Sharif Digital Repository

Oxy-fuel firing is more energy efficient and environmental friendly than conventional air-fuel firing and its application to reheating furnaces has hegun since 1990s. A computational method was presented to predict the steady heat transfer to the billets and temperature distribution in a continuous pusher type reheating furnace in which combustion air was enhanced by oxygen. Radiation heat flux calculated from the radiation heat exchange within the furnace was modeled using the FVM considering the effects of furnace walls and billets. Energy consumption per ton of steel, production rate and thermal efficiency of furnace, and trend of NOx emission in various levels of oxygen enrichment were... 

For steel industries optimum operation with high efficiency is of the first importance. On the other hand, extra investments in the supply side of electric arc furnaces may have been seen as redundant cost. Therefore, to improve the system efficiency, devices such as SVCs or STATCOMs can be employed. In this paper, the benefits of dynamic shunt reactive compensation by SVCs in steel industries are investigated. It is shown that this operation leads to optimization in steel production process and is completely beneficial from economic point of view. Supply system of a typical arc furnace is simulated using MATLAB software and the effects of a compensator on the operating characteristics of an... 

This paper presents an electric arc furnace (EAF) optimization framework intended to define optimal control profiles for the EAF, in order to increase its efficiency and thus reduce the energy consumption. The framework aims to minimize controllable losses and to maximize energy transfer to the bath and, consequently, minimize the operational costs. This is achieved through improved actuation of the EAF inputs, i.e., transformer power, oxygen lancing, and carbon addition. To achieve maximal energy transfer to the bath and to reduce the heat losses from the arcs, proper properties of the slag, such as foaminess and basicity, are a subject of considerable attention. The framework is designed... 

In this study main reactive power calculation methods are evaluated and compared. Furthermore, a novel simple method that can be used for calculation of reactive power in electric arc furnace (EAF) plants is proposed. The focus here is on their application in the control system of static VAr compensators (SVCs). SVC can compensate only the fundamental harmonic component. So the reactive power signal used in the control system should be sensitive only to the main harmonic component. In addition, the reactive power calculation should be fast enough that SVC can follow the quick changes of the load to mitigate the flicker efficiently. To compare various reactive power calculation methods and to... 

The paper presents a conceptual study on modification of the electric arc furnace (EAF) slag doors in order to allow removal of the excess slag from the EAF. The idea behind additional slag doors is to allow deslagging of the bath in certain unfavorable cases when the slag height is too great. Slags which exceed the optimal height cause unnecessary refractory corrosion and additional energy losses. The study proposes symmetric slag doors comprised of two hatches, i.e. upper and lower. The upper hatch is intended to decrease the slag height to the optimal level, while the lower hatch can be used to completely deslag the EAF at tapping. In this manner, tilting of the EAF is not necessary. A... 

In this study, a combination of energy and exergy analysis is applied for the industrial sulfur recovery unit (SRU) in commercial simulation software. The data of energy and exergy are obtained from the simulator and Excel (for physical and chemical exergy), respectively. In doing so, five intensified SRU configurations namely: (1) hot gas bypass (2) acid gas bypass (3) inlet stream preheating (4) acid gas enrichment and (5) oxygen (air) enrichment are compared in terms of energy production, reaction furnace temperature, sulfur recovery and pollutant emission into environment. Then, irreversibility in these five arrangements is compared and all the proposed methods show higher useful exergy... 

In this paper, a numerical simulation involving fluid flow and heat transfer is presented in order to improve the understanding of rotary furnaces. The finite element model is employed to simulate the furnace rotation and analyse the energy flows inside the furnace. A transient dynamic analysis is carried out to predict the evolution and distribution of temperatures in a rotary furnace by modelling and analysing the furnace under different flame positions. The finite element modelling system ELFEN is used to develop models of the furnace. The results clearly indicate the temperature distribution for different angular velocities along with a comparison of temperature variation under different... 

This paper presents a new time domain model for electric arc furnaces using MATLAB, The model can simulate both nonlinear and time varying nature of such loads, which create flicker, harmonics, and voltage/current unbalance. In this model, Cassie and Mayr equations are used in three-phase mode and the effects of arc furnace transformer tap changer and flexible cables mutual inductances are considered. The proposed model takes into account the system inter-relation of parameters and arcing conditions as well  

In this study, leaching of reverberatory furnace dust at Sarcheshmeh was investigated in H2SO4-O3 medium. Response surface methodology based on central composite face-centered design (RSM-CCF) was applied to optimize the operating parameters. The optimal conditions to achieve the principle objectives of maximizing copper dissolution and minimizing iron dissolution from dust were identified to be a temperature of 30 °C, a leaching time of 3 h, an initial pH of 0.5, a pulp density of 20%, and an ozone flow rate of 1 g/h. Under the optimum conditions, the copper and iron concentrations in the leaching solution were found to be 27.11 and 0.90 g/L, respectively. The results showed that selective... 

The ability of static VAr compensators (SVC) to reduce the flicker caused by electric arc furnaces and other variable VAr loads depends on their speed, which is limited by delays in reactive power measurement and thyristor ignition. In this paper, a predictive method is proposed to compensate the delay time and, hence, to improve the SVC performance. Previous samples of the load reactive power are used to predict its future values. Predicted VAr is then applied as a reference for reactive power compensation. © 2006 IEEE  

In the absence of powerful rigorous models, in this research a simple but practical method for calculating the temperature and residence time and carbon black yield in oil-furnace reactors is proposed. For this purpose an empirical formula of the form CXHY is assumed for the carbon black feedstock based on typical feedstock used in this industry. Based on the prevailing reactor conditions, thermodynamic considerations and available outlet tail gas from the reactor, a few representative reactions are considered to describe the entire reaction network. These include complete combustion for the fuel and, incomplete combustion and pyrolysis for the feedstock. Carbon black yield can be estimated... 

The paper studies the effects of solid and liquid steel properties on the heat transfer coefficient (HTC) in electric arc furnaces (EAFs). Mathematically speaking, the HTC is a function of solid and liquid steel properties. Different velocities of the bath cause different flow paths around the solid particles and therefore different HTCs - a computational issue that has not been addressed yet. Therefore, a simplified calculation model is proposed, intended for HTC estimation according to the EAF conditions. Although many studies investigated this topic, most of them either assume unconventional conditions for the EAF operation, are computationally complex or focus on a specific case; and... 

In this paper, a conceptual study and quantification of using a thermophotovoltaic system (TPV) to convert incident radiation on furnace panels to electrical energy is presented. In typical electric arc furnaces (EAF), a considerable amount of energy is wasted during the melting process, that is, steel enthalpy, off-gas extraction, vessel cooling, slag enthalpy, and others. Although a remarkable share of the energy is wasted in circulating water, the contained exergy is simply too low to be considered for heat recovery (under 0.5% of input exergy) in comparison to energy content of the extracted gasses and slag. In the performed study, a TPV power output is calculated as a function of arc... 

Electric arc furnaces are used to make steel from scrap iron in steel industry. Nowadays, the aim of more researches in this area is to increase yield of furnace and it's compatibility with environment. One of the methods to achieve these purposes is to control the off-gas system as relative pressure in furnace would be kept negative. Because the combustion gases inside the furnace must not leak into the plant environment. However for preventing of loss of energy, the amount of this negative number must be small. In this paper, new intelligent control method named fuzzy emotional control, applied to off- gas system to control the relative pressure in the furnace and its result is compared to... 

The nonlinear and time varying nature of electric arc furnaces (EAFs) create flicker, harmonics, and voltage/current unbalances. Nowadays to improve the performance of EAFs and the power quality problems of electrical systems around them high speed compensators like STATCOM are needed. This paper uses a time domain model for electric arc furnaces and a new model of STATCOM respectively for creating and improving mentioned power quality problems. In this paper, first we investigate and simulate electric arc furnace and STATCOM using SIMULINK/PSB. Second, we simulate a network including them completely. The proposed models take into account arcing conditions and associated effects improvement... 

This paper presents a newr control strategy for the shunt active filter in three-phase three-wire svstems with zero sequence voltages. An extended method based on instantaneous power theory in a rotating reference frame is developed for extracting the compensating signals for highlv/randomly varying loads. Since voltages at the point of common coupling contain low frequency interharmonics, conventional methods can not be used for dc voltage regulation. Therefore, a new method is introduced for this purpose. A three-phase electric arc furnace model is used to showT power quality improvement through reactive power and harmonic compensation by a shunt active fi'lter using the proposed method.... 

The production of reducing gas is usually a bottleneck to capacity increase in direct reduction plants. Modelling and simulation of reducing gas production result in better design and operation of these plants. In the present work, a mathematical model is discussed that relates to a Midrex reformer, which is different from conventional steam reformers in some respects. Both process side and furnace side have been included in an integrated model. Simulation results have been tested against available data from an actual plant. The model predictions have been found to be reasonably accurate. The effects of three process variables, feed gas temperature, feed gas pressure and excess air, on...