Showing 8 results for Dri
S. Aminorroaya and H. Edris,
Volume 21, Issue 1 (7-2002)
Abstract
In electric arc furnace steelmaking units, the essential parameters are reducing price, increasing production and decreasing environmental pollution. Electric arc furnaces are the largest users of electric energy in industry. The most important techniques that can be used to reduce the electric energy consumption in electric arc furnaces are scrap preheating, stirring, use of burners and hot charge and foamy slag. Between these methods, the use of foamy slag is the most useful and economical factor. Foamy slag can reduce the amount of energy, electrodes, refractory consumption, and tap to tap time while it also increases productivity.
In this study, method of production and optimum conditions for foamy slag in a 200-ton electric arc furnace were investigated. The use of foamy slag in this research can reduce the electric energy consumption from 670 to 580 kwh/t and the melting time from 130 to 115 min. and that the electric power input can be increased. It also shows that with foamy slag, the optimum amount of FeO in slag is 20-24 percent and the optimum basicity is 2-2.2.
Keywords: electric arc furnace, energy, DRI, foamy slag
J. Soltani and F. Katiraei,
Volume 22, Issue 1 (7-2003)
Abstract
In this paper, using a personal computer (PC), the practical implementation of scalar and vector control methods on a three–phase rotor surface- type permanent magnet synchronous machine drive is discussed. Based on the machine dynamic equations and the above control strategies, two block diagrams are presented first for closed-loop speed controlling of the machine drive/system. Then, the design and implementation of hardware circuits for power, insulating, and signal matching stages are explained along with a description of the written software program for the servo drive system control. These circuits are
used to produce the drive inverter switching pulses. To supply the machine drive, the sinusoidal, uniform sampling and step-trapezoidal PWM voltage source inverters are examined. For closed loop speed control of the drive system, the stator currents and rotor speed signals (in scalar control method only the rotor speed) are sampled on-line. After filtering, buffering and matching operations, these signals are transferred to a personal computer port via a high frequency sampling and high resolution A/D converter. It is worth mensioning that both methods of controlling mathematical calculations is done by computer. Finally, the practical and computer simulation results obtained are demonstrated.
Keywords: Machine Drive, Synchronous Machine, Permanent Magnet, Rotor Surface Type, Scalar and Vector Control, Voltage – Source Inverter, Control by PC.
J. Soltani and N. R. Abjadi,
Volume 22, Issue 2 (1-2004)
Abstract
In this paper, based on feedback linearization control method and using a special PI (propotational integrator) regulator (IP) in combination with a feed-forward controller, a three-phase induction servo-drive is speed controlled. First, an observer is employed to estimate the rotor d and q axis flux components. Then, two input-output state variables are introduced to control the dynamics of torque and the magnitude of the rotor flux independently. In addition, based on the model refrence adaptive system (MRAS) and the recursive least square (RLC) error techniques, the rotor time constant and the mechnical parameters (J, R) are simultaneously estimated. Finally, the efficiency of the proposed method is confirmed against results from computer simulation.
Keywords: Adaptive speed ontrol, Inducation servo-drive, Feedback linearization, IP controller, Model reference, Adaptive
system, Recursive least square.
K. Badv,
Volume 23, Issue 2 (1-2005)
Abstract
This study is an attempt to introduce scientific fundamentals and available methods for wellhead protection area (capture zone) delineation for drinking water wells in cities. The results of this study could obviate some demands of the national water and wastewater company in quality control of the drinking water resources by delineation and application of the wellhead protection areas. For this purpose, the available literaturer reviewed to extract, criteria and methods of wellhead protection delineation, Then, (1) fixed radius method, (2) simplified variable shape methods, and (3) flow-transport analytical methods implemented in the computer code WHPA are introduced. The applicability of these methods is shown by some sample calculations for Urmia drinking water wells. Samples of the calculated wellhead protection areas for 36 wells in Urmia City will be shown using three analytical modules in WHPA. The effects of the hydrogeologic parameters on the wellhead areas will be discussed. When reliable hydrogeologic parameters are available in the region where wells are located, the analytical methods and WHPA code produce accurate results for wellhead protection areas.
J. Safarian-Dastjerdi and A. Saidi, ,
Volume 24, Issue 1 (7-2005)
Abstract
A higher bustle temperature in midrex direct reduction process is always desirable due to its positive effect on the productivity and DRI quality. The limit of the bustle temperature is related to the sticking or clustering behaviour of oxide pellets during the reduction in the reactor. It has been well estabilished that coating of oxide pellets by a refractory material decreases its
tendency to clustering. In this study, the clustering behaviour of oxide pellets (produced from Golegohar-Chadormalu iron ore) during redution at different temperatures was investigated. The effect of coating with different amounts of hydrated lime on the clustering behaviour was also examined. Microscopic examination of coated pellets shows a porous, non-continious layer of Ca(OH)2 being fromed on the surface of the pellets. The clustering tendency of coated pellets, measured by the standard sticking test at pilot scale, was much lower, compared with normal (uncoated) pellets, while their reducibility was the same.
R. Bagheri and M.a. Golozar,
Volume 25, Issue 2 (1-2007)
Abstract
Using Electrostatic Spray Coating Technique, Polypropylene Powder (EPD 60R) was applied on carbon steel substrates at room temperature. In order to obtain a uniform coating, steel substrates with powder coatings were heated in a vacuum oven at various temperatures up to 250° C for various periods of time up to 45 min and a pressure of 200 mb. The coatings produced had thicknesses of around 470 microns. In order to modify the chemical structure of this polymer, the powder coatings containing various weight percentages of maleic (anhydride (MA) and a peroxide (TBHP or DCP) were also applied onto the steel substrates under the above conditions. Adhesion strength, wear resistance, and ductility of polymer coatings produced were assessed using ASTM standard methods. Results obtained revealed that the polymer coating containing 5 wt%. MA and 0.1 wt% TBHP had the best mechanical properties. Adhesive strength and wear resistance of this coating were 14.3 kgf and 250.3 cm, at 6 kgf, respectively, under the applied load of 6kg. Results obtained from DSC thermographs and IR Spectroscopy also proved the chemical bond formation (grafting) between the polymer and MA. The mechanical properties of coatings on steel substrate stem from such graftings.
H. Khabbazi, R. Bagheri, and M.a Golozar,
Volume 26, Issue 1 (7-2007)
Abstract
Polypropylene (PP) has poor adhesion to metals and other surfaces for its chemical structure. Hence, chemical modification of PP is necessary for metal surface coating application. In this research, grafting of maleic anhydride (MA) onto co(propylene-b-ethylene) in the presence of a dicumyl peroxide (DCP) was accomplished in a single screw extruder. Characteristics of the modified polymer were determined by Infra-red Spectroscopy (IR), Scanning Electron Microscopy (SEM), and adhesion test. Maximum grafting of MA was found to be 1.2832% for 1.5 pph of MA. Adhesion test showed that the samples containing 1 pph of MA (degree of grafting is 0.5816%) had better adhesion to steel surface (17.25 kgf).
S. A. Ahmadi, M. H. Pashaei, R. A. Jafari-Talookolaeilokoolaei,
Volume 39, Issue 1 (8-2020)
Abstract
In this paper, three-dimensional displacement response of a cylindrical sandwich panel with compressible core under the action of dynamic pulse loading is addressed using the extended high order sandwich panel theory. Also, local dynamic pulse buckling of facesheets is studied by considering the Budiansky-Roth buckling criterion. It is assumed that the sandwich panels consist of orthotropic face sheets and an isotropic viscoelastic foam core layer. The effects of various parameters including the panel span, core and facing thickness, pulse duration and maximum pressure on the non-linear dynamic response and buckling strength of the sandwich cylindrical panel are studied. The results obtained from the present method are compared with finite element solutions using the commercial software ANSYS and those reported in the literature, showing a good agreement. It is revealed that applied core non-linear theory could be satisfactory for the dynamic pulse response of sandwich viscoelastic panels. It is also shown that the pulse buckling strength of panel increases with a decrease of the panel radius or an increase of the panel thickness.
