Effect of Gaseous Inhibitors on PCDD/F Formation

Abstract

Emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) from municipal waste incineration are currently a subject of considerable public concern because of their extreme toxicity. PCDD/F formation in incineration processes is being studied widely, but studies on inhibition are quite sparse, especially in a pilot-plant scale. In this work, the effect of four gaseous inhibitors (sulfur dioxide, ammonia, dimethylamine, and methyl mercaptan) on PCDD/PCDF formation in the combustion of liquid fuel was studied using a pilot-scale plant. The inhibitors were injected into the flue gas stream after the first economizer at a temperature of 670 °C and just before the second economizer at 410 °C. Both the chlorophenol and PCDD and PCDF concentrations decreased when inhibitors were added. Particle-phase PCDD/F concentrations in particular decreased by up to 98%. The results suggest that the formation of PCDD/Fs is hindered in the particle phase at the early stages of the PCDD/F formation chain, probably even before precursors such as chlorophenols have been formed.

Effects of gaseous NH3 and SO2 on the concentration profiles of PCDD/F in flyash under post-combustion zone conditions

“…It suggests that varying the temperature within the tested range did not significantly affect the mechanism of PCDD/F inhibition by ammonia. This was consistent with the results reported by Ruokojarvi et al, (1998).…”

“…Consistent with a previous report by Ruokojarvi et al (1998), reduction of PCDF in the solid phase was slightly higher than that in the gas phase. This could be partly attributed to the suggestion that SO 2 can increase the gas/solid ratios of PCDD/F via promoting desorption of PCDD/F from the flyash matrix (Ke et al, 2010).…”

“…However, it is not clear why both 2378-TCDF and 123789-HxCDF gave the highest reduction and why 1234789-HpCDF and OCDF gave the highest formation in the presence of ammonia under these test conditions. These results are comparable with the results reported by Ruokojarvi et al (1998), who found that there was more reduction in the particulate phase than that in the gas phase when the gaseous ammonia was injected between two economisers at a temperature range of 670 to 410 ºC. They reported that the total PCDD/F concentration was reduced by between 42% and 78%.…”

“…Over the last two decades several nitrogen compounds and/or in combination with sulphur compounds, have been examined as potential inhibitors for PCDD/F formation during waste incineration and other combustion processes. Among others, the PCDD/F suppressing effects of some solid inhibitors including urea, ethylenediammine tetraacetic acid (EDTA), monoethanolamine (MEA), and triethanol-amine (TEA), and some gaseous inhibitors such as ammonia (NH 3 ), sulphur dioxide, amido sulphonic acid and dimethylamine (DMA) have been reported (Addink et al, 1996;Ruokojarvi et al, 1998;Tuppurainen et al, 1999;Samaras et al, 2000a;Samaras et al, 2000b;Ruokojarvi et al, 2001;Xhrouet et al, 2002;Kuzuhara et al, 2005;Marie-Rose et al, 2009;Williams, 2005).…”

Thermal Exploitation of Wastes with Lignite for Energy Production

“…MDF contains such compounds as urea, which could inhibit the formation of PCDD/ Fs. [25][26][27] Because of the large number of moving stokers installed in southeast Europe, the need of wastewood utilization and the importance of PCDD/F emissions the obtained results were discussed in detail (e.g., XAD resin, soot particles, congeners, homologue patterns) in refs 8, 24, and 28.…”