A NEW METHOD FOR WASHABILITY ANALYSIS OF FINE COAL PARTICLES USING WATER FLUIDISATION
Dr. Kevin P. Galvin
School of Engineering
University of Newcastle
NSW 2308, Australia
Wednesday, February 21, 2003 3:00pm
Ben Bandy Conference Center
Center for Applied Energy Research
Galvin and Pratten (1999) have previously reported the technique of utilizing the density segregation effect of a narrow size range of particles in a fluidised bed to determine washability data. This has been verified with replication of yield density information, but to date there has been no investigation of particle yield-ash distribution. This paper examines the procedure of using water fluidisation for attaining coal washability data with a view to providing a rapid, accurate and safe alternative to the current laboratory method of float-sink testing.
This test work has refined the method using a broad particle size range of -4.0+0.045 mm. We have identified that separation is a combination of the techniques of fluidisation and particle sizing. This study has shown that the final separation of the particles is independent of whether the material is initially sized into narrow particle size ranges for fluidising or if a broad size range is fluidised and the subsamples sized into individual fractions for analysis.
The new method has been extensively tested using a variety of Australian coals. Results indicate excellent agreement between the particle density distribution data generated by float-sink testing and the new method, although, comparison of particle ash distribution information shows some variation in the low ash region. This deviation between methods represents a reduced yield of low ash material and appears to be a function of the mechanics of the fluidisation process and cannot be entirely eliminated. The application of a universal correction factor to washability information generated by the new method has been employed to effectively remove any discrepancy with float-sink data.
The major advantage of the new water-based fluidisation technique is the significant reduction in the use of heavy organic liquids utilised in the float-sink procedure, and hence considerable health and environmental benefits. Finally, application of the new method to fine particles (-0.250 +0.045mm) has also produced results comparable to the standard laboratory technique of tree flotation.