Advanced Coal Cleaning Technology
AUTHOR: Gordon R. Couch
DATE: December 1991
This report reviews recent developments in established practice. In particular:
- principal separation methods;
- instrumentation and control;
- management aspects and operational philosophy;
- application to low rank coals.
The report describes advanced cleaning methods:
Physical separation often requires milling the coal to below 100 micrometers in order to obtain sufficient liberation of mineral matter. However, as particles become smaller the effects of turbulence and viscosity in the separating medium increase. Gravity separation, based on micronised magnetite can be used for particles down to 50 micrometers. For smaller particles methods which depend on differences in surface properties are normally used. These include froth flotation, column flotation, selective agglomeration and flocculation.
Chemical cleaning may also remove organic sulphur but often at the expense of a reduction in volatile matter.
Biological methods may remove up to 90% of pyritic sulphur but reaction rates are slow and process conditions require precise control.