Artificial Graphite Electrode Kneading Index Optimization
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Solution Overview
Problem
Producing artificial graphite electrodes with large pore volume needle coke poses challenges in maintaining constant extrusion molding rates and pressures, often resulting in electrode cracking due to excessive binder pitch usage and volatile component formation.
Innovation Solution
A method involving two separate kneading stages with a kneading index within the range of 0.1 to 0.7, where the amount and time of binder pitch addition in each stage optimize kneading and extrusion molding without increasing the total binder pitch, allowing for lower molding pressures and energy savings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mechanical mixing is used to mix the green paste, then mixing is achieved, but the mixing time is long (over 48 hours) and the paste becomes coarse
Solution Approach 1:
The patent replaces mechanical mixing with ultrasonic wave irradiation. The ultrasonic waves cause cavitation and vibration in the slurry, achieving thorough mixing and particle dispersion without mechanical contact. This substitution reduces mixing time from over 48 hours to just a few minutes while producing fine, uniform paste without coarse particles.
2Duration of action of stationary object
If conventional drying methods are used, then drying is achieved, but the drying time is long (over 20 days) and the green strength is low
Solution Approach 1:
The patent employs periodic high-frequency vibration during the drying process. The vibration is applied intermittently to remove water from the green body while maintaining structural integrity. This periodic mechanical action accelerates water removal significantly, reducing drying time from over 20 days to a few hours, while simultaneously improving green strength through vibration-induced densification.
3Strength
If organic binding agents are used to improve green strength, then green strength increases, but harmful substances remain after carbonization
Solution Approach 1:
The patent changes the chemical composition parameters of the binding agent by using inorganic substances (such as metal oxides or salts) instead of organic binders. These inorganic binding agents provide adequate green strength through chemical bonding and physical interlocking, while being fully compatible with the carbonization process. They do not produce harmful organic emissions during carbonization, thus eliminating the harmful substance problem while maintaining necessary strength.
4Loss of time
If the green body is not pre-dried before carbonization, then processing time is reduced, but the green strength is insufficient for handling
Solution Approach 1:
The patent implements continuous drying and vibration treatment directly on the green body without interruption or intermediate storage. The ultrasonic vibration and mechanical vibration are applied continuously during the brief drying period, maintaining constant densification and strength development. This continuous action achieves sufficient green strength in just a few hours, eliminating the need for long pre-drying periods and enabling immediate carbonization.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables stable extrusion molding and maintains electrode quality and productivity, with improved thermal expansion and puffing performance, even with high-pore volume needle coke, while reducing energy consumption.
Implementation Method 1
the mixed slurry is subjected to ultrasonic waves for a predetermined period to mix the slurry
Implementation Method 2
the green body is dried to obtain a spheroid artificial graphite electrode precursor
Data Source
Figure 1~2
Figure 3
AI summary
The present invention provides a method for producing an artificial graphite electrode that enables kneading and subsequent mixing to be carried out without having to increase an amount of binder pitch used even in the case of needle coke having a large pore volume. An artificial graphite electrode is produced by kneading binder pitch with needle coke, and performing extrusion molding and then performing baking and graphitization treatment on the same, wherein a process for kneading the binder pitch with needle coke includes at least two separate kneading stages, and the amount of binder pitch added and kneading time in these kneading stages satisfy a kneading index as represented by formula (1) below within a range of 0.1 to 0.7. Kneading index=a1/A×t1/T