The following paper presents an approach to the mathematical modeling of thermo-chemical reactions and relations in a 3-phase, 80 MVA AC, electric arc furnace (EAF) and represents a continuation of our work on modeling the electric and hydraulic processes of an EAF. This paper is part 2 of the complete EAF model and addresses the issues relating to chemical reactions and the corresponding chemical energy in the EAF, which are not included in part 1 of the paper, which is focused on mass, temperature and energy-exchange modeling. Part 2 and part 1 papers are related to each other accordingly and should be considered as a whole. The developed and presented sub-models are obtained according to mathematical and thermo-chemical laws, with the parameters fitting both experimentally, using the measured operational data of an EAF during different periods of the melting process, and theoretically, using the conclusions of different studies involved in EAF modeling. Part 2, part 1 and the already published electrical and hydraulic models of the EAF represent a complete EAF model, which can further be used for the initial aims of our project, i.e., optimization of the energy consumption and the development of an operator-training simulator. Like with part 1, the obtained results show high levels of similarity with both the operational measurements and theoretical data available in different studies, from which we can conclude that the presented EAF model is developed in accordance with both the fundamental laws of thermodynamics and the practical aspects relating to EAF operation.
The following paper presents an approach to the mathematical modeling of heat and mass transfer processes in a 3-phase, 80 MVA AC, electric arc furnace (EAF) and represents a continuation of our work on modeling the electric and hydraulic EAF processes. This paper represents part 1 of the complete model and addresses issues on modeling the mass, temperature and energy processes in the EAF, while part 2 of the paper focuses solely on the issues related to the thermo-chemical relations and reactions in the EAF. As is generally known, the chemical, thermal and mass processes in an EAF are related to each other and cannot be studied completely separately; therefore, the work presented in part 1 and part 2 is related to each other accordingly and should be considered as a whole. The presented sub-models were obtained in accordance with different mathematical and thermo-dynamic laws, with the parameters fitted both experimentally, using the measured operational data of an EAF during different periods of the melting process, and theoretically, using the conclusions of different studies involved in EAF modeling. In conjunction with the already presented electrical and hydraulic models of the EAF, the heat-, mass-and energy-transfer models proposed in this work represent a complete EAF model, which can be further used for the initial aims of our study, i.e., optimization of the energy consumption and development of the operator-training simulator. The presented results show high levels of similarity with both the measured operational data and the theoretical data available in different EAF studies, from which we can conclude that the presented EAF model is developed in accordance with both fundamental laws of thermodynamics and the practical aspects regarding EAF operation.
The following paper presents an approach to the mathematical modeling of 3-phase AC, electric arc furnace (EAF) processes for control-design and process-optimization purposes. The EAF can be, from the modeling point of view, considered as a combination of electrical, hydraulic, chemical, thermal and several energy-balance sub-processes or sub-models. In this paper the modeling of the electrical and hydraulic submodels is presented in detail, since the two represent a very complex and important sub-system of the complete EAF model. The presented sub-models are obtained in accordance with different mathematical, electrical and mechanical laws. Several parameters, which are necessary to successfully identify the scrapmelting process, were fitted experimentally, using the measured operational data of an 80 MVA AC furnace during different periods of the melting process. Similar data has also been used for the validation of the developed model in typical EAF operating situations. The aim of the presented EAF modeling is to obtain an accurate, robust and realistic mathematical model of the scrap-melting process, which will later be used for control-design purposes, the optimization of the energy consumption and the development of an operatortraining simulator. The main advantage of our modeling approach over the existent EAF-related models is a more macroscopic level of modeling, which accurately simulates the electrical and hydraulic processes under different conditions in the EAF.KEY WORDS: EAF; electric model; hydraulic model; experimental validation; harmonic analysis. reactances; etc.) and non-electrical (transformer and reactor taps; number of short circuits and arc breakages; electrode controller outputs; electrode position; temperatures of the cooling panels; composition and weight of the additives; consumption of oxygen, carbon, gas; etc.) values sampled over a 1-s time window. At this stage of the model's development, nearly all of the electrical and some of the mechanical values were used to obtain the correct parameters of the sub-models describing the electrical properties of the EAF. Additionally, since the properties of the electric arcs are dependent on the position of the hydraulically actuated electrodes, the presented hydraulic sub-model for the electrode control completes the particular modeling assembly. Measurements and Modeling EAF Operation DataFor the purposes of this study, the measurements were made during different operational situations in the EAF melting process. The obtained data included measurements of the effective values, i.e., the root mean squares (RMS), sampled over a 1-s window of the following: phase voltages; phase-to-phase voltages; arc voltages; phase currents; power factors; arc resistances and reactances; total circuit resistances and reactances; apparent, active, reactive and arc power; total energy consumption; etc. The measurements were made with the electrode-control and data-acquisition system (E.M.P.E.R.E.). 8) ModelingThe following section presents the approach to mod...
This paper presents an approach to the mathematical modeling and validation of the radiative heattransfer processes in an electric arc furnace (EAF). This radiative heat transfer represents an important part of the complete EAF model, which is further composed of electrical, hydraulic, thermal, chemical and mass-transfer sub-models. These have already been addressed in our previous publications. It is well known that during the operation of an EAF all three types of heat transfer (conductive, convective and radiative) are present; however, a great portion of the heat is transferred between the surfaces by means of radiation. The model presented in this work uses a simplified internal geometry of the EAF to represent the relations between the defined EAF zones and is developed in accordance with fundamental thermodynamic laws. The parameters of the model were fitted using the geometrical relations in the EAF; theoretically, using the conclusions from different studies involved in EAF modeling; and experimentally, using the measured temperatures on the furnace roof and the water-cooled panels. Since the radiative heat mostly represents a negative impact on the furnace roof, walls and linings, the obtained model represents an important part of the complete EAF. The presented results show satisfactory levels of similarity between the measured and simulated temperatures of the roof and water-cooled panels, which suggest that the presented model is relatively accurate and follows the fundamental laws of thermodynamics. Possessing such a model is of special importance when enhancing the EAF process using different optimization techniques, since the radiative impacts on the furnace need to be taken into the account in order to maintain or reduce the wear on the furnace lining.
Increasing demands on effluent quality and loads call for an improved control, monitoring and fault detection of waste-water treatment plants (WWTPs). Improved control and optimization of WWTP lead to increased pollutant removal, a reduced need for chemicals as well as energy savings. An important step towards the optimal functioning of a WWTP is to minimize the influence of sensor faults on the control quality. To achieve this a fault-detection system should be implemented. In this paper the idea of using an evolving method as a base for the faultdetection/monitoring system is tested. The system is based on the evolving-fuzzy-model method. This method allows us to model the nonlinear relations between the variables with the Takagi-Sugeno fuzzy model. The method uses basic evolving mechanisms to add and remove clusters and the adaptation mechanism to adapt the clusters' and local models' parameters. The proposed faultdetection system is tested on measured data from a real WWTP. The results indicate the potential improvement of the WWTP's control during a sensor malfunction.
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