Bulk Material Testing - Powder Fluidization

Overview

Why Powder Fluidization Testing?

Fluidization can be a highly effective method for handling a fine bulk material in an aerated or liquid-like condition.

Air or another gas can be used for powder fluidization either in a fully fluidized state or only in a localized manner with small amounts of gas flow.
Fluidization is commonly used with pulverized fuel handling, drying operations, reaction processes, and fine powder hopper discharge systems.

Jenike & Johanson fluidization column apparatus.

Fluidized discharge test.

Fluidized powder in drum.

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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