The Effect of Sulfur Dioxide on the Formation of Molecular Chlorine during Co-Combustion of Fuels

Xie, Youjun; Xie, Wei; Liu, Kunlei; Dicken, Laura; Pan, Wei‐Ping; Riley, John T.

doi:10.1021/ef990173d

Cited by 20 publications

(8 citation statements)

References 15 publications

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“…For chlorine content higher than 1%, the I-TEQ value of the fly ash from the combustion of C4 (Ca = 3.25%) was lower (22%) than that of C3 (Ca = 0), and that of the fly ash from the combustion of S4 (Ca = 5.23%) was lower (5%) than that of S3 (Ca = 0). The results obtained in this study indicate that a calcium content of 3.25% or more inhibits the formation of dioxins, which agrees with the results of a study conducted by Xie et al (2000). Qin et al (2017) indicate that the increase of CaO/S was beneficial for suppressing PAHs formation and capturing SO 2 .…”

Section: Effect Of Calcium Content On Pcdd/fs In the Fly Ash Collected From The Baghousesupporting

confidence: 91%

Effects of Sulfur and Calcium Compounds on Dioxin Reduction in a Fluidized Bed Combustor

Shen

Wang

Chyang

et al. 2019

Aerosol Air Qual. Res.

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The focus of this study is the effects of sulfur and calcium compounds on reducing dioxins in fly ash collected from the baghouse of a pilot-scale fluidized bed combustor. Pelletized sawdust with various amounts of polyvinyl chloride (PVC), pyrite, and calcium hydroxide was used as the feeding material. The experimental results indicated an extremely low concentration of dioxin in the fly ash from the cyclone (0.025 to 0.284 ng g -1 ), and the concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the fly ash collected from the baghouse increased by 27.4% as the chlorine content increased from 0.568 to 1.136 wt%. The inhibition of PCDD/Fs by sulfur is not clear and can be attributed to the low content of copper (average 387 ppm), which serves as the catalyst for the Deacon reaction. Octa-chlorinated dibenzofuran (OCDF) was the major congener of the PCDD/Fs. The highest toxicity-equivalent (I-TEQ) of 2,3,7,8substituted congeners was 2,3,4,7,8-PeCDF, which accounted for 37% of the total congeners (average value). The correlation between the I-TEQ values and 2,3,4,7,8-PeCDF concentration of fly ash is also discussed.

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Section: Effect Of Calcium Content On Pcdd/fs In the Fly Ash Collected From The Baghousesupporting

confidence: 91%

Effects of Sulfur and Calcium Compounds on Dioxin Reduction in a Fluidized Bed Combustor

Shen

Wang

Chyang

et al. 2019

Aerosol Air Qual. Res.

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“…Xie et al (36) tested the impact of SO 2 on the Deacon reaction by flowing 250 ppm HCl and 0-1230 ppm SO 2 through a tube furnace at 800 • C in a background gas of N 2 containing 15% CO 2 , 0.2% CO, 5% O 2 , and 5% H 2 O. The product gases were trapped in a solution of phenol in methylene chloride, which formed chlorinated phenol when contacted with Cl 2 .…”

Section: Homogeneous Oxidation Of Mercurymentioning

confidence: 99%

Understanding the effects of sulfur on mercury capture from coal-fired utility flue gases

Morris

Morita

Jia

2010

Journal of Sulfur Chemistry

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Coal combustion continues to be a major source of energy throughout the world and is the leading contributor to anthropogenic mercury emissions. Effective control of these emissions requires a good understanding of how other flue gas constituents such as sulfur dioxide (SO 2 ) and sulfur trioxide (SO 3 ) may interfere in the removal process. Most of the current literature suggests that SO 2 hinders elemental mercury (Hg 0 ) oxidation by scavenging oxidizing species such as chlorine (Cl 2 ) and reduces the overall efficiency of mercury capture, while there is evidence to suggest that SO 2 with oxygen (O 2 ) enhances Hg 0 oxidation by promoting Cl 2 formation below 100 • C. However, studies in which SO 2 was shown to have a positive correlation with Hg 0 oxidation in full-scale utilities indicate that these interactions may be heavily dependent on operating conditions, particularly chlorine content of the coal and temperature. While bench-scale studies explicitly targeting SO 3 are scarce, the general consensus among full-scale coal-fired utilities is that its presence in flue gas has a strong negative correlation with mercury capture efficiency. The exact reason behind this observed correlation is not completely clear, however. While SO 3 is an inevitable product of SO 2 oxidation by O 2 , a reaction that hinders Hg 0 oxidation, it readily reacts with water vapor, forms sulfuric acid (H 2 SO 4 ) at the surface of carbon, and physically blocks active sites of carbon. On the other hand, H 2 SO 4 on carbon surfaces may increase mercury capacity either through the creation of oxidation sites on the carbon surface or through a direct reaction of mercury with the acid. However, neither of these beneficial impacts is expected to be of practical significance for an activated carbon injection system in a real coal-fired utility flue gas.

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“…At high S concentrations (S/Cl > 10), in the presence of H 2 O, inhibition of de novo synthesis is due to SO 2 oxidation to SO 3 reverting Cl 2 to HCl [174]. The same effect was found for lower S/Cl; below 2.5 [175], and also below 0.64 [166]. Another inhibition mechanism consists in the poisoning of Cu catalyst by formation of CuSO 4 (stable until about 800 • C) [158,165,166,[176][177][178].…”

Section: Origin Generation and Fate Of Pcdd/fs And Pahs In Combustion Processesmentioning

confidence: 63%

Insights into PCDD/Fs and PAHs in Biomass Boilers Envisaging Risks of Ash Use as Fertilizers

Lopes

Proença

2020

Applied Sciences

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Since ashes are a possible source of Persistent Organic Pollutants (POPs) contamination, their application in soils must be subject to more study and control. In this scope, feed residual forest biomasses and biomass ashes, collected along one year in four biomass power stations, were characterized mainly for their polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) and Polycyclic Aromatic Hydrocarbons (PAHs) contents. The biomasses present concerning levels of Cl (0.04–0.28%) that may lead to PCDD/Fs formation. The biomasses also contain OCDD (29–260 ng/kg) and 1,2,3,4,6,7,8-HpCDD (35 ng/kg) that may contribute to increased Toxic Equivalents (TEQs) of ashes, possibly involving dichlorination and ash enrichment mechanisms. While the World Health Organization (WHO)2005-TEQs in bottom ashes (14–20 ng TEQ/kg) reaches the proposed limit (20 ng TEQ/kg) for ash use as fertilizers, in fly ashes (35–1139 ng TEQ/kg) the limit is exceeded. PAHs are below 0.02 mg/kg in bottom ashes and 1.5–2.5 mg/kg in fly ashes, complying with the proposed limit of 6 mg/kg. As bottom and fly ash streams may contain different ash flows, a clear definition of ash mixes is required. Correlations between unburned carbon (C), PAHs and PCDD/Fs were not found, which highlights the need for compulsory PCDD/Fs analysis in ashes, independently of their origin, burnout degree or levels of other contaminants. A sensitivity analysis was performed to evaluate the impact of handling non-detected values, which showed more impact for TEQs values close to the proposed regulatory limit of PCDD/Fs. These findings highlight the need to define reporting protocols of analytical results for risk assessments and conformity evaluation.

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The Effect of Sulfur Dioxide on the Formation of Molecular Chlorine during Co-Combustion of Fuels

Cited by 20 publications

References 15 publications

Effects of Sulfur and Calcium Compounds on Dioxin Reduction in a Fluidized Bed Combustor

Effects of Sulfur and Calcium Compounds on Dioxin Reduction in a Fluidized Bed Combustor

Understanding the effects of sulfur on mercury capture from coal-fired utility flue gases

Insights into PCDD/Fs and PAHs in Biomass Boilers Envisaging Risks of Ash Use as Fertilizers

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