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Abstract

The presented article describes the method for determining one of the trace elements occurring in coalbismuth. The subjects of the analysis were coal type 34, 35 and their fly ashes derived from Jastrzębska Spółka Węglowa. The main reason for the research was the extensive use of bismuth in many industry sectors. Additionally, bismuth is on the list of deficit elements, therefore the possibility of obtaining an alternative for its recycling source of it is needed, is required. The research was carried out using atomic absorption spectrometry with electrothermal atomization in a graphite cuvette. The samples were incinerated at 800°C and microwave mineralization in a high-pressure closed system was performed until the spectrometric analysis was achieved. In order to achieve mineralization, a mixture of HF and HNO3 acids was used to turn the samples into acidic solutions. The preparation of the samples was based on available literature data and own observations. In the experiment, the effects of the additive modifier was modified by changing the temperature in further steps: drying, incineration, cooling, atomization and burning were described. In addition, the palladium modifier was used in order to limit secondary reactions and enable the evaporation of matrix components. The measurement conditions which are presented in this article allow for a linear calibration curve to be established. However, this is not clear and the definitive method for determining the bismuth in coal is carried out through the use of ET-AAS.
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Abstract

A method of suppressing chaotic oscillations in a tubular reactor with mass recycle is discussed. The method involves intervention in the temperature of the input flow by the recirculation flow and the temperature set from the exterior. The most advantageous solution was proved to be heat coupling elimination and maintenance of the reactor input temperature on the set level. Moreover, the reactor modelwas identified on the basis of a chaotic solution, as it provides the biggest entropy of information.
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Abstract

A356 is one of the widely used aluminium casting alloy that has been used in both sand and die casting processes. Large amounts of scrap metal can be generated from the runner systems and feeders. In addition, chips are generated in the machined parts. The surface area with regard to weight of chips is so high that it makes these scraps difficult to melt. Although there are several techniques evolved to remedy this problem, yet the problem lies in the quality of the recycled raw material. Since recycling of these scrap is quite important due to the advantages like energy saving and cost reduction in the final product, in this work, the recycling efficiency and casting quality were investigated. Three types of charges were prepared for casting: %100 primary ingot, %100 scrap aluminium and fifty-fifty scrap aluminium and primary ingot mixture were used. Melt quality was determined by calculating bifilm index by using reduced pressure test. Tensile test samples were produced by casting both from sand and die moulds. Relationship between bifilm index and tensile strength were determined as an indication of correlation of melt quality. It was found that untreated chips decrease the casting quality significantly. Therefore, prior to charging the chips into the furnace for melting, a series of cleaning processes has to be used in order to achieve good quality products.
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