With the rapid development of electrolytic aluminum industry, aluminum prebaking anode industry has become a new investment hotspot, the production of prebaking anode is increasing, petroleum coke is the main raw material of prebaking anode, and its indexes will have a certain impact on the quality of products.
Sulfur content
The sulfur content in petroleum coke mainly depends on the quality of crude oil. Generally speaking, when the sulfur content of petroleum coke is relatively low, the anode consumption decreases with the increase of sulfur content, because sulfur increases the coking rate of asphalt and reduces the porosity of asphalt coking. At the same time, sulfur is also combined with metal impurities, reducing the Catalysis by metal impurities to suppress carbon dioxide reactivity and air reactivity of carbon anodes. However, if the sulfur content is too high, it will increase the thermal brittleness of the carbon anode, and because the sulfur is mainly converted into the gas phase in the form of oxides during the electrolysis process, it will seriously affect the electrolysis environment, and the environmental protection pressure will be great. In addition, sulfuration may be formed on the anode rod Iron film, increasing the voltage drop. As my country’s crude oil imports continue to increase and processing methods continue to improve, the trend of inferior petroleum coke is inevitable. In order to adapt to changes in raw materials, prebaked anode manufacturers and the electrolytic aluminum industry have carried out a large number of technological transformations and technological breakthroughs. From China’s domestic prebaked anode According to the investigation of production enterprises, petroleum coke with a sulfur content of about 3% can generally be directly calcined.
Trace elements
Trace elements in petroleum coke mainly include Fe, Ca, V, Na, Si, Ni, P, Al, Pb, etc. Due to the different oil sources of petroleum refineries, the composition and content of trace elements are very different. Some trace elements are brought in from crude oil, such as S, V, etc. Some alkali metals and alkaline earth metals will also be brought in, and some ash content will be added during transportation and storage, such as Si, Fe, Ca, etc. The content of trace elements in petroleum coke directly affects the service life of prebaked anodes and the quality and grade of electrolytic aluminum products. Ca, V, Na, Ni and other elements have a strong catalytic effect on the anodic oxidation reaction, which promotes the selective oxidation of the anode, causing the anode to drop slag and blocks, and increase the excessive consumption of the anode; Si and Fe mainly affect the quality of primary aluminum, and the Si content increases It will increase the hardness of aluminum, reduce the electrical conductivity, and the increase of Fe content has a great influence on the plasticity and corrosion resistance of aluminum alloy. Combined with the actual production requirements of enterprises, the content of trace elements such as Fe, Ca, V, Na, Si, and Ni in petroleum coke should be limited.
Volatile matter
The high volatile content of petroleum coke indicates that the uncoked part is carried more. Excessively high volatile content will affect the true density of calcined coke and reduce the actual yield of calcined coke, but an appropriate amount of volatile content is conducive to the calcination of petroleum coke. After the petroleum coke is calcined at high temperature, the volatile content decreases. Since different users have different expectations for volatile content, combined with the actual needs of manufacturers and users, it is stipulated that the volatile content should not exceed 10%-12%.
Ash
The incombustible mineral impurities (trace elements) remaining after the combustible part of petroleum coke is completely burned under the condition of high temperature of 850 degrees and air circulation are called ash. The purpose of measuring ash is to identify the content of mineral impurities (trace elements) How much, in order to assess the quality of petroleum coke. Controlling the ash content will also control the trace elements. Excessive ash content will definitely affect the quality of the anode itself and the primary aluminum. Combined with the actual needs of users and the actual production situation of enterprises, it is stipulated that the ash content should not exceed 0.3%-0.5%.
Moisture
The main sources of water content in petroleum coke: First, when the coke tower is discharged, the petroleum coke is discharged to the coke pool under the action of hydraulic cutting; second, from the perspective of safety, after the coke is discharged, the petroleum coke that has not been completely cooled needs to be sprayed to cool down Third, petroleum coke is basically stacked in the open air in coke pools and storage yards, and its moisture content will also be affected by the environment; fourth, petroleum coke has different structures and different ability to retain moisture.
Coke content
The particle size of petroleum coke has a great influence on the actual yield, energy consumption and calcined coke. Petroleum coke with high powder coke content has serious carbon loss during the calcination process. Shooting and other conditions can easily lead to problems such as early breakage of the furnace body, over-burning, blockage of the discharge valve, loose and easy pulverization of the calcined coke, and affect the life of the calciner. At the same time, the true density, tap density, porosity, and strength of the calcined coke , Resistivity and oxidation performance have great influence. Based on the specific situation of domestic petroleum coke production quality, the amount of powder coke (5mm) is controlled within 30%-50%.
Shot coke content
Shot coke, also known as spherical coke or shot coke, is relatively hard, dense and non-porous, and exists in the form of spherical molten masses. The surface of shot coke is smooth, and the internal structure is not consistent with the outside. Due to the lack of pores on the surface, when kneading with binder coal tar pitch, it is difficult for the binder to penetrate into the inside of the coke, resulting in loose bonding and prone to internal defects. In addition, the thermal expansion coefficient of the shot coke is high, which may easily cause thermal shock cracks when the anode is baked. The petroleum coke used in the pre-baked anode must not contain shot coke.
Catherine@qfcarbon.com +8618230208262
Post time: Dec-20-2022