Oxygen supply for oxyfuel CO2 capture

This paper presents the results of a study to develop Air Products’ air separation unit (ASU) offerings for oxyfuel coal CO₂ capture projects. A scalable “reference plant” concept is described to match particular sizes of power generation equipment, taking into account factors such as safety, reliability, operating flexibility, efficiency, and low capital cost. We describe the selection of a process cycle to exploit the low purity requirements, as well as the options for compression machinery and drivers as the scale of the plant increases and the sizes of referenced equipment limit the possibilities. We also explore integration with other elements of the system, such as preheating condensate or heating and expanding pressurised nitrogen. In addition, we consider how the ASU affects the flexibility of the oxyfuel system and discuss how its power consumption can be reduced during periods of high power demand. Finally, the advantages and disadvantages of different execution strategies for air separation unit projects are discussed, as well as alternative commercial models for the supply of oxygen.     

Full-scale use of glycogen-accumulating organisms for excess biological carbon removal

The purpose of this study has been to verify the efficient full-scale applicability of glycogen-accumulating organisms (GAOs) for excess biological carbon removal, that is, for removing more carbon substrate than the amount of available nutrients would allow in the conventional activated sludge process of microbial growth. This aims to cost-effectively overcome the problem of viscous bulking occurring in a fully aerated system, with nutrient deficiency. Analytical data measured at the wastewater treatment plant of the Balatonboglár (BB) winery in Balatonboglár, Hungary, containing consecutive unaerated and aerated activated sludge basins, reflected a high performance with efficient carbon removal and good sludge settling, without dosing any external nutrient source to the severely nitrogen- and phosphorous-deficient influent. Supplementary laboratory-scale batch experiments and microbiological tests verified the abundance of GAOs in the activated sludge system and elucidated their role in efficient excess biological carbon removal.     

Estimating Future NO2 Levels in the Greater Los Angeles Area by Source–Type Contribution

Two indicator pollutants, carbon monoxide (CO) for mobile source influence and sulfur dioxide (SO₂) for stationary source influence, were used to estimate source-type contributions to ambient NO₂ levels in a base year and to predict NO₂ concentrations in a future year. For a specific source-receptor pair, the so-called influence coefficient of each of three source categories (mobile sources, power plants, and other stationary sources) was determined empirically from concurrent measurements of CO and SO₂ concentrations at the receptor site and CO and SO₂ emissions from each source category in the source area. Those coefficients, which are considered time invariant, were used in conjunction with the base year and future year NO _x emission values to estimate source-type contribution to ambient NO₂ levels at seven study sites selected from the Greater Los Angeles area for both the base year period, 1974 through 1976, and the future goal year of 1987 in which the air quality standards for NO₂ are to be attained. The estimated NO₂ air quality at the seven sites is found to meet the national annual standard of 5 pphm and over 99.9% of total hours, the California 1-hr NO₂ standard of 25 pphm in 1987. The estimated power plant contributions to ambient NO₂ levels are found to be considerably smaller than those to total NO _x emissions in the area. Providing that reasonably complete air quality and emissions data are available, the present analysis method may prove to be a useful tool in evaluating source contributions to both short-term peak and long-term average NO₂ concentrations for use in control strategy development.     

Dental fluorosis linked to degassing of Ambrym volcano, Vanuatu: a novel exposure pathway

Ambrym in Vanuatu is a persistently degassing island volcano whose inhabitants harvest rainwater for their potable water needs. The findings from this study indicate that dental fluorosis is prevalent in the population due to fluoride contamination of rainwater by the volcanic plume. A dental survey was undertaken of 835 children aged 6–18 years using the Dean’s Index of Fluorosis. Prevalence of dental fluorosis was found to be 96% in the target area of West Ambrym, 71% in North Ambrym, and 61% in Southeast Ambrym. This spatial distribution appears to reflect the prevailing winds and rainfall patterns on the island. Severe cases were predominantly in West Ambrym, the most arid part of the island, and the most commonly affected by the volcanic plume. Over 50 km downwind, on a portion of Malakula Island, the dental fluorosis prevalence was 85%, with 36% prevalence on Tongoa Island, an area rarely affected by volcanic emissions. Drinking water samples from West Ambrym contained fluoride levels from 0.7 to 9.5 ppm F (average 4.2 ppm F, n = 158) with 99% exceeding the recommended concentration of 1.0 ppm F. The pathway of fluoride-enriched rainwater impacting upon human health as identified in this study has not previously been recognised in the aetiology of fluorosis. This is an important consideration for populations in the vicinity of degassing volcanoes, particularly where rainwater comprises the primary potable water supply for humans or animals.     

The effects of ammonium and phosphate enrichments on clorophyll a,pigment ratio and species composition of phytoplankton of Vineyard Sound

Seawater containing natural phytoplankton populations from Vineyard Sound, USA was enriched in the laboratory with three levels each of ammonium and phosphate and with a combination of ammonium and phosphate which provided three different N:P ratios. The addition of ammonium produced more cells and chlorophyll a than the control or the phosphate enrichments. However, enrichment with ammonium and phosphate, regardless of the N:P ratio, yielded the most cells and chlorophyll a. Thus, nitrogen seems to be the primary limiting nutrient, with phosphate showing secondary limiting effects. The ratios of photosynthetic pigments decreased with the increased chlorophyll a production in the enriched cultures. There were no significant changes in the species composition within the cultures, so that the observed changes in pigment ratio and chlorophyll a content were due to physiological responses.     

Use of biological monitoring in the assessment of effects of mining wastes on aquatic ecosystems of the alligator rivers region,tropical Northern Australia

The primary objective of the biological monitoring program of the ARRRI is to develop techniques and procedures to monitor and assess effects of the mining and processing of ores on aquatic ecosystems of the Region. Studies have been made in a seasonal tributary (Magela Creek) of the East Alligator River near the Ranger Uranium Mine, and in the upper South Alligator River (SAR) near the Coronation Hill gold, platinum and palladium prospect. Ranger and Coronation Hill are enclosed by Kakadu National Park, environmental safeguards for which require the minimization of impairment of water quality in the aquatic ecosystems. Present studies on Magela Creek are designed to verify the adequacy of release standards, based on biological tests, in protecting the aquatic environment during and after releases of waste-water from Ranger during the Wet season. Detection of short-term effects will be sought by either creekside orin situ monitoring methods. The detection and assessment of any longer-term impacts, however, will rely chiefly on comparisons of post-release data with those of historical baselines. Such baseline information is provided by studies on the structure of macroinvertebrate and fish communities and/or on concentrations of elements in organisms in those communities, in Magela Creek and SAR catchments.     

Using electromagnetic induction technology to predict volatile fatty acid, source area differences

Subsurface measures have been adapted to identify manure accumulation on feedlot surfaces. Understanding where manure accumulates can be useful to develop management practices that mitigate air emissions from manure, such as odor or greenhouse gases. Objectives were to determine if electromagnetic induction could be used to predict differences in volatile fatty acids (VFA) and other volatiles produced in vitro from feedlot surface material following a simulated rain event. Twenty soil samples per pen were collected from eight pens with cattle fed two different diets using a predictive sampling approach. These samples were incubated at room temperature for 3 d to determine fermentation products formed. Fermentation products were categorized into acetate, straight-, branched-chained, and total VFAs. These data were used to develop calibration prediction models on the basis of properties measured by electromagnetic induction (EMI). Diet had no significant effect on mean volatile solids (VS) concentration of accumulated manure. However, manure from cattle fed a corn (Zea mays L.)-based diet had significantly ( P ≤ 0.1) greater mean straight-chained and total VFA generation than pens where wet distillers grain with solubles (WDGS) were fed. Alternately, pens with cattle fed a WDGS-based diet had significantly (P ≤ 0.05) greater branched-chained VFAs than pens with cattle fed a corn-based diet. Many branched-chain VFAs have a lower odor threshold than straight-chained VFAs; therefore, emissions from WDGS-based diet manure would probably have a lower odor threshold. We concluded that diets can affect the types and quantities of VFAs produced following a rain event. Understanding odorant accumulation patterns and the ability to predict generation can be used to develop precision management practices to mitigate odor emissions.     

Study of individual reactions of the sour compression process for the purification of oxyfuel-derived CO2

Following the feasibility study of sour compression process as a novel purification method of producing NO_x-free, SO₂-free oxyfuel-derived CO₂ using actual fluegas, in this paper, we present the study of the individual reactions taking place in the process in a controlled environment. We have previously showed that an increase of NO/NO₂ concentration in the inlet stream is beneficial for SO₂ removal as NO₂ promotes SO₂ oxidation and the further removal as liquid acid. In this study we show that the reaction SO₂ + NO₂ → SO₃ + NO does not take place significantly in the absence of liquid water at a range of conditions relevant to the sour compression process. When liquid water is present, SO₂ is oxidised by NO₂ regenerating NO with the rate of conversion of SO₂ being dependent on the acid concentration in the liquid. The formation of small liquid droplets where very low levels of pH (?0) can be reached is shown to be of great importance to the SO₂ + NO₂ conversion process.     

Protecting off-site populations and site workers from vapor discharges during shallow soil mixing at the North Carolina State University National Priorities List Site

Although vapor monitoring is generally a component of remedial action activities, most sites do not have routine gaseous releases or vapor clouds erupting from the soil during implementation of the cleanup process (or during cleanup of the site). At the North Carolina State University Lot 86 National Priorities List Site, over 8410 m3 (11,000 yd3) of chemical waste was disposed at the Site, including organic solvents and shock-sensitive and air- and water-reactive compounds. During the Remedial Action, it was imperative to protect site workers and off-site populations from potential inhalation exposures. Engineering controls were incorporated into the shallow soil mixing process to limit the release of gaseous compounds. To quantify potential exposures to on-site and off-site receptors, modeling was conducted to evaluate potential exposure routes and migration pathways. To demonstrate acceptable levels of airborne constituents, a multifaceted air sampling and monitoring program was implemented. To ensure that potential exposures could be quantified, passive dosimeters, continuous real-time monitoring, time-weighted whole air sampling, and grab samples of vapor clouds were all critical components of the air monitoring program. After the successful completion of the Remedial Action, the pre-Resource Conservation and Recovery Act (RCRA) chemical waste generated from the University's educational and research laboratories was entirely encapsulated and neither on-site workers nor off-site populations were exposed to analyzed compounds above any health-based action level (i.e., 15-min short-term exposure limit [STEL], 8-hr threshold limit value, or time-weighted average permissible exposure limit).