FOUR STAGE, FLUIDIZED BED GASIFICATION PROCESS MINIMIZES NOX

FOUR STAGE, FLUIDIZED BED GASIFICATION PROCESS MINIMIZES NOX
F. Michael Lewis, Roger T. Haug, Environmental Engineering Division, Bureau of Engineering, City of Los Angeles
ASME Paper No. FBC99-0205, 15th International Conference on Fluidized Bed Combustion, Savannah, Georgia, May 16 - 19, 1999

Hyperion Setting Stage
Hyperion Setting Stage
Staged Gasification
Staged Gasification

Select image and "Original" to enlarge.

BACKGROUND AND INTRODUCTION

In 1981, after a long and thorough study of alternative methods of sewage sludge (biosolids) disposal, the City of Los Angeles (CLA) embarked on a pilot test program to incinerate dried sewage sludge from its Hyperion Wastewater Treatment Plant. This dried sludge is typically 47% ash, 53% combustible, and has an average higher heating value (HHV), moisture, ash-free (MAF) of 10,675 Btu/Lbm. The dried sludge is called sludge derived fuel (SDF). Approximately 8% of the MAF fraction of SDF is fuel-bound nitrogen. When SDF, with its extremely high fuel-bound nitrogen, was combusted in conventional multiple hearth and fluidized bed pilot plant furnaces, NOX emissions were extremely high (>1,000 ppm). Faced with this dilemma, the CLA initiated an R&D program to reduce NOX. The final result of this effort was the development of three (3) full-size, fluid bed gasifiers (two operational - one standby) that operated in a staged combustion mode. These furnaces were operated by CLA from 1986 to 1996.

This was a FOUR stage gasification process. A THREE stage gasification is illustrated below.

3-Stage Gasification
3-Stage Gasification

See attachment.

F. Michael Lewis
fml@earthlink.net

Hyperion Assembly 1
Hyperion Assembly 1
Hyperion Assembly 2
Hyperion Assembly 1

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