Flue Gas Desulfurization Research Articles

Effect of Al2(SO4)3 Additive on the Properties of Calcined Gypsum Prepared from Flue Gas Desulfurization

In order to upgrade the utilization of flue gas desulfurization (FGD) gypsum, crystal modifier aluminum sulfate (Al2(SO4)3) was added into FGD gypsum to prepare calcined gypsum by calcining at normal pressure, and the effect of Al2(SO4)3 addition on the performance of calcined gypsum was studied. The results show that the addition of Al2(SO4)3 to FGD gypsum is slightly beneficial to promote the crystallization of hemihydrate gypsum (HH) along the a-axis direction. The Al2(SO4)3 addition also has a quick-setting effect on gypsum plaster during the hydration process, meanwhile inhibiting the growth of the (020) crystal plane of dihydrate gypsum (DH), then promoting uniform growth and aggregation along the c-axis. The close stacking makes hardened gypsum body dense and improves the strength of calcined gypsum. The strength of calcined gypsum prepared by calcining FGD gypsum with Al2(SO4)3 of 0.6 wt.% at 170 ℃ for 2 h is the highest. 2 h and 7 d flexural strength are 3.80 MPa and 7.20 MPa, and 2 h and 7 d compressive strength are 9.05 MPa and 19.23 MPa, respectively. In addition, 2 h flexural and compressive strength of the calcined gypsum with 0.6 ~ 1.0 wt.% of Al2(SO4)3 prepared at 170 ~ 180 ℃ for 2 h increase by 16 ~ 22 % and 20 ~ 33 %, respectively, which is very advantageous for the high value-added reuse of FGD gypsum for the preparation of high-quality calcined gypsum.

Deep learning and big data mining for Metal–Organic frameworks with high performance for simultaneous desulfurization and carbon capture

Carbon capture and desulfurization of flue gases are crucial for the achievement of carbon neutrality and sustainable development. In this work, the “one-step” adsorption technology with high-performance metal–organic frameworks (MOFs) was proposed to simultaneously capture the SO2 and CO2. Four machine learning algorithms were used to predict the performance indicators (NCO2+SO2, SCO2+SO2/N2, and TSN) of MOFs, with Multi-Layer Perceptron Regression (MLPR) showing better performance (R2 = 0.93). To address sparse data of MOF chemical descriptors, we introduced the Deep Factorization Machines (DeepFM) model, outperforming MLPR with a higher R2 of 0.95. Then, sensitivity analysis was employed to find that the adsorption heat and porosity were the key factors for SO2 and CO2 capture performance of MOF, while the influence of open alkali metal sites also stood out. Furthermore, we established a kinetic model to batch simulate the breakthrough curves of TOP 1000 MOFs to investigate their dynamic adsorption separation performance for SO2/CO2/N2. The TOP 20 MOFs screened by the dynamic performance highly overlap with those screened by the static performance, with 76 % containing open alkali metal sites. This integrated approach of computational screening, machine learning, and dynamic analysis significantly advances the development of efficient MOF adsorbents for flue gas treatment.

Improving Fine Particle Removal Using a Single-Channel Slit Bubbling Device in Wet Flue Gas Desulfurization System.

To improve the cleanliness of coal-fired power plants' particulate matter emissions, a novel device (single-channel slit bubbling particle removal device (SCSB-PRD)) is proposed to improve the wet flue gas desulfurization system's (WFGDs) collaborative particle removal effect. Actual coal-fired flue gas was used to test the particle removal performance. The results showed that the flue gas temperature had no obvious effect on the scrubbing effect of the SCSB-PRD. The scrubbing space, scrubbing liquid volume, and flue gas flow rate effectively changed the gas-liquid flow state, and the bubbling state was the key factor in particle removal. The jet-bubbling contact state was more conducive to removing particles than the foam bubbling state. The jet-bubbling state improved the removal efficiency of fine particles by approximately 30% compared to the foam bubbling state. The device operated in a single stage, and the removal performance of the particulate matter reached more than 60%. Even the submicron particles had a satisfactory removal performance of greater than 50%. The particulate matter concentration at the outlet of the WFGDs was reduced to less than 10 mg/m3, which provides a feasible transformation path for ultraultra-low emissions of particulate matter from coal-fired power plants.

Experimental study on integrated desulfurization and denitrification of low-temperature flue gas by oxidation method

In this paper, TiO2 catalysts doped with different Fe contents (Fe-TiO2 catalysts) were prepared by coprecipitation method and the Fe loading capacity was optimized, and then the integrated pollutant removal experiment was conducted, in which TiO2 doped with Fe as catalyst and H2O2 as oxidant. The results show that under the condition of constant H2O2/(SO2 + NO) molar ratio, low concentration of SO2 can promote the oxidation and removal efficiency of NO, while high concentration of SO2 can inhibit the removal of NOx. The pollutant removal efficiency is proportional to the amount of catalyst, liquid–gas ratio and pH value of the absorbing solution. The optimal experimental conditions are H2O2/(SO2 + NO) molar ratio 1.5, space velocity ratio 10,000 h−1, H2O2 mass fraction 10 wt%, liquid gas ratio 10, pH 10. Correspondingly, NO oxidation efficiency reaches 88%, NOx removal efficiency 85.6%, and SO2 is almost completely removed. The microstructure of the catalyst before and after the reaction was characterized, and the crystal structure did not change obviously. However, with the deepening of the reaction, the specific surface area of the catalyst decreases, and the catalytic effect decreases slightly.

The production of artificial aggregates with flue gas desulfurization ash: Development of a novel carbonation route

Using solid waste to absorb CO2 in the production of aggregates is an efficient approach, which can reduce CO2 emissions and improve the recycling of solid waste. However, a challenge lies in addressing the cracking issues of aggregates prepared by the calcium oxide (CaO) system, particularly those containing flue gas desulfurizati ash (FGDA), during the direct carbonation process. This study presents a novel carbonation route combining air curing (AC) and CO2 curing (CC) under industrial flue gas conditions that effectively resolves the cracking problem of FGDA. The results show that under the optimized conditions (6 % CaO, 2 % Na2SO4, 3 days of AC, and 12 h of CC), the FGDA can be used to produce the flue gas desulfurization ash artificial aggregate (FGDAA), with pellet strength and water absorption of 3.11 MPa and 16.87 %, respectively. The CaCO3 forms during the carbonation, which improves pellet strength and decreases water absorption, except for the high CaO content (8 %) or AC age over 3 days. This shows that this method has clear requirements for the CaO content in solid waste. By developing a low-cost and energy-efficient carbonation process, FGDAA offers significant advantages in the construction field. With a production cost of only $5.14 per ton and a shorter curing time, it is environmentally sustainable and has a low global warming potential of 52.68 kg CO2-Eq. Although its compressive strength of 32.52 MPa is slightly lower than some conventional aggregates, FGDAA is still suited for applications such as road construction and mine backfill.

Multivariate state estimation-based condition monitoring of slurry circulating pumps for wet flue gas desulfurization of power plants

The slurry circulating pump, a crucial component of wet flue gas desulfurization (WFGD) systems, often encounters faults such as impeller and bearing box damage due to limestone slurry's intense abrasion, corrosion, and cavitation. The various operating conditions, including frequent switching and rapid frequency variations of the slurry circulating pump will make the working environment worse undoubtedly. To ensure the process safety and operation efficiency of the WFGD system, this study proposed a condition monitoring (CM) method based on a novel multivariate state estimation technique (MSET), which can realize the fault early warning of the slurry circulating pump. To improve the accuracy of the conventional MSET, a memory matrix (MM) construction method based on K-means algorithm is proposed, which can provide a MM that varies with the operating condition of real-time observed vectors. In typical cases of predicting the pump’s B-phase current under normal conditions, the root mean square error (RMSE) of our method is 0.25 A, much smaller than that of the conventional MSET method (2.08 A). On the other hand, the computation time of our method remains short (about 20 s) compared to other models (e.g., MEST aided with K-nearest neighbour model needs about 19,000 s) adaptive to varying conditions for over 3000 samples. Also, the proposed CM method can effectively provide early fault warning for impeller damage and bearing box damage of the slurry circulating pump, with 8 days and 1 day in advance, respectively. This can win enough time to inspection & maintenance before troubleshooting.

Flue Gas Desulfurization Products Use on Agricultural Land Use Systems

The Flue gas desulfurization (FGD) process is a set of technology that is used to remove the sulphur dioxide (SO2) present in the flue gas, which is exhausted from the thermal power plant during electricity generation. In FGD equipment, high calcium-containing sorbent materials are sprayed, which will react with the SO2 present in the flue gas and result in the formation of calcium sulphite and FGD gypsum etc. these formed waste materials are known as FGD products. The FGD products can be used in agricultural land for the amelioration of the soil acidity, salinity and alkalinity, it improves the soil’s physical property, reduce the runoff rate etc. Now a day around two per cent of generated FGD products is used in the agricultural field. As some of the FGD products may contain heavy metals, their direct use in the agriculture field may cause environmental hazards. To avoid environmental pollution before its direct use the chemical properties of the product have to be thoroughly checked. So by the use of these materials in the agricultural field, we can effectively convert waste material into useful products.

Environmental Health Risk Analysis of Sulfur Dioxide (SO2) Inhalation Exposure in Ambient Air Among the Tirtonirmolo Community, Bantul.

Introduction: Sulfur dioxide (SO2) is one of the gases that can pollute the ambient air and cause respiratory irritation. This study aims to determine the characterization of health risk and risk management of sulfur dioxide (SO2) exposure to prevent health impact in the Tirtonirmolo community, Bantul. Methods: This study was a quantitative descriptive research with an Environmental Health Risk Analysis (EHRA) approach. The study subjects were the Tirtonirmolo community in Bantul, with a sample of 110 respondents. The sampling method uses purposive sampling. Results and Discussion: Most respondents are female (74%) with ages over 54 years (52%), and the majority work as housewives (44%). The description of EHRA variables consists of an inhalation rate of 0.83 m3/hour, exposure time of 22 hours/day, exposure frequency of 354 days/year, and exposure duration for real-time projections of 35 years and 30 years for lifetime projections. The SO2 measurement results did not exceed the national quality standard, with the highest concentration being on Madukismo Road, with a concentration of 11.72 μg/m3. The dose-response analysis uses data from the US-EPA, which is 0.026 mg/kg/day. The real-time average intake value is 0.0039 mg/kg/day, and the 30-year lifetime average intake value is 0.0033 mg/kg/day. Conclusion: All respondents from this study had an RQ value<1, both in the RQ for real-time and lifetime. Risk management needs to reduce health risk by using masks when doing outdoor activities and installing Flue Gas Desulfurization (FGD) in factories that emit SO2 emissions.

Experimental Study on the Properties and Hydration Mechanism of Gypsum-Based Composite Cementitious Materials

In order to achieve the resourceful, large-scale and high-value utilization of bulk industrial solid wastes such as flue gas desulfurization gypsum (FGDG), fly ash (FA) and ground blast furnace slag (GGBS), and to reduce the dosage of cementitious materials, orthogonal experimental methods were used to prepare composite cementitious materials based on the principle of synergistic coupling and reconstruction of multi-solid wastes. Through the method of extreme difference and ANOVA, the influence law of different factor levels on the performance of the cementitious materials was studied, and the maximum compressive strength of cementitious materials was reached when the ordinary Portland cement (OPC) dosage was 20%, the FGDG dosage was 56%, the FA dosage was 19.2% and the slag dosage was 4.8%, and the W/B was 0.55. The hydration products and microscopic morphology of the cementitious materials were analyzed by means of XRD, SEM and MIP techniques, so as to elucidate the complex synergistic hydration mechanism, and then to determine the more optimal group distribution ratio. The results show that the hydration reaction between FGDG and OPC can be synergistic with each other, and C-A-H further generates AFt under the action of SO42−, and at the same time, it plays the role of alkali-salt joint excitation for FA–GGBS, generates a large amount of cementitious materials, fills up the pores of the gypsum crystal structure, and forms a dense microstructure.

Outstanding performance of reproducible sulfureted Fe-Ti spinel for the centralized control of Hg (both gaseous Hg0 and aqueous Hg2+) emitted from coal-fired power plants with seawater flue gas desulfurization

The emission of aqueous Hg2+ into the sea during seawater flue gas desulfurization (SFGD) is of great concern. In this study, a novel technology for the centralized control of Hg discharged from coal-fired power plants (CFPPs) with SFGD was developed using sulfureted Fe-Ti spinel as a magnetic and regenerable sorbent to sequentially adsorb unoxidized gaseous Hg0 from flue gas and aqueous Hg2+ from desulfurized seawater. The sulfureted Fe-Ti spinel exhibited an excellent ability to adsorb gaseous Hg0 and aqueous Hg2+. Although SO2 in the flue gas and Fe2+ released from sulfureted Fe-Ti spinel both promoted Hg2+ reduction to Hg0, the sulfureted Fe-Ti spinel displayed a moderate ability to adsorb Hg0 in seawater. Hence, there was a critical Hg2+ concentration for Hg0 re-emission (19.6 μg/L). Hg0 re-emission was completely suppressed by sulfureted Fe-Ti spinel addition, as aqueous Hg2+ concentration consistently remained below the critical concentration due to its excellent Hg2+ adsorption rate. Therefore, the alternate capture of gaseous Hg0 in flue gas and aqueous Hg2+ in desulfurized seawater by sulfureted Fe-Ti spinel may be a promising technology for the centralized control of Hg discharged from CFPPs equipped with SFGD to both atmosphere and sea.

Effects of flue gas desulfurization gypsum and clover planting on qualities of soil and winter jujube in coastal saline-alkali orchard of north China

Effects of flue gas desulfurization gypsum and clover planting on qualities of soil and winter jujube in coastal saline-alkali orchard of north China

Preparation of α-High Strength Gypsum from Flue Gas Desulfurization Gypsum Pretreated by Hydrothermal-aging Method

Preparation of α-High Strength Gypsum from Flue Gas Desulfurization Gypsum Pretreated by Hydrothermal-aging Method

Modeling based on machine learning to investigate flue gas desulfurization performance by calcium silicate absorbent in a sand bed reactor

Flue gas desulfurization (FGD) is a critical process for reducing sulfur dioxide (SO2) emissions from industrial sources, particularly power plants. This research uses calcium silicate absorbent in combination with machine learning (ML) to predict SO2 concentration within an FGD process. The collected dataset encompasses four input parameters, specifically relative humidity, absorbent weight, temperature, and time, and incorporates one output parameter, which pertains to the concentration of SO2. Six ML models were developed to estimate the output parameters. Statistical metrics such as the coefficient of determination (R2) and mean squared error (MSE) were employed to identify the most suitable model and assess its fitting effectiveness. The random forest (RF) model emerged as the top-performing model, boasting an R2 of 0.9902 and an MSE of 0.0008. The model's predictions aligned closely with experimental results, confirming its high accuracy. The most suitable hyperparameter values for RF model were found to be 74 for n_estimators, 41 for max_depth, false for bootstrap, sqrt for max_features, 1 for min_samples_leaf, absolute_error for criterion, and 3 for min_samples_split. Three-dimensional surface plots were generated to explore the impact of input variables on SO2 concentration. Global sensitivity analysis (GSA) revealed absorbent weight and time significantly influence SO2 concentration. The integration of ML into FGD modeling offers a novel approach to optimizing the efficiency and effectiveness of this environmentally crucial process.

Performance Evaluation of Inerter-Based Dynamic Vibration Absorbers for Wind-Induced Vibration Control of a Desulfurization Tower

High-rise flue gas desulfurization towers are susceptible to wind loads, which can cause instability and failure in the along-wind and across-wind directions. The tuned mass damper (TMD) has been widely applied in the wind-induced vibration control of high-rise structures. To enhance the control performance and reduce the auxiliary mass of TMD, this study focuses on inerter-based dynamic vibration absorbers (IDVAs) for controlling the vibration response of a desulfurization tower. The dynamical equations of the tower–IDVA systems are established under wind loads, and a parameter optimization strategy for IDVAs is proposed by using the genetic algorithm. The performance of the traditional TMD and six IDVAs in the vibration control of the tower are systematically compared. Numerical simulations demonstrate that both the TMD and IDVAs can substantially mitigate the vibration response of the tower. However, compared to the TMD with the same response mitigation ratio, more than 34% of the auxiliary mass can be reduced by two optimal IDVAs. In addition, the energy dissipation enhancement and lightweight effect of the two IDVAs are explained through parametric studies.

Dry desulphurisation of gas streams using KCC-1 mesoporous silica functionalised with deep eutectic solvents.

Sulphur dioxide, a toxic gas pollutant, is mainly generated by the combustion of fossil fuels and the smelting of sulphur-bearing mineral ores. Removal of SO2 gas or desulphurisation can be accomplished in industries using a variety of processes; the most efficient is wet flue gas desulphurisation (FGD). However, wet FGD has challenges, such as the requirement for wastewater treatment, excessive water usage, and the necessity for chloride protective coating. Despite having a lesser adsorption capacity than wet FGD, dry FGD can efficiently remove SO2 from the effluent gas stream and avoid the issues associated with wet FGD, provided that the sorbents are modified and regenerable. An alternative dry desulphurisation strategy by using fibrous mesoporous silica (KCC-1) modified with deep eutectic solvents (DES), choline chloride-glycerol (DES1) and choline chloride-ethylene glycol (DES2) is studied in this paper. KCC-1 modified with DES1 is found to increase SO2 adsorption capacity to 4.83 mg g-1, which is 1.73 times greater than unmodified KCC-1 and twice higher than KCC-1 modified with DES2 attributed to the sorbent's high porosity. Increasing reaction temperature and SO2 concentration reduce the adsorption capacity to 1.73 mg g-1 and 2.73 mg g-1, respectively. The Avrami kinetic model and the Toth isotherm model best reflect SO2 adsorption on the modified KCC-1, indicating that SO2 molecules are adsorbed exothermically in multilayer adsorption on a heterogeneous surface through a combination of physical and chemical processes. The higher SO2 adsorption capacity of the modified KCC-1 suggests that choline chloride-glycerol can provide additional sites for SO2 adsorption in dry FGD technology.

Co0 anchored on Co/N co-doped porous carbon material induces H migration to accelerate sulfite oxidation and Hg(ii) adsorption in flue gas desulfurization

The low oxidation rate of (NH4)2SO3 and the coexistence of Hg(ii) in desulfurization liquids restrict sulfur recovery for use as a high-value fertilizer.

Effect of dry desulfurization ash as a filler on asphalt pavement performance

This study aims to explore the feasibility of using dry flue gas desulphurization ash (DFGDA) as a filler in asphalt pavements. Two DFGDA materials were added into the base asphalt with different mineral powder proportions to prepare asphalt mastic and mixture, and the pure mineral powder asphalt mastic and mixture were used as the blank control group to evaluate the properties of DFGDA-doped asphalt mastic and mixture. The results show that the addition of DFGDA can improve the high-temperature rheological property and reduce the low-temperature rheological property of asphalt mastic; similarly, the high-temperature stability of asphalt mixture can be greatly improved, while its low-temperature performance and water stability are reduced; despite these decreases, all outcomes still meet the requirements of relevant specifications. No chemical reactions are observed between DFGDA and asphalt, indicating that the physicochemical properties of fillers are responsible for the change in the properties of DFGDA-doped slurry and mixture. Notably, the DFGDA-added asphalt mixture does not bring additional negative effects to the environment. Based on cost analysis, the high-quality use of DFGDA in asphalt mixture can save direct material costs of about $920,000 per 100 kilometers of asphalt road construction. In summary, the application of DFGDA in the asphalt mixture can not only meet the basic performance requirements of asphalt pavements but also greatly save material costs and protect the environment.

DESULFURIZATION OF FLUE GASES OF THERMAL POWER PLANTS WITH OBTAINING POTASSIUM-MAGNESIUM FERTILIZER (KALIMAGNESIA)

A new method of flue gas desulfurization with the production of a valuable is proposed. The essence of the method is to pass flue gases through a scrubber (Venturi) filled with magnesium hydroxide suspension. At the same time, SO2 of the flue gases will react with magnesium hydroxide according with the formation of magnesium sulfite. Crystals of magnesium sulfite are able to interact with new portions of SO2 and turn into hydrosulfite. As a result of such "washing" of flue gases, a suspension of sparingly soluble salt MgSO3∙6H2O in a 12-15% solution of MgSO4 is obtained. Magnesium hexahydrate will precipitate as large crystals and be separated in a hydrocyclone. Separated crystals of magnesium sulfite will be oxidized under the influence of air oxygen to magnesium sulfate.

Influence of Reaction Parameters on Solid Outputs in CO2 Mineralization of Desulfurized Gypsum

Flue gas desulfurization gypsum is the main solid byproduct generated during the limestonegypsum wet desulfurization process in coal-fired power plants. This byproduct is produced in large quantities annually, and ineffective management or disposal can lead to significant environmental damage and land resource wastage. This study investigates how reaction conditions affect CO2 mineralization of desulfurization gypsum, focusing on the purity of the resultant solid minerals, the rate of carbonation of CaSO4·2H2O, and the proportion of vaterite in the produced calcium carbonate. The experimental findings suggest that an increase in ammonia solution concentration enhances the purity and carbonation rate of calcium carbonate from CaSO4·2H2O. Additionally, a higher CO2 flow rate speeds up the mineralization process but may decrease CO2 capture efficiency; however, an optimal increase in CO2 flow can reduce the Ca2+ to CO32- ratio, facilitating the formation of vaterite calcium carbonate. The solid-to-liquid ratio in the reaction does not generally impact the purity or carbonation rate of calcium carbonate but increasing this ratio leads to higher supersaturation of the solution, slowing the conversion of vaterite to calcite and increasing the vaterite content. However, this effect diminishes past a certain point. This research serves as a basis for refining the direct mineralization conditions for CO2 in desulfurization gypsum processes, aiming to optimize the conditions for producing high-quality vaterite-type calcium carbonate.

The Leaching and Kinetics of Magnesium in Phosphate Ore Slurry during FGD Process

The phosphate ore reserves in China are very large, but the overall quality is poor, and the magnesium impurity in phosphate ore is not conducive to the production of phosphorus chemical products. Recovery of sulfur dioxide from exhaust gas by phosphate slurry is a new desulfurization technology developed in recent years. During SO2 removal from flue gas by phosphate ore slurry, in phosphate ore magnesium can be simultaneously reduced. The magnesium leaching process could be described by the reaction-controlled shrinking core model. The leaching process of magnesium from phosphate ore slurry in FGD process includes 5 steps and 10 steps, which describes a gas-liquid-solid three-phase complete reaction process of removing magnesium from industrial flue gas desulfurization of phosphate slurry. In this study, a three-phase mass transfer kinetics model was established to find the controlling factors of the desulfurization reaction rate of the magnesium removal system of phosphate ore slurry in the FGD Process, and the research showed that the gas film resistance was the key control step, the solid film resistance was negligible. The reaction relation of desulfurization and removal of magnesium from phosphate slurry was obtained as k=3.766and#215;e-10318.39/RT.