PMET's patented Jet Mill Comminution/Classification, Mechanical Grinding/Classification and Mechanical Separation technologies provide operators of coal-burning power plants efficient, cost-effective means to convert fly ash waste into profitable high-margin products and avoid the cost and problems associated with landfill disposal of high volumes of ash. To assist in the cost-effective implementation of these processes, PMET offers a complete licensing and equipment package including ash testing, process optimization, and ongoing customer service and support at our state-of-the-art Jet-Mill Pilot Facility.


PMET's Jet Mill Comminution/Classification technology for removing unburned carbon from fly ash is based upon fluid air jet autogenous grinding and simultaneous air classification using standard commercially-available jet mill equipment available from Hosokawa Micron Power Systems. In this process, high-carbon ash is automatically introduced into the jet mill where it subjected to autogenous grinding by high energy particle-to-particle impact which liberates adhered and entrapped carbon and ash and separates the free and adhered ash and carbon. The higher density low-carbon ash particles fall back to the bottom of the unit and the lower density free and liberated carbon particles are carried out of the system and recovered. This process, with or without subsequent treatment of the ash:

  • is suitable for processing a wide variety of ashes regardless of initial carbon content, ash characteristics, or coal properties

  • is especially well suited for processing ashes generated at plants using low NOx burners

  • improves the pozzolanic properties of the ash

  • removes adhered and entrapped carbon

  • can be used with ammoniated ash

  • permits optimization of throughput and final ash content

  • consistently achieves carbon contents of <3%


For select ashes, PMET offers alternative Mechanical Grinding/Classification Processes, in which grinding is performed by ball milling, rod milling, or attritor milling with air classification performed by sweeping the mill with a controlled air flow. The choice of autogenous grinding or mechanical grinding depends upon the ash composition and particle size, the desired particle size of the product, and the carbon content desired.

PMET's Mechanical Separation Process for removing carbon from fly ash (U.S. Patent No. 5,887,724) is a simple one-step technique based upon selective screening of the ash. This process provides a very low cost alternative for separating non-combined carbon from selected ashes having a bimodal ash-carbon distribution. The process may be performed wet or dry.