Current situation and direction of negative graphitization technology

With the rapid development of new energy vehicles worldwide, the market demand for lithium battery anode materials has increased significantly. According to statistics, in 2021, the industry’s top eight lithium battery anode enterprises plan to expand their production capacity to nearly one million tons. Graphitization has the greatest impact on the index and cost of anode materials. The graphitization equipment in China has many kinds, high energy consumption, heavy pollution and low degree of automation, which limits the development of graphite anode materials to a certain extent. It is the main problem to be solved urgently in the production process of anode materials.

1. Current situation and comparison of negative graphitization furnace

1.1  Atchison negative graphitization furnace

In the modified furnace type based on the traditional electrode Aitcheson furnace graphitization furnace, the original furnace is loaded with graphite crucible as the carrier of negative electrode material (the crucible is loaded with carbonized negative electrode raw material), the furnace core is filled with heating resistance material, the outer layer is filled with insulation material and furnace wall insulation. After electrification, a high temperature of 2800 ~ 3000℃ is generated mainly by the heating of the resistor material, and the negative material in the crucible is heated indirectly to achieve the high temperature stone inking of the negative material

1.2. Internal heat series graphitization furnace

The furnace model is a reference to the serial graphitization furnace used for the production of graphite electrodes, and several electrode crucible (loaded with negative electrode material) are connected in series longitudinally. The electrode crucible is both a carrier and a heating body, and the current passes through the electrode crucible to generate high temperature and directly heat the internal negative electrode material. The GRAPHItization process does not use resistance material, simplifying the process operation of loading and baking, and reducing the heat storage loss of resistance material, saving power consumption

1.3 Grid box type graphitization furnace

No.1 application is increasing in recent years, the main is learned Series acheson graphitization furnace and concatenated technology characteristics of graphitizing furnace, furnace core of using multiple pieces of anode plate grid material box structure, material into the cathode in the raw material, through all slotted connection between anode plate column is fixed, each container, the use of anode plate seal with the same material. The column and the anode plate of the material box structure together constitute the heating body. The electricity flows through the electrode of the furnace head into the heating body of the furnace core, and the high temperature generated directly heats the anode material in the box to achieve the purpose of graphitization

1.4 Comparison of three graphitization furnace types

The internal heat series graphitization furnace is to directly heat the material by heating the hollow graphite electrode. The “Joule heat” produced by the current through the electrode crucible is mostly used to heat the material and crucible. The heating speed is fast, the temperature distribution is uniform, and the thermal efficiency is higher than the traditional Atchison furnace with resistance material heating. The grid-box graphitization furnace draws on the advantages of internal heat serial graphitization furnace, and adopts the pre-baked anode plate with lower cost as the heating body. Compared with the serial graphitization furnace, the loading capacity of the grid-box graphitization furnace is larger, and the power consumption per unit product is reduced accordingly


2. Development direction of negative graphitization furnace

2. 1 Optimize the perimeter wall structure

At present, the thermal insulation layer of several graphitization furnace is mainly filled with carbon black and petroleum coke. This part of the insulation material during the production of high temperature oxidation burn, each time the loading out of the need to replace or supplement a special insulation material, the replacement of the process of poor environment, high labor intensity.

Can consider a is to use special high strength and high temperature cement masonry wall stick adobe, enhance the overall strength, ensure the wall in the whole operation cycle stability in deformation, brick seam sealing at the same time, prevent excessive air Through the brick wall cracks and joint gap into the furnace, reduce the oxidation burning loss of insulating material and anode materials;

The second is to install the overall bulk mobile insulation layer hanging outside the furnace wall, such as the use of high-strength fiberboard or calcium silicate board, the heating stage plays an effective sealing and insulation role, the cold stage is convenient to remove for rapid cooling; Third, the ventilation channel is set in the bottom of the furnace and the furnace wall. The ventilation channel adopts the prefabricated lattice brick structure with the female mouth of the belt, while supporting the high-temperature cement masonry, and considering the forced ventilation cooling in the cold phase.

2. 2 Optimize the power supply curve by numerical simulation

At present, the power supply curve of the negative electrode graphitization furnace is made according to the experience, and the graphitization process is adjusted manually at any time according to the temperature and furnace condition, and there is no unified standard. Optimizing the heating curve can obviously reduce the power consumption index and ensure the safe operation of the furnace. The NUMERICAL MODEL OF needle alignment SHOULD be ESTABLISHED by scientific means according to various boundary conditions and physical parameters, and the relationship between the current, voltage, total power and the temperature distribution of the cross section in the grapHItization process should be analyzed, so as to formulate the appropriate heating curve and continuously adjust it in the actual operation. Such as in the early stage of power transmission is the use of high power transmission, then quickly reduce the power and then slowly rise, power and then reduce the power until the end of the power

2. 3 Extend the service life of crucible and heating body

In addition to power consumption, the life of crucible and heater also directly determines the cost of negative graphitization. For graphite crucible and graphite heating body, the production management system of loading out, reasonable control of heating and cooling rate, automatic crucible production line, strengthen sealing to prevent oxidation and other measures to increase the crucible recycling times, effectively reduce the cost of graphite inking. In addition to the above measures, the heating plate of grid box graphitization furnace can also be used as the heating material of pre-baked anode, electrode or fixed carbonaceous material with high resistivity to save the graphitization cost.

2.4 Flue gas control and waste heat utilization

The flue gas generated during graphitization mainly comes from volatiles and combustion products of anode materials, surface carbon burning, air leakage and so on. At the beginning of furnace start-up, volatiles and dust escape a large number, the workshop environment is poor, most enterprises do not have effective treatment measures, this is the biggest problem affecting the occupational health and safety of operators in negative electrode production. More efforts should be made to comprehensively consider the effective collection and management of flue gas and dust in workshop, and reasonable ventilation measures should be taken to reduce workshop temperature and improve the working environment of graphitization workshop.


After the flue gas can be collected through the flue into the combustion chamber mixed combustion, remove most of the tar and dust in the flue gas, it is expected that the temperature of the flue gas in the combustion chamber is above 800℃, and the waste heat of the flue gas can be recovered through the waste heat steam boiler or shell heat exchanger. The RTO incineration technology used in carbon asphalt smoke treatment can also be used for reference, and the asphalt flue gas is heated to 850 ~ 900℃. Through heat storage combustion, the asphalt and volatile components and other polycyclic aromatic hydrocarbons in the flue gas are oxidized and finally decomposed into CO2 and H2O, and the effective purification efficiency can reach over 99%. The system has stable operation and high operation rate.

2. 5 Vertical continuous negative graphitization furnace

The above mentioned several kinds of graphitization furnace is the main furnace structure of anode material production in China, the common point is periodic intermittent production, low thermal efficiency, loading out mainly rely on manual operation, the degree of automation is not high. A similar vertical continuous negative graphitization furnace can be developed by referring to the model of petroleum coke calcination furnace and bauxite calcination shaft furnace. The resistance ARC IS used as the high temperature heat source, the material is continuously discharged by its own gravity, and the conventional water cooling or gasification cooling structure is used to cool the high temperature material in the outlet area, and the powder pneumatic conveying system is used to discharge and feed the material outside the furnace. The FURNACE type can realize continuous production, the heat storage loss of furnace body can be ignored, so the thermal efficiency is significantly improved, the output and energy consumption advantages are obvious, and the full automatic operation can be fully realized. The main problems to be solved are the fluidity of powder, the uniformity of graphitization degree, safety, temperature monitoring and cooling, etc. It is believed that with the successful development of the furnace to scale industrial production, it will set off a revolution in the field of negative electrode graphitization.


3 the knot language

Graphite chemical process is the biggest problem plaguing lithium battery anode material manufacturers. The fundamental reason is that there are still some problems in power consumption, cost, environmental protection, automation degree, safety and other aspects of the widely used periodic graphitization furnace. The future trend of the industry is toward the development of fully automated and organized emission continuous production furnace structure, and supporting mature and reliable auxiliary process facilities. At that time, the graphitization problems that plague enterprises will be significantly improved, and the industry will enter a period of stable development, boosting the rapid development of new energy-related industries


Post time: Aug-19-2022