Aluminium Hydroxide Precipitation via Cross-Seeding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing Bayer process for aluminum production generates bauxite residue that is environmentally hazardous and economically challenging, while the Pedersen process is economically unsustainable due to high energy requirements, and both processes face challenges in producing high-quality aluminum hydroxide suitable for industrial use.
Innovation Solution
A method that combines the Bayer and Pedersen processes by seeding aluminum hydroxide precipitates between two tanks containing supersaturated sodium aluminate solutions, allowing for high-quality aluminum hydroxide production with minimal adjustments to existing Bayer process equipment, thereby increasing yield and reducing environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the Bayer process is used to extract aluminum from bauxite, then aluminum production is achieved, but large amounts of hazardous bauxite residue (red mud) are generated requiring expensive storage facilities
Solution Approach 1:
The patent converts the harmful bauxite residue (red mud) into a valuable resource by using it as raw material in the Pedersen process to produce aluminum hydroxide and pig iron. The residue is mixed with limestone and coke, then processed in a submerged arc furnace to extract aluminum and generate useful by-products, thereby eliminating the need for expensive storage facilities and converting waste into economic value
Solution Approach 2:
The patent merges the Bayer process and Pedersen process into a single integrated facility. The Bayer process produces sodium aluminate solution and bauxite residue, while the Pedersen process uses the residue along with limestone and coke to produce aluminum hydroxide and pig iron. This combination allows both processes to operate synergistically within one plant, maximizing resource utilization and minimizing waste
2Object-generated harmful factors
If the Pedersen process is used to produce aluminum from rocks, then environmentally friendly production with valuable side products is achieved, but high electric energy consumption makes it economically unsustainable
Solution Approach 1:
The patent converts the high energy consumption of the Pedersen process into an economic advantage by producing valuable pig iron as a by-product. The pig iron generated from processing bauxite residue with limestone and coke in the submerged arc furnace provides additional revenue streams that offset the high electricity costs, making the process economically viable while maintaining environmental benefits
Solution Approach 2:
The patent makes the Pedersen process multi-functional by simultaneously producing aluminum hydroxide for industrial use and pig iron as a valuable by-product. The single process serves multiple purposes: extracting aluminum from residue, generating pig iron for steel production, and producing calcium carbonate-rich slag for construction materials, thereby diversifying income sources to compensate for high energy costs
3Productivity
If aluminum hydroxide is produced by carbon dioxide precipitation in the Pedersen process, then aluminum extraction is achieved, but the precipitate lacks the properties required for industrial usage
Solution Approach 1:
The patent applies preliminary action by adding seed crystals of aluminum hydroxide to the supersaturated sodium aluminate solution before carbon dioxide precipitation. These seed crystals provide nucleation sites that guide the formation of aluminum hydroxide precipitate, ensuring it develops the correct crystalline structure and physical properties required for industrial use, thereby resolving the quality issue while maintaining high extraction rates
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 achieves significantly higher alumina extraction rates, produces high-quality aluminum hydroxide and oxide, and generates valuable side products like pig iron, while minimizing environmental harm and economic investments, by synergizing both processes in a single facility.
Implementation Method 1
carbon dioxide (CO2) gas is added to the first tank to form a first aluminium hydroxide precipitate
Implementation Method 2
carbon dioxide (CO2) gas is added to the first tank to form a first aluminium hydroxide precipitate
Implementation Method 3
seed crystals are added to the second tank to form a second aluminium hydroxide precipitate
Implementation Method 4
seed crystals are added to the second tank to form a second aluminium hydroxide precipitate
Implementation Method 5
at least a fraction of the first aluminium hydroxide precipitate obtained from the first solution in the first tank is seeded into the second tank and/or at least a fraction of the second aluminium hydroxide precipitate obtained from the second solution in the second tank is seeded into the first tank
Data Source
AI summary
A method for the production of aluminium hydroxide (Al(OH)3) is described wherein in a first tank a first aqueous solution of sodium aluminate (NaAl(OH)4) is provided and carbon dioxide (CO2) gas is added to the first tank to form a first aluminium hydroxide precipitate, and wherein a second tank containing a second aqueous solution of sodium aluminate is provided, wherein the sodium aluminate solution in the second tank is supersaturated and seed crystals are added to the second tank to form a second aluminium hydroxide precipitate. At least a fraction of the first aluminium hydroxide precipitate obtained from the first solution in the first tank is seeded into the second tank and/or at least a fraction of the second aluminium hydroxide precipitate obtained from the second solution in the second tank is seeded into the first tank.