Papers by Keyword: Sulphur

Abstract: Analysis of literature sources and empirical data indicate a variety and a large volume of experimental material, which often characterizes the uncertainty and contradiction of information regarding the effect of sulphur and manganese on the corrosion behaviour of steels obtained using traditional methods. This leads to the need to search for new, alternative methods for its effective analysis. The task of assessing and predicting the corrosion properties of structural steels is a key one in the general problem of managing the operational reliability of welded metal structures and equipment for the chemical, metallurgical, oil and gas, mining and other industries. The possibilities of its solution consist of using new information technologies, a component of which is intelligent means of information processing, such as artificial neural networks (ANN). The use of ANN makes it possible to create qualitatively new hardware and software that significantly expand the classes of emerging problems and increase the efficiency of analysis and forecasting. In the process of long-term operation of metal structures in many industrial industries, the metal is in direct contact with sulfur-containing agents at high temperatures. This leads to the saturation of the surface layer of the metal with sulfur with a concentration of up to 0.6%, which further makes it impossible to carry out repair and welding operations due to the formation of hot cracks. It was found that adding metallic manganese into the electrode coating in an amount of 20-25% significantly increases (4-5 times) the resistance against the formation of hot cracks. Sulfur content in the deposited metal has the opposite effect on the appearance of hot cracks. So, with a sulfur content of 0.042% and more, the resistance of the metal against the formation of hot cracks decreases sharply. It is shown that an increase in the content of metallic manganese in the electrode coating significantly reduces the content of dissolved sulfur in the deposited metal. Moreover, this tendency is typical for steels with different sulfur content in the surface layers and with different service life. For example, for steel with a service life of 20 years, the initial sulfur content in the surface layer of the metal (up to 1 mm) was about 0.52%. Adding metallic manganese in the coating of electrodes in an amount of 20-25% made it possible to reduce the sulfur content in the deposited metal to 0.03-0.045%, i.e. 12.6-17.3 times. In addition, the corrosion rate decreases with an increase in the content of metallic manganese in the electrode coating. The lowest corrosion rate for all steels involved in the research was established at 20-25% manganese content in the coating.

Abstract: The sulfur content present in graphene oxide prepared by Hummers' method has only been addressed by few papers so far. By modified Hammers method we synthesized thermally stable in ambient environment multilayer sulphur-doped graphene oxide. The samples were heat treated in an electrical furnace setup at different ambient temperatures and their crystallite size and linear coefficient of thermal expansion were extracted from Raman band intensity peak ratio as a function of temperature. We found unusually large (in comparison with graphene oxide) contraction on heating of multilayer two weight percent sulphur-doped graphene oxide with carbon to oxygen ratio of 2.3 in a narrow temperature range (308-318 K) with the lowest value of the linear thermal expansion coefficient of -18 ppm 1/K. Based upon an examination of the synthesized sulphur-doped graphene diffractograms, it is suggested that negative thermal expansion stems from the phonon backscattering by the sulphur impurity sites and the edges of the layers. The obtained experimental results have potential practical applications for fabrication of solar cells, sensors, lubricators, thermal actuators and also wavelike (second sound) thermal transport structures.

Abstract: The aim of the research was to investigate the pollution level of sulphur and metallic elements in Riga city (Freeport of Riga, Kundziņsala, Mežaparks) by using foliose lichens (Xanthoria parietina) as a bio-indicators. Obtained results show that the Freeport of Riga is the most polluted area comparing with other neatest places in Riga city, Kundziņsala and Mežaparks. Evaluate a washing effect, obtained results shows that lichen thallus contains about 50 % of total amount of sulphur and investigated elements as dust particles on the surface of lichens.

Abstract: Graphene oxide/sulphur compound was synthesized by Hammers method. The chemical composition, presence/quantity of functional groups, exfoliation level, number of layers, crystallite size of graphene oxide/sulphur were characterized by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy images. The current-voltage characteristics of the samples were measured in air at room temperature. In the I - V characteristic curve of graphene oxide/sulphur compound with the ratio of oxygen to carbon of 3.54 and that to sulphur of 42.54, negative differential resistance was observed. The negative differential resistance is attributed to current carrier transitions between the localized states formed by functional groups.

Abstract: Synthesis of the portland cement clinker in the presence of a significant amount of SO₃ is difficult, due to the tri-calcium silicate formation suppression. Since some technogenic formations contain a significant amount of SO_3, it is hard to obtain the portland cement clinker from it. The analysis of the SO₃ influence on the clinker-formation thermodynamic process allowed to reveal a number of regularities of their occurrence and to propose a method for the raw mix composition calculating and its preparation, to ensure a stable portland cement clinker synthesis.

Abstract: Literature reported extensive work on the failure of Industrial power transmission systems, during their routine torque transmission, rotary motion etc. During transmission through gear drive the noise, temperature, stresses, vibration etc are important factors to be considered. When one or more of above exceed certain design limits, the drive and its accessories must be examined for the cause and a preventive maintenance is to be followed. The latest research work carried out, in above area is reviewed. The cause of failure and failure analysis is examined. An attempt is made in this paper, to systematically analyze the modes of failures, the reasons for the same, issues and challenges involved, there in, and measures to be taken for addressing them. This analysis is likely to help the researchers to proceed further in analyzing the failure and to suggest means to prevent failure of gear power transmission systems. The major contribution of present work is, to present the common modes of failure of gear teeth in power transmission systems, and measures to be taken to address the same. In general various additives in the lubricating oil help in controlling initiation of pitting. The present work involves controlling one of the additives namely sulphur in the lubricating oil to control pitting. The present work forms an excellent basis for identifying various other parameters affecting the pitting failure of gear teeth in a gear box.

Abstract: Quality of machine production is very close-knit with quality of metallurgical semi-products and with improvement their working properties. It can be achieved first of all by decrease of sulphur and non-metallic inclusions content in metal. Improvement of working properties provide remelted processes above an electro slag remelting (ESR). The slags play very important role by ESR process. By experiments steel with next chemical composition was used: C (0,9 – 1,1%), Mn (0,30 – 0,50%), Si (0,15 – 0,35%), Cr (1,30 – 1,65%), Ni (max.0,30%), Cu (max.0,25%), P (max.0,027%), S (max.0,030%). The steel was remelted under 8 types of slags on the base of CaO, Al₂O₃, CaF₂ and SiO₂ in different ratios. The contribution deals with influence of chemical composition of slag on mechanical properties and cleannes of metal after electro slag remelting. Variation of slag chemical composition enables to change chemical composition of remelted steel, to reduce the non-metallic inclusions and sulphur content and to improve the mechanical properties of steel.

Abstract: The structural characteristics of low S (0.025%), low Al (<0.003%) and 4.0% carbon equivalent (CE) electric melted grey irons were studied at different solidification rates, for Ca and Ca,RE [Mischmeta as the inoculating elements. Despite a relatively high CE, this base iron is sensitive to undercooling during solidification. A conventional Ca-FeSi inoculant is not recommended for these critical conditions, especially to avoid undercooled graphite morphologies. It is only adequate to control free carbides, for castings with more than 15mm section. Rare earth (RE) bearing CaFeSi alloy appears to be a more effective solution, at least for castings with more than 5mm section to control carbides, even the end effect, and promote a homogeneous structure. Undercooled graphite presence was limited and avoided in more than 10mm section. Thin wall castings, less than 5mm section, requiring stronger control for carbides and undercooled graphite formation, should not be produced from this type of base iron, unless more efficient inoculation can be accomplished.

Abstract: The main objectiv of this experimental reserch is a comparative analysis of sulphur and oxygen effects on the cooling curves parameters at different iron melt modifying potential (residual Mg content). For the experiment, three irons with different modifying potential (0.0014, 0.0213 and 0.033 wt % residual Mg content respectively) were developed. After Ca-Ba inoculation, the three irons were additional treated by stoichiometric equivalent additions of sulphur or oxygen as FeS₂ and Fe₂O₃ respectively. Both FeS₂ and Fe₂O₃ sources were placed on the bottom of standard Quik-Cup moulds,usualy used for iron melt thermal analysis. The effect of sulphur and oxygen on the standard and nonconventional cooling curves parameters were evaluated to a more deep understanding of the cast iron solidification mechanism. The cooling curves parameters are strongly influenced both by the initial residual Mg level of iron melt and afterwords sulphur/oxygen additions. A very complex and sometimes confused variation of the cooling curves parameters was recorded because of different actions of the three factors (iron melt modifying potential, sulphur and oxygen). As a previous paper highlighted, sulphur addition has a strong graphite decompactizing effect while oxygen addition has mostly an inoculant effect.

Abstract: This paper takes the conversion system of sulphuric acid plant made with the sulphur as research object, utilizes Aspen Energy Analyzer software and pinch technology to improve and optimize for the current heat exchange network of conversion system. The heat exchange network optimized by Aspen software is under the premise of reaching the requirement of heat exchange, its heat transfer area, utilities and operating cost reaches the minimum, achieving energy saving, and it provides a new approach for the optimal design of heat exchange network.