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[Display omitted] • Hg0 was removed efficiently from syngas over Fe7SC by adding external O 2. • The introduction of O 2 promoted the oxidation of H 2 S to form S active sites. • Hg0 removal form syngas was proposed to follow the Eley–Rideal mechanism. • HgS was the main mercury species on surface of used sorbent. In this study, a Fe7SC sorbent was prepared via hydrothermal impregnation and used to eliminate Hg0 from simulated syngas. A certain amount of oxygen was introduced to induce targeted H 2 S oxidation to form active surface sulfur species for the enhanced capture of Hg0 over Fe7SC. The effects of the introduced oxygen, temperature, and syngas composition (H 2 S, CO, H 2 , and H 2 O) on Hg0 adsorption performance were investigated. X-ray photoelectron spectroscopy, Hg0-temperature programmed desorption, and density functional theory calculations were performed to elucidate the Hg0 removal mechanism. Fe7SC exhibited a superior Hg0 removal performance (approximately 99.2%) in the presence of H 2 S + O 2 at 150 °C. The interaction between H 2 S and the introduced oxygen was responsible for its superior Hg0 capture capacity. CO and H 2 suppressed Hg0 adsorption, and H 2 O inhibited Hg0 removal owing to competitive adsorption. Results of the Bangham kinetic analysis indicate that Hg0 surface chemisorption is the primary rate-controlling step. Hg0 adsorption on the Fe7SC sorbent may follow the Eley–Rideal mechanism, in which the active sulfur species generated from H 2 S oxidation react with gaseous Hg0 to form HgS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe-Ti spinel exhibited more than 92% Hg0 removal efficiency at 120–180 °C. • Hg0 reaction with H 2 S over Fe-Ti spinel followed the Eley-Rideal mechanism. • Reaction pathway of Hg0 capture was proposed according to characterizations and DFT. A magnetic Fe-Ti spinel sorbent was synthesized by the co-precipitation method and applied to remove gaseous Hg0 from syngas. A superior Hg0 removal performance was achieved in the temperature range of 120–180 °C, and the highest an average removal efficiency of was approximately 95% at 150 °C under simulated syngas. H 2 S was adsorbed on the Fe-Ti spinel surface，which generated active sulfur species, and enhanced the Hg0 removal efficiency significantly. CO, H 2 and H 2 O variably suppressed the Hg0 removal performance. H 2 S-pretreatment, X-ray photoelectron spectroscopy (XPS) and Hg0-temperature programmed desorption (Hg0-TPD) results demonstrated that Hg0 reacted with H 2 S over Fe-Ti spinel followed the Eley-Rideal mechanism, in which gas-phase Hg0 reacted with the active surface sulfur species generated from H 2 S oxidation and formed surface-bonded HgS. The surface Fe3+ and surface-active oxygen species were involved in the H 2 S and Hg0 adsorption and transformation process. Stability and regeneration cycling experiments indicated that Fe-Ti spinel exhibited excellent stability for Hg removal and great regeneration ability. Density functional theory (DFT) calculations showed that H 2 S underwent strong chemisorption on the Fe-Ti spinel surface with an adsorption energy of −116.988 kJ/mol, and then H 2 S further dissociated on the sorbent surface to generate active sulfur species, which reacted strongly with gas-phase Hg0 to form HgS. [ABSTRACT FROM AUTHOR]

• Coupling WFGD with wet flue gas condensation desulfurization technology was proposed. • Ca(OH) 2 was used to enhance SO 2 absorption during wet flue gas condensation. • Main influence factors and reaction mechanisms were fully analyzed. • Significant energy-saving potential of coupling desulfurization technology was demonstrated. Limestone–gypsum wet flue gas desulfurization (WFGD) is the most effective desulfurization technique. However, to achieve ultralow SO 2 emissions, the efficiency of WFGD should be improved and its energy consumption reduced. To address these aims, a technology of coupling WFGD with condensation desulfurization using a condensing heat exchanger (CHE) was proposed in this study. The results show that, as the WFGD approaches the limiting desulfurization efficiency, a small increase in the efficiency may cause a high energy consumption. However, the energy consumption can be reduced significantly through the synergistic absorption of SO 2 during the wet flue gas condensation. The synergistic absorption efficiency is affected by the SO 2 concentration at the inlet of the CHE, flue gas flow, and the amplitude and rate of temperature drop. Injecting Ca(OH) 2 into the flue gas during wet flue gas condensation can form dispersive heterogeneous cores of Ca(OH) 2 in the flue gas, thereby enhancing SO 2 mass transfer and improving the desulfurization efficiency considerably. The increased amount of Ca(OH) 2 is small, and the unreacted Ca(OH) 2 can be fully utilized by collecting the condensed solution and returning it to the WFGD system. When the coupling desulfurization technology is applied to achieve ultralow SO 2 emissions, at inlet SO 2 concentrations of 2000 and 4000 mg/Nm3, the circulating pump power consumption decreases by 351–449 kW and 1661.5–2125.5 kW for 300- and 1000-MW units, respectively, demonstrating the significant energy-saving potential of the coupling desulfurization technology. [ABSTRACT FROM AUTHOR]

Particulate matter emitted by fuel combustion has become a major air pollutant. It comes in the form of filterable particulate matter (FPM) and condensable particulate matter (CPM). In the past, people focused on FPM due to its large emission amount. Such active research prompted the rapid development of FPM control technology. At present, FPM is effectively controlled, and its emission concentration is extremely low. By contrast, the emission concentration of CPM is higher than that of FPM and requires immediate attention. Therefore, people are paying close attention to CPM. Nevertheless, CPM is still poorly understood. On the basis of existing research, this study reviews CPM, including its concept, formation mechanism, and hazards. CPM test methods and the factors that affect the accuracy of CPM measurement are also discussed. Improvement methods focusing on CPM measurement are introduced. The results of previous research on CPM characteristics are summarized. Finally, possible CPM control techniques are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ag/Fe-Ti spinel presented higher than 90% Hg0 capture efficiency at 250 °C. • H 2 S was an effective syngas component responsible for Hg0 removal. • Ag enhanced the Hg0 removal performance at 250 °C without sulfur poisoning. • Hg0 removal over Ag/Fe-Ti spinel followed the Langmuir-Hinshelwood mechanism. • HgS and surface sulfur were formed on the surface of spent Ag/Fe-Ti spinel. A series of Ag doping Fe-Ti spinel sorbents (Ag/Fe-Ti spinel) were synthesized using co-precipitation and impregnation methods and employed to remove elemental mercury (Hg0) from syngas at high temperatures (200–350 °C). The role of H 2 S on Hg0 elimination over Ag/Fe-Ti spinel and the Hg0 removal mechanism were systematically investigated by experimental and theoretical methods. N 2 adsorption–desorption, SEM-EDS, XRD, H 2 -TPR and XPS were used to characterize the physicochemical properties of samples. The synthesized Ag/Fe-Ti spinel was tested on a fixed-bed reactor for Hg0 removal from the simulated syngas and showed an average mercury removal efficiency above 90 % at 250 °C. Loading Ag effectively enhanced Hg0 removal activity in high-temperature syngas by generating Ag-Hg alloy via the amalgamation reaction. H 2 S played the most important role in mercury removal, by adsorbing Hg0 on Ag/Fe-Ti spinel sorbent surface to form active sulfur species. H 2 S-pretreatment experiments indicated that the reaction of H 2 S and Hg0 occurred via the Langmuir-Hinshelwood mechanism. Stability and cyclic regeneration experiments indicated that the Ag/Fe-Ti spinel had good regeneration performance and reusability. Density functional theory (DFT) calculation was performed to elucidate that strong chemisorption for H 2 S and HgS occurred over the Ag/Fe-Ti spinel surface with adsorption energies of −300.35 kJ/mol and −408.12 kJ/mol, respectively. XPS and DFT calculations demonstrated the Hg0 removal mechanism, which the chemisorbed Hg0 reacted with active sulfur species to generated surface-bound HgS. Both XPS and Hg0-TPD analysis certified the presence of HgS and elemental S on the surface of spent Ag/Fe-Ti spinel. [ABSTRACT FROM AUTHOR]

• The combination of limestone-based dual-loop WFGD and oxygen-enriched combustion was proposed. • Main influence factors and reaction mechanism were fully investigated. • Effect of CO 2 concentration on desulfurization process of single-loop and dual-loop WFGD was compared. • Dual-loop WFGD has better adaptability to flue gas desulfurization after oxygen-enriched combustion. Oxygen-enriched combustion is the most promising CO 2 emission reduction technology for coal burning. However, the sharp increase in CO 2 and SO 2 concentrations in flue gas after oxygen-enriched combustion poses a new challenge to the subsequent wet flue gas desulfurization (WFGD) system. In this study, limestone-based dual-loop WFGD technology was used to solve this problem. Using a small dual-loop falling-film WFGD experimental system, the effect of CO 2 concentration on limestone dissolution, SO 2 absorption, SIV oxidation, and CaSO 4 crystallization during limestone-based dual-loop WFGD was investigated in detail and compared with single-loop WFGD. The results show that, although an increase in CO 2 concentration is beneficial to SO 2 absorption in the single-loop WFGD system, it is not conducive to limestone dissolution, SIV oxidation, and CaSO 4 crystallization. Compared with single-loop WFGD, in the low pH region of dual-loop WFGD, increasing the CO 2 concentration can also improve the SO 2 absorption efficiency. However, it had no obvious effect on limestone dissolution, SIV oxidation, and CaSO 4 crystallization. In the high pH region of the dual-loop WFGD, although an increase in CO 2 concentration is not conducive to SO 2 absorption, the SO 2 absorption efficiency is still higher than that of single-loop WFGD. The negative effect of increasing the CO 2 concentration on limestone dissolution, SIV oxidation, and CaSO 4 crystallization can be effectively solved by introducing slurry from the high pH region into the low pH region. Therefore, compared with single-loop WFGD technology, dual-loop WFGD is more suitable for flue gas desulfurization after oxygen-enriched combustion. [ABSTRACT FROM AUTHOR]

• The charged atomization technology of organic agglomeration solution was proposed and investigated. • Main influence factors and agglomeration mechanism were fully investigated. • The atomization and agglomeration performance of agglomeration solution before and after charged atomization were compared. • Charged atomization improved the agglomeration ability of organic agglomeration solution greatly. Chemical agglomeration is an effective method for agglomerating fine particles. Generally, an aqueous solution of an organic polymer is used as the agglomeration solution. However, these water-soluble polymers have high viscosity, resulting in a poor atomization effect of the solution, which significantly reduces the probability of collision between the agglomeration solution droplets and particles and further reduces the agglomeration efficiency of particles. To improve the agglomeration efficiency, the charged atomization technology of organic agglomeration solutions was proposed and investigated. The results showed that although the agglomeration effects of different organic agglomeration solutions on particles were different, the agglomeration performance improved after charged atomization. Among the four solutions obtained using the charged atomization technique, sodium carboxymethyl cellulose (CMC) and sodium alginate (SAA) showed the largest improvement in performance. Compared to the uncharged droplet, the agglomeration efficiency of fine particles increased by 53.4% for the 0.01% CMC solution under the charged droplet condition. With an increase in the mass concentration, the agglomeration efficiency of the particles increased but the change rate decreased, and this trend was more apparent after charged atomization. As the concentration increased from 0.03% to 0.1%, the change rates of the relative agglomeration efficiency of CMC before and after charged atomization were 11.2% and 2.4%, respectively. The change in droplet size is among the main reasons for the change in the agglomeration ability of an organic solution. Since the conductivity and viscosity of the solution affect the change in droplet size after charged atomization, it also has an effect on the agglomeration efficiency of the solution. The agglomeration performance of the organic agglomeration solution with high conductivity and low viscosity improved significantly after charged atomization. The particles exhibited characteristics of more compact chains and clusters after charged atomization. [ABSTRACT FROM AUTHOR]

• Novel Fe 2 O 3 /TiO 2 sorbents were synthesized for Hg0 removal from simulated syngas. • Elemental mercury adsorption with H 2 S over the Fe 2 O 3 /TiO 2 sorbents occurred via the Eley–Rideal mechanism. • Surface Fe3+ species and stored oxygen both contributed to H 2 S oxidation and Hg0 capture. Fe 2 O 3 /TiO 2 sorbents synthesized by the sol-gel method were employed to capture elemental mercury in simulated syngas. It was found that Fe 2 O 3 /TiO 2 sorbents exhibited an outstanding Hg0-removal efficiency of over 95% in the temperature range 50–150 °C; however, the Hg0-adsorption capacity was limited by high temperatures (above 150 °C). H 2 S significantly promoted Hg0 capture, whereas CO, H 2 , and H 2 O suppressed Hg0 removal. After a 10-hour adsorption test, and five adsorption–regeneration cycles at 150 °C, the Hg0-removal efficiency was maintained at approximately 95% and 90%, respectively, confirming that the sorbent showed stability and reusability. Hg0 adsorption with H 2 S over the Fe 2 O 3 /TiO 2 sorbents occurred via the Eley–Rideal mechanism, in which active sulfur sites originating from the oxidation of H 2 S reacted with gaseous Hg0 to form HgS. A possible reaction pathway for Hg0 removal has also been proposed. The fresh and spent sorbents were explored by X-ray photoelectron spectroscopy and Hg0-temperature-programmed desorption, indicating that the surface Fe3+ species and stored oxygen both contributed to H 2 S oxidation and Hg0 capture. It can be concluded that Fe 2 O 3 /TiO 2 sorbents appeared to be promising and efficient sorbent for mercury removal from syngas in industrial application. [ABSTRACT FROM AUTHOR]