Browsing by Author "Stanev R."

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    ASSESSMENT OF THE IMPACT OF SOME METEOROLOGICAL FACTORS ON THE ENERGY AND ENVIRONMENTAL EFFICIENCY OF TUBE ROTARY KILNS
    (2023-01-01) Stanev R.; Mitov I.; Shtaplev I.; Harizanov V.
    It is emphasized that rotary kilns are units for high-temperature heat treatment of a wide range of materials in a continuous technological process. This type of equipment is used intensively in many industrial branches such as chemical, metallurgical, silicate, pharmaceutical and others. In metallurgy, these installations find application at heat treatment of bulk materials, for example at reduction of oxide ores, at calcination of limestone, drying of copper sulfide charge, cleaning of metal shavings from machine oil and others. An overview of the ways of heat transfer to the material processed in a given rotary kiln, as well as of the basic mathematical models for describing the complex transport phenomena in the considered units is made. An accent is put on the fact that due to their large size, rotary kilns are often installed on open areas within the industrial sites to whose equipment they are included. The variable weather conditions can have a significant impact on the energy flow that leaves the cage of such a unit. It dissipates uselessly in the environment, which is accepted as a reason to be widely characterized as “heat loss”. This concept contains some conditionality, because according to the law of conservation of energy, it can not be created and disappear, but is transformed from one species to another. Nevertheless, the convenience of expression it offers has led to its use in the present statement. The proposed work is focused on the analysis of results obtained from calculating the heat loss from a rotary kiln to the surrounding outside air at typical for the latitude and climatic features of Bulgaria average annual temperature and a presence of relatively weak constant wind. As a result of the performed calculations, conclusions have been made about the ratios between the individual heat fluxes from the outer surface of the unit to the environment, as well as practically oriented recommendations for improving the energy and environmental efficiency of the discussed equipment
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    Extension of the interrepairing period of metal recuperative heat exchangers
    (2014-01-01) Stanev R.
    The importance of the modern heat utilization equipment for the fulfillment of the activities related to the energy efficiency and sustainability of the individual divisions and shops, and thence - of the whole firm, is well known. Reduction of the relativefuel consumption in technological aggregates, productivity growth and the improvement ofthe output quality is based upon their energy updating. The solution of the enumerated tasks is related to the heat utilization of the outgoing flue gas from the furnace. In the present work the basic technical and technological problems for the introduction and exploitation of the recuperators in metallurgy, one of the industries with the highest energy consumption, is discussed. The implemented analysis of the factors influencing the interrepairing period of these units is also applicable in other industries like silicate and chemical ones, mechanical engineering, etc. The problems of the joint operation of the furnace and the metal utilizing equipment mounted to it, are reviewed. The most important causes for the occurring unfavorable phenomena are discussed, and results of our own and of the other's experience in the design and the service of these heat exchangers are presented. The basic constructive and exploitation measures leading to overcoming the disturbances in the functioning of the recuperators are pointed out, with an emphasis on the practical aspect of the raised problems.
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    Geometrical characteristics of the solid bed in a rotary kiln
    (2014-02-25) Stanev R.; Mitov I.; Specht E.; Herz F.
    Rotary kilns are aggregates for high temperature thermal treatment of a wide range of materials in a continuous technological process. This type of furnaces is used intensively in many industrial branches such as chemical, metallurgi-metallurgical, silicate, pharmaceutical, etc. In the metallurgy these units find application for heat treatment of bulk materials (e.g. oxide ores reduction, limestone calcination, sulphide copper stock drying, cleaning of metal swarfs from machine oil, etc). The present study enlarges the opportunities for a fast and reliable thickness determination of the separate zones of the solid disperse bed at rolling motion as the most widespread regime of its transverse transport. Data published in a previous work of the authors are used. They are obtained by a mathematical model established on the basis of regularities in the particles movement in a cylindrical rotary kiln, allowing determination of the total thickness of the layer of processed material and the active part of it, occupying the area immediately below the free surface of the bed. Approximation equations for prediction of the maximal values of the enumerated indicators depending on the inner diameter of the rotary kiln, its rotation speed, the filling degree of the drum with material, the dynamic angle of its repose and the particles diameter are proposed.
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    IMprovement of sintering process of platinum layers in electrical furnaces
    (2017-01-01) Gankov A.; Stanev R.
    With the increased requirements for the price and quality of the components used in automotive industry and also the enhancing criteria for on time deliveries, which are related with keeping the stock of parts in warehouses very low, more and more manufacturing companies of these elements are forced to optimizing measures and fitting-up of high-tech equipment. As a rule, before such investments, very serious economic rationale, detailed risk assessment and long functional tests, followed by customer validations and finally approval must be done. Each of those steps guarantees the quality and the expedience of the project. The technology of production of electro-resistive temperature sensors for the automotive industry, based on thin film platinum layers, uses many thermal processes on different stages of their elaboration as a main method for stabilization of each next applied micro layer. To their running are demanded great and diverse requirements, which enforce a high level of the equipment and the technologies. The present work aims to the improvement of two of the sintering processes of platinum paste, applied directly to the ceramic base of the sensor element, using identical thermal regime. Their implementation is realized in terms of changing the existing older type of furnaces with new advanced version of these aggregates with perfected design of the operating chamber and improved control of the temperature in it. An evaluation of the thermal work of standard furnace for the production and also of the new advanced type is made. Both results are compared. It is analyzed the influence of the sintering process on the treated platinum layers and the ceramic substrate. All received data are confronted with their relevant ones at using the standard units and conditions. The obtained results allow the conclusion, that the replacement of the equipment is reasoned and it not only improves characteristics and product quality, but also reduces variations in the performance of the process. It was analyzed the influence of the sintering process on the platinum layers and the ceramic base. All the obtained data are compared with those corresponding to them using standard conditions and aggregates.
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    INFLUENCE OF LOW-TEMPERATURE THERMAL RADIATION AT THE HEAT TRANSFER TO AN AIR AMBIENT
    (2020-01-01) Stanev R.; Choshnova D.; Velibashev S.
    The availability of some contradictory recommendations and facts in diferent literature sources has given a reason as a purpose of the present work to be chosen the fulfllment of a quantitative analysis of the influence of the radiative component in the total low-temperature energy fux. This aim is realized, as three typical for the practice cases are examined. They are connected to the heat transfer through a window of a residential room, from a tube with warm water to the environment and in a steel recuperator for air preheating by the internal energy of the outgoing fue gas from an industrial furnace. The results from the quantitative analysis of the influence of the radiative constituent in the total low-temperature heat transfer are commend and on the basis of them are formulated concrete ascertainments, to what kind of errors would lead the neglecting of the discussed mechanism
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    POSSIBILITIES FOR CONSTRUCTION OF PHOTOVOLTAIC PARKS ON INDUSTRIAL LANDS
    (2022-01-01) Stanev R.; Mihailova I.; Lazarov P.; Shtaplev I.
    It is carried out an overview of current European strategic documents regulating the guidelines for transition to a green, resource-efficient and competitive economy. The main place is given to industry and power engineering. It is pointed out that the elimination of the existing problems in these branches requires the most serious concentration of material and intellectual resources, as well as an entirely new approach to their solution. It is emphasized that in addition to a major overhaul of large power stations, this large-scale task can be supported by the diversification of electricity generation into smaller, flexible and based on modern environmentally friendly technologies generating facilities. On the ground of a critical overview of the literature on renewable energy sources (RES), as well as on our own previous studies, solar installations have been identified as especially suitable for such integration into factory circumstances. Finding suitable areas for their location is often associated not only with financial and technical, but also with significant infrastructure, logistics, urban, social and other difficulties. Given the above and in view of the desire for synergy between industry and energetics in solving their general and specific problems, as an aim of this study is chosen to be studied the possibilities for building of photovoltaic parks on industrial lands. Based on the analysis of three of the most widespread types of solar systems, conclusions and recommendations have been made for the choice of a concrete construction, as well as for the way of integrating such power generating equipment to the energy system of the respective plant. Three criteria are derived, according to which the technical-economical indicators of different variants for design and building of photovoltaic parks can be assessed under the restrictions imposed by the circumstances of the production area in the considered enterprise.
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    Rdf as an alternative fuel for the cement plants in Bulgaria
    (2017-01-01) Chamurova I.; Stanev R.; Deliyski N.
    With the growth of the world economy, the daily waste, generated by the industry and the way of life also increases. Since recycling does not solve comprehensively the problem about handling with the solid waste, significant resources are invested in the integration of combined systems and their management aimed at their complete utilization. As a member of the European Union (EU), Bulgaria is also committed to the entire concept for waste reduction, carbon dioxide emissions and other gases, causing the greenhouse effect on the earth surface. The cement industry appears to be among the most suitable places for solving the mentioned tasks. The substitution of its traditional fuels with alternative energy sources has turned into a widespread method not only in Europe, but in all economically developed countries worldwide. In the current work we discuss the possibilities for utilization of the highly calorific refused derived fuel (RDF) in Bulgaria, with the purpose to reduce the use of fossil energy resources in the cement production and to reach environment protection, according to the current Directives 2010/75/EC and 2000/76/EC of the European Parliament and of the Council. The main findings from this research are that the input of RDF in the rotary kilns in the cement plants on the territory of Bulgaria would affect positively the industry, both in technical and in environmental terms, and thence - in its economic aspects. The more specific results of the established trends are: reduction of greenhouse emission and other atmospheric pollutants, in particular - of ammonium oxides; cost reduction for fossil fuels; increase of the efficiency of the observed kiln, as well as; complete drop of the landfilled waste quantities on the territory of the state.