Flue Gas Desulfurization Research Articles

Synergistic reduction of SO2 emissions while co-firing biomass with coal in pilot-scale (1.5 MWth) and full-scale (471 MWe) combustors

The objective of this study was to understand the synergistic effect of sulfur dioxide (SO2) emission reduction during the combustion of biomass-coal blends in comparison to pure coal by recording the gaseous SO2 concentrations, analyzing the composition of combustion ash by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), and simulating and verifying the fate of sulfur by a thermodynamic equilibrium software (FactSage). In Set A experiments, five combinations of coal and steam-exploded biomass (100/0, 75/25, 50/50, 25/75, 0/100 in percentages by mass) were co-fired in a 1.5 MWth pilot-scale combustor. In Set B, pure coal (100/0) and an 85/15 percent mass blend of coal and torrefied biomass were co-fired in a 471 MWe utility boiler. Woody biomass contains lower amounts of sulfur compared to coal and the linear lowering of SO2 emissions as a result of co-firing is called the dilution effect. For Set A tests, FactSage predicted, and ash analysis confirmed that calcium was primarily responsible for the synergistic emission reduction (beyond dilution effect) in all the blends, except in pure biomass, where potassium was responsible. During pure coal combustion, 41.1% of the sulfur in the system was absorbed in the ash, compared to 97.0% during pure biomass testing. In Set B tests, the 85/15 coal-biomass blend, showed a 28.1% reduction in SO2 emissions along with a 22.1% reduction in the lime slurry utilization at flue gas desulfurization (FGD) towers compared to pure coal, which is equivalent to saving 7.4 L of lime slurry per MWe-hour. The results suggest that blending woody biomass with coal can help coal-fired utility boilers meet environmental emission standards and reduce desulfurization costs. These results are important since the current literature is deficient in research conducted at suspension-fired full-scale boilers to reduce SO2 emissions by co-firing coal and biomass blends.

Removal and emission characteristics of hazardous trace elements in total and graded particulate matters: A case study of a typical ultra-low emission coal-fired power plant

Particulate matters (PMs) and hazardous trace elements (HTEs) emitted from coal-fired power plants (CFPPs) have raised serious environmental and human issues. Herein, total PMs and graded PMs including PM<1, PM1–2.5 and PM2.5–10 at the inlet/outlet of air pollution control devices (APCDs) were collected from a representative ultra-low emission (ULE) CFPP in China. The removal efficiencies of total PMs by selective catalytic reduction (SCR), electrostatic precipitator (ESP), wet flue gas desulfurization (WFGD) and wet electrostatic precipitator (WESP) were 0.40 %, 99.9 %, 38.1 % and 85.3 %, respectively. PM2.5–10 was robustly removed by WFGD, while PM<1 and PM1–2.5 were readily removed by WESP. The removal efficiencies of As, Cd, Cr and Pb in total PMs by APCDs followed an order: ESP > WESP > WFGD > SCR. SCR significantly decreased Se concentration by 42.8 %, contrasting to the removal of As, Cd, Cr and Pb (10.8–20.8 %). As, Cd, Cr, Pb and Se concentrations in graded PMs at the outlets of ESP, WFGD and WESP decreased with particle size increasing. All As, Cd, Cr, and Pb contents in PM<1, PM1–2.5 and PM2.5–10 at WFGD outlet increased, surpassing their analogues at ESP and WESP outlets. However, the concentration of Se declined in PM<1 at WFGD outlet. The atmospheric emission factors (EFs) of As, Cd, Cr, Pb and Se in the studied ULE CFPP were respectively 7.32, 1.27, 6.05, 122.5 and 6.42 mg/t, in line with Monte Carlo simulations. This study would not only provide a basis for emission control of PMs and HTEs in CFPPs, but also promote the improvement of respective environmental policy.

Aminoalkyl organosilicon with dual chemical sites for SO2 absorption and analysis of site-specific absorption entropy and enthalpy

Wet flue gas desulfurization is widely used for its high efficiency, however, the low absorption capacity, high viscosity and poor thermal stability of absorbents remains an open question. Herein, a low viscosity and high thermal stability SO2 absorbent with dual interacting sites was synthesized by introducing phenyl into organic silicon. The thermal stability of 1,5-bis (diethylamino)− 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane (BADPS) is comparable to ILs, while its viscosity is much lower than that of ILs. For the first time, we use a variant of the pseudo-first-order reaction rate equation obtained the reaction rate constant and the saturation absorption capacity. In addition, the optimal absorption and desorption temperatures were obtained based on an objective function. Mostly importantly, the absorption enthalpy change (ΔH) and entropy change (ΔS) of BADPS absorption reaction show the highest absolute values of SO2 absorbents reported so far. These results indicated that the prepared amine alkyl organosilicon could serve as a promising desulfurizing agent with low-energy consumption.

Equilibrium and experimental study on carbothermal reduction of sulfur dioxide to elemental sulfur

In order to solve the problem of low utilization value of flue gas desulfurization by-product, reduction of sulfur dioxide to elemental sulfur has emerged as a new process for resource utilization of SO2 with promising application prospects. Herein, the thermodynamic equilibrium calculation was carried out to study the influence of temperatures and C/SO2 molar ratios on the C-SO2 reaction. The effects of reaction temperature, carbon mass, and CO concentration on SO2 reduction by coke and activated carbon were studied on a fixed bed reaction system. The theoretical results demonstrated that the highest equilibrium S yield occurred when the C/SO2 molar ratio is 1, with higher ratios resulting in the formation of COS, CS2, and CO. Experimental data revealed that at temperatures below 700 °C, both SO2 conversion and S yield are notably low. As the temperature increases, both the conversion and yield gradually increase and approach the thermodynamic equilibrium value. The evolution of carbon surface chemical properties under the action of CO was analyzed by FTIR and XPS, which indicated that the presence of CO promotes the decarboxylation reaction, and then increases SO2 conversion and S yield. The conclusion of this study provides guidance for the development of high efficiency SO2 reduction technology.

Resource Utilization Potential of Red Mud: A Study on the Micro-Mechanism of the Synergistic Effect of Multiple Solid Waste Filling Materials

Red mud (RM) is a common industrial byproduct that is characterized by high alkalinity, high pollution, and difficult utilization. In this paper, gangue (CG), flue gas desulfurization gypsum (FGD), and silicate cement (PC) were used to assist red mud in the preparation of red mud-based composite filler material (RMC), aiming at the large-scale resource utilization of RM. The effects of the mass ratio of RM/CG, the mass ratio of FGD/(RM + CG), and the water–solid ratio (WCR) on the multi-angle properties of RMC were investigated and the optimal ratios were determined. The results showed that the RM/CG was 7:1, FGD/(RM + CG) was 4%, and WCR was 0.51 (RMC8), and the system could increase the RM content to 70%. The microstructural analysis of RMC using a specific surface area and porosity analyzer (BET), X-ray diffractometer (XRD), and scanning electron microscope (SEM) showed that its hydration products could remodel the pore structure, encapsulate and cement the coarse and fine particles into a dense matrix, and play a certain alkali reduction role, which revealed the microscopic synergistic mechanism between multiple solid wastes. The study shows that the comprehensive disposal of RM reduces the pollution released into the environment and provides new ideas for the green development of mines.

Analisa Partikulat Debu, SO Dan NO2 Pada Industri Manufaktur Di Surabaya

This study aims to determine how much dust, SO2 and NO2 concentrations are in the air and to know the description of the distribution of air in the study site. In addition, this research also aims to design air pollution control devices that can be used to control the emissions produced. The method in this research uses the Gausse method in modeling and uses AERMOD software and Google Earth to complete the model description. It is known that the farthest distance the highest concentration of dust spread is 0.071 km with a dust concentration of 101.3 µg/m3. The farthest distance the highest concentration of SO2 spread was at a distance of 0.051 km with a value of SO2 concentration of 6753.3 µg/m3. The farthest distance the highest concentration of NO2 spread was at a distance of 0.051 km with a value of NO2 concentration of 91.45 µg/m3. The air controller uses a bag filter with 6 compartments for dust control and uses silica absorbent and activated charcoal for controlling NO2 and the Flue-Gas Desulfurization (FGD) method for SO2.

Optimization of effecting parameters for flue gas desulfurization in a self‐priming venturi scrubber using response surface methodology

AbstractHydrogen sulfide (H2S), a highly poisonous and corrosive gas, is regarded as a hazardous air pollutant with significant effects on human health. Hence, reduction of hydrogen sulfide (H2S) gas from the atmosphere is very essential. In the present work, self‐priming venturi scrubber is employed to extract H2S gas from the air. Response surface methodology (RSM) with a central composite design (CCD) has been selected to investigate maximizing the H2S removal efficiency by optimizing the process variables. Experiments were carried out by altering the throat gas velocity, outer cylinder liquid level and inlet concentration of H2S. The analysis of variance (ANOVA) test showed that the parameters had a significant effect on the efficiency of H2S removal. A quadratic equation has been developed that accurately predicts the percentage of removal efficiency. The appropriateness of the generated model has been verified by the value of higher R2 resulting from the regression analysis. According to the observations, the velocity of throat gas has the highest effect on the H2S removal efficiency, whereas inlet H2S concentration has the least effect.

A novel method of combined desulfurization and heat utilization of low-temperature flue gas from hot blast stove for blast furnace: Laboratory research and industrial application

To address the challenges of low waste heat utilization rates and high desulfurization costs, this study proposes a novel method for combined desulfurization and heat utilization of low-temperature flue gas. By utilizing the low-temperature flue gas from hot blast stoves to dry lump metallurgical coke, the method also achieves flue gas desulfurization during the lump coke drying process. During the drying process, the wet lump coke desulfurizes due to the reaction between water vapor in the lump coke and the SO2 and oxygen in the flue gas, resulting in the formation of sulfuric acid. Additionally, the coke powder generated by friction during the drying process of lump coke has a large specific surface area, enabling it to adsorb additional quantities of SO2 and enhance the desulfurization process. It's important to note that the lump coke itself does not exhibit adsorption properties towards SO2 during the drying process, and the gas is not retained within the lump coke. Industrial applications indicate the outlet flue gas temperature is reduced from 175 °C to 60 °C, and the concentration of SO2 in the outlet flue gas is reduced from 150 mg/m3 to 29 mg/m3.

Positive and negative impacts of flue gas desulfurization (FGD) gypsum on water quality

Flue gas desulfurization (FGD) gypsum, a by-product of carbon-based energy sources, has typically been incorporated as a component of concrete mixes and wallboard and beneficially used as an agricultural amendment to enhance terrestrial crop production and improve the quality of runoff. These various uses for the by-product aid in reducing the amount that is ultimately landfilled. Limited studies have investigated its benefits when used directly in aquatic settings, such as ponds and lakes, to increase hardness and potentially mitigate eutrophication. A 36-day field mesocosm experiment tested a larger range of FGD gypsum concentrations (500–2000 mg/L) than those previously tested in the literature to investigate its desired and potentially undesired impacts on water quality, including the algal community. High FGD gypsum concentrations, 1000 and 2000 mg/L, were found to have more undesired impacts than the 500 mg/L treatment, including an initial spike in cyanobacteria, a decrease in total zooplankton abundance, and an increase in certain trace metals in the highest treatment. Ultimately, the 500 mg/L FGD gypsum treatment was found to have fewer undesired impacts while still resulting in significant desired effects, including those on hardness and pH, as well as moderate reductions in algal abundance. This experiment provides a better understanding of the effects of FGD gypsum when directly used in an aquatic setting, determines an optimal dose for future field experiments, and helps provide the groundwork for developing an upper threshold on FGD gypsum so as to not have the negative effects outweigh the positive.

High-performance electrospun polystyrene-based nanofiber membrane for efficient SO2 capture

It is essential to design a stable membrane material to solve the pollution produced by SO2 emissions. This study aims to fabricate polystyrene (PS) nanofiber membranes, which are applied for flue gas desulfurization. PS nanofiber membranes are fabricated via electrospinning with porous polypropylene (PP) membrane as the support and high hydrophobic PS as the main membrane material. The modified membranes are characterized by scanning electron microscopy, true color confocal microscopy and other analyticalmethods, and the effects of mixed solvent ratio and polymer concentration on the desulfurization performance and on the stability of PS nanofiber membranes are investigated. The results suggest that an optimum hydrophobicity of PS nanofiber membrane is obtained with a water contact angle of 145°, when the polymer concentration is 5 %. The average pore size of PS nanofiber membrane is 1.56 μm, and the liquid entry pressure of water (LEPw) is 0.26 bar and the roughness of membrane is 5.674 μm. The desulfurization performance of the PS nanofiber membrane is better than that of the PP membrane. The SO2 absorption flux of the modified membranes keeps at 7.2 × 10−4 to 7.6 × 10−4 mol·m−2·s−1 during 5 h operating, and SO2 removal efficiency is up to 50 %, which potentially makes contributions to air pollution reduction.

Mechanism and experimental study of desulfurizing agent based on Mn/Ce-Ca for sintering flue gas desulfurization (FGD)

A novel Mn/Ce-Ca-based desulfurizer was prepared by dipping-roasting method to improve the performance of single calcium hydroxide (Ca(OH)2) for sintering flue gas desulfurization (FGD) at 100–350 ℃. In this study, metal dopants iron oxide (Fe2O3) and magnesium oxide (MgO) are added to improve the microstructure of single Ca(OH)2 and enhance the utilization of active components. The experimental results on the fixed bed showed that the desulfurization performance got best when the ratio of Fe2O3 to MgO was 3:2, the dipping times of desulfurizer were two, the temperature was 350 ℃, and the oxygen content was 5%. Meanwhile, the effect of H2O content was also studied. Great desulfurization ability with a removal efficiency of 100%, sulfur capacity of 69.95 mg/g, and breakthrough time of 76 min was achieved by desulfurizer 3F2M–3MC-Ca. Even at a low temperature of 100 °C, the sulfur capacity of the desulfurizer is three times higher than that of single Ca(OH)2, confirming its advantages in low-temperature desulfurization. Moreover, the reaction mechanism is systematically elaborated via the kinetic, diffusion, and thermodynamic calculations, and the characterization of this desulfurizer is studied by XRD, SEM, BET, XPS, and ICP-OES. Results show that the addition of Mn/Ce significantly enhances the activity of the desulfurizer by providing abundant oxygen vacancies during the reduction reaction. The work presented here has profound implications for future studies of the low-temperature dry sintering flue gas desulfurization field. Finally, the potential application of this technology is discussed to demonstrate the industrial application value.

Development of an online analyser to meet challenging new discharge limits for mercury in flue gas desulphurisation wastewater

Abstract Anthropogenic emissions of mercury to the environment are of great concern due to its toxicity. The burning of coal contributes highly to Hg emissions and, as such, much lower effluent discharge limits for Hg in flue gas desulphurisation (FGD) wastewater have recently been proposed in the USA. Lower detection limits are required to meet the most demanding discharge limit of 10 ng L−1. Therefore, in this work, a new analyser for online monitoring of Hg in FGD wastewater based on syringe injections of chemicals combined with gold amalgamation – atomic fluorescence spectrometry has been developed. The instrument has been validated against international standard method ISO 17852, as well as an interference study with extreme levels of salts majorly present in FGD water. Detection limits of 1.8 ng L−1 as well as accurate performance in an on-site field trial indicate that the methodology is fit to meet the new legislation.

Study on Multi-Pollutant Test and Performance Index Determination of Wet Electrostatic Precipitator

A wet electrostatic precipitator (WESP) is typically installed downstream of wet flue gas desulfurization (WFGD) to remove fine particles and sulfuric acid mists from flue gases in coal-fired power plants. The emission reduction characteristics of multiple pollutants and the energy consumption data of 214 sets of WESPs (94 sets of metal plate WESPs, 111 sets of conductive Fiber Reinforced Plastic WESPs, and 9 sets of flexible plate WESPs) were tested and analyzed, and the results showed that: WESPs had a high removal efficiency on PM, PM2.5, SO3, droplets and Hg, and mostly concentrated in ≥75%, ≥70%, ≥60%, ≥70% and ≥40%, respectively. The outlet pollutant concentrations were mostly concentrated in ≤5 mg/m3, ≤3 mg/m3, ≤5 mg/m3, ≤15 mg/m3 and ≤5 μg/m3, respectively. Specific power consumption and specific water consumption were concentrated in the range of 0.5~2.5 × 10−4 kWh/m3 and ≤10 × 10−6 t/m3. The correlation analysis of multiple pollutant’s removal performance was studied and the quantitative evaluation index requirements of high efficiency WESPs were determined in this paper. The high efficiency indexes of WESPs, such as PM emission concentration, SO3 emission concentration, PM removal efficiency, SO3 removal efficiency, pressure drop, air leakage rate and specific power consumption, were ≤2.50 mg/m3, ≤2.50 mg/m3, ≥90%, ≥85%, ≤200 Pa, ≤0.5% and ≤1.3 × 10−4 kWh/m3, respectively. The high efficiency indexes of specific water consumption for metal plate WESPs and FRP WESPs were ≤2.50 and ≤0.66 × 10−6 t/m3, respectively. This study can provide valuable reference for the following energy conservation and efficiency improvement of ultra-low emission units.

Studies on the industrial applications of limestone samples from three geographical regions in Nigeria: Ashaka, Mfamosing, and Nkalagu

The chemical properties of limestone have been the subject of several studies in recent years, highlighting its importance in various industrial applications. The present study focuses on six limestone samples from three geographical regions in Nigeria (Ashaka, Mfamosing, and Nkalagu). The analyses of their chemical composition using the Loss on Ignition Test and X-Ray Fluorescence Spectrometry was successfully carried out. Results of the study show that CaO is the main component, comprising between 60.054 % and 78.632 % of the samples. Values of Loss of Ignition (LOI) ranged from 30.820 % to 33.280 % while SiO2 composition ranged between 5.095 % to 12.238 %. Other oxides detected, include Al2O3 and Fe2O3, which make up less than 1 % of the composition. Obtained values were compared to Limestone standards for various industries and findings indicate that the Ashaka, Mfamosing, and Nkalagu limestone samples are of high purity and suitable for use in various industrial fields, including the steel industry, manufacture of bleaching powder, manufacture of calcium carbide, sugar industry, textile manufacture, cement industry, agricultural practice (soil liming), and flue gas desulphurization. Thus limestone deposits from Ashaka, Mfamosing, and Nkalagu has more potential and application uses beyond cement production which they are currently used for

Fabrication of Pillar-Cage Fluorinated Anion Pillared Metal-Organic Frameworks via a Pillar Embedding Strategy and Efficient Separation of SO2 through Multi-Site Trapping.

Flue gas desulfurization is crucial for both human health and ecological environments. However, developing efficient SO2 adsorbents that can break the trade-off between adsorption capacity and selectivity is still challenging. In this work, a new type of fluorinated anion-pillared metal-organic frameworks (APMOFs) with a pillar-cage structure is fabricated through pillar-embedding into a highly porous and robust framework. This type of APMOFs comprises smaller tetrahedral cages and larger icosahedral cages interconnected by embedded [NbOF5]2- and [TaOF5]2- anions acting as pillars. The APMOFs exhibits high porosity and density of fluorinated anions, ensuring exceptional SO2 adsorption capacity and ultrahigh selectivity for SO2/CO2 and SO2/N2 gas mixtures. Furthermore, these two structures demonstrate excellent stability towards water, acid/alkali, and SO2 adsorption. Cycle dynamic breakthrough experiments confirm the excellent separation performance of SO2/CO2 gas mixtures and their cyclic stability. SO2-loaded single-crystal X-ray diffraction, Grand canonical Monte Carlo (GCMC) simulations combined with density functional theory (DFT) calculations reveal the preferred adsorption domains for SO2 molecules. The multiple-site host-guest and guest-guest interactions facilitate selective recognition and dense packing of SO2 in this hybrid porous material. This work will be instructive for designing porous materials for flue gas desulfurization and other gas-purification processes.

Fabrication of Pillar‐Cage Fluorinated Anion Pillared Metal–Organic Frameworks via a Pillar Embedding Strategy and Efficient Separation of SO2 through Multi‐Site Trapping

AbstractFlue gas desulfurization is crucial for both human health and ecological environments. However, developing efficient SO2 adsorbents that can break the trade‐off between adsorption capacity and selectivity is still challenging. In this work, a new type of fluorinated anion‐pillared metal–organic frameworks (APMOFs) with a pillar‐cage structure is fabricated through pillar‐embedding into a highly porous and robust framework. This type of APMOFs comprises smaller tetrahedral cages and larger icosahedral cages interconnected by embedded [NbOF5]2− and [TaOF5]2− anions acting as pillars. The APMOFs exhibits high porosity and density of fluorinated anions, ensuring exceptional SO2 adsorption capacity and ultrahigh selectivity for SO2/CO2 and SO2/N2 gas mixtures. Furthermore, these two structures demonstrate excellent stability towards water, acid/alkali, and SO2 adsorption. Cycle dynamic breakthrough experiments confirm the excellent separation performance of SO2/CO2 gas mixtures and their cyclic stability. SO2‐loaded single‐crystal X‐ray diffraction, Grand canonical Monte Carlo (GCMC) simulations combined with density functional theory (DFT) calculations reveal the preferred adsorption domains for SO2 molecules. The multiple‐site host–guest and guest‐guest interactions facilitate selective recognition and dense packing of SO2 in this hybrid porous material. This work will be instructive for designing porous materials for flue gas desulfurization and other gas‐purification processes.

Mechanical enhancement of epoxidized natural rubber by flue gas desulfurization ash as the sole reinforcing filler

AbstractFlue gas desulfurization facilities produce flue gas desulfurization ash (FGDA), which has ecological and economic benefits. In this article, we explored the possibility and impact of using FGDA as the sole reinforcing filler to mechanically improve epoxidized natural rubber (ENR). The influence on the properties of the composites was examined. FGDA exhibits good interfacial interaction and compatibility with ENR, which improves the mechanical properties of ENR. When 15 phr FGDA was added, the tensile strength of the composites increased by approximately 41.4% compared with that of pure ENR. This work demonstrates the possibility of using FGDA as an effective and sole reinforcing material to enhance the properties of rubber materials.Highlights FGDA improves the mechanical properties of ENR as a sole reinforcing filler. FGDA reacts with ENR during vulcanization, enhancing compatibility. Adding 15 phr FGDA to ENR increases the tensile strength by 41.4%.

The influence of air pollution control devices on gas organic pollutants emission from coal-fired power plants based on LCA

Air pollutants (e.g., NOx, SO2) emitted from coal-fired power plants in China have been effectively controlled by Air Pollution Control Devices (APCDs) since 1996. However, the gas organic pollutants (typically Volatile Organic Compounds (VOCs) and Polycyclic Aromatic Hydrocarbons (PAHs)) have been overlooked for a long time. In this study, based on the life cycle assessment method, the effect of APCDs (mainly Selective Catalytic Removal (SCR), Electrostatic Precipitator (ESP), Wet Flue Gas Desulfurization (WFGD), and Wet Electrostatic Precipitator (WESP)) on gas organic pollutants (without methane) from three typical coal-fired power plants in China has been evaluated in terms of direct emission removal and indirect emissions. Detecting the gas organic pollutants concentrations at the inlet and outlet of APCDs in these three cases, it is found that the total direct emission removal efficiency is up to more than 71.97%, with SCR’s contribution being the highest. However, the manufacture and equipping of APCDs will lead to indirect emission of gas organic pollutants. The result shows that the SCR system is also the main process that induces indirect emissions of gas organic pollutants, associated with the utilization of liquid ammonia and catalyst. Compared to the direct emission of gas organic pollutants, indirect gas organic pollutants emissions can not be ignored. The calculation of net emission removal and the degree of co-effects shows that APCDs can reduce gas organic pollutants, which results in reducing the photochemical ozone creation potential of 1.81E-06~5.93E-06kg(Ethene eq.)/MW·h and human toxicity potential of 2.51E-03~8.06E-03kg (DCB eq.)/MW·h.

Interactions between flue gas desulfurization gypsum and biochar on water infiltration characteristics and physicochemical properties of saline-alkaline soil

The application of flue gas desulfurization gypsum (FGDG) improves the soil structure, reduces soil pH, and accelerates soil salt leaching. Biochar amendment to soil can affect the soil infiltration rate, increase soil porosity, decrease soil bulk density, and enhance the water retention capacity. This study investigated the interactive effect of FGDG and biochar on water infiltration characteristics and physicochemical properties as well as determined the optimal amendment rate as a saline-alkaline soil conditioner. Seven experimental schemes were designed, and the newly reclaimed cultivated soil from Pingtan Comprehensive Experimental Zone in Fujian Province, China, was used in an indoor soil column experiment to simulate soil infiltration. Five models were employed to describe the infiltration process. The power function was used to represent the dynamic process of the wetting front. The conclusions of this study are as follows: (1) there was a reduction in the infiltration capacity of saline-alkaline soil (sandy soil) in each treatment, and the application of FGDG alone had the highest inhibition effect compared to the control (CK). The Kostiakov model provides the best fit for the experimental data of soil cumulative infiltration. (2) All treatments increased the total porosity and water content of saline-alkali soil, with the combined application of FGDG and biochar found to be more effective. (3) The application of FGDG alone or in combination with biochar decreased the pH and increased the electrical conductivity of the saline-alkali soil significantly, with the combined application having the most significant effect. In contrast, soil amended with biochar alone had minimal effect on the pH and EC of the soil. (4) The best improvement ratio was achieved with the F1B2 combination (75 g/kg FGDG + 30 g/kg biochar).

Recycling flue gas desulfurization ash in enhancing the comprehensive moisture susceptibility of asphalt mixtures

Moisture susceptibility of asphalt mixtures is a major concern in areas with heavy rainfall or humid climates, as it can lead to premature pavement failures. As a typical industrial by-product during the flue gas desulfurization process of coal-fired, flue gas desulfurization ash (FGDA) with alkali mineral can facilitate the water damage resistance of asphalt mixtures. However, low density and high hydrophilic coefficient of FGDA limit its improvement effect. Hence, the comprehensive moisture susceptibility of asphalt mixtures with FGDA deserves systematic investigation. In this study, the properties indexes of FGDA and FGDA-limestone filler (LF) composite fillers were characterized. And the moisture susceptibility of asphalt mixtures containing six dosages of FGDA-LF fillers under hydrostatic damage and moisture induced sensitivity tester (MIST) hydrodynamic damage conditions were determined. The comprehensive assessment index of FLAM was explored based on radar chart assessment mean. The results indicate that FGDA with high alkali minerals and flocculent sphere morphology promotes the improvement of dispersivity and compatibility and the generation of homogeneous integral structure. Incorporating FGDA in FGDA-LF composite filler degrades its apparent density and elevates fineness and hydrophilic coefficient. Under MIST hydrodynamic damage, FLAM demonstrates the larger RMS and TSR than asphalt mixture with LF, accompanied by smaller attenuation compared to hydrostatic treatment. FLAM with F3 reveals the lowest rutting depth of 8.65 mm and creep slope of 1.92 × 10−4 and the largest comprehensive assessment index of 0.9998, indicating its optimal comprehensive moisture susceptibility. It is suggested that 30% FGDA might be an appropriate substitution amount for LF in FLAM.