Storage and Flow of Solids

Grinding sludge oil recovery transportation system development.

For simple applications it may be sufficient to let the bulk solid flow out freely from a silo or hopper. The mass flow rate to be achieved is of particular interest here, which in the case of fine-grained bulk solids depends on the behavior of the gas in the voids between the particles. Often a controlled discharge of the bulk solid is necessary, for which purpose discharge devices (feeders) are used. Discharge devices are either conveyors that have been modified to meet the requirements as discharge devices, or special devices that not only discharge the bulk solid but also stimulate it to flow within the silo. With discharge devices, it is particularly important to ensure that they remove the bulk solid over the entire discharge opening and that no stagnant zones are created. Discharge aids are used to stimulate the flow of bulk solid in the silo (e.g., when stable arches or ratholes are formed) or to improve it. The mode of operation and use of the common principles of discharge aids (pneumatic, mechanical) are described.

Discharge of Bulk Solids

It has taken some time to obtain general acceptance but in recent times, at least in Australia, competent designers of mass-flow bins use techniques based on the traditional concepts of Jenike to determine the appropriate geometry for mass-flow hoppers to handle bulk solids reliably. While the traditional Jenike design concepts may appear straightforward experience dictates that some important considerations need to be exercised during the design process, especially when handling the more difficult bulk solids, to ensure that the final bin construction performs to expectations. Some of the important considerations that this paper will highlight include: • Appropriate bulk solids sampling for flow property testwork; • Interpreting flow property test results; • Applying flow property test results to determine appropriate hopper geometries; • Detail design issues; • Special requirements for particular circumstances (eg segregation, fine powders); • Design auditing.

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Determining the geometry of mass-flow bins - some important considerations

The uniaxial tester is an instrument where powder samples can be consolidated uniaxially in a die at different stress levels. After consolidation the die is removed and the axial compressive strength is measured. By repeating the procedure at different consolidation stress levels, the compressive strength is determined as a function of the consolidation stress, indicating the flow properties of the powder. Advantages of this method are that it is relatively simple to use, and it has a reproducibility that is better than most other methods. In the work to further improve the reproducibility, it has been found that the procedure of filling the die is very important. Three different procedures therefore have been tested, including one using vibration to pack the sample during filling of the die. Although the procedure using vibrations so far has not improved the reproducibility, it may still reduce the operator dependency. Results of some preliminary work to develop an improved filling procedure are reported on here.

Storage and Flow of Solids

Citations

Grinding sludge oil recovery transportation system development.

Discharge of Bulk Solids

Determining the geometry of mass-flow bins - some important considerations

Investigation on the effect of filling procedures on testing of flow properties by means of a uniaxial tester

Modelling of tensile strength of a powder bed in a pendular state

Related Papers (5)

Flow property measurement of food powders and sensitivity of Jenike’s hopper design methodology to the measured values

Evaluating flow properties of solids.

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Statics and Kinematics of Granular Materials

Review on testers for measuring flow properties of bulk solids