Cross-linked Polysaccharide Flocculation for Red Mud Separation
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Solution Overview
Problem
The Bayer Process faces inefficiencies in separating and washing insoluble red mud solids due to high cost associated with filtration and dilution steps, where the density of underflow in settlers and washers is limited, preventing effective recovery of alumina and caustic, and requiring additional energy and resources.
Innovation Solution
The use of cross-linked polysaccharides in combination with flocculants in the primary settling and washing stages to alter the rheology of red mud slurry, allowing for higher underflow densities and improved separation efficiency, thereby enhancing alumina and caustic recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional flocculants are used in primary settling, then red mud particles are bound and settling rate increases, but underflow density remains limited requiring additional filtration and dilution steps
Solution Approach 1:
The patent applies parameter changes by modifying the chemical properties of flocculants through cross-linking polysaccharides with agents like glutaraldehyde or epichlorohydrin. This chemical modification changes the molecular structure and functionality of the flocculant, enabling it to achieve higher underflow densities (up to 2.0-2.5 times conventional levels) and eliminate the need for additional filtration and dilution steps.
Solution Approach 2:
The patent employs composite materials by combining cross-linked polysaccharides with conventional flocculants to create a hybrid flocculation system. The cross-linked polysaccharide forms a three-dimensional network structure that enhances particle binding capability, while working synergistically with conventional flocculants to achieve superior separation performance and higher underflow densities.
2Reliability
If additional filtration and dilution steps are implemented, then alumina and caustic recovery is improved, but operational costs and energy consumption increase
Solution Approach 1:
The cross-linked flocculant system changes the separation efficiency parameter to achieve high-purity underflow in a single stage, eliminating the need for multiple filtration and dilution steps. This maintains reliable alumina and caustic recovery while significantly reducing energy consumption associated with additional processing steps.
Solution Approach 2:
The invention extracts the essential separation function into a single enhanced flocculation stage, removing the need for subsequent filtration and dilution steps. The cross-linked flocculant system performs the complete separation task in one operation, reducing both operational complexity and energy requirements.
3Ease of operation
If conventional flocculants are used, then separation is achieved, but underflow density is limited reducing throughput
Solution Approach 1:
The patent achieves both effective separation and high throughput by changing the flocculant parameters through cross-linking. The modified flocculants produce underflow densities up to 2.0-2.5 times higher than conventional systems while maintaining effective particle binding and separation, thereby increasing overall process throughput.
Solution Approach 2:
The cross-linked polysaccharide structure creates a dynamic three-dimensional network that adapts to bind particles effectively while allowing high solids concentration in the underflow. This dynamic structure maintains separation effectiveness at elevated densities, enabling increased throughput without compromising separation quality.
Data Source
AI summary
The invention provides methods and compositions for improving the rheology of red mud removed from Bayer Process liquor. The method includes adding a flocculant and a cross-linked polysaccharide to the liquor. This combination separates the red mud from the liquor but also prevents the red mud from becoming too thick. By preventing excessive thickness, the method allows for the formation of extremely dense amounts of red mud even in primary settlers because the dense red mud can still flow. As a result a user can simultaneously enjoy both easy handling of red mud and also high recovery rates of valuable alumina and caustic from the red mud.