Low SO2 Research Articles

Evaluation of Electrochemical Properties of La0.6Sr0.4Co0.2Fe0.8O3-δ Porous Electrode with Sulfur Poisoning

The effect of low concentration SO2 (0.01ppm) in the air on the degradation of a La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) cathode of solid oxide fuel cells was investigated as a function of temperature and poisoning time. The performance degradation of LSCF cathode depends on the operating temperature. At 923 K, rapid degradation is observed due to the sulfur deposited at whole surface of LSCF particles which inhibits oxygen reduction reaction process. In contrast, for 1023 K, the SrSO4 formation concentrates at some localized parts of the surface LSCF. As a result, slow degradation was observed over period of poisoning time.

Observations of trace gases, photolysis rate coefficients and model simulations over semi-arid region, India

Continuous ground-based measurements of CO, SO2 and NO2 were carried out in a semi-arid rural area, Anantapur [14.62 0N, 77.65 0E], Southern India, for the period January 2012–December 2012. The maximum CO concentration was observed in winter (310 ± 17 ppbv) followed by summer (180 ± 21 ppbv) and post monsoon (174 ± 20 ppbv), while the minimum in monsoon (72 ± 9 ppbv). Seasonal mean NO2/NOx ratios for monsoon, post monsoon, winter and summer were about 0.88, 0.91, 0.76 and 0.80 respectively, indicating a higher conversion of NO to NO2 over the measurement site. Monthly mean low SO2 mixing ratio was found (0.46 ± 0.02 ppbv) in monsoon and high (2.42 ± 0.21 ppbv) in winter. Keeping the emissions aside, the levels of CO, SO2 and NO2 were influenced by meteorology, urban effects and trans-boundary transport in the lower troposphere. Atmospheric boundary layer (ABL) had the good correlation coefficient (R = 0.76) with solar radiation during daytime, while it was mainly correlated with wind speed during night time (R = 0.42). Diurnal trend of atmospheric visibility was found to be maximum during noon times at around (14:00–16:00 h) about 76 k.m. and minimum during morning periods (06:00–08:00 h) about 45 k.m. A strong positive correlation was observed between BC and CO (R = 0.71) with an average slope, suggesting common or proximate sources likely to be traffic emissions contribution for the production of BC and CO. The SO2/NOx and CO/NOx study were strongly suggested that mobile sources were larger contributors over the site and the evidence of transport of emissions from other surrounding regions. Tropospheric Ultraviolet Visible (TUV) radiative transfer model was used to calculate the Photolysis rate coefficients (J(O3), J(NO2)). Chemical box model (NCAR-MM) was used to simulate diurnal variation of CO and the results were reported.

Hydrogen chloride emissions from combustion of raw and torrefied biomass

Elevated emissions of hydrogen chloride (HCl) from combustion of biomass in utility boilers is a major issue as it can cause corrosion and, in combination with the high alkali content often encountered in these fuels, it can also deposit molten alkali chloride salts on the boiler’s water tubes. Such deposition can impede heat transfer and cause further corrosion. This work torrefied and then burned herbaceous biomass (corn straw) as well as crop-derived biomass (olive residue and corn-based Distillers Dried Grains with Solubles, DDGS), all pulverized in the size range of 75–150µm. It monitored the HCl emissions from torrefaction of biomass and, subsequently, the comparative HCl emissions from combustion of both raw and torrefied biomass. Results showed that during torrefaction most of the chlorine of biomass was released in the gas phase, predominately as HCl. Consequentially, combustion of torrefied biomass, which contained less chlorine than raw biomass, generated significantly lower HCl emissions than raw biomass, particularly so for biomass of low alkali content. This observation complements previous findings in this laboratory that torrefied biomass also generated lower SO2 emissions than raw biomass, albeit by a smaller factor. Both of these findings enhance the appeal of torrefied biomass as a substitute fuel in utility boilers.

Reduction of SO2 to elemental sulfur with H2 and mixed H2/CO gas in an activated carbon bed

Experiments and thermodynamic equilibrium calculations were carried out on a H2-SO2 system. The effects of temperature, H2/SO2 ratio, and retention time on SO2 reduction in an activated carbon bed were studied. The equilibrium calculations showed elemental sulfur to be the major S-containing product of SO2 reduction at low H2/SO2 ratios. However, when the H2/SO2 ratio was greater than three, the calculations predicted that SO2 would be completely reduced to H2S with elemental sulfur completely absent from the reduction products. The experimental results showed that the starting temperature for reduction of SO2 with H2 is 600°C. In the presence of activated carbon, the starting temperature decreased and an obvious increase in the SO2 conversion and S yield was achieved at temperatures below 800°C. The experimental results showed a lower SO2 conversion and higher S selectivity than those predicted by the equilibrium calculations because equilibrium was not achieved under the experimental conditions. Higher H2/SO2 ratios and longer retention times were beneficial to SO2 conversion. They also improved the S yield initially; however, subsequently, the yield decreased because an increase in S-containing byproduct formation after complete SO2 conversion was achieved. The activity of mixed H2/CO gas for SO2 reduction was also probed. CO displayed a higher SO2 reduction activity in comparison with H2. COS was the major S-containing byproduct at lower temperatures, while H2S was the main byproduct at 800°C. At a H2/CO ratio of 1, the optimum SO2 conversion and S yield achieved were 99.3% and 79.3%, respectively, at 700°C with a (H2+CO)/SO2 ratio of 2.5.

High-performance sulfur dioxide sensing properties of layer-by-layer self-assembled titania-modified graphene hybrid nanocomposite

This paper demonstrates layer-by-layer (LbL) self-assembled titania (TiO2)/graphene film device towards ultralow sulfur dioxide (SO2) gas sensing at room temperature. The as-prepared film was realized through the layer-by-layer alternative deposition of TiO2 nanospheres and graphene oxide (GO) to form a nanostructure, and followed by thermally reducing GO into reduced graphene oxide (rGO). The nanostructural, morphological and compositional properties of TiO2/rGO sample was examined by SEM, TEM, XRD, EDS and Raman spectroscopy. The gas-sensing properties of TiO2/rGO hybrid were investigated at room temperature against low concentration SO2 gas. The sensor in our work exhibited ppb-level detection, rapid response and recovery, good reversibility, selectivity and repeatability for SO2 gas sensing. The possible sensing mechanism for the presented sensor was attributed to the synergistic effect of TiO2 and rGO, as well as special interaction at TiO2/rGO interfaces. This work shows that the fabricated TiO2/rGO film sensor possesses potential applications for SO2 detection with advantages of cost-effective, low power consumption and distinguished sensing abilities.

Using Ionic Liquid Mixtures To Improve the SO2 Absorption Performance in Flue Gas

The functional ionic liquids (ILs) [NH2emim][OAc] and [NH2emim][BF4] were synthesized for SO2 capture. Although functional ILs have potential advantages in SO2 absorption, the high viscosity of a single IL markedly affects the SO2 absorption separation process. To improve the SO2 absorption performance, [NH2emim][OAc] and [NH2emim][BF4] were mixed with low-viscosity imidazolium-based ILs [bmim][OH]/[bmim][BF4]. When the mole ratio of [NH2emim][OAc]/[bmim][OH] is about 1:1, the binary mixture has the best SO2 absorption capacity. The SO2 absorption performance was investigated in the simulated flue gas, where SO2 partial pressure was about 0.2 kPa. Under the low SO2 partial pressure, the absorption capacity of the [NH2emim][OAc] + [bmim][OH] mixture was more than 0.7 mol of SO2/mol of IL, which was superior to that of a single IL. The regeneration test of [NH2emim][OAc] + [bmim][OH] showed that the binary mixture had high reversibility and the SO2 absorption capacity almost kept constant after 12 recycles....

Comparative study on sulfur poisoning of V2O5-Sb2O3/TiO2 and V2O5-WO3/TiO2 monolithic catalysts for low-temperature NH3-SCR

The V2O5-Sb2O3/TiO2 monolithic catalyst prepared by an impregnation method showed superior deNOx performance compared with the commercial V2O5-WO3/TiO2 catalyst in the presence of sulfur dioxide. In addition, it exhibited remarkable sulfur resistance at 250°C for 30h test due to the low deposition of NH4HSO4, suggested by the TG and MS results. The lower SO2 oxidation and higher reactivity of NH4HSO4 with NO are the key factors for the low deposition of NH4HSO4 over this Sb-modified monolithic catalyst.

Redox, acid-base and clinical analysis of preterm and term neonatal lambs.

During pregnancy, fetal lambs are exposed to low oxygen tension. Thus, an effective antioxidant mechanism is partially developed which sensitizes fetus to oxidative stress. Consequently, term and preterm neonates are susceptible to molecular and cellular injury caused by oxygen species (ROS). This study aimed to evaluate the development of antioxidant enzymes and oxidative profile of preterm (135 days of pregnancy) and term (145 days of pregnancy) neonatal lambs, correlating with clinical analysis. Preterm lambs had significantly (P ≤ 0.05) lower score of vitality (4.00 ± 1.10), bradycardia (99 ± 34 bpm) and bradypnea (13 ± 10 mpm). However, both groups were normothermic and euglycemic. Preterm group had low blood pH (7.07 ± 0.10) and both groups had hypercapnia, more severe in preterm group (85.52 ± 18.65 mmHg). In addition, premature newborns had lower pO2 (10.67 ± 5.65 mmHg) and SO2 (6.17 ± 5.85%) values. No significant difference (P ≥ 0.05) on antioxidant enzymes and oxidative stress were verified among experimental groups, although glutathione peroxidase negatively correlated with Apgar score, heart rate, SO2 and pO2. Our data show that preterm neonates are less adapted to the odds of labor and to overcome the immediate changes of extra-uterine life. Furthermore, we verified an influence of glutathione peroxidase in controlling oxidative stress, which highlights mature enzymatic mechanisms of cell redox, even in premature lambs.

Anterior vena caval oxygen profiles in a deep-diving California sea lion: arteriovenous shunts, a central venous oxygen store and oxygenation during lung collapse.

Deep-diving California sea lions (Zalophus californianus) can maintain arterial hemoglobin saturation (SO2 ) above 90% despite lung collapse (lack of gas exchange) and extremely low posterior vena caval SO2 in the middle of the dive. We investigated anterior vena caval PO2and SO2 during dives of an adult female sea lion to investigate two hypotheses: (1) posterior vena caval SO2 is not representative of the entire venous oxygen store and (2) a well-oxygenated (arterialized) central venous oxygen reservoir might account for maintenance of arterial SO2 during lung collapse. During deep dives, initial anterior vena caval SO2 was elevated at 83.6±8.4% (n=102), presumably owing to arteriovenous shunting. It remained high until the bottom phase of the dive and then decreased during ascent, whereas previously determined posterior vena caval SO2 declined during descent and then often increased during ascent. These divergent patterns confirmed that posterior vena caval SO2 was not representative of the entire venous oxygen store. Prior to and early during descent of deep dives, the high SO2 values of both the anterior and posterior venae cavae may enhance arterialization of a central venous oxygen store. However, anterior vena caval SO2 values at depths beyond lung collapse reached levels as low as 40%, making it unlikely that even a completely arterialized central venous oxygen store could account for maintenance of high arterial SO2 These findings suggest that maintenance of high arterial SO2 during deep dives is due to persistence of some gas exchange at depths beyond presumed lung collapse.

Combustion properties of torrefied biomass obtained from flue gas-enhanced reactor

Torrefaction is the process of thermal treatment that leads to enhanced biomass properties. Specifically, torrefaction of raw biomass can lead to higher energy density, improvement of handling and grinding properties, and other advantages. This work investigates the combustion properties of torrefied biomass obtained from the torrefaction of willow (Salix viminalis) in the presence of flue gas. The properties were compared with other solid fossil fuels such as Polish hard coal and Polish lignite. The comparison was based on proximate and ultimate analyses as well as the combustion of the fuels using an auto-thermal bubbling fluidized bed reactor. The combustion process of torrefied willow was stable, and the most promising result was radically low SO2 emission levels. However, the relatively high NOx emission should be decreased by the application of primary or secondary methods of NOx removal.

Selection of a New Highly Resistant Strain for Malolactic Fermentation under Difficult Conditions

Malolactic fermentation (MLF) is a biological process that contributes to wine quality, but it is frequently affected by various vinification conditions. Resistance to four wine-limiting factors was studied with respect to 10 Oenococcus oeni strains in order to select a suitable strain for performing reliable MLF in difficult wines. Resistance to low fermentation temperature, high SO2 and/or ethanol concentration, and low pH were assayed in laboratory tests. A pool of the most resistant strains was used in a set of laboratory MLFs. At the end of fermentation, the dominant strains were identified by RAPD-PCR. The PN4 strain was found to be dominant in the majority of cases and under the most detrimental wine conditions, and it was therefore chosen as the single-strain inoculum for the subsequent MLF trials. The effectiveness of the PN4 strain was confirmed in a series of MLFs carried out in three different countries under experimental and industrial conditions. It accomplished MLF in wines with up to 15.8% ethanol, pH as low as 3.0, 60 mg/L of free SO2, and in fermentation temperatures below 17oC. Our findings indicate that the O. oeni PN4 strain could be an effective starter, guaranteeing regular and reliable MLF fermentation.

The role of limestone during fluidized bed oxy-combustion of coal and biomass

The interest in bio-CCS technologies is growing due to their potential to reduce CO2 emission in power generation. Oxy-co-firing in fluidized-bed units is one of the available techniques to develop bio-CCS, offering wide fuel flexibility and low SO2 and NOx emissions. This paper discusses the results of an experimental campaign carried out in a lab-scale fluidized bed reactor. The work focuses on the influence of limestone when oxy-firing blends of lignite and corn stover. Two different types of limestone with two Ca:S molar ratios were tested, and operational conditions were selected to compare the mechanisms governing desulphurization. Emissions of SO2, NO and HCl, together with deposition rates and ash mineralogy are studied in the paper. SO2 capture increases with the Ca:S ratio and bed temperature, but to a different extent depending on the limestone fragmentation. The amount of NO emitted rises with the Ca:S ratio and the presence of calcined limestone (indirect desulphurization). The HCl concentration in the gas phase is dominated by alkali sulfation. Finally, the conditions for the highest desulphurization efficiency diminished the deposition rates, but increased the risk for chlorine-induced corrosion.

Co-Firing of Fast Pyrolysis Bio-Oil and Heavy Fuel Oil in a 300-kWth Furnace

Combustion characteristics and pollutant emissions of burning fast pyrolysis bio-oil/heavy fuel oil (HFO) blends in a 300-kWth furnace are investigated. Lauan (shorea) wood is used as biomass feedstock for making bio-oil via a fast pyrolysis process. The bio-oil has high viscosity, high water and oxygen content, as well as a low heating value. A furnace test is conducted for pure HFO and bio-oil/HFO blends with various mixing ratios. The results show that instability occurs during the test for cases with more than 5% bio-oil in the emulsion. Notably, it is verified that burning a bio-oil/HFO blend with a 2.5% bio-oil and a 97.5% HFO exhibits similar furnace performance and has lower NO and SO2 emission levels as compared to burning pure HFO. The reductions of NO and SO2 emissions are 2.6% and 7.9% for this blend, respectively.

Carbon, sulfur and nitrogen oxide emissions from combustion of pulverized raw and torrefied biomass

This work contrasted gaseous emissions of carbon, sulfur and nitrogen oxides from combustion of several types of biomass including woody, herbaceous and crop-derived wastes, pulverized in the size range of 75–150μm. Both raw and torrefied biomass were exposed to high heating rates (104–105K/s) in a laboratory-scale electrically-heated drop-tube furnace, operated at 1400K. Combustion occurred under fuel-lean conditions. Torrefied biomass has lower volatile matter content, higher fixed carbon content and higher heating value than raw biomass. Results revealed that (a) CO2 emission factors from torrefied biomass were higher than those from raw biomass, reflecting the higher carbon content of the former, however there was no uniform trend in emission factors (kg/GJ); (b) SO2 emission factors of torrefied biomass were lower than those from raw biomass, even if some torrefied biomass types contained higher sulfur mass fractions than their raw biomass precursors. All raw and torrefied biomass, with one exemption, generated lower SO2 emission factors than a typical sub-bituminous coal; (c) torrefied biomass has higher fuel-nitrogen mass fractions than their raw biomass precursors; however, there was no clear trend in NOx emission factors between raw and torrefied biomass, as torrefied herbaceous and woody biomass types generated higher while torrefied crop biomass types generated lower emission factors than their raw biomass precursors. Comparing with the sub-bituminous coal, some raw and torrefied biomass types generated lower and some higher NOx emission factors. Overall, combustion of most types of biomass, either in raw or torrefied state, can result in lower SO2 and NOx emissions factors than those of typical western US sub-bituminous coals while, in principle, generating minimal net emissions of carbon.

Environmental regulation and productivity: The case of electricity generation under the CAAA-1990

This paper measures the impact of the 1990 Clean Air Act Amendments on coal-fired boilers' productivity and output. The Act led to generating units adopting a number of different pollution abating behaviors, one of which was an input change to lower SO2 emitting coal. A key feature of the production technology is that each boiler is designed to burn a particular variety of coal, with significant deviations from the targeted coal characteristics resulting in productivity losses. Using data for the 1985–1999 period, I present empirical evidence of the policy impact. The main findings are that productivity declined between 1% and 2.5%, on average, and output losses ranged from 1% to 6% for affected boilers, varying across regions and over time.

Progress in SO<sub>2</sub> capture by ionic liquids

Minimizing the emissions of SO2 is highly important, because it is a significant source of atmospheric pollution that threatens environment and human health. SO2 can be absorbed by ionic liquids (ILs) due to their unique properties, such as ultra low vapor pressure, wide liquid temperature range, non-flammability, chemical stability, and tunable structure and properties. As a new sorption technology, ILs with useful functional groups are attracting the attention of a growing number of scientists and engineers in recent years. In this article, the recent advances on the studies of ILs in the capture of SO2 were reviewed, where traditional ILs and functionalized ILs were included. Traditional ILs with the anions such as BF4 - , PF6 - , Tf2N - , F - , Cl - , Br - and I - could uptake SO2 at ambient temperature and pressure through physical interaction between IL and SO2, but they could not be used under industrial conditions because of the weak interactions. Industrial condition means high temperature and low SO2 partial pressure, which needs strong interaction between IL and SO2. Functional ILs, including organic acid salt ILs, phenolate ILs, azolate ILs, ether-based ILs, amine-based ILs and multi-functional ILs, showed highly efficient SO2 absorption under ambient conditions. 1,1,3,3-Tetramethylguanidine lactate ([TMG][L]) was the first functional IL used to achieve about equal mole SO2 capacity under 40°C and 8% SO2 through chemical interaction. [SCN]-based ILs were proved to be highly efficient and reversible ILs for SO2 capture under low partial pressure by the single-site interaction mechanism. Although ether-based ILs could achieve much higher SO2 capacity due to their multiple ether groups, they could not be used to capture SO2 under industrial conditions because of the weak physical interaction. Among the functional ILs investigated, novel azolate ILs were found to have the two mole of chemical absorption capacity through two-site cooperative interactions under low partial pressure. Very recently, other kinds of multiple-site based ILs were developed, including sites on the independent cation and anion as well as those on the same anion. [Et2NEmim][Tetz] was found to be a kind of multi-functional IL that could absorb two mole of SO2 under low partial pressure through independent anion···SO2 and amine···SO2 interactions. Among the above mentioned functional ILs, the ILs based on [Tetz] and [SCN] anions were proved to be more efficient and highly reversible for the capture of SO2 under low SO2 partial pressure. The perspective for further researches on the design of functionalized ILs was also provided. Finally, some challenges in the absorption of SO2 from flue gas were indicated, which includes the high cost of ILs, the deep mechanism study of SO2 absorption, the investigations under high temperature and low SO2 partial pressure, as well as the effect of other species (such as CO2, NO x , O2, dust, and moisture) in flue gas. The development of alternative ILs that are able to achieve rapid and reversible SO2 capture in high capacity is always highly desired.

Correlation between some arterial and venous blood gas parameters in healthy newborn Martina Franca donkey foals from birth to 96 hours of age

In neonatology, blood gas analysis is a useful tool in the evaluation of the health of newborns and plays a key role in early detection of critically ill subjects. Because blood gas analysis parameters have not previously been studied in any depth in donkey foals, this study was performed on 16 healthy Martina Franca donkey foals born after an uncomplicated delivery. Arterial and venous blood samples were collected at 5 minutes and at 12, 24, 72, and 96 hours of age. Blood gas analysis was performed by a portable analyzer, measuring arterial and venous total carbon dioxide, carbon dioxide partial pressure (pCO2), oxygen partial pressure (pO2), oxygen saturation (sO2), bicarbonate, base excess (BE), pH, and lactate (LT). Lower blood pH values, pO2 and sO2, and a higher level of lactate were found at birth in comparison with subsequent sampling times. This moderate acidotic profile disappeared at 12 hours, when all the parameters became constant until the end of the study period. As expected, significant differences between arterial and venous blood gas parameters related to the oxygenation, such as pO2 and sO2, and partially carbon dioxide partial pressure were found, whereas total carbon dioxide, pH, BE, and LT were comparable in arterial and venous blood samples. For these latter parameters, the highly significant correlation between arterial and venous findings suggests that venous samples could be an acceptable alternative to the arterial sample for blood gas analysis in newborn donkey foals, when the oxygenation status of the patient is not the first goal of patient analysis.

H2S Oxidative Decomposition for the Simultaneous Production of Sulphur and Hydrogen

The reaction parameters of H2S conversion, H2 yield and SO2 selectivity obtained by thermal decomposition of H2S in presence of oxygen have been investigated at different operating conditions such as O2/H2S molar feed ratio, residence time and reaction temperature. Experimental tests allowed to find the best values of operating parameters able to assure a high H2S conversion and a good hydrogen yield, minimizing the SO2 selectivity. The increase of the O2 concentration has determined an increase of the H2S conversion and the SO2 selectivity and a slight decrease of H2 yield. The increase of the temperature in the range 700 - 1,100 °C has improved the H2S conversion and H2 yield, with a reduction of SO2 selectivity from about 30 % to 2 %. At temperature of 1,100 °C and O2/H2S = 0.2 good performances were observed in terms of the H2S conversion (58 %), H2 yield (24 %) with a lower SO2 selectivity (~2 %).

Space view of the decadal variation for typical air pollutants in the Pearl River Delta (PRD) region in China

The Pearl River Delta (PRD) is one of the most industrialized, urbanized and populated regions in China, and thus has been long suffering from severe air pollutions. Space data provide a unique perspective for investigating the atmospheric environment at a regional scale. By utilizing multiple satellite retrievals from 2005 to 2013, this study presented, for the first time, the spatial patterns and temporal trends of typical air pollutants over PRD and its vicinity. As viewed from space, aerosol optical depth (AOD), NO2 and SO2 all had their higher values at the central part of PRD, and showed clear descending gradients as moving to the outskirt of this region. As to the inter-annual variation, all these pollutants had decreasing trends in PRD during the study period, which generally agreed with the relevant in situ measurements. However, the satellite retrievals differed from ground measurements when addressing NO2 and SO2 in the vicinity of PRD. This work also provides the inter-comparison among PRD and three other metropolitan clusters in China: PRD had relatively high AOD, moderate NO2 and low SO2 levels, and it was the only region achieving the effective reduction of NO2 and SO2 during last decade. Unlike the previous three pollutants, HCHO observed by satellite showed very special patterns: it had a relatively homogeneous spatial distribution over both of PRD and its vicinity, and presented an opposite increasing trend from 2005 to 2010. Moreover, PRD had the highest HCHO level among all the metropolitan clusters, hinting a considerable contribution of biogenic origins of HCHO in PRD.

Simulation and economic evaluation of biomass gasification with sets for heating, cooling and power production

In this work, syngas was used directly as fuel source for the renewable CCHP system, which can be producted through biomass gasification process. The advantages and limitation of entrained flow gasifier are compared, followed by discussion on the key parameters that are critical for the optimum production of syngas. Gasification agent of 450 °C temperature and 30 atm pressure has been proposed as a optical solution to a entrained flow gasifier using air as gasification agent at 0.27 ER (oxygen equivalence ratio), in that it provides a syngas of 5.665 MJ/m3 LHV and up to 77% gasification efficiency. Depending on the key parameters of gasification process, the properties of syngas produced can be varied. It is thus essential to thoroughly understand the cogeneration system to identify the suitable methods for a renewable CCHP system. These process was simulated using Aspen Plus to perform the rigorous material and energy balances. The results obtained from simulation and experiment agreed well. This paper later focused on economic evaluation of the entire process, as well as the environmental benefits. The renewable CCHP system could able to attain lower CO2 and SO2 emission with total energy efficiency and gas yield of 75.43% and 2.476 m3/kg respectively.