High-Strength Shaped Alumina Beads with Single-Step Agglomeration
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Solution Overview
Problem
Existing methods for producing high strength shaped alumina, such as beads or spheres, require expensive forming and drying steps, large amounts of water, and high-temperature calcination, leading to high costs and equipment requirements, with additional seeding steps complicating the process.
Innovation Solution
A method involving a single forming step using a high shear agglomerator to produce shaped alumina beads, followed by a single calcination step, without the need for seeding, utilizing alumina powders with specific crystallite and particle sizes, and a liquid binder to achieve high strength and density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional forming and drying steps are used to produce shaped alumina beads, then the beads can be made with sufficient strength for handling, but the process becomes expensive and requires large amounts of water
Solution Approach 1:
The invention combines the forming and drying steps into a single spray drying operation. The alumina slurry is sprayed into a drying chamber where droplets are formed and dried simultaneously, eliminating the need for separate forming and drying equipment and reducing process complexity while maintaining bead strength
Solution Approach 2:
The invention changes the water content parameter of the alumina slurry to an optimized range (20-40% by weight) that allows direct spray drying without additional drying steps. This parameter adjustment enables the slurry to form stable droplets that dry completely during spray drying, producing strong beads with reduced process complexity
2Loss of time
If spray drying is incorporated into the process to reduce cost, then processing time is reduced, but bead size is limited by nozzle capability
Solution Approach 1:
The invention segments the bead formation process into multiple stages: first forming smaller droplets via spray drying, then agglomerating these droplets into larger beads through controlled collision and coalescence in the drying chamber. This segmentation allows spray drying to be used while achieving large final bead sizes that would be impossible with direct nozzle spraying alone
3Strength
If high temperature calcination is used to create strong, dense granules, then the alumina achieves high strength and high bulk density, but the cost of sintering increases
Solution Approach 1:
The invention performs preliminary densification during the spray drying step, where water is removed and particles are packed closely together before calcination. This preliminary action reduces the porosity and increases the density of the green beads, so that lower temperature and shorter duration calcination is needed to achieve the same final strength and density, reducing sintering energy cost
4Productivity
If water is removed at a high rate during drying, then processing efficiency increases, but the beads crack or fail
Solution Approach 1:
The invention uses periodic or staged drying conditions in the spray drying chamber, where droplets experience controlled evaporation rates at different stages. The outer shell of droplets dries first forming a protective skin, then internal water evaporates more slowly, preventing cracking. This periodic drying action maintains high overall drying efficiency while preserving bead integrity
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
The method produces high strength, high density alumina beads with reduced processing steps and costs, eliminating the need for seeding and allowing for adjustable properties like bulk density and porosity, suitable for various applications including oil field chemicals and synthetic sapphire production.
Implementation Method 1
a method involving a single forming step using a high shear agglomerator to produce shaped alumina beads
Implementation Method 2
followed by a single calcination step, without the need for seeding
Data Source
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AI summary
A method of producing high strength shaped alumina by feeding alumina power into an agglomerator having a shaft with mixers able to displace the alumina power along the shaft, spraying a liquid binder onto the alumina power as it is displaced along the shaft to form a shaped alumina, and calcining the shaped alumina. The shaped alumina produced having a loose bulk density of greater than or equal to 1.20 g/ml, a surface area less than 10 m2/g, impurities of less than 5 ppm of individual metals and less than 9 ppm of impurities in total, and/or crush strength of greater than 12,000 psi.