SO2 Removal Efficiency Research Articles

Flue‐Gas Desulfurization by Using a HiGee Electric‐Field Device

AbstractAn innovative technique to remove SO2 from flue gas, comprising a rotating packed bed (RPB) coupled with an electric‐field device, is presented herein. The effects of operating conditions, such as packing type, rotation speed, gas‐liquid volumetric ratio, Na2SO3 content, and voltage supply on SO2 removal efficiency (η), as well as the gas‐phase overall volumetric mass‐transfer coefficient (KGa), were systematically investigated. Results indicate that a high η can be achieved under certain operating conditions. A correlation to predict KGa was also established and results show that the predicted values are in agreement with the experimental results. This work generally provides a feasible means of intensification for flue gas desulfurization.

SO3 Removal from Flue Gas with Ca(OH)2 in Entrained Flow Reactors

Experiments were carried out in a pilot-scale entrained flow reactor (EFR) to investigate the reaction of SO3 with Ca(OH)2 as a method of dry sorbent injection (DSI) for SO3 removal from flue gas. The results indicate that SO3 can be removed by Ca(OH)2 with an efficiency that can reach 80%, and it was found that the molar ratio of Ca(OH)2 to SO3 ([Ca]/[S]) and reaction temperature have a significant effect on SO3 removal efficiency. The experimental data measured inside the EFR were analyzed with a computing fluid dynamic (CFD) simulation, in which the Euler–Lagrangian frames were used for gas- and discrete-phase modeling. The CFD models were validated and applied to analyze the effects of certain parameters on SO3 removal efficiency, such as particle velocity, [Ca]/[S], temperature and residence time. It was found that the sorbent diameter has a significant influence on SO3 removal efficiency, with an obvious decrease in efficiency if the Ca(OH)2 particle diameter increases. For example, if the sorbent d...

Sticky rice lime mortar-inspired in situ sustainable design of novel calcium-rich activated carbon monoliths for efficient SO2 capture

Abstract In the present study, a facile and eco-friendly strategy is developed for in situ conversion of waste lime mud and sawdust to valuable calcium-rich activated carbon monoliths (Ca-ACM) in the presence of sticky rice. The obtained “green hybrid bodies” can exhibit superior compressive strength of 18 MPa, water resistance for more than 60 days, and SO2 removal efficiency up to 93.6%. The SO2 adsorption capacity of Ca-ACM was evaluated to be 57.1 mg/g in a fixed bed reactor. The remarkable performance of Ca-ACM could be a result of synergetic desulfurization behaviors derived from the integrated activated carbons and Ca-based components, as well as the compact microstructure that is similar to the biomimetic mineralization system of sticky rice lime mortar. The newly developed Ca-ACM is a promising cost-effective (∼CNY 4.88/kg) alternative to comparable commercial activated carbons that can be used as a clean and ecologically compatible adsorbent for SO2 capture. The route for direct massive utilization of lime mud as an indispensable component for making functional adsorbent reported herein is very beneficial to lime mud waste recycling, SO2 pollution control, and sustainable growth of papermaking industry.

Removal of SO2 with Sodium Sulfite Solution in a Rotating Packed Bed

High efficiency and compact design of the desulfurization technology is necessary to meet the strict emission requirement of the marine environment. A rotating packed bed (RPB), having the high mass transfer efficiency and small size, is an excellent choice for SO2 removal from the flue gas in ships or warships. In this work, SO2 removal in a laboratory and a pilot RPB with sodium sulfite solution was investigated. Experimental results show that the SO2 concentration at the gas outlet of the RPB can meet the emission requirement and it has no obvious scale up effect. A correlation of the mass transfer coefficient (Kya) was proposed and the predicted Kya agrees with the experimental data with a deviation within ±12%. Compared with the spray tower, the RPB has a higher SO2 removal efficiency and a quarter volume, which displays a bright future for the offshore application of SO2 removal.

Control of H2S generation in simultaneous removal of NO and SO2 by rotating drum biofilter coupled with FeII(EDTA)

ABSTRACTSimultaneous removal of SO2 and NO from flue gas can be biologically achieved by the rotating drum biofilter with FeII(EDTA) as a solvent. One issue related with this process is the generation of H2S. To control its generation, the pathways of H2S formation were investigated, and the parametric tests were conducted. The addition of FeII(EDTA) (10 mM) increased the removal efficiency of NO and SO2, while the S2− concentration decreased from 81 to 3.5 mM. The parametric tests showed that the high NO concentration favored the SO2 removal and significantly inhibited the H2S generation. High-throughput sequencing showed that the dominant denitrifying bacteria were Pseudomonas (9.09%), and the main sulfate-reducing bacteria were Desulfovibrio (5.84%). The long-term operation confirmed that the system could effectively simultaneous perform biological denitrification and desulfurization, and the H2S could be controlled.

Photocatalytic removal of SO2 using natural zeolite modified by TiO2 and polyoxypropylene surfactant.

Air pollution due to emission of various hazardous gases such as SO2 into the atmosphere and its control is an important environmental issue. Application of photocatalysts is considered as a suitable process to control the gaseous pollutants. In this study, the efficiency of clinoptilolite as a natural zeolite (Ze) modified by TiO2 (Ze-Ti) and a polymeric surfactant polyoxypropylene (Ze-Ti-POP) for removal of SO2 was investigated. The nanocomposites were characterized by SEM, EDX, and BET analyses. The photocatalytic oxidation experiments of SO2 by the nanocomposites and natural zeolite were done under UV irradiation with initial SO2 concentration of 500ppm in a photoreactor. The effects of different factors including reaction time, catalyst dose, UV irradiation intensity, humidity content, and calcination temperature and dose of TiO2 were studied. The modification of clinoptilolite by TiO2 and POP increased considerably the BET specific surface areaof the nanocomposites. The results showed that maximum removal efficiencies of SO2 by Ze-Ti and Ze-Ti-POP under the optimum experimental conditions were 82.1 and 87.4%, respectively. Adsorption kinetics data well fitted with the Langmuir-Hinshelwood model. Moreover, reusing of nanocomposites after three regeneration cycles indicated that application of Ze-Ti and Ze-Ti-POP nanocomposites could be a promising approach for SO2 removal. Graphical abstract ᅟ.

Simultaneous Removal of SO2 and NOx from Coal-Fired Flue Gas Using Steel Slag Slurry

A method for simultaneously removing sulfur dioxide (SO2) and nitrogen oxides (NOx) from coke oven flue gas using steel slag slurry was proposed. Due to the high removal efficiency of SO2, the effects of operation conditions on the removal of NOx were investigated emphatically. The results showed that the removal efficiency of NOx increased with an increase in steel slag slurry concentration, NOx oxidation ratio, steel slag slurry pH, and NOx and SO2 inlet concentrations and a decrease in reaction temperature. The removal efficiencies of SO2 and NOx could reach 100 and 83.4%, respectively, by optimizing the operation conditions. The mechanism of NOx removal using steel slag slurry was investigated. The results showed that (MgO)0.841·(MnO)0.159 (RO phase, a CaO–FeO–MnO–MgO solid solution) in steel slag was decomposed by H+ and produced Mg2+ and Mn2+. Furthermore, Mn2+ in steel slag slurry could promote the absorption of NO2 via redox reactions with the generation of solid Mn3O4 and MnO(OH).

Challenge of SO3 removal by wet electrostatic precipitator under simulated flue gas with high SO3 concentration

Wet electrostatic precipitators (WESP) have been proven to be a promising technology for the removal of sulfuric acid mist from flue gases. Recent studies indicate that WESPs, when mitigating sulfuric acid mist, can be less effective on systems that burn high sulfur content fuel. This paper reports on a pilot-scale WESP used to investigate SO3 removal with high SO3 concentration. Both mass concentration of SO3 and number concentration of sulfuric acid mist were measured. Two key parameters, i.e., electrical characteristics and gas loading, were studied to evaluate their effects on SO3 removal efficiency under severe corona suppression conditions. Results showed that the maximum corona current was reduced by 83.1% when the WESP inlet SO3 concentration increased from 0 to 5c0, and the corresponding SO3 removal efficiency decreased from 74.5% to 54.2%. SO3 removal efficiency can be improved by increasing corona power and reducing gas velocity. A comprehensive method was proposed to enhance SO3 removal efficiency, with removal efficiencies greater than 90% using proper electrode configurations and lower velocity under a pilot plant condition. In addition, other challenges including new ultra-fine mist generation, material corrosion and insulator failure are summarized.

Simultaneous absorption–oxidation of nitric oxide and sulfur dioxide using ammonium persulfate synergistically activated by UV-light and heat

Simultaneous absorption–oxidation process of nitric oxide (NO) and sulfur dioxide (SO2) from flue gas using aqueous ammonium persulfate synergistically activated by UV-light and heat in a novel UV-impinging stream reactor was developed. The main influencing factors, products and active species of NO and SO2 simultaneous removal were studied. The mass transfer and kinetics of NO absorption–oxidation were also investigated. The present studies show that SO2 is very easy to remove because of its very high solubility in water (SO2 removal efficiencies reach 100% under most of experimental conditions). Increasing S2O82− concentration, UV radiation power, activation temperature or liquid–gas ratio promotes absorption–oxidation of NO. Increasing solution pH, concentrations of NO and SO2 or flue gas flow inhibits absorption–oxidation of NO. The contents of O2 and CO2 have no significant effect on removal of NO. The highest simultaneous removal efficiency for NO and SO2 is 96.1% and 100%, respectively. OH and SO4− are the key oxidizers for NO removal. Absorption–oxidation process of NO meets a fast pseudo-first order reaction for NO, and can be enhanced by increasing the gas-side mass transfer coefficient and interfacial area.

Combined Removal Of NOx And SO2 From Flue Gas At Low Temperature

A method was proposed to remove NOx and SO2 in flue gas by using the sulfinyl functional group as a catalyst. Ozone is introduced into the flue gas to oxidize NO. Soluble NO2 and SO2 reacted with ammonia to form ammonium sulfate and ammonium nitrate, which were the raw material of the compound fertilizer. A small pilot is built in a container that can be easily transported to power plant and extracts the actual flue gas directly from the gas duct. In order to obtain the best the SO2 and NOX removal efficiency in this experiment, many parameters were changed. Such as flue gas flow, ozone / NOX ratio, liquid-gas ratio, flue gas temperature, catalyst type, catalyst concentration, solution pH value. Results indicated that SO2 was cleaned up quite efficiently and the removal efficiency was nearly 99% under all conditions. the best NOX removal efficiency can reach 88%. The NOX removal efficiency depended primarily on ozone / NOX ratio, and the temperature of flue gas also had influence on the NOX removal efficiency. The optimum pH range is 5.6-6.3. After inspection by authoritative institutions, the quality of fertilizers is superior to national standards.

Simultaneous purifying of Hg0, SO2, and NOx from flue gas by Fe3+/H2O2: the performance and purifying mechanism.

Hg0, SO2, and NOx result in heavily global environmental pollution and serious health hazards. Up to now, how to efficiently remove mercury with SO2 and NOx from flue gas is still a tough task. In this study, series of high oxidizing Fenton systems were employed to purify the pollutants. The experimental results showed that Fe3+/H2O2 was more suitable to purify Hg0 than Fe2+/H2O2 and Cu2+/H2O2. The optimal condition includes Fe3+ concentration of 0.008mol/L, Hg0 inlet concentration of 40μg/m3, solution temperature of 50°C, pH of 3, H2O2 concentration of 0.7mol/L, and O2 percentage of 6%. When SO2 and NOx were taken into account under the optimal condition, Hg0 removal efficiency could be enhanced to 91.11% while the removal efficiency of both NOx and SO2 was slightly declined, which was consistent to the analysis of purifying mechanism. The removal efficiency of Hg0 was stimulated by accelerating the conversion of Fe2+ to Fe3+, which resulted from the existence of SO2 and NOx. The results of this study suggested that simultaneously purifying Hg0, SO2, and NOx from flue gas is feasible.

A hybrid plasma-chemical system for high-NOx flue gas treatment

The reduction of high concentrations of NOx and SO2 from simulated flue gas has been studied. Our aim was to optimise energy consumption for NOx and SO2 removal from off-gases from a diesel generator using heavy fuel oil. A hybrid process: electron beam (EB) plasma and wet scrubber has been applied. A much higher efficiency of NOx and SO2 removal was achieved in comparison to dry, ammonia free, electron beam flue gas treatment (EBFGT). A recorded removal from a concentration of 1500ppm NOx reached 49% at a low dose of 6.5kGy, while only 2% NOx was removed at the same dose if EB only was applied. For SO2, removal efficiency at a dose of 6.5kGy increased from 15% (EB only) to 84% when sea water was used as a wet scrubber agent for 700ppm SO2. The results of this study indicate that EB combined with wet scrubber is a very promising technology to be applied for removal of high concentrations of NOx and SO2 emitted from diesel engines operated e.g. on cargo ships, which are the main sources of SO2 and NOx pollution along their navigation routes.

Sulfur Dioxide Removal Using Hydrogen Peroxide in Sodium- and Calcium-Based Absorbers

This study presents the first results on comparing Na- and Ca-based absorbers for separating SO2 from flue gases in two-phase flows where the gas is modeled as a continuous phase and the absorber droplets are solved as a discrete phase. The reactions are solved as volumetric reactions where reactions are assumed to be in instantaneous equilibrium with finite rate. The results show that the Na-based absorbers have considerably higher SO2 removal efficiency compared to Ca-based absorbers. NaHCO3 is found to have the highest separation efficiency of around 96% while the lowest removal efficiency is for naturally abundant CaO. The physics behind the domination of Na-based over Ca-based absorbers is described in this work which shows that the lower activation energy and better dispersion of Na-based absorbers compared to Ca-based absorbers leads to high SO2 removal in Na-based absorbers. It is also found that the utilization of H2O2 increases the efficiency of SO2 removal for NaHCO3 to 99.8%, for CaO to 88%, a...

Experiment and Prediction Studies of Marine Exhaust Gas SO2 and Particle Removal Based on NaOH Solution with a U-Type Scrubber

Marine diesel engines produce exhaust gas including a lot of SOx and particulate matter (PM), and laws have been promulgated to regulate ship exhaust emissions. This paper proposes a U-type exhaust gas cleaning (EGC) system that is capable of removing SO2 and particulate matter (PM) simultaneously. The purpose of this study was to find the relationships between removing efficiency and parameters of EGC system, then get the optimal structural and operational parameters. The experimental results show that the SO2 absorption rate in the scrubber was mainly influenced by liquid–gas ratio, pH value, and temperature in the range of experimental operating conditions. With the system stable running, when the liquid–gas ratio and temperature were determined, the pH value must be in a fixed range of 6.5–7.5. The further research was also carried on for the EGC system applicable to ships. On the basis of SO2 removal efficiency, the prediction and experimental validation of particulate matter (PM) were studied. When ...

The Effect of Structure Modification of Sodium Compounds on the SO2 and HCl Removal Efficiency from Fumes in the Conditions of Circulating Fluidised Bed

The Effect of Structure Modification of Sodium Compounds on the SO2 and HCl Removal Efficiency from Fumes in the Conditions of Circulating Fluidised Bed

Simultaneous removal of NO and SO2 using vacuum ultraviolet light (VUV)/heat/peroxymonosulfate (PMS)

Simultaneous removal process of SO2 and NO from flue gas using vacuum ultraviolet light (VUV)/heat/peroxymonosulfate (PMS) in a VUV spraying reactor was proposed. The key influencing factors, active species, reaction products and mechanism of SO2 and NO simultaneous removal were investigated. The results show that vacuum ultraviolet light (185 nm) achieves the highest NO removal efficiency and yield of ▪ and ▪ under the same test conditions. NO removal is enhanced at higher PMS concentration, light intensity and oxygen concentration, and is inhibited at higher NO concentration, SO2 concentration and solution pH. Solution temperature has a double impact on NO removal. CO2 concentration has no obvious effect on NO removal. ▪ and ▪ produced from VUV-activation of PMS play a leading role in NO removal. O3 and ·O produced from VUV-activation of O2 also play an important role in NO removal. SO2 achieves complete removal under all experimental conditions due to its very high solubility in water and good reactivity. The highest simultaneous removal efficiency of SO2 and NO reaches 100% and 91.3%, respectively.

Eulerian-Eulerian numerical simulation for a flue gas desulfurization tower with perforated sieve trays

The CFD simulation based on the Eulerian-Eulerian model has been utilized to a small-scale Flue Gas Desulfurization (FGD) tower with perforated sieve trays. Most of the relevant studies have focused on the flow structures without the consideration of the chemical effects. In order to study the interactions between the flow structure and chemical reaction, the species transport equations of the chemical reactions have been implemented in the present study.The numerical investigation of this study includes the liquid phase distributions, streamlines of the gas phase, chemical source term, and mass fraction of SO2 gas. The complex vortical structure due to the implement of the sieve trays results in a sufficient large two-phase contact area. It also increases the number of times that the gas phase interacts with the liquid layer above the sieve trays and enhances flow mixing between regions of intense and weak chemical reactions. Correspondingly, the sieve trays can improve the SO2 removal efficiency. This study can help to carry out the numerical based optimal design of the full-scale tower in the future.

Photochemical Removal of SO2 over TiO2-Based Nanofibers by a Dry Photocatalytic Oxidation Process

Efficient and economical technologies are essential to the control of SO2, the emission of which poses serious health concerns and environmental risks. Photocatalysis is an attractive method for reducing SO2 emissions. To reduce energy consumption for excess moisture evaporation, a dry photocatalytic oxidation (DPCO) system was used instead of a traditional gas–liquid process in this study. Considering that TiO2 is a widely applied photocatalyst for the purification of gaseous pollutants, this study investigated the photocatalytic removal of SO2 over different TiO2-based nanofibers. Results show that the reduction of SO2 was mainly due to oxidation. Under ultraviolet irradiation, the removal of SO2 was enhanced by the presence of NO2, which was formed by the oxidation of NO. More interestingly, the SO2 removal efficiency remains 100% over cerium-based titania nanofibers with an increase in gas humidity, indicating that this sample has excellent resistance to H2O. This is very beneficial for application in...

Simultaneous removal of SO2 and NO from flue gas with [rad]OH from the catalytic decomposition of gas-phase H2O2 over solid-phase Fe2(SO4)3

In typical Fenton-like reaction, ferric sulfate (Fe2(SO4)3) was usually used to produce hydroxyl radical (OH) in the form of Fe3+ in aqueous solution. In this research, it was the first time that OH was obtained from the catalytic decomposition of gas-phase H2O2 over solid-phase Fe2(SO4)3 for simultaneous removal of SO2 and NO. The radical scavenger tests indicated the critical role of OH in NO removal rather than SO2 removal. The operation parameters were systematically investigated. The SO2 removal efficiency was affected by the liquid absorption, whereas the NO removal was mainly affected by the catalytic temperature, H2O2 concentration, H2O concentration and catalyst dosage. 99.8% SO2 and 92.5% NO were achieved under the operation condition where the molar ratio of H2O2 to NO was 2.5. According to the products before and after scrubbing, the removal process of SO2 and NO were speculated. NO removal experiments in NO only system and simultaneous removal system was studied, respectively. The improvement of SO2 on NO removal was elucidated by XPS characterization. SO2 and NO removal efficiencies in 12hours’ test were collected and the evolution of catalyst before and after reaction was studied using FTIR and SEM-EDX.

Reactivity of NaClO2 and HA-Na in air pollutants removal: Active species identification and cooperative effect revelation

This paper studied the yield and release of ClO2 from NaClO2 under various conditions by ultraviolet–visible spectrophotometer (UV–Vis), the existing form of HA-Na under various conditions by Fourier transform infrared spectroscopy (FT-IR), and the reactivity of chlorite/humate (NaClO2/HA-Na) in removal of SO2, NO and Hg0 under various conditions. The investigated factors included the temperature, the pH, the standing time, the coexistence gases and the anions. The results indicated that the yield and release of ClO2 were significantly affected by the cooperative effects of pH/temperature and pH/standing time. ClO2 was confirmed as an effective oxidant in the removal of NO and Hg0, and dominated the distribution of Hg2+ in NaClO2 and KCl. SO2 and NO were characterized as the promoters for oxidizing Hg0 and stabling Hg2+. The addition of Cl− decreased the removal efficiencies of SO2 and NO, but slightly increased the Hg0 removal efficiency. The best removal efficiencies of SO2, NO and Hg0 were 100%, 95.3% and 100% respectively. Based on the characterization results by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS), the removal products were determined as NaCl, humic (HA), Na2SO4, NaNO3, HgSO4, Hg(NO3)2 and HgCl2. The reaction mechanism was proposed finally.