Advanced combustion system for industrial boilers. Phase 2, Quarterly technical progress report, April--June 1990

Abstract

(1) A ZrO{sub 2} oxygen sensor was calibrated successfully over the concentration range from 0 to 21 percent O{sub 2} at temperatures from ambient to 400{degrees}F. This inexpensive automotive sensor provides 8 signal which will be used to monitor and automatically control combustion conditions to maintain consistently high combustion efficiency combined with low NO{sub x} emissions; (2) An improved burner was designed and fabricated with an initial ``stage`` which functions as a coal-eductor/coal-air mixer. Now coal can be transported in dense phase to the burner without pressurizing the coal-storage hopper which had approximately a four-hour capacity. This permits refilling the hopper during periods of continuous operation of the boiler as required for commercial use; (3) The improved burner produced the highest boiler efficiency to date. Carbon burnout improved to 98.9 Percent, compared to about 97 percent during Phase I testing for the same Upper Elkhorn No. 3 coal with 2.7% ash. We expect to exceed 99% Combustion efficiency with all of the test coals during more optimized future testing; and (4) Although the new burner proved to be very efficient, emissions of NO{sub x} were higher than those observed during Phase I testing. The new-burner design was modified. Capability for deep air-staging was added to the new burner to promote low-NO{sub x} operation.