An investigation into the likely impact of oxy-coal retrofit on fire-side corrosion behavior in utility boilers

Real-time electrochemical measurements of corrosion rate were performed to evaluate the respective corrosion rates of one boiler waterwall material (SA210) and three boiler superheater materials (T22, P91 and 347H) while firing Utah Western bituminous, Illinois high-sulfur bituminous and Powder River Basin (PRB) sub-bituminous coals in a 1.5 MW pulverized coal-fired furnace. The raw average measured corrosion rates were very low, between 0.0003 and 0.016 mm/year (0.012 and 0.63 mils/year) for most materials under air- and oxy-fired conditions. For some high-sulfur conditions measured corrosion rates were as high as 0.72 mm/year (28 mils/year). Waterwall corrosion rates decreased consistently when converting from air- to oxy-firing while superheater corrosion rates generally increased, although they were less than twice the air-fired rate under most conditions. Corrosion rates for the lower alloyed materials (SA210 and T22) increased significantly during transients from reducing to oxidizing conditions. Measured increases in the corrosion rate of 347H material under high sulfur and low temperature conditions, and associated decrease in corrosion rate at higher temperatures on this alloy, were consistent with the formation of trisulphates in the superheater deposits. The increase of corrosion rate with increased metal temperatures was demonstrated, as was the consistently repeatable nature of the observed results.     

Magnitude,Frequency, and Duration Relations for Suspended Sediment in Stable (“Reference”) Southeastern Streams1

Abstract: Sediment is listed as one of the leading causes of water‐quality impairments in surface waters of the United States (U.S.). A water body becomes listed by a State, Territory or Tribe if its designated use is not being attained (i.e., impaired). In many cases, the prescribed designated use is aquatic health or habitat, indicating that total maximum daily loads (TMDL) targets for sediment should be functionally related to this use. TMDL targets for sediment transport have been developed for many ecoregions over the past several years using suspended‐sediment yield as a metric. Target values were based on data from “reference” streams or reaches, defined as those exhibiting geomorphic characteristics of equilibrium. This approach has proved useful to some states developing TMDLs for suspended sediment, although one cannot conclude that if a stream exceeds the target range, the aquatic ecosystem will be adversely impacted. To address this problem, historical flow‐transport and sediment‐transport data from hundreds of sites in the Southeastern U.S. were re‐examined to develop parameters (metrics) such as frequency and duration of sediment concentrations. Sites determined as geomorphically stable from field evaluations and from analysis of gauging‐station records were sorted by ecoregion. Mean‐daily flow data obtained from the U.S. Geological Survey were applied to sediment‐transport rating relations to determine suspended‐sediment load for each day of record. The frequency and duration that a given concentration was equaled or exceeded were then calculated to produce a frequency distribution for each site. “Reference” distributions were created using the stable sites in each ecoregion by averaging all of the distributions at specified exceedance intervals. As with the “reference” suspended‐sediment yields, there is a broad range of frequency and duration distributions that reflects the hydrologic and sediment‐transport regimes of the ecoregions. Ecoregions such as the Mississippi Valley Loess Plains (#74) maintain high suspended sediment concentrations for extended periods, whereas coastal plain ecoregions (#63 and 75) show much lower concentrations.     

Towards the development of adaptation options using climate and crop yield forecasting at seasonal to multi-decadal timescales

In order for climate forecasting to be used in developing adaptation options, the forecasts should be able to affect decisions made by stakeholders in a manner that improves outcomes. The implications of this requirement for forecasting are presented under five headings: relevance, reliability, stakeholder engagement, holism and accuracy. These characteristics are elucidated through a particular focus on the use of ensemble climate and crop simulations. Resulting recommendations, including comments on mainstreaming and seamlessness, are described using the concepts of quality and value.Adaptation options can be developed using climate forecasts on a range of timescales, from days to decades. Using the five identified characteristics, two cases are presented: (i) options based on large-area seasonal crop yield forecasting are discussed, and (ii) genotypic adaptation based on long-term climate change projections is examined. For the latter, novel analyses of existing large-area groundnut simulations are used to assess the magnitude and spatial extent of the impact of changes in the mean and variability of temperature, rainfall and humidity. The genotypic properties required to ameliorate negative impacts are then assessed and compared to observations. The processes examined act on most annual crops, making the method, and to some extent the results, broadly relevant.     

Regulatory risk control through mandatory occupational safety and health (OSH) certification and testing regimes (CTRs)

Governments make increasing use of private certification and testing infrastructures as an alternative for traditional regulatory arrangements in several areas including occupational safety and health (OSH).This research, commissioned by the Dutch Inspectorate for Work and Income (IWI), concerns an analysis of risk control of four certification and testing regimes (CTRs) in the Netherlands, three mandatory regimes and one non-mandatory regime. The aim was to create a better understanding of problems that may arise in the risk control through such regimes and to identify critical processes and factors that can affect the risk control process.The results of this research are reported in two papers in this special issue (see also Zwetsloot et al., this issue). This one presents an analysis of the risk control at the regulatory level, and its associated critical factors and processes. These critical factors are clustered in four essential processes: the regulatory choice for a CTR, the definition of requirements for the auditing or inspection regime, the certification and testing processes as such, and the processes needed for the self-correcting or learning capability of the CTR. Jointly, these factors and processes form a framework for both the design and the evaluation of such regimes. The case studies clearly demonstrate that these critical factors may undermine the effectiveness of such regulatory practices. We propose that a further development of our framework should be used in the (re)design process for proposed and existing CTRs, and in the process of independent evaluation of such regimes.     

Seasonal changes in the diet and feeding behaviour of a top predator indicate a flexible response to deteriorating oceanographic conditions

Shifts in the diet of top predators can be linked to changes in environmental conditions. In this study, we tested relationships between environmental variation and seasonal changes in diet of a top predator, the grey-headed albatross Thalassarche chrysostoma, breeding at Bird Island, South Georgia in an austral summer of 1999/2000. Oceanographic conditions in that year around South Georgia were abnormal (i.e. anomalously high sea surface temperature to a relative 19-year long-term mean). The diet of grey-headed albatrosses showed high seasonal variation, shifting from cephalopods (42.9 % by mass) in late February to Antarctic krill Euphausia superba (58.3 %) in late April, and grey-headed albatrosses breeding performance was low (16.8 %). This study shows these albatrosses did not manage to find sufficient alternative prey and highlight the risk to top predators if there is an increase in the frequency or severity of food shortages in Antarctic waters.     

The Tyndall coastal simulator

The threat of sea-level rise and climate change means that coastal managers are being increasingly asked to make long-term assessments of potential coastal impacts and responses. In the UK, shoreline management planning (for flood and erosion hazards) and spatial planning now takes a 100 year perspective. An integrated framework across a wide range of physical and social issues is required for the assessment of coastal impacts and consequently for making sound management decisions. This paper provides an overview of the development of the ‘Tyndall Coastal Simulator’ including the underlying philosophy that is being followed. The Simulator is based on a series of linked climate models (CM) within a nested framework which recognises three spatial scales: (i) the global (GCM) scale; (ii) the regional scale and (iii) the Simulator Domain (a physiographic unit, such as a coastal sub-cell). Within the nesting, the larger scale provides the boundary conditions for the smaller scale. The models feed into each other and describe a range of relevant processes: sea level, tides, surges, waves, sediment transport and coastal morphology. Different climate scenarios, as well as the range of uncertainty, are being explored. Communication of results is a major issue and the Simulator includes a dedicated GIS-based user interface that allows a wide range of queries of model outputs. The paper demonstrates the possibility of developing an integrated framework that is multi-scale and capable of linking various models in order to simulate complex coastal processes and consequently allowing long-term assessments that are useful for setting future management plans.     

Heterogeneity of Hydrologic Response in Urban Watersheds1

Meierdiercks, Katherine L., James A. Smith, Mary Lynn Baeck, and Andrew J. Miller, 2010. Heterogeneity of Hydrologic Response in Urban Watersheds. Journal of the American Water Resources Association (JAWRA) 46(6):1221–1237. DOI: 10.1111/j.1752-1688.2010.00487.x Abstract: The changing patterns of streamflow associated with urbanization are examined through analyses of discharge and rainfall records for the study watersheds of the Baltimore Ecosystem Study (BES). Analyses utilize a decade (1999-2008) of observations from a dense U.S. Geological Survey stream gaging network and Hydro-NEXRAD radar rainfall fields. The principal study watershed of the BES is Gwynns Falls (171 km²). Focus is given to two Gwynns Falls basins with contrasting patterns and histories of development, Dead Run and Upper Gwynns Falls. The sharp contrasts in streamflow properties between the basins reflect the differences in urban development prior to implementation of stormwater management regulations (much of Dead Run) and development for which stormwater management is an integral part of the hydrologic system (Upper Gwynns Falls). The mean annual runoff in Dead Run (558 mm) is 35% larger than that of Upper Gwynns Falls; larger contrasts in runoff properties typify the “warm season” and are linked to storm event hydrologic response. Spatial heterogeneities in storm event response are reflected in seasonal and diurnal properties of streamflow. Analyses of storm event response are presented for June 2006, during which monthly rainfall over the BES region ranged from less than 150 to more than 500 mm. Baisman Run, the BES forest reference watershed, and Moores Run, a highly urbanized watershed in Baltimore City, provide “end-member” representations of urban impacts on streamflow.     

Groundwater circulation well operation using wind turbine–generated energy

An investigation was conducted regarding the potential economic benefits associated with using a wind turbine to power a groundwater circulation well (GCW) at the former Nebraska Ordnance Plant Superfund site. The first phase of the investigation used a 10‐kilowatt‐rated grid inter‐tie wind turbine to partially offset the purchase of electricity from the utility company. The second phase consisted of the conversion of the grid inter‐tie system to an off‐grid system that stored energy using batteries. During the second phase, the GCW system was operated using either wind turbine power or utility power, and the other system components were operated using utility power. The study showed that a significant amount of power purchased from the utility company was used for nonessential purposes (other than operating the GCW pump and essential treatment components). One nonessential power consumer was the continuous heating of the equipment shelter for operator comfort during their 10‐minute visit every few days. Wind‐turbine reduction in utility power consumption was evaluated, and the operating time of a hypothetical system powered solely by the wind turbine was compared to the actual GCW operating time. This study indicates that retrofitting this GCW system did not economically offset power costs from a cheap, readily available grid system. Perhaps at a remote location with a more energy‐efficient design and operation and the inclusion of green power benefits (in some monetary amount), the wind turbine results will be more favorable. The study of a renewable energy application at the site highlighted opportunities for significant electrical energy savings regardless of the source of the electricity. © 2008 Wiley Periodicals, Inc.