The causes of excessive consumption can be divided into two categories: carbon anode slag falling and carbon anode surface oxidation.
1. Carbon anode slag dropping is produced in many forms:
(1) In the process of carbon anode manufacturing, the surface of coke particles is not fully wrapped and soaked by liquid asphalt during kneading, so the particles cannot be fully closely bonded during vibration molding, and a perfect asphalt carbon network structure for fixing coke particles cannot be formed after roasting. In the process of aluminum electrolysis, coke particles fall off and fall into the electrolyte to form carbon slag.
(2) The excitation force is insufficient, or the amplitude, frequency, vibration time and other parameters do not match, the anode vibration is not real, the anode porosity is high after roasting, the specific gravity is small, the coke particles are not closely bonded, and slag falls during electrolysis.
(3) Over burning of petroleum coke during calcination reduces the reaction activity of coke particle carbon, while the coke particles are bonded by asphalt in anode production. The activity of the fixed carbon left after asphalt calcination is higher than that of coke particles. Therefore, in the electrolysis process, the network asphalt carbon of this anode reacts faster, the coke particle carbon with low activity reacts slower, and the consumption speed is inconsistent, resulting in slag falling.
(4) The formula of anode particles is unreasonable, and the porosity is high. When used in electrolysis, the oxygen generated in electrolysis will enter the hole for reaction, and the formation reaction is not carried out on the same bottom surface, resulting in slag falling.
(5) When the anode current density is low, the selective carbon reaction occurs, that is, the oxygen atoms first choose to react on the surface of the network asphalt carbon with strong activity, and the coke with low activity will not react. After the network asphalt carbon is consumed, the coke particles will fall into the electrolyte to form carbon slag.
(6) When the carbon dioxide gas generated at the bottom of the anode flows to the edge during the electrolysis process, the huge pressure and flow rate formed impact the bottom surface of the anode and accelerate the slag falling of the anode.
2. Carbon anode surface oxidation is that when the anode is not fully covered by alumina and exposed, or the covering material is not tight, and there is air leakage, it will oxidize with oxygen in the air to generate carbon dioxide gas, which will be discharged along the outer surface of the anode. When the anode is in the state of high temperature red heat, CO2 gas will react with red hot carbon to generate CO gas, resulting in excessive consumption of carbon anode.
Solutions of excessive consumption of carbon anode
(1) Attach great importance to carbon anode consumption and energy conservation and emission reduction in electrolytic aluminum production.
(2) Improve the anode manufacturing technology and comprehensively improve the quality of anode products. From improving the activity of petroleum coke after calcination to improving the formula, kneading, molding, roasting and so on.
(3) Strengthen the technological management of electrolytic cell, reasonably match various technical parameters of electrolytic cell, ensure the operation of electrolytic cell in good condition, especially control the occurrence of sick cell, and prevent the thermal cracking, damage, falling off and slag dropping of carbon anode in the process of aluminum electrolysis. Seal and cover the upper part of the anode to reduce air oxidation, and control the working temperature of the electrolytic cell, especially the upper part of the anode, so as to reduce the oxidation consumption of Buda reaction.
(4) Vigorously study the new structure carbon anode, change the discharge behavior of anode gas in electrolytic aluminum production, reduce the scouring of anode gas on anode bottom palm and reduce anode slag falling.
