The effect of HCl and SO2 on NO
x
formation in coal flames was investigated experimentally
and kinetically in an entrained flow combustion reactor (EFCR). Two bituminous coals (German
“Goettelborn” and a Polish coal) were used as fuels with a feeding rate of 1 or 1.5 kg/h. HCl or
SO2 is added into the primary air for injection into the reactor. Experimental results indicate
that when HCl is added in the range from 0 to 610 ppmv, NO
x
emissions are reduced by 0−20%.
The measured NO
x
profiles along the reactor length clearly show that the addition of HCl reduces
NO
x
formation. Under air-staging conditions, HCl addition has almost no influence on NO
x
emissions presumably because of the different reaction mechanisms. The effect of added SO2 on
NO
x
emissions is less significant than the effect of added HCl. A detailed kinetic mechanism is
used to model the reactions, and the controlling reactions are analyzed.
In the paper, the numerical simulation program coupled with the detailed chemical reaction mechanism and computational fluid dynamics software was applied to calculate the concentration profiles of CO, NO x , and SO x during cocombustion of coal and biomass. The predicted data are compared to experimental results in an entrained flow combustion reactor to validate the numerical method for pulverized coal combustion. The characteristics of pollutant emissions in cocombustion with coal and three typical kinds of biomasses (Swedish wood, Danish straw, and sewage sludge) are also investigated. NO formation is significantly affected by the reactor temperature, and an increasing temperature obviously enhances the NO concentration. In the range of the calculated temperature, the final SO 2 emission level is not obviously influenced by the temperature. Co-combustion technology could effectively reduce the pollutant emissions, and the effect is proportional to the blending ratio of biomass. The biomass with low contents of nitrogen and sulfur and a high volatile content and lower heating value is an ideal co-fired fuel to reduce NO and SO 2 emissions.
The effect of HCl and SO 2 on CO oxidation in pulverised coal flames was investigated experimentally and kinetically in an entrained flow combustion reactor. Two bituminous coals (German 'Goettelborn' and a Polish coal) were used as fuels with a feeding rate of 1 or 1.5 kg/h. HCl or SO 2 is introduced into the reactor premixed with the primary air. Experimental results indicate that HCl addition may inhibit CO oxidation in coal flames and increases CO emission. Reducing temperature in the reactor will enhance the inhibitory effect of HCl on CO oxidation. The measured CO profiles along the reactor height clearly show that the addition of HCl may inhibit CO oxidation. In the experimental range of SO 2 addition, the inhibiting effect of SO 2 on CO oxidation is less significant than HCl. A detailed kinetic mechanism is used to model the reactions, and the controlling reactions are analysed. q
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