ЕНЕРГЕТИЧНІ ХАРАКТЕРИСТИКИ ТИРИСТОРНИХ ЕЛЕКТРОПРИВОДІВ ПОСТІЙНОГО СТРУМУ У ДИНАМІЧНОМУ РЕЖИМІ ЇХ РОБОТИ

The paper considers the research of dc thyristor converters in unstable conditions. The estimations weremade on examples of unbroken mill cutter MC-250/150-6 and blooming of joint-stock company ARSELORMITTAL. Authors performed the harmonic analysis of current; calculated the power constituents and loadingasymmetry of converters transformer in the mentioned devices in correspondent modes.Рассмотрена работа тиристорных преобразователей постоянного тока в динамических режимах электроприводов ножниц непрерывного прокатного стана МС-250/150-6 и блюминга ОАОАРСЕЛОР МИТТАЛ. Проведен гармонический анализ тока, рассчитаны составляющие мощности и несимметрия нагрузки трансформаторов преобразователей указанных установок в соответствующих режимах.Розглянута робота тиристорних перетворювачів постійного струму в динамічних режимах електроприводів ножиць неперервного прокатного стану ДС-250/150-6 та блюмінгу ВАТ АРСЕЛОР МІТТАЛ. Проведений гармонічний аналіз струму, розраховані складові потужності та несиметрія навантаження трансформаторів перетворювачів вказаних установок у відповідних режимах

КОМУТАЦІЙНІ ПРОЦЕСИ В СИСТЕМАХ ГРУПОВОГО ЖИВЛЕННЯ І КЕРУВАННЯ ЕНЕРГОЄМНИМИ УСТАНОВКАМИ

The peculiarities of commutative processes creation in systems of group power supply and control ofpower-intensive installations subject to real loads are presented. The mathematical model and the algorithmof commutative distortions calculation constructed on its basis is developed at operation of converterinstallation group on a power line. The commutative calculations of turbomechanisms group and rollingmill mechanisms of «ArselorMittal Krivoy Rog» are given in the paper.Приведены особенности формирования коммутационных процессов в системах группового питания и управления энергоемкими установками с учетом реальных нагрузок. Разработана математическая модель и построенный на ее основе алгоритм расчета комутационных искажений при работе группы преобразовательных устройств на сеть. Приведены примеры расчетаформирования коммутационных режимов группы турбомеханизмов и механизмов прокатногостана ДС-250/150-6 ВАТ «АРСЕЛОРМИТТАЛ КРИВОЙ РОГ»Приведені особливості формування комутаційних процесів в системах групового живлення і керування енергоємними установками з урахуванням реальних навантажень. Створена математична модель та побудований, на її основі, алгоритм розрахунку комутаційних спотворень при роботі групи перетворювальних пристроїв на мережу живлення. Наведені приклади розрахунку формування комутаційних режимів групи турбомеханізмів та механізмів прокатного стану ДС – 250/150 – 6 ВАТ «АРСЕЛОРМІТТАЛ КРИВИЙ РІГ»

Modeling and Forecasting the Removal of Biogenic Elements from Agricultural Lands Depending on the Soil Agrophysical Properties

Introduction. Environmental pollution prevention, including prevention of water bodies, with nutrients (nitrogen and phosphorus) when they are removed from agricultural lands with possible runoff is a topical problem that requires a timely solution. The studies have found that the removal of nutrients is a result of geochemical processes, fertilization, and other factors. In this regard, mathematical modeling of the process of removal of nutrients from agricultural lands and their possible entry into water bodies is an urgent task. Aim of the Study. The study is aimed at modeling and predicting the process of possible removal of nutrients from agricultural lands to water bodies. Materials and Methods. When conducting the study, there were used well-known modeling methods. They are the methods for calculating the removal of nutrients from agricultural objects into water bodies, based on the minimum amount of initial information for predicting the eutrophication of water bodies and agrochemical methods taking into account the structure and size of field and agricultural areas, crop yields, and removal nutrients with the harvest. Results. Based on an analysis of the literature and expert judgment, a list of the most significant indicators influencing the process of nitrogen and phosphorus removal was justified. There have been developed mathematical models to determine and predict the input of nutrients from agricultural lands to water bodies. There have been found significant indicators influencing the amount of input of nutrients, such as the amount of applied fertilizers, the volume of moisture, soil water capacity, field area, depth of cultivation, etc. There is given an example of calculating the amount of input of nutrients into water bodies with a rainfall intensity of 50 mm per hour. Discussion and Conclusion. The essence of the proposed mathematical models comes down to the synthesis of numerous indicators in the complex process of removal of nutrients and their impact on water quality. The proposed mathematical models make it possible to predict the removal of nutrients from agricultural lands and to develop and implement technical and technological solutions to prevent environmental pollution

DISTRIBUTION OF NATURAL RADIONUCLIDES IN ASHES, COLLECTED BY THERMAL POWER PLANTS ELECTROSTATIC PRECIPITATOR

Link for citation: Nazirov R.A., Vede P.Yu., Tarasov I.V., Zhuikov A.V., Sergunicheva E.M., Tolochko O.R. Distribution of natural radionuclides in ashes, collected by thermal power plants electrostatic precipitator. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 7, рр. 177-186. In Rus. Relevance. In the context of the global trend towards sustainable development, there is a problem of utilization of ash and slag waste from thermal power plants. The use of these wastes in the construction industry is of particular importance, due to the resource intensity of the production of building materials. Fly ash in the building materials composition can influence to a large extent the natural radioactivity of structures and increase the background radiation in the buildings. This is due to the fact that when coal combusting, fly ash is enriched with natural radionuclides. Purpose: to study the radioactivity of fly ash deposited on various fields of the electrostatic precipitator. Object: fly ash deposited on the fields of electrostatic precipitators from the combustion of Kansk-Achinsk brown coal in power boilers BKZ-420-140 PT-2. Methods. Content of Ra-226, Th-232 and K-40 was determined by gamma-spectrometric method, the value of the normalized indicator of specific effective activity for fly ash was calculated. The granulometric composition of the studied samples was determined by the method of laser diffraction analysis. Cluster analysis was used for statistical processing of test results. Results. The presence of two clusters in the content of natural radionuclides was established. In the first cluster, which has high radioactivity, the first and second fields of UGZ-4 electrostatic precipitators are combined, and in the second – the third and fourth fields. A correlation dependence was established between the numbers of fields of electrostatic precipitators, the size of ash particles, the content of Ra-226 and specific effective activity was established. No such dependence was found for Th-232. Conclusions. Particle distribution in the fields of electrostatic precipitators is multimodal. The nature of the distribution of each mode approaches the lognormal law. The content of radium and the value of the specific effective activity depend on the size of ash particles and are described by an exponential function. The highest content of Ra-226 is observed in the ashes deposited on the third and fourth fields of electrostatic precipitators, which indicates the enrichment of finer ash particles with this radionuclide. The conclusions obtained correspond to the well-known thesis about the increased radioactivity of ash particles that are not deposited by ash collection systems and enter the atmosphere together with flue gases. The proposed method for studying the distribution of natural radionuclides over the fields of electrostatic precipitators can be used to predict the radioactivity of particles that are not captured by the flue gas cleaning system and released into the environment

Electrospun magnetic composite poly-3-hydroxybutyrate/magnetite scaffolds for biomedical applications: composition, structure, magnetic properties, and biological performance

Magnetically responsive composite polymer scaffolds have good potential for a variety of biomedical applications. In this work, electrospun composite scaffolds made of polyhydroxybutyrate (PHB) and magnetite (Fe3O4) particles (MPs) were studied before and after degradation in either PBS or a lipase solution. MPs of different sizes with high saturation magnetization were synthesized by the coprecipitation method followed by coating with citric acid (CA). Nanosized MPs were prone to magnetite-maghemite phase transformation during scaffold fabrication, as revealed by Raman spectroscopy; however, for CA-functionalized nanoparticles, the main phase was found to be magnetite, with some traces of maghemite. Submicron MPs were resistant to the magnetite-maghemite phase transformation. MPs did not significantly affect the morphology and diameter of PHB fibers. The scaffolds containing CA-coated MPs lost 0.3 or 0.2% of mass in the lipase solution and PBS, respectively, whereas scaffolds doped with unmodified MPs showed no mass changes after 1 month of incubation in either medium. In all electrospun scaffolds, no alterations of the fiber morphology were observed. Possible mechanisms of the crystalline-lamellar-structure changes in hybrid PHB/Fe3O4 scaffolds during hydrolytic and enzymatic degradation are proposed. It was revealed that particle size and particle surface functionalization affect the mechanical properties of the hybrid scaffolds. The addition of unmodified MPs increased scaffolds' ultimate strength but reduced elongation at break after the biodegradation, whereas simultaneous increases in both parameters were observed for composite scaffolds doped with CA-coated MPs. The highest saturation magnetization-higher than that published in the literature-was registered for composite PHB scaffolds doped with submicron MPs. All PHB scaffolds proved to be biocompatible, and the ones doped with nanosized MPs yielded faster proliferation of rat mesenchymal stem cells. In addition, all electrospun scaffolds were able to support angiogenesis in vivo at 30 days after implantation in Wistar rats

Dry Residues of Sewage – a Promising Energy Fuel

По профилям кривых дифференциальной сканирующей калориметрии была определена максимальная интенсивность теплового потока, а также эндотермические и экзотермические эффекты горения остатков сточных вод (ОСВ). Иловые остатки сточных вод имеют высокую зольность (более 50 %), что снижает значение низшей теплоты сгорания в рабочем состоянии. Высокое содержание летучих веществ (более 80 %) обеспечивает раннее зажигание при температуре 268 °C. Имея низкую температуру зажигания, они могут быть перспективным добавочным топливом к углю после обогащения с целью существенного снижения зольности и увеличения теплоты сгорания. Низкое значение индекса горения, равное 0,4×10–6, обусловлено низким значением максимальной скорости реакции, равной 13 %/мин, и высокой температурой выгорания, равной 633 °C. Проведенные исследования показали, что сжигание ОСВ не приводит к ухудшению условий эксплуатации топочных экранов в топках котлов из-за высокого содержания минералов в золе с высокой температурой плавления (фосфаты железа и кальция). Высокое содержание фосфора в остатках сточных вод способствует иммобилизации подвижного железа в фосфаты. Такой состав ОСВ будет способствовать уменьшению мобильности тяжелых металлов в шлаковых и зольных остатках совместного сжигания с углями при последующем долговременном хранении. Результаты данного исследования целесообразно использовать при проектировании объектов теплоэнергетикиFrom the profiles of the curves of differential scanning calorimetry, the maximum intensity of the heat flux, as well as the endothermic and exothermic effects of the combustion of wastewater residues (SWS) were determined. Sludge wastewater residues have a high ash content (more than 50 %), which reduces the value of the lower calorific value in the working state. The high content of volatile substances (more than 80 %) ensures early ignition at a temperature of 268 °C. Having a low ignition temperature, they can be a promising additional fuel to coal after enrichment in order to significantly reduce the ash content and increase the calorific value. The low value of the combustion index equal to 0.4×10–6 is due to the low value of the maximum reaction rate equal to 13 %/min and the high burnout temperature equal to 633 °C. The conducted studies have shown that the combustion of WWS does not lead to a deterioration in the operating conditions of the furnace screens in boiler furnaces due to the high content of minerals in the ash with a high melting point (iron and calcium phosphates). The high content of phosphorus in wastewater residues contributes to the immobilization of mobile iron into phosphates. Such a composition of WWS will help to reduce the mobility of heavy metals in slag and ash residues of co-combustion with coal during subsequent long-term storage. The results of this study should be used in the design of thermal power facilitie

ЕНЕРГЕТИЧНІ ХАРАКТЕРИСТИКИ ТИРИСТОРНИХ ЕЛЕКТРОПРИВОДІВ ПОСТІЙНОГО СТРУМУ У ДИНАМІЧНОМУ РЕЖИМІ ЇХ РОБОТИ

Розглянута робота тиристорних перетворювачів постійного струму в динамічних режимах електроприводів ножиць неперервного прокатного стану ДС-250/150-6 та блюмінгу ВАТ АРСЕЛОР МІТТАЛ. Проведений гармонічний аналіз струму, розраховані складові потужності та несиметрія навантаження трансформаторів перетворювачів вказаних установок у відповідних режимах

ЕНЕРГЕТИЧНІ ХАРАКТЕРИСТИКИ ТИРИСТОРНИХ ЕЛЕКТРОПРИВОДІВ ПОСТІЙНОГО СТРУМУ У ДИНАМІЧНОМУ РЕЖИМІ ЇХ РОБОТИ

The paper considers the research of dc thyristor converters in unstable conditions. The estimations weremade on examples of unbroken mill cutter MC-250/150-6 and blooming of joint-stock company ARSELORMITTAL. Authors performed the harmonic analysis of current; calculated the power constituents and loadingasymmetry of converters transformer in the mentioned devices in correspondent modes.Рассмотрена работа тиристорных преобразователей постоянного тока в динамических режимах электроприводов ножниц непрерывного прокатного стана МС-250/150-6 и блюминга ОАОАРСЕЛОР МИТТАЛ. Проведен гармонический анализ тока, рассчитаны составляющие мощности и несимметрия нагрузки трансформаторов преобразователей указанных установок в соответствующих режимах.Розглянута робота тиристорних перетворювачів постійного струму в динамічних режимах електроприводів ножиць неперервного прокатного стану ДС-250/150-6 та блюмінгу ВАТ АРСЕЛОР МІТТАЛ. Проведений гармонічний аналіз струму, розраховані складові потужності та несиметрія навантаження трансформаторів перетворювачів вказаних установок у відповідних режимах

Electron Transfer and Modification of Oligosilanylsilatranes and Related Derivatives

International audienceSeveral silatranyl -substituted oligosilanes were prepared starting from bis(trimethylsilyl)silatranylsilanide. Electrochemical and theoretical investigations of some oligosilanes revealed that electrooxidation occurs by formation of a short-lived cation radical. This species undergoes structural relaxation to form a pair of conformers, with endo and exo relationships with respect to the Si-N interaction. Reaction of a 1,4-disilatranyl-1,4-disilanide with 1,2-dichlorotetramethyldisilane gave a mixture of cis and trans diastereomers of a cyclohexasilane with the trans isomer showing a diminished Si-N distance