Advantages
Advantages for Handling Powders and Bulk Solids via Fluidization
The advantages for handling powders and bulk solids via fluidization instead of traditional deaerated gravity flow include:
- Elimination or reduction of arching (bridging) or ratholing problems
- Increased discharge rate from a silo or hopper
- Blending of solids and reduction in mixture segregation
- Increased gas-solids interaction for drying, agglomeration, or reactions
Typical bulk solids suitable for fluidization have a fine particle size, a low permeability, a tight particle size distribution, and low cohesive strength. The Geldart powder fluidization chart is a common reference used to assess if a bulk solid is a good candidate for fluidization (Geldart zones A and B). Many solids can be fluidized, though powders prone to segregate or cake are often not good candidates.
Approach
Powder Fluidization Tests
To evaluate powder fluidization suitability, we can perform the following tests:
- Minimum fluidization velocity: run with 8 in. (200 mm) dia. test column
- Fluidization discharge assessment: run with 22 in. (560 mm) dia. column
- Air-assisted discharge: localized powder aeration vs. full fluidization
These tests can be run with various gases (e.g., nitrogen, carbon dioxide) and over a range of temperatures. During these tests, observations are made to note settlement behavior, channeling of the solids, formation of a solid plug, and bed expansion. View a video of powder fluidization tests performed in our laboratory.
Results
Powder Fluidization Test Results
The fluidization test results are presented in a comprehensive report package containing:
- Description of fluidization procedure, test apparatus, fluidization media
- Graph of powder bed pressure-drop as function of superficial gas velocity
- Observations of test phenomena such as plug rise, bed spouting, or cracking
- Video of fluidization behavior in test column
- Test conclusions and recommendation for fluidization velocity for powder
After completion of the tests, we will review the results with you and answer any questions. We will also discuss how the test results may be used for your fluidization application.
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