SO2 Removal Efficiency Research Articles

Insights into Coproduction of Silica Gel via Desulfurization of Steel Slag and Silica Gel Adsorption Performance.

Steel slag is a calcium-containing alkaline industrial solid waste that can replace limestone for flue gas desulfurization. It can remove SO2 and coproduce silica gel while avoiding CO2 emission from limestone in the desulfurization process. In this study, steel slag with a D50 of 3.15 μm was used to remove SO2. At room temperature, with a solid–liquid ratio of 1:10, a stirring speed of 800 rpm, and the mixed gas introduced at a flow rate of 0.8 mL/min, 1 ton of steel slag could remove 406.7 kg of SO2, a SO2 removal efficiency typical of existing calcium-rich desulfurizers. As limestone desulfurization can release CO2, when limestone desulfurization was replaced with steel slag of equal desulfurization ratio, CO2 emissions could be reduced by 279.6 kg and limestone could be reduced by 635.5 kg. The yield of silica gel was 5.1%. Silica gel pore structure parameters were close to those of commercially available B silica gel. Products after desulfurization were mainly CaSO4·2H2O, CaSO4·0.5H2O, CaSO3·0.5H2O, and silica gel. With a silica gel dosage of 30 mg, a temperature of 20 °C, a pH value of 6.00, a stirring time of 0.5 h, and a methylene blue concentration of 0.020 mg/mL, the removal ratio of methylene blue adsorbed by silica gel was 98.4%.

Enhancement of citric acid on low-grade limestone wet desulfurization performance coupled with spray and partial bubble technology

Developing low-grade limestone as absorbents has been recognized as a prerequisite for industrial application of wet flue gas desulfurization (WFGD) due to the serious depletion of high-grade limestone for SO2 capture. In this research, citric acid was utilized as additive in order to improve the SO2 removal efficiency of low-grade limestone. The enhancement of citric acid on desulfurization performance and the effects of citric acid concentration were investigated based on the spray and partial bubble technology. The results show that the addition of citric acid into low-grade limestone slurry can significantly improve the desulfurization efficiency and the optimal blending ratio between citric acid and low-grade limestone was 1:5. The spent absorbents and reacted liquid phase products were analyzed by X-Ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ion chromatography (IC) and inductively coupled plasma luminescence spectrometry (ICP-OES). These characterizations illustrated that the oxidation of SO32− into SO42− ions along with formation of gypsum was inhibited in the presence of citric acid because of its strong reducibility, whereas the reaction between SO2 and SO32− was greatly promoted, leading to the high SO2 removal efficiency. Furthermore, molecular dynamics (MD) calculation was conducted to provide the microscopic information including the self-diffusion and hydration behavior of SO2 and the gas-liquid interface microstructure. These investigations are of significant importance in providing enhancement mechanism of citric acid on low-grade limestone WFGD process.

Integrated on-site collection and off-site analysis of airborne molecular contamination in cleanrooms for integrated circuit manufacturing processes

Both long-term on-site collection and off-site analysis methods were conducted to investigate airborne molecular contaminants (AMCs) in a semiconductor wafer cleanroom. The removal efficiency of SO2 and NO2 for chemical filters on a make-up air unit (MAU) in the cleanroom is approximately 50%, though this value does not meet the removal efficiency mentioned in the GB 36306 standard. The removal efficiencies of SO2, H2S, NO, NO2, NH3, and TVOC were approximately 76.5%, 50.9%, 83.5%, 99.3%, 94.8%, and 97.1% after the fan filter unit (FFU) was equipped with a chemical filter. AMCs mainly include benzene, toluene, ethylbenzene, xylene (BTEX), alkanes and alkenes, though BTEX accounts for 77% of the total. VOC concentrations in cleanrooms fitted with FFU chemical filters and where the process equipment was not in operation were found to be lower than those at domestic residences and slightly higher than those found in commercial aircraft cabin air. The daily average TVOC concentrations were negatively correlated with temperature (R2 = 0.46, p < 0.01) and positively correlated with humidity (R2 = 0.26, p < 0.01). The daily average NH3 concentrations were negatively correlated with T (R2 = 0.19, p < 0.05) and positively correlated with RH (R2 = 0.18, p < 0.01). Dibutyl phthalate (DBP) and dioctyl phthalate/diethylhexyl phthalate (DOP/DEHP) were detected in the new sealing joint strips in the HEPA filters. Phthalates and organophosphates were not detected in the new filter papers.

Ultralow loading of Cu2O/CuO nanoparticles on metal-organic framework-derived carbon octahedra and activated semi-coke for highly efficient SO2 removal

A highly efficient desulfurizer is derived from a sacrificial Cu-based metal-organic framework (MOF) template, which is loaded on low-cost activated semi-cokes. The carbonized composite possesses highly-dispersed copper oxide nanoparticles (Cu2O/CuO) as active sites, which are distributed on MOF-derived carbon octahedra and activated semi-cokes. With an ultralow surface loading of 0.19 at% Cu and a high proportion of Cu+, the optimized sample shows an excellent breakthrough time of 822 min and SO2 adsorption capacity of 233.11 mg/g with a steady SO2 removal efficiency of 100%, which is superior to previously reported coke-base desulfurizers in literature. Meanwhile, the best-performed sample shows stability and reversibility for SO2 removal during 10 desulfurization−regeneration cycles. The excellent SO2 removal performance can be attributed to a well-developed porous structure and highly-dispersed copper oxide active sites due to the utilization of both sacrificial MOF template and activated semi-coke.

Experimental study on removal performance of SO2 and NOx in marine exhaust gas using seawater/urea peroxide solution and analysis of ions concentration change

The removal of SO2 and NOx emitted by marine diesel engines was still very important for the development of shipping industry. In this study, a novel method based on seawater/urea peroxide composited absorption solution was used to remove NOx and SO2 efficiently and can keep nitrate concentration lower in liquid phase. And the key parameters were investigated, such as removal efficiency, ions concentration, solution composition, reaction temperature and absorbent concentration. The selected reaction temperature and urea peroxide concentration was 60 °C and 5%, and the SO2 and NOx removal efficiency was close to 100% and 80% respectively. Compared with fresh water, the seawater can improve the NOx absorption capacity of urea peroxide solution, so as to meet the emissions regulation requirements. The concentration of NO3− increased with the oxygenation and absorption capacity of the absorbing solution increasing. However, the addition of seawater could make the concentration of NH4+ decrease a little bit. The ions concentration also increased with the reaction time, and when it came to practical application, the reaction time should be strictly controlled.

Enhancing the catalytic desulfurization capacity of CuO-LaCoO3 using two dielectric barrier discharge configurations

Developing efficient and economical methods to treat low concentrations of sulfur dioxide, which is commonly found in electrolytic aluminum flue gas and is typically emitted directly to the atmosphere without treatment, is an important objective. In this study, we examined the desulfurization efficiencies of CuO-LaCoO3 catalysts in two of the most common catalytic dielectric barrier discharge (DBD) enhancement layouts, namely the in-plasma-catalysis (IPC) and post-plasma-catalysis (PPC) configurations, for the first time. The results suggested a 160–266% enhancement in desulfurization efficiency can be reached in PPC configurations compared to the catalyst-only setup. More aggressively, 100% SO2 removal efficiency can be reached even at room temperature and pressure in IPC configuration if sufficient SIE (2486 J/L) was supplied. Among tested LaCoO3 catalysts, The groups doped with 15% Cu showed the best catalytic activity and excellent ozone suppression ability. The catalysts before and after the enhancement were analyzed and compared by N2-adsorption, SEM, XPS, XRD. The result suggested that discharge will increase the surface area of the catalyst from 31.81 to 155.43 (m2/g) and the proportion of Cu1+ without affecting the main crystalline structure ((Cu0.3Co0.7)Co2O4). Indicating the surface area and the REDOX capacity of catalyst are the main factors affecting the enhancement process. The change of intermediate and free radicals inside the reactor was also revealed by spectroscopy and numerical simulation.

Simultaneous removal of NOX and SO2 from flue gas in an integrated FGD-CABR system by sulfur cycling-mediated Fe(II)EDTA regeneration

Chemical absorption-biological reduction (CABR) process is an attractive method for NOX removal and Fe(II)EDTA regeneration is important to sustain high NOX removal. In this study a sustainable and eco-friendly sulfur cycling-mediated Fe(II)EDTA regeneration method was incorporated in the integrated biological flue gas desulfurization (FGD)-CABR system. Here, we investigated the NOX and SO2 removal efficiency of the system under three different flue gas flows (100 mL/min, 500 mL/min, and 1000 mL/min) and evaluated the feasibility of chemical Fe(III)EDTA reduction by sulfide in series of batch tests. Our results showed that complete SO2 removal was achieved at all the tested scenarios with sulfide, thiosulfate and S0 accumulation in the solution. Meanwhile, the total removal efficiency of NOX achieved ∼100% in the system, of which 3.2%–23.3% was removed in spray scrubber and 76.7%–96.5% in EGSB reactor along with no N2O emission. The optimal pH and S2−/Fe(III)EDTA for Fe(II)EDTA regeneration and S0 recovery was 8.0 and 1:2. The microbial community analysis results showed that the cooperation of heterotrophic denitrifier (Saprospiraceae_uncultured and Dechloromonas) and iron-reducing bacteria (Klebsiella and Petrimonas) in EGSB reactor and sulfide-oxidizing, nitrate-reducing bacteria (Azoarcus and Pseudarcobacter) in spray scrubber contributed to the efficient removal of NOX in flue gas.

Optimizing SO2 Adsorption from Flue Gas Using Microporous Polypropylene Hollow Fiber Membrane Contactor

This study optimized the operational parameters of removing SO2 from flue gas via a polymeric hollow fiber membrane contactor (HFMC) using the response surface methodology (RSM). The distilled water and polypropylene hollow fibers were applied as the adsorbent and membrane material, respectively. Three experimental parameters were chosen as independent variables: liquid flow rate, gas flow rate, and initial SO2 concentration. The SO2 removal efficiency was significantly affected by the initial SO2 concentration. The optimal ratio of liquid-to-gas flow rate was found to be 0.25 to reach maximum separation efficiency (98.81%). The optimal value of the liquid flow rate was 33 l/h, and the optimal gas flow rate was 131 l/h. The effect of CO2 presence, module length, fibers number, temperature, and the adsorbent nature were also investigated under optimal values obtained for the ratio of liquid-to-gas flow rate. Results indicated that CO2 presence in the flue gas slightly affects SO2 removal using water as an absorbent in HFCM. Furthermore, it was indicated that the SO2 removal efficiency was a function of the flue gas temperature and number of fibers: it decreased as the temperature rose from 20 to 50°C and the fiber numbers increased from 300 to 1000. This study offers a model to predict the efficiency of SO2 removal using HFMC under different conditions and provides the ground to further explore the industrial applications of this technology.

Removal of sulfur trioxide by wet injection with alkaline absorbent: Model and experimental studies

Sulfur trioxide (SO3) emissions from coal flue gas have become an increasingly serious issue, and alkaline absorbent injection technology has been successfully applied in industry as an effective control method. To accurately predict the SO3 removal effect, a new mathematical model based on the shrinking core model and mass conservation was proposed in this study. In this model, a fixed-bed adsorption experiment was used to estimate the absorption capacity of individual particles, and other model parameters were estimated. The theoretical results of the model were compared with the experimental results of an entrained flow reactor, the fitting parameters were determined, and the model was verified. In addition, the effects of key parameters such as the residence time, molar ratio, flue gas composition, and particle size of absorbers on the SO3 removal efficiency were compared and evaluated. Finally, the Sobol method was used to analyze the parameter sensitivity of the model. The results showed that particle size and porosity have an important influence on the removal of SO3, and thus should be considered when determining the type of absorbent.

Kinetic study of SO2 with sodium lactate based deep eutectic solvents and modelling of desulfurization intensification in rotating packed bed reactor

As ionic liquids alternative, the deep eutectic solvents (DESs) are expected to realize green and efficient SO2 recovery. In this work, the reaction kinetics of SO2 and sodium lactate (NaLa)/water DES was first studied. The reaction kinetic parameters, including order of reaction, rate constant, pre-exponential factor, and activation energy were determined. In view of the reaction characteristics, desulfurization intensification by high gravity technology was proposed. A mathematic model based on the reaction kinetics was developed to describe the SO2-DES mass transfer and reaction process in a rotating packed bed reactor. To validate this model, the desulfurization efficiency and mass transfer coefficient were measured under different operating conditions. It was demonstrated that SO2 removal efficiency was above 99% under optimized conditions, realizing efficient SO2 recovery. The validity of the proposed model was confirmed by the fact that most predicted mass transfer coefficients agreed well with the experimental results with deviations within ± 15%.

SOx removal and emission characteristics of WFGD system applied in ultra-low emission coal-fired power plants

In this paper, SOX (SO2 and SO3) removal and emission characteristics of wet limestone-gypsum flue gas desulfurization (WFGD) are investigated based on the data collected from 95 ultra-low emission coal-fired power units. The study shows that the overall removal efficiency of single-absorber is above 97.5%, in which the SO3 removal efficiency is between 31% and 70%. When the inner structures are installed into the spray absorber, the correlation between the inlet SO2 concentration and SOX removal efficiency becomes more obvious, however, with a tray absorber, the maximum SO2 removal efficiency of double-absorber reaches 99.74%, in which the SO3 removal efficiency is between 27% and 81%. With a normal spray absorber, the higher inlet concentration, the higher removal efficiency it reaches, while with a tray absorber, the result is opposite. With a single-absorber, there is little correlation between flue gas temperature drop and SO2 removal efficiency. Large temperature drop harms the improvement of overall SO2 removal efficiency but is beneficial to SO3 removal. By the calculation of SOX emission performance model, average emission performances of SO2 and SO3 are acquired, which are about 90–107 mg/(kW·h) and 81–97 mg/(kW·h), respectively.

Simultaneous removal of NO, SO2 and Hg0 with the WDRMRS

ABSTRACT Micro-nanobubbles can spontaneously generate hydroxyl free radicals (OH). Urea is a cheap reductant and can react with NOx species, and their products are nontoxic and harmless N2, CO2 and H2O. In this study, a Wet Direct Recycling Micro-nanobubble Flue Gas Multi-pollutants Removal System (WDRMRS) was developed for the simultaneous removal of NO, SO2 and Hg0. In this system, a micro-nanobubble generator (MNBG) was used to produce a micro-nanobubble gas–liquid dispersion system (MNBGLS) through recycling the urea solution from the reactor and the simulated flue gas composed of N2, NO, SO2 and Hg0. The MNBGLS, which has a large gas–liquid dispersion interface, was recycled continuously from the MNBG to the reactor, thus achieving cyclic absorption of various pollutants. All of the investigated parameters, including the initial pH and temperature of the absorbent as well as the concentrations of urea, NO and SO2 had significant effects on the NO removal efficiency but did not significantly affect the SO2 removal efficiency, whereas only the initial solution pH and NO concentration affected the Hg0 removal efficiency. The analysis results of the reaction mechanism showed that ·OH played a critical role in the removal of various pollutants. After the treatment by this system, the main removal products were Hg0 sediment, and NH4+ which could be easily recycled. The use of this system (MNBGLS) for the simultaneous removal of NO, SO2 and Hg0 is a new technology application and research. Recycling process based on MNBGLS succeeded in simultaneously removing NO, SO2 and Hg0. The system (MNBGLS) can provide a reference for commercial applications. The removal products are relatively simple and beneficial to recycling, which can reduce the cost of waste gas treatment.

Removal of SO2 from flue gas using blast furnace dust as an adsorbent.

To control the SO2 emission and achieve the target of "waste controlled by waste", a novel desulfurization method with blast furnace dust slurry was proposed. The effects of reaction temperature, oxygen concentration, and solid-liquid ratio on SO2 removal efficiency were investigated. The optimal conditions were reaction temperature of 35 ℃, oxygen concentration of 10 vol.%, and solid-liquid ratio of 0.5g/300mL. Under the optimal conditions, the desulfurization efficiency reached 100% for 4h. Response surface methodology (RSM) results showed that oxygen concentration significantly influenced the SO2 removal efficiency. Finally, the possible desulfurization mechanism of blast furnace dust was proposed based on the EDX, XRD, SEM-EDS, ICP, and IC. The blast furnace dust (main components are CaZn8(SO4)2(OH)12Cl2·(H2O)9, Mn6.927Si6O15·(OH)8, ZnO, Fe2O3) reacted with H+ to form Zn2+, Fe3+, and Mn2+ which shows a key effect on the SO2 liquid catalytic oxidation. This study provides a promising, feasible, and low-cost desulfurization technology by reusing blast furnace dust.

Process analysis of SO3 removal by Ca(OH)2 particles from flue gas

SO3 in coal-fired flue gas will cause equipment corrosion and the emission of sulfuric acid mist. The performance of injecting the alkaline adsorbent into the flue gas to remove SO3 is affected by the adsorption of SO2 in the flue gas. Taking Ca(OH)2 as a typical alkaline adsorbent, a model describing the adsorption of SO3 and SO2 by Ca(OH)2 particles was established, based on the combination of the product-island-growth model and the grain model. The parameters in the model were determined by the experimental data of adsorption in the fixed-bed reactor. The adsorption process of a single Ca(OH)2 particle was studied by numerical simulation. The adsorption of SO3 and SO2 was found to involve two stages: (1) In the early stage when there existed unreacted grain surface in the particle, SO3 and SO2 mainly reacted with the left fresh grain surface. The SO3 adsorption was controlled by internal pore diffusion and surface reaction, in which internal pore diffusion played a major role. The SO3 adsorption showed a shrinking core mode. The SO2 adsorption was controlled by internal pore diffusion and surface reaction and occurred throughout the entire particle. The SO3 adsorption selectivity at the outer surface of the particle was the highest, and decreased with a decreasing dimensionless particle radius R/R0. (2) In the later stage when the grain surface was completely reacted, the SO3 adsorption was controlled by internal pore diffusion and product-layer diffusion, in which product-layer diffusion played a major role. The SO2 adsorption was controlled by product-layer diffusion. The product-layer diffusion coefficient in the SO3 adsorption process was significantly higher than that of the SO2 adsorption, so SO3 was still significantly adsorbed in the later stage. The adsorption process of Ca(OH)2 under different particle structure parameters showed that decreasing the particle radius and increasing the particle porosity and specific surface area increased the SO3 removal efficiency as well as the total conversion of Ca(OH)2. Decreasing the particle radius and the specific surface area and increasing the particle porosity increased the SO3 adsorption selectivity by Ca(OH)2. When preparing industrial adsorbents, the optimization of the particle porous structure should be given attention.

Novel method for high-performance simultaneous removal of NOx and SO2 by coupling yellow phosphorus emulsion with red mud

This study develops a novel method for simultaneously removing NOx and SO2 from coal-fired flue gas via coupling yellow phosphorus emulsion with red mud. The effects of different factors on the synergistic purification of sulphur-nitric acid were investigated in this study. The achieved removal efficiencies of NOx and SO2 were as high as 97.9% and 100%, respectively, under optimized conditions. This indicates that the yellow phosphorus emulsion coupled with red mud as a composite absorbent is favorable for simultaneous removal effect on NOx and SO2. The samples before and after the reaction were characterized using X-ray diffraction, X-ray fluorescence, inductively coupled plasma, scanning electron microscopy, and other methods, and the main product was identified as gypsum (CaSO4·2H2O) after desulfurization and denitrification. Adsorption kinetics, isotherm adsorption, and breakthrough curve models of NOx and SO2 adsorption on red mud were established. Moreover,the mechanism of multiphase oxidation and absorption reactions for simultaneous desulfurization and denitrification was also speculated.

Experimental study on the influence of H 2 O vapor and O 2 for desulfurization and denitrification of the diesel exhaust in marine application by non‐thermal plasma

To improve the pollutant removal efficiency by non-thermal plasma (NTP), the effect of H2O vapor and O2 on removal efficiency of NO and SO2 as well as the reduction of CO was investigated in H2O/O2/SO2/NO/C3H6/CO2/N2 system. To analyse the reaction mechanism, the effects of H2O vapor and O2 on the emission intensity of O ( 3 p 5 P → 3 s 5 S 2 0 ) and O H ( A 2 ∑ + → X 2 ∏ ) were investigated. The experimental results show that the increase of H2O vapour (0%–9.8%) promotes the generation of OH radicals, increases the removal efficiency of NO from 18.9% to 57.3%, decreases the energy per NO removed from 449.0 to 148.1 eV/NO, increases SO2 removal efficiency from 4.8% to 35.3%, decreases the energy per SO2 removed decreases from 2784.0 to 582.9 eV/SO2, and reduces the generation of CO from 460 to 229 ppm. In the range of 0%–15%, the increase of O2 content promotes the formation of O radicals, increases the removal efficiency of NO from 8.5% to 54.2%, and decreases the energy per NO removed from 994.3 to 156.4 eV/NO. In the range of 0%–5%, increasing O2 content promotes SO2 removal efficiency from 8.7% to 24.8%, and decreases the energy per SO2 removed from 2485.7 to 876.6 eV/SO2. However, CO generation increases from 200 to 350 ppm with the increase of O2 in 0%–5% due to the incomplete oxidation of C3H6. In the range of 5%–15%, the increase of O2 produces more O radicals, decreases the removal efficiency of SO2 from 24.8% to 23.5% and the generates of CO from 350 to 311 ppm. This study is helpful for improving the efficiency of NTP for desulfurization and denitrification, while reducing the by-product CO.

Enhanced SO2 Absorption Capacity of Sodium Citrate Using Sodium Humate

A novel method of improving the SO2 absorption performance of sodium citrate (Ci-Na) using sodium humate (HA–Na) as an additive was put forward. The influence of different Ci-Na concentration, inlet SO2 concentration and gas flow rate on desulfurization performance were studied. The synergistic mechanism of SO2 absorption by HA–Na and Ci-Na was also analyzed. The consequence shows that the efficiency of SO2 absorption by Ci-Na is above 90% and the desulfurization time added with the Ci-Na concentration rising from 0.01 to 0.1 mol/L. Both the desulfurization efficiency and time may increase with the adding of HA–Na quality in Ci-Na solution. Due to adding HA–Na, the desulfurization efficiency of Ci-Na increased from 90% to 99% and the desulfurization time increased from 40 to 55 min. Under the optimum conditions, the desulfurization time of Ci-Na can exceed 70 min because of adding HA–Na, which is nearly doubled. The growth of inlet SO2 concentration has little effect on the desulfurization efficiency. The SO2 adsorption efficiency decreases with the increase of inlet flow gas. The presence of O2 improves the SO2 removal efficiency and prolongs the desulfurization time. Therefore, HA–Na plays a key role during SO2 absorption and can dramatically enhance the SO2 adsorption performance of Ci-Na solution.

SO2 removal performance for the solution absorption system applied to coal-fired flue gas

The solution absorption system has great potential for recovery of water and latent heat from industrial gas. However, few investigations have been conducted on the synergistic removal of SO2 and the treatment of the associated precipitation when the method is applied for flue gas from coal-fired power plants. To solve this problem, a falling-film reaction platform was established and the CaCl2 solution was chosen as the liquid desiccant. The effects of solution temperature and concentration, solution pH, O2 content and catalyst concentration on the efficiency of SO2 removal were investigated. The solubility of the CaSO4·2H2O precipitates in the CaCl2 solution was measured. The results revealed that the precipitated component was influenced by the O2 content. The decrease in solution pH was responsible for the decrease in the efficiency of SO2 removal. The highest SO2 removal efficiency of 95.6% was obtained during the operation of solution circulation in this experiment. In addition, the solubility test showed that a higher temperature, a lower concentration and the addition of Ca(OH)2 were conducive to reducing the solubility of the CaSO4·2H2O precipitate in CaCl2 solution.

Dry scrubbing of gaseous HCl and SO2 with hydrated lime in entrained mixing reactor

The simultaneous dry scrubbing of gaseous HCl and SO2 by hydrated lime in the entrained mixing reactor has been studied at condition of simulating waste incineration flue gas. The entrained mixing reactor combining a numerical optimized entrained mixing up flow reactor with a rectifier for homogeneous flue gas mixing flow distribution were developed as reaction chambers for the dry scrubbing of gaseous HCl and SO2 with hydrated lime powders. The dry scrubbing performance of this technology was experimented at the pilot scale entrained mixing reactor with 0.3 m in diameter of lower part chamber, 1.29 m in diameter of upper part chamber and 6.0 m in total height. Three kind of hydrated lime powders with different surface area and pore volume were injected with carrier compressed air into the reaction chamber for absorption of acid gaseous. The experimental conditions were the following: reaction temperature 180 °C, gas flow rate 1800Nm3/h and HCl and SO2 concentration in inlet gas 250 ppm, respectively, giving different values for the ratio the amount of fresh hydrated lime and acid gaseous concentration at the inlet of reaction chamber and that corresponding to the stoichiometric molar ratio (SR). The gaseous HCl and SO2 removal efficiencies ranged from 89 to 99% and 87 to 99% respectively. The best performance of dry scrubbing was obtained for high surface area and pore volume of the hydrated lime. Increased the surface area and pore volume of hydrated lime improved the removal performance of the gaseous HCl and SO2 as well as the solid reactant conversion. The concentration of HCl and SO2 at the downstream of bag filter was measured to predict the absorption of gaseous HCl and SO2 on the surface of bag filter.

Mass transfer process intensification for SO2 absorption in a commercial-scale wet flue gas desulfurization scrubber

To intensify SO2 absorption process in wet flue gas desulfurization (WFGD) spray scrubber, a comprehensive CFD model coupled transfer process with chemical reactions is established by Eulerian‒Lagrangian method and verified in a commercial-scale device of 330 MW coal-fired power unit. The desulfurization performance is significantly affected by both the property of each droplet and the dispersion of droplet swarm, which are determined by the spray behaviors. Three dominant factors, including droplet diameter, injection direction and spray morphology, are explored to optimize the spray conditions for intensifying SO2 absorption process. Differing from the ideal plug flow, the optimal diameter of droplet in non-ideal flow is obtained by considering the synergistic effect of the uniformity of gas–slurry distribution and the dynamics of SO2 mass transfer. Compared with the single-direction spray with downward or upward injection, the dual-direction spray reaches a great balance between the competitive effects of the uniformity of gas‒slurry flow and the interfacial area for mass transfer. The influence of spray morphology on mass transfer process is essentially the difference of dispersion characteristics of droplets in the middle part of scrubber. A design scheme combining full-cone and hollow-cone nozzles is suggested for improving the overall SO2 removal efficiency.