SO2 Mole Fraction Research Articles

Computational Particle Fluid Dynamics Simulation on Combustion Characteristics of Blended Fuels of Coal, Biomass, and Oil Sludge in a 130 t h−1 Circulating Fluidized Bed Boiler

In this study, the co-combustion of coal and biomass, and the tri-combustion of coal, biomass, and oil sludge in a 130 t h−1 circulating fluidized bed (CFB) boiler are investigated via the computational particle fluid dynamics (CPFD) approach. Furthermore, the effect of biomass feeding position is also comprehensively evaluated. The results show that for the co-combustion of coal and biomass, the O2 mole fraction at the furnace outlet rises from 0.0541 to 0.0640 as the biomass blending ratio enhances from 40% to 100%, while the CO2 mole fraction reduces from 0.1357 to 0.1267. The mole fraction of NOx and SO2 at the furnace outlet decreases from 4.5867 × 10−5 to 3.9096 × 10−5 and 2.8253 × 10−4 to 4.6635 × 10−5, respectively. For the tri-combustion of three fuels, the average NOx mole fraction initially grows quickly and then declines gradually, ranging from 4.1173 × 10−5 to 4.2556 × 10−5. The mole fraction of SO2 at the furnace outlet increases from 3.5176 × 10−4 to 4.7043 × 10−4 when the ratio of oil sludge rises from 10% to 20%. The uniformity of temperature and gas components distribution is “new inlet > secondary air inlet > feed inlet”. As for the three inlet positions, the mole fractions of NOx at the furnace outlet are between 3.9096 × 10−5 and 5.1537 × 10−5, while those for SO2 are between 2.5978 × 10−4 and 2.5278 × 10−4.

An intelligent sensing system for estimation of efficiency of carbon-capturing unit in a cement plant

In this study, an artificial intelligence-based framework was developed to monitor the efficiency of the carbon capture unit, i.e., the Sour Compression Unit (SCU) and a cryogenic unit, in a cement manufacturing plant. Initially, an Aspen Plus-based model of the SCU and the cryogenic unit was developed. The process model was then transformed into dynamic mode through the interfacing of MATLAB and Excel with Aspen Plus to capture real-time process behavior. Five hundred fifty data samples were generated by varying the process conditions, i.e., inlet water flow rate, temperature, pressure, etc. The dataset was then used to develop ensemble models. Output compositions of the models were CO2, SO2, and NO. The ensemble models were used as surrogates in Sobol and Fourier Amplitude Sensitivity Test (FAST) frameworks to find the most sensitive process conditions that affect the efficiency of the process. The correlation coefficients based on the ensemble models for estimation of the composition of CO2, SO2, and NO, were 0.9888, 0.9663, and 0.9970, respectively. Based on the sensitivity analysis, the inlet flue gas temperature and pressure were the dominant variables that affect the mole fraction of SO2 and NO in the flue gas. Besides, the CO2 recovery was found heavily dependent on temperature of the flash tanks. The proposed framework was highly accurate and will provide a base for real-time implementation of the concept of smart factory in cement manufacturing plants.

Experimental study and parametric analysis of SO2 capture in limestone fixed bed reactor

AbstractBACKGROUNDThe use of absorbents, based on calcium, for the reduction of sulfur dioxide (SO2) emissions from power plants has been studied for the last 90 years. The present work is part of a research project, which aims at the development of a fixed and a moving bed limestone filter. A filter is placed after the burning, in order to capture SO2 from the flue gases of pulverized lignite combustors. An experimental study and a parametric analysis in a limestone and lignite fixed bed reactor for SO2 capture were conducted in previous works.RESULTSThis work studies experimentally the SO2 capture by analyzing the following parameters: inlet mole fraction of SO2, inlet mole fraction of O2, volumetric flow rate, average temperature in bed, type of calcium carbonate (CaCO3) and length of the solid bed. Under specific circumstances, conversion of SO2 values were found to be greater than 0.99 in the gas outlet for more than 110 min.CONCLUSIONUseful conclusions are drawn regarding the behavior of a fixed bed reactor in different conditions. The results highlight the importance of technological interest in the dry process for SO2 capture. © 2019 Society of Chemical Industry

Insights into Sulfur Uptake by Solid Sorbents from Fossil Fuels and Biomass: Revisiting C–H–O Ternary Diagrams

Sulfur, omnipresent in fossil fuels and biomass, causes substantial industrial challenges and significant environmental harm when released to the atmosphere. Efficient and cost-effective integration of sulfur removal into high-temperature industrial processes calls for temperature compatible strategies, and solid sorbents offer the most promising solution. This article presents C–H–O ternary diagrams as visual tools for fundamental evaluation of potential sulfur uptake capacity of solid sorbents. The findings of this study are based on thermodynamic analyses and highlight how the C/H/O ratio of the fuel feedstock as well as the gasification or oxidation agent affect sulfur uptake capacity of the sorbents. The thermodynamic effect of changing temperature (T = 1000–1400 K) and pressure (P = 1–10 atm) on sorbent sulfur uptake is also explored. In this study, Ca- and Sr-based sorbents are investigated, but C–H–O ternary diagrams could be calculated for any other potential solid sorbent. Important thermodynamic insights are drawn from the C–H–O ternary equilibria. Importantly, the initial sulfur content of the fuel does not affect the thermodynamic limit of the sorbent, which is primarily a function of the overall C/H/O ratio of the fuel + gasification or oxidation agent. Under reducing conditions, the total gas-phase sulfur concentration depends strongly on the water vapor partial pressure. Moreover, operating at stoichiometric oxygen conditions results in poor sorbent sulfur uptake with a rapid rise in SO2 mole fraction. The article also offers important insights to predict the most favorable conditions for the use of solid sorbents that can mitigate anode deactivation in solid oxide-based carbon fuel cells.

Numerical study of the burner parameters on the thermal field in a sulfur recovery unit thermal reactor

A sulfur recovery unit (SRU) thermal reactor is the most important equipment in a sulfur plant and is negatively affected by high temperature operations. In this paper, the effect of burner parameters, including the clearance of the acid gas tip and the inlet air swirler angle, on the thermal field in a SRU thermal reactor are investigated numerically, with the aim to reduce the high temperature inside the thermal reactor and to ensure an acceptable sulfur recovery. The simulation results show that the burner with a smaller clearance of the acid gas tip produces a lower temperature, a lower exit SO2 mole fraction and higher exit S2 and H2S mole fractions. Among the clearancs of the acid gas tip investigated, the horizontal clearance of 152.4mm and vertical clearance of 240mm yield the lowest temperature, exit SO2 mole fraction and highest exit S2, H2S mole fractions. The burner with a smaller inlet air swirler angle produces a higher temperature, a higher exit SO2 mole fraction and lower exit S2 and H2S mole fractions. Among the swirler angles investigated, 60° yields the lowest temperature, exit SO2 mole fraction and highest exit S2 , H2S mole fractions.

Chemical Mass Transfer Mechanism and Characteristics of Flue Gas Desulfurization of Basic Aluminum Sulfate by Bubbles

Flue gas desulfurization (FGD) technology with SO2 recyclable regeneration has been increasingly used for basic aluminum sulfate (aluminum base); in this process, chemical reaction and physical mass transfer synergistically affect desulfurization. In this study, experiments and ANSYS numerical simulation were performed to determine the multicomponent continuity equation, gas-phase volume overall mass transfer coefficient (KGae), and chemical mass transfer complex factor (F) by analyzing the reaction kinetics and using two-film theory. The chemical reaction rate (r) was calculated using the consumption rates of SO2 and active Al2O3, and KGae was obtained using flue gas apparent velocity and SO2 mole fraction. The effect of different factors on the chemical mass transfer of aluminum base FGD was then determined. Results showed that both r and dynamic field of gas–liquid two-phase flow affected the mass transfer capacity and desulfurization effect of the aluminum base. The inlet SO2 concentration exhibited a greater influence on KGae and F than the concentration of the absorption solution. Chemical mass transfer originated at the phase interface, and the reaction mainly occurred in the liquid-phase boundary film. Mass transfer resistance was mainly concentrated in the gas-phase boundary film. The aeration rate affected bubble formation, diffusion morphology, and gas–liquid contact time. Increasing the number of small bubbles and preventing coalescence improved the desulfurization efficiency. Moreover, KGae increased linearly with the increasing aeration rate (0.05–0.15 m/s), and F remained stable at a high level (about 0.05). The mass transfer capacity was mainly controlled by aeration rate, and the comprehensive effect of aluminum base FGD was mainly controlled by liquid-phase mass transfer conditions caused by the chemical reactions. Under the condition with 12.5% absorption solution and 0.05 m/s aeration rate, KGae was only 2.346 × 10–6 kmol/(s·m3·kPa). Furthermore, KGae increased rapidly with increasing concentration of absorption solution, whereas F decreased rapidly to the minimum value of 0.03443 with increasing aeration rate (0.15–0.2 m/s) under the conditions of low absorption solution concentration. The mass transfer capacity and comprehensive effect of aluminum base desulfurization were controlled by both physical mass transfer conditions due to the aeration rate and the liquid-phase mass transfer conditions caused by chemical reactions.

Xylene and H2S destruction in high temperature flames under Claus condition

Abstract Experimental results on the destruction of H2S and xylene mixtures in H2/O2–N2 flames, at an equivalence ratio of three (Claus condition) are presented. The combustion generated products, including excited radical species were analyzed using flame emission spectroscopy and online gas chromatography (GC). The results showed the oxidation of H2S and H2 that resulted in the formation of high mole fraction of SO2. The formed SO2 further decomposed due to the formation of S2 and CS2 in the reactor. This reveals the possible interaction between sulfurous and hydrocarbon radicals. The examination of emission spectra of excited species between 280 nm and 490 nm showed C2∗ and C3∗ swan bands, CHO∗ and CH∗ bands and H∗ (Balmer band series). The results also showed bands of SO, SH, S2∗, CS2∗ and SO2∗. The continuum of SO2 afterglow was also observed in the flame. These results provide insight on the reaction chemistry associated with the destruction of xylene and H2S. They are also of significant interest to operators and designers of sulfur plants, as well as related policy-makers. The results show the formation of value added chemicals, such as methane that can also be recovered from acid gases.

Dissociation Conditions and Raman Spectra of CO2 + SO2 and CO2 + H2S Hydrates

To further define the information needed for CO2 gas sequestration and storage in the presence of impurities, the stability of hydrates made from CO2 + SO2 and CO2 + H2S mixtures was measured by an isochoric dissociation method. The hydrates were characterized with powder X-ray diffraction, confirming that CO2 + SO2 formed a structure I hydrate. The Raman spectra of CO2 + SO2 and CO2 + H2S hydrates were also measured along with those of THF + CO2 + SO2 and THF + CO2 + H2S hydrates to observe and assign the Raman peaks of SO2 or H2S in the small cages. It was found the SO2 Raman peaks are at 1147.1 and 1155.4 cm–1 in large and small cages, respectively; the H2S Raman peaks are at 2594.0 and 2603.0 cm–1 in large and small cages, respectively. At the equilibrium points established, the composition of the released gas mixture was analyzed by gas chromatography. Measurements for gas pressures (ranging from 0.72 to 3.59 MPa) and gas compositions (ranging from 0.04% to 7.63%, mole fraction of SO2 or H2S) at spec...

Effect of benzene on product evolution in a H 2 S/O 2 flame under Claus condition

Experimental results are presented on the role of benzene addition to H2S combustion at an equivalence ratio of three with respect to H2S (Claus condition) and complete combustion of benzene. The results are reported with 0.3%, 0.5% and 1% benzene addition to H2S/O2 flame. Combustion of H2S and benzene mixtures is of practical value for sulfur recovery during combustion of acid gases. The results showed that H2S combustion caused H2S to decompose to a minimum mole fraction with high conversion of H2S while the SO2 mole fraction reached a maximum value. Addition of benzene decreased the conversion of H2S with reduced mole fraction of SO2 in the reactor to subsequently reduce the formation of elemental sulfur. Benzene also caused significant production of H2, CO and COS formation along with faster decomposition of the formed SO2. Presence of benzene, even in trace amounts, in acid gas hinders sulfur conversion in a Claus reactor and increases emission of unwanted sulfur bearing compounds. Increased hydrogen production with benzene offers potential value for hydrogen recovery under certain conditions.

Xylene addition effects to H2S combustion under Claus condition

Experimental results are presented on the combustion of H2S and mixtures of H2S and xylene at an equivalence ratio of three (Claus condition). The H2S mole fraction decreased along longitudinal central axis of the reactor to a minimum value. The SO2 mole fraction increased to a maximum value, which subsequently decomposed due to the formation of elemental sulfur, which is favorable under Claus condition. In contrast, mixtures of H2S and trace amounts of xylene (0.5%, 1% and 2%) favored the formation of H2 and increased the amounts of H2S at reactor exit. Xylene addition reduced the maximum mole fraction of SO2, and resulted to the formation of CH4 and CO. The formed SO2 decomposed faster to yield COS and CS2 from its reaction with CH4 and CO. The formation of CH4, CO, COS and CS2 poses severe impact on sulfur capture efficiency from acid gases. These results reveal a direct impact on the Claus reactor performance with trace amount of xylene present in H2S thermal processing.

Molecular Dynamics Simulations of Acidic Gases at Interface of Quaternary Ammonium Ionic Liquids

Thermodynamics, structure, and dynamics of CO2 and SO2 absorption by ionic liquids based on the bis(trifluoromethylsulfonyl)-imide anion, [NTf2]−, and quaternary ammonium cations have been investigated by molecular dynamics (MD) simulations. The effect of ether-functionalized chains of different lengths in the ammonium cations is emphasized. Oxygen atoms of ether functions in the cation compete with oxygen atoms of anions for interactions with gas molecules. The mole fraction of SO2 is larger than CO2 in a given ionic liquid. The calculation of Gibbs free energy of solvation and profiles of potential of mean force across the gas–liquid interface provide a physical picture consistent with structural effects of gas absorption. The potential of mean force for the gas molecules at interface exhibits a minimum, which is about twice deeper for SO2 than CO2, with corresponding effect on residence times of gas molecules in different layers across the interface toward the bulk.

Experimental Investigation on Multiphase Bunsen Reaction in the Thermochemical Sulfur–Iodine Cycle

The effects of SO2 flow rate, SO2 mole fraction, iodine content and water content on the Bunsen reaction were experimentally studied for the thermochemical iodine–sulfur cycle for hydrogen production. One multistage reaction mechanism on the Bunsen reaction has been hypothesized, considering the kinetic characteristics. The appearance of a liquid–liquid equilibrium (LLE) phase separation was in the range of 20–40 min in the apparatus we chose. An increase in iodine content and a decrease in water content improved LLE separation characteristics to the H2SO4 phase and HIx phase. The H2S formation side reaction easily occurred with the increase in water content and decrease in iodine content. The optimal operating condition that the inlet SO2 mole fraction exceeds 0.12 coupled with initial I2/H2O molar ratio exceeding 0.284 has been proposed based on the experimental results, for the criteria of improving the separation characteristics and preventing side reactions.

Research on sulfur recovery from the byproducts of magnesia wet flue gas desulfurization

To recycle sulfur from byproducts of magnesia wet flue gas desulfurization, the authors conducted an experimental study and computational analysis on the factors influencing the SO2 mole fraction in the calciner gas by an industrial demonstration unit. With a sulfur content of 1.65% in coal and a generating capacity of 300 MW of power plant, the economics of the renewable magnesium oxide desulfurization technology was compared to that of limestone–gypsum desulfurization technology. The results show that the decomposition reaction of byproducts mainly occurred in the lower zone of the furnace. When the excess air coefficient was 1.05 and the magnesium sulfite content in the byproducts was 60%, the SO2 mole fraction in the calciner gas was 10.5%. Decreasing the excess air coefficient can improve the SO2 mole fraction in the calciner gas. When the moisture content in the byproducts was 15%, the SO2 mole fraction reached 9.2%. The calciner exit gas temperature should be controlled at 1253.5 K or below. Adopting oxygen-enriched combustion, the oxygen content in air should be controlled to 31%. The magnesium oxide desulfurization renewable technology was found to be more economic.

Role of toluene in hydrogen sulfide combustion under Claus condition

Experimental investigations on the effect of different amounts of toluene addition to H2S combustion in oxygen under Claus condition (Φ=3) are presented. Three toluene concentrations of 0.5%, 1% and 5% in H2S are presented and compared with the baseline case of 100% H2S oxygen combustion. Temperature data showed that addition of toluene to H2S gas stream increases the flame temperature because of large heating value associated with toluene. Addition of toluene resulted in the production of H2, which increased with increase in the amounts of toluene addition. Furthermore, increased addition of toluene concentration increased the asymptotic minimum value of hydrogen sulfide due to oxidation competition between the formed H2 and H2S. The results also showed that the presence of CO triggers the formation of COS with toluene addition due to reaction of CO with SO2. The results showed that SO2 mole fraction increased to a maximum value then decayed with distance along the reactor. Addition of toluene increased the rate of SO2 decay. These results have direct impact on sulfur capture in the Claus reactor and its performance.

Effect of oxygen enrichment on acid gas combustion in hydrogen/air flames under claus conditions

Results are presented to examine the combustion of acid gas (H2S and CO2) in hydrogen-fueled flames using a mixture of oxygen and nitrogen under Claus conditions (Φ=3). Specifically the effect of oxygen enrichment in the above flames is examined. The compositions of acid gas examined are100% H2S and 50% H2S/50% CO2 with different percentages of oxygen enrichment (0%, 19.3% and 69.3%) in the oxygen/nitrogen mixtures. The results revealed that combustion of acid gas formed SO2 wherein the mole fraction of SO2 increased to an asymptotic value at all the oxygen concentrations examined. In addition, increase in oxygen enrichment of the air resulted in increased amounts of SO2 rather than the formation of more desirable elemental sulfur. In case of 50% H2S/50% CO2 acid gas, carbon monoxide mole fraction increased with oxygen enrichment which is an indicator to the availability of additional amounts of oxygen into the reaction pool. This gas mixture resulted in the formation of other sulfurous–carbonaceous compounds (COS and CS2) due to the presence of carbon monoxide. The results showed that the rate of COS formation increased with oxygen enrichment due to the availability of higher amounts of CO while that of CS2 reduced. The global reactions responsible for this observed phenomenon are presented.

Effect of CO2 and N2 concentration in acid gas stream on H2S combustion

The Effect of the presence of nitrogen and carbon dioxide in H2S acid gas stream is investigated. Concentrations of up to 30% of N2 or CO2 in H2S stream have been examined. All cases were compared with the baseline case of 100% H2S acid gas stream. Temperature measurements showed that injection of CO2 or N2 in the H2S stream decreases the flame temperature. However, injection of CO2 resulted in temperature increase downstream. Increase of carbon dioxide in the acid gas stream increased SO2 mole fraction in the byproducts. In addition, the increase of CO2 decreased the asymptotic value of H2S at downstream locations. Furthermore, the presence of CO2 decreased the amount of sulfur captured during the reaction process. This is attributed to increase in oxidizing medium in the reaction pool from the presence of carbon dioxide. The increase in oxygen fostered H2S combustion to form higher amounts of SO2. Subsequently, the amount of captured sulfur and asymptotic value of H2S decreased. On the other hand, the presence of nitrogen in the acid gas stream did not affect the reaction process significantly. Nitrogen acted as an inert gas on the reactants and did not affect the reaction chemistry.

Simultaneous Absorption of Carbon Dioxide and Sulfur Dioxide into Aqueous 1,8-Diamino-p-menthane

Carbon dioxide and sulfur dioxide were simultaneously absorbed into aqueous 1,8-diamino-p-menthane (DAM) in a stirred semi-batch tank with a planar gas-liquid interface within a range of 0–2.0 kmol/m3 of DAM, 0.01–0.12 mole fraction of CO2, 0.001–0.012 mole fraction of SO2, and 298-318 K. Absorption data of each gas in the CO2-DAM and SO2-DAM systems are obtained to verify their reaction regimes, based on film theory, respectively, which are used to analyze the simultaneous absorption mechanisms of CO2 and SO2 in the CO2-SO2- DAM systems. In the simultaneous absorption rate of CO2 and SO2 into DAM solution, the absorption of CO2 belongs to the second-order reaction of finite rate and the absorption of SO2 belongs to the instantaneous reaction regime.

Gas−Liquid Equilibrium Data for Sulfur Dioxide + Nitrogen in Diethylene Glycol + Water at 298.15 K and 123.15 kPa

Isothermal gas−liquid equilibrium (GLE) data have been measured for the system diethylene glycol (DEG) (1) + water (2) + SO2 (3) + N2 (4) at 298.15 K and 123.15 kPa and SO2 partial pressures in the range of (0.7 to 100) Pa. Measurements were carried out by a saturation method using a glass absorption apparatus, which was controlled at constant temperatures by a thermostatic circulation bath with a Beckmann thermometer. The GLE compositions were obtained with relative uncertainties within ± 0.6 % for SO2 concentration in the liquid phase and ± 3.5 % for SO2 mole fraction in the gas phase. The measurement showed that the system DEG (1) + water (2) in the mass fraction range of w1 = (0.60 to 1.00) decreased the solubility of SO2 and the system DEG (1) + water (2) in the mass fraction range of w1 = (0.00 to 0.60) increased the solubility of SO2. Compared with our previous work (Zhang, J. B.; Wei, X. H.; et al. J. Chem. Eng. Data 2008, 53, 2372−2374; Zhang, J. B.; Wei, X. H.; et al. J. Chem. Eng. Data 2009, DOI: 10.021/je900392e), the solubility of SO2 in pure DEG is 259 mg·L−1 when SO2 volume fraction in the gas phase is Φ3 = 5·10−4, which is higher than in pure ethylene glycol (EG, 128 mg·L−1) and lower than in pure poly(ethylene glycol) 400 (PEG 400, 1330 mg·L−1). The results of this work can be used to provide important GLE data for the design and operation of the absorption and desorption process in flue gas desulfurization (FGD) with potential industrial application of various PEG aqueous solutions.

East Asian SO<sub>2</sub> pollution plume over Europe – Part 1: Airborne trace gas measurements and source identification by particle dispersion model simulations

Abstract. A large SO2-rich pollution plume of East Asian origin was detected by aircraft based CIMS (Chemical Ionization Mass Spectrometry) measurements at 3–7.5 km altitude over the North Atlantic. The measurements, which took place on 3 May 2006 aboard of the German research aircraft Falcon, were part of the INTEX-B (Intercontinental Chemical Transport Experiment-B) campaign. Additional trace gases (NO, NOy, CO, H2O) were measured and used for comparison and source identification. The atmospheric SO2 mole fraction was markedly increased inside the plume and reached up to 900 pmol/mol. Accompanying lagrangian FLEXPART particle dispersion model simulations indicate that the probed pollution plume originated at low altitudes from densely populated and industrialized regions of East Asia, primarily China, about 8–12 days prior to the measurements.

Simultaneous Absorption of Carbon Dioxide and Sulfur Dioxide into Aqueous 2-Amino-2-Methy-1-Propanol

Carbon dioxide and sulfur dioxide were simultaneously absorbed into aqueous 2-amino-2-methyl-1-propanol (AMP) in a stirred semi-batch tank with a planar gas-liquid interface within a range of 0–4.0 kmol/m3 of AMP, 0.03–0.3 mole fraction of CO2, 0.005–2 mole fraction of SO2, and 298–318 K. Absorption data of each gas in the CO2-AMP and SO2-AMP systems are obtained to verify their reaction regimes, based on film theory, respectively, which are used to analyze the simultaneous absorption mechanisms of CO2 and SO2 in the CO2-SO2-AMP systems. The measured absorption rates of CO2 and SO2 are compared to those formulated by an approximate solution of the mass balances with simultaneous reactions.