Reductive Melting of Li-Ion Battery Scrap With a Protective Slag Layer
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Solution Overview
Problem
The existing methods for recovering valuable metals from discarded lithium ion batteries, such as those described in Patent Document 1, face issues with excessive lowering of the liquidus temperature due to flux addition, leading to refractory material erosion and safety concerns, as well as high maintenance costs, which hinder efficient and safe recovery of valuable metals.
Innovation Solution
A method involving a melting furnace with external cooling to form a solidified slag layer on the furnace wall with a Ca/Al value smaller than the slag, containing 15 mass% or more of Al and 3 mass% or more of Li, during reductive melting treatment, using a flux containing calcium to separate and recover alloys of copper, nickel, and cobalt, while maintaining a slag heating temperature between 1,400°C and 1,600°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a flux is added to lower the liquidus temperature of the slag, then the valuable metal can be recovered more efficiently, but the refractory material of the furnace wall is eroded and safety is compromised
Solution Approach 1:
The patent segments the furnace wall structure by introducing a cooling means (water-cooled copper plates) between the refractory material and the molten slag, creating a temperature gradient that protects the refractory material from direct contact with high-temperature molten slag while allowing the slag to maintain its required temperature for metal recovery
Solution Approach 2:
The cooling means acts as an intermediary between the molten slag and the refractory material, absorbing excess heat from the slag through water circulation and preventing direct thermal contact that would cause erosion, thereby enabling the use of fluxes to lower liquidus temperature without compromising furnace safety
2Productivity
If the liquidus temperature of the slag is excessively lowered, then the valuable metal recovery is improved, but the refractory material erosion increases and maintenance cost becomes enormous
Solution Approach 1:
The furnace wall is segmented into a refractory material layer and a water-cooled copper plate layer, allowing the slag to be maintained at a lower temperature range that is still effective for metal recovery but safe for the refractory material, thereby reducing maintenance costs while preserving productivity
Solution Approach 2:
The patent changes the temperature parameter of the slag by introducing active cooling, enabling the slag to be maintained at an optimized temperature range (1400-1600°C) that balances recovery efficiency with refractory material protection, reducing the need for expensive maintenance
3Reliability
If cooling means is introduced to protect the furnace wall, then refractory material erosion is suppressed, but the device complexity increases
Solution Approach 1:
The patent uses hydraulic cooling (water circulation through copper plates) to protect the furnace wall, leveraging fluid dynamics to remove heat efficiently from the refractory material without requiring complex mechanical moving parts or active control systems
Solution Approach 2:
The furnace wall employs a composite structure combining refractory material (for thermal insulation and protection) with water-cooled copper plates (for active heat removal), creating a multi-layer composite system that provides robust protection while maintaining relatively simple construction
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 allows for safe and efficient recovery of valuable metals by suppressing refractory material erosion and enhancing the recovery ratio, ensuring a high melting point for the solidified slag layer and maintaining a stable temperature for effective metal separation.
Implementation Method 1
a reductive melting step of subjecting the raw material to a reductive melting treatment using a melting furnace provided with a cooling means for cooling a furnace wall from outside
Implementation Method 2
forming a solidified slag layer on a surface of the furnace wall while using this means for cooling the furnace wall from outside
Implementation Method 3
a reductive melting step of subjecting the raw material to a reductive melting treatment
Implementation Method 4
a flux containing calcium (Ca) is added to the raw material
Data Source
Figure 1
Figure 2
AI summary
Provided is a method by which it is possible to safely and efficiently collect valuable metals from raw material including waste lithium-ion batteries or the like. The present invention is a method for producing valuable metals from raw material containing valuable metals including Cu, Ni and Co. The method includes at least: a preparation step for preparing raw material containing Li, Al, and valuable metals; a reduction melting step for subjecting the raw material to reduction melting treatment using a melting furnace provided with a cooling means for cooling the furnace walls from the outside to obtain a reduced product comprising a valuable metals-containing alloy and slag; and a slag separation step for separating the slag from the reduced product to collect the alloy. One or both of the preparation step and the reduction melting step include adding Ca-containing flux to the raw material. In the reduction melting step, while the furnace walls of the melting furnace are cooled with the cooling means, a solid slag layer having a Ca/Al value smaller than the Ca/Al value of the slag or a solid slag layer containing 15 mass% or more Al and 3 mass% or more Li is formed on the inside surface of the melting furnace.