Laboratory study of N2O formation from burning char particles at FBC conditions

• Coal combustion in fluidized bed combuster is a cause of nitrous oxide emissions to the atmosphere. The formation of NzO seems to be related both to homogeneous and heterogeneous reactions taking place in the combustion process. The purpose of this investigation was to study the formation of NzO from burning char particles under different combustion conditions. The experiments were carried out in a fmed bed reactor containing quartz sand (SiOz) to support the coal particles. A monolayer of bituminous coal particles between two layers of quartz sand was devolatilized prior to the actual combustion in an argon flow. The coal particle sizes were varied between 0.090 and 2.80 mm. The inlet gas mixture contained NO, 0 2 , and Ar or just 0 2 and Ar. The oxygen concentration was varied between 0.5 and 20% 0 2 and the NO concentration was varied between 0 and 1000 ppm NO. The inlet gas flow was varied between 590 and 1581 mL/ min NTP (273 K, 1 atm) and the bed temperature was varied between 1023 and 1123 K. The off-gases were analyzed for NzO, NO, CO, and COZ. Addition of NO to the flue gas increased the NzO yield. A low combustion temperature also favors high yields of N20. A great influence of the oxygen concentration was found (high oxygen concentrations give low Nz0 yields), which indicates that the combustion conditions are very important for the NzO yield. A particle size of 1 mm gives the highest NzO yields.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Naturresursteknik -- Annan naturresursteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Environmental Engineering -- Other Environmental Engineering (hsv//eng)

NATURVETENSKAP  -- Kemi -- Oorganisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Environmental Sciences (hsv//eng)

Nyckelord

nitrous oxide

formation

char

particles

fluidised bed

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