Opazovanje in simulacija nestabilnih pogojev med kontinuirnim litjem

Continuous casting comprises thermal, mechanical and chemical processes running in a complex system that contains a number of elements, such as a solidifying steel strand, a mould with an oscillation mechanism, a withdrawal mechanism, a water cooling sub-system with nozzles, several control sub-systems, etc. An external observer might see the process as robust and stable, but in reality there are fluctuations in the internal thermal and mechanical quantities, reflected in the structure and quality of the product. The research on unsteady behaviour of the quantities such as a solidifying strand temperature field, solid shell thickness and metallurgical length was conducted using an industrial diagnostic system DGS complemented with special measurement equipment and a thermal numerical model. Selected results of the monitoring and simulation of the non-standard process states are shown and analysed in the paper. Methods for determining the boundary conditions for the numerical model are also presented. The effect of the Leidenfrost phenomenon on the heat-transfer coefficient during water cooling by nozzles is also discussed. Since the determination of precise and immediate boundary conditions has technical limits, the model provides only smoothed values in time and space. As knowledge of the instantaneous state of the fluctuating process is a prerequisite for achieving quality and defect-free production, it is appropriate to complement the thermal numerical model by on-line monitoring of the machine's internal state. The results of the simulations are closely linked to the real process data.Kontinuirno litje obsega termične, mehanske in kemične procese, ki tečejo v kompleksnem sistemu, ki vsebuje vrsto elementov, kot so: strjujoča se jeklena žila (gredica), kokila z oscilacijskim mehanizmom, izvlečni mehanizem, vodno hlajenje s podsistemom hladilnih šob, več kontrolnih podsistemov itd. Zunanji opazovalec lahko vidi proces kot robusten in stabilen, toda v resnici imamo vrsto fluktuacij (nihanj) internih termičnih in mehanskih veličin in kakovosti produkta (nastajajoče konti lite gredice). Raziskave (časovno) nestabilnega obnašanja veličin, kot so: temperaturno polje strjujoče se konti gredice, debelina trdne skorje in metalurška dolžina, so avtorji prispevka izvajali z industrijskim diagnostičnim sistemom (DGS), dopolnjenim s specialno merilno opremo in termičnim numeričnim modelom. V članku avtorji predstavljajo izbrane rezultate analiz, opazovanja in simulacije nestandardni procesnih stanj. Prav tako predstavljajo metode določevanja robnih pogojev za numerični model. Diskusija obsega tudi t.i. Leidenfrostov fenomen in njegov vpliv na koeficient prenosa toplote med vodnim hlajenjem s šobami. Za natančno določitev vsakokratnih robnih pogojev obstajajo tehnične omejitve. Zato so v postavljenem modelu uporabljene le zglajene vrednosti v realnem času in prostoru. Poznavanje trenutnega stanja ves čas spreminjajočega stanja, je predpogoj za doseganje kvalitetne proizvodnje brez napak. Zato je primerno uporabljati termični numerični model s tekočim (on-line) oz. neposrednim spremljanjem internega stanja na konti livni napravi. Predstavljeni rezultati so tesno povezani z realnimi procesnimi podatki.Web of Science52211711

Analysis of the causes and impact of the financial crisis in the management of Komerční banky, a.s.

Import 29/09/2010Resumé: Ekonomika na celém světě je silně ovlivněna finanční krizí, která začala v roce 2007 kvůli problémům na hypotečním trhu v USA. Globalizace světa je důvodem, proč ekonomiky mnoha zemí byly také zasaženy finanční krizí. Mnoho ekonomických odvětví se zhoršilo důsledkem finanční krize. Diplomová práce analyzuje příčiny a dopad finanční krize na hospodaření Komerční banky, a.s.. Je složena ze čtyř hlavních kapitol. Druhá kapitola zahrnuje mnoho teoretických informací popisujících finanční krizi a její negativní vliv na USA, Evropu a Českou republiku. Tato kapitola rovněž podrobně vysvětluje příčiny a typy finančních krizí. Kromě toho líčí události, které se staly po vzniku finanční krize. Třetí kapitola se zabývá finančními údaji Komerční banky, a.s. a ukazateli obezřetného chování bank. Finanční výsledky získané ze zkoumaných dat ovlivňují finanční stabilitu Komerční banky, a.s.. Čtvrtou kapitolu lze považovat za praktickou a ověřuje platnost teoretických předpokladů. Ekonomická data jsou analyzována v programu SPSS, který umožňuje finanční a statistické testování dat včetně vytváření grafů a modelů. Pátá a zároveň závěrečná kapitola shrnuje finanční zdraví Komerční banky, a.s. na základě předchozích výsledků. Tato kapitola podrobně vysvětluje ekonomické ukazatele a jejich vliv na hospodaření Komerční banky, a.s. v daném časovém období. Na základě této kapitoly lze vytvořit závěr ohledně finanční stability Komerční banky, a.s. v období finanční krize.Summary: The economy around the world is strongly influenced by the financial crises that started in a year of 2007 because of the problems on the mortgage market in the USA. Globalization of the world is the reason that the economies of many countries in the world were also hit by the financial crisis. Many economic sectors got worse because of the effects of the financial crisis. The thesis analyses the causes and the effects of the financial crises in the management of Komerční banky, a.s.. It is consisted of four main chapters. The second chapter involves much theoretical information that describes the financial crisis and its negative influence on the USA, Europe and the Czech Republic. This chapter also explains in detail the causes and types of financial crises. Furthermore, it depicts the events that happened after the beginning of the financial crisis. The third chapter deals with the financial data of Komerční banky, a.s. and the indicators of the prudent behavior of the banks. Financial results obtained from the explored data have impact on management and financial stability of Komerční banky, a.s.. The fourth chapter can be considered as practical one and verifies the validity of theoretical assumptions. Economic data are analyzed in SPSS program that enables financial and statistical testing of the data including the creation of the graphs and models. The fifth and also ending chapter summarizes the financial health of Komerční banky, a.s. based on the previous results. This chapter narrowly interprets the economic indicators and their impact on the management of Komerční banky, a.s. at the given period of time. Based on the this chapter, it could be made the conclusion about the financial stability of Komerční banky, a.s. in the period of the financial crisis.154 - Katedra financívelmi dobř

Experience with application of reagent to heat transfer surfaces of combustion device

The formation of deposits on heat exchange surfaces of combustion equipment causes a decrease in heat exchange, a decrease in power, and consequently deterioration in the economic balance of combustion equipment. The technology of French company A. I. T. DRIVEX has been developing and being applied in practice for many decades. Preventive technology is used as a mean reagent periodically injected during operation into the combustion chamber. Part of the application is always pre-prepared project resolving the location of the injection nozzles into the combustion chamber on the flue gas path. The article describes the experimental usage of reagent GEPERSUITE 2200 at the Sermaize refinery in France. The aim of the test is to evaluate the benefits and advantages of applied technology in the boiler refinery in full operation. The results clearly demonstrate that using the reagent GEPERSUITE 2200 is advantageous in terms of economic and technical propertiesWeb of Science1925

Measurement the thermal profile of steelmaking ladle with subsequent evaluation the reasons of lining damage

Based on the operational measurement, of which content was to determine ladle thermal profile, there were analysed causes of possible damage of lining in steel ladles by steel breakout through the ladle shell. There exists connection between thermal state of ladle lining during the operation and its lifetime. There were reached to the conclusion that the cause of failure in the lining of ladle is except for high temperature of bath, also wide interval of temperature change during the tap operation, in consequence with possible insufficient pre-heating of ladle, discontinuous operation of aggregate and damage of insulating lining layer, respectively deformation of ladles shell.Web of Science61128227

Research of thermal processes for the continuous casting of steel

The article deals with the determination of the basic indicators of heat transfer in the continuous casting of steel, which can be described as an unsteady process with complicated boundary conditions for the solution. An analytical solution of this problem is practically impossible and, therefore, mathematical modelling is applied with a certain simplification of the real conditions and with a description of those criteria that influence the most the process of solidification and cooling. Using a simulation program and the knowledge of input parameters, it was possible to predict the distribution of the thermal field of a continuously cast blank in the course of its casting. Simulations also allowed us to deal with the issues of the inner structure, surface quality, mechanical properties of a continuously cast blank, metallurgical length, change in the thickness of a strand shell and overheating of steel. Some results obtained with numerical simulations are documented for concrete examples.Web of Science47681881

Comparison of Chemical Composition and Colour Parameters of Different Mentha Genus Plants Grown under Organic Conditions

Mentha species are one of the world oldest and popular herbs, that are used in cosmetic and food industry, as well as tea for their medical properties. Due the consumer perception of ecological production and aromatic plants production waste utilization the objective of this work was to determine differences in chemical content and colour among different varieties and parts of Mentha plants ecologically grown in Lithuania. In mint leaves there were determined: content of essential oils, dry matter, soluble solids, ascorbic acid, crude fibre, crude ash, photosynthetic pigments and colour CIE L*a*b* parameters. In the case of mint plants stems, the same analyses were performed except ascorbic acid, soluble solids and colour. The highest content of essential oils were found in Mentha spicata L. ‘Moroccan’ and Mentha piperita L. ‘Glacialis’ leaves, while the least in Mentha suaveolens Ehrh. ‘Variegata’. The content of essential oils in the stems was minor and did not depend on mint variety. Plant parts differ significantly in respect of chemical composition. Amount of dry matter in mint leaves and stems was very similar, while crude ash in the leaves was twice higher than in the stems. Content of crude fibre in the leaves did not differ significantly in all investigated varieties and was 3.6 times lower comparing with the stems. Average ratio of chlorophyll a to b in the leaves was equal to 2.78, while in stems equal to 2.83. The lightest was Mentha suaveolens ‘Variegata’, the darkest Mentha spicata L. ‘Moroccan’ and the greenest Mentha piperita L. ‘Swiss’ leaves. Mints and their parts differ in chemical content and can have widespread usage not only for production of high-value natural products but in addition as alternative fibrous biomass plants

Use of numerical methods for the design of thermal protection of an RFID-based contactless identification system of ladles

A method of contactless identification is proposed for steel ladles to eliminate manual inputs that negatively affect the monitoring system of ladles. It is an RFID (Radio Frequency Identification) method based on the principle of radio data transmission between the sensor and a moving object (in our case, a ladle), which is equipped with a so-called transponder (RFID tag). The RFID tag was part of the ladle; it was placed on its shell, reaching a temperature often exceeding 250 degrees C. The temperature limit for using an RFID transponder is 120 degrees C. For this reason, thermal insulation protection was made for the RFID transponder. Its design was preceded by simulations of temperature fields using numerical methods. The aim was to compare the resulting values obtained from numerical simulations with the actually measured temperatures and, on this basis, to subsequently perform a numerical simulation for conditions that are not operationally measurable.Web of Science127art. no. 116

The corrosion effect of fly ash from biomass combustion on andalusite refractory materials

The main problem affecting the life of refractory linings in furnaces is alkaline corrosion formed during biomass combustion, especially in systems with SiO2–Al2O3 . This corrosion effect is very intensive compared to using conventional technologies designed for burning traditional fuels. This study focuses on the development of a new type of andalusite refractory material with a higher corrosion resistance to K2CO3 and fly ash after biomass combustion. The original andalusite refractory material is labeled A60PT0, with an oxide content of 60 wt.% Al2O3 and 37 wt.% SiO2 , a compressive strength parameter of 64 MPa, and an apparent porosity of 15%. In the experiment, four mixtures (labeled A60PT1–A60PT4) were modified primarily using the raw materials and granulometry. The fly ash was characterized by an X-ray diffraction analysis with the following phases: quartz, calcite, microcline, leucite, portlandite, and hematite. According to the X-ray fluorescence analysis, the samples contained the following oxides: 47 wt.% CaO, 12 wt.% K2O, 4.6 wt.% SiO2 , 3.5 wt.% MgO, and some minority oxides such as P2O5 , MgO, MnO, and Fe2O3 between 2 and 5 %. The tendency for slagging/fouling of the ash was determined with the help of the indexes B/A, TA, Kt , and Fu. The final material was a shaped andalusite refractory material labeled A60PT4 with a content of 65 wt.% Al2O3 and 36 wt.% SiO2. The properties of the andalusite material were a compressive strength of 106.9 MPa, an apparent porosity of 13%, and the recommended temperature of use up to 1300 ◦C. For corrosion testing, a static crucible test was performed according to the norm CSN CEN/TS 15418 and ˇ the company’s internal regulation. The exposure time of the samples was 2 h and 5 h at temperatures of 1100 ◦C and 1400 ◦C for K2CO3 and ash, respectively. For the evaluation of tested samples, an X-ray powder differential analysis, an X-ray fluorescence analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were used.Web of Science133art. no. 35

Use of neural networks for lifetime analysis of teeming ladles

When describing the behaviour and modelling of real systems, which are characterized by considerable complexity, great difficulty, and often the impossibility of their formal mathematical description, and whose operational monitoring and measurement are difficult, conventional analytical-statistical models run into the limits of their use. The application of these models leads to necessary simplifications, which cause insufficient adequacy of the resulting mathematical description. In such cases, it is appropriate for modelling to use the methods brought by a new scientific discipline-artificial intelligence. Artificial intelligence provides very promising tools for describing and controlling complex systems. The method of neural networks was chosen for the analysis of the lifetime of the teeming ladle. Artificial neural networks are mathematical models that approximate non-linear functions of an arbitrary waveform. The advantage of neural networks is their ability to generalize the dependencies between individual quantities by learning the presented patterns. This property of a neural network is referred to as generalization. Their use is suitable for processing complex problems where the dependencies between individual quantities are not exactly known.Web of Science1522art. no. 823

Corrosive effect of wood ash produced by biomass combustion on refractory materials in a binary Al-Si system

In terms of its chemical composition, biomass is a very complex type of fuel. Its combustion leads to the formation of materials such as alkaline ash and gases, and there is evidence of the corrosive effect this process has on refractory linings, thus shortening the service life of the combustion unit. This frequently encountered process is known as "alkaline oxidative bursting". Corrosion is very complex, and it has not been completely described yet. Alkaline corrosion is the most common cause of furnace-lining degradation in aggregates that burn biomass. This article deals with an experiment investigating the corrosion resistance of 2 types of refractory materials in the Al2O3-SiO2 binary system, for the following compositions: I. (53 wt.% SiO2/42 wt.% Al2O3) and II. (28 wt.% SiO2/46 wt.% Al2O3/12 wt.% SiC). These were exposed to seven types of ash obtained from one biomass combustion company in the Czech Republic. The chemical composition of the ash is a good indicator of the problematic nature of a type of biomass. The ashes were analyzed by X-ray diffraction and X-ray fluorescence. Analysis confirmed that ash composition varies. The experiment also included the calculation of the so-called "slagging/fouling index" (I/C, TA, Sr, B/A, Fu, etc.), which can be used to estimate the probability of slag formation in combustion units. The corrosive effect on refractory materials was evaluated according to the norm CSN P CEN/TS 15418, and a static corrosion test was used to investigate sample corrosion.Web of Science1516art. no. 579