Despacho económico ambiental de unidades térmicas de carbón

El objetivo del presente proyecto es el despacho económico-ambiental de unidades térmicas de carbón con respecto a la minimización de sus costes horarios o de sus emisiones de óxidos de nitrógeno (NOX), según convenga. Se han estudiado tanto las curvas de costes de generación como las de emisión de óxidos de nitrógeno para cinco unidades tipo de carbón para poder llevar a cabo el proyecto. Se modelizaron las curvas de emisión de óxidos de nitrógeno para las cinco unidades estudiadas mediante la simulación de la combustión del carbón en caldera con el software ASPEN PLUS®, y las curvas de costes con datos proporcionados en la publicación “Las centrales termoeléctricas: Consumos marginales, Consumos medios y costes de arranque de grupos de carbón” y otra bibliografía, para su posterior aplicación en el despacho, desarrollado en Excel y con el uso de su lenguaje de programación, VBA, para escribir un código que automatice la elección a tomar entre todas las posibilidades. Analizando tres posibles casos de generación térmica con carbón, se ha llevado a cabo el despacho económico-ambiental de las cinco unidades implicadas, con todas sus posibles combinaciones (apagado-encendido), obteniendo en cada caso lo que parece ser la manera más económica o ambiental, según convenga, de generar la potencia demandada en cada momento. ABSTRACT The aim of this project is the economic-environmental dispatch of thermal coal power plants to minimize the hourly costs of generation or the nitrogen oxides (NOX) emissions as appropriate. It have been studied both generation cost curves as nitrogen oxides emissions curves for five examples of coal power plants to carry out the project. Nitrogen oxides emissions curves were modeled for the five coal power plants simulating the coal combustion in the boiler with ASPEN PLUS® software, and generation cost curves with data provided in the publication “Las centrales termoeléctricas: Consumos marginales, Consumos medios y costes de arranque de grupos de carbón” and other publications, to be used later in the dispatch, developed in Excel, using the VBA code, to write a code that automatize the correct election between all the generation possibilities. Analizing three possible cases of thermal generation with coal, economic-environmental dispatch for the five implied power plants has been done, with all the possible combinations (generating or no generating), obtaining, in each case, the most economically or environmentally way, as appropriate, to generate the demanded power in each moment.

The NH3-Abating effect of Slurry Injection as Influenced by Soil Moisture in a Semiarid Arable Soil

Accumulation of large volumes of dilute slurries is considered one of the major problems related to intensive farming (Sommer et al., 2004). In the EU-27, more than half of the total N excretion is applied to croplands due to technical advantages for farmers (e.g. reuse of nutrients). However, the N use efficiency of slurries produced by livestock is low, i.e. only 20-52% of the excreted N is recovered by crops. Much of the remainder can be lost into the atmosphere as ammonia (NH3), nitrous oxide (N2O), dinitrogen (N2) and nitrogen oxides (NOx).

Effects of protein calorie malnutrition on tuberculosis in mice

Infectious diseases and malnutrition represent major burdens afflicting millions of people in developing countries. Both conditions affect individuals in industrialized nations, particularly the aged, the HIV-infected, and people with chronic diseases. While malnutrition is known to induce a state of immunodeficiency, the mechanisms responsible for compromised antimicrobial resistance in malnourished hosts remain obscure. In the present study, mice fed a 2% protein diet and developing protein calorie malnutrition, in contrast to well-nourished controls receiving a 20% protein diet, rapidly succumbed to infection with Mycobacterium tuberculosis. Malnourished mice exhibited a tissue-specific diminution in the expression of interferon γ, tumor necrosis factor α, and the inducible form of nitric oxide synthase in the lungs, but not the liver. The expression of these molecules critical to the production of mycobactericidal nitrogen oxides was depressed in malnourished animals in the lungs specifically at early times (<14 days) after infection. At later times, levels of expression became comparable to those in well-nourished controls, although the bacillary burden in the malnourished animals continued to rise. Nevertheless, urinary and serum nitrate contents, an index of total nitric oxide (NO) production in vivo, were not detectably diminished in malnourished, mycobacteria-infected mice. In contrast to the selective and early reduction of lymphokines and the inducible form of nitric oxide synthase in the lung, a marked diminution of the granulomatous reaction was observed in malnourished mice throughout the entire course of infection in all tissues examined (lungs, liver, and spleen). Remarkably, the progressively fatal course of tuberculosis observed in the malnourished mice could be reversed by restoring a full protein (20%) diet. The results indicate that protein calorie malnutrition selectively compromises several components of the cellular immune response that are important for containing and restricting tuberculous infection, and suggest that malnutrition-induced susceptibility to some infectious diseases can be reversed or ameliorated by nutritional intervention.

Polynitrosylated proteins: characterization, bioactivity, and functional consequences.

Chemical modification of proteins is a common theme in their regulation. Nitrosylation of protein sulfhydryl groups has been shown to confer nitric oxide (NO)-like biological activities and to regulate protein functions. Several other nucleophilic side chains -- including those with hydroxyls, amines, and aromatic carbons -- are also potentially susceptible to nitrosative attack. Therefore, we examined the reactivity and functional consequences of nitros(yl)ation at a variety of nucleophilic centers in biological molecules. Chemical analysis and spectroscopic studies show that nitrosation reactions are sustained at sulfur, oxygen, nitrogen, and aromatic carbon centers, with thiols being the most reactive functionality. The exemplary protein, BSA, in the presence of a 1-, 20-, 100-, or 200-fold excess of nitrosating equivalents removes 0.6 +/- 0.2, 3.2 +/- 0.4, 18 +/- 4, and 38 +/- 10, respectively, moles of NO equivalents per mole of BSA from the reaction medium; spectroscopic evidence shows the proportionate formation of a polynitrosylated protein. Analogous reaction of tissue-type plasminogen activator yields comparable NO protein stoichiometries. Disruption of protein tertiary structure by reduction results in the preferential nitrosylation of up to 20 thus-exposed thiol groups. The polynitrosylated proteins exhibit antiplatelet and vasodilator activity that increases with the degree of nitrosation, but S-nitroso derivatives show the greatest NO-related bioactivity. Studies on enzymatic activity of tissue-type plasminogen activator show that polynitrosylation may lead to attenuated function. Moreover, the reactivity of tyrosine residues in proteins raises the possibility that NO could disrupt processes regulated by phosphorylation. Polynitrosylated proteins were found in reaction mixtures containing interferon-gamma/lipopolysaccharide-stimulated macrophages and in tracheal secretions of subjects treated with NO gas, thus suggesting their physiological relevance. In conclusion, multiple sites on proteins are susceptible to attack by nitrogen oxides. Thiol groups are preferentially modified, supporting the notion that S-nitrosylation can serve to regulate protein function. Nitrosation reactions sustained at additional nucleophilic centers may have (patho)physiological significance and suggest a facile route by which abundant NO bioactivity can be delivered to a biological system, with specificity dictated by protein substrate.

Three-way catalysts: past, present and future

In this article, the past and the state-of-the-art in Three-Way Catalyst (TWC) technology are reviewed. The main chemical reactions occurring in a gasoline engine are discussed and also the main reactions taking place in a TWC placed in the tailpipe, namely CO and hydrocarbons oxidation and nitrogen oxides reduction to molecular nitrogen. The main components of a TWC (substrates, noble metals and cerium oxides) and their role in the different chemical reactions occurring in a TWC are described. Finally, the problem of diesel vehicles gas aftertratment is described, and the current state-of-the art in catalytic converters for these vehicles are commented.

Sourcebook, NOx control technology data /

Mode of access: Internet.

Compatibility studies of anion exchange resins.

"U.S. Atomic Energy Commission Contract AT(29-1)-1106."

Report to the Illinois General Assembly in response to House Resolution 405.

"On May 31, 2001, House Resolution 405 was adopted ..." [92nd General Assembly].

Acid rain and transported air pollutants : implications for public policy.

Mode of access: Internet.

Acid rain and transported air pollutants : implications for public policy : summary.

Mode of access: Internet.

Estimativa da poluição emitida pelos ônibus das linhas troncais da cidade de Uberlândia, MG

The transport of people and goods contributes to the deterioration of the environment in urban areas because of the generation of pollution, such as, air, noise, soil, water or visual degradation. The heavy vehicles that use diesel as fuel are mainly responsible for the emission of nitrogen oxides (NOx) and particulate matter (PM), contributing to participation of the transport sector in air pollution. In addition, there is emission of Greenhouse Gas (GHG) whose main component is carbon dioxide (CO2). In most major cities, public transportation is often considered as a less polluting alternative compared to the private vehicle, in view of the potential to reduce, per passenger, the emissions of GHG and air pollutants. The study area was the city of Uberlândia and the objects of study were the trunk lines of the Sistema Integrado de Transporte (SIT). The emissions of NOx, PM and CO2 were estimated through the bottom-up approach which used the route of each bus line and also fuel consumption obtained through simulation from the TSIS software. The software has some result limitations, there are no report about the emission of pollutants by bus, and it is not able to change specifications for the fuel used by the fleet. The results obtained through calculations of pollutants and GHG emission by the bottom-up approach show that the emission is higher when using fuel comsuption obtained in simulation than using distance. For the results considering fuel and distance there was a reduction in emissions comparing ethanol and diesel.

Effects of engine cooling water temperature on performance and emission characteristics of a CI engine operated with biofuel blend

The temperature of the coolant is known to have significant influence on engine performance and emissions. Whereas existing literature describes the effects of coolant temperature in engines using fossil derived fuels, very few studies have investigated these effects when biofuel is used. In this study, Jatropha oil was blended separately with ethanol and butanol. It was found that the 80% jatropha oil + 20% butanol blend was the most suitable alternative, as its properties were closest to that of fossil diesel. The coolant temperature was varied between 50°C and 95°C. The combustion process enhanced for both diesel and biofuel blend, when the coolant temperature was increased. The carbon dioxide emissions for both diesel and biofuel blend were observed to increase with temperature. The carbon monoxide, oxygen and lambda values were observed to decrease with temperature. When the engine was operated using diesel, nitrogen oxides emissions correlated in an opposite manner to smoke opacity; however, nitrogen oxides emissions and smoke opacity correlated in an identical manner for biofuel blend. Brake specific fuel consumption was observed to decrease as the temperature was increased and was higher on average when the biofuel was used. The study concludes that both biofuel blend and fossil diesel produced identical correlations between coolant temperature and engine performance. The trends of nitrogen oxides and smoke emissions with cooling temperatures were not identical to fossil diesel when biofuel blend was used in the engine.

Major ion chemistry of snow cores along a transect in central Dronning Maud Land, Antarctica

Among the large variety of particulates in the atmosphere, calcic mineral dust particles have highly reactive surfaces that undergo heterogeneous reactions with nitrogen oxides contiguously. The association between Ca2+, an important proxy indicator of mineral dust and NO3-, a dominant anion in the Antarctic snow pack was analysed. A total of 41 snow cores (~ 1 m each) that represent snow deposited during 2008-2009 were studied along coastal-inland transects from two different regions - the Princess Elizabeth Land (PEL) and central Dronning Maud Land (cDML) in East Antarctica. Correlation statistics showed a strong association (at 99 % significance level) between NO3- and Ca2+ at the near-coastal sections of both PEL (r = 0.72) and cDML (r = 0.76) transects. Similarly, a strong association between these ions was also observed in snow deposits at the inland sections of PEL (r = 0.8) and cDML (r = 0.85). Such systematic associations between Ca2+ and NO3- is attributed to the interaction between calcic mineral dust and nitrogen oxides in the atmosphere, leading to the possible formation of calcium nitrate (Ca(NO3)2). Forward and back trajectory analyses using HYSPLIT model v. 4 revealed that Southern South America (SSA) was an important dust emitting source to the study region, aided by the westerlies. Particle size distribution showed that over 90 % of the dust was in the range < 4 µm, indicating that these dust particles reached the Antarctic region via long range transport from the SSA region. We propose that the association between Ca2+ and NO3- occurs during the long range transport due to the formation of Ca(NO3)2. The Ca(NO3)2 thus formed in the atmosphere undergo deposition over Antarctica under the influence of anticyclonic polar easterlies. However, influence of local dust sources from the nunataks in cDML evidently mask such association in the mountainous region. The study indicates that the input of dust-bound NO3- may contribute a significant fraction of the total NO3- deposited in Antarctic snow.

Boreal forest fire impacts on lower troposphere carbon monoxide and ozone levels at the regional to hemispheric scales

Tropospheric ozone (O3) and carbon monoxide (CO) pollution in the Northern Hemisphere is commonly thought to be of anthropogenic origin. While this is true in most cases, copious quantities of pollutants are emitted by fires in boreal regions, and the impact of these fires on CO has been shown to significantly exceed the impact of urban and industrial sources during large fire years. The impact of boreal fires on ozone is still poorly quantified, and large uncertainties exist in the estimates of the fire-released nitrogen oxides (NO x ), a critical factor in ozone production. As boreal fire activity is predicted to increase in the future due to its strong dependence on weather conditions, it is necessary to understand how these fires affect atmospheric composition. To determine the scale of boreal fire impacts on ozone and its precursors, this work combined statistical analysis of ground-based measurements downwind of fires, satellite data analysis, transport modeling and the results of chemical model simulations. The first part of this work focused on determining boreal fire impact on ozone levels downwind of fires, using analysis of observations in several-days-old fire plumes intercepted at the Pico Mountain station (Azores). The results of this study revealed that fires significantly increase midlatitude summertime ozone background during high fire years, implying that predicted future increases in boreal wildfires may affect ozone levels over large regions in the Northern Hemisphere. To improve current estimates of NOx emissions from boreal fires, we further analyzed ΔNOy /ΔCO enhancement ratios in the observed fire plumes together with transport modeling of fire emission estimates. The results of this analysis revealed the presence of a considerable seasonal trend in the fire NOx /CO emission ratio due to the late-summer changes in burning properties. This finding implies that the constant NOx /CO emission ratio currently used in atmospheric modeling is unrealistic, and is likely to introduce a significant bias in the estimated ozone production. Finally, satellite observations were used to determine the impact of fires on atmospheric burdens of nitrogen dioxide (NO2 ) and formaldehyde (HCHO) in the North American boreal region. This analysis demonstrated that fires dominated the HCHO burden over the fires and in plumes up to two days old. This finding provides insights into the magnitude of secondary HCHO production and further enhances scientific understanding of the atmospheric impacts of boreal fires.