Mercury Control Research Articles

Emission factors of mercury and particulate matters, and in situ control of mercury during the co-combustion of anthracite and dried sawdust sludge

Anthracite and dried sawdust sludge (DSS) were demonstrated as a complementary combination. Since air pollution has attracted great concern, this paper studies the emission characteristics of mercury and particulate matters (PMs) during the co-combustion process. The results indicated that no Hg2+ was produced in all cases. The Hg0 emission factor decreased significantly with the increasing of DSS. The rising temperature from 800 to 900 °C slightly promoted the Hg0 emission, but the further increasing temperature caused a decreasing of Hg0 emission. Oxygen-enrich atmosphere accelerated the release of Hg0 from anthracite, but the DSS combustion was independent on the atmospheric conditions. The emission factor of PMs for DSS was 10.5 ± 1.7 mg/kg which was 9 times higher than that of anthracite combustion (95.2 ± 7.7 mg/kg). The results of in situ control of Hg0 demonstrated the co-combustion of fuel and Ca-based additives could not deeply reduce Hg0 emission, however the integrated approach of gas phase oxidation combined with wet absorption was satisfactory in terms of Hg0 control, and the way of post-combustion injection was better, the oxidation efficiencies of Hg0 reached 62.5%. The main existing forms of mercury were determined as HgSO4 and HgX2 (X: Br or Cl) by XPS, the reaction mechanism of Hg0 removal was proposed accordingly.

Unveiling Adsorption Mechanisms of Elemental Mercury on Defective Boron Nitride Monolayer: A Computational Study

The control of mercury in flue gas is challenging, especially that of elemental mercury (Hg0). Recently, many researchers have focused on various mercury removal technologies. Here, by performing density functional theory (DFT) calculations, we systematically studied the adsorption of Hg0 on several experimentally available hexagonal boron nitride (h-BN) nanosheets with no defects, nitrogen vacancies (VN), boron vacancies (VB), and both nitrogen and boron vacancies (VN+B) as well as their structures and electronic properties. Our calculation results show that the presence of VN, VB, and VN+B enhances the adsorption energies of Hg0 by 9, 45, and 214 kJ/mol, respectively. Moreover, a more negative potential at the VB and VN+B sites makes the h-BN-VB and h-BN-VN+B surfaces more reactive than those of h-BN and h-BN-VN. The partial density of states analysis reveals that the Hg atom interacts firmly with surface B or/and N atoms through orbital hybridization. The trend of the equilibrium constant implies that ...

Mercury Interaction on Modified Activated Carbons under Oxyfuel Combustion Conditions

Mercury pollution is a cause for concern that requires global action. The most demonstrated and commercially available technology for mercury control is pulverized activated carbon injection. During oxy-coal combustion, the elevated concentrations of SOx, the moisture level in the flue gas, and the recirculation streams may affect the performance of activated carbons as mercury sorbents. This works evaluates mercury oxidation and capture using impregnated-activated carbons. In this study a novel aspect is considered by the application of a novel thermal desorption procedure for mercury species identification and the elucidation of the interaction mechanism. The results show oxidation efficiencies ranging from 85% to 96%. The mercury is partially retained in the solid by chemical adsorption. The formation of new mercury species HgS, HgI2, and HgO by the interaction was established.

Simultaneous removal of NO and Hg0 from simulated flue gas over CoOx-CeO2 loaded biomass activated carbon derived from maize straw at low temperatures

To rationally utilize agricultural wastes and expediently simultaneous control of elemental mercury (Hg0) and NO, a series of CoOx-CeO2 loaded maize straw derived biomass activated carbon (CoCe/BAC) samples were applied for simultaneous NO and Hg0 removal. These samples’ physicochemical characteristics were characterized by BET, SEM, XRD, NH3-TPD, H2-TPR, XPS and FTIR. 15%Co0.4Ce0.6/BAC yielded prominent Hg0 removal efficiency (96.8%) and superior NO removal efficiency (84.7%) at 230 °C. The separate or synchronous deactivation effects of 400 ppm SO2 and 5%H2O were detected. The interaction between NO removal and Hg0 removal was investigated, the results demonstrated that abundant Hg0 exhibited very slightly inhibitory effect on NO removal, and NH3 negatively affected Hg0 removal, whereas NO mildly boosted Hg0 removal in presence of O2. The characterization analyses indicated the excellent performance of 15%Co0.4Ce0.6/BAC could be ascribed to its better texture properties, lower crystallinity and stronger redox ability. Besides, a synergetic effect appeared between cobalt oxide and cerium oxide, resulting in generating more Ce3+ and Co3+ to induce more anionic defects and produce more active oxygen and oxygen vacancies. The removal mechanisms of NO and Hg0 were systematically investigated, and NO reduction reactions were mainly assigned to the Langmuir-Hinshlwood mechanism while both adsorption and Hg0 oxidation contributed to Hg0 removal. Meanwhile, Hg0 oxidation corresponded to the Mars-Masson mechanism prevailed gradually with the increase of reaction time.

Control of mercury and methylmercury in contaminated sediments using biochars: A long-term microcosm study

The effectiveness of activated carbon and four types of biochar, switchgrass (300 °C and 600 °C), poultry manure (600 °C), and oak (∼700 °C) with respect to mercury (Hg) and methylmercury (MeHg) control was assessed in microcosm experiments carried out for 524 d. Early in the study (<30 d), minimal differences in concentrations of <0.45-μm filtered total Hg (THg) in control and 5% biochar-amended systems were observed. At later stages, THg concentrations in the amended systems decreased to 8–80% of concentrations in the sediment controls. Aqueous concentrations of MeHg were generally lower in the amended systems than in the controls, with an initial peak in MeHg concentration corresponding to the onset of iron and sulfate reduction (∼40 d) and a second peak to methanogenic conditions (∼400 d). Pyrosequencing analyses indicate the microbial communities initially associated with fermenters and later shifted to iron-reducing bacteria (FeRB), sulfate-reducing bacteria (SRB), and methanogens. These analyses also indicate the existence of 12 organisms associated with Hg methylation in all systems. Community shifts were correlated with changes in the concentrations of carbon sources (dissolved organic carbon (DOC) and organic acids) and electron acceptors (NO3−, Fe, and SO42−). Co-blending of biochars with Hg-contaminated sediment can be an alternative remediation method for controlling the release of Hg and MeHg, but the potential for Hg methylation under some conditions requires consideration.

Improving Flue Gas Mercury Removal in Waste Incinerators by Optimization of Carbon Injection Rate.

This study tested the mercury emission characteristics of six municipal solid waste incinerators (MSWIs) and recommended future mercury control via adjusting operational parameters. The results indicated that over 99% of the mercury in solid wastes ended in fly ash and flue gas, of which 3.3-66.3% was emitted to air through stack gas. Mercury in the stack gas was mainly in the form of oxidized mercury (Hg2+), the proportion (65.4-89.0%) of which was far higher than previous estimation (15%). Mercury removal efficiencies (MRE) of the tested incinerators were in the range of 33.6-95.2%. The impact of waste incineration capacity, gas flow, fly ash yield, and activated carbon (AC) injection on MRE were analyzed. We found that the MRE was significantly linearly correlated to the ratio of AC injection and fly ash yield (correlation coefficient = 0.98, significance <0.01). AC injection value is determined based on the control of dioxin emissions without considering mercury control in traditional design. To increase MRE of MSWIs, the AC injection should increase from around 100 mg·Nm-3 to 135 mg·Nm-3 for grate furnace combustor and 170 mg·Nm-3 for circulation fluidized bed combustor, so as to reach a MRE of 90%.

Effects of oral exposure to inorganic mercury on the feeding behaviour and biochemical markers in yellowfin bream (Acanthopagrus australis)

Mercury is a known toxic metal, but studies on the effects of inorganic mercury ingestion in aquatic organisms are scarce. The present study aimed to investigate changes in feeding behaviour and biomarkers (lipid peroxidation, acetylcholinesterase, glutathione S-transferase and catalase activities) of yellowfin bream (Acanthopagrus australis) after ingestion of inorganic mercury (control: 0.2 mg kg−1, low: 0.7 mg kg−1, medium: 2.4 mg kg−1 and high: 6 mg kg−1) over 16 days. After 4 days, exposed fish attempted feeding more often, and showed a significantly lower eating success than controls. However, these differences became less notable with longer exposure periods. Most biochemical markers varied over time, regardless of mercury treatment. However, biomarker responses to mercury were also observed, mostly with increased exposure period and were dependant on the tissue analysed. This study showed that fish can recover from initial feeding behaviour effects of inorganic mercury, but showed delayed response in tissue biomarkers.

Insights into the heterogeneous Hg0 oxidation mechanism by H2O2 over Fe3O4 (0 0 1) surface using periodic DFT method

The gaseous oxidation process for Hg0 oxidation is regarded as an efficient and low-cost option for mercury control in solid fuel combustion devices. The heterogeneous Hg0 oxidation by gaseous H2O2 over Fe3O4 (0 0 1) surface was calculated using periodic density functional theory (DFT) method to gain a fundamental understanding of Hg0 oxidation mechanism on H2O2/Fe3O4 (0 0 1) surface. The results showed that on the Fe3O4 (0 0 1) surface, the Fetet site (A layer) is more active than the Feoct site (B layer). H2O2 can easily undergo dissociation process to form two OH radicals, which have highly active in Hg0 oxidation over the A layer. The Mulliken charge population analysis showed that a large amount of electron transfer occurred from Hg0 to the produced OH. The calculated reaction energy barriers suggested that the interaction between OH and Hg0 is exothermic and Hg0 oxidation processes by OH produced from H2O2 are thermodynamically and kinetically favorable. In addition, Hg0 oxidation processes on the H2O2/Fe3O4 (0 0 1) surface may simultaneously undergo through three different pathways. The possible Hg-OH product will easily desorbs from the surface, whereas the Hg(OH)2 is stable on the surface and belongs to chemisorption. The detailed mechanism for the oxidation reaction over Fe3O4 makes it an attractive method for Hg control from flue gases.

DOCUMERICA and the Power of Environmental History

DOCUMERICA and the Power of Environmental History

Mercury removal and its fate in oxidant enhanced wet flue gas desulphurization slurry

Mercury is a toxic heavy metal that, once emitted or released, persists in the environment and circulates between air, water, sediments, soil and living creatures. Therefore, international governments and other authorities are taking measures to control mercury emissions from various sources. Despite many efforts, mercury remains a problematic pollutant in coal-fired installations in regards to differentiation of existing forms and their behavior in flue gas stream and purification units. Scientists try to understand its behavior in the flue gas and to capture it in one place, employing processes of adsorption, absorption, membranes or different catalysis. At the same time, researchers are also developing efficient and economically feasible technologies for mercury control. One such technology involves the capture of mercury in flue gases via gas-cleaning units through co-benefit application. Examples include, for instance, carbon injection in ESP, catalytic conversion in SCR unit, and absorption in a wet desulfurization scrubber.This paper outlines a mercury capture method developed in American and Polish laboratories and will present the pilot-scale research with emphasize on the mercury behavior in the slurry with and without any added reagents.

Power Plant Bromide Discharges and Downstream Drinking Water Systems in Pennsylvania.

Coal-fired power plants equipped with wet flue gas desulfurization (FGD) systems have been implicated in increasing bromide levels and subsequent increases in disinfection byproducts at downstream drinking water plants. Bromide was not included as a regulated constituent in the recent steam electric effluent limitations guidelines and standards (ELGs) since the U.S. EPA analysis suggested few drinking water facilities would be affected by bromide discharges from power plants. The present analysis uses a watershed approach to identify Pennsylvania drinking water intakes downstream of wet FGD discharges and to assess the potential for bromide discharge effects. Twenty-two (22) public drinking water systems serving 2.5 million people were identified as being downstream of at least one wet FGD discharge. During mean August conditions (generally low-flow, minimal dilution) in receiving rivers, the median predicted bromide concentrations contributed by wet FGD at Pennsylvania intake locations ranged from 5.2 to 62 μg/L for the Base scenario (including only natural bromide in coal) and from 16 to 190 μg/L for the Bromide Addition scenario (natural plus added bromide for mercury control); ranges depend on bromide loads and receiving stream dilution capacity.

Environmental geochemistry of mercury in the area of emissions of the Karabashmed copper smelter

Mercury emissions during production of blister copper at the smelter Karabashmed are roughly estimated. The high mercury content in the atmospheric dust, soils, lake sediments of the Karabash geotechnogenic system shows that emissions of the plant are the main source of environmental contamination. The mercury content in soils of residential territory ranges within 0.2–11.4 mg/kg, reaching 15 mg/kg in soils of the impact zone. The maximum mercury content in the bottom sediments of Lake Serebry is 32 mg/kg. The high degree of contamination by other elements of emissions (Cu, Pb, Zn, As, Cd) is also demonstrated. Obtained results justify the need for the instrumental control of mercury in emissions.

Influence of H2O on Hg0 Oxidation in the Simulated Flue Gas in Oxygen-Enriched Combustion

The catalytic oxidation on elemental mercury (Hg0) to water-soluble oxidized mercury (Hg2+) is a good mercury (Hg) control approach for coal-fired power plants, and Hg2+ can be removed by the existing wet flue gas desulfurization (FGD) device. Oxygen-enriched combustion (OEC) is considered as an optimal option for the post CO2 capture among the clean coal combustion technologies. On the basis of the established bench-scale experimental apparatus, this paper studied the influence mechanism of a high H2O concentration on Hg0 oxidation in the simulated flue gas in OEC. The results showed that both the high HCl concentration and the high temperature could improve the Hg0 oxidation in the simulated flue gas above 500 °C and with as high as 30% of H2O content in OEC. A key intermediate reaction step was needed to complete the reaction between Hg0 and HCl. HCl was first oxidized to oxidative Cl by O2. Then, Hg0 was further oxidized by oxidative Cl. The high H2O concentration could inhibit this process of Hg0 oxidation, and the reason was that the high H2O concentration could inhibit the conversion from HCl to oxidative Cl. The inhibitory efficiency of oxidative Cl was affected by both the HCl and H2O concentrations. Added SO2 consumed oxidative Cl in the simulated flue gas with a high H2O content in OEC, which inhibited the oxidation of Hg0. Hg0 oxidation efficiency increased obviously in the heterogeneous flue gas with ash in OEC. The inhibitory effect of H2O on Hg0 oxidation could be weakened in the heterogeneous flue gas in OEC.

Economic evaluation of health benefits of mercury emission controls for China and the neighboring countries in East Asia

Globally, coal-fired power plant (CFPP) is a major source of mercury. China is developing its first National Implementation Plan on Mercury Control, which priorities the control of emissions from CFPPs. While social benefits play an important role in designing environmental policies in China, the benefits associated with mercury control are not yet understood, mainly due to the scientific challenges to trace mercury's emissions-to-impacts path. This study evaluates the benefits of mercury reductions in China's CFPPs for China and its three neighboring countries in East Asia. Four policy scenarios are analyzed following the policies-to-impacts path, which links a global atmospheric model to health benefit analysis models to estimate the economic gains from avoided mercury-related adverse health outcomes under each scenario, and take into account key uncertainties in the path. Under the most stringent scenario, the benefits of mercury reduction by 2030 are projected to be $432 billion (95% CI: $166–941 billion), with the benefits for China and the neighboring countries accounting for 96% and 4% of the total benefits, respectively. Policy scenario analysis indicates that coal washing generates the greatest benefits in the near term, whereas upgrading air pollution control devices maximizes health benefits in the long term.

Comprehensive Evaluation of Mercury Photocatalytic Oxidation by Cerium-Based TiO2 Nanofibers

Efficient and economical technologies are essential to the control of mercury, the emission of which imposes serious health concerns and environmental risks. Photocatalysis is an attractive method for reducing mercury emissions. Considering that titania is widely applied in the photodegradation of toxic contaminants, this study investigated the removal of mercury over cerium-based titania nanofibers (CBTs) at low temperature. According to the results, in the atmosphere containing SO2, both catalyst and UV proposed adverse effect on Hg0 oxidation. The competition between SO2 and Hg0 for active sites and the formation of cerium sulfate are responsible for the deactivation of Hg0 removal capacity. More interestingly, without O2, NO and HCl still exerted a superior promoting effect on mercury removal. Entirely different from the properties under SO2, UV and catalyst both facilitated Hg0 oxidation with the existence of HCl. Meanwhile, effects of the copresence of NO and SO2 on Hg0 removal were further investig...

Mercury emission control: Phase II. Let’s now go passive

The US Environmental Protection Agency’s plan for a National set of standards limiting mercury emission from coal power plants has recently hit a setback. A decision by the US Supreme Court rejected this based on the two available methods having a burdensome cost basis. Moreover, even if the activated charcoal or bromine addition methods do become standard in the US, their cost may still inhibit global implementation. As a result it is timely to develop alternate methods. This paper outlines further development of such an approach. It is based on mercury’s own chemistry. Previous published work discovered that elemental mercury, although volatile, has a propensity for heterogeneous chemistry on warm non-catalytic surfaces. This paper now reports results of a second pilot plant test continuing its clarification, extension and further validation of practicality. It extends data to inexpensive base metal surfaces that can be used and indicates the extent of mercury control possible. This non-catalytic heterogeneous chemistry has been overlooked due to this disguising role of surfaces. It is this that now suggests a passive mitigation method, natural to the system. By providing inserted metal surfaces in the downstream flue gas flow, mercury can be chemically modified and controlled.

Review of Mercury Formation and Capture from CO2-Enriched Oxy-Fuel Combustion Flue Gas

Oxy-fuel combustion is the ideal option among low carbon combustion technologies for post CO2 capture. Mercury in CO2-enriched flue gas must be removed efficiently because mercury can cause metal embrittlement and aluminum corrosion during post CO2 processing. To date, there is little research that has reported mercury speciation, emissions, and removal from the oxy-fuel combustion systems. Therefore, a comprehensive review of mercury chemistry and mercury removal from the oxy-fuel combustion system is necessary. This paper reviews the formation, emission, and removal of mercury from oxy-fuel combustion systems. The aim is to evaluate and summarize the fate of mercury and the status of mercury-control technologies for the oxy-fuel combustion process. It is recommended that the modification of existing ESP, SCR, or FGD systems to enhance mercury control should be developed. The investigation of mercury capture by activated carbon or other low-cost sorbents requires further research to evaluate its suitabil...

Control of Mercury, Dioxins/Furans, and Particulate Matter Emissions from Sewage Sludge Incinerators for Compliance with New US EPA Regulations

Control of Mercury, Dioxins/Furans, and Particulate Matter Emissions from Sewage Sludge Incinerators for Compliance with New US EPA Regulations

A sol-gel Ti-Al-Ce-nanoparticle catalyst for simultaneous removal of NO and Hg0 from simulated flue gas

To optimize simultaneous control of NO and elemental mercury (Hg0) and gain more insight into the mechanisms, nano-sized TiO2-Al2O3-CeO2 materials synthesized via sol-gel method were used for simultaneous removal of NO and Hg0 from simulated flue gas. The physicochemical characteristics of catalysts were characterized by ICP-OES, BET, XRD, SEM, TEM, XPS, H2-TPR and FT-IR. TiAl10Ce20 nanoparticle with the addition of 10wt%Al2O3 showed superior NO removal efficiency (93.41%) and Hg0 removal efficiency (80.54%) in the presence of SCR atmosphere at 300°C. The deactivation effects of 8% H2O and 400ppm SO2 were also reduced by Al addition. In the presence of SCR atmosphere, the capture of Hg0 was inhibited by the existence of NH3, while the presence of Hg0 had little impact on NO removal. The characterization results showed that the excellent performance of TiAl10Ce20 nanoparticle might result from the stronger redox ability, lower crystallinity and better texture properties with highly dispersed Ce species, which were all attributed to Al addition. The mechanisms for simultaneous removal of NO and Hg0 were also proposed on the basis of above results. TiAl10Ce20 nanoparticle developed in this work was considered to be a promising catalyst for simultaneous removal of NO and Hg0.

Elemental mercury adsorption and regeneration performance of sorbents FeMnOx enhanced via non-thermal plasma

Recent laboratory experiments and field tests have demonstrated the potential for modified regenerable materials to be a cost-effective alternative to expensive activated carbon for mercury control in coal-fired power plants. To develop a competitive and commercially viable technology, better mercury capture and regeneration performances of regenerable sorbents are required. For this purpose, non-thermal plasma was used to treat the magnetic sorbents FeMnOx synthesized by co-precipitation. The mercury adsorption tests showed that the treated sorbents with non-thermal plasma had higher mercury removal efficiency than raw sorbents, and longer treatment time resulted in higher efficiency. The main reason was that the content of the high valence manganese oxides and lattice oxygen were greatly increased by non-thermal plasma treatment, and this played a significant role in the mercury removal process. Further analysis showed that the lattice oxygen coming from the stepwise reduction of manganese oxide (MnO2→Mn2O3→MnO) served as an oxidant in the reaction with Hg0. The NO, SO2 and H2O inhibited the mercury adsorption while O2 and HCl promoted mercury removal. High valence of manganese oxides and lattice oxygen were consumed during mercury adsorption, while non-thermal plasma treatment could replenish it and increase mercury removal regeneration performance better than without non-thermal plasma treatment. In summary, the combination of magnetic separation, thermal regeneration and plasma treatment makes FeMnOx an excellent recyclable sorbent for mercury emission control.