Formation Of SO Research Articles

Effects of SO3 formation on high temperature flue gas desulphurization performance

The removal of SO2 from a synthetic flue gas using limestone sorbent was investigated. The formation of SO3 in situ was quantified and its effect on the desulphurization performance of the sorbent was determined. The transient response was measured in a bench-scale fixed-bed reactor at 700 °C, 800 °C and 900 °C, and under inert and catalytic wall conditions. Under the homogeneous gas-phase reaction conditions (inert wall effects), it was found that the breakthrough times increased as the temperature increased, indicating an increasing sorbent capacity. The SO3 molar yields under these conditions were found to remain constant at 0.24% at all temperatures. It was found that after the pickling and cleaning of the reactor vessel, the iron oxide on the exposed stainless steel reactor walls had catalytically accelerated the conversion of SO2 to SO3 as the temperature increased. Longer breakthrough times were thus obtained for SO2 removal and increased SO3 molar yields of 1.62%, 2.8% and 4.65% were obtained at each of the temperatures, respectively. The increasing SO3 molar yield had an adverse effect on the desulphurization performance of the sorbent as indicated by decreasing desulphurization ratios (0.95, 0.91 and 0.864), where the desulphurization ratio is the ratio of the actual degree of desulphurization to the apparent degree of desulphurization. It was determined that under these mild desulphurization conditions, the conversion of SO2 to SO3 influences the overall desulphurization performance of the hot-gas system, with increased effects at higher temperatures and a catalytically active reactor wall.

Numerical simulation of NO and SO2 emission dynamic characteristics during thermal start-up of CFB boiler

During the startup process of CFB boiler, problems such as wear, coking and excessive pollutant emission may occur, which pose a serious threat to the safe and environmental protection operation of the power plant. Based on the Computational Particle Fluid Dynamics (CPFD) method, numerical simulation was carried out for the thermal startup process of CFB boiler, so as to analyze the flow field change and pollutant emission dynamic characteristics during the thermal startup process of the boiler. The results show that the formation of NO and SO2 is mainly concentrated in the dense-phase zone of CFB boiler during the thermal startup process. After stable operation of the boiler, the production of NO, SO2, CO and O2 presents dynamic fluctuation. The bed height (H0) and the initial bed temperature (T0) have certain influences on the formation and distribution of NO and SO2. The research results provide theoretical basis for the actual thermal startup and operation of CFB boiler and have certain reference value.

Structure and Conductivity Correlation in NASICON Based Na3Al2P3O12 Glass: Effect of Na2SO4

Identifying the factors influencing the movement of sodium cations (Na+) in glasses accelerates the possible options of glass-based solid electrolyte materials for their applications as a promising electrolyte material in sodium-ion batteries. Nevertheless, due to the poor correlation between the structure and conductivity in glass materials, identifying the factors governing the conductivity still exists as a challenging task. Herein, we have investigated the DC-conductivity variations by correlating the structure and conductivity in sodium superionic conductor (NASICON) based Na3Al2P3O12 (NAP) glass (mol%: 37.5 P2O5—25.0 Al2O3—37.5 Na2O) due to the successive substitution of Na2SO4 for Al2O3. Structural variations have been identified using the Raman and magic-angle spinning nuclear magnetic resonance (MAS-NMR) (for 31P, 23Na, and 27Al nuclei) and conductivity measurements have been done using the impedance spectroscopy. From the ac-conductivity spectra, the correlations between mean square displacement (MSD) and dc-conductivity and between the Na+ concentration and dc-conductivity have also been evaluated. Raman spectra reveal that the increase in the Na2SO4 concentration increases the number of isolated SO42− sulfate groups that are charge compensated by the Na+ cations in the NAP glass. MAS-NMR spectra reveal that the increase in Na2SO4 concentration increases the concentration of non-bridging oxygens and further neither S-O-P nor S-O-Al bonds are formed. Impedance spectroscopy reveals that, at 373 K, the DC conductivity of the NAP glass increases with increasing the Na2SO4 up to 7.5 mol% and then decreases with the further increase. In the present study, we have shown that the mobility of sodium cations played a significant role in enhancing the ionic-conductivity. Further, we have shown that inter-ionic Coulombic interactions and the structural modification with the formation of SO42− units significantly influence the critical hopping length < R2 (tp)> of the sodium cations and consequently the mobility and the ionic conductivity. The present study clearly indicates that, based on the compositions, glass materials can also be treated as strong-electrolyte materials.

Experimental Study on RP-3 Aviation Fuel Tank Using Oxygen-Consuming Inerting Technology

Oxygen-consuming fuel tank inerting technology is a novel technology with a simple structure and a high efficiency for tank explosion suppression based on flameless catalytic combustion. To verify the feasibility of the oxygen-consuming inerting system for RP-3 aviation fuel tanks, a test bench was constructed based on a self-developed catalyst, and the system performance was studied on the ground. The results showed that both the oxygen volume fraction in the fuel tank and the mixed inert gas decreased gradually with time, and the oxygen volume fraction in the tank dropped to 12% and 9% after 11.3 and 15.3 min, respectively, which demonstrated that the oxygen-consuming inerting system for RP-3 fuel tanks was successful. In addition, the influence of key parameters on the system performance was also analyzed. The results indicated that the higher the fan flow, inlet gas temperature, and fuel temperature, the faster the oxygen volume fraction decreased. In addition, the formation of CO, NO, and SO2 was also observed during the experiment. The research results can be used as references for the application of oxygen-consuming inerting systems for RP-3 aviation fuel tanks.

A comprehensive exploration about the effects of O2, SO2 and NO on As2O3 adsorption over Cu/γ-Al2O3 SCR catalyst: A DFT study

Identifying the mechanisms by which gas components influence arsenic deposition over a SCR catalyst is an important issue to protect the catalyst from arsenic poisoning. In this work, the effects of O2, SO2, and NO on arsenic adsorption over a Cu/γ-Al2O3 catalyst were calculated via density functional theory (DFT) method. Results revealed that O2 facilitated the As2O3 retention on Cu/γ-Al2O3 surface due to the formation of adsorbed O atoms. The positive effect of SO2 on As2O3 adsorption was reflected by the formation of SO42− and HSO4−, which changed the potential field of substrate surface. Specifically, HSO4− enhanced the adsorption activities of surface atoms. However, NO3− did not show a significant impact on As2O3 adsorption when NO was introduced. From thermodynamic and adsorption selectivity analysis, the adsorption activities of different surfaces were in the order of O-Cu/γ-Al2O3 > SO42−-Cu/γ-Al2O3 > O2-Cu/γ-Al2O3 > NO3−-Cu/γ-Al2O3 > HSO4−-Cu/γ-Al2O3. However, the adsorption selectivity weakened with increasing temperature. Results from this work can help improve the arsenic resistance of SCR catalysts.

The promoting mechanism of doping Mn, Co, and Ce on gas adsorption property and anti-SO2 oxidation over γ-Fe2O3 (001) surface: A density functional theory study

To improve the deNOx and anti-poisoning performance of γ-Fe2O3 catalyst, the effects of three dopants Mn, Co, and Ce on gas adsorption and SO2 oxidation were investigated by a DFT method. Results show that NH3, NO, O2 can be adsorbed stably on the γ-Fe2O3 (001) surface to form coordinated NH3, nitrosyl, and adsorbed oxygen species, respectively. SO2 and H2O bind to Fe site on the catalyst surface by weak chemisorption. Doped Mn, Co, and Ce atoms simultaneously improve the gas adsorption performance of its own site and the surrounding Fe sites, especially for Ce doping. Furthermore, doping Mn contributes to the oxidation of SO2 to SO3, while doping Co and Ce restrains the formation of SO3, especially doping Ce, which is conducive to sulfur resistance of the catalyst. By comparison, the doping of Ce has more excellent deNOx and anti-poisoning property for the γ-Fe2O3 catalyst, which provides theoretical guidance for the selection of dopant in the subsequent experiments.

Formation of NO and SO2 in the Sintering Process of Iron Ores

Formation of NO and SO2 in the Sintering Process of Iron Ores

Density functional theory studies on ortho-position adsorption of SO3 at step sites of a CaO surface with SO2 and CO2

With the application of high-sulfur coal and oxy-fuel combustion in power plants, the formation of SO3 in flue gas has strongly enhanced. Hence, the removal of SO3 has received growing attention. Within this context, SO3 sorption using calcium-based sorbents is an interesting approach. In this study, we analyzed the steps on a CaO surface and examined their influence on the adsorption of SO3 molecules using density function theory calculations. The results indicate that steps with O and Ca atoms at the edges are the most stable terminations and also the best terminations for SO3 adsorption. SO3 molecules bind to OCaO sites by SSO3 atoms and weak bonds between Ca and OSO3 are formed. At edge sites, the adsorption energy of SO3, SO2 and CO2 shows a remarkable increase compared to that on a flat surface, whereas it decreases at the top site nearby the edge. The adsorption energy of SO3 is also affected by the OCaO that interacts with SSO3 and the Ca near the OCaO. Interestingly, the SO3 adsorption energy can increase if an SO3, SO2 or CO2 molecule previously adsorbed at a neighboring site. SO3 adsorption is more stable than SO2 and CO2 absorption on step surface and has an advantage in competitive adsorption with SO2 or CO2. The calculation results thus indicate that the formation of a step surface could be an effective method to enhance SO3 sorption on calcium-based sorbents.

Kinetics, product distribution and atmospheric implications of the gas-phase oxidation of allyl sulfides by OH radicals

Relative rate coefficients of the OH radical -initiated oxidation of allyl methyl sulfide (AMS, H2CCHCH2SCH3) and allyl ethyl sulfide (AES, H2CCHCH2SCH2CH3) have been measured at atmospheric pressure of synthetic air and 298 K: kAMS= (4.98 ± 1.42) and kAES= (6.88 ± 1.49) × 10−11 cm3 molecule−1 s−1 by means of in situ FTIR spectroscopy. In addition, the molar yields of the main reaction products of AMS with OH radicals formed in the absence and presence of nitric oxides (NOX) were determined to be the following: sulfur dioxide (95 ± 12) % and (51 ± 12) % for acrolein (50 ± 9) % and (41 ± 9) %. In the reaction of AES with OH radicals, the following molar yields were obtained: for sulfur dioxide (88 ± 13) % and (56 ± 12) % for acrolein (36 ± 9) % and (41 ± 9) %. The present results suggest that the abstraction at C3 plays an important role in the oxidation mechanism as the addition to the double bond. This work represents the first study of the OH radical interaction with AMS and AES carried out under atmospheric conditions. The atmospheric implications were discussed in terms of the atmospheric residence times of the sulfur-containing compounds studied and the products formed in the presence and absence of NOx. SO2 formation seems to be the main fate of the gas-phase allyl sulfides oxidation with significant acidifying potentials and short-chain aldehydes production like formaldehyde and acetaldehyde.

Atmospheric Fate of the CH3SOO Radical from the CH3S + O2 Equilibrium.

The atmospheric oxidation mechanisms of reduced sulfur compounds are of great importance in the biogeochemical sulfur cycle. The CH3S radical represents an important intermediate in these oxidation processes. Under atmospheric conditions, CH3S will predominantly react with O2 to form the peroxy radical CH3SOO. The formed CH3SOO has two competing unimolecular reaction pathways: isomerization to CH3SO2, which further decomposes into CH3 and SO2, or a hydrogen shift followed by HO2 loss, leading to CH2S. Previous theoretical calculations have suggested that CH2S formation should be the dominant pathway, in disagreement with existing experimental results. Our large active space multireference configuration interaction calculations agree with the experimental results that the formation of CH3 and SO2 is the dominant route and the formation of CH2S and HO2 can, at most, be a minor pathway. We support the calculations with new experiments starting from the OH + CH3SH reaction for CH3S formation under low NOx conditions and find a SO2 yield of 0.86 ± 0.18 within our reaction time of 7.9 s. Model simulations of our experiments show that the SO2 yield converges to 0.98. This combined theoretical and experimental study thus furthers the understanding of the general oxidation mechanisms of sulfur compounds in the atmosphere.

Exploring the growth and oxidation of 2D-TaS2 on Cu(111)

In this work, the growth and stability towards O2 exposure of two dimensional (2D) TaS2 on a Cu(111) substrate is investigated. Large area (∼1 cm2) crystalline 2D-TaS2 films with a metallic character are prepared on a single crystal Cu(111) substrate via a multistep approach based on physical vapor deposition. Analytical techniques such as Auger electron spectroscopy, low energy electron diffraction, and photoemission spectroscopy are used to characterize the composition, crystallinity, and electronic structure of the surface. At coverages below one monolayer equivalent (ML), misoriented TaS2 domains are formed, which are rotated up to relative to the Cu(111) crystallographic directions. The TaS2 domains misorientation decreases as the film thickness approaches 1 ML, at which the crystallographic directions of TaS2 and Cu(111) are aligned. The TaS2 film is found to grow epitaxially on Cu(111). As revealed by low energy electron diffraction in conjunction with an atomic model simulation, the (3 × 3) unit cells of TaS2 match the (4 × 4) supercell of Cu(111). Furthermore, the exposure of TaS2 to O2, does not lead to the formation of a robust tantalum oxide film, only minor amounts of stable oxides being detected on the surface. Instead, the exposure of TaS2 films to O2 leads predominantly to a reduction of the film thickness, evidenced by a decrease in the content of both Ta and S atoms of the film. This is attributed to the formation of oxide species that are unstable and mainly desorb from the surface below room temperature. Temperature programmed desorption spectroscopy confirms the formation of SO2, which desorbs from the surface between 100 and 500 K. These results provide new insights into the oxidative degradation of 2D-TaS2 on Cu(111).

Electrochemical cross-coupling reactions of sodium arenesulfinates with thiophenols and phenols

A green electrochemical oxidative cross-coupling protocol for the generation of thiosulfonates and sulfonate esters using sodium arenesulfinates and thiophenols/phenols is disclosed. The protocol involves using inorganic and non-toxic NaI as both redox catalyst and supporting electrolyte at room temperature without oxidant and base. The reactions provide good yields of products and tolerate broad substrate scope. The mechanistic studies revealed that the reactions proceed via a radical pathway for the formation of SO2–S and SO2–O bonds.

Modeling accretion shocks at the disk–envelope interface

Context.As material from an infalling protostellar envelope hits the forming disk, an accretion shock may develop which could (partially) alter the envelope material entering the disk. Observations with the Atacama Large Millimeter/submillimeter Array (ALMA) indicate that emission originating from warm SO and SO2might be good tracers of such accretion shocks.Aims.The goal of this work is to test under what shock conditions the abundances of gas-phase SO and SO2increase in an accretion shock at the disk–envelope interface.Methods.Detailed shock models including gas dynamics were computed using the Paris-Durham shock code for nonmagnetizedJ-type accretion shocks in typical inner envelope conditions. The effect of the preshock density, shock velocity, and strength of the ultraviolet (UV) radiation field on the abundance of warm SO and SO2is explored. Compared with outflows, these shocks involve higher densities (~107cm−3), lower shock velocities (~few km s−1), and large dust grains (~0.2 μm) and thus probe a different parameter space.Results.Warm gas-phase chemistry is efficient in forming SO under mostJ-type shock conditions considered. In lower-velocity (~3 km s−1) shocks, the abundance of SO is increased through subsequent reactions starting from thermally desorbed CH4toward H2CO and finally SO. In higher velocity (≳4 km s−1) shocks, both SO and SO2are formed through reactions of OH and atomic S. The strength of the UV radiation field is crucial for SO and in particular SO2formation through the photodissociation of H2O. Thermal desorption of SO and SO2ice is only relevant in high-velocity (≳5 km s−1) shocks at high densities (≳107cm−3). Both the composition in the gas phase, in particular the abundances of atomic S and O, and in ices such as H2S, CH4, SO, and SO2play a key role in the abundances of SO and SO2that are reached in the shock.Conclusions.Warm emission from SO and SO2is a possible tracer of accretion shocks at the disk–envelope interface as long as a local UV field is present. Observations with ALMA at high-angular resolution could provide further constraints given that other key species for the gas-phase formation of SO and SO2, such as H2S and H2CO, are also covered. Moreover, theJames WebbSpace Telescope will give access to other possible slow, dense shock tracers such as H2, H2O, and [S I] 25 μm.

Theoretical insights into H2S reaction mechanism over CuFe2O4 oxygen carrier

CuFe2O4 is a promising oxygen carrier because of its high reactivity and good resistance to sintering. The existence of H2S in fuel gas may lead to the poison of oxygen carrier during chemical-looping combustion. The reaction mechanism of H2S over CuFe2O4 was systematically investigated at molecular level based on the periodic slab model and density functional theory calculations. The results show that H2S reaction over CuFe2O4 includes dehydrogenation, H2O production and SO2 formation. The reaction of HS∗ → S∗ + H∗ is the rate-determining step of H2S dehydrogenation. The decomposed H atoms can react with surface O to generate H2O through overcoming an energy barrier of 158.51 kJ/mol. S∗ can be oxidized by surface O to produce SO2, and the energy barrier is 81.15 kJ/mol. The O vacancy produced from H2O desorption can affect the reaction behavior of H2S. The adsorption energies of H2S and its species increase in the presence of O vacancy, while the energy barrier for H2O production decreases to 103.37 kJ/mol. The S atom on the surface migrates and fills the O vacancy.

Impact of boiler load and limestone addition on SO3 and corrosive cold-end deposits in a coal-fired CFB boiler

The risk of cold-end corrosion caused by two different phenomena was studied: the well-known sulfuric acid-induced corrosion and corrosion caused by hygroscopic fly ash deposits. Measurements were performed in a full-scale circulating fluidized bed boiler firing bituminous coal with high contents of sulfur and chlorine. The boiler was run both with and without limestone addition to reveal the effects of limestone on corrosion. Furthermore, the impact of boiler load on corrosion and deposit composition was studied. Corrosion probe, SO3, and dew point measurements were performed up- and downstream of the electrostatic precipitator. Ash deposits were collected from the different sides of the corrosion probe and were analyzed. The formation of SO3 was low in all cases (<0.1 ppmv), which was connected to the relatively low furnace temperature in fluidized bed combustion and the efficient SO3 capturing of the fly ash and limestone. The different operational parameters of the boiler had a significant impact on deposit composition and on expected corrosion risk. At full load and without limestone addition, the chlorine of the fuel stayed as gaseous HCl, whereas no Cl was found in the deposits. However, when limestone was added, corrosion was caused by the presence of deliquescent calcium chloride. At low load operation of the boiler, ammonium chloride was formed on the cold-end deposit probe. Ammonium chloride was formed via the reaction between HCl and NH3 in the cooling flue gases. Laboratory studies with NH4Cl was further conducted to assess its corrosivity.

High temperature H2S selective oxidation on a copper-substituted hexaaluminate catalyst: A facile process for treating low concentration acid gas

H2S selective catalytic oxidation technology is a prospective way for the treatment of low concentration acid gas with simple process operation and low investment. However, undesirable results such as large formation of SO2 and catalyst deactivation inevitably occur, due to the temperature rise of fixed reaction bed caused by the exothermic reaction. Catalyst with high activity in wide operating temperature window, especially in high temperature range, is urgently needed. In this paper, a series of copper-substituted hexaaluminate catalysts (LaCux, x = 0, 0.5, 1, 1.5, 2, 2.5) were prepared and investigated for the H2S selective oxidation reaction at high temperature conditions (300-550°C). The LaCu1 catalyst exhibited excellent catalytic performance and great stability, which was attributed to the best reductive properties and proper pore structure. Besides, two facile deep processing paths were proposed to eliminate the remaining H2S and SO2 in the tail gas.

Laser induced breakdown spectroscopy for monitoring the molten phase desulfurization process of blister copper

The development of real-time monitoring sensors for pyro-metallurgical processes is an analytical challenge, mainly due to adverse environmental conditions, high spectral interferences and multiphase (molten and gas) reactions. This work demonstrates the suitability of stand-off LIBS (ST-LIBS) for real time monitoring of the desulfurization of blister copper which is carried out in molten phase. Here sulfur is removed by the formation of SO2 by supplying oxygen in molten phase. Using ST-LIBS the relative emission intensities of Cu(I) at 351.06 nm, O at 777.34 nm and S at 921.29 nm in both molten and gaseous phase were considered simultaneously during the process. This was possible only by the use high energy laser pulse over up to 270 mJ per pulse. In the case of copper, the selection of emission lines was assessed considering non-linear behavior, which is caused by self-absorption. For the first time, real time determination of sulfur in ppm range is reported by ST-LIBS using low sensitive lines from the NIR region. These results were validated with differential optical absorption spectroscopy (DOAS) as gold standard method. The analytical information obtained by LIBS can precisely determine the critical end-point of the desulfurization where the removal of sulfur is finished, and copper started to oxidize.

Thermodynamic study of NOx and SO2 formation and possible reduction during Pb waste recycling

With the increasing demand for electricity due to the increasing economic boom, there is an excessive production of emissions that natural processes cannot cope with. Fortunately, there are various technological solutions for capturing harmful substances from produced emissions. However, the European Union aims to prevent the formation of emissions in the process of industrial production itself. In order to achieve this, it is necessary to reconcile the interests of individual European Union member states by the implementation of regulations into laws, to monitor short-term and long-term changes in air quality, and also to put into practice increasingly effective methods of capturing emissions from the air. This paper offers an example of thermodynamic calculation of quantities by appropriate software in the process of recycling waste from the metallurgical industry and possibilities of technological improvement in emission reduction.

Composition of a gas and ash mixture formed during the pyrolysis and combustion of coal-water slurries containing petrochemicals

This paper presents the results of experimental research into the component composition of gases and ash residue from the combustion of a set of high-potential coal-water slurries containing petrochemicals. We have established that the use of slurry fuels provides a decrease in the CO2, CH4, SO2, and NOx concentrations as compared to those from coal combustion. The content of carbon monoxide and hydrogen in the gas environment from the combustion of slurries is higher due to the intense water evaporation. It is shown that adding biomass allows a further 5–33% reduction in the emissions of nitrogen and sulfur oxides as compared to the coal-water slurry and the composition with added waste turbine oil and a 23–68% decrease as compared to coal (per unit mass of the fuel burnt). The mechanisms and stages of CO2, SO2, and NOx formation are explained with a view to controlling gaseous anthropogenic emissions and ash buildup. The values of the relative environmental performance indicator are calculated for slurry fuels. It is shown to exceed the same indicator of bituminous coal by 28–56%.

TG-FTIR and Py-GC/MS combined with kinetic model to study the pyrolysis characteristics of electrolytic manganese residue

The manuscript used TG-FTIR, Py-GC/MS along with kinetic models to investigate the pyrolysis characteristics of electrolytic manganese residue. The possible reaction mechanism for the pyrolysis process of electrolytic manganese residue and the change rule of volatiles release characteristics during the pyrolysis were analyzed. The result shows that the pyrolysis process of electrolytic manganese residue can be divided into five processes: the dehydration of CaSO4·2H2O, the removal of ammonium salt compounds, the transformation of anhydrous CaSO4 crystal form, the decomposition of carbon-containing organic matter and the solid-phase reaction between the substances to form a new phase. According to the difference of activation energy values, the kinetic process for the pyrolysis of electrolytic manganese residue was divided into four sections. The pyrolysis reaction mechanism functions for different kinetic mechanism were the second-order phase boundary chemical reaction function: g(α) = (1-α)−1, Mampel Power law function g(α) = α1/4, 2/3-order phase boundary chemical reaction function g(α) = (1-α)-1/2 and three-dimensional diffusion function g(α) = [1-(1-α) 1/3] 1/2. The major gases released during the pyrolysis of electrolytic manganese residue were NH3, CO2 and SO2. The intermediate product of CO was unstable and participated in the reaction to promote the formation of CO2 and SO2.