Detailed measurements in a pulverized coal flame with natural gas reburning

• Published in: Fuel (Guildford) Vol. 78; no. 6; pp. 689 - 699
• Main Authors: Nazeer, Waseem A., Jackson, Robert E., Peart, Jacob A., Tree, Dale R.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1999; Elsevier
• Subjects: Applied sciences; Burnout; Combustion of solid fuels; Combustion. Flame; Emissions; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fuel staging; Pulverized coal flame; Reburning; Theoretical studies. Data and constants. Metering; NO; Burnout; Pulverized coal flame; Fuel staging; Reburning; Emissions; Concentration measurement; Measurement; Air pollution control; Temperature; Pulverized coal; Combustion; Afterburning; Natural gas
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/S0016-2361(98)00197-5

Gas composition and temperature profiles were measured inside a 200
kW, entrained flow, pulverized coal Controlled Profile Reactor, using reburning for NO reduction. NO, CO, CO
2, NO
x
, O
2, and NH
3 samples were collected with a water-cooled and water-quenched stainless steel probe and analyzed on a dry basis with on-line gas analyzers and an ion-sensitive electrode (NH
3) over a grid of 36 locations within the reactor. Temperature data were obtained with a suction pyrometer using an S-type shielded thermocouple. NO reduction with reburning was investigated over a range of residence times and reburning zone stoichiometric ratios to optimize for maximum NO reduction in the flue gases. A decrease in stoichiometric ratio of the reburning zone resulted in an increase in NO reduction up to a maximum of 70% at a stoichiometric ratio of 0.78. The residence time in the reburning zone was varied by moving the tertiary air injector up and down axially. Increasing residence time in the reburning zone was initially beneficial but became unimportant when residence time became longer than 700
ms. The location of the reburning zone was found to be optimal when reburning fuel was directed at the location of highest NO concentration (i.e., immediately following NO formation). In comparison to a baseline case without reburning, the rate of carbon burnout was found to be higher with 20
cm of primary fuel injection, but proceeded very slowly through the reburning zone. At the end of the reactor, burnout was more complete in the baseline case. The species, temperature, and solid sample elemental concentrations appeared to be self-consistent and should provide accurate data for comparison with modeling results.