Weyerhaeuser Company Limited

Grant G Karsner

Terry N Adams

James F Lincoln

Robert M Spurrell

Gregory P Golike

The present invention relates to the recovery of heat values from biomass materials such as wood waste or peat. Wood waste or 'hog fuel' from the forest industries is of particular interest. It has been discovered that this material can be burned with no fossil fuel support in an air suspension-type burner without the need to finely pulverize the full fuel stream. One portion of the biomass fuel stream is ground so that it is less than 100 .mu.m in diameter. This fine portion serves as an ignition component and should comprise about 20% of the total heating value of the fuel, using a conventional air suspension burner, or 10% of the total heating value using a staged burner, when the burners are operated at full load. The balance of the fuel can be of much larger particle size. This can be up to about 10 mm or even greater in maximum dimension if used with a grate equipped boiler. If the boiler lacks a grate, the principle fuel component should not exceed about 1 mm in thickness and 4 mm in any other dimension if carryover is to be avoided. A key aspect of the invention is the discovery that the total amount of ignition fuel component should be maintained constant regardless of burner load. The principal fuel component is modulated to accommodate load swings. Thus, at lower loads a higher percentage of the total heat energy is derived from the ignition fuel component.

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Vorhees, NJ, United States of America

Grant G Karsner