Mercury emission trend influenced by stringent air pollutants regulation for coal-fired power plants in Korea

Regulatory control of mercury emission from anthropogenic sources has become a global concern in the recent past. Coal-fired power plants are one of the largest sources of anthropogenic mercury emission into the atmosphere. This paper summarizes the current reducing trend of mercury emission as co-beneficial effect by more stringent regulation changes to control primary air pollutants with introducing test results from the commercial coal-fired facilities and suggesting a guideline for future regulatory development in Korea. On average, mercury emission concentrations ranged 16.3–2.7 μg Sm^?3, 2.4–1.1 μg Sm^?3, 3.1–0.7 μg Sm^?3 from anthracite coal-fired power plants equipped with electrostatic precipitator (ESP), bituminous coal-fired power plants with ESP + flue gas desulphurization (FGD) and bituminous coal-fired power plants with selective catalytic reactor (SCR) + cold side (CS) ? ESP + wet FGD, respectively. Among the existing air pollution control devices, the best configuration for mercury removal in coal-fired power plants was SCR + CS ? ESP + wet FGD, which were installed due to the stringent regulation changes to control primary air pollutants emission such as SO₂, NOx and dust. It was estimated that uncontrolled and controlled mercury emission from coal-fired power plants as 10.3 ton yr^?1 and 3.2 ton yr^?1 respectively. After the installation of ESP, FGD and SCR system, following the enforcement of the stringent regulation, 7.1 ton yr^?1 of mercury emission has been reduced (nearly 69%) from coal-fired power plants as a co-benefit control. Based on the overall study, a sample guideline including emission limits were suggested which will be applied to develop a countermeasure for controlling mercury emission from coal-fired power plants.     

Characteristics of gas and residues produced from electric arc pyrolysis of waste lubricating oil

An attempted has been made to recover high-calorific fuel gas and useful carbonaceous residue by the electric arc pyrolysis of waste lubricating oil. The characteristics of gas and residues produced from electric arc pyrolysis of waste lubricating oil were investigated in this study. The produced gas was mainly composed of hydrogen (35–40%), acetylene (13–20%), ethylene (3–4%) and other hydrocarbons, whereas the concentration of CO was very low. Calorific values of gas ranged from 11,000 to 13,000 kcal kg^?1 and the concentrations of toxic gases, such as NO_x, HCl and HF, were below the regulatory emissions limit. Gas chromatography–mass spectrometry (GC/MS) analysis of liquid-phase residues showed that high molecular-weight hydrocarbons in waste lubricating oil were pyrolyzed into low molecular-weight hydrocarbons and hydrogen. Dehydrogenation was found to be the main pyrolysis mechanism due to the high reaction temperature induced by electric arc. The average particle size of soot as carbonaceous residue was about 10 μm. The carbon content and heavy metals in soot were above 60% and below 0.01 ppm, respectively. The utilization of soot as industrial material resources such as carbon black seems to be feasible after refining and grinding.     

Eutectic mixture promoted CO2 sorption on MgO-TiO2 composite at elevated temperature

The development of carbon dioxide(CO_2) sorbents that can operate at elevated temperatures is significant for the advancement of pre-combustion capture technologies.Recently, promoter-based systems composed of alkali/alkaline earth metal nitrates and/or carbonates have been considered as next-generation solid sorbents due to their improved CO_2 uptake and kinetics. However, obtaining stable MgO sorbents against temperature swing regeneration still remained challenging. Herein, we report MgO-TiO_2 solid sorbents promoted by eutectic mixture(KNO_3 and LiNO_3) for elevated temperature CO_2 sorption. The developed sorbents show improved CO_2 sorption capacity, which may be attributed to the alternative CO_2 sorption pathway provided by the ionization of highly dispersed MgO in the eutectic mixture. The MgO-TiO_2 framework was also shown to assist in retaining the MgO configuration by constraining its interaction with CO_2. Furthermore, it is demonstrated that constructing composite structures is essential to improve the CO_2 sorption characteristics,mainly recyclability, at elevated temperatures. The developed promoter integrated sorbents showed exceptionally high CO_2 sorption capacity of 30 wt.% at an elevated temperature(300°C) with pronounced stability under temperature swing operation.     

Effect of vermiculite addition on compost produced from Korean food wastes

To evaluate the effect of vermiculite addition on composting food wastes from Korean households, food wastes were composted in three small bins to which different additives were added. The following three bins were employed: in Case I, only recycled compost was composted; in Case II, food wastes with recycled compost; and in Case III, food wastes with recycled compost and vermiculite. In the experiment performed for 30 days, it was confirmed that the supplementary addition of vermiculite to the composting mixture did not significantly improve the weight loss rate and the decomposition rate of food wastes. Due to dilution through the use of inorganic vermiculite, the vermiculite addition reduced the organic matter concentration of the composting mixtures. Vermiculite addition did not raise the pH value. Weight losses of roughly 70% were observed based on calculating moisture loss as well as dry food waste loss and not considering additives, while dry food waste loss was 29.4% and 35.8% with and without the addition of vermiculite, respectively. For these experiments, the major portion of the weight loss was the loss of water. The results indicate a need to differentiate between weight loss percentages and decomposition percentages, and a need to indicate if either of these percentages includes or excludes the mass of additives.     

The removal of heavy metals in urban runoff by sorption on mulch

A series of adsorption experiments was conducted in order to assess the ability of three mulches to remove several of the heavy metal ions typically encountered in urban runoff. Three types of mulch, cypress bark (C), hardwood bark (H), and pine bark nugget (P), were selected as potential sorbents to capture heavy metals in urban runoff. The hardwood bark (H) mulch had the best physicochemical properties for adsorption of heavy metal ions. In addition, because of its fast removal rate and acceptably high capacity for all the heavy metal ions, it was concluded that the H mulch is the best of the three adsorbents for treatment of urban runoff containing trace amounts of heavy metals. In order to investigate the sorption isotherm, two equilibrium models, the Freundlich and Langmuir isotherms, were analyzed. The sorption of these metals on H mulch conformed to the linear form of the Langmuir adsorption equation. At pH 5 and 6, the Langmuir constants (S(m)) for each metal were found to be 0.324 and 0.359 mmol/g (Cu); 0.306 and 0.350 mmol/g (Pb); and 0.185 and 0.187 mmol/g (Zn) at 25 degrees C.     

Ecological modeling for water quality management of Kwangyang Bay, Korea

This study estimated the appropriate pollutant load reduction from point sources in Kwangyang Bay, Korea, using an eco-hydrodynamic model. The total chemical oxygen demand (COD), nitrogen (TN), and phosphorus (TP) loads from rivers and ditches that provide input to the bay were approximately 2.8x10(4), 2.5x10(4), and 5.9x10(2) kg day-1, respectively. Wastewater discharge from industrial complexes was the greatest contributor to pollutant loads in the inner part of the bay. COD values in the inner part of the bay were greater than 3.0 mg l-1, and exceeded Korean seawater quality grade III limits. A residual current was simulated, using a hydrodynamic model, to have a slightly complicated pattern in the inner part of the bay, ranging from 0.001 to 8 cm s-1. In the outer part of the bay, the simulated current flowed out to the South Sea with a southward flow at a maximum of 15 cm s-1. The results of the ecological model simulation of COD levels showed high concentrations, exceeding 4 mg l-1, in the southwest of the Myodo, an area of wastewater discharge, and lower levels, approaching less than 1 mg l-1, closer to the outer part of the bay. Engineering countermeasures to reduce the organic and inorganic material loads from point sources by more than 45% were required to keep the COD levels below 2 mg l-1.     

ENVIRONMENTAL AUDITING: Economic Values of Recreational Power Boating Resources in Pennsylvania

/ The travel cost method was used to estimate the economic value of seven major power boating resources in Pennsylvania. A significant relationship between number of visitor trips and cost per visitor trip existed for five of the seven water bodies. The annual total value for those five resources was $396 million, which was 2.5 times greater than the total out-of-pocket expenditures of approximately $157 million visitors spent to visit them. Research results can help resource managers plan and craft programs and policies that are founded on economic values of the natural resources involved.     

Determination of low (137)Cs concentration in seawater using ammonium 12-molybdophosphate adsorption and chemical separation method

A new method has been developed for analyzing (137)Cs in a small volume of seawater. Ammonium 12-molybdophosphate (AMP) was used two times during pretreatment procedure. The first step was to adsorb (137)Cs in seawater samples into AMP in order to reduce sample volume, and the second was to remove (87)Rb, interference nuclide for beta counting. The AMP adsorbing (137)Cs was dissolved by sodium hydroxide solution, and then (137)Cs was finally formed to be cesium chloroplatinate precipitate by adding 10% hexachloroplatinic acid. The beta rays emitted from (137)Cs were measured with a low background gas-proportional alpha/beta counter. This method was applied to several seawater samples taken in the East Sea of Korea. Compared to the routinely used gamma-spectrometry method, this new AMP method was reliable and suitable for analyzing (137)Cs in deep seawater.     

Removal characteristics of CO2 using aqueous MEA/AMP solutions in the absorption and regeneration process

The carbon dioxide (CO2) removal efficiency, reaction rate, and CO2 loading into aqueous blended monoethanolamine (MEA) + 2-amino-2-methyl-1-propanol (AMP) solutions to enhance absorption characteristics of MEA and AMP were carried out by the absorption/regeneration process. As a result, compared to aqueous MEA and AMP solutions, aqueous blended MEA+AMP solutions have a higher CO2 loading than MEA and a higher reaction rate than AMP. The CO2 loading of rich amine of aqueous 18 wt.% MEA+12 wt.% AMP solution was 0.62 mol CO2/mol amine, which is 51.2% more than 30 wt.% MEA (0.41 mol CO2/mol amine). Consequently, blending MEA and AMP could be an effective way to design cousidering economical efficiency and used to operate absorber for a long time.     

Thermoeconomic installation limit of PV/WT hybrid energy systems for Off-grid islands

An ideal off-grid island can become 100% energy-sufficient if one installs renewable energy systems such as solar photovoltaic (PV) and wind turbine (WT) systems. However, the intermittent and uncertain nature of the power supply from renewable energy systems hinders a 100% autonomy level (AL) without an infinite energy storage capacity. The thermoeconomic installation limit (TEIL) of a PV/WT hybrid energy system was studied using hourly weather data and the energy demand profile for off-grid islands. An appropriate battery size for the TEIL was also determined. Given the current installation cost of the hybrid energy system and the battery unit, the AL for a PV/WT hybrid energy system at the TEIL is calculated to be approximately 70%. Above the limit, the size of the energy storage unit and, correspondingly, the total annual cost of the PV/WT hybrid energy system increase sharply.