Fossil Units Research Articles

Analysis of the useable properties of coal-water fuel modified with chemical compounds

Due to the protection of the environment, one should seek to rationally use conventional fuels and explore new ways to obtain more energy per unit of fossil fuel. For this reason, attempts have been made to prepare coal-water slurries. Coal materials that belong to different assortments: a qualified steam coal (q. s. coal), fine coal and sludge coal were used. The tests were performed on a laboratory scale in a ball mill. The suspensions contained coal material, water and a stabilising agent: sodium methacrylate, Triton X-405 or rapeseed oil. On the basis of the results, the most favourable parameters of process have been chosen (type of raw material and additive, additive content and grinding time). The most favourable process parameters of preparing coal-water suspensions were as follow: q. s. coal with sodium methacrylate as an additive in an amount of 8.0g/kg and 60min milling time. These parameters enabled to obtain suspension characterised by stability at 9.4mm, the equivalent diameter of particles had 6.3μm, density was equal to 1.16g/cm3 and viscosities values were 22.2 mPa·s (shear speed of 100rev/min) and 12.7 mPa·s (shear speed of 200rev/min). The resulting suspensions are characterised by low viscosity and density, small equivalent diameters and high stability.

Economic dispatch optimization algorithm based on particle diffusion

Due to the widespread installation of emissions control equipment in fossil fuel-fired power plants, the cost of emissions control needs to be considered, together with the plant fuel cost, in providing economic power dispatch of those units to the grid. On the other hand, while using wind power decreases the overall power generation cost for the power grid, it poses a risk to a traditional grid, because of its inherent stochastic characteristics. Therefore, an economic dispatch optimization model needs to consider all of the fuel cost, emissions control cost and wind power cost for each of the generating unit conforming the fleet that meets the required grid power demand. In this study, an optimization algorithm referred as diffusion particle optimization (DPO) is proposed to solve such complex optimization problem. In this algorithm, Brownian motion theory is used to guide the movement of particles so that the particles can search for an optimal solution over the entire definition region. Several benchmark functions and power grid system data were used to test the performance of DPO, and compared to traditional algorithms used for economic dispatch optimization, such as, particle swarm optimization and artificial bee colony algorithm. It was found that DPO has less probability to be trapped in local optimums. According to results of different power systems DPO was able to find economic dispatch solutions with lower costs. DPO was also used to analyze the impact of wind power risk and fossil unit emissions coefficients on power dispatch. The result are encouraging for the use of DPO as a dynamic tool for economic dispatch of the power grid.

A fungal reproductive unit from the Lower Devonian Rhynie chert (Aberdeenshire, Scotland) that demonstrates an unusual hyphal investment pattern

The Early Devonian Rhynie chert has yielded the oldest evidence of hyphal investments (= mantles) in fungal reproductive units, with four different investment morphologies documented to date. This paper describes an unusual fungal reproductive unit from the Rhynie chert that is spheroid–elongate in outline, up to 60 μm in diameter, and consists of a thin-walled central cavity enveloped in a plectenchymatous or pseudoparenchymatous investment of tightly abutting, interwoven hyphae; pores extend through the investment. Several specimens contain a single spherical structure in the cavity. Because the structure of the investment differs from that seen in all other fossil fungal reproductive units, the new genus Scepasmatocarpion and species S. fenestrulatum are proposed for the new form. The systematic affinities of S. fenestrulatum remain unresolved. Nevertheless, the fossils support the hypothesis that the diversity of the fungi that produced hyphal envelopes was extensive by the Early Devonian.

Assessing the potential of hybrid fossil–solar thermal plants for energy policy making: Brayton cycles

This paper proposes a first study in-depth of solar–fossil hybridization from a general perspective. It develops a set of useful parameters for analyzing and comparing hybrid plants, it studies the case of hybridizing Brayton cycles with current solar technologies and shows a tentative extrapolation of the results to integrated combined cycle systems (ISCSS). In particular, three points have been analyzed: the technical requirements for solar technologies to be hybridized with Brayton cycles, the temperatures and pressures at which hybridization would produce maximum power per unit of fossil fuel, and their mapping to current solar technologies and Brayton cycles. Major conclusions are that a hybrid plant works in optimum conditions which are not equal to those of the solar or power blocks considered independently, and that hybridizing at the Brayton cycle of a combined cycle could be energetically advantageous.

An assessment of energy balance from sugar-based ethanol for fuel-saving and climate policy - the case of an island economy

The study assesses the efficiency of sugar-based ethanol production in Mauritius using the net energy balance and energy ratio. The findings indicate a positive net energy balance. For every one unit of fossil fuel used, the system returns more than six times in terms of renewable energy from ethanol. The fuel savings and other economic benefits which may be accrued to Mauritius are discussed. The sensitivity analysis shows that the fossil energy consumed in the production of fertilisers and in the transportation of feedstock to factory represents the main components which influence efficiency indicators. Greening the supply chain may enhance the efficiency and sustainability of bio-ethanol production systems. Green strategies may include the use of organic fertilisers, clean technology, and sustainable transportation and land use. The efficiency indicators can also be used to guide the CDM for sugar-based ethanol project.

Quaternary coral reefs of the Red Sea coast, Egypt: diagenetic sequence, isotopes and trace metals contamination

This study focuses on the diagenetic sequence under marine and meteoric conditions as well as isotopes and trace metals contamination in Quseir and Gebel Zeit areas along the Egyptian Red Sea coast through a series of modern and fossil corals, Porites lutea and Favites pentagona. The diagenetic sequence begins with deposition of thin fringes of syntaxial aragonite and micritic high-magnesian calcite in the modern corals to completely altered Porites and partially altered Favites to low-magnesium calcite in the oldest Pleistocene unit. Average δ18O and δ13C values of Pleistocene corals in the two studied areas were lower than those of modern corals. Values of modern corals and lower fossil unit indicated coralline limestone, while those of middle and upper fossil units indicated fresh water influences. Average values of trace metals in modern corals were higher than those of Pleistocene counterpart except for Mn. Modern coral samples recorded enrichment in the average values of Pb, Zn, and Mn at Quseir area and enrichment in Co, Cu, and Ni at Gebel Zeit area. This may be attributed mostly to different tourist activities, landfill due to increase urbanization and nearby of Quseir area from the old phosphate harbor at El Hamrawin area, as well as oil exploration and production activities in the Gulf of Suez area. Also, results indicated that most samples of Porites have high concentration of trace metals than in Favites, especially in Cu, Zn, Mn, and Pb. This may due to high amounts of intergranular porosity and high total surface area of Porites in contrast to Favites.

The Interdependence of Electricity and Natural Gas: Current Factors and Future Prospects

The growing interdependence of the nation's electricity and natural gas systems presents challenges to the reliable and efficient operation of both systems. Shale gas developments, retirement of aging fossil units, and increases in variable renewable generation are likely to increase the prominence of natural-gas-fired generation and interdependence risks. The authors review factors at the intersection of electricity and natural gas markets and operations, and present ways to address the risks.

Inferring ecological disturbance in the fossil record: A case study from the late Oligocene of Ethiopia

Environmental disturbances profoundly impact the structure, composition, and diversity of modern forest communities. A review of modern studies demonstrates that important characteristics used to describe fossil angiosperm assemblages, including leaf margin type, plant form, plant diversity, insect herbivore diversity and specialization, and variation in herbivory among plant species, differ between early and late successional forests. Therefore, sequences of fossil floras that include a mix of early and later successional communities may not be appropriate to study long-term temporal trends or biotic effects of climate, latitude, or other variables. We conducted sedimentological, paleobotanical, and insect damage analyses at two contemporaneous late Oligocene (27–28 Ma) leaf localities in the Chilga Basin, northwest Ethiopia, to test the hypothesis that successional stage explains variation between the assemblages. The Guang River and Bull's Bellow fossil plant localities are stratigraphically equivalent and only 1.5 km apart, but they have no plant species in common. Sedimentary structures at Bull's Bellow suggest multiple episodes of deposition and a more disturbed environment than the single, featureless mudstone that composes the Guang River fossil unit. Bull's Bellow has a significantly higher percentage of plant species with toothed margins, lower plant and insect herbivore damage diversity, and less specialized herbivore damage than Guang. Furthermore, the nearest living relatives of many of the Bull's Bellow plant species are associated with early successional forests, whereas the Guang River plants are a mix of early and late successional species. Thus, the physiological and ecological attributes of the Guang flora are consistent with a more mature forest community, and the differences between the two floras emphasize the importance of collecting multiple floras from the same stratigraphic level in order to account for landscape-level ecological processes. More specifically, accurate estimates of diversity and feeding specialization in tropical, angiosperm-rich fossil assemblages are essential to address adequately the origin and persistence of relatively high species diversity in the modern tropics, and diversity differences between regions such as modern tropical Africa and South America.

A decomposition analysis of CO2 emissions in the United States

This article decomposes the growth in US CO2 emissions by state. Using the Logarithmic Mean Divisia Index (LMDI) method, we account for CO2 emissions change in each state between 1990 and 2004. The change is decomposed into five effects: (a) emissions per unit of fossil fuel; (b) share of fossil fuel in total energy consumption; (c) energy intensity; (d) gross state product per capita and (e) population. Results show that for the past 15 years gains in the efficiency of energy use in the economy, the lowering share of fossil fuels in total energy consumption and lowering of emissions intensity of fuels all contributed to offsetting the effect of Gross Domestic Product (GDP) per capita and the population growth in carbon emission across the US.

Effects and costs of policies to increase bioenergy use and reduce GHG emissions from heating in Norway

In many European countries, the use of policy measures to decrease greenhouse gas (GHG) emissions from energy consumption, including heating, is high on the political agenda. Also, increasing the absolute consumption of bioenergy seems to partly be an objective in itself. But neither the costs of replacing fossil fuels with bioenergy in heating, nor the effects on the GHG emission account are clear. This study analyses first the avoided GHG emissions from substituting one energy unit of fossil fuel with forest based bioenergy (wood fuel) in several heating technologies. Secondly, the effects on bioenergy production of two policy measures in Norway - higher tax on domestic heating oil and paraffin and investment grants to district heating installations based on wood fuels - are investigated. Thereafter, the results are combined to display how the emissions from heating are affected. Finally, the achievements are compared to the costs. The analysis is done by using a partial, spatial equilibrium model of the Norwegian forest sector, wood fuels included. Based on model runs we conclude that a tax of 60 €/CO 2eq on competing fossil fuels could increase the bioenergy use in district heating installations with almost 4000 GWh/year. The same amount of bioenergy could be used in pellet stoves and central heating systems, but a higher tax is then necessary. 50% investment grant to district heating installations may also have a large effect on the bioenergy use, but the effect of the subsidies decreases rapidly if applied together with a tax. Around 70% of the emissions from heating in Norway may potentially be avoided, but such achievements depend on very high taxes on fossil fuels. Both taxes and subsidies may greatly influence the energy market, but should be used with caution in order to obtain the preferred goals. Few similar studies are carried out in this field, and the results might be of interest for the bioenergy industry and the energy policy authorities.

CFD studies on burner secondary airflow

In many fossil power plants operating today, there is insufficient means to assure the proper balancing of the secondary airflows between the individual burners of wall-fired units. This mismatch leads to decreased boiler efficiency and increased emissions. In this study, a computational fluid dynamics (CFD) modeling of a fossil power plant wind box was performed. The model solved the three-dimensional Reynolds averaged Navier–Stokes equations with the k – ε turbulence model. The CFD results were validated by the experimental data taken from a 1/8th scale model of a wall-fired fossil unit. Simulations under various mass flow rates specified at inlet, various baffle positions and two opening conditions of the burners were obtained to identify the optimum design in terms of the equalization of the secondary airflow through the burners. This study demonstrated that the combination of experimental and CFD approach can be an effective tool in the research of burner secondary airflow balancing.

THE LIFE ASSESSMENT OF STEAM TURBINE ROTORS FOR FOSSIL POWER PLANTS

The operational mode of thermal power plants has been changed from base load to duty cycle. From the changeover, fossil power plants cannot avoid frequent thermal transient states, for example, start up and stop, which results in thermal fatigue damage at the heavy section components. The rotor is the highest capital cost component in a steam turbine and requires long outage for replacing with a new one. For an optimized power plant operational life, inspection management of the rotor is necessary. It is known in general that the start-up and shutdown operations greatly affect the steam turbine life. The start-up operational condition is especially severe because of the rapid temperature and rotational speed increase, which causes damage and reduction of life of the main components life of the steam turbine. The start-up stress of a rotor which is directly related to life is composed of thermal and rotational stresses. The thermal stress is due to the variation of steam flow temperature and rotational stress is due to the rotational speed of the turbine. In this paper, the analysis method for the start-up stress of a rotor is proposed, which considers simultaneously temperature and rotational speed transition, and includes a case study regarding a 500MW fossil power plant steam turbine rotor. Also, the method of quantitative damage estimation for fatigue-creep damage to operational conditions, is described. The method can be applied to find weak points for fatigue-creep damage. Using the method, total life consumption can be obtained, and can be also be used for determining future operational modes and life extension of old fossil power units.

Life Prediction of High Pressure Steam Turbine Rotor

The operation mode of thermal power plants has been changed from the base load to duty cycle. From the changeover, fossil power plants cannot avoid frequent thermal transient state, for example, start up and stop, which results in thermal fatigue damage at the heavy section components. The rotor is the highest capital cost component in steam turbine and requires long outage for replacing the new one. For optimized power plant operation life and inspection management of rotor is necessary. It is known as general that start-up and shutdown operation greatly affect on steam turbine life. The start-up operation condition is especially severe because of the rapid temperature and rotational speed increase, which causes damage and reduction of main components life of steam turbine. The start-up stress of rotor which is directly related life is composed of thermal and rotational stresses. The thermal stress is due to the variation of steam flow temperature and rotational stress is due to the rotation speed of itself. In this paper, the analysis method of start-up stress of rotor which considers simultaneously temperature and rotation speed transition is proposed, which includes a case study regarding 500MW fossil power plant steam turbine rotor. Also, the method of damage quantitative estimation of fatigue damage to operation condition is described. The method can be applied to find weak points to the fatigue damage. Using the method, total life consumption can be obtained, and can be also used for determining future operation mode and the life extension of old fossil power units.

Skeletal Extension Rates of Cenozoic Caribbean Reef Corals

There has been significant biological and environmental change in Caribbean coral reefs during the past 30 million years, including two periods of accelerated turnover of species in the zooxanthellate coral biota that may have been correlated with changes in regional sea-surface productivity during the Early Miocene and the Early Pleistocene. Skeletal extension rates measured on x-radiographs of 11 massive genera of fossil corals collected from Late Oligocene to Pleistocene units from across the Caribbean were analyzed to determine whether average coral growth responded to these regional environmental changes. The observed patterns were evaluated by comparisons with records of Recent coral growth rates taken from published literature. These analyses suggest that there is significant variation in average growth rate among corals living in the Recent Indo-west Pacific, eastern Pacific, and Caribbean, even when broad ranges of taxa and habitats are intermingled. When applied to fossils, a similar analysis suggests that rates of growth do not change overall through time. One exception is during the Late Miocene, when rates of growth were significantly lower than from other fossil units or for Recent colonies from the Caribbean. However, the Late Miocene colonies sampled for this study lived in relatively deep, turbid habitats, so the observed reduced growth rates may have resulted from local low availability of light. Similar facies were not sampled in other stratigraphic intervals, so there is no strong evidence for reduced regional average growth rates for Caribbean corals during the past 30 million years.

Late Holocene relative sea-level changes and the earthquake deformation cycle around upper Cook Inlet, Alaska

Multiple peat-silt couplets preserved in tidal marsh sediment sequences suggest that numerous great plate boundary earthquakes caused the coast around Cook Inlet, Alaska, to subside over the past 3500 years. Field and laboratory analyses of the two youngest couplets record the well-documented earthquake of AD 1964 and the penultimate one, approximately 850 cal yr BP. Diatom assemblages from a range of modern day estuarine environments from tidal flat through salt marsh to acidic bog produce quantitative diatom transfer function models for elevation reconstructions based on fossil samples. Only nine out of 124 fossil assemblages analysed, including previously published data for the AD 1964 earthquake, have a poor modern analogue. Calibration of fossil samples indicate co-seismic subsidence of 1.50±0.32 m for AD 1964, similar to measurements taken after the earthquake, and 1.45±0.34 m for the ∼850 cal yr BP earthquake. Elevation standard errors for individual fossil samples range from ∼0.08 m in peat layers to ∼0.35 m in silt units. Lack of a chronology within fossil silt units prevents identification of changes in the rate of recovery and land uplift between the post-seismic and inter-seismic periods. However, preservation of multiple peat-silt couplets indicates no net emergence over multiple earthquake cycles. Glacio-isostatic movements from Little Ice Age glacier advance and retreat explains a ∼0.15 m relative sea-level oscillation recorded within the peat layer subsequently submerged as a result of the AD 1964 earthquake. Before both this and the ∼850 cal yr BP earthquake, diatom assemblages suggest pre-seismic relative sea-level rise of ∼0.12±0.13 m, representing possible precursors to great earthquakes.

Greenhouse gas emissions from final harvest fuel chip production in Finland

Abstract Renewable energy sources have been identified to play an important role in mitigating climate change. The main reason is that carbon dioxide emission is avoided when fossil fuels are replaced. This paper presents a study focusing on direct and indirect greenhouse gas emissions from fuel chip production in Finland. The fuel chips studied were produced from logging residue at final harvest. Five different fuel production chains were considered. The calculations showed that fuel chip production from the residues of final harvest is very efficient from the viewpoint of energy use during collection, chipping and transportation. Only an input of 2–3% of the produced energy is needed, which means that roughly 30 to 50 units of bioenergy is produced for every unit of (fossil) energy consumed. The emissions from collecting, chipping and transporting the residues were evaluated to be about 4–7 kg CO 2 eq MWh chip - 1 depending on harvesting and chipping methods and transportation distance. Emissions of greenhouse gases (other than CO 2 ) from burning forest residues in a modern CHP-plant were evaluated to be small, about 2 kg CO 2 eq MWh chip - 1 . If nitrogen losses are compensated for with fertilisation, the additional greenhouse gas emissions were calculated to be about 7 kg CO 2 eq MWh chip - 1 . The calculations showed that in a favourable situation as much as 97–98% of the greenhouse gas emissions could be avoided by substituting a fossil fuel with wood fuel, but even in an unfavourable situation the amount avoided should be higher than 75%.

Increasing electricity generation per unit of fossil fuel so expended in diesel engines

Increasing electricity generation per unit of fossil fuel so expended in diesel engines

Biological nitrogen fixation associated with tropical pasture grasses

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000 The semi-humid or humid tropics are ideal for the production of large quantities of biomass from fast-growing C4 grasses, but high yields normally require large quantities of fertiliser, especially N, which has a very high input from fossil fuels (natural gas). A program has been started recently to use elephant grass (Pennisetum purpureum Schum.) to substitute firewood as a fuel and also to make charcoal for iron production. In this case, any large N fertiliser additions would mean that the yield of bio fuel per unit of fossil fuel invested would be detrimentally affected. In this study, we report on the potential for the selection of genotypes of fast-growing C4 tropical grasses of the genera Pennisetum and Brachiaria for their capacity to obtain N inputs from plant-associated biological nitrogen fixation (BNF). Fourteen genotypes each of Brachiaria and Pennisetum were screened for BNF contributions by growing them in 15N-labelled soil. In the case of the Pennisetum, after a suitable cutting height for the crop had been selected, there were large differences in dry matter production, N accumulation and 15N enrichment. The differences in 15N enrichment between genotypes were statistically significant and BNF inputs were estimated as high as 41% of accumulated N. In the study on Brachiaria genotypes, potential inputs of BNF seemed lower. Only one or two genotypes of B. brizantha and B. ruziziensis obtained more then 20% of their N from BNF. The N2-fixing bacteria that were most commonly associated with shoots and roots the Pennisetum genotypes were of the genus Herbaspirillum, but predominantly of a recently described new species. The Brachiaria spp. from three different sites (Rio de Janeiro, Goânia, Bahia) were predominately colonised by Azospirillum spp., most of the isolates being of the species Azospirillum amazonense. Very few Herbaspirilla were isolated from these plants.

Time-averaging period for regulation service

Because electricity is a real-time product, power system operators must adjust generation to match load on a moment-to-moment basis, providing the ancillary service called regulation. But what is meant by moment-to-moment? This article addresses that question by providing background information on the regulation ancillary service and by analyzing short-interval changes in system-level generation and load for four electrical systems. Three systems are large, with peak demands between 10,000 and 20,000 MW, while the fourth system has a peak demand of under 5,000 MW. One of the large systems relies primarily on hydro units for regulation, while the other three systems use fossil units. For each system, the authors obtained 30-second data for 1 or more days on total generation and load. They analyzed these data to see how quickly and with how much lag generation follows load.

In-Stack Condensible Particulate Matter Measurements and Issues

ABSTRACT Particulate matter (PM) emitted from fossil fuel-fired units can be classified as either filterable or condensible PM. Condensible PM typically is not measured because federal and most state regulations do not require sources to do so. To determine the magnitude of condensible PM emissions relative to filterable PM emissions and to better understand condensible PM measurement issues, a review and analysis of actual U.S. Environmental Protection Agency (EPA) Method 202 (for in-stack condensible PM10) and EPA Method 201/201A (for in-stack filterable PM10) results were conducted. Methods 202 and 201/201A results for several coal-burning boilers showed that the condensible PM, on average, comprises approximately three-fourths (76%) of the total PM10 stack emissions. Methods 202 and 201/201A results for oil- and natural gas-fired boilers showed that the condensible PM, on average, comprises 50% of the total PM10 stack emissions. Methods 202 and 201/201A results for oil-, natural gas-, and kerosene-fired combustion turbines showed that the condensible PM, on average, comprises 69% of the total PM10 stack emissions. Based on these limited measurements, condensible PM can make a significant contribution to total PM10 emissions for fossil fuel-fired units. A positive bias (indicating more condensible PM than is actually emitted) may exist in the measured data due to the conversion of dissolved sulfur dioxide to sulfate compounds in the sampling procedure. In addition, these Method 202 results confirm that condensible PM, on average, is composed mostly of inorganic matter, regardless of the type of fuel burned.