Air Toxics Standards Research Articles

Laboratory testing of a continuous emissions monitor for hydrochloric acid

Continuous monitoring of exhaust flue gas has become a common practice in power plants in response to Federal Mercury and Air Toxics Standards (MATS) standards. Under the current rules, hydrochloric acid (HCl) is not continuously measured at most plants; however, MATS standards have been proposed for HCl, and tunable diode laser (TDL) absorption spectroscopy is one method that can be used to measure HCl continuously. The focus of this work is on the evaluation and verification of the operation performance of an HCL TDL over a range of real-world operating environments. The testing was conducted at the University of California at Riverside (UCR) spectroscopy evaluation laboratory. Laboratory tests were conducted at three separate temperatures, 25ºC, 100ºC, and 200ºC, and two distinct moisture levels for the enhanced temperatures, 0%, (2 tests) and 4%, over a concentration range from 0 ppmv to 25 ppmv-m at each of the elevated temperatures. The results showed good instrument accuracy as a function of changing temperature and moisture. Data analysis showed that the average percentage difference between the ammonia concentration and the calibration source was 3.33% for varying moisture from 0% to 4% and 2.69% for varying temperature from 25 to 100/200ºC. An HCl absorption line of 1.742 μm was selected for by the manufacturer for this instrument. The Hi Tran database indicated that CO2 is probably the only major interferent, although the CO2 absorption is very weak at that wavelength. Interference tests for NO, CO, SO2, NH3, and CO2 for a range of concentrations typical of flue gasses in coal-fired power plants did not show any interference with TDL HCl measurements at 1.742 μm. For these interference tests, CO2 was tested at a concentration of 11.9% concentration in N2 for these tests. Average precision over the entire range for all 10 tests is 3.12%.Implications: The focus of this study was an evaluation of the operation performance of a tunable diode laser (TDL) for the measurement of hydrochloric acid (HCl) over a range of real-world operating environments. The results showed good instrument accuracy as a function of changing temperature from 25ºC to 200ºC and moisture from 0% to 4%. Such as an instrument could be used for continuous monitoring of exhaust flue gas in power plants once the Federal Mercury and Air Toxics Standards (MATS) standards have been fully implemented.

Evaluation of Palladium-Based Sorbents for Trace Mercury Removal in Electricity Generation

The development of warm-gas cleanup (WGCU) systems for synthesis gas (syngas) cleanup in in- tegrated gasification combined cycle (IGCC) power plants has the potential to lower the costs of generating power. WGCU includes the removal of mercury (Hg), present in coal, from the syngas. Carbon-based sorbents used for Hg removal are not suitable for high-temperature Hg removal in conjunction with the WGCU. The US Department of Energy’s National Energy Technology Laboratory’s (DOE/NETL) Office of Research & Development (ORD) has been developing various sorbent alternatives to address the problem of high-temperature Hg removal. This study presents analysis of the capture of Hg from syngas streams as a polishing step to attain US Environmental Protection Agency (EPA) Mercury and Air Toxics Standards (MATS) requirements for Hg (0.003 lb/GWhgross for new IGCC plants) using palladium (Pd) adsorbent being tested by DOE/NETL in association with Johnson Matthey (JM). For the present study, it was assumed that syngas is already cleaned to 5 parts per billion by weight (ppbw) Hg, and the Pd sorbent technology is used as a polishing step to achieve the EPA MATS requirements (0.003 lb/GWhgross, equivalent to 2 ppbw given representative process configuration and material flows). The incremental cost of Hg polishing and the additional capital cost needed were estimated for several scenarios/cases. These cases were differentiated by variance in the following parameters, which are important because they have direct im- pacts on additional capital costs ($/kW), and in turn impacts on the levelized cost of electricity (LCOE): 1) Pd cost (varied from $4,000 to $12,000/lb Pd); 2) Gas hourly space velocity (SV) (varied from 500 to 13,500 h-1); 3) Pd loading (varied between 2 w/w% Pd and 5 w/w% Pd); 4) Sorbent make-up rate (varied between 3%, 1%). The ranges were chosen in order to reasonably reflect, in the cases that are analyzed, the actual fluctuations that have been observed in past *Corresponding author. experience in these important parameters that affect cost (e.g., the Pd cost has kept to within the $4 to 12 k/lb range in recent years). In the case of SV, the high and low points of the range are extremes beyond which costs would either be unreasonable, or increase in cost benefit would be negligible. For a typical case (i.e., using mid-range values of the parameters, including SV of 8000 h-1, 2% Pd loading, 3% make-up rate, $9500/lb Pd cost), the increase in LCOE due to the Pd-polishing system is approximately 0.4% and the additional capital cost is ~$10/kW. As a comparison, the incremental capital cost of conventional Hg removal in an IGCC plant is ~$4 to 8/kW, and the increase in the LCOE is less than 0.4%. Results indicate that in the range of SVs from 3500 h-1 to 10,000 h-1, the Hg-polishing step is expected to function adequately and with increase of LCOE limited to about 1% - 2%. The use of a Pd sorbent-based polishing system to reduce trace Hg levels to the EPA MATS requirements for new IGCC power generation appears to be feasible and reasonably cost-effective.

Mercury chemistry of brominated activated carbons – Packed-bed breakthrough experiments

Coal-fired power plants provided between 45% and 50% of the United States net energy generation in the years between 1999 and 2010 and will continue to be a primary source of electricity into the future. Among the major environmental concerns of coal utilization is the release of mercury (Hg), which was recently regulated by the US EPA in the Mercury and Air Toxics Standards (MATS) ruling in December 2011. Among the variety of potential methods for Hg capture, activated carbon injection (ACI) is viewed by the EPA as a viable, ready technology available to energy utilities to comply with MATS. However, there remain significant questions regarding the complicated interaction between the carbon sorbent, Hg, and contaminants present in combustion flue gas, such as SO2 and NOx (NO and NO2). In this study, bromine-impregnated carbon fiber (Br-ACF) was tested for Hg capture and oxidation in a controlled flue gas environment to elucidate trends in the interaction of the flue gas components. These results are compared with prior surface analysis results from this group to provide additional support to prior conclusions. Compared to baseline capture rates in a clean environment, results indicate that NOx promotes the oxidation of Hg, while SO2 prevents the adsorption or oxidation of Hg on the Br-ACF.

Mercury exposed: Advances in environmental analysis and ecotoxicology of a highly toxic metal

Mercury exposed: Advances in environmental analysis and ecotoxicology of a highly toxic metal

Compact fluorescent lighting in Wisconsin: elevated atmospheric emission and landfill deposition post-EISA implementation

The majority of states in the USA, including Wisconsin, have been affected by elevated air, soil and waterborne mercury levels. Health risks associated with mercury increase from the consumption of larger fish species, such as Walleye or Pike, which bio-accumulate mercury in muscle tissue. Federal legislation with the 2011 Mercury and Air Toxics Standards and the Wisconsin legislation on mercury, 2009 Wisconsin Act 44, continue to aim at lowering allowable levels of mercury emissions. Meanwhile, mercury-containing compact fluorescent lights (CFL) sales continue to grow as businesses and consumers move away from energy intensive incandescent light bulbs. An exchange in pollution media is occurring as airborne mercury emissions from coal-burning power plants, the largest anthropogenic source of mercury, are being reduced by lower energy demand and standards, while more universal solid waste containing mercury is generated each time a CFL is disposed. The treatment of CFLs as a 'universal waste' by the Environmental Protection Agency (EPA) led to the banning of non-household fluorescent bulbs from most municipal solid waste. Although the EPA encourages recycling of bulbs, industry currently recycles fluorescent lamps and CFLs at a rate of only 29%. Monitoring programs at the federal and state level have had only marginal success with industrial and business CFL recycling. The consumer recycling rate is even lower at only 2%. A projected increase in residential CFL use in Wisconsin owing to the ramifications of the Energy Independence and Security Act of 2007 will lead to elevated atmospheric mercury and landfill deposition in Wisconsin.

Mercury and Air Toxics Standards Analysis Deconstructed: Changing Assumptions, Changing Results

Several recent studies have used simulation models to quantify the potential effects of recent environmental regulations on power plants, including the Mercury and Air Toxics Standards (MATS), one of the US Environmental Protection Agency’s most expensive regulations. These studies have produced inconsistent results about the effects on the industry, making general conclusions difficult. We attempt to reconcile these differences by representing the variety of assumptions in these studies within a common modeling platform. We find that the assumptions, and their differences from the way MATS will be implemented, make a substantial impact on projected retirement of coal-fired capacity and generation, investments that are required, and emissions reductions. Almost uniformly, the actual regulation, when examined in its final form and in isolation, provides more flexibility than is represented in most models. We find this leads to a smaller impact on the composition of the electricity generating fleet than most studies have predicted.

Modeling the Electricity Sector: A Summary of Recent Analyses of New EPA Regulations

Several different economic models have been applied to try to understand how new regulations by the U.S. Environmental Protection Agency (EPA) could impact coal-fired generation in the United States as well as the electricity system as a whole. This paper provides an overview of many of the key studies and the models used to analyze the potential impacts of EPA’s rules. The regulations surveyed include the Cross-State Air Pollution Rule (CSAPR), the Mercury and Air Toxics Standards (MATS), the proposed Clean Water Act (CWA) Section 316(b) rule, and the proposed Coal Combustion Residuals (CCR) rule. The models generally agree that these regulations will result in coal plant retirements, though there is far less agreement on how much generation may retire. Assumptions about the price of natural gas and the expected stringency of regulations play a key role in determining modeling results. The models provide useful guidance for policymakers when considering the potential impact of EPA regulation.

Tougher rules for mercury and other toxics

A new rule on mercury and air toxics standards, issued by the U.S. Environmental Protection Agency (EPA) on 21 December, will reduce emissions of heavy metals and acid gases from power plants. The rule, which gives existing sources of pollution up to 4 years to comply with the new standards, will affect about 1400 existing “units,” including 1100 coal‐fired units and 300 oilfired units, at about 600 power plants. EPA notes that more than half of all coal‐fired plants already deploy pollution‐control technologies. Power plants are the largest U.S. source of several pollutants—accounting for about 50% of mercury emissions and 77% of acid gas emissions—and emit the largest amounts of arsenic and other toxics, according to EPA.

AIR POLLUTION: Mercury Emissions Not Shrinking as Forecast

AIR POLLUTION: Mercury Emissions Not Shrinking as Forecast