Spent Pot Lining Recycling via Packed Bed Leaching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current recycling methods for Spent Pot Linings (SPL) from aluminium production are costly, energy-intensive, and fail to comply with environmental regulations due to the need for expensive technological solutions and inefficient detoxification processes.
Innovation Solution
A recycling process that involves crushing SPL into granules of 0-4 mm, forming a packed bed column, and using hydrogen peroxide and sodium hydroxide solutions for decomposition and leaching, with multiple washing stages at controlled temperatures around 25°C, reducing water usage and eliminating hazardous substances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spent pot linings are completely crushed to fine granulation (0.6 mm) and processed through multiple high-temperature steps, then detoxification is achieved, but investment cost and energy consumption greatly increase
Solution Approach 1:
The invention changes the particle size parameter from fine granulation (0.6 mm) to coarse granulation (0-4 mm), and changes the temperature parameter from high temperature to ambient temperature (25°C ± 5°C). These parameter changes enable effective detoxification while dramatically reducing energy consumption and eliminating the need for expensive high-temperature equipment
Solution Approach 2:
The invention replaces expensive, complex high-temperature technological equipment with simple, inexpensive ambient temperature processing equipment. The process uses readily available chemicals (hydrogen peroxide and sodium hydroxide) instead of requiring specialized high-temperature processing facilities, thereby greatly reducing investment cost
2Loss of substance
If spent pot linings are processed through multiple washing stages at high temperatures, then water-soluble fluoride salts are removed, but water usage and energy consumption increase
Solution Approach 1:
The invention changes the temperature parameter from high temperature to ambient temperature (25°C ± 5°C) and optimizes the particle size to 0-4 mm coarse granulation. These changes improve water usage efficiency and enable effective fluoride salt removal without requiring excessive water or energy input
3Object-affected harmful factors
If expensive technological solutions are used for SPL recycling, then environmental compliance is achieved, but investment cost increases
Solution Approach 1:
The invention replaces expensive, complex technological equipment with simple, inexpensive ambient temperature processing equipment. The process achieves environmental compliance using readily available chemicals (hydrogen peroxide and sodium hydroxide) and simple washing equipment, thereby greatly reducing investment cost while meeting environmental regulations
Solution Approach 2:
The invention enables the recycling process to be self-sufficient and simple to operate. The packed bed column design allows for automatic percolation of washing solutions, and the process uses common chemicals that do not require specialized handling equipment, making the system easy to operate and maintain
4Object-affected harmful factors
If spent pot linings are ground to fine granulation (0.6 mm), then detoxification is effective, but the process becomes more complex and expensive
Solution Approach 1:
The invention changes the particle size parameter from fine granulation (0.6 mm) to coarse granulation (0-4 mm). This parameter change simplifies the crushing process, reduces equipment requirements, and lowers operational complexity while maintaining effective cyanide decomposition and detoxification through the chemical treatment process
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 process effectively detoxifies SPL, achieving non-toxic materials that can be reused in industries like stone wool and metallurgy, while being simpler, more cost-effective, and environmentally sound, with higher purity levels compared to existing methods.
Implementation Method 1
concurrently inside the washing cycle cyanides are decomposed by oxidation with addition of the hydrogen peroxide (H2O2)
Implementation Method 2
The crushed spent pot lining material is leached in a packed bed column with a sodium hydroxide (NaOH) solution
Data Source
Figure 1
AI summary
The invention relates to a process for the preparation of spent pot lining material for use in recycling, wherein the spent pot lining material is coarsely ground and poured into a reactor to form packed bed column so that the granulation of the spent pot lining is in the range from 0 to 4 mm, and that the main fraction is in the range up to 3 mm, further the aforementioned filled layers of the ground spent pot lining are first washed with water and then a leaching is performed with a solution of sodium hydroxide - NaOH that has a concentration range from 0.05 to 0.48 mol/L and finally the spent pot lining material is once again washed with clean water until the measured electrical conductivity of the water reaches its entry level e.g. 0.5 mS/m. In all the above cases, a liquid to solid (L/S) ratio of 2.9:1 is used; washing and leaching procedures are repeated 2 to 7 times. In both the above steps, washing with water and leaching, hydrogen peroxide is added concurrently in twice the amount of the necessary stoichiometric quantity to decompose the cyanides present.