Simultaneous Removal Of SO2 Research Articles

Utilization of inherent minerals in coal for high-performance activated carbon production: The mechanism of deSO2 and/or deNOx enhanced by in situ transformed calcium sulfide (CaS)

Calcium sulfide (CaS) is transformed from the interaction between inherent pyrite and calcite in coal during activated carbon (AC) preparation by vapor activation, which could impact AC's textural and performance. For elucidating the contribution of in situ transformed CaS on the AC structure and SO2/NO removal, as-obtained AC-XCaS (X is the CaS content) were produced by Taixi coal and calcium sulfide (0–4 wt.%) through steam activation. The textural evolution and denitrification and/or desulfurization were also investigated. The results indicated that: (1) Calcium sulfide declined the burn-off linearly. The graphitization degree of ACs presents first enhancing and then decreasing trend with the CaS content increased. Calcium sulfide promotes the AC's micropore porosity development by catalyzing the corrosion of steam on the carbon surface. The specific surface area including total BET and micropore from 954 m2/g and 894 m2/g (AC) first raised to 1017 m2/g and 962 m2/g (AC-1CaS) and then decreased to 808 m2/g and 768 m2/g (AC-4CaS), respectively. Meanwhile, calcium sulfide improves the AC's amounts of C–O and C=O. (2) Calcium sulfide strengthens AC's removal ability of NO and SO2 evidently. The maximum desulfurization capacity is up to 67.1 mg/g of AC-4CaS, which is higher by 50.8% than 44.5 mg/g of AC. Calcium sulfide enhances AC's surface chemical feature and finally favors the adsorption of SO2/O2/H2O. Meanwhile, calcium sulfide catalyzes the desulfurization reaction. The AC-3CaS's NO conversion is up to 22.7%, which is higher 39.3% than 16.3% of AC. Calcium sulfide favors oxygen dissociation to form intermediate C(O), which could strengthen the adsorption of NH3 and NO. (3) During simultaneous removal of SO2 and NO, calcium sulfide shows that anti-SO2 poisoning ability is promising. The results of this research could complement the reference by utilizing coal with high-inorganic-iron/calcium/sulfur for high-performance AC preparations.

Simultaneous removal of SO2 and NOx by potassium-modified carbide slag

The treatment of solid waste carbide slag (CS) poses an urgent challenge in terms of its resolution. This study presented an efficient and cost-effective method for simultaneous desulfurization and denitrification at low temperatures using different modified potassium compounds (KOH, K2CO3, and KHCO3) as adsorbents. The experimental results revealed the significant impact of potassium modification on the performance of the CS, leading to a significant improvement in its denitrification activity while maintaining the same desulfurization effect. The denitrification rates of the modified CS demonstrated increases by 30 % (KOH), 25 % (K2CO3), and 40 % (KHCO3), respectively, compared to the unmodified CS at 200 ℃. The NO adsorption capacities were 2.48 (KOH), 2.24 (K2CO3), and 3.05 (KHCO3) times that of CS, respectively. Subsequent investigations suggested that the potassium modification process induced changes in the microstructure of CS, augmenting the abundance of oxygen vacancies, KOx, C = O, and Oads, thereby enhancing the intensity and quantity of basic sites. This reduced the activation energy of the CS during simultaneous desulfurization and denitrification. In addition, it was observed that certain byproducts formed during the desulfurization and denitrification processes, such as sulfate, sulfite, and nitrate, accumulated on the surface and within the inner pores of the adsorbents, ultimately resulting in a decline in catalytic activity. This study aims to embrace the “treat waste with waste” approach and is expected to provide guidance for the advancement of simultaneous desulfurization and denitrification technologies targeting solid waste CS.

Simultaneous removal of SO2 and NO by self-activated NaHCO3

Systematical experiments, mechanistic studies, and kinetic studies of SO2/NO removal with NaHCO3 were first carried out in this paper. The results showed that NaHCO3 was self-activated by an in-situ decomposition process that generated more active sites for SO2/NO removal. The efficiency of NO removal was sensitive to the oxygen concentration and the presence of SO2. The optimal SO2/NO removal efficiencies reached 100%/85% at 160 °C and with O2 concentrations over 5%. Additional mechanistic studies showed that the presence of NO facilitated the conversion of SO32-→SO42-. The intermediate NO2 generated by NO oxidation competed with SO2 for adsorption sites. Kinetic studies illustrated that the absorption of NO2 was the rate controlling step in the early NO removal process. The optimal parameters obtained were sulfur-to-sodium ratios of 2–3 and volume space velocities of 20,000–30,000 h−1. A potential application involving “Na2SO4 to NaHCO3” was proposed for Na2SO4 utilization and integrated SO2/NO2/CO2 removal.

Simultaneous removal of SO2, NO and Hg0 using porous carbon/heat-coactivated persulfate system

A novel simultaneous removal technique of SO2, NO, and Hg0 using porous carbon/heat-coactivated persulfate (PS) system was proposed. A series of experiments and theoretical analysis were conducted to explore simultaneous removal process of Hg0, SO2, and NO. Study demonstrates that the developed porous carbon/heat-coactivated PS system gains larger free radical yield and higher pollutants simultaneous removal efficiency than other comparison systems, which are associated with the synergism between porous carbon and heat. High temperature plays a vital role in this co-activation system. Both SO4−· and ·OH play an important role in NO and Hg0 removal, but ·OH is more important for NO removal while SO4−· is more important for Hg0 removal. Both NO and Hg0 removal processes meet pseudo-first-order rapid reaction kinetics, and their removal processes are controlled by mass transfer. Removal efficiencies of NO and Hg0 are increased first and then are decreased with increasing PS concentration, temperature and porous carbon concentration. Increasing pH and concentrations of SO2, NO and Hg0 reduce the NO and Hg0 removal efficiencies. The highest simultaneous removal efficiency of Hg0, SO2, and NO is up to 98.4% for Hg0, 100% for SO2, and 89.3% for NO under an optimized test condition.

SO42−, Cl−, Br−, and TDS removal by semi continuous electrocoagulation reactor using rotating anode

In this study, the simultaneous removal of SO 4 2 − , Cl − , Br − , and TDS from saline lake water was investigated using an emerging electrocoagulation (EC) reactor in a batch and a semi-continuous electrocoagulation mode (batch recirculation system). The possibility of the EC process in salt removal and sludge production were evaluated. The EC continuous reactor with rotating anode was used and the effect of the impeller plate anode was validated. Several variables were estimated to set the optimum operating conditions for a batch system. The effects of variables such as rotation speed (rpm), retention time (min), recirculation flow rate, current density (mA/cm 2 ), inter space distance (mm), pH solution, and continuous flow system were optimized. These operational parameters were set at 75 rpm, 10 min, 4 L/min, 2 mA/cm 2 , pH 8, 1 cm 2 , and 0.25 L/min, respectively. Statistical analyses were performed to determine the optimal EC conditions. The results revealed that the maximum removal efficiency of SO 4 2 − , Cl − , Br − , and TDS were 90.2%, 93.4%, 90.8%, and 92.3%, respectively. Electrical energy, aluminum consumption, chemical reagents, and sludge production were calculated to achieve an operating cost per m 3 of $0.1766. The sludge and treated water were characterized, and the mechanism of the EC technology was assessed. The results revealed that treated water with the use of the EC process was very efficient, with a low overall consumption cost. • SO 4 2 − , Cl − , Br − , and TDS are limited via physical adsorption with Al hydroxides. • Impeller plates of rotating anodes were used. • EC rotation speed, retention time, pH, and current density were the key parameters. • The EC technology revealed efficiency in saline water treatment.

Performance and mechanism of CO2 absorption during the simultaneous removal of SO2 and NOx by wet scrubbing process

The co-removal of CO2 while removing SO2 and NOx from industrial flue gas has great potential of carbon emission reduction but related research is lacking. In this study, a wet scrubbing process with various urea solutions for desulfurization and denitrification was explored for the possibility of CO2 absorption. The results showed that the urea-additive solutions were efficient for NOx and SO2 abatement, but delivered < 10% CO2 absorption efficiency. The addition of Ca(OH)2 dramatically enhanced the CO2 absorption, remained the desulfurization efficiency, unfortunately restricted the denitrification efficiency. Among various operating parameters, pH of solution played a determining role during the absorption. The contradictory pH demands of CO2 absorption and denitrification were observed and discussed in detail. A higher pH of solution than 10 was favorable for CO2 absorption, while the oxidizing of NO to NO2, NO2− or NO3− by NaClO2 was inhibited in this condition. When 7 < pH < 10, it was favorable for the conversion and absorption of NO and NOx. However, the conversion of HCO3− to CO32− was significantly inhibited, hence preventing the absorption of CO2. Large part of Ca(OH)2 became CaCO3 with a finer particle size, which covered the unreacted Ca(OH)2 surface after the reaction. Kinetic analysis showed that the CO2 absorption in urea-NaClO2-Ca(OH)2 absorbent was controlled by chemical reaction in early stage, then by ash layer diffusion in later stage.

Purification mechanism of corona discharge coupled with dimethyl sulfoxide microemulsion for simultaneous desulfurization and denitrification

In this study, a new absorbent dimethyl sulfoxide (DMSO) microemulsion is used, and corona discharge coupled with dimethyl sulfoxide microemulsion is proposed for simultaneous desulfurization and denitrification. This study solves the problem of low efficiency of simultaneous SO2 and NO purification and avoids the problem of easy poisoning of catalysts for simultaneous desulfurization and denitrification. In addition, it makes up for the defects of low efficiency and complex products of desulfurization and denitrification by plasma alone. In this study, the effects of different corona discharge voltages, DMSO microemulsion oil–water ratio and oxygen concentration on the simultaneous removal of SO2 and NO were investigated in detail. The study showed that increasing the voltage and oxygen concentration had a significant promotion effect on the degradation of NO, but the high oxygen concentration would release part of the captured SO2. Under the best experimental conditions, the SO2 removal efficiency could reach 93.4 % and the NO removal efficiency was 84.9 %. In addition, the adsorption energy calculations combined with different initial concentrations and different DMSO microemulsion temperatures illustrate that SO2 and NO react competitively with SO bonds in DMSO and OH bonds in isoamyl alcohol in DMSO microemulsions, with SO2 being preferentially adsorbed. Finally, this study explains in detail the mechanism of simultaneous SO2 and NO degradation, showing that the reactive species generated during corona discharge can excite microemulsions to produce more reactive radicals and active substances to further improve the removal of SO2 and NO.

Simultaneous Removal of SO2 and NO by O3 Oxidation Combined with Seawater as Absorbent

Aiming at NOx (NO 90%, NO2 10%) and SO2 in simulated vessel emissions, denitration and desulfurization were studied through ozone oxidation combined with seawater as absorbent. Specifically, the different influencing factors of denitration and desulfurization were analyzed. The results indicated that the oxidation efficiency of NO can reach over 90% when the molar ratio of O3/NO is 1.2. Ozone oxidation and seawater washing in the same unit can decrease the temperature of ozone oxidation of NO, avoid high temperature ozone decomposition, and enhance the oxidation efficiency of NO. When NO inlet initial concentration is lower than 800 ppm, the NOx removal efficiency can be improved by increasing NO inlet concentration, and when NO inlet initial concentration is greater than 800 ppm, increasing the concentration of NO would decrease the NOx removal efficiency. Increasing the inlet concentration of SO2 has minor effect on desulfurization, but slightly reduces the absorption efficiency of NOx due to the competition of SO2 and NOx in the absorption solution. Besides, final products (NO2−, NO3−, SO32−, and SO42−) were analyzed by the ion chromatography.

Simultaneous Removal of SO2 and NO from the Flue Gas of Marine Ships with a Gas Cyclone–Liquid Jet Absorption Separator

Simultaneous Removal of SO₂ and NO from the Flue Gas of Marine Ships with a Gas Cyclone–Liquid Jet Absorption Separator

Preparation of ozone for simultaneous removal of SO2 and NOx with mud-phosphorus slurry

Preparation of ozone for simultaneous removal of SO2 and NOx with mud-phosphorus slurry

Simultaneous Removal of SO2 and NO x Using Steel Slag Slurry Combined with Ozone Oxidation.

In this work, steel slag slurry was used in combination with O3 oxidation for the simultaneous removal of SO2 and NOx in a laboratory-scale wet flue gas desulfurization process. The effects of the oxidation temperature, steel slag concentration, initial SO2 concentration, and pH value on the desulfurization and denitrification efficiencies were studied. The results showed that the highest NOx removal efficiency occurred at an oxidation temperature of 90 °C. With an increase of the oxidation temperature above 90 °C, the denitrification efficiency decreased due to the decomposition of N2O5. The effect of the SO2 concentration on denitrification was complicated. When the concentration of SO2 was 500 ppm, generation of SO32– promoted the absorption of NO2. However, higher SO2 concentrations strengthened the competitive absorption of SO2 and NOx. In the pH range of 8.5–4.5, the denitrification efficiency was maintained at about 96%. The component analyses of the aqueous solution and the solid residue were conducted to investigate the compositions of the absorption products. The results showed that NO3– and SO42– were the major anions in the aqueous solution. The nitrogen balance was analyzed to be 95.8%, clearly illustrating the migration and transformation path of nitrogen. In the solid residue, most alkaline substances were consumed, and the final products were mainly CaSO4 and FeO. Accordingly, the reaction mechanism of simultaneous desulfurization and denitrification using steel slag combined with ozone oxidation was proposed.

Investigation on Simultaneous Removal of SO2 and NO over a Cu–Fe/TiO2 Catalyst Using Vaporized H2O2: An Analysis on SO2 Effect

Investigation on Simultaneous Removal of SO₂ and NO over a Cu–Fe/TiO₂ Catalyst Using Vaporized H₂O₂: An Analysis on SO₂ Effect

Simultaneous removal of SO2 and NOx from flue gas by low-temperature adsorption over activated carbon

An exceptional phenomenon has been observed that SO2 and NOx in flue gas can be effectively adsorbed over activated carbon with a surprising capacity at cold temperatures with the presence of oxygen. In this study, the adsorption characteristics of NO and SO2 over activated carbon at 80, 20, 0, and − 20 is experimentally investigated. Without the presence of oxygen, adsorption of NO is negligible. In the presence of oxygen, NO can be oxidized to NO2 over activated carbon which leads to the co-adsorption of NO/NO2 within the adsorption bed. Catalytic oxidation of NO over activated carbon can be significantly enhanced at cold temperatures, leading to an extraordinary increase of adsorption capacity of NO. With an initial concentration of NO = 200 ppmv and a space velocity of 5000 h−1, the average specific capacity increases from 3.8 to 169.1 mg/g when the temperature decreases from 80 to – 20 ℃. For NO–O2 co-adsorption, the specific capacity increases along the adsorption bed due to the increasing NO2 concentrations. The adsorption capacity of SO2 is also significantly enhanced at cold temperatures. With an initial concentration of SO2 = 1000 ppmv, the specific capacity increases from 12.9 to 123.1 mg/g when the temperature decreases from 80 to – 20 ℃. A novel low-temperature adsorption (LAS) process is developed to simultaneously remove SO2 and NOx from flue gas with a target of near-zero emission. A pilot-scale testing platform with a flue gas flowrate of 3600 Nm3/h is developed and tested. Emission of both SO2 and NOx is less than 1 ppmv, and the predicted energy penalty is about 3% of the net generation.

Removal of gas-phase arsenic and selenium in flue gas by a new combined spray-and-scattered-bubble technology based on ammonia desulphurization

The integrated control of multiple pollutants is a promising approach for efficient and economical pollution reduction. Inspired by the simultaneous removal of SO2 and NOx by the spray-and-scattered-bubble (SSB) technology, this paper further explores gas phase arsenic and selenium removal ability of this new technology. Ammonia concentration, SO2 concentration, liquid/gas ratio and immersion depth, which are the key operating parameters of SSB technology, are evaluated to determine their effect on arsenic and selenium removal. The experimental results indicate that ammonia concentration and SO2 will facilitate the simultaneous removal of arsenic and selenium by SSB technology. However, the excess ammonia concentration and SO2 should avoided to prevent the decrease in removal efficiency caused by the ammonia escape, increased mass transfer resistance, and mechanical carry-over. The maximum removal efficiency for arsenic can be obtained at the liquid-gas ratio of 10 L/m3, and for selenium, the maximum removal efficiency will be reached at 14 L/m3. For the technology of spray-and-scattered-bubble, chemical reaction and mass transfer jointly play the role in contaminant removal. By changing the immersion depth and measuring the corresponding pressure drop, the weight assigned to the effect of chemical reaction and mass transfer effect could be ascertained to a certain degree. It is speculated that chemical reaction will play a more important role for selenium removal in the bubble zone than the mass transfer. Moreover, for arsenic, mass transfer effect will play a more important role than chemical reaction. The sensitivity analysis for simultaneous removal of arsenic and selenium by SSB technology indicating that the variation of operating conditions will lead to a greater change in arsenic removal as compared with selenium.

Simultaneous NOx and SO2 removal during wet flue gas desulfurization, using copper smelter slag slurry combined with yellow phorphorus

AbstractThe study of copper slag has attracted the attention of scholars from both China and around the world. But few have paid attention to its applications in the simultaneous removal of SO2 and NOx in wet flue gas desulfurization (WFGD), becasue WFGD technique is inappropriate for directly treating NOx owing to the low solubility of NO. This work aims to improve NOx removal efficiency in WFGD technology using copper slag slurry associated with the oxidation of NOx by yellow phosphorus. Different operating conditions, including dispersion of P4, solid‐liquid ratio, initial pH value of copper slag slurry, reaction temperature, oxygen content, and gas flow rate, were compared regarding the efficiency of SO2 and NOx simultaneous removal. The characterizations were carried out on the liquid and solid part of fresh and spent copper slag slurry after filtration. The results indicated that a great amount of metals ions, such as Fe3+ and Zn2+, were leached by reacting with produced acids (H2SO4, HNO3, and H3PO4), which had a liquid‐phase catalytic oxidation on SIV species (SO32−/HSO3−), leading to promotion in absorption for SO2. The copper slag played a significant role in dispersing the yellow phosphorus and promoting ozone generation, thus improving NOx removal efficiency. The reaction pathway can be divided into three parts: (a) ozone generation induced by yellow phosphorus, (b) the oxidation of NO by O3 and then dissolution in aqueous solution, and (c) the dissolution of SO2 and the liquid‐phase oxidation for SO2 through metal ions produced by the reaction between acid and copper slag.

Simultaneous removal of SO2, NOx and Hg0 by O3 oxidation integrated with bio-charcoal adsorption

Simultaneous removal of SO2, NOx and Hg0 using O3 and corn stalk bio-charcoal (CR)/coconut shell activated carbon (CS) was compared in a fixed bed. The effects of temperature, adsorption time and ratio of O3/NO on the removal efficiency of NO, Hg0 and SO2 by CR/CS were studied, and the CR and CS was characterized and analyzed. The results indicated that the oxidation rate of NO and Hg0 increased with the increase of O3/NO ratio, while the oxidation rate of SO2 first increased and then decreased slightly. The increase of temperature inhibits the oxidation of NO but promotes the oxidation of Hg0 and SO2. At 140°C and O3/NO ratio was 1.4, the oxidation rate of NO, Hg0 and SO2 is 99%, 78.6% and 3.5%, respectively. As O3/NO ratio increased from 0.4 to 1.4, the removal efficiency of CR for NOx increased from 4.6% to 93%, and CS increases from 4.5% to 79%. CR and CS can reduce part of NO2 and increase NO concentration at the outlet. NOx adsorption performance on CR is relatively better, while those of Hg0 and SO2 on CS are relatively stronger. CS has stronger physical adsorption capacity than CR. The relative content of oxygen-containing functional groups C-O and C=O on the surface of CR is higher than that of CS, while its relative content of COOH and O=C-O is lower.

Recent advances in simultaneous removal of SO2 and NOx from exhaust gases: Removal process, mechanism and kinetics

• Oxidation, reduction, adsorption/absorption and microbial approaches are summarized. • Removal processes are divided into gas-gas, gas-liquid and gas-solid reactions. • Removal process, mechanism, and kinetics of pathways are systematically reviewed. • Effects of catalyzers and reaction conditions on removal efficiency are analyzed. • Challenges and potential breakthroughs in future de-SO 2 and de-NO x are discussed. SO 2 and NO x , major gaseous pollutants in exhaust gas, can exert adverse effects on human health and environmental disaster. Therefore, numerous desulfurization (de-SO 2 ) and denitrification (de-NO x ) technologies have been designed to reduce SO 2 and NO x emissions. Compared to traditional multi-step removal processes, simultaneous removal of SO 2 and NO x has been attracting significant attention recently. This paper timely reviewed available literature focused on simultaneous de-SO 2 and de-NO x methods, which are classified into four pathways as oxidation, reduction, adsorption/absorption and microbial purification. The removal process, basic mechanism and kinetics of each pathway are systematically reviewed in consideration of reactants, catalyzers, temperatures and atmosphere. Moreover, the main challenges and potential breakthroughs in developing novel simultaneous de-SO 2 and de-NO x methods are critically discussed to provide a roadmap for prospective research activities. Therefore, this review provides a deeper insight in understanding the mechanisms of de-SO 2 and de-NO x , and then helps to develop innovative simultaneous removal methods or improve the efficiency of available abatement methods.

Erratum for “Simultaneous Removal of SO2 and NO by Electromigration-Enhanced Chemical Absorption” by Guifen Shen and Zuwu Wang

Erratum for “Simultaneous Removal of SO2 and NO by Electromigration-Enhanced Chemical Absorption” by Guifen Shen and Zuwu Wang

Simultaneous removal of SO2 and NOx with [rad]OH from the catalytic decomposition of H2O2 over Fe-Mo mixed oxides

In this paper, the simultaneous removal of SO2 and NOx catalyzed by Fe-Mo mixed oxides at varying Mo/Fe atomic ratios was reported for the first time with the aim of reducing H2O2 consumption and elucidating the roles of Fe and Mo species in the catalytic process. Fe-Mo mixed oxides with varying Mo/Fe atomic ratios were synthesized and the catalytic performances were systematically studied. The catalyst with Mo/Fe atomic ratio of 2.0 exhibited the highest activity, with which removal efficiencies of 89.4 % for NOx and 100 % for SO2 can be attained at extremely low H2O2 dosage. Products analysis revealed that SO2 was mainly removed via wet scrubber, while the adequate oxidation resulting from OH radicals was the prerequisite for NOx removal. The redox pair of Fe2+/Fe3+ played a significant role in decomposing H2O2, while Mo species had double effect on catalytic activity. Higher Mo content resulted in abundant oxygen vacancies and stronger surface acidity, which favored OH formation. However, the excessive Mo content involved severe surface Mo enrichment and remarkably reduced the active sites of Fe species. The H2O2/Fe-Mo catalyst system showed excellent stability and had a promising prospect for simultaneously removing SO2 and NOx in coal-fired flue gas.

Simultaneous Removal of SO2 and Hg0 by Composite Oxidant NaClO/NaClO2 in a Packed Tower.

Based on the implementation of the global Minamata Convention, developing an efficient and economical technology for mercury reduction in coal-fired flue gas becomes a hotspot in the field of air pollution control. The composite oxidant NaClO/NaClO2 combined with limestone was used in the simultaneous removal of SO2 and Hg0 in this study, and the three-factor and four-level orthogonal experiments were performed in a packed tower. The influential sequence of various factors on SO2 and Hg0 removals was investigated through range analysis of the orthogonal experiments. Results showed that factors affecting desulfurization was C > A > B (liquid–gas ratio > oxidant concentration ratio > initial pH of absorption liquid), while factors affecting Hg0 removal was A > C > B (oxidant concentration ratio > liquid–gas ratio > initial pH of absorption liquid). Optimum conditions of simultaneous desulfurization and demercuration by NaClO/NaClO2 were A4B1C4; that is, the oxidant concentration ratio was 10/4 (mmol/L:mmol/L), the initial pH was 5, and the liquid–gas ratio was 18 (L/m3). The simultaneous removal efficiencies of SO2 and Hg0 reached 99.5 and 85.4% under these optimum conditions, respectively. Analysis of the characteristics of the solid products showed that the main products of the wet oxidation were CaSO4 and CaSO3. Analysis of the existing form of oxidized mercury showed that 23% of mercury was in the gypsum, while 77% was in the supernatant. Results of this research would provide a practical reference for promoting the simultaneous removal of SO2 and Hg0 by NaClO/NaClO2 with limestone in industrial application.