The Effect of HCl and SO₂ on NO_x Formation in Coal Flames

Abstract

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.

Interactions of CO, HCl, and SOx in pulverised coal flames

“…In order to consider the effect of HCl or SO 2 released from the coals on CO emissions, the baselines of HCl and SO 2 concentrations were measured for some operating conditions [24]. For various operating conditions, the base emission of HCl at the reactor exit varied in the range of 29 -83 ppmv for Polish coal, and 30 -95 ppmv for Goettelborn coal.…”

“…The trials were conducted in an entrained flow combustion reactor (EFCR) and the detailed description of this reactor may be found in the other paper [24]. The electrically heated reactor has five regulated heating zones with a maximum temperature of 1673 K. The combustion air can be preheated up to approximately 673 K. The carrying air with pulverised coal enters the burner centre, surrounded by the primary air and the secondary air.…”

“…The objective of this work was to perform an experimental and theoretical study of the interactions of CO, SO x , and HCl under pulverised coal combustion conditions. The influence of HCl and SO 2 on NO formation in coal flames can be found in a recent paper [24]. Experiments were performed in a flow reactor in the wall temperature range from 1223 to 1523 K. The added SO 2 or HCl concentrations were varied between 0 and 600 ppmv.…”

Influence of HCl on CO and NO emissions in combustion

“…During combustion or gasification, the chlorine is released as HCl and Cl 2 , which are known to act as inhibitor by catalyzing the recombination of radicals O, H, OH, and HO 2 in the flame. Therefore, HCl is likely to affect the oxidation of CO [2][3][4][5] and the formation of NO [6,7] in combustion.…”

“…Wei et al [7] found that the HCl addition decreased NO emission in pulverized coal flames and explained it by the competition between the reactions of NO formation and reduction. In the present paper, in order to study the effect of HCl on NO formation in gaseous volatile combustion, the experiments are conducted in an entrained flow reactor (EFR), for the first time.…”