Diffusion Of SO2 Research Articles

Correlation-Based Predictions of Gas Solute Diffusivity in Ionic Liquid Solvents Based on Solvent-Accessible Surface Area.

In our prior study [Olowookere, F. V.; Turner, C. H. J. Phys. Chem. B 2023, 127(42), 9144-9154], we introduced a new scaling relationship to predict gas solute diffusion at challenging conditions, focusing on CO2 and SO2 diffusion in multivalent ionic liquid (IL) solvents. This work extends our initial exploratory study into a much broader array of systems, encompassing additional solutes (N2, CH4, C2H6, C3H8, C3H8O, and H2O) and a variety of different ionic liquid species ([Bzmim3]3+, [Bzmim4]4+, [BMIM]+, [EMIM]+, [HMIM]+, [NapO2]2-, [BzO3]3-, [BF4]-, [Tf2N]-, and [PF6]-). Our study demonstrates a remarkably robust logarithmic correlation between solute diffusion and solvent accessible surface area (SA) across 20 different additional systems. We perform comprehensive analyses of the underlying molecular phenomena responsible for this correlation, including solute lifetime distributions, void space dynamics, and Voronoi tessellation, in order to elucidate a stronger mechanistic understanding of this behavior. Our findings highlight a direct link between the solvent accessible SA and the size of the void domains. Overall, our scaling approach provides an efficient and reliable approach for predicting diffusion from analyses of short simulations at higher temperatures.

Pore-Scale Study on the Effect of SO2 on Hydrate-Based CO2 Sequestration in a High-Pressure Microfluidic Chip

Summary To mitigate the effects of greenhouse gases, the sequestration of greenhouse gases such as carbon dioxide (CO2) in seafloor sediments in the form of hydrates has become a safe and efficient method. If sulfur dioxide (SO2), one of the flue gas impurities, is also sequestered, the cost of CO2 purification and sequestration can be effectively reduced. However, there is a lack of in-situ observation of how SO2 affects the nucleation and growth process of CO2 hydrates. In this study, a visual microfluidic chip combined with in-situ Raman spectroscopy was used for the first time to investigate the impact mechanism of SO2 on the nucleation and growth kinetics of CO2 hydrates in porous media. The results indicate that SO2 could promote the nucleation and growth of CO2 hydrate in the following aspects: First, the diffusion of SO2 in solution induces spontaneous convection of the solution in the pores, which could promote the nucleation of mixed hydrates. After nucleation, dissolved SO2 acts as a “seed” for hydrate formation, and the pore solution is covered with hydrate microcrystals, providing heterogeneous nucleation sites for hydrate growth in solution. During the growth stage, SO2 could induce the preferential growth of mixed hydrates within the solution and enhance the growth rate of hydrates, acting as a promoter of hydrate formation. As CO2-SO2 mixed hydrates preferentially grow in solution and grow denser, it could quickly cement the pores, which could significantly improve the stability of the reservoir and form a strong hydrate barrier in the reservoir. These findings have important theoretical value and guiding significance for the synchronous sequestration of CO2-SO2 by hydrates.

Understanding the pore size distribution of Ca(OH)2 for effective desulfurization under low-to-medium temperatures

The pore size distribution plays a crucial role in the gas-solid desulfurization reaction of Ca(OH)2, yet its impact on desulfurization performance is not fully understood, especially in low-to-medium temperature range (100–400 °C). This study examined the diffusion and adsorption characteristics of SO2 in Ca(OH)2 pores with different sizes by Monte Carlo Simulation and Molecular Dynamics Methods. The reaction kinetics of desulfurization for samples with different pore structures were analyzed based on TGA data and linear regression. It is found that the adsorption of SO2 on Ca(OH)2 was mainly induced by electrostatic interaction. Pores with the size of 5–15 nm were most favorable for SO2 adsorption, with the maximum adsorption heat of 464.83 kJ/mol at 5 nm. When the pore size increased, the diffusion of SO2 was improved, but the distribution of SO2 became more scattered, resulting in an adverse effect on the desulphurization reaction. The desulphurization process can be divided into the surface reaction controlled stage and product layer diffusion controlled stage. The desulphurization ability was primarily contributed by the reaction controlled stage, in which Ca2+ migration resistance was the least. Pore structure was a crucial factor in determining the duration of the reaction controlled stage. The presence of 15–30 nm pores was of significant importance for this stage. Yet in the diffusion controlled stage, pores size of ≥30 nm was much more important than other sizes to improve the Ca2+ diffusion. This study shows that a reasonable pore size combination facilitates the diffusion of SO2 and its reaction with Ca2+.

A facile MnSO4 surface coated NiMnFeOx catalyst with enhanced SO2 resistance for SCR reaction: A dual-protection mechanism

The SO2 resistance under low-temperature conditions remains a pivotal challenge in the industrial application of NH3-SCR catalysts. This work develops a facile and effective strategy of constructing a surface MnSO4 coating layer on catalysts in combination with Ni doping, which significantly boosts the SO2 resistance and stability of the conventional MnFeOx catalyst. Advanced characterizations including Synchrotron XAS analysis coupled with density functional theory (DFT) calculations, were utilized to further elucidate the underlying mechanism. The findings corroborate that the remarkable SO2 resistance of the MnSO4 surface-coated NiMnFeOx catalyst originates from a dual-protection mechanism. The doping of Ni effectively restricts the diffusion of SO2 within the catalyst, thereby confining sulfation to the surface of the catalyst. Subsequently, the MnSO4 coating layer provides further protection to the surface of the catalyst, inhibiting SO2 adsorption and safeguarding the active metal from poisoning. Importantly, this facile strategy can be implemented without any alterations to the catalyst preparation process, making it applicable to existing commercial catalysts, thus having outstanding industrial application potential.

Predicting Gaseous Solute Diffusion in Viscous Multivalent Ionic Liquid Solvents.

Calculating solute diffusion in dense, viscous solvents can be particularly challenging in molecular dynamics simulations due to the long time scales involved. Here, a new scaling approach is developed for predicting solute diffusion based on analyses of CO2 and SO2 diffusion in two different multivalent ionic liquid solvents. Various scaling approaches are initially evaluated, including single and separate thermostats for the solute and solvent, as well as the application of the Arrhenius relationship and the Speedy-Angell power law. A very strong logarithmic correlation is established between the solvent-accessible surface area and solute diffusion. This relationship, reflecting Danckwerts' surface renewal theory and the Vrentas-Duda free volume model, presents a valuable method for estimating diffusion behavior from short simulation trajectories at elevated temperatures. The approach may be beneficial for enhancing predictive modeling in similar challenging systems and should be more broadly evaluated.

Research on predicting the diffusion of toxic heavy gas sulfur dioxide by applying a hybrid deep learning model to real case data

Toxic heavy gas sulfur dioxide (SO2) is a specific life and environmental hazard. Predicting the diffusion of SO2 has become a research focus in fields such as environmental and safety studies. However, traditional methods, such as kinetic models, cannot balance precision and time. Thus, they do not meet the needs of emergency decision-making. Deep learning (DL) models are emerging as a highly regarded solution, providing faster and more accurate predictions of gas concentrations. To this end, this study proposes an innovative hybrid DL model, the parallel-connected convolutional neural network-gated recurrent unit (PC CNN-GRU). This model utilizes two CNNs connected in parallel to process gas release and meteorological datasets, enabling the automatic extraction of high-dimensional data features and handling of long-term temporal dependencies through the GRU. The proposed model demonstrates good performance (RMSE, MAE, and R2 of 20.1658, 10.9158, and 0.9288, respectively) with real data from the Project Prairie Grass (PPG) case. Meanwhile, to address the issue of limited availability of raw data, in this study, time series generative adversarial network (TimeGAN) are introduced for SO2 diffusion studies for the first time, and their effectiveness is verified. To enhance the practicality of the research, the contribution of drivers to SO2 diffusion is quantified through the utilization of the permutation importance (PIMP) and Sobol’ method. Additionally, the maximum safe distance downwind under various conditions is visualized based on the SO2 toxicity endpoint concentration. The results of the analyses can provide a scientific basis for relevant decisions and measures.

Development of MoS2 doping strategy for enhanced SO2 detection at room temperature

Despite significant efforts to limit the use of fossil fuels, SO2 remains a major air pollutant that adversely affects human health and the environment, especially in heavily industrialized regions of developing countries. Consequently, effective and sustainable methods of SO2 monitoring remain vital issues for detector development. However, despite decades of progress, current solutions based on resistive sensors remain limited by poor sensing performance of semiconducting materials when operated at room temperature and thus suffer from high power consumption due to heating. One solution could be to employ novel 2D semiconductor nanomaterials like MoS2, which have shown good room-temperature performance for gases such as NO2 and NH3. However, they have also shown limited response to other gases, which, on the other hand, can be improved by substitutional doping. Consequently, this work investigates, employing density functional theory, the doping of MoS2 with Si, P, Cl, Ge, and Se to improve its SO2 sensing capability. The results show that P, Cl, and P+Cl doping facilitates all desired effects with molecule-sheet charge transfers enhanced by over 300%, and moderate binding energies that enable effective surface diffusion of SO2 at 300 K.

A theoretical model of sulfuration depth of concrete based on SO2 reaction and mass balance

Industrial production emits a large amount of SO2, and the alkaline environment of pore solution of concrete is destroyed by the reaction of SO2 and Ca(OH)2. This process, called sulfuration of concrete, decreases the pore-solution pH and causes the damage of concrete cover and corrosion of rebar. In this paper, the sulfuration reaction process of concrete is presented, and the mass balance equations of SO2 and sulfurable substances are established. Some important parameters are discussed in the mathematical model. The formation rates, content and sulfuration rates of sulfurable substances, the consumption rate of SO2, as well as the porosity and pore saturation of concrete are analysed. A calculation method of SO2 diffusion coefficient is proposed. The initial conditions and boundary conditions of the model are determined, and the prediction model of sulfuration depth of concrete is obtained by using the dimensionless method. The accuracy of the model of concrete sulfuration depth is verified by comparing the calculated results and experimental results obtained from previous studies.

Determination of Sulfur Dioxide Diffusion Coefficients in Hydrogen, Helium, and Nitrogen by Reversed-Flow Inverse Gas Chromatography

Diffusion coefficients of sulfur dioxide in hydrogen, helium, and nitrogen were determined by reversed-flow gas chromatography. Experiments were performed at temperatures ranging from 323.3 to 573.3 K and reduced at 101.3 kPa. The precision of the method is 96.6%, while its accuracy is 95.5%. Comparison with values predicted by Fuller–Schettler–Giddings and Huang equations indicates small deviations: the Chen–Otmer equation is successful only for the SO2–N2 system. The temperature exponents of SO2 diffusion are as follows: 1.77, 1.71, and 1.75 in H2, He, and N2, respectively. Comparisons with available experimental values for the SO2–H2 and SO2–N2 systems showed small average deviations: 5.7 and 1.3%, respectively.

Energy Conservation Optimization and Numerical Simulation of Urban Green Space Landscape Pattern

In order to alleviate the urban heat island effect, absorb harmful gases, reduce temperature, and increase humidity, a method of energy conservation optimization and numerical simulation of urban green space landscape pattern is proposed. Based on the theory of landscape ecology, green wedge, green belt, green road, park, and other types of green space with different ecological functions are designed in Shenyang, and an optimization scheme of urban green space network spatial structure of “four belts, three rings, seven wedges, and network connection” is formed. Combined with remote sensing (RS) and geographic information system (GIS) spatial analysis technology, the atmospheric environment effect under the influence of green space landscape optimization pattern in summer based on computational fluid dynamics (CFD) numerical simulation technology is analyzed, and the corresponding optimization strategies of urban green space planning are put forward. The simulation results show that in the bottom wind speed field of 1.5 m, the area ratio of 0∼0.375 m/s wind speed is 15.87%, and the area ratio of 2.625∼3 m/s wind speed is 32.06%. In the bottom concentration field of 1.5 m, the spatial diffusion capacity of SO2 pollutants is enhanced, and the concentration of pollutants is relatively low. The area ratio of SO2 concentration is 10.06% in the range of 0.1292∼0.1551 mg/m3, and the area ratio of SO2 concentration is 68.08% in the range of 0∼0.05169 mg/m3. It is concluded that the spatial diffusion of wind speed, SO2, and temperature is closely related to the urban spatial layout. The optimal spatial layout of urban green space can effectively alleviate the urban heat island effect, promote the spatial diffusion of SO2, and better form the urban ventilation corridor. The research on atmospheric environmental effects of urban green space based on CFD can effectively simulate and evaluate the optimization measures and conceptual design of urban green space system planning, and also provide new ideas for the quantitative planning of urban green space system.

Separation of SO2 and NO2 with the Zeolite Membrane: Molecular Simulation Insights into the Advantageous NO2 Dimerization Effect.

NO2 and SO2, as valuable chemical feedstock, are worth being recycled from flue gases. The separation of NO2 and SO2 is a key process step to enable practical deployment. This work proposes SO2 separation from NO2 using chabazite zeolite (SSZ-13) membranes and provides insights into the feasibility and advantages of this process using molecular simulation. Grand canonical ensemble Monte Carlo and equilibrium molecular dynamics methods were respectively adopted to simulate the adsorption equilibria and diffusion of SO2, NO2, and N2O4 on SSZ-13 at varying Si/Al (1, 5, 11, 71, +∞), temperatures (248-348 K), and pressures (0-100 kPa). The adsorption capacity and affinity (SO2 > N2O4 > NO2) demonstrated strong competitive adsorption of SO2 based on dual-site interactions and significant reduction in NO2 adsorption due to dimerization in the ternary gas mixture. The simulated order of diffusivity (NO2 > SO2 > N2O4) on SSZ-13 demonstrated rapid transport of NO2, strong temperature dependence of SO2 diffusion, and the impermeability of SSZ-13 to N2O4. The membrane permeability of each component was simulated, rendering a SO2/NO2 membrane separation factor of 26.34 which is much higher than adsorption equilibrium (6.9) and kinetic (2.2) counterparts. The key role of NO2-N2O4 dimerization in molecular sieving of SO2 from NO2 was addressed, providing a facile membrane separation strategy at room temperature.

Remote detection sulfur content in fuel oil used by ships in emission control areas: A case study of the Yantian model in Shenzhen

A method is proposed for remotely detecting sulfur content in fuel oil used by ships in emission control areas (ECAs) based on the direct collection of SO2 emission data from the plume of the ship and numerical simulation models. Assuming a ship in the ECA uses fuel oil with compliance fuel sulfur content (FSC), activity-based ship emission assessment model is firstly utilized to calculate the SO2 concentration emitted from the ship. Numerical simulation models are then used to estimate the theoretical SO2 diffusion concentration at the location of the monitoring equipment. The observed SO2 concentration at the same time can then be integrated to estimate the FSC of the ship. A sample of eleven ships was selected to verify the proposed method in Yantian port, Shenzhen, China in June 2018. The result illustrates that the method can remotely detect ships using fuel oil with the FSC greater than 0.146%m/m in the ECAs, the relative error is 46%.

Kinetics and thermodynamics of SO2 adsorption on metal-loaded multiwalled carbon nanotubes

Abstract To investigate the adsorption kinetics and thermodynamic adsorption mechanism and laws of dry flue gas desulfurization, we prepared a new adsorbent by loading Cr, Cu, and Zn on TiO2-loaded multiwalled carbon nanotubes. Desulfurization experiments were also carried out. In this study, three kinds of samples were used for simulation and diffusion processes in the dynamic adsorption of different SO2 volume fractions in flue gas and thermodynamic model analysis of different temperatures in flue gas. Results show that the diffusion coefficient of SO2 in three kinds of samples ranges from 10−16 to 10−14 m2 s−1, and the diffusion may be dominated by configuration diffusion. The intraparticle diffusion model predicts that the performance improves with an increase in the SO2 volume fraction and a shift of adsorption time. This finding indicates that an increase in SO2 volume fraction and a change in adsorption time increase the Kundsen diffusion specific gravity and decrease the configuration diffusion specific gravity, thereby increasing the SO2 diffusion resistance, which becomes faster than the activation energy barrier resistance in the catalytic oxidation reaction. Thus, the diffusion resistance specific gravity increases in the total resistance of the diffusion reaction. One possible mechanism of the adsorption process is the transition to surface reaction control at the early stage of adsorption to joint control of late diffusion and surface reactions. Adsorption thermodynamics studies show that SO2 adsorption by three adsorbents is a spontaneous, exothermic, and entropic reduction process, and the increase in temperature is inconducive for SO2 adsorption in three samples.

Comprehensive study of the dynamic interaction between SO2 and acetaldehyde during alcoholic fermentation

In this work, we focused on the effect of the initial content of SO2 in synthetic grape juice on yeast metabolism linked to the production of acetaldehyde. Lengthening of the lag phase duration was observed with an increase in the initial SO2 content. Nevertheless, an interesting finding was a threshold value of an initial SO2 content of 30 mg L−1 in the juice led to equilibrium between intracellular SO2 diffusion and SO2 production from the sulfate pool by yeast. The ratios of free and bound acetaldehydes were measured during fermentation, and the maximum accumulation of free acetaldehyde was observed when SO2 concentration equilibrium between diffusion and production was reached in the fermenting juice. Moreover, it was observed that SO2 addition resulted in significant changes in the synthesis of aroma compounds. Production of volatile molecules related to sulfur metabolism (methionol) was changed. But, more surprisingly, synthesis of some volatile carbon compounds (diacetyl, isoamyl alcohol, isobutyl alcohol, phenyl ethanol and their corresponding esters) was also altered because of major disruptions in the NADPH/NADP+ redox equilibrium. Finally, we demonstrated that acetaldehyde bound to SO2 could not be metabolized by the yeast during the time course of fermentation and that only free acetaldehyde could impact metabolism.

Promoting Effect of the Core-Shell Structure of MnO2@TiO2 Nanorods on SO2 Resistance in Hg0 Removal Process

Sorbent of αMnO2 nanorods coating TiO2 shell (denoted as αMnO2-NR@TiO2) was prepared to investigate the elemental mercury (Hg0) removal performance in the presence of SO2. Due the core-shell structure, αMnO2-NR@TiO2 has a better SO2 resistance when compared to αMnO2 nanorods (denoted as αMnO2-NR). Kinetic studies have shown that both the sorption rates of αMnO2-NR and αMnO2-NR@TiO2, which can be described by pseudo second-order models and SO2 treatment, did not change the kinetic models for both the two catalysts. In contrast, X-ray photoelectron spectroscopy (XPS) results showed that, after reaction in the presence of SO2, S concentration on αMnO2-NR@TiO2 surface is lower than on αMnO2-NR surface, which demonstrated that TiO2 shell could effectively inhibit the SO2 diffusion onto MnO2 surface. Thermogravimetry-differential thermosgravimetry (TG-DTG) results further pointed that SO2 mainly react with TiO2 forming Ti(SO4)O in αMnO2-NR@TiO2, which will protect Mn from being deactivated by SO2. These results were the reason for the better SO2 resistance of αMnO2-NR@TiO2.

Flue Gas Desulphurization in Circulating Fluidized Beds

Sulphur dioxide (SO2) is mostly emitted from coal-fueled power plants, from waste incineration, from sulphuric acid manufacturing, from clay brick plants and from treating nonferrous metals. The emission of SO2 needs to be abated. Both wet scrubbing (absorption) and dry or semi-dry (reaction) systems are used. In the dry process, both bubbling and circulating fluidized beds (BFB, CFB) can be used as contactor. Experimental results demonstrate a SO2-removal efficiency in excess of 94% in a CFB application. A general model of the heterogeneous reaction is proposed, combining the external diffusion of SO2 across the gas film, the internal diffusion of SO2 in the porous particles and the reaction as such (irreversible, 1st order). For the reaction of SO2 with a fine particulate reactant, the reaction rate constant and the relevant contact time are the dominant parameters. Application of the model equations reveals that the circulating fluidized bed is the most appropriate technique, where the high solid to gas ratio guarantees a high conversion in a short reaction time. For the CFB operation, the required gas contact time in a CFB at given superficial gas velocities and solids circulation rates will determine the SO2 removal rate.

Loading-Dependent Diffusion of SO2 in 13X and 5A Using Molecular Dynamics: Effects of Extraframework Ions and Topology

In the present study, the effects of loading, topology, and extraframework ions on SO2 diffusion in zeolites 13X and 5A were investigated using molecular dynamics simulation. The study was performe...

Health Risk of Living near a Coal Electric Power Plant: A Residential Cohort Study in North-Western Italy

In North-Western Italy, an Electric Power Plant (EPP) has been active since the early 1970s. In 2014, two production sections fed by coal were seized by the Prosecutor’s Office, while a section powered by natural gas is still functioning.To evaluate the association between exposures of residents in an area affected by EPP’s emissions and the risk of hospitalization and mortality a population-based cohort study was conducted (follow-up 2001-2013, 1,418,000 person-years).Lympho-hematopoietic and lung cancers, nervous system, cardiovascular and respiratory diseases were analysed.The diffusion of SO2 and NOx was estimated for the main sources of pollution (EPP, other industries, roads, port areas and urban heating) using the MOLOCH-ABLE-ADMS model. Modelled concentrations of SO2 were used as proxi of residential exposure to air pollution of EPP (SO2-EPP); NOx was used as proxi of Multi-Source Model including all sources of pollution (NOx-MSM).For males (M) and females (F) Hazard Rate Ratios (HRR) adjusted by age, socio-economic deprivation and NOx-MSM were computed according to quartiles of SO2-EPP concentrations. Linear Trend of HRR was performed (THRR).Mortality analysis showed increased risk for all cancers [THRR-M 1.15 95%CI (1.11-1.19); THRR-F 1.10 95%CI (1.11-1.19)], lympho-hematopoietic cancers [M 1.30 (1.14-1.48); F 1.17 (1.01-1.35)], nervous system [M 1.10 (1.00-1.22); F 1.12 (1.02-1.22)], cardiovascular [M 1.11 (1.07-1.16); F 1.16 (1.12-1.20)], and respiratory diseases [M 1.23 (1.13-1.33); F 1.17 (1.07-1.27)]. Results of hospitalization analysis were largely consistent with those of mortality analysis.The risk excesses associated to exposures attributed to the coal plant have been obtained for mortality or hospitalization causes for which the evidence of association with atmospheric emissions is persuasive.The results reinforce the knowledge on the dangers of the use of coal for energy production and the consequent indication to decarbonise to protect health.

Numerical simulation on circulation flow and mass transfer inside atmospheric water drops

When a water droplet moves in atmosphere with pollutant, internal circulation is formed due to surface shear stress. This enhances internal mass transfer greatly, and improves the spray droplet SO2 absorption. In this paper, the internal circulation and diffusion of SO2 in a water droplet were numerically studied. The distribution of tangential velocity at the interface and the effect of interior circulation on sulfur dioxide transfer are analyzed under different Reynolds numbers. The numerical results indicate that there are two symmetrical vortexes inside the droplet when there is a relative motion between gas and liquid phase. The distance between the vortex core and the droplet center is around 2/3Rd, and the vortex velocity increases with the Reynolds numbers. The study shows sulfur dioxide absorption by the droplet is controlled by two mechanisms, which are (1) the radial diffusion due to concentration gradient and (2) mass transport induced by internal circulation. The characteristic times of radial diffusion and vortex formation are compared. The comparison indicates that the internal circulation dominates sulfur dioxide mass transfer inside the water droplet. The internal circulation influences the sulfur dioxide mass transfer greatly with the increase of Reynolds number. On the other hand, the effect of deformation rate on mass transfer is insignificant because of the characteristic time areofthesameorder with the same Reynolds number.

Kinetics study of platinum and base metals precipitation in gas\u2013liquid chloride system

The use of dissolved sulphur from gaseous phase was tested for its ability to precipitate platinum ions in chloride system with alterations in the parameters such as metal ion concentration, hydrochloric acid concentration, pressure and temperature. The precipitation process was analysed on the basis of mass transfer coefficient, diffusivity models and also by absorption kinetic models. The maximum physical and reactive absorption capacity for sulphur dioxide was found to be 0.015 and 0.018 mol/L, respectively, at 298.15 K and 1.125 bars in a short contact time of 10 min. Based on the sulphur dioxide solubility data in gas–liquid system for both physical and reactive absorption conditions, the introduction of sulphur atoms in the chloride system was achieved. The mass transfer coefficients obtained for all metal ions were in the range 0.10–0.26 min−1, while the diffusivity of SO2 at different temperatures and pressures was found to be in the range (2.36–3.43) × 10−9 and (1.36–2.22) × 10−9 m2s−1, respectively. Thermodynamic parameters such as the changes in Gibbs free energy, enthalpy and entropy were also evaluated. The results indicated that the precipitation of platinum and base metals in gas–liquid (G–L) chloride system was an endothermic process.