MagMill
The MagMill – a dry magnetic separation technology combining an existing pulverizer at a power plant with a magnetic separator – removes mineral contaminants from coal more efficiently and economically than can be done at a prep plant. Developed to be installed as a retrofit in pulverized-coal-fired power plants today, the MagMill offers the opportunity to change the design of new coal combustion or gasification plants which will have lower capital and operational costs.
The MagMill is being commercialized by MagMill LLC, a joint venture between EXPORTech Company, Inc. and Nalco Mobotec. A nominal 2-3 TPH MagMill demonstration unit has been installed at the DTE Energy Services' new processing and shipping facility for petroleum coke in Vicksburg, MS, to be used to demonstrate its ability to improve the quality of coals for clients of both companies. The DTEES CE Raymond 352 pulverizer and MagMill LLC's separators are shown below. The installation is now operational and available for testing. To schedule a site visit and/or coal testing, e-mail Dr. Robin Oder or call him at 412-573-0191. An overview of the MagMill is given below. For detailed information, visit the MagMill LLC web site.
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What is a MagMill?
The MagMill removes the hard to grind (low value HGI), dense (heavier than the hydrocarbon component of coal) and abrasive minerals (iron carbonate, iron pyrite, etc.) from coal while reducing grinding energy and abrasive wear and improving the quality of coal by lowering mineral content, sulfur, and hazardous trace metals.
The MagMill can treat all coals where the particles to be removed are at least feebly magnetic and are “liberated” or “semi-locked” in the nominal 8 mesh to 200 mesh size range. Ash, sulfur and hazardous trace metals must be associated with magnetic particles. Liberation is the function of the pulverizer. Removal is the function of the magnetic separator. Over 70 coals from all major American coal basins have been tested for their response to magnetic separation.
The MagMill concept as shown here as applied to a B&W MPS pulverizer but can be used with any vertical mill.
Coal feed falls onto the pulverizer grinding table from above and is slung outward as the table rotates beneath large metal tires which crush the coal as they roll over it. Hot air swirls upward around the outer circumference of the table and carries the fine coal released in the milling upward to the classifier at the top of the mill where oversize particles are separated and returned to the grinding table. The concentration of hard and abrasive minerals is significantly greater on the surface of the grinding table than in the feed coal because these minerals require more passes through the grinding zone to reach product specification than does the soft hydrocarbon component of the coal . The MagMill withdraws a stream of these concentrated minerals from the lower regions of the mill and passes it to a dry magnetic separator outside the pulverizer. The separator recovers the carbon for return to the mill and rejects minerals that otherwise would have gone to the burner. 