In USA, the EPA announced in 2000 the need to regulate Hg emissions fromcoal-fired electric-generating units under the 1970 Clean Air Act (CAA). At that time, a dedicated effort was already underway in both the USA and Canada to better understand the fate and formation of Hg, including native capture in existing coal-firedpower plants, most of which are pulverized coal-fired units. The world’s first Hg control regulation was released by the EPA on 18 March 2005: the Clean AirMercury Rule (CAMR) [US EPA, 2005a]. A sister rule promulgated just prior to the CAMR, the Clean Air Interstate Rule, was crafted concurrently to provide early multi-pollutant control of Hg by controlling SO x , NO x and PM [US EPA, 2005b]. Despite earlier expectations that the EPA would release a rule that called for maximum achievable control technology (MACT) standards, the CAMR called for a cap- and-trade approach. After significant input from both the private and public sectors, a lawsuit was brought against the EPA. The recent outcome of that suit is that the District Court of Appeals revoked the CAMR on 8 February 2008, leaving the EPA with instruction to draft a new regulation, which means that utilities in the United States will soon be required to comply with MACT standards.
Exposure to air pollution affects early childhood development. Heavy metal and ultrafine particulates are able to cross the placental barrier and have the potential to harm the foetus and its developing organs (Wick et al. 2010). There is strong evidence that ozone and SO 2 are associated with premature birth, with weaker evidence for particulates (Ha et al. 2014). Exposure to particulates, and perhaps also to ozone, NO 2 and carbon monoxide (CO) during pregnancy may affect foetal growth and increases the risk of low birth-weight (Glinianaia et al. 2004; WHO 2013). The concern with premature birth and low birth- weight is that they have an impact on the developing organs. Heavy metals, like lead and mercury, have been associated with neurodevelopmental harm, leading to reduced cognitive function, lower intelligence quotient (IQ), attention deficit hyperactivity disorder and possibly autism spectrum disorder during childhood (Canfield et al. 2003; Liu and Lewis 2014. Young children are particularly vulnerable to the effects of air pollution. After birth, the organs are still maturing and infants have a relatively high metabolic rate so they breathe a greater volume of air than adults, relative to their size (RCP 2016). Early- life exposure to air pollution is also thought to cause epigenetic modification through changes in DNA methylation (Janssen et al. 2013; Jiang et al. 2014).
It is evident that the models differ in their completeness of substances coverage, the sophistication regarding air pollution chemistry and degree of resolution of meteorological conditions, their degree of source-region resolution and their degree of receptor grid and receptor characteristics resolution, and finally, in the degree of complete coverage of the whole global area as source and receptor region. For the purpose of regional assessment of primary and secondary air pollutants therefore, the EMEP_EU_SRM is quite appropriate. The EMEP_EU_SR model for Europe distinguishes between release height, smaller sub-regions within Europe, different background emission scenarios and meteorological years. In the following, the EMEP_EU_SR for Europe will be described.
In each reception bin the course ash settles to the bottom while the finest particles are conveyed by the transport air directly to the combustion chamber. Bottom ash is extracted from the reception bins by tubular vibro-feeders, and discharged directly in the coal mill feeding hoppers. A single reception bin serves 2 coal mills, therefore it is necessary to install two vibro-feeders for each reception bin. Each Reception Bin is provided with a bursting disc for pressure relief and 4 level probes for control purposes.
In this report, methods and results of estimating the most important health risks caused by emissions of air pollutants fromcoalfiredpower plants in Germany are described. Based on data about emissions of air pollutants fromcoalfiredpower plants provided by GREENPEACE (Myllyvirta 2013), the resulting health risks are estimated. The air pollutants causing by far the highest health risks and thus considered in this analysis are primary fine dust PM10, PM2.5, SO 2 , NO x , and NMVOC. The latter species SO 2 , NO x and NMVOC are transformed in the atmosphere into secondary inorganic aerosols and ozone. The method used to estimate the health risks, i.e. the impact pathway approach, has been developed by IER in cooperation with other European partners during a series of projects (the ExternE projects) funded by the European Union (European Commission 2005), ( www.ExternE.info ), (Markandya and Wilkinson 2007), (Friedrich and Preiss 2012). This method is widely applied by the European Commission for carrying out integrated assessments for supporting environmental legislation and for transport project appraisal.
Employers are required to report occupational hygiene data of exposed employees, and exposure levels. The information reported by the power utility company is standardised and it includes the site (power station name, which has been coded to the purpose of this study) and number of employees potentially exposed to respirable dust; worker’s personal data and job type; date of measurement and level of exposure. The power station Occupational Hygiene and Safety department is responsible for the measurement procedures and air sampling methods in accordance with NIOSH method 7500, which provide technical guidance to implement a dust monitoring strategy. The workers are stratified into homogeneous exposure groups (HEG) and are randomly selected per cycle of measure using a prescribed selection method as per the Occupational Exposure Sampling Strategy Manual (OESSM). The total respirable coal dust samples were analysed using gravimetric analysis and silica quartz samples were analysed using X-ray diffraction (XRD, method 7500) at a laboratory accredited by the South African National Standards.
Mercury is a persistent and toxic substance that can be bio-accumulated in the food chain. Natural and anthropogenic sources con- tribute to the mercury emitted in the atmosphere. Eskom’s coal-firedpowerstations in South Africa contributed just under 93% of the total electricity produced in 2015 (Eskom 2016). Trace amounts of mercury can be found in coal, mostly combined with sulphur, and can be released into the atmosphere upon combustion. Coal-fired electricity generation plants are the highest contributors to mer- cury emissions in South Africa. A major factor affecting the amount of mercury emitted into the atmosphere is the type and efficiency of emission abatement equipment at a power station. Eskom employs particulate emission control technology at all its coal-firedpowerstations, and new powerstations will also have sulphur dioxide abatement technology. A co-beneficial reduction of mercury emissions exists as a result of emission control technology. The amount of mercury emitted from each of Eskom’s coal-firedpowerstations is calculated, based on the amount of coal burnt and the mercury content in the coal. Emission Reduction Factors (ERF’s) from two sources are taken into consideration to reflect the co-benefit received from the emission control technologies at the stations. Between 17 and 23 tons of mercury is calculated to have been emitted from Eskom’s coal-firedpowerstations in 2015. On completion of Eskom’s emission reduction plan, which includes fabric filter plant retrofits at two and a half stations and a flue gas desulphurisa- tion retrofit at one power station, total mercury emissions from the fleet will potentially be reduced by 6-13% by 2026 relative to the baseline. Mercury emission reduction is perhaps currently not the most pressing air quality problem in South Africa. While the focus should then be on reducing emissions of other pollutants which have a greater impact on human health, mercury emission reduction can be achieved as a co-benefit of installing other emission abatement technologies. At the very least, more accurate calculations of mercury emissions per power station should be obtained by measuring the mercury content of more recent coal samples, and developing power station-specific ERF’s before mercury emission regulations are established or an investment into targeted mercury emission reduction technology is made.
In the expanded area (behind the main sample line) the air temperature (T ), static pressure (p), and relative humidity (rH) are measured. To avoid adsorption losses of sticky trace gases, the internal surface of the inlet system was coated with Teflon and only PFA tubing was used for the sampling lines. The outside of the inlet was coated with copper to avoid elec- trostatic charging. The inlet was fastened onto a 90 cm long telescope tube (6 cm diameter), which was mounted in a hole on the floor fuselage via a sliding guide. After takeoff, the tube was pushed down by ∼ 40 cm from inside the aircraft, to ensure that the inlet nozzle was outside the aircraft boundary layer. Before landing the tube was pulled back into the air- craft to protect it from damage by objects whirled up by the front wheel. The inlet and the telescope tube were equipped with heaters to prevent icing, but during the ETMEP mea- surements the heating was always switched off because the measurement flights were carried out in summer at altitudes below 3000 m a.s.l. The tubing from the inlet to instruments ( ∼ 2.5 m long 3/8” O.D. main sample tube with PFA mani- folds to instruments) was not heated. The temperature inside the cabin was 18 to 30 ◦ C.
pollutants. aerMOd has been promulgated by ePa as a preferred air dispersion model to replace the iScSt3. dispersion modeling was conducted by both aerMOd and iScSt3 model systems, and the results were compared in this study. The features of stack flue gases and mercury emission rates of those power plants were obtained from the netl’s 2007 coalPower Plant database and ePa’s toxics release inventory (tri) database (http://www. epa.gov/triexplorer), respectively, and summarized in table 1. in addition, aerMOd and iScSt3 model parameters are summarized in table 2. Meteorological data were obtained from the meteorological resource center (http://www.webmet.com). due to limitations on availability, 1990 meteorological data were used for both aerMOd and iScSt3 modeling. considering proximity to each coal-firedpower plant, columbus meteorological data were applied to the conesville coal-firedpower plant, and dayton meteorological data were applied to the JM Stuart coal-firedpower plant. as found in the ePa report to congress (rice and others 1997), the mercury species in all the stack flue gases were assumed to consist of 58% hg 0 , 40% hg 2+ , and 2% hg p . The atmospheric
During the energy crisis period, energy demand was met by means of delaying maintenance on the generation fleet. This led to the decline in perform- ance of the fleet, which in turn, negatively impact- ed the effectiveness of the fleet to meet future demand (Integrated Resource Plan for Electricity (IRP), 2013). Three older powerstations that were mothballed during the 1980’s and early 1990 were returned back to service to alleviate the pressure on existing stations. It is believed that the energy demand/supply balance will remain vulnerable until Medupi and Kusile, two new powerstations cur- rently under construction, come fully online expect- edly between 2018 and 2020 (Eskom, personal communication), although uncertainty still remains on the exact commissioning dates. In 2010 the South African Department of Environmental Affairs (DEA) promulgated a set of Minimum Emission Standards (MES) for criteria pollutants that will come into effect in 2015 and 2020, and is expected to decrease emissions (Department of Environmental Affairs (DEA), 2010a). However, a number of industries, including Eskom and Sasol, the two major role players in the combustion of coal in South Africa have filed applications for the post- ponement of, and in some cases, exemption from the MES (Iliso Consulting, 2013; SRK Consulting, 2013). The reasons for this are the high cost of com- pliance with the MES (with a capital cost of around 6% of the South African nominal Gross Domestic Product (GDP) for 2013) (Eskom, personal com- munication, 2014; Statistics South Africa, 2014), and the inflexibility of the MES by not taking the ambient air quality and exposed population sur- rounding powerstations into account. This means that stations are expected to comply with the MES even if the national ambient air quality standards are met before compliance. It is further envisaged that a Carbon tax as an instrument to encourage carbon mitigation will come into effect in 2016 (Greve, 2013).
due to ambiguities in the estimation methodologies employed to evaluate mobile sources. The main sources of mercury emissions to atmosphere in Japan are coal–fired cement plants, accounting for over 30% of the total emissions in the year 2006. On the other hand, industrial emissions from primary ferrous metal production and coal–firedpower plants had a significant contribution of atmospheric mercury emissions in Japan in 2006. The assessment of mercury concentrations in the local atmosphere in Japan was performed using two different atmospheric dispersion models, i.e., the AIST–ADMER and the METI–LIS. The results of the present study indicated that the annual mean ambient concentrations of mercury in residential areas generally amounted to be less than 0.22 ng/m 3 (0.00022 μg/m 3 ), but there are no sites that exceed 0.04 μg/m 3 near industrial point sources. Though it is unrealistic to expect the Gaussian models to predict the real situation of mercury concentration in the local atmosphere, the major purposes of the present assessment was to conduct a methodology of comprehensive analysis of exposure and atmospheric distribution of mercury concentration, and thereby to develop a detailed picture of current air quality assessment of the different industrial areas of Japan.
Mercury is a toxic heavy metal, with a complicated biogeochemical cycle due to its various species. Mercury emissions to the atmosphere come mainly from anthropogenic activities, and among them, coal combustion is considered to be the dominant contributor. Seawater flue gas desulfurization (SFGD) system has been widely adopted in coal-firedpower plants (CFPPs) of China coastal region. Defferent from other flue gas desulfurization techniques, where the influence of CFPPs on surrounding atmosphere is only dominated by stack emission, the mercury transfer from post-desulfurization seawater of a SFGD system to air should not be ignored. Therefore, it is meaningful to study the influence of mercury discharged from CFPPs equipped with SFGD system on surrounding atmosphere.
Fuel reduction has been achieved for coalpowerstations by hybridisation with solar thermal systems. Current technology uses feedwater or turbine bleed steam (TBS) heating with linear Fresnel based concentrated solar power (CSP) fields. The low temperature heat produced by these systems results in low solar to power conversion efficiency and very low annual solar shares. In this paper the technical advantages of solarising coalfiredpower plants using preheated air by a novel CSP system based on a solid particle receiver (SPR) are examined. This system is compared to the current deployed state- of-the-art coal plant solarisation by modelling the systems and analysing the thermodynamic heat and mass balance of the steam cycle and coal boiler using EBSILON®Professional software. Annual performance simulation tools are also used to calculate the performance of the solarisation technologies. Solarisation using SPR technology for preheating air in solar-coal hybrid powerstations has the potential to considerably increase the solar share of the energy input by 28% points at design point and improve the annual fuel reduction from 0.7% fuel saved to 20% over the year. This is a significant reduction in fossil fuel requirements and resulting emissions. These benefits are a result of SPR solar system’s higher operating temperature and integrated thermal storage, which also allow a buffered response time for handling transients in the intermittent solar resource.
Halogen in coal can be a key factor influencing Hg speci- ation. We collected data from over twenty onsite tests and analyzed the effect of chlorine content in coal on mercuryspeciation in the flue gas released from the boilers, as shown in Fig. 4a. We found that, with three sample points excluded, the correlation coefficient reached 0.75, indicating that chlo- rine content of coal may have significant effect on distribu- tion of different mercury species. This is in line with previ- ous studies (Yang et al., 2007; Chen et al., 2007). The follow reactions show the mechanism of mercury changing from el- emental form to oxidized form with the presence of halogens (Cl and Br). In the reactions, M stands for metal and X stands for halogen.
Mercury can also be returned to the rivers as part of sediments, and high concentrations of mercury in sediment can be found near sources of mining. If the mercury compound is soluble the mobility of the mercury in the environment is greater, although cases of enhanced solubility are also of concern. During rainy seasons, when the water flow is rapid and turbid, and the solids load is high, the lateral and downstream transport of mercury is more favourable due to the amount of suspended material (VanLoon and Duffy, 2005). In the sediments at the surface, oxidation of mercury occurs forming a soluble mercury (II) chloro species that can be accumulated in the plants growing in nutrient rich waters. According to VanLoon and Duffy (2005) and Cheng et al. (2009) fish can take up methylated mercury when sediments contain organic matter and, as mentioned in the previous section, is the major species of mercury found in fish (Cheng et al., 2009; VanLoon and Duffy, 2005). Mercury is observed in plants, also an important component of human diet, in areas exposed to sources of mercury. In Massachusetts, humans are warned to avoid consuming the local fish as a result of the unsafe mercury levels. It is suspected that the primary source of mercury contamination to these water bodies is due to atmospheric mercury deposition from long range transport and near field point sources as a result of anthropogenic or natural sources (Hutcheson et al., 2008).
At the Power Plant Air Pollutant Control “Mega” Symposium in 2008 several new methods have been presented for the reduction of mercury emissions up to removal efficiency of 90%. Activated Coal Injection (ACI) upstream of the ESP/FF increases the Hg(P) portion that can be removed by the ESP/FF from the flue gas. When brominated active coal is injected the Hg(2+) portion also increases which improves the performance of the FGD for the removal of mercury (ref 4). The use of activated coal as adsorbent will reduce the emission of mercury to levels in the range of microgram/Nm 3 . For the Toxecon process, based on injection of activated carbon, emission levels were established in the range of 0.5 to 3 microgram/ Nm 3 (Ref. 17).
per capita coal capacity could serve as a better estimate of externality then pollutant composition measurements. Those pollutants such as SOx, NOx, heavy metal are asso- ciated with lung cancer from previous studies . Thirdly, although capacity factors varied among countries, the range of capacity was approximately 40–60% ; this indicates that the quantity of coal combustion remained fixed after a plant was built. Finally, coal prices in a local market reflect coal quality. Although coal quality might vary between countries, it remains constant within a plant across time . Country-specific effects, such as coal quality, are marginalized out by GEE in the analysis. By weighting the model by country population, we are reflect- ing the individual data by exploiting aggregated mean values of per capita coal capacity for each individual.
and compression installation so that the integration carried out later should bring economic profits. Such effi- ciency values can only be achieved by optimum technological structures if the best available technologies (BATs) are applied in the field of power engineering machinery and equipment. The paper presents the impact of the efficiency of individual elements of the power unit machinery and equipment on the plant overall effi- ciency. It can be seen that giving values of the power unit electricity generation efficiency without specifying the efficiencies of the unit main components is burdened with a considerable margin of uncertainty which may even be as high as several percentage points.
9 surface of the furnace walls. On the other hand, deposits build-up that occurred in the convection pass after the combustible gasses exits the furnace are known as fouling. These accumulated deposits are usually formed at the leading edges of the superheater and re-heater tubes. Although they are easily dislodged using soot blowers, the ash particles blown by the soot blowers may result into the flue gas stream and create cinders which can plug air heater baskets and block selective catalytic reduction catalyst flow paths or bridge across the boiler tube in the convection pass . The most common sections of the boiler affected by slagging and fouling are from the burner belt to the furnace exit. Typically, boiler slagging and fouling are caused by low furnace excess oxygen, extreme stratifications of the Furnace Exit Gas Temperature (FEGT), high primary airflows, burner damage and deficient mechanical condition or tolerances, poor coal pulverizer performance and inconsistent fuel properties and chemistry. These slagging and fouling occurrences, when left untreated eventually result in a significant increase of the flue gas temperature that reduces the system overall efficiency and leading to an increase in corrosion problems in boilers .
As shown in the table, the total plant investment of reference system (230.52 M$) are estimated according to the related data of typical 350 MW coal-firedpower plants in China with specific plant investment of ap- proximately 700 $/kW. The total investment of CO 2 cap-