Desulfurization System Research Articles

Biogas desulfurization under anoxic conditions using synthetic wastewater and biogas slurry

A feasibility study was conducted to determine whether aerated biogas slurry is a suitable nutrient solution for biogas desulfurization systems with a biotrickling filter. At a loading rate of 36.20 g-H2S m−3h−1, the H2S and NOx−-N removal efficiencies were 84.7% (average elimination capacity of 30.67 g-H2S m−3h−1) and 60.9%, respectively, when utilizing synthetic wastewater in a simultaneous biogas desulfurization and wastewater denitrification system. However, these efficiencies were just 61.9% (average elimination capacity of 22.42 g-H2S m−3h−1) and 49.2%, respectively, when biogas slurry was used. High-throughput sequencing revealed that the Thiobacillus and Sulfurimonas genera were the main functional bacteria. Alpha- and beta-diversity analyses showed that the H2S loading rate significantly affected the microbial community structure, especially in the system utilizing aerated biogas slurry. Finally, based on the results, we describe a feasible approach to using biogas slurry for biogas desulfurization.

선박용 탈황설비(SOx Scrubber)의 수출경쟁력에 관한 연구

선박용 탈황설비(SOx Scrubber)의 수출경쟁력에 관한 연구

Utilization of coal fly ash and bottom ash as solid sorbents for sulfur dioxide reduction from coal fired power plant: Life cycle assessment and applications

Feasibility of sulfur dioxide (SO2) reduction from a coal fired power plant using fly ash and bottom ash as solid sorbents is evaluated. The study integrates inventory data from experiments, process simulation, published studies, and real plant operation for comprehensive life cycle assessment (LCA). The experimental results exhibit the capability of free lime contained fly ash and bottom ash to react with SO2 under the least efficient conditions. The scenario-based LCA results show that fly ash/bottom ash utilization can lower the SO2 load of untreated flue gas by 3.7–4.7% before an existing wet limestone flue gas desulfurization (WFGD) system. The combined desulfurization process with SO2 reduction saves the annual energy consumption by 4.0–5.0%, the environmental impacts by 3.0–5.0%, and the annual operating cost by 3.1–4.5%, compared to the existing WFGD process. The uncertainty analysis evaluates the probability of scenarios, and the sensitivity analysis recommends the parameter variations to further improve the combined desulfurization process and possible applications of the post SO2 capture fly ash. The approach can also be applied in other coal fired power plants for more environmentally-benign WFGD operation and cleaner electricity production.

Oxidative desulfurization of dibenzothiophene using molybdenum catalyst supported on Ti-pillared montmorillonite and separation of sulfones by filtration

Cost-effective removal of refractory sulfur-containing compounds from oils is still a challenge. In this paper, a novel catalyst of molybdenum supported on Ti-pillared interlayer clay (Ti-PILC) was successfully prepared which performed well in oxidative desulfurization (ODS) with cyclohexanone peroxide (CYHPO) as oxidant under mild conditions. Performance of catalytic oxidation and removal of oxidation product were also studied. The oxidation rate of dibenzothiophene (DBT) reached 99.90% under the optimum reaction conditions. Mo/Ti-PILC catalyst showed higher activity than Mo/Na-MMT in ODS not only due to the pillared interlayer structure which contributed to better molybdenum dispersion and faster diffusion of reactants, but also the catalytic activity of titanium in the oxidative desulfurization of DBT. Oxidative product of sulfone which appeared as crystal in the model oil was filtered and sulfur concentration was reduced to below 10 mg/L. Catalytic activity would be almost unaffected after regenerating for 9 times, and the leaching of active species did not appear in the leaching experiment of the catalyst, which proved that it was real heterogeneous catalysis. Besides, kinetics data conformed to the pseudo-first-order equation pretty well. These results indicated that this desulfurization system was cost-effective for the removal of DBT from oils.

A computational fluid dynamics model of a rotary regenerative heat exchanger in a flue gas desulfurization system

Rotary regenerative heat exchangers (RHEX) are commonly used in flue gas desulfurization (FGD) systems to improve the dispersion of pollutants, reduce the visible plume, avoid liquid droplet rainout from the stack and avoid corrosion problems on the system materials. In this study, transient behaviors of heating and cooling cycles of a rotary regenerative heat exchanger in an FGD system were investigated via a 3-D computational fluid dynamics (CFD) model. For this purpose, the rotary regenerative heat exchanger was modelled using porous media approach for the heat transfer surfaces (i.e. matrix) inside the heat exchanger. A standalone channel model as used to obtain porous media parameters and heat transfer coefficient. Numerical results confirmed by published literature. Effects of different operating conditions on the performance of the heat exchanger have been investigated. In conclusion treated gas outlet temperature increases with increasing angular velocity and treated gas inlet temperature while it decreases with decreasing load. Consequently, untreated gas outlet temperature decreases with increasing angular velocity and decreases with the decreasing treated gas inlet temperature and load. By means of overall system performance it is observed that overall system performance increases with decreasing angular velocity and treated gas inlet temperature while it increases with decreasing load.

Clean power production by simultaneous reduction of NOx and SOx contaminants using Mazut Nano-Emulsion and wet flue gas desulfurization

Combustion of Mazut in power plant generates sulfur oxides (SOx) and nitrogen oxides (NOx) that need to be controlled in accordance with the European standard. Most of the pollutant removal methods are effective in removing only one contaminant but not both SOx and NOx. In this work, a combined approach is studied to simultaneously control SOx and NOx from combustion of Mazut fuel.This combined approach is consisted of the Mazut Nano-Emulsion usage instead of regular Mazut, as well as, wet flue gas desulfurization or FGD system installation. The wet FGD system removes the SOx by 80.3% but has no influence on NOx. The water content equals to by 10% of Mazut volume is used to synthesize the Mazut Nano-Emulsion at optimum performance. The dimensions of fuel droplet are in nano scale (63.7 nm in width and 123 nm in diameter). The Mazut Nano-Emulsion usage removes the NOx and SOx by 30.8% and 42.2%, respectively. The approach of Mazut Nano-Emulsion usage and wet flue gas desulfurization leads to simultaneous reduction of SOx and NOx in accordance with the European standard. Results show that the combined approach decreases the SOx and NOx 79.8% and 78.3%, respectively that satisfied the European standard.

Syntheses and ultra-deep desulfurization performance of sandwich-type polyoxometalate-based TiO2 nanofibres

The sandwich-type polyoxometalate-based TiO2 nanofibres were prepared successfully by electrospinning combining with chemical reaction and employed in ultra-deep desulfurization. OTA–CoVW–TiO2 nanofibres (OTA = CH3(CH2)17(CH3)3N, CoVW = [Co4(H2O)2(VW9O34)2]10−) confirmed the excellent desulfurization performance in extraction catalytic oxidative desulfurization system (ECODS). At 323 K, the 500 ppm DBT (dibenzothiophene) model oil was entirely removed within 20 min using 0.010 g 45 wt% OTA–CoVW–TiO2 nanofibres as catalyst when O/S molar ratio was 4:1 and the dosage of model oil was 5 mL. The catalysts could be recycled and reused at least five times without remarkable decrease in catalytic activity. The desulfurization efficiencies for different substrates were shown as following order: DBT > 4,6-DMDBT (4,6-dimethyl-dibenzothiophene) > BT (benzothiophene). Moreover, the possible mechanism was also elucidated.

Developing steady and dynamic ORP models for mercury emissions control in power plants using WFGD operating data

The oxidation-reduction potential (ORP) is highly related to Hg re-emission in wet flue gas desulfurization (WFGD) systems in coal-fired power plants. Developing an accurate model that describes the ORP characteristics is beneficial to achieve the operation optimization of the WFGD system and Hg re-emission reduction. In this paper, steady and dynamic ORP models were reported based on the least squares support vector machine (LSSVM) technique and using operating data acquired from a coal-fired power plant. For the steady model, input parameters consisted of flue gas flow, flue gas temperature, inlet SO2 concentration, oxidation air flow, recycle pump currents, and slurry feed flow. For the dynamic model, in addition to the parameters listed above, time delays of these parameters were also considered in the modeling scheme. Both models achieved high accurate predictions. Model sensitivity analysis was conducted to investigate the influence of the input parameters and time delays on ORP. Results show that the parameters are adequate to describe the characteristics of the ORP. In addition, parametric time delays play an important role to represent the dynamic characteristics of the ORP. These models can be extended to design process control strategy and conduct the ORP operation optimization of the WFGD system in power plants to mitigate Hg re-emission from the scrubber.

Improving the Catalytic Performance of Keggin [PW12O40]3- for Oxidative Desulfurization: Ionic Liquids versus SBA-15 Composite.

Different methodologies were used to increase the oxidative desulfurization efficiency of the Keggin phosphotungstate [PW12O40]3− (PW12). One possibility was to replace the acid proton by three different ionic liquid cations, forming the novel hybrid polyoxometalates: [BMIM]3PW12 (BMIM as 1-butyl-3-methylimidazolium), [BPy]3PW12 (BPy as 1-butylpyridinium) and [HDPy]3PW12 (HDPy as hexadecylpyridinium. These hybrid Keggin compounds showed high oxidative desulfurization efficiency in the presence of [BMIM]PF6 solvent, achieving complete desulfurization of multicomponent model diesel (2000 ppm of S) after only 1 h, using a low excess of oxidant (H2O2/S = 8) at 70 °C. However, their stability and activity showed some weakness in continuous reused oxidative desulfurization cycles. An improvement of stability in continuous reused cycles was reached by the immobilization of the Keggin polyanion in a strategic positively-charged functionalized-SBA-15 support. The PW12@TM–SBA-15 composite (TM is the trimethylammonium functional group) presented similar oxidative desulfurization efficiency to the homogeneous IL–PW12 compounds, having the advantage of a high recycling capability in continuous cycles, increasing its activity from the first to the consecutive cycles. Therefore, the oxidative desulfurization system catalyzed by the Keggin-type composite has high performance under sustainable operational conditions, avoids waste production during recycling and allows catalyst recovery.

Energy consumption and energy-saving potential analysis of pollutant abatement systems in a 1000-MW coal-fired power plant

ABSTRACTPollutant abatement systems are widely applied in the coal-fired power sector, and the energy consumption is considered an important part of the auxiliary power. An energy consumption analysis and assessment model of pollutant abatement systems in a power unit was developed based on the dynamic parameters and technology. The energy consumption of pollutant abatement systems in a 1000-MW coal-fired power unit that meets the ultra-low emission limits and the factors of operating parameters, including unit load and inlet concentration of pollutants, on the operating power were analyzed. The results show that the total power consumption of the pollutant abatement systems accounted for 1.27% of the gross power generation during the monitoring period. The wet flue gas desulfurization (WFGD) system consumed 67% of the rate, whereas the selective catalytic reduction (SCR) and electrostatic precipitator (ESP) systems consumed 8.9% and 24.1%, respectively. The power consumption rate of pollutant abatement systems decreased with the increase of unit load and increased with the increase of the inlet concentration of pollutants. The operation adjustment was also an effective method to increase the energy efficiency. For example, the operation adjustment of slurry circulation pumps could promote the energy-saving operation of the WFGD system.Implications: The application of pollutant abatement technologies increases the internal energy consumption of the power plant, which will lead to an increase of power generation costs. The real-time energy consumption of the different pollutant abatement systems in a typical power unit is analyzed based on the dynamic operating data. Further, the influence of different operating parameters on the operating power of the system and the possible energy-saving potential are analyzed.

Efficient Oxidative Desulfurization Processes Using Polyoxomolybdate Based Catalysts

This work proposes an efficient desulfurization system to produce low sulfur diesel under sustainable and moderate experimental conditions. Treatment of a real diesel with a sulfur content of 2300 ppm led to 80% desulfurization after 2 h. The processes used conciliate liquid-liquid extraction and sulfur oxidative catalysis. The catalytic performance of the commercial Keggin-polyoxomolybdate H3[PMo12O40] (PMo12) was strategically increased by simple cation exchange, using a long carbon chain (ODAPMo12, ODA = CH3(CH2)17(CH3)3N), and by its incorporation into the Metal-Organic Framework (MOF) NH2-MIL-101(Cr), forming a new active heterogeneous PMo12@MOF composite catalyst. Activity of both catalysts was similar; however, the solid catalyst could be easily recovered and reused, and its stability was confirmed after multiple continuous cycles.

Nickel Sulfides Decorated SiC Foam for the Low Temperature Conversion of H₂S into Elemental Sulfur.

The selective oxidation of H2S to elemental sulfur was carried out on a NiS2/SiCfoam catalyst under reaction temperatures between 40 and 80 °C using highly H2S enriched effluents (from 0.5 to 1 vol.%). The amphiphilic properties of SiC foam provide an ideal support for the anchoring and growth of a NiS2 active phase. The NiS2/SiC composite was employed for the desulfurization of highly H2S-rich effluents under discontinuous mode with almost complete H2S conversion (nearly 100% for 0.5 and 1 vol.% of H2S) and sulfur selectivity (from 99.6 to 96.0% at 40 and 80 °C, respectively), together with an unprecedented sulfur-storage capacity. Solid sulfur was produced in large aggregates at the outer catalyst surface and relatively high H2S conversion was maintained until sulfur deposits reached 140 wt.% of the starting catalyst weight. Notably, the spent NiS2/SiCfoam catalyst fully recovered its pristine performance (H2S conversion, selectivity and sulfur-storage capacity) upon regeneration at 320 °C under He, and thus, it is destined to become a benchmark desulfurization system for operating in discontinuous mode.

Distribution and leaching characteristics of heavy metals in a hazardous waste incinerator

In this study, distribution and leaching characteristics of heavy metals (As, Cd, Cr, Cu, Pb, Se, Zn, and Hg) along flue gas cleaning systems were investigated in a hazardous waste incinerator located in Zhejiang, China. The particle size distribution, heavy metal loading, and morphological and mineralogical characteristics of solid incineration residues were assessed before and after acetic acid extraction. Results showed that Hg, Cd, As, Pb, and Zn were transmitted into the fly ash mainly by evaporation, condensation, and adsorption, while Se and Cr were mainly by entrainment. High chlorine availability in the industry hazardous waste favored the evaporation of Cu, Pb and Zn. Due to the mass ratio of the bottom slag in the incineration residues being more than 52%, most of Cu, Cr, As, and Zn remained in the bottom slag. Scarcely any Hg and less than 9.6% of Cd were found in the bottom slag. Cd was mainly retained in the fly ash and the absorbent solution of the wet flue gas desulfurization (WFGD) system while most of Pb was found in the fly ash. WFGD system had a high Hg removal efficiency and more than 74.7% of Hg was retained in the absorbent solution of WFGD system. The distinction in the distribution and migration characteristics of heavy metals between two continuous operating conditions was mainly due to the different physicochemical properties of wastes. The studied heavy metals in the bottom slag, with the exception of Zn, showed low leachability, with a leaching ratio below 2%. Cd and Zn presented the highest leachability, and over 56.2% of Cd and more than 39.5% of Zn in the fly ash were transferred into the leachate. For the each studied heavy metal, the leaching ratio in the bag filter ash was the highest.

TEM study the corrosion behavior of the low alloy steels developed for flue gas desulfurization system

This study investigated the corrosion behavior and underline mechanisms of low alloy steels with a minor addition of 0.4 wt% Cu, 0.2 wt% Ni, 0.1 wt% Sb and 0.05 wt% Co developed for a flue gas desulfurization (FGD) system. Corrosion tests were carried out in an aggressive solution of 16.9 vol% H2SO4 + 0.35 vol% HCl + Bal. H2O at 60 °C for up to 48 h. The experimental results revealed enrichment of the additional elements (Cu, Sb and Ni) in the corrosion layer, whose concentration increased with test time. As the concentrations of Cu increased, the crystallization and growth of the Cu particles (from several nm to 320 nm)) within the corrosion layer was accelerated. At the initial stage of the test, a continuous amorphous layer rich with the additional elements formed and covered the surface of the steel, which then gradually developed defects, pores and cracks, as the crystallization and growth of Cu particles with the elapse of time. The results indicated that the corrosion resistance of the low alloy steel depends on the existence form of Cu in the corrosion layer, i.e., as solute atoms or as nanoparticles strengthened the corrosion layer and increased corrosion resistance. As the coarsening of Cu particles weakened the corrosion layer and deteriorated the corrosion resistance.

Sulfur abundant S/FeS2 for efficient removal of mercury from coal-fired power plants

Sulfur abundant S/FeS2 prepared by a hydrothermal method was employed for removing elemental mercury (Hg0) from coal-fired flue gas at low temperature. The S/FeS2 exhibited optimal Hg0 adsorption performance at 80 °C, which matched the temperature window between the flue gas desulfurization (FGD) and wet electrostatic precipitator (WESP) systems. The adverse effects of H2O and SO2 on Hg0 adsorption were slight. The Hg0 adsorption capacity of S/FeS2 was up to 2732 μg/g when achieved 50% breakthrough threshold. Both elemental sulfur (S) and FeS2 in the S/FeS2 contributed to the excellent Hg0 adsorption capacity. The mercury leaching tests show that only 0.00076% mercury adsorbed on the S/FeS2 was leached out. The mercury concentration in leachate was 0.694 μg·L−1, which was much lower than that for a commercial AC (1.214 μg·L−1). Furthermore, the S/FeS2 presented about 95% oxidized mercury (Hg2+) adsorption efficiency from WESP effluent. The Hg2+ concentration could decreased rapidly from 50 μg·L−1 to below 2.5 μg·L−1 in 30 min, which was much lower than the World Health Organization (WHO) guideline (6 μg·L−1). With these advantages, S/FeS2 appears to be a promising material for co-beneficial gaseous Hg0 and aqueous Hg2+ removal from power plants by injecting upstream of a WESP system.

Characteristics and Inhibition of Hg0 Re-emission in a Wet Flue Gas Desulfurization System

Characteristics of Hg0 re-emission in a wet flue gas desulfurization (WFGD) system were investigated on the basis of a bubble column. Five addition agents were used to inhibit Hg0 re-emission and improve removal of gaseous mercury. The results show that SO32– plays an important role in Hg0 re-emission in a WFGD system. Hg0 re-emission is intensified sharply in the presence of SO32– and further intensified with the increase of the SO32– concentration. Hg0 re-emission is strengthened at a higher temperature of desulfurization slurry. However, the removal efficiencies of both Hg2+ and total gaseous mercury decrease significantly with an increasing slurry temperature. The decreasing amplitude of total mercury removal efficiency is slightly higher than that of Hg2+. In addition, the re-emission rate of Hg0 declines first and then increases with an increasing pH value. A least Hg0 re-emission is observed at a pH value of 5.5. Fenton reagent, NaClO, K2S2O8, Na2S, and ethylenediaminetetraacetic acid (EDTA) can in...

Elimination of hydrogen sulfide from biogas by a two-stage trickling filter system using effluent from anaerobic–aerobic wastewater treatment

This study presents a two-stage desulfurization system based on two trickling filters (TFs): a first-stage closed-type TF (1st TF) and an open-type second-stage TF without aeration (2 nd TF). The effluent from an anaerobic–aerobic wastewater treatment system served as the water source, and coconut chips were used as the packing media for both the TFs. The concentration of hydrogen sulfide in the biogas ranged from 80 to 2300 ppm (v/v) with an average concentration of 737 ppm. The 1st TF eliminated more than 99% of the hydrogen sulfide at a loading rate of 5.24 gS–H2S m−3 h−1. Subsequently, 50.0% of the eliminated hydrogen sulfide was oxidized to sulfate in the 2 nd TF without aeration. The two-stage TF system additionally eliminated 53.1% of ammonia from among which 52.6% was detected as nitrate in the effluent of the 2 nd TF. Additionally, 9.2% of the total nitrogen was eliminated by the 2 nd TF. These results indicate that some of the dissolved sulfide was oxidized to elemental sulfur and/or thiosulfate; further, and sulfur-based autotrophic denitrification was observed to occur in the 2 nd TF. Therefore, this two-stage TF system can be employed as a low-cost desulfurization system to perform biogas purification and nitrogen elimination.

Oxidative desulfurization of dibenzothiophene and diesel by hydrogen peroxide: Catalysis of H3PMo12O40 immobilized on the ionic liquid modified SiO2

Here we reported an oxidative desulfurization system for oxidation of sulfur-containing compounds in model oil and diesel by catalysis using SiO2-supported phosphomolybdate hybrid material with 30% H2O2 aqueous solution as the oxidant. Firstly, The SiO2 was modified with 1-propyl-3-triethoxysilyl 3-methylimidazolium chlorid by grafting method. We used the 29Si MAS NMR to demonstrate that the organic silane group was attached to the SiO2 surface by one or two SiOSi bonds. Secondly, the phosphomolybdate was immobilized onto the modified SiO2 to prepare the hybrid material catalyst. The FT-IR, UV–vis, and TG characterization results indicate that the Keggin structure of the [PMo12O40]3− and imidazole ring were remained. The catalyst was used to oxidative desulfurization of dibenzothiophene by H2O2 as the oxidant. Maximum oxidation activity was observed at a loading of 30 wt.% H3PMo12O40 which can complete oxidation 0.2 wt.% of dibenzothiophene at 50 °C and an O/S molar ratio of 3.0 in 30 min. The catalyst could be easily separated by centrifugation and reused for seven times without any deactivation. The high performance of this oxidative desulfurization system was verified in the sulfur removal from a real diesel oil by oxidation followed by dimethylformamide extraction.

Experimental Study on Removal Characteristics of SO3 by Wet Flue Gas Desulfurization Absorber

This paper reports a study on the simultaneous removal characteristics of SO3 in a wet flue gas desulfurization (WFGD) system. The impacts of the operating parameters, including liquid-to-gas (L/G) ratio, inlet SO3 concentration, flue gas temperature, superficial velocity, and slurry temperature, on the SO3 removal efficiency and SO3 aerosol characteristic were studied. Results showed that the overall SO3 removal efficiency varied from 20% to 55% under the experimental conditions. For the SO3 aerosol, particles measuring 0.5 μm had a higher removal efficiency, whereas particles measuring 0.1–0.5 μm were relatively difficult to remove in the WFGD system. Increases in L/G ratio and SO3 concentration exerted positive effects on the SO3 aerosol capture, whereas superficial velocity, flue gas temperature, and slurry temperature had negative effects. After installing a sieve plate, the SO3 removal efficiency increased from 49.88% and 53.46% to 51.77% and 58.05%, respectively, under two typical cond...

안내깃 형상에 따른 배연탈황 시스템 배관 내 유동 특성에 관한 전산수치해석

안내깃 형상에 따른 배연탈황 시스템 배관 내 유동 특성에 관한 전산수치해석