial production of needle coke is already feasible in China, the process technology still needs further improvement. The main technical challenges include the following: 1.1 Raw material pretreatment. The purification of coal-based needle coke raw materials presents difficulties related to methods for removing QI from coal tar, the yield of refined tar, and the stability of the properties of the refined tar； Furthermore, at present, the pretreatment of coal-based needle coke raw materials both domestically and internationally relies on solvent methods to remove QI. During the production process, materials rich in QI have poor fluidity, which poses significant difficulties; moreover, it is also challenging to determine how to utilize this component as a by-product in the end. The challenges in selecting and purifying oil-based needle coke feedstocks lie in the removal of impurities (such as catalysts), the high aromatic content, and the low sulfur content. To diversify the sources of raw materials, China has begun researching the pretreatment of raw materials for oil-based needle coke in recent years; further work is needed to remove S, resins, and asphaltenes from heavy petroleum fractions. 1.2 Delayed coking: Problems existing in the delayed coking process: (1) Determination of operating conditions: Determining the process parameters such as temperature, pressure, and gas flow for pulling coke during the coking process. (2) The optimization of process parameters is a key issue in delayed coking. There is a certain relationship between these process parameters and the properties of the feedstock (refined pitch). Under the condition of maintaining stable feedstock quality, how to optimize the process parameters for delayed coking is the main challenge that needs to be addressed in order to produce high-quality needle coke. (3) Uniformity issue of the quality of needle coke in each tower: During the feeding process in each coking tower, factors such as temperature, pressure, and gas velocity in the empty tower change, which results in non-uniform quality of the coke at the upper, middle, and lower sections of the tower after coking occurs. How to effectively address the issue of uniformity in the quality of needle coke is also one of the considerations in needle coke production. 1.3 Calcination (1) Calcination temperature: All imported needle coke is calcined coke; carbon enterprises in China only calcine petroleum coke (raw coke), with the calcination temperature ranging from 1250°C to 1350°C (using rotary kilns). The calcination temperature for needle coke needs to be above 1500°C, which is 150°C higher than that of petroleum coke; whether the refractory materials in the rotary kiln can withstand such high temperatures is an issue that must be taken into consideration during the calcination process. (2) Uniformity issue of the green coke quality: The volatiles, moisture, and particle size distribution of the green coke (the raw material for calcination) affect the uniformity of the quality of the final needle coke. In addition to optimizing delayed coking operations, these issues require treating the raw coke before calcination (such as dehydration and homogenization).