Перегляд за Автор "Seminska, N. V."

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  • Ескіз
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    Analysis of the influence parameters on steel strip defects in continuous roll casting-rolling
    (Igor Sikorsky Kyiv Polytechnic Institute, 2023) Nogovitsyn, O. V.; Kholiavik, O. V.; Boris, R. S.; Sokhan, D. V.; Seminska, N. V.
    Problems. The casting-rolling process is currently one of the most effective and promising processes used for the production of steel sheets. The advantages of this process include the small dimensions of the unit and a significant reduction in energy resources. This occurs due to a combination of technological operations and absence of the intermediate heating of the metal. At the same time, there is the challenge of a sustainable industrial process for producing high quality steel sheets. Objective. Companies developing direct melt strip processes using twin-roll crystallizers report a number of challenges they face. Among such problems are defects on the surface of the cast strip. Currently, there is no generally accepted classification of surface defects, such as surface cracks, wrinkles, namely, depressions, and transverse deformation bands. At the moment, there is also no justification for the reasons for the appearance of surface defects during the rolling process. Methods. Based on the research results, a hypothesis was proposed about the causes of defects on the surface of the cast strip and ways to prevent them. During the operation of two-roll crystallizers, a combination of metal hardening processes and its subsequent plastic deformation occurs. The metal moves sequentially through areas of crystallization and deformation. During the research, the authors calculated the process of roll casting-rolling. Conclusions. Based on the research results, we believe that when casting steel using twin-roll casting-rolling, it is necessary to reduce the compression to a minimum value. This recommendation will ensure welding of defects on the surface. The use of this proposal will allow the casting process to be carried out at high speed and little force to be applied to squeeze the rolls. We propose to carry out the process of forming a cast strip with the necessary quality parameters at the following stages of rolling.
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    Intensification of the biohydrogen production process
    (Igor Sikorsky Kyiv Polytechnic Institute, 2024) Golub, N. B.; Zubchenko, L. S.; Demianenkо, I. V.; Zhang, Y.; Seminska, N. V.
    Background. In the last decades, humanity has faced the challenge of finding new ways to obtain renewable, environmentally friendly energy carriers. Hydrogen is one of such energy carriers; however, the current methods of its production require fossil fuels and are accompanied by significant CO2 emissions. Consequently, the energy costs needed to obtain hydrogen by electrolysis exceed the amount of energy produced by burning the hydrogen. Simultaneously, the hydrogen yields for alternative ways, such as fermentation, remain low. Objective. The aim of the work is the development of approaches to intensify the biohydrogen obtaining process from agricultural waste. Methods. An increase in hydrogen yield was achieved using specifically grown microorganisms of the Clostridium spp. A combination of the waste fermentation process with the production of hydrogen in a microbial fuel cell (MFC), which was fed with the liquid fraction after fermentation, was employed. Results. The yield of hydrogen depends on the component composition of the raw material. Higher lignin content in the raw material reduces the yield of hydrogen. The addition of Clostridium spp. to the natural consortium in the amount of 10% of the total inoculum led to an increase in hydrogen yield. The combination of two processes – fermentation and hydrogen production in a MFC – increased the yield of hydrogen by 1.7 times, along with a higher degree of organic raw materials utilization. Conclusions. The additional introduction of Clostridium spp. to the hydrogen-producing consortium leads to a 7–10% increase in the yield of hydrogen, depending on the composition of the raw material. The yield of hydrogen obtained in the fermentation process for the substrate containing corn silage is 12 +- 1% higher than for the wheat straw. In general, the combination of the fermentation and hydrogen production in the MFC in a two-stage process leads to an overall increase in the yield of hydrogen by 60 +- 5%.