Influence Of SO Research Articles

Inhibition of de novo synthesis of PCDD/Fs by SO 2 in a model system

The effect of sulfur dioxide (SO 2) on de novo synthesis of polychlorinated dibenzo- p-dioxins, dibenzofurans (PCDD/F) and biphenyls (PCB) was investigated in model systems containing carbon, activated by cupric chloride (CuCl 2). Five types of carbons (activated carbon, three types of carbon blacks, and graphite) were used to test the universal character of our results. The influence of SO 2 on speciation and behavior of copper compounds, catalytic oxidation of carbons, and formation of organic chlorine (extractable organic chlorine and non-extractable organic chlorine) was also studied to investigate the inhibition mechanism of SO 2 on de novo synthesis. It was found that SO 2 can sulfate CuCl 2, but does not react with CuO and CuCl 2·CuO in a 10% O 2/N 2 atmosphere at 300 °C. The suppression by SO 2 of organic chlorine (C–Cl) formation also confirmed these findings. It was also found that catalytic oxidation of carbons was strongly suppressed by SO 2. A dramatic decrease in PCDD/Fs formation was observed for all five carbons, while adding SO 2; at the same time the average chlorination level also decreased. However, the inhibiting effect on PCB was less apparent compared with that on PCDD/F. On the basis of the experimental results, the conversion of both cupric and cuprous chloride into the non-reactive sulfate was proposed as inhibition mechanism.

Influence of SO 3 on mercury removal with activated carbon: Full-scale results

Activated carbon injection is considered one of the most cost-effective options for mercury control at PRB-fired power plants. However, roughly 30% of sites firing PRB coal use SO 3 for flue gas conditioning. The presence of SO 3 in flue gas can decrease mercury capture by activated carbon, sometimes dramatically. Overcoming activated carbon performance limitations caused by SO 3 conditioning for units with this configuration is essential to enable these plants to cost-effectively meet pending mercury emission regulations. Ameren's Labadie Unit 2 fires PRB coal and uses SO 3 to enhance particulate capture in the electrostatic precipitator (ESP). Full-scale sorbent injection tests at Labadie were conducted from 2005–2007. Six sorbents were tested at SO 3 injection concentrations ranging from 0 to 10.7 ppm. Sorbent performance was evaluated at two injection locations (the air preheater (APH) inlet and outlet). Native mercury capture on fly ash was typically less than 15%. When the mercury sorbents were injected downstream of the air preheater, the SO 3 concentration resulted in a decrease in mercury capture from 85% (no SO 3 injection) to 17% (SO 3 injection set at 10.7 ppm). Mercury sorbents were more effective when injected upstream of the air preheater. With the SO 3 system off, mercury removal increased from 75% when injecting 5.1 lb/MMacf of brominated carbon at the APH outlet, compared to 95% when injecting at the inlet. With the SO 3 system on, test results indicated an increase from about 30% injecting at the outlet to 58% injecting at the inlet. Tests evaluating the ADA-ES patented onsite milling process showed that 85% mercury capture was achieved injecting 4 lb/MMacf of milled activated carbon compared to a requirement of 10 lb/MMacf to achieve the same removal using as-received carbon, representing a 60% reduction in activated carbon consumption. No changes in opacity, APH and ESP performance, or other balance-of-plant effects were observed in these tests.

Impacts of sulfur dioxide from Miyakejima on precipitation chemistry in Japan

Precipitation chemistry data of Japanese Acid Deposition Survey (JADS) by Japan Ministry of the Environment was analyzed to evaluate the influence of SO 2 emitted from the volcano of Miyakejima located in the Pacific Ocean 200 km south of Tokyo. Precipitation samples were collected with wet-only samplers on a daily basis at eight sites over Japan. The sampling periods (1997–2005) were divided into three periods in consideration of the start of the eruption, August 2000: 1997–1999 (Period A), 2000–2002 (Period B), 2003–2005 (Period C). The influence was evaluated in terms of the ratio before-to-after the eruption, B/A and C/A. The B/A ratios for mean nss-SO 4 2− concentration ranged from 1.1 to 2.3. The average pH decreased at most sites in Period B. The ratios for annual deposition were the same level as those of the concentration. The influence was also assessed for daily concentration and deposition at Tanzawa and Tsukuba, the two closest sites to Miyakejima. The cumulative frequency distributions of the daily nss-SO 4 2− concentration shifted to higher concentration for both sites in Period B. Daily pH cumulative frequency distributions shifted to lower values at both sites in Period B. The monthly fraction, nss-SO 4 2−/(nss-SO 4 2− + NO 3 −), increased immediately after the eruption onset. The eruption was found to have influenced concentrations and deposition of nss-SO 4 2− and pH on a national scale, and the sites closest to Miyakejima showed the largest influence.

Effect of SO 2 on the formation and evolution of volatile compounds in wines

The aim of this work was to study the influence of SO 2 on the formation and later evolution of volatile compounds in wine bottles made from fermentations of sterilized and inoculated must. For this purpose, Parellada must, sterilized and inoculated with Saccharomyces cerevisiae, was fermented with and without SO 2. Subsequently, the obtained wines were aged in bottle during 6 months at room temperature with and without SO 2. The results show that SO 2 hardly had any effect on the formation of volatile compounds during fermentation. However, the wine stored in bottle with SO 2 showed a higher concentration of volatile compounds, mainly esters and alcohols, than the wine aged in bottle without SO 2.

Modelling the atmospheric transport and deposition of sulphur and nitrogen over the United Kingdom and assessment of the influence of SO 2 emissions from international shipping

A statistical Lagrangian atmospheric transport model was used to generate annual maps of deposition of sulphur and oxidised and reduced nitrogen for the UK at a 5×5 km 2 resolution. The model was run using emissions for the year 2002. The model was compared with measurements of gas concentrations (SO 2, NO x , HNO 3 and NH 3) and of wet deposition and aerosol concentrations of SO 4 2−, NO 3 − and NH 4 + from national monitoring networks. Good correlation was obtained, demonstrating that the model is capable of accurately estimating the mass balance and spatial distribution of sulphur and nitrogen compounds in the atmosphere. A future emissions scenario for the year 2020 was used to test the influence of shipping emissions on sulphur deposition in the UK. The results show that, if shipping emissions are assumed to increase at a rate of 2.5% per year, their relative contribution to sulphur deposition is expected to increase from 9% to 28% between 2002 and 2020. The model was compared to both a European scale and a global scale chemical transport model and found to give broad agreement with the magnitude and location of sulphur deposition associated with shipping emissions. Enforcement of the MARPOL convention to reduce the sulphur content in marine fuel to 1% was estimated to result in a 6% reduction in total sulphur deposition to the UK for the year 2020. The percentage area of sensitive habitats with exceedance of critical loads for acidity in the UK was predicted to decrease by 1% with the implementation of the MARPOL convention.

An empirical rate equation for the partial removal of manganese from solution using a gas mixture of sulfur dioxide and oxygen

The oxidation of soluble manganese by SO 2–O 2 gas mixtures is known to occur via complicated reaction pathways. An empirical equation was derived for the rate of manganese precipitation from solution as a function of the gas composition, the concentrations of dissolved sulfur and O 2, and the solution temperature and pH. The relationships between the rate of manganese precipitation and each of these parameters were obtained from batch tests. The influence of SO 2 was described by both the SO 2 content of the gas mixture and the concentration of the dissolved sulfur arising from the dissolution of the SO 2 gas. The rate of manganese precipitation was found to be first order with respect to the dissolved O 2 concentration and inversely proportional to the pH of the solution. An Arrhenius relationship was used to relate the solution temperature to the rate of precipitation, from which an activation energy of 23.5 kJ/mol was calculated. The manganese(II) concentration had little influence on the rate at concentrations above 500 mg/L. The rate equations for each of the operating parameters were combined into a single empirical rate equation for manganese precipitation, which described all of the batch data and was also applicable to manganese precipitation in continuous mode.

Investigations of main factors affecting tropospheric nitrate aerosol using a coupling model

Factors affecting tropospheric nitrate aerosol formation were investigated through a number of sensitivity studies using the thermodynamic equilibrium model ISORROPIA and the condensed gas-phase chemistry model. Results indicate that the equilibrium concentration of nitrate aerosol varies with solar zenith angle, air temperature, relative humidity, initial SO 2 concentration, initial NO 2 concentration and initial NH 3 concentration. NH 3 concentration and solar zenith angle play the most important roles, followed by relative humidity and NO 2 concentration. It seems that the relations between nitrate aerosol and these four factors, as well as air temperature, are strong and highly nonlinear due to the coupling effect. The influence of SO 2 concentration on nitrate aerosol is near-linear and weak.

Influence of SO 2 on the consumption of nitrogen compounds through alcoholic fermentation of must sterilized by pulsed electric fields

The aim of this work was to study the influence of SO 2 on the use of nitrogenous compounds by yeast during wine alcoholic fermentation. Thus Parellada must was sterilized by a pulsed electric field treatment and inoculated with Saccharomyces cerevisiae Na33 strain. The fermentations were carried out with SO 2 (20 mg/l) and without SO 2. Results showed that yeast better consumed the amino acids in the first half of fermentation in the presence of SO 2. The final concentration of amino acids in the obtained wine was greater when the must was fermented without SO 2 than when the latter compound was present. Therefore, the presence of SO 2 facilitated the consumption of amino acids and, hence, such wine should have more complex flavour and better microbiological stability than that obtained from fermentation without SO 2.

Effect of SO 2 on the performance of Ag-Pd/Al 2O 3 for the selective catalytic reduction of NOx with C 2H 5OH

The influence of SO 2 on the performance of Ag-Pd/Al 2O 3 for the selective catalytic reduction (SCR) of NOx with C 2H 5OH was investigated experimentally. The activity test results suggest that Ag-Pd/Al 2O 3 shows a small activity loss in the presence of SO 2 when using C 2H 5OH as a reductant. In situ DRIFTS spectra show that the activity loss originates from the formation of surface sulphate species on the Ag-Pd/Al 2O 3. The surface sulphate species formation inhibits the formation of nitrate, whereas hardly changes the partial oxidation of C 2H 5OH. Compared with the NOx reduction by C 3H 6, an obvious suppression of the surface sulphate species formation was observed by DRIFTS experiment when using C 2H 5OH as a reductant. This phenomenon reveals the better catalytic performance and strong SO 2 tolerance of Ag-Pd/Al 2O 3-C 2H 5OH system.

Antioxidative response of Mesembryanthemum crystallinum plants to exogenous SO 2 application

The facultative halophyte, Mesembryanthemum crystallinum shifts its mode of carbon assimilation from the C 3 pathway to crassulacean acid metabolism (CAM) in response to many factors that lead to the generation of reactive oxygen species (ROS) at the cellular level. Reactive oxygen species have been suggested to be involved in the initiation of CAM induction. In our experiment we would like to test whether the space/place of ROS production could play a role in CAM induction. In the present studies we applied exogenously sulphur dioxide to M. crystallinum plants as an oxidative stress factor that accumulates mainly in chloroplasts. On the basis of our data, one can suggest that oxidative stress in the cellular space, mainly in chloroplasts, is not sufficient to induce functional CAM in M. crystallinum plants. The second aim was to evaluate the influence of SO 2 fumigation/sulphite incubation on the activity and mRNA transcript level of SOD isoenzymes, especially FeSOD, that is pointed out as a one of the first indicators correlating with the C 3/CAM transformation. The data indicate that the activity of FeSOD and CuZnSOD isoforms increase under SO 2/sulphite stress, despite of no induction of functional CAM. The increase of the activity level both of these enzymes were not accompanied by the induction of their mRNA transcript levels, suggesting a post-transcriptional regulation of activity of these enzymes. The pattern of FeSOD and CuZnSOD induction suggests that CuZnSOD might take over the role of FeSOD in conditions of severe oxidative stresses. The induction of CuZnSOD is probably due to the action of sulphite per se.

Effect of SO 42− on the corrosion behavior of cerium-based conversion coatings on galvanized steel

The cerium-based conversion coatings on galvanized steel were investigated and the influence of SO 4 2− on the corrosion behavior was evaluated. The coatings were prepared by a simple immersion of galvanized steels in an aqueous solution composed of cerium nitrate and sodium sulfate. The corrosion behavior was studied by means of potentiodynamic polarization measurements and neutral salt spray tests. The addition of SO 4 2− to the coating solution considerably improved the corrosion resistance of the conversion coatings. Atomic force microscope observation shows that deposits prepared from the solution with SO 4 2− have smaller crystalline size than those prepared without SO 4 2−. The results of X-ray photoelectron spectroscopy and titration curves demonstrate that SO 4 2− ions are incorporated in the coating during the conversion process. This indicates that SO 4 2− acts as a grain refiner and/or growth inhibitor, thus enhancing the corrosion resistance.

Sulfur deactivation of Pt/SiO 2, Pt/BaO/Al 2O 3, and BaO/Al 2O 3 NO x storage catalysts: Influence of SO 2 exposure conditions

Flow reactor experiments were performed to study the effect of SO 2 + O 2 and SO 2 + H 2 exposures on the NO x storage performance of Pt/BaO/Al 2O 3 and BaO/Al 2O 3 catalysts. In addition, Pt/SiO 2 samples were used to study the interaction between Pt and SO 2 under the two exposure conditions. For BaO/Al 2O 3 the two SO 2 exposure conditions caused similar deactivation of the NO x storage capacity, whereas for Pt/BaO/Al 2O 3 the decline in the NO x storage capacity was faster during the SO 2 + H 2 exposure than for SO 2 + O 2 exposure. The presence of Pt enhances the adsorption of SO 2 for both SO 2 exposure conditions. Quantitative analysis of sulfur showed that exposure to SO 2 + O 2 caused higher accumulation of sulfur in Pt/BaO/Al 2O 3 samples in comparison with SO 2 + H 2 exposure. Thus there is no correlation between the total amount of adsorbed sulfur in the samples and the reduction of the NO x storage capacity, probably because of the adsorption of sulfur on sites not necessarily important for the NO x storage process.

Influence of SO2 in the Reduction of NOx by Potassium-Containing Coal Pellets

The influence of SO 2 in the reduction of NO x by different potassium-containing coal pellets with catalyst loading between 7.9 and 16.8% was studied. For comparative purpose, a catalystfree sample was also checked. At several temperatures between 350 and 550 °C, 2-h isothermal reactions were carried out under NO x /O 2 /N 2 and NO x /SO 2 /O 2 /N 2 gas mixtures, and the results revealed that SO 2 inhibits drastically the potassium-catalyzed NO x -carbon reaction. The amounts of SO 2 retained on samples indicate that there is a direct relationship between these quantities and the potassium loading on samples. X-ray fluorescence, Fourier transform infrared-in situ, and X-ray diffraction techniques were used in order to prove the presence of sulfur on samples after the reactions with NO x /SO 2 /O 2 /N 2 and to elucidate the nature of the sulfur species formed. The cause of the loss in activity seems to be related to the SO 2 irreversible chemisorption on the catalyst, originating the formation of potassium-sulfur compounds.

Influence of southern oscillation and SSTs over Nino-3.4 region on the winter monsoon rainfall over coastal Andhra Pradesh

An analysis of the mean monthly data of 124 years reveals that the relationship between the Southern Oscillation Index in September and the winter monsoon rainfall (WMR) over Coastal Andhra Pradesh (CAP) is variable and non-stationary. In the recent four decades, however, SOI (Sept) is negatively and significantly correlated with CAP WMR. A similar analysis is performed using 50 years of mean monthly SSTs over Nino-3.4 region in August and September and CAP WMR to detect a possible relationship and there is a striking positive relation between them. In both of the above cases, the September signal is more significant in the recent four decades than for the other months and seasons for probable prediction of CAP WMR. Finally, to examine the influence of SO on the winter monsoon rainfall, a non-parametric test “Mann-Whitney Rank Statistics” test has been applied to the rainfall associated with extreme positive and negative SOI events

Frequency dependent conductivity of the thin film blend of electroluminescent poly( p-phenylene vinylene) with waterborne polyurethane as ionomer

The frequency dependent conductivity, σ( ω), of the blend containing two different charge carrying material, a conjugated polymer, poly( p-phenylene vinylene), PPV and an ionomer, waterborne polyurethane ionomer, WPUI, was investigated in the frequency ( ω) range from 0.1 to 1000 kHz by impedance spectroscopy and compared with the individual materials, PPV and WPUI, respectively. Clear differences could be seen in the dependence of ω on both real and imaginary parts of impedance between WPUI, PPV and the blend film. At high frequencies (>200 kHz), all the three materials, exhibit a power law dependence between σ( ω) and ω as σ( ω) ∝ω s . Simulation of s value through theoretical fitting reveals that the s value of the blend (1.108) is in between PPV (1.289) and WPUI (1.035) and signifies the mixed contribution of carrier transport of PPV and WPUI in the blend. The morphology of the blend as observed from atomic force microscopy (AFM) imaging reveals that WPUI connects the islanded parts of PPV and provides a path for carrier conduction. Results observed indicate that carrier transport operates through barrier hopping in these materials and the difference in the dependence of ω on σ in the blend is attributed from the influence of SO 3 − group in WPUI on the carrier transport of PPV.

Sulfur deactivation of NO x storage catalysts: influence of exposure conditions and noble metal

In the present study, barium-based NO x storage catalysts containing platinum, rhodium, or both noble metals were investigated. The influence of SO 2 exposure conditions on the performance of NO x storage catalysts was studied using flow reactor measurements, FTIR, and XPS where the samples were exposed to lean and/or rich SO 2-containing gas mixtures, simulating the conditions in a mixed lean application. The main results show that all samples are sensitive to sulfur and that deactivation is faster when SO 2 is present in the feed under rich conditions than under lean or continuous SO 2 exposure. It was also found that SO 2 affects the performance of noble metals strongly and that noble metal deactivation most likely occurs during the rich period of a NO x storage cycle. Additionally, the influence of the noble metals present in the catalysts was investigated with respect to sulfur sensitivity and it was found that a combination of platinum and rhodium seems to be preferable for retaining high performance (high NO oxidation and reduction activity) of the catalyst under SO 2 exposure and subsequent regeneration.

Effect of SO2 on CO and C3H6 oxidation over CeO2 and Ce0.75Zr0.25O2

Ceria and Ce0.75Zr0.25O2 were characterized before and after SO2 exposure to determine the effect of sulfation on the structural, morphological and catalytic properties of the solids. The X-ray diffraction (XRD), scanning electron microscopy (SEM) data, and BET measurements show that both CeO2 and Ce0.75Zr0.25O2 are susceptible to crystallite grain size growth and surface area loss under exposure to gaseous mixtures containing 20–40ppm SO2 at 600°C. The Ce0.75Zr0.25O2 is more resistant to morphological changes than CeO2. However, no bulk sulfites/sulfates were detected with either oxide. Both presulfation of the oxides and addition of 20ppm SO2 to a 1% CO+2% O2+N2 reaction mixture results in a significant suppression of the CO oxidation reaction. The effect of SO2 on CO oxidation was much less pronounced for the Ce0.75Zr0.25O2 than for the CeO2. Surprisingly, 20ppm SO2 in the 1100ppm C3H6+2% O2+N2 reaction mixture has a promoting effect on the oxidation of C3H6 catalyzed by CeO2. The influence of SO2 in the feed gas on the CO and C3H6 oxidation is discussed in terms of different mechanisms for these reactions.

On the promotion by SO2 of the SCR process over Ag/Al2O3: influence of SO2 concentration with C3H6 versus C3H8 as reductant

The catalytic reduction of NOx over 5% Ag/γ-Al2O3 was studied in the presence of various SO2 concentrations (between 0 and 100vppm) while using propane/propene as reductant either separately or as a mixture. A promotional effect on the catalytic activity was found for all SO2 concentrations. Propene as reductant was found to perform best. Measurements were performed for 6h time-on-stream during which maxima in the de-NOx activity were found. While these maxima occurred at different times, they were always at the same level percentage. The results provide evidence for differences in the de-NOx mechanism when replacing propene by propane.

The influence of SO 2 level and operating conditions on NO x and N 2O emissions during fluidised bed combustion of coals

The influence of SO 2 level and operating conditions on NO x and N 2O emissions during fluidised bed combustion of coals

Investigations of sulphur deactivation of NO x storage catalysts: influence of sulphur carrier and exposure conditions

The influence of SO 2, H 2S and COS in low concentrations on the deactivation of Pt/Rh/BaO/Al 2O 3 NO x storage catalysts was investigated. Different samples of the catalyst were exposed to synthetic gas mixtures mimicking lean/rich engine cycling in a mixed lean application at 400 °C. The lean gas mixture contained 8 vol.% O 2, 500 vol-ppm C 3H 6 and 400 vol-ppm NO balanced to 100 vol.% with Ar. The rich excursions were performed by switching off the oxygen supply. Sulphur, 25 vol-ppm of either SO 2, H 2S or COS, was added to the gas flow either during the lean, the rich or both periods. This procedure aimed at investigating the influence of the exposure conditions and therefore the lean and rich periods were kept equally long (5 min). In addition, thermodynamical calculations for the prevailing conditions were performed. It was concluded that all sulphur compounds investigated, i.e. SO 2, H 2S and COS, had similar, negative impact on the NO x storage ability of the catalyst and that they all showed increased deactivation rates during rich exposure compared to lean. During lean exposure, all sulphur carriers showed similar behaviour, while H 2S and COS caused severe loss of noble metal activity during rich exposure.