Process For Removal Of SO2 Research Articles

Multi-scale numerical analysis of Ca-based desulfurizer dynamics characteristics and SO2 absorption processes in industrial-scale SDA-FGD reactor

Spray dry absorption flue gas desulfurization technology is widely employed to control sulfur dioxide emissions from industrial pollutant gases. This study employs the multiphase particle-in-cell method to numerically simulate gas–solid heat transfer, SO2 removal processes, and the effect of operating conditions in the SDA reactor. The flue gas desulfurization model used has been experimentally validated. The results indicate that flue gas and slurry droplets exhibit swirling flow along the reactor walls, forming gas vortices at the top and near the outlet. The temperature and Reynolds number of slurry droplets show minimal variation when particle size is below 43 μm. The heat transfer coefficient of slurry droplets is notably higher at the reactor top and increases with the slip velocity of the droplets. Furthermore, the CaSO3 volume fraction increases with longer residence times of the slurry droplets in the reactor. When the height and diameter of the main reaction area are lower than 14 m and 8.5 m, respectively, the SO2 mass fraction in the central area undergoes significant changes. The SO2 inlet concentration is negatively correlated with desulfurization efficiency, whereas the slurry injection speed, along with the diameter and height of the main reaction region, are positively correlated with desulfurization efficiency. Among these factors, the SO2 inlet concentration and the height of the main reaction region have the most substantial impact on desulfurization efficiency.

Experimental evaluation and neural networks modeling of removal efficiency and volumetric mass transfer coefficient for gas desulfurization in spray tower

Spray towers to can be used to absorb pollutants gases. Due to the complexity of the process, to propose mathematical models for prediction of removal efficiency and volumetric mass transfer coefficient, is a difficult task. This work aimed to evaluate the influence of variables on the SO2 removal process in a spray tower and to obtain an artificial neural network (ANN) to predict the removal efficiency and the volumetric mass transfer coefficient for columns with different heights, gas and liquid flow rates. The tower built in this study reached a maximum efficiency of 99.47% and showed that it was possible to achieve high levels of removal without the need to build high towers. The best ANN obtained presented error of 2.76% for the removal efficiency of the SO2 and 6.79% for the volumetric mass transfer coefficient. The obtained results were very promising in the prediction of important parameters in the process of removing atmospheric pollutants via spray tower.

Simultaneous removal of SO2 and NO by phosphate tailings-derived composite slurry: A study of phosphorus element migration and transformation

In this study, we developed a composite slurry using industrial hazardous solid waste phosphate tailings and yellow phosphorus for the simultaneous removal of SO2 and NO. Additionally, the migration and transformation of the P element within the slurry were thoroughly investigated. The experimental results revealed that this composite slurry exhibited efficient removal of both SO2 and NO. Further investigations indicated that Ca5(PO4)3F and CaMg(CO3)2 within the composite slurry acted as the primary active phases during the SO2 removal process. On the other hand, the yellow phosphorus (P4) components facilitated the conversion of O2 to O3, which subsequently oxidized NO to nitrate. Throughout the course of the reactions, significant amounts of the P element in the solid phase (Ca5(PO4)3F and yellow phosphorus (P4) were leached out as PO43−, accumulating in the liquid phase. The resulting solution containing NO3− and PO43− could potentially serve as a valuable raw material for the production of nitrogen-phosphorus composite fertilizers. Additionally, a small portion of the P element within the composite slurry was oxidized to P2O5 and released into the gas phase, resulting in a partial loss of the P element.

Simultaneous removal of NO and SO2 by Fe(II)/peracetic acid oxidation system: Operating conditions, removal efficiency and removal mechanism

The request of synergistic control of PM2.5 and O3 pollution has made NO and SO2 emission control a hot topic again in the field of atmospheric environment. An advanced oxidation process (AOPs) for simultaneous removal of SO2 and NO from the flue gas of small and medium-sized boilers and kilns by Fe(II) activated peracetic acid (PAA) was investigated. The influences of operating parameters like reaction temperature, initial pH, concentrations of PAA and Fe(II) on SO2 and NO removal efficiency in Fe(II)/PAA system were studied. The NO removal efficiency was increased with higher PAA concentration and lower initial pH. Changes in reaction temperature and Fe(II) concentration had a dual effect on NO removal efficiency. The SO2 removal efficiency can be stably maintained above 99 % under all operating conditions, which is of great significance for practical engineering applications. Results indicated that the maximum removal efficiency of 92.3 % for NO and 99.5 % for SO2 were obtained under the optimal conditions of 100 mM PAA, 10 mM Fe(II), operating temperature 45 °C and initial solution pH 2.4. PAA was confirmed to play a major role in NO removal rather than coexistent H2O2. According to the electron paramagnetic resonance (EPR) technology, methyl phenyl sulfoxide (PMSO)-based probe experiments and radicals quenching experiments, reactive oxidizing species such as CH3C(O)O·, CH3C(O)OO·, ·OH and FeIVO2+ were generated in the Fe(II)/PAA system, where organic radicals (R-O•) were confirmed to be the major ones affecting NO oxidation. Ion chromatographic analysis revealed that SO42- and NO3- were the main products of SO2 and NO removal, and the mechanism of SO2 and NOx oxidation and removal by Fe(II)/PAA system was thus elucidated, which would promote the industrial application of this novel method.

Improving SO2 and/or NO removal by activated carbon through comprehensive utilization of inherent pyrite and calcite in coal

Utilization of inherent active minerals in coal is an effective strategy for high-performance activated carbon (AC) production, such as calcite and pyrite. In this research, ACs were prepared through blending demineralized Ningxia coal with calcite (CaCO3, 0–8 wt.%) and pyrite (FeS2, 0–3 wt.%). The combined effect of inherent pyrite and calcite in coal on the as-prepared AC’s texture and SO2 and/or NO removal performance was discussed. The results indicated that: (1) The combined effect of calcite and pyrite showed nonlinearly on weight loss and burn-off, and reduced AC’s yield. The impact of calcite on pore structure was more evident than pyrite. Meanwhile, calcite and pyrite enhance the content of CO (C 1 s) and π-π*, and new mineral CaS could be formed through interaction between calcite and pyrite; (2) Calcite and pyrite promote AC's SO2 and NO removal ability evidently. Pyrite and calcite regulate physiochemical texture, and the physical and chemical adsorption of SO2/O2/H2O was enhanced. Meanwhile, iron and calcium ingredients in AC catalyzed desulfurization. CaO could participate in the SO2 removal process. Fe2O3 oxidized SO2 to SO3 and then forms H2SO4 rapidly, meanwhile, a redox cycle of Fe3+ and Fe2+ was established. Enhancement of NO removal was more evident than SO2, which was mainly due to Fe2O3 being helpful to oxidizing NO to NO2, and calcium components could enhance the adsorption of NH3 and NO and finally promote “fast SCR”; (3) During simultaneous desulphurization and denitrification, sulfur capacity was obviously enhanced and NO conversion was declined. The mechanism was proposed as follows: the existence of NH3 could enhance the SO2 adsorption through chemisorption and/or catalytic oxidization; Due to the competitive adsorption of SO2, denitrification declined. This research could guide high-performance AC production by utilizing high-inorganic-calcium/iron/sulfur coal.

Selection of additives to improve the efficiency of NOx and SO2 treatment in electron beam process

In this study, we used mixed additives (base additive + oxidant) to increase the efficiency of the NOx and SO2 removal process using an electron beam. To assess the removal characteristic and efficiency of their compounds, influencing factors, such as the presence or absence of mixed additives, the stoichiometric ratio of the oxidant among the mixed additives, and the absorbed dose, were investigated. As a result, the removal efficiency when using NaOH as a base additive for both NOx and SO2 was higher than that when using NH4OH; in the case of NO, when NaOH was used as a sole additive, the efficiency was the highest at 87.90%. For NO2, when NaOH was mixed with the oxidant NaCl, the removal efficiency was confirmed to increase by about 6%. Furthermore, in most cases of NOx, as the absorbed dose increased to (0−20) kGy, the removal efficiency increased; but when NaClO2 was used as the oxidant, the removal efficiency tended to decrease. However, when a mixed additive of NaOH + NaClO2 was used at a low dose (5 kGy), the removal efficiencies of NO and NO2 were confirmed to be 89.28% and 88.16%, respectively, indicating high removal efficiency.

Buffer effect of MgO on Na2SO3 to stabilize S(IV) for the enhancement in simultaneous absorption of NOx and SO2 from non-ferrous smelting gas.

Oxidation-reduction-absorption based on sulfite is a promising process for simultaneous removal of NOx and SO2. However, excessive oxidation of sulfite and competitive absorption between NOx and SO2 limit its application. A matching strategy between antioxidants and alkaline agents has been proposed to solve these problems and enhance the absorption process. The comparison results of inhibitors showed that hydroquinone exhibited long-term high-efficiency inhibition of S(IV) (SO32-/HSO3-) oxidation. The comparison of alkaline agents showed that the Na2SO3 solution with heterogeneous mixture of MgO and hydroquinone exhibited better absorption performance than that with other combinations. The absorption amounts of NOx in 0.15mol/L Na2SO3 50mL solution added 0.1% hydroquinone (HQ) with 0.09mol/L MgO were 2.24mmol, which improved 5 times than that without additives. In addition, studies on the influence of pH showed that the pH of MgO mixture could be stabilized at 9-10 for a long time, while the pH of Na2CO3 mixture decreased faster. Further studies suggested that the hydration of MgO resulted in the solution with MgO keeping high pH. This is also the main reason why the combination of MgO and hydroquinone is superior to the combination of Na2CO3 and hydroquinone in desulfurization and denitration performance.

Simulation of SO2 removal process from marine exhaust gas by hybrid exhaust gas cleaning systems (EGCS) using seawater and magnesium-based absorbent

Exhaust gas from navigation is an important source of air pollution, especially in coastal and port cities. The installation of a hybrid exhaust gas cleaning system (EGCS) is a popular method to reduce the SO2 emission because of their flexibility and efficiency. However, limited by the experience of operators, the operation of EGCS can hardly meet the requirement of economy and safety demands. In this paper, a detailed model of hybrid EGCS is developed to study the effect of important factors on SO2 absorption process and crystallization process. A comparison between seawater and magnesium-based absorbent on the SO2 absorption process in the droplet and the scrubber is carried out. Compared with seawater, magnesium-based absorbents are more adaptable to temperature and the SO2 concentration. What’s more, in order to prevent the EGCS from scaling and ensure the safe operation of EGCS, the safe operating ranges of magnesium-based absorbent under different temperature and oxidation rate are studied. Finally, an operation strategy of the EGCS for different absorbents is proposed. The operator can adjust the liquid-gas ratio of the current operating mode or switch to other modes according to the temperature and pH of seawater and emission standard. These results would be helpful for the design and the operation of the EGCS.

Economic performance assessment of elemental sulfur recovery with carbonate melt desulfurization process

This study develops an elemental sulfur recovery (ESR) process from sulfur dioxide (SO2) as a hazardous material removed from flue gas emitted at thermal coal-fired power plants with a carbonate melt flue gas desulfurization (CMFGD) process. The carbonyl sulfide (COS) generated as a byproduct after removing SO2 from flue gas using carbonate melt in the CMFDG is utilized as a resource to produce elemental sulfur by applying the hydrolysis and Claus processes in the ESR process. In addition, to increase energy independence in the integrated CMFGD-ESR process, heat integration was applied by introducing new heat exchanger networks that utilize the waste heat in the proposed process. The levelized cost of the integrated CMFGD-ESR process was determined to be US$ 811 per ton SO2 removed; from this result, the proposed process to remove hazardous material from flue gas emitted at thermal coal-fired power plants is economically benign compared to conventional SO2 removal processes (US$ 500 ~ US$ 1200 per ton SO2 removed), which use limestone as the raw material.

Removal of sulfur dioxide from air using a packed-bed DBD plasma reactor (PBR) and in-plasma catalysis (IPC) hybrid system.

Sulfur dioxide, a noxious air pollutant, can cause health and environmental effects, and its emissions should be controlled. Nonthermal plasma is one of the most effective technologies in this area. This study evaluated the efficiency of a packed-bed plasma reactor (PBR) and in-plasma catalysis (IPC) in SO2 removal process which were finally optimized and modeled by the use of the central composite design (CCD) approach. In this study, SO2 was diluted in zero air, and the NiCeMgAl catalyst was selected as the catalyst part of the IPC. The effect of three main factors and their interaction were studied. ANOVA results revealed that the best models for SO2 removal efficiency and energy yielding were the reduced cubic models. According to the results, both PBR and IPC reactors were significantly energy efficient compared with the nonpacked plasma reactor and had high SO2 removal efficiency which was at least twice larger than that of the nonpacked one. Based on the results, the efficiency of IPC was better than in PBR, but its performance decreased over time. However, the PBR had relatively high SO2 removal efficiency and energy efficiency compared to the nonpacked reactor, and its performance remained constant over the studied time. In optimization, the maximum SO2 removal efficiency and energy efficiency were 80.69% and 1.04 gr/kWh, respectively (at 1250 ppm, 2.5 L/min, and 18 kV as the optimum condition) obtained by the IPC system which were 1.5 and 1.24 times greater than PBR, respectively. Finally, the model's predictions showed good agreement with the experiments.

SO2 rapid adsorption and desorption over activated semi coke in a rotary reactor

Herein, activated semi coke (ASC) adsorbents were prepared and tested for SO2 adsorption-desorption process in a rotary reactor. The experiment results showed that the nitric acid activated semi coke (ASC-1) had a higher SO2 adsorption capacity and a better SO2 removal ability in the SO2 adsorption-desorption dynamic process. And the SO2 adsorption efficiency of ASC-1 in the dynamic SO2 removal process was increased from 57.5% to 88.3% at 200 °C with the extension of desorption time from 60 s to 180 s. Increasing the desorption temperature was an effective method to improve SO2 removal efficiency in the rotary reactor. The SO2 adsorption efficiency of ASC could be improved from 52.5% to 80.7% with the desorption temperature increasing from 100 °C to 300 °C. Moreover, the mechanisms of SO2 adsorption-desorption dynamic process over ASC in rotary reactor at different temperatures were also summarized. There were two desorption paths for SO2 species adsorbed on the ASC surface under the purge of desorption gas CO. One of the paths was that the weakly adsorbed SO2 and some –SO3- species were directly desorbed from ASC surface under the purge of CO, which was the dominant SO2 desorption path. And the other path, which was not activated at low temperature (<200 °C), was that sulfate and part of sulfite species were combined with CO first, then decomposed and desorbed from ASC in the form of SO2 under not too high temperature, while the CO involved in the combination was released in the form of CO2.

Application of dielectric barrier discharge (DBD) plasma packed with glass and ceramic pellets for SO2 removal at ambient temperature: optimization and modeling using response surface methodology

Air pollution is a major health problem in developing countries and has adverse effects on human health and the environment. Non-thermal plasma is an effective air pollution treatment technology. In this research, the performance of a dielectric barrier discharge (DBD) plasma reactor packed with glass and ceramic pellets was evaluated in the removal of SO2 as a major air pollutant from air in ambient temperature. The response surface methodology was used to evaluate the effect of three key parameters (concentration of gas, gas flow rate, and voltage) as well as their simultaneous effects and interactions on the SO2 removal process. Reduced cubic models were derived to predict the SO2 removal efficiency (RE) and energy yield (EY). Analysis of variance results showed that the packed-bed reactors (PBRs) studied were more energy efficient and had a high SO2 RE which was at least four times more than that of the non-packed reactor. Moreover, the results showed that the performance of ceramic pellets was better than that of glass pellets in PBRs. This may be due to the porous surface of ceramic pellets which allows the formation of microdischarges in the fine cavities of a porous surface when placed in a plasma discharge zone. The maximum SO2 RE and EY were obtained at 94% and 0.81 g kWh−1, respectively under the optimal conditions of a concentration of gas of 750 ppm, a gas flow rate of 2 l min−1, and a voltage of 18 kV, which were achieved by the DBD plasma packed with ceramic pellets. Finally, the results of the model’s predictions and the experiments showed good agreement.

Removal and recovery of SO2 and NO in oxy-fuel combustion flue gas by calcium-based slurry

This study investigates the use of calcium-based slurry for simultaneous removal NO and SO2 from oxy-fuel combustion flue gas, and recovery of the sulfur and nitrogen species in resulting solutions. The experiments were performed in a bubbling reactor in a transient mode under the pressure of 20 bar. The various influencing factors including the CaO amount, carrier gas (N2/CO2), and absorption time on the simultaneous NO and SO2 removal process, and the solution products were studied comprehensively. The results show that the NO2 removal efficiency can be improved by the presence of CO2, and the gas phase HNO2 produces in this process. The addition of CaO has positive effects not only on the NO2 removal efficiency but also on the formation of stable HNO3. With the presence of CO2, CaCO3 is formed in a solution initially. With the decrease of pH, CaCO3 is gradually converted to CaSO4, and in particular CaCO3 can be fully avoided through decreasing the pH of an absorption solution to 1.14. At the same time, the formation of unstable S(IV) and NO2- can be prevented when the solution pH is lower than 1.37. The nitrogen and sulfur compounds in the absorption solution (at pH 1.14) were further separated by the addition of different amounts of CaO. In particular, 95% of SO42- finally can be recovered in the form of CaSO4.2H2O with nitrogen in solution existing as NO3- by controlling the Ca/S ratio at 4.70. The effectiveness of calcium-based slurry on the removal and recovery of SO2 and NO is confirmed.

Promotional effect of cyclic desulfurization and regeneration for selective catalytic reduction of NO by NH3 over activated carbon

Cyclic desulfurization-regeneration-denitrification of activated carbon (AC) has been widely used as a cost-effective integrated process for the simultaneous removal of SO2 and NOx. In this work, the influence of cyclic desulfurization and regeneration (C-S-R) on selective catalytic reduction (SCR) of NOx by NH3 was systematically investigated. The results indicated that the SCR activity of AC significantly improved after several desulfurization and regeneration cycles. Different characterization tests were carried out to reveal the internal correlations among the structures, acid/redox properties and SCR activities of the regenerated carbons. Results showed that the increased phenol, anhydride and ester groups were mainly responsible for the enhanced SCR activity, which not only promoted the oxidation of NO to NO2, but also increased the NH3 adsorption. Furthermore, in situ diffuse reflectance infrared transform spectroscopy (DRIFTS) results indicated that the SCR reaction over regenerated carbons mainly obeyed the Eley-Rideal mechanism and the Lewis acids induced by anhydride and ester groups played significant roles in SCR reaction. Hence, the promoting effect of C–S-R on denitrification strongly supports the sustainability of AC in reducing pollution emission and facilitates cleaner production.

A combination process of mineral carbonation with SO2 disposal for simulated flue gas by magnesia-added seawater

The desulfurization by seawater and mineral carbonation have been paid more and more attention. In this study, the feasibility of magnesia and seawater for the integrated disposal of SO2 and CO2 in the simulated flue gas was investigated. The process was conducted by adding MgO in seawater to reinforce the absorption of SO2 and facilitate the mineralization of CO2 by calcium ions. The influences of various factors, including digestion time of magnesia, reaction temperature, and salinity were also investigated. The results show that the reaction temperature can effectively improve the carbonation reaction. After combing SO2 removal process with mineral carbonation, Ca2+ removal rate has a certain degree of decrease. The best carbonation condition is to use 1.5 times artificial seawater (the concentrations of reagents are 1.5 times of seawater) at 80°C and without digestion of magnesia. The desulfurization rate is close to 100% under any condition investigated, indicating that the seawater has a sufficient desulfurization capacity with adding magnesia. This work has demonstrated that a combination of the absorption of SO2 with the absorption and mineralization of CO2 is feasible.

Modeling and Simulation of Gas Liquid Absorption Column for So2 Removal Process

During coal combustion, sulphur in the coal is converted into sulphur dioxide (SO2).This sulphur dioxide (SO2) is responsible for the formation of acid rain which is one of the widespread forms of pollution all over the world that causes harmful effects to humans and environment. To minimize the adverse impacts of SO2, it must be removed from flue gas. For reduction of SO2, flue gas desulphurization (FGD) is most commonly used. The mathematical viewer is developed and simulated for a gas liquid absorption column to control the flow rate of H2O2.The model equation is developed by considering material balance around the column. The absorption rate is determined by using different concentration of sulphur dioxide with hydrogen peroxide. Hydrogen peroxide, not only absorbs the SO2 but it also produce useful by-product in the form of sulphuric acid (H2SO4).

Modeling of SO2 seawater scrubbing in countercurrent packed-bed columns with high performance packings

Packed-bed columns with fourth generation random packings offer an attractive way to implement SO2 seawater scrubbing on-board large marine ships because of small two-phase pressure drop, high capacity and high SO2 removal efficiency. SO2 seawater scrubbing was investigated via an Eulerian 3-D model based on the macroscopic volume-averaged continuity, momentum, energy and species balance equations in the liquid and gas phases. The performance of SO2 seawater absorption process in packed-bed column reactors with fourth generation random packings can be enhanced by the increase of liquid flow rate and the decrease of liquid temperature. Consequently, SO2 seawater scrubbing on-board large marine ships improves significantly in the temperate oceans with an average temperatures between 10 and 20 °C. The increase of pressure improves the driving force of gas-liquid mass transfer and subsequently SO2 removal process which becomes completely at lower values of liquid-to-gas ratio. SO2 seawater scrubbing at higher pressure increases the capital cost and energy requirement but offers major improvements such as total removal of SO2 at large sulfur content of fuel and prevention of losing of engine power because of the large counter pressure to the incoming exhaust. The operation with extra packed bed height allows to amplify the gas–liquid contact time and consequently the absorption process performance.

전자빔을 이용한 SO2 제어공정 개선을 위한 첨가제 연구

전자빔을 이용한 SO2 제어공정 개선을 위한 첨가제 연구

Interaction between NO and SO2 removal processes in a pulsed corona discharge plasma (PCDP) reactor and the mechanism

The interaction between De-NO and De-SO2 from flue gas in a pulsed corona discharge plasma (PCDP) reactor was studied experimentally. A mechanism and kinetic scheme of De-NO and De-SO2 inside the PCDP reactor has been proposed and verified by comparison of the simulated and experimental results. The dominant radicals and elementary reactions are confirmed through sensitivity analysis. It has been found that there is significant interaction between the De-NO and De-SO2 processes in a PCDP reactor, and that the De-NO reactions prevail over the De-SO2 ones. The interaction consists of competitive reactions between NO and SO2 involving oxidative radicals, as well as interaction reactions between NO, SO2 and their derivatives. Through sensitivity analysis it has been found that the most effective elemental reaction to De-NO is NO + HO2 <=> OH + NO2 and that the most helpful radical is HO2. The most effective reaction for De-SO2 is SO2 + O <=> SO3 and the most helpful radical is atomic O. The study reveals the interaction mechanism between De-NO and De-SO2 in PCDP and provides a theoretical basis to improve the performance of simultaneous NO and SO2 abatement in a PCDP reactor.

Evaluation of electrical energy consumption in UV/H2O2 advanced oxidation process for simultaneous removal of NO and SO2

Evaluation of electrical energy consumption in UV/H2O2 advanced oxidation process for simultaneous removal of NO and SO2