SO2 Removal Research Articles

Robust 4d-5f Bimetal-Organic Framework for Efficient Removal of Trace SO2 from SO2/CO2 and SO2/CO2/N2 Mixtures.

Herein, we report a highly rare robust 4d-5f bimetal-organic framework that shows high porosity and thermal/chemical stability and thus is capable of removing trace SO2 from a SO2/CO2/N2 mixture even under humid conditions. This work not only shows a novel adsorbent for SO2 removal but also extends the function of actinium-based coordination compounds.

SO2 Absorption by Multiple Biomass Ash Types.

As the severity of environmental pollution continues to increase and ultralow emission standards are proposed, biomass power plants must implement additional processes to control SO2 emission. Biomass ash can be utilized as a sorbent for flue gas desulfurization because of its strong alkalinity. In this study, the characteristics of SO2 absorption in simulated flue gas using four types of typical biomass ashes were studied in fixed bed experiments. The results showed that the addition of water, the increase in water vapor, and the lower temperature were beneficial for SO2 absorption. The main components of wheat straw ash are KCl and SiO2, cotton stalk ash is rich in K2O and calcium compounds, poplar bark ash has a considerable content of calcium compounds, and corncob ash contains large amounts of KCl and K2O. Alkali substances, such as oxides or carbonates of potassium and calcium, play a crucial role in SO2 absorption. The SO2 removal effect of corncob ash was the best owing to the abundance of potassium oxides. Meanwhile, wheat straw ash performed worst in SO2 removal due to the small amount of K2O and Ca. The desulfurization products were mainly potassium and calcium sulfate.

Techno-economic assessment of carbonate melt flue gas desulfurization process

Sulfur dioxide (SO2) is a pollutant that is mainly emitted in thermal coal-fired power plants, and it causes air pollution, which is required to be removed since it adversely affects the atmosphere environment. This study presents a novel approach to remove SO2 using carbonate melt by designing a flue gas desulfurization (FGD) process that uses a carbonate melt desulfurization (CMD) subsystem to remove >99.9 wt% of SO2 and a carbonate melt regeneration (CMR) subsystem that recovers ~99 wt% of the melt. To reduce the operating costs of the proposed process, a heat-exchanger network was developed to use the waste heat that existed in the process. The levelized cost of the proposed FGD process using carbonate melt was determined as US$ 761/ton SO2 removed and is therefore cost-competitive with other SO2 removal technologies. Sensitivity analysis indicates that coal price is the main driver of levelized cost.

Design and evaluation of a novel system for the flue gas compression and purification from the oxy-fuel combustion process

The process of flue gas compression and purification is essential for oxy-fuel combustion, because of its significance in determining the quality of the CO2 product. Based on the difference of dew points between CO2 and acid contaminants, a novel system, which integrated the partial CO2 recirculation with the flue gas purification, was proposed and evaluated in this study. The simulation results confirmed that a CO2 stream with a purity of 99.9% could be achieved, and the distillate after treatment in SO2 and NO absorbers could be directly recycled back to the boiler. The performance of CO2 recovery was enhanced by elevating the condensing pressure to 3.0–4.0 MPa. Besides, there was a critical ratio between the recycled CO2 liquid and the raw flue gas for the abatement of contaminants, which was 11.0 L/m3. Furthermore, the performances of SO2 and NO removal were investigated. The efficiencies of SO2 and NO abatement could be more than 99% when the reaction pressures were 0.5 MPa and 1.5 MPa separately. Besides, a critical molar ratio of SO2 to NO in the raw feeding flue gas was determined, and the removal of SO2 was restrained when the SO2/NO molar ratio increased over the critical point. As for the NO abatement, the continuous re-oxidation of NO released from the dissociation of HNO2 was dominant in the NO absorber, and the performance of NO removal was dramatically enhanced with the presence of NO pre-oxidation at low reaction pressures.

Removal of Hg0, NO, and SO2 by the surface dielectric barrier discharge coupled with Mn/Ce/Ti-based catalyst.

In this study, power parameters (power, frequency, and voltage), initial Hg0 concentration, and residence time are investigated for the removal of the increased Hg0 concentration via surface dielectric barrier discharge (SDBD). The synergistic effect of a Mn/Ce/Ti catalyst with SDBD is verified with a mixture of flue gas (Hg0, NO, and SO2). Results show that Hg0 oxidation efficiency has an optimal frequency, which declines as the input voltage increases. The amplification of the Hg0 removal efficiency decreases as voltage increases. The effect of the initial Hg0 concentration gradually decreases as the peak voltage increases. The residence time slightly affects the Hg0 removal efficiency at a high peak voltage. The cooling water temperature behaves differently on Hg0 oxidation under high and low voltages. X-ray photoelectron spectroscopy (XPS) reveals the relative atomic concentrations of Mn2+ and Mn3+ in the Mn-TiO2 and Mn-Ce-TiO2 catalysts are 66.84% and 65.80%, respectively, which indicate that Ce addition will not affect surface Mn. Mn has a limited catalytic action on the removal of flue gas with and without SDBD. Nevertheless, SDBD can stimulate the oxygen storage capacity of Mn to increase the NO2 conversion rate. Mn-Ce-TiO2 greatly improves the removal efficiencies of NO and SO2 because of the existence of the redox pairs of Mn4+/Mn3+, Ce4+/Ce3+, and Ti4+/Ti3+. However, the three catalysts slightly differ on Hg0 removal when combined with SDBD, indicating that the effect of the catalyst was weakened after SDBD was added.

Comparative Study of the Effects of Various Activation Methods on the Desulfurization Performance of Petroleum Coke

In this study, we activated different samples of petroleum coke, an economical carbonaceous substance with great potential as an activated carbon material for the removal of SO2, via six common methods, viz., hydrothermal, high-temperature, acid-based, alkali-based, H2O2-based and Cu2+-based treatment, and evaluated the desulfurization efficiency of each sample by investigating the dynamic SO2 adsorption along with various relevant factors. We found that high-temperature activation modified the structure and chemical properties of the petroleum coke, leading to an initial desulfurization efficiency of 76.4%, with a specific surface area of 59.0 m2 g–1, whereas acid-based treatment increased the SO2 removal rate to above 82%, producing a specific surface area as high as 247.7 m2 g–1. However, alkali-based treatment applied at a KOH/coke ratio of 4:1 achieved the best performance, with a desulfurization efficiency of 96.3% under the optimal conditions. Further comparison of the activated samples’ physicochemical properties revealed that both an optimized texture (due to the change in pore structure) and an increased number of active sites contributed to the enhanced desulfurization. Thus, our results demonstrate that activated petroleum coke exhibits several favorable properties that make it a promising sorbent for acidic SO2 in industrial flue gas desulfurization.

Experimental Investigation of Simultaneous Removal of SO2 and NOx Using a Heteropoly Compound

ABSTRACT Aiming at developing a simple, feasible method for SO2 and NOx removal, in this work, various doping amounts of heteropolyacid and heteropolyacid salts were prepared and used in wet absorption for simultaneous removal of SO2 and NO. The desulfurization and denitrification performance was evaluated by investigating dynamic SO2 and NO absorption in a simulated reactor containing a heteropoly compound (HPC) solution along with various factors influencing the reaction. The results demonstrate that this system had a high removal efficiency of SO2 and modest NO removal. The amount of Wolfram (W) doping and the pH of the solution affecting the removal performance was studied, and a stable SO2 removal efficiency higher than 95% was obtained for HPW1Mo at a pH value of 5.5. In addition, the desulfurization performance of NaPWMo with a 50% removal efficiency was higher than that of the HPWMo solution (20%) after a 60 min reaction time. A high concentration of the NaPWMo solution and the presence of O2 were beneficial to desulfurization at room temperature. In addition, the removal efficiency of SO2 or NO by NaPWMo was only affected by its own gas concentration rather than their mutual influences on each other. This work should be beneficial to the optimization leading to the development of simultaneous desulfurization and denitrification systems in practical applications.

Effect of seawater alkalinity on the performances of a marine diesel engine desulphurization scrubber

Since the last fifteen years, Flue Gas Desulphurization (FGD) plants based on seawater scrubbing found an interesting application in the maritime transportation, as an answer to the stringent regulations imposed by International Maritime Organization (IMO) on sulphur emissions. This work reports the experimental results on desulphurization in a pilot seawater scrubber (DN 400) from a marine Diesel engine (80 kW) operated under different loads (10, 25 and 50%). The pilot scrubber was fed with a gas velocity 0.15 m/s and a liquid to gas mass ratio 1-3 kg/kg. The scrubbing liquid was available at different alkalinity and salinity levels representing the ion speciation of marine water in different geographic areas. The experiments evaluate the SO2 removal efficiency of the scrubber as a function of seawater alkalinity and pH. Finally, the paper reports a correlation to assess the seawater flow rate required to comply with the current IMO restrictions. This correlation allows tuning the seawater flow rate during the ship navigation based on the registered marine alkalinities and to the operating conditions of the engine. The model can be integrated in the scrubber control system to identify optimal operating conditions and reduce pumping costs, helping to reduce the EEDI and the SEEMP ships energy indexes.

Study on SO3 emission test of typical ultra-low emission coal-fired units in western region of Inner Mongolia

To study the effect of types of boilers, pollutant treatment facilities and coal quality on SO3, emission concentration of SO3 was tested by controlled condensation method for seven typical ultra-low emissions coal-fired units in western region of Inner Mongolia. The test results showed that the SO3 emission concentration of all units ranged from 0.36 mg/m3 to 2.04 mg/m3, much lower than 5 mg/m3, so there was no need to add SO3 removal facilities. For the units burning the coal of same sulfur content, which adopt LLTESP and WESP has the lower SO3 emission concentration. The SO3 emission concentration can also be controlled at a lower value when SNCR and double-tower double-cycle WFGD technology are adopted in the unit burning medium-high sulfur coal.

Condensational growth activated by cooling method for multi-objective treatment of desulfurized flue gas: A full-scale study

The desulfurized flue gas from coal-fired power plants is discharged with pollutants and a lot of heat and water vapor into the environment. To synchronously reduce the pollutant emission and recover the heat and water, a novel technology was proposed and applied in a coal-fired power plant after experimental and pilot studies. The technology, referred to as phase transition agglomeration system (PTAS), was developed based on condensational growth and subsequently enhanced removal of particles and droplets under supersaturated conditions. Unlike existing research, the supersaturation here is produced by cooling the desulfurized flue gas through an appropriate approach, which is more feasible for industrial application. Meanwhile, heat and water are recovered. Field measurements were conducted to study its performance. Particle removal efficiencies of the full-scale PTAS were 53.05% and 71.11% at 90% and 75% loads, respectively, and the emission concentrations were reduced to below 5 mg/m3. SO3 removal efficiency was nearly 20% at the initial concentration of ~2.9 mg/m3. >87% of the heat released by the flue gas and over 83% of the condensate were recovered. The recovered heat was utilized directly to heat the feed water of boiler, and the recovered water could be used to replenish the desulfurization slurry after alkali treatment. The heat and water recovery rates were up to 3.59 MW and 4.32 t/h, respectively, which improved the economics of the power plant. The good performance of PTAS in particle and SO3 removal, together with heat and water recovery, was demonstrated in this full-scale study, and worthwhile data and experiences were provided for the development of such technologies for further treatment of coal-fired flue gases.

Promotion of manganese extraction and flue gas desulfurization with manganese ore by iron in the anodic solution of electrolytic manganese

In this work, Mn ore was mixed with the wastewater anode solution of electrolytic Mn (ASEM, instead of water) and utilized as the desulfurizer for simultaneous SO2 removal from flue gas and Mn extraction. The effects of Fe2+ and Fe3+ on Mn leaching and flue gas desulfurization were investigated. For MnO2 and Mn2O3 (mixed with ASEM), the introduction of Fe2+could simultaneously increase Mn extraction efficiency and flue gas desulfurization efficiency when MnO2 and Mn2O3 mixed with ASEM was used. Fe3+ addition could improve desulfurization efficiency obviously for MnCO3. Fe2+ could react with MnO2 and H+ to form Mn2+ and Fe3+. This reaction further improved Mn extraction and simultaneously decreased the acidity of ASEM, thus promoting SO2 removal. The introduced Fe3+ could react with SO2, when MnO2 was absent from the desulfurizer slurry. The resulting Fe2+ was then oxidized by O2 to form Fe3+, which underwent a Fe3+ ↔ Fe2+ cycle to promote flue gas desulfurization. Thus, the introduction of Fe ions, especially Fe2+, could promote simultaneous Mn leaching and flue gas desulfurization with Mn ore. This work provided not only a new way for effective SO2 removal from flue gas and Mn extraction but also for recycling ASEM.

Constructing superhydrophobic surface of PES/PES-SiO2 mixed matrix membrane contactors for efficient SO2 capture

Obtaining high SO2 absorption flux for membrane contactor is noticeably vital for fule gas desulfurization, and superhydrophobic surface is essential to reach excellent desulfurization performance. The development of a generic and low budget strategy for membrane contactors preparation is important in indisturial application. In this study, a superhydrophobic polyethersulfone-silica (PES/PES-SiO2) gas-liquid membrane contactor is fabricated using a facile spin coating method. PES substrate is prepared by a facile non-solvent induced phase separation (NIPS), and then the superhydrophobic surface of PES/PES-SiO2 is formed on the PES substrate by spin coating method. The solubility parameters of mixed solvent, PES concentration, and SiO2 content are regulated to investigate the morphology of membrane contactors. On one hand, the surface structure of MMMCs is regulated, and constructs lotus-leaf like morphology, which noticeably elevate surface roughness. On the other hand, SiO2 nanoparticles enhance hydrophobic characteristic with water contact angle 159° and anti wetting resistance with liquid entry pressure of water (LEPw) 1.389 bar. Moreover, the SiO2 nanoparticles help to significantly improve the stability of desulfurization performance, which is much higher than PES control membrane after 12 h test. The SO2 absorption fluxes and SO2 removal efficiencies are 1.24 × 10−3 mol·m−2·s−1 and 63.8%, respectively. Besides, the membrane phase transfer coefficient (Km) and membrane phase transfer resistance (H/Km) are explored.

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.

Preparation of powdered activated coke for SO2 removal using different coals through a one-step method under high-temperature flue gas atmosphere

Powdered activated coke (PAC) used for SO2 adsorption can be prepared using pulverized coal through a one-step method under a high-temperature flue gas atmosphere, and the PAC performance is significantly affected by the coal type. In this study, five coals with different ranks were used to prepare the PACs through this method in a drop-tube reactor. The pore structures, bulk densities, surface morphologies, and chemical functional groups of the PACs were characterized, and their yields and SO2 adsorption capacities were determined. Results show that the PACs prepared from low-rank coals (IN-coal and ZD-coal) had developed pore structures, abundant oxygen-containing functional groups and high SO2 adsorption capacities, but their yields were relatively low. As the degree of coalification increased, as in JJ-coal and RU-coal, the pore structure parameters, amount of oxygen-containing functional groups, and SO2 adsorption capacities of the PACs demonstrated a decreasing trend, whereas the yields increased. Besides, the XW-coal was found to be unsuitable for PAC preparation, because the resulting PAC had an undeveloped pore structure and a low SO2 adsorption capacity, and caking property of coal is an unfavorable factor in the PAC preparation. These conclusions can provide guidance for the selection of raw materials used to prepare PAC through the one-step method.

Application of BP neural network models in predicting the desulfurization rate of petroleum coke calcination flue gas

Sulfur-containing prebaked anodes, mainly made from petroleum coke, can give rise to SO2 emission in the production of electrolytic aluminum. In order to study the correlation between the emission volume and desulfurization rate of the flue gas discharged from the calcination of petroleum coke, a traditional double hidden layer BP neural network model was established on the basis of BP neural network by taking the emission data of the petroleum coke calcination flue gas desulfurization system as input parameters. This model was used to predict the desulfurization rate of the petroleum coke calcination flue gas desulfurization system, with an aim to control the SO2 removal rate of flue gas through controlling the flue gas parameters of the desulfurization system, so as to reduce SO2 emission from the flue gas of the electrolytic aluminum industry. The study will be of practical significance for the SO2 removal of the petroleum coke calcination flue gas.

Analysis of Particulates and SO2 Removal from Coal Combustion Emissions Using Cyclone and Wet Scrubber With Textile Wastewater Feed

Reuse of wastewater in the industry is mostly accomplished for watering plants. In a closed cycle, however, industrial wastewater can be returned through treatment to save water usage. This study aims to analyze textile wastewater's ability to be used as scrubbing liquid in the SO2 gas and particulate removal from coal combustion using a packed wet scrubber. Usually, the textile industry uses boiler fueled by coal and discharging base/alkaline wastewater. The method is carried out experimentally using a prototype device using a combination of cyclone and scrubber, with a source of coal combustion gas emissions. We did experiments using textile wastewater four times and two times using clean water as a control. We monitor the SO2, particulate emission in the gas stream, and pH, sulfate levels, and TSS levels in collected wastewater according to SNI. SO2 gas and particulates from coal combustion will be absorbed by the scrubber's wastewater spray so that SO2 will dissolve into sulfate, particulate matter into TSS. The study results using textile wastewater showed the removal efficiency of particulates on cyclone by 34-78%. The removal efficiency of SO2 on wet scrubber was only 24.7%. There was an increase in TSS levels after passing through the scrubber by 46%. The rise in TSS and sulfate concentrations in the wastewater indicates the absorption of SO2 and particulates into wastewater. Based on this result, we can use textile wastewater for controlling the emission of SO2 and particulate from coal combustion by feeding it for the scrubber. However, the efficiency of this process is not optimal.

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.

Novel product-adjustable technology using Wellman-Lord method coupled with sodium-alkali for SO2 removal and regeneration from smelting gas

A product-adjustable method for desulfurization and regeneration was proposed in this study. Two stages of SO2 absorption combined the sodium-alkali and Wellman-Lord methods. The products could be recycled as valuable pure SO2, H2SO4, or Na2SO3. The absorption characteristic and the regenerative behavior with Na2SO3 solution were investigated. The influences of various temperatures, oxygen concentration, and absorbent concentration in SO2 removal were studied respectively. Na2SO3 exhibited SO2 removal efficiency higher than 99% and maintained it with the temperature range of 25–60 °C. Oxidation of Na2SO3 harmed its absorption ability. Ascorbic acid realized good oxidation inhibition effect with concentration less than 0.1%. The utilization rate of Na2SO3 remained nearly 100% at different concentrations. Meanwhile, desorption of saturated absorbent (mainly NaHSO3) was studied. The desorption proportion rose with the increasing concentration of HSO3- while slightly changing with desorption temperature. Ascorbic acid could raise SO2 regeneration concentration higher than 2.5%. Part of NaHSO3 could be regenerated to release high-concentration SO2 and fully used in further absorption. The system showed good regeneration performance for at least 4 rounds and stabilized then. Therefore, the improved regeneration technology realized the reuse of Na2SO3 and the recycling of pure SO2.

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.

Insights into the effect of regeneration temperature on physicochemical properties and SO2 removal over powdered activated coke

Porous carbon materials have emerged as a new technology with tremendous potential as energy-saving and environmentally friendly pathways for SO2 removal due to its advantages, which include recyclability and a high adsorption capacity. However, the degradation of the performance of adsorbents using thermal regeneration has become a key issue limiting the scaling-up of this new technology. The main purpose of this study is to clarify the effect of the regeneration temperature on the physicochemical properties of activated coke and secondary SO2 removal performance, as well as explore the mechanism by which the circulating adsorbent is deactivated. Using powdered activated coke (PAC) prepared from coal. Experimental results show that adsorbed SO2 desorbs at temperatures between 200 and 500 ℃, while both excess CO2 and CO are released over a wide temperature range owing to the regeneration reaction and decomposition of newly formed oxygen-containing functional groups. The physicochemical properties of PAC are significantly affected by the regeneration temperature. As this temperature rises, the adsorbed sulfuric acid in the pores evaporates and the functional groups decompose, producing several micropores and a large specific surface area. Moreover, the SO2 adsorption–desorption process increases the number of C–O groups such that the active adsorption sites are occupied and SO2 adsorption is prevented. The C-O groups decompose to produce CO2 when exposed to even higher temperatures. The secondary SO2 adsorption experiment demonstrated that the ability of the adsorbent to perform desulfurization could be recovered completely by controlling the regeneration temperature.