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•Several factors have a synergistic effect on investigated anthropogenic emissions.•Slurries with low S and N content can reduce NOx and SO2 by 80% vs. coal combustion.•Reactions of ...nitrogen and sulfur reduction occur in temperature interval 800–900 °C.•Sulfur turns to ash at the reaction of metals in biomass with sulfur oxides.•Water concentration increasing in slurries reduces activity of NOx and SO2.
The paper presents the results of the experimental research performed for a comparative analysis of factors that influence the concentrations of the main gaseous anthropogenic emissions from coal and waste-based slurry fuel combustion. We focus on controlling the NOx and SO2 concentrations. We have researched for the first time a group of mechanisms and factors, influencing the formation of anthropogenic emissions from burning waste as part of wet multi-component slurry fuels. The experiments were conducted with coals of different grades, coal processing waste, water-containing slurries, as well as extra additives of biomass and waste. We show how much the NOx and SO2 concentrations are affected by a wide group of factors and processes: temperature in the chamber, vaporization, initial content of sulfur and nitrogen in the fuel mixture, specialized additives with different concentrations and in different combinations, as well as specific chemical reactions in a limited range of temperatures. The experimental results show that the initial content of nitrogen in the slurry and the catalytic processes of nitrogen oxide reduction to free N2 have a dominant influence on NOx emissions due to free hydrogen radicals and interaction of additives with the components (e.g., with Fe2O3). SO2 concentrations are decisively influenced by the content of sulfur in the slurry, as well as the chemical interactions of amphoteric and active metals with sulfur oxides. Combined employment of a group of factors under study can provide a reduction of NOx and SO2 by up to 80% as compared to coal combustion conditions.
•Emissions were normalized relative to the fuel mass, time, energy, maximum concentrations.•Combustion of the slurry derived from oil sludge with water reduces the emissions.•Oil sludge without ...additives has the highest emission mass factors.•SO2 and NO emission normalized relative to thermal energy are minimal for oil sludge with water.•The most promising fuel from those considered is the slurry of oil sludge with water.
The use of traditional energy carriers results in large amounts of waste, of petroleum origin, in particular. Such waste is highly hazardous when stored in open waste piles or discharged into the soil. It is, therefore, rational to combust it as part of fuel compositions with specialized additives. These additives are utilized to solve specific environmental, energy, social and other tasks. Emission factors were calculated, corresponding to gas emissions, relative to: (i) mass of the fuel to be burned; (ii) maximum/average emissions released into the atmosphere per time; (iii) thermal energy released from combustion; (iv) specific mass emissions of a pollutant per tonne of oil equivalent (toe). The conducted research indicated that the combustion of a slurry derived from oil sludge and water was characterized by the lowest absolute concentrations of carbon, nitrogen and sulfur oxides, which were 7–30%, 9–21% and 41–63% lower, respectively, than those of oil sludge without water. From the considered fuels, the most promising ones by specific normalized factors of SO2 and NO emission were slurries derived from oil sludge and water, but emission factors of CO2 were lower for oil sludge without additives. The information obtained in this study makes it possible to assess the emission characteristics of fuel combustion, taking into account a combination of factors (combustion temperature, fuel mass, etc.), and also makes it possible to compare the results with other studies. Research results show great prospects of using oil sludge as part of composite liquid fuels at power plants.
The economy of the Russian Federation is aimed at developing a fuel and energy complex that uses environmentally friendly energy, which corresponds to the global trend of reducing emissions of ...harmful substances into the atmosphere during the production of various types of products. Decarbonization is one of the biggest challenges of modern society. To solve this problem, renewable energy sources are being actively introduced, as well as various types of fuel, the combustion of which produces a minimum content of emissions. Among them, we can highlight the fuel that has the greatest prospects; this is hydrogen, a fuel with the highest energy content, reaching a value of 120 MJ/kg. Unlike renewable energy sources, the practice of which in a number of countries has caused a crisis in the reliability of the energy system, hydrogen technologies make it possible to achieve the task of decarbonization with minimal impact on the environment at all stages: production, transportation, combustion, without compromising reliability. The main problems of mass introduction of hydrogen technologies are the difficulty in obtaining, transporting and storing hydrogen fuel. Following the signing of hydrogen strategies, most developed countries are considering using hydrogen as a vehicle fuel. Hydrogen transport, unlike electric transport, is not limited by range, but the high cost of hydrogen transport and the lack of refueling infrastructure hinder the development of this type of technology. Currently, the most common fuel cell system is FCV (fuel cell vehicle).
The article presents the concept of hydrogen refueling, taking into account different technologies for the production of hydrogen fuel. Hydrogen must be stored at a filling station at a pressure of 300–800 bar, in a gaseous or liquid state. An analysis of the cost of construction and subsequent operation of hydrogen filling stations revealed criteria for the economic efficiency of their implementation depending on the amount of fuel consumed and storage methods.
Metamaterials are of great interest due to their unusual properties and promising practical application. The paper studies a mechanical metamaterial bar composed of 81 unit cells. The unit cell is ...shaped to a cube the faces of which consist of two-dimensional tetrachiral elements. The elastic deformation of a metamaterial specimen is numerically modeled in uniaxial loading. How the twist angle and Young modulus of the metamaterial specimen depend on the parameters of the chiral structure is demonstrated. Value ranges of the parameters in which the twist angle is largely affected are found. Cell parameters that have the greatest and least influence on the metamaterial twist angle and Young's modulus are determined. The effective Young's modulus decreases by a factor of approx. 20 when changing the inner radius of the ring. An almost constant effective Young's modulus is found.
In the Russian Federation, the construction of individual housing construction projects is being carried out at an increasing pace, for the construction of electrical networks for which there are no ...regulatory documents with an adequate methodology for calculating electrical loads. This situation led to low load on power grid equipment, and accordingly, investments became non-refundable. Sustainable development of private and industrial construction of individual housing projects is possible only with the development of regulatory technical documents that meet modern trends. To accomplish this task, research work was carried out to develop regulatory documents used in the design of electrical networks in cottage villages, taking into account the different number of floors and area of individual housing construction projects. Using the example of two cottage villages in Kazan, based on the parameter of daily and monthly electricity consumption, it was possible to obtain a sample whose data obeys the law of normal distribution. The analysis of sample sets of cottages in the villages shows that according to the power consumption parameter they can be grouped depending on the number of floors and area of the houses. The results obtained make it possible to formulate a future methodology for calculating electrical loads with amendments to the Federal Code of Rules.
Over the past few years, much attention has been paid to hydrogen energy. The development of hydrogen technologies leads to a reduction in the cost of both the hydrogen fuel itself and hydrogen ...systems, which leads to a wider use of this type of fuel in various branches of the fuel and energy complex.
At the moment, the primary task is to increase the efficiency of combined cycle power units, reduce wear and tear of equipment during peak electricity consumption, reliable backup of energy supply, and reduce harmful emissions during the generation of heat and electricity. One of the modern methods for implementing these challenges is the use of energy storage devices. A new solution to this problem can be the introduction of hydrogen storage in the cycle of a thermal power plant.
The article considers the modernization of a combined-cycle power unit with a gas turbine PG6111FA manufactured by « General Electric» with a rated power of 80 MW, a waste heat steam boiler manufactured by JSC « EnergoMashinostroitelny Alliance», and a steam turbine KT-33/36–7.5/0.12. During periods of night unloading, the effective efficiency of the power unit drops, so it is necessary not to unload the equipment, but to turn on the electrolyzers for the production of hydrogen fuel for further use in hydrogen fuel cells. The operating time of the hydrogen system with an electrolyzer is not limited in time, the operation of the electrolyzer takes place during night unloading periods (from 4 to 7 h a day), while the hydrogen storage works constantly, in this mode of operation, the service life is about 15 years, for stable operation it is necessary hydrogen fuel and periodic maintenance. An important component of the hydrogen system is a hydrogen battery with minimal storage losses, in contrast to traditionally installed thermal storage. Studies of the use of hydrogen storage in the circuits of thermal power plants have shown their effectiveness, including their implementation allows you to increase the efficiency, reduce the cost of own needs of the power plant, reduce emissions in the production of electricity, a leveled load schedule allows you to increase the life of the gas turbine, as the turbine works in basic mode. The use of accumulators in thermal power plants increases the competitiveness among traditional energy generation systems.
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Geostationary orbit transfers of a spacecraft with low-thrust electric propulsion systems (EPSs) that use the energy of solar batteries are considered. The influence of such disturbing factors as ...the gravitational effect of the Sun and Moon, geopotential variations, and switching off of the EPS thrust when the spacecraft enters the Earth’s shadow is investigated. The influence of all factors jointly and each of the factors separately is analyzed. In each case, to minimize the working substance expenditures for a transfer, the two-point boundary value problem is formulated and solved on the basis of the Pontryagin’s maximum. Only in the case of thrust switching off in the area of the shadow is the so-called “incomplete” boundary value problem solved. This solution does not take into account the conditions for optimal crossing the shadow boundaries. Although the transfers are nonoptimal in this case, it becomes possible by choosing the problem parameters to obtain good (in terms of expenditures) solutions. Here, the criterion is a comparison with the nominal trajectories—the optimal transfers in the central Newtonian field of the Earth without the thrust switching off and without taking the gravitational effect of the Sun and Moon into account. The results of calculations for several nominal trajectories, which differ in transfer duration, in the number of revolutions, and in other parameters, are presented.
The growth in demand for the production of heat and electricity requires an increase in fuel consumption by power equipment. At the moment, the most demanded thermal equipment for construction and ...modernization is gas turbine units. Gas turbines can burn a variety of fuels (natural gas, synthesis gas, methane), but the main fuel is natural gas of various compositions. The use of alternative fuels makes it possible to reduce CO2 and NOx emissions during the operation of a gas turbine. Under conditions of operation of thermal power plants at the wholesale power market, it becomes probable that combined cycle power units, designed to carry base load, will start to operate in variable modes. Variable operation modes lead to a decrease in the efficiency of power equipment. One way to minimize or eliminate equipment unloading is to install an electrolysis unit to produce hydrogen.
In this article the technology of “Power to gas” production with the necessary pressure at the outlet of 30 kgf/cm2 (this pressure is necessary for stable operation of the fuel preparation system of the gas turbine) is considered. High cost of hydrogen fuel during production affects the final cost of heat and electric energy, therefore it is necessary to burn hydrogen in mixture with natural gas. Burning a mixture of 5% hydrogen fuel and 95% natural gas requires minimal changes in the design of the gas turbine, it is necessary to supplement the fuel preparation system (install a cleaning system, compression for hydrogen fuel). In addition, the produced hydrogen can be stored, transported to the consumer. For the possibility of combustion of a mixture of natural gas and hydrogen fuel in a gas turbine the methodology of calculation of thermodynamic properties of working bodies developed by a team of authors under the guidance of Academician RAS (the Russian Academy of Sciences) V.E. Alemasov has been adapted, resulting in a program that allows to obtain an adequate mathematical model of the gas turbine. The permissible range of the working body temperature is limited to 3000 K. This paper presents the developed all-mode mathematical model of a gas turbine.
On the basis of mathematical modeling of a gas turbine, a change in the main energy and environmental characteristics is shown depending on the composition of the fuel gas. Adding 5% hydrogen to natural gas has little effect on the gas turbine air treatment system, the flow rate remains virtually unchanged. CO2 emissions decrease, but there is an increase in the amount of H2O in the turbine exhaust gases.
In this article, we consider cross-validation of the quantitative structure-property relationship models for reactions and show that the conventional k-fold cross-validation (CV) procedure gives an ...'optimistically' biased assessment of prediction performance. To address this issue, we suggest two strategies of model cross-validation, 'transformation-out' CV, and 'solvent-out' CV. Unlike the conventional k-fold cross-validation approach that does not consider the nature of objects, the proposed procedures provide an unbiased estimation of the predictive performance of the models for novel types of structural transformations in chemical reactions and reactions going under new conditions. Both the suggested strategies have been applied to predict the rate constants of bimolecular elimination and nucleophilic substitution reactions, and Diels-Alder cycloaddition. All suggested cross-validation methodologies and tutorial are implemented in the open-source software package CIMtools (
https://github.com/cimm-kzn/CIMtools
).
Transfers in the central Newtonian field are considered under the assumption that low thrust that is constant in magnitude is zeroed when spacecraft with solar batteries enters the Earth’s shadow. ...Using the maximum principle, the two-point boundary-value problem is formed, in which, however, the conditions for optimal intersection of the shadow boundaries are not considered, which significantly complicates the problem. For this reason, the boundary-value problem is found to be “incomplete” and its solutions are not optimal. Nevertheless, for transfers to a geostationary orbit from highly elliptical orbits, it allows one to obtain “good” trajectories with working substance costs less than those on trajectories without zeroing the thrust, or slightly exceeding them. This is shown by the example of transfers from the initial orbit with an inclination of 13° and with a distance at the perigee of
≈
15.6 Mm and at the apogee of
≈
83.2 Mm.
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