Seawater Flue Gas Desulfurization Research Articles

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.

Mass flows and characteristic of mercury emitted from coal-fired power plant equipped with seawater flue gas desulphurization

This study investigated the characteristics of mercury emitted from a large-scale coal-fired power plant in Taiwan via intensive sampling campaigns. The air pollution control devices equipped in this coal-fired power plant include selective catalytic reduction, fabric filter and seawater flue gas desulfurization. During three sampling campaigns, mercury concentrations emitted from this large-scale coal fired power plant ranged from 0.04 to 0.35 μg Nm−3. In addition, solid and liquid samples including coal, bottom ash, fly ash and inlet/outlet seawater were collected and analyzed for mercury content to provide the mass flows of mercury in this plant. The results indicate that mercury emitted from this coal-fired power plant is dominated by Hg0, and the emission factor of mercury ranges from 0.37 to 3.37 mg Hg t−1 coal, which is relatively lower than those reported in other studies. The relative enrichment factor of mercury in fly ash (0.23–1.22) is significantly higher than that of bottom ash (0.10 × 10–3–0.89 × 10–3). Although this coal-fired power plant has a relatively low mercury atmospheric emission which accounts for 6.4% of the total mercury output, it is essential to further control mercury released from fly ash (62.6% of the total mercury output) and discharged seawater (33.7% of the total mercury output) to reduce environmental damage and human health effects.

Implementation of Risk Management for Coal Switching in Coal Fired Steam Power Plant

Steam Power Plant is the backbone of electricity sector in Indonesia. Steam Power Plants supply 27.5 GW to the grid, in which 90% of them is coal fired. Today, several Coal Fired Steam Power Plants face a supply problem; consequently, they must procure lower quality of coal. One of them is XYZ Coal Fired Steam Power Plant. Even if there are four candidates of provider to supply coal for a minimum 10 years, it is necessary to make assessment about the effects of coal switching on equipment. The risk assessment focuses on effects of each coal sample on equipment in plant site, especially the equipment closely related to firing process, i.e., boiler, electrostatic precipitator (ESP), and Seawater Flue Gas Desulfurization (SWFGD). Risk Breakdown Structure (RBS) is employed to map problem and problem root in equipment. Risk analysis and evaluation use House of Risk (HOR), meanwhile Net Present Value (NPV) is used to evaluate financial traits. HOR analysis shows one environmental factor, i.e., emission, becomes the highest risk as each coal has high ash content; hence it is necessary to improve emission control. Three of four candidates show high NPV values suitable for the company to maximize profitability.

Assessment of air pollution control technologies to reduce SOx emission from thermal oxidizer for oil and gas industry

Many countries have put in place, various legislations that govern air emission limits/pollutants from the industries. The common pollutants being monitored are Sulphur Oxides (SOx), Nitrogen Oxides (NOx), Carbon Monoxide (CO), Carbon Dioxide (CO2), Volatile Organic Compounds (VOCs), particulate matters and dioxins. In Malaysia, the regulatory requirement aims to regulate emissions of air pollutants from industrial activities including oil and gas, power plants, waste fuel plants and asphalt mixing plants. One of the emission limits under Clean Air Regulation (CAR2014) is emission level for SOx should be less than 600 mg/m3 (reference condition at 3 % of O2, 273 K, 101.3 kPa) whereby sum of SO2 and SO3 expressed as SOx. Excessive SOx emission can affect both health and the environment. Aligning with the regulation requirement, Group Technical Solution (GTS) under PETRONAS has embarked on assessment of technology solutions to meet the emission limit on SOx emission limit for thermal oxidizers which cover new and existing facilities. This paper describes on the work methodology and approach adopted during the assessment. The objective of the assessment is to determine the suitable process technology to reduce SOx emission in order to achieve the desired emission limit for flue gas at outlet stream of thermal oxidizer. Thorough evaluation was carried out based on proposal submission from various technology providers and Vendors. The selection criteria was developed and established. For existing thermal oxidizers, the assessment is more complex taking into consideration the nature of brownfield project and to ensure the proposed modification has minor impact to operability and maintainability of existing facilities. This study has successfully enabled identification of feasible process technologies such as Caustic Scrubber, Seawater Flue Gas Desulfurization and Ammonia based Desulfurization to meet the desired emission limit at thermal oxidizer outlet for Oil and Gas Industry and supporting environmental protection. The selected technology is varies based on plant/project specific requirement. Among main considerations are the by-product management, consumable and utility consumption as well as compatibility of the technology with existing plant on shutdown requirement.

Mercury speciation and mass distribution of coal-fired power plants in Taiwan using different air pollution control processes

ABSTRACT In this study, the mercury (Hg) emission, speciation, and mass distribution of four coal-fired power plants (CFPPs) located at central, southern, and northern Taiwan with various types of air pollution control devices were investigated. Gaseous Hg in the coal-combustion flue gas was sampled by using the Ontario Hydro method, and the solid and liquid samples were collected for understanding the Hg mass balance. The experimental results showed that the total Hg concentrations in flue gases at the inlets of selective catalytic reduction (SCR) varied from 2.984 to 4.692 μg Nm−3, while the total Hg concentrations in the flue gases at the stacks ranged from 0.240 to 0.675 μg Nm−3. These four CFPPs showed similar Hg speciation results at the stacks. The average Hg removal efficiencies of Plants 1 (SCR + electrostatic precipitator [ESP] + wet flue gas desulfurization [WFGD]), 2 (SCR + ESP + WFGD), 3 (SCR + bag filter (BF) + seawater flue gas desulfurization [SWFGD]) and 4 (SCR + BF + SWFGD) were 92.4%, 90.1%, 85.9%, and 84.8%, respectively. Coal was the major raw material in Hg input of CFPPs with a mass flow rate ranging 5.87–12.05 g hr−1. Elemental Hg (Hg0), accounting for 66.4%−97.1% of the total Hg, was the dominant species emitted to the atmosphere. The Hg mass balances for the four CFPPs varied from 86.0% to 117% of the Hg input, suggesting that good mass balances were obtained from the tested CFPPs. Implications: Mercury emissions from coal-fired power plant (CFPPs) have been greatly concerned and should thus be better comprehended. The present study examined the mercury speciation and mass distribution of four CFPPs located at Taiwan. Overall, these CFPPs had similar Hg speciation results at stack and Hg0 was the dominant species emitted to the atmosphere. The selective catalytic reduction (SCR) + electrostatic precipitator (ESP) + wet flue gas desulfurization (WFGD) system had the highest Hg removal efficiency and the Hg mass balances for the four CFPPs varied from 86.0 to 117%. This study helps better understanding the Hg emission inventory of CFPPs and provides useful information for selecting adequate air pollution control devices (APCDs) for Hg control.

Advanced and Intensified Seawater Flue Gas Desulfurization Processes: Recent Developments and Improvements

Seawater flue gas desulfurization (SWFGD) is considered to be a viable solution for coastal and naval applications; however, this process has several drawbacks, including its corrosive absorbent; low vapor loading capacity since the solubility of sulfur oxides (SOx) in seawater is lower than that of limestone used in conventional methods; high seawater flowrate; and large equipment size. This has prompted process industries to search for possible advanced and intensified configurations to enhance the performance of SWFGD processes to attain a higher vapor loading capacity, lower seawater flowrate, and smaller equipment size. This paper presents an overview of new developments as well as advanced and intensified configurations of SWFGD processes via process modifications such as modification and optimization of operating conditions, improvement of spray and vapor distributors, adding internal columns, using square or rectangular shape, using a pre-scrubber, multiple scrubber feed; process integration such as combined treatment of SOx and other gases, and waste heat recovery; and process intensification such as the use of electrified sprays, swirling gas flow, and rotating packed beds. A summary of the industrial applications, engineering issues, environmental impacts, challenges, and perspectives on the research and development of advanced and intensified SWFGD processes is presented.

Simultaneous aqueous Hg(II) adsorption and gaseous Hg0 re-emission inhibition from SFGD wastewater by using Cu and S co-impregnated activated carbon

Seawater flue gas desulfurization (SFGD) has shown great effectiveness in the controlling of sulfur dioxide (SO2) emission and the removing of mercury (Hg) from flue gases of coal-fired power plants. Some problems pertaining to SFGD for Hg control, however, remain to be solved: (1) environmental impact from the discharge of Hg-containing seawater to the ocean, and (2) re-emission of gaseous Hg from the aeration tank to the atmosphere. This study synthesizes the copper/sulfur co-impregnated activated carbon (Cu–S-AC) to simultaneously capture aqueous Hg(II) and inhibit gaseous Hg0 re-emission from actual SFGD wastewater. Cu–S-AC exhibited greater Hg(II) adsorption than both raw activated carbon (AC) and sulfur-impregnated activated carbon (S-AC) at an initial Hg(II) concentration of higher than 8000 ng/L. The Hg(II) adsorption of Cu–S-AC was slightly greater at pH 7 and 8 than that under acidic conditions. The Hg(II) adsorption was well-fitted with both linear and Freundlich isotherms. The results of thermodynamic analyses veiled the endothermic and spontaneous adsorption of Hg(II) on Cu–S-AC. In addition, the pseudo-second-order equation provided the best correlation coefficient for the Hg(II) adsorption on Cu–S-AC. Notably, the increases of pH and temperature increased the Hg0 re-emission. Nevertheless, Cu–S-AC addition significantly inhibited the Hg0 re-emission (92%) from SFGD wastewater.

An aeration membrane absorption seawater flue gas desulfurization process intensified by combining dual-phase flow and oxidation reaction

Seawater flue gas desulfurization is an important method for controlling SO2 pollution. The membrane absorption, as a promising technology, attracted more and more interest in this field. A novel aeration membrane absorption seawater flue gas desulfurization process was proposed to improve the mass transfer by the physical and chemical effect. The flow rates of seawater and flue gas considerably influenced the absorption by improving the fluent turbulence near the membrane surface. The overall mass transfer coefficient (KG) of SO2 could be increased from 1.15–1.5 × 10−3 m/s without aeration to 1.35–1.85 × 10−3 m/s with 5 L/min aeration flowrate. Three kinds of gas with different Oxygen content (O2, N2, air) were investigated and compared. Both of the remove rate and KG with the aeration of O2 were larger than the value with the other two. The introduced gas bubbles could bring a synergistic effect of dual-phase flow and oxidation reaction on the mass transfer of SO2, which were also proved by the fluent simulation and oxidation experiments. The morphology and hydrophobicity of membrane after long-term running was tested, which showed a decrease in hydrophobicity. Treatment with the acid solution could improve the hydrophobicity to some extent.

Adsorption of aqueous Hg2+ and inhibition of Hg0 re-emission from actual seawater flue gas desulfurization wastewater by using sulfurized activated carbon and NaClO

The potential impacts of seawater flue gas desulfurization (SFGD) process used in coal-fired power plants have been greatly concerned because the wastewater containing Hg is directly discharged into the ocean environment without proper treatment. Furthermore, the re-emission of Hg as Hg0 to the atmosphere from SFGD wastewater caused by the reduction of aqueous Hg2+ has also been observed. This study investigated the dependence of Hg2+ adsorption behavior for sulfurized activated carbon (SAC) in actual SFGD wastewater on various influencing factors, including initial Hg2+ concentration, solution pH, contact time, temperature, and the addition of oxidant (sodium hypochlorite, NaClO). SAC exhibited greater Hg2+ adsorption than raw activated carbon at an initial Hg2+ concentration of more than 4,723 ng L−1. The Hg2+ removal efficiency of SAC was slightly larger at pH 7.0 and 8.0 than that at pH within 2.0–6.0. Hg2+ adsorption on SAC was well correlated with the linear adsorption model. Kinetic analysis results indicate that pseudo-second-order adsorption may serve as the rate-limiting reaction of Hg2+ adsorption on SAC. Thermodynamic analyses confirmed the endothermic and spontaneous adsorption behavior of Hg2+ on SAC in the seawater environment. Notably, the addition of NaClO significantly reduced the Hg2+ removal efficiency when SAC was used as the adsorbent. Nevertheless, NaClO addition also inhibited the reduction reaction of Hg2+ to Hg0 by forming strong HgCl complexes, which decreased the risk of Hg0 reemitted into the atmosphere via a SFGD system.

Increasing seawater alkalinity using fly ash to restore the pH and the effect of temperature on seawater flue gas desulfurization

Wet type flue gas desulfurization (FGD) using lime or limestone is popular because of its operational simplicity and the availability of lime and limestone. Seawater FGD (SWFGD) utilizes the alkalinity of seawater, and its efficiency varies depending on the seawater alkalinity. This study examined the effects of temperature, gas/water ratio, and total alkalinity of the absorbing solution on the removal efficiency of SO2 from flue gas by seawater. In addition, this study showed the possibility of increasing the total alkalinity of seawater using fly ash from coal power plants. The experimental results showed a 8% increase in removal efficiency, while temperature decreased by 10 °C from 25 °C under the conditions of a gas/water ratio of 100 and a resultant pH of 3. The increase in removal efficiency with increasing alkalinity was measured as 0.27%/ppm of bicarbonate alkalinity. This study showed that fly ash has the ability to increase the total alkalinity of seawater. The pH restoration experiment was conducted using fly ash and limestone. The conceptual design processes of SWFGD using NaOH, fly ash, and limestone for a 400 MW coal power plant were developed, and the material balance was calculated using ASPEN Plus software.

Feasibility Study on Application of Seawater Flue Gas Desulfurization (SWFGD) in Ultra-low Emission (ULE)

As an economical and energy-saving environmental protection technology, seawater desulfurization technology is widely used in environmental protection facilities of coal-fired power plants. With the introduction of the ULE management, the traditional seawater desulfurization technology can no longer meet the increasingly stringent environmental requirements. Based on the theory of gas-liquid mass transfer and nozzle atomization size distribution analysis, this paper investigates the effect and limitation of desulfurization performance enhancement by adding spray layer. The research results show that the design efficiency of the fifth layer spray is only 31.94%, and the export SO2 is only reduced to 98mg/m3. The concentration level is far from the ULE standard (35mg/m3), and the spray layer does not fully meet the requirements of ULE standards. Therefore, further considerations need to be taken from other ways of increasing efficiency.

Integrated electrochemical-aerating oxidation in recovery system of seawater flue gas desulfurization

In recovery system of seawater flue gas desulfurization (SWFGD) process, a novel integrated electrochemical-aerating oxidation method is developed. The influences of process factors such as anode-cathode brush assembly, applied current and dilution ratio on S(IV) oxidation performance are investigated, in connection with S(IV) oxidation rate, the anodic potential range of S(IV) oxidation, energy consumption and total amount of seawater. Compared with the conventional aerating process, the integrated oxidation is confirmed as an energy-efficient and seawater-saving improvement for existing SWFGD recovery system. Based on these experiment results, the reaction mechanism is also proposed. The electrochemical reactions on modified polyacrylonitrile-based carbon fiber (MPAN-CF) brush anode and polyacrylonitrile-based carbon fiber (PAN-CF) brush cathode, together with aerating process, synergistically accelerate the S(IV) oxidation. Therefore, integrated electrochemical-aerating oxidation method using MPAN-CF&PAN-CF anode–cathode brushes is promising for industrial application and is expected for the treatment of high sulfur flue gas in future.

Natural stable isotopic compositions of mercury in aerosols and wet precipitations around a coal-fired power plant in Xiamen, southeast China

In this study, samples of 18 wet precipitations (WPs) and 38 aerosols were collected around a coal-fired power plant (CFPP) located in Xiamen, southeast China, which was equipped with a seawater flue gas desulfurization system. Total particulate mercury (TPM) in aerosol samples, and total mercury (WP-TM), dissolved mercury (WP-DM) and particulate mercury (WP-PM) in WP samples were analyzed for the natural isotopic compositions of mercury. For the first time, both mass dependent fractionation (MDF) and mass independent fractionation of odd (odd-MIF) and even (even-MIF) isotopes of WP-DM and WP-PM were reported and discussed. Both WP-TM and TPM displayed negative MDF and slightly positive even-MIF. Negative odd-MIF was observed in TPM and WP-PM, whereas positive odd-MIF was observed in WP-TM and WP-DM. It was found that the mercury budget in WP-PM samples was mainly controlled by atmospheric particles. Potential sources of mercury in samples were identified via analysis of mercury isotopic signatures and meteorological data with the NOAA HYSPLIT model. The results showed that TPM and WP-PM in solid samples were homologous and the isotopic compositions of WP-TM depended on those of WP-DM. The ratios of Δ199Hg/Δ201Hg resulting from photochemical reactions and positive Δ200Hg values (from -0.06‰ to 0.27‰) in all samples indicated that the mercury coming from local emission of the CFPP together with long-distance transportation were the two main contributing sources.

Mass Flow Analysis of Mercury Transformation and Effect of Seawater Flue Gas Desulfurization on Mercury Removal in a Full-Scale Coal-Fired Power Plant

To understand the mercury speciation and mass flow in a full-scale bituminous coal-fired power plant equipped with a selective catalytic reduction (SCR) unit, an electrostatic precipitator (ESP), and a seawater flue gas desulfurization (SWFGD) scrubber, the evolution and emission of mercury was systematically measured and analyzed. The results showed that the elemental mercury (Hg0) was oxidized mainly through heterogeneous oxidation, especially in SCR, which transformed 57–64% of elemental mercury (Hg0) to oxidized mercury (Hg2+). It changed the concentrations of different mercury species and then increased the Hg2+ removal efficiencies of SWFGD, which ranged from 67 to 82%. A total of 8.24–11.54% of mercury was adsorbed by fly ash to form particulate-bound mercury (HgP) and subsequently removed by the ESP. Mass flow and mass distribution of mercury indicated that most mercury was removed and retained in the SWFGD. The heterogeneous oxidation of Hg0 in SCR and then absorption of Hg2+ by SWFGD significant...

Fractionation of mercury stable isotopes during coal combustion and seawater flue gas desulfurization

In the current study, fractionation of mercury isotopes during coal combustion and seawater flue gas desulfurization (SFGD) in a coal-fired power plant using a SFGD system was investigated. Fourteen samples were collected from the power plant. The samples were pretreated with a combustion-trapping method and were analyzed with a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS). Compared with the raw coal, the bottom ash was enriched with lighter mercury isotopes with δ202Hg values ranging from −0.45 to −0.03‰. The fly ash was enriched with lighter mercury isotopes with δ202Hg values ranging from −1.49 to −0.73‰ for Chinese coal and from −1.47 to −0.62‰ for Indonesian coal. The δ202Hg of fresh seawater and desulfurized seawater was found to be −1.32 and −0.32‰ respectively. These δ202Hg values indicated that the desulfurized seawater was enriched with heavier mercury isotopes. Based upon the calculated results obtained from the mass balance equation, it was suggested that the stack emissions were enriched with lighter mercury isotopes. Mass independent fractionation was observed in most of the samples with a Δ199Hg/Δ201Hg ratio of approximately 0.96. The results help in improving the understanding of mercury isotope fractionation during coal combustion and SFGD, and are also useful in tracing the mercury emissions from coal fired power plants.

Mercury isotope signatures of seawater discharged from a coal-fired power plant equipped with a seawater flue gas desulfurization system

Seawater flue gas desulfurization (SFGD) systems are commonly used to remove acidic SO2 from the flue gas with alkaline seawater in many coastal coal-fired power plants in China. However, large amount of mercury (Hg) originated from coal is also transferred into seawater during the desulfurization (De-SO2) process. This research investigated Hg isotopes in seawater discharged from a coastal plant equipped with a SFGD system for the first time. Suspended particles of inorganic minerals, carbon residuals and sulfides are enriched in heavy Hg isotopes during the De-SO2 process. δ202Hg of particulate mercury (PHg) gradually decreased from −0.30‰ to −1.53‰ in study sea area as the distance from the point of discharge increased. The results revealed that physical mixing of contaminated De-SO2 seawater and uncontaminated fresh seawater caused a change in isotopic composition of PHg isotopes in the discharging area; and suggested that both De-SO2 seawater and local background contributed to PHg. The impacted sea area predicted with isotopic tracing technique was much larger than that resulted from a simple comparison of pollutant concentration. It was the first attempt to apply mercury isotopic composition signatures with two-component mixing model to trace the mercury pollution and its influence in seawater. The results could be beneficial to the coal-fired plants with SFGD systems to assess and control Hg pollution in sea area.

Modified clinoptilolite catalysts for seawater flue gas desulfurization application: Preparation, characterization and kinetic evaluation

Seawater flue gas desulfurization (FGD) process has been adopted by a number of coastal power plants for its lower operation cost. Natural clinoptilolite (clin) was modified by Fe2+ ion exchange, drying, and calcination to prepare a catalytic packing for improving desulfurization efficiency of the adsorption tower. Compared with natural clin, the most active 350-Fe-clin (Fe2+ exchanged clin, calcined at 350°C) catalyst kept 6–12% higher SO2 removal efficiency at the operation temperature regime 45–85°C. The acidic effluent of the adsorption tower was below pH 3.0, and S(IV) oxidation efficiency was above 80%. This confirmed that the modified clin catalytic packing played a crucial role on seawater FGD process. Mechanistic and kinetic studies were carried out on the seawater SO2 removal over prepared catalytic packings. XRD, SEM and temperature programmed desorption (TPD) were employed to characterize the catalysts. Kinetic and TPD experiments showed that SO2 desorption energy on 350-Fe-clin was 19.85kJ/mol, apparent reaction activation energy of seawater FGD on 350-Fe-clin in the scrubber was 20.27kJ/mol, and liquid phase S(IV) oxidation rate constant in liquid phase was much higher than that of overall reaction. It could be deduced that the reaction rate determining step existed in gas phase reactions.

Understanding selected trace elements behavior in a coal-fired power plant in Malaysia for assessment of abatement technologies

The Proposed New Environmental Quality (Clean Air) Regulation 201X (Draft), which replaces the Malaysia Environmental Quality (Clean Air) 1978, specifies limits to additional pollutants from power generation using fossil fuel. The new pollutants include Hg, HCl, and HF with limits of 0.03, 100, and 15 mg/N-m3 at 6% O2, respectively. These pollutants are normally present in very small concentrations (known as trace elements [TEs]), and hence are often neglected in environmental air quality monitoring in Malaysia. Following the enactment of the new regulation, it is now imperative to understand the TEs behavior and to assess the capability of the existing abatement technologies to comply with the new emission limits. This paper presents the comparison of TEs behavior of the most volatile (Hg, Cl, F) and less volatile (As, Be, Cd, Cr, Ni, Se, Pb) elements in subbituminous and bituminous coal and coal combustion products (CCP) (i.e., fly ash and bottom ash) from separate firing of subbituminous and bituminous coal in a coal-fired power plant in Malaysia. The effect of air pollution control devices configuration in removal of TEs was also investigated to evaluate the effectiveness of abatement technologies used in the plant. This study showed that subbituminous and bituminous coals and their CCPs have different TEs behavior. It is speculated that ash content could be a factor for such diverse behavior. In addition, the type of coal and the concentrations of TEs in feed coal were to some extent influenced by the emission of TEs in flue gas. The electrostatic precipitator (ESP) and seawater flue gas desulfurization (FGD) used in the studied coal-fired power plant were found effective in removing TEs in particulate and vapor form, respectively, as well as complying with the new specified emission limits.Implications:Coals used by power plants in Peninsular Malaysia come from the same supplier (Tenaga Nasional Berhad Fuel Services), which is a subsidiary of the Malaysia electricity provider (Tenaga Nasional Berhad). Therefore, this study on trace elements behavior in a coal-fired power plant in Malaysia could represent emission from other plants in Peninsular Malaysia. By adhering to the current coal specifications and installation of electrostatic precipitator (ESP) and flue gas desulfurization, the plants could comply with the limits specified in the Malaysian Department of Environment (DOE) Scheduled Waste Guideline for bottom ash and fly ash and the Proposed New Environmental Quality (Clean Air) Regulation 201X (Draft).

Minimization of SO2 Emissions at ADGAS (Das Island, UAE): II- Impact on Air Quality

In Part I of this work, two SO2 minimization schemes, namely, Fuel Gas Sweetening (FGS) and Seawater-Flue Gas Desulfurization (SW-FGD) schemes have been proposed to be implemented at the ADGAS plant (Das Island, UAE). The implementation of such schemes is expected to reduce the SO2 emissions by 77%. The FGS scheme is expected to reduce the H2S content in the fuel gas system by 94% and results in decreasing the total SO2 emissions due to fuel gas usage by 98%. The SW-FGD scheme is expected to reduce the SO2 emissions due to incomplete sulfur recovery by 99.5%. This work is based on on-site measurements and data collected from specific locations at the ADGAS plant and over the Das Island, UAE. These data were loaded into air dispersion model software (AERMOD 7, 2008) and simulated to predict future air quality on the Island. The SO2 Ground Level Concentrations (GLCs) were predicted for the current conditions and for the proposed SO2 minimization schemes (presented in Part I of this work) using the BREEZE AERMOD Pro software model. Upon implementing the proposed SO2 minimization schemes, the predicted GLCs were found to comply with the United Arab Emirates Federal Environment Agency (UAE-FEA) standard limits at all sites in the ADGAS plant and over the Island. Also the remaining SO2 emissions have the potential to challenge any future stringent limits set by the UAE-FEA with a high level of confidence since the emission rates after implementing the proposed SO2 minimization schemes will be reduced to about 5% of the current standard emission limit (25 mg/Nm3). Lastly, the general approach presented in this work may be of value in application to other similar systems worldwide.

Oxidation of S(IV) in Seawater by Pulsed High Voltage Discharge Plasma with TiO2/Ti Electrode as Catalyst

Oxidation of S(IV) to S(VI) in the effluent of a flue gas desulfurization(FGD) system is very critical for industrial applications of seawater FGD. This paper reports a pulsed corona discharge oxidation process combined with a TiO2 photocatalyst to convert S(IV) to S(VI) in artificial seawater. Experimental results show that the oxidation of S(IV) in artificial seawater is enhanced in the pulsed discharge plasma process through the application of TiO2 coating electrodes. The oxidation rate of S(IV) using Ti metal as a ground electrode is about 2.0×10−4 mol · L−1 · min−1, the oxidation rate using TiO2/Ti electrode prepared by annealing at 500°C in air is 4.5×10−4 mol · L−1 · min−1, an increase with a factor 2.25. The annealing temperature for preparing TiO2/Ti electrode has a strong effect on the oxidation of S(IV) in artificial seawater. The results of in-situ emission spectroscopic analysis show that chemically active species (i.e. hydroxyl radicals and oxygen radicals) are produced in the pulsed discharge plasma process. Compared with the traditional air oxidation process and the sole plasma-induced oxidation process, the combined application of TiO2 photocatalysts and a pulsed high-voltage electrical discharge process is useful in enhancing the energy and conversion efficiency of S(IV) for the seawater FGD system.