Aluminum Hydroxide Crystal Growth Modifiers for Oxalate Interference
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Solution Overview
Problem
The aluminum hydroxide production process, particularly in the Bayer process, faces challenges in achieving increased particle size and yield due to the presence of oxalate anions, which lead to decreased average particle size and yield, and require effective removal methods to prevent agglomeration and shutdowns.
Innovation Solution
The introduction of oligomeric or polymeric compounds with carboxylic groups, produced through ene or Diels-Alder synthesis, as crystal growth modifiers, which are blended and in-line injected into the process to enhance particle size and yield while facilitating oxalate removal, are used.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If oxalate removal methods (washing or side-stream destruction) are implemented, then oxalate interference is reduced, but processing complexity and potential aluminum loss increase
Solution Approach 1:
The patent applies preliminary action by adding crystal growth modifiers to the seed charge before the precipitation process begins. This pre-treatment of seeds modifies their surface properties in advance, preventing oxalate co-precipitation during the main process without requiring separate removal steps, thereby reducing processing complexity while still eliminating oxalate interference
2Manufacturing precision
If crystal growth modifiers are used to increase aluminum hydroxide particle size, then particle size and yield improve, but oxalate may co-precipitate and reduce effectiveness
Solution Approach 1:
The patent applies local quality by treating the seed crystals with crystal growth modifiers to give them specialized surface properties that are selective - they promote aluminum hydroxide growth while rejecting oxalate. This localized modification of seed surface chemistry allows the system to achieve size control without oxalate interference, as the modified seeds create a local environment that favors selective crystal growth
3Object-affected harmful factors
If seed washing is performed to remove oxalate, then oxalate is reduced, but processing time and potential aluminum loss increase
Solution Approach 1:
The patent eliminates the need for seed washing by applying preliminary action - treating seeds with crystal growth modifiers before use. This pre-treatment creates oxalate-resistant seed surfaces that prevent co-precipitation during the main process, achieving oxalate removal without the time-consuming washing step and associated aluminum losses
Solution Approach 2:
The patent takes out the harmful oxalate interference mechanism by modifying seed surfaces with crystal growth modifiers, which selectively prevent oxalate attachment while allowing aluminum hydroxide growth. This extraction of oxalate's harmful effect is achieved through surface chemistry modification rather than physical removal, saving processing time
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
These compounds effectively increase the particle size and yield of aluminum hydroxide crystals without decreasing overall product yield, improving the separation and collection of alumina trihydrate, and stabilizing oxalate concentrations, thus addressing the limitations of existing methods.
Implementation Method 1
The introduction of oligomeric or polymeric compounds with carboxylic groups, produced through ene or Diels-Alder synthesis, as crystal growth modifiers, which are blended and in-line injected into the process to enhance particle size and yield
Implementation Method 2
stabilizing oxalate concentrations, thus addressing the limitations of existing methods
Data Source
AI summary
The present invention relates ways to increase the output of a high quality product from the aluminum hydroxide recovery processes such as the Bayer process. The invention is a method of increasing the size of precipitated aluminum hydroxide while not reducing the total production amounts. The invention relates to the use of a crystal growth modifier compositions added to the precipitation liquor to increase the particle size distribution of the precipitated alumina trihydrate.