Thermodynamics of Refining in Electric Furnace Steelmaking

In general, the input impurity levels in the electric and induction furnace charge is low, so refining does not pose any special problems. But the use of poor quality or unsorted scrap or high phosphorus sponge in the charge can lead to significant increase in the input impurity level. Besides, quite often the desired final impurity level is very low. Composition control in these cases pose a problem particularly because a large refining time leads to a higher power consumption and low productivity. To overcome this difficulty, ladle refining as secondary steelmaking practices are widely used along with the electric steel making. In this lecture refining principles both in electric furnace and ladle furnace will be discussed.Even at steelmaking temperatures, the reactions do not attain equilibrium unless the slag and metal phases are well stirred for a reasonable length of time. In this sense, equilibrium thermodynamics cannot give quantitative idea about the extent of actual refining that can be attained in electric and induction furnace

On the Direct Reduction of Iron Ore in Rotary Kiln

An analysis of direct reduction process in the isothermal zone of a rotary kiln has been made. The analysis results in four simultaneous ordinary differential equations and one algebric equation relating the fraction of total oxygen remaining in iron ore, the fraction of total carbon gasified, partial pressures of carbonmonoxide, carbondioxide and nitrogen inside the charge bed as a function of time. The numerical solution of equations shows that upto 90% reduction, the rate of reduction is practically constant and it depends on the following parameters: size of ore particles, reactivity of solid fuel, the ratio of iron oxide to carbon in the charge and the fraction of reactor volume occupied by the charge. For a particular reactivity of solid fuel, particle size of ore and the fraction of reactor volume occupied by the charge, the production rate increases with the increase in the ratio of carbon to iron oxide in the charge till the latter reaches a critical value, when further increase of the ratio dies not effect the production rate appreciably. This critical ratio of carbon to iron oxide in the charge increases with the decrease in the particle size of ore and with the increase in the reactivity of solid fuel but it is practically independent of fraction of reactor volume occupied by the charge. The analysis further shows that the production rate can be increased by increasing the amount of charge per unit reactor volume, using solid fuel of higher reacti- vity and by decreasing the particle size of iron ore

Realization of Resistorless Lossless Positive and Negative Grounded Inductor Simulators Using Single ZC-CCCITA

This paper is in continuation with the very recent work of Prasad et al. [14], wherein new realizations of grounded and floating positive inductor simulator using current differencing transconductance amplifier (CDTA) are reported. The focus of the paper is to provide alternate realizations of lossless, both positive and negative inductor simulators (PIS and NIS) in grounded form using z-copy current-controlled current inverting transconductance amplifier (ZC-CCCITA), which can be considered as a derivative of CDTA, wherein the current differencing unit (CDU) is reduced to a current-controlled current inverting unit. We demonstrate that only a single ZC-CCCITA and one grounded capacitor are sufficient to realize grounded lossless PIS or NIS. The proposed circuits are resistorless whose parameters can be controlled through the bias currents. The workability of the proposed PIS is validated by SPICE simulations on three RLC prototypes

Choice of Corrosion Resisting Materials in Extraction of Metals

For recovery of different metals from metallic ores, chemical and gyro-metallurgical treatments, such as roast-ing, smelting and leaching are performed under varying conditions of temperatures, pressures and corroding media. Since the economics of a process is influenced among others by the life of the equipment, materials for cons-truction thereof are selected so as to possess required resistance to corrosion and abrasion. This paper reviews the use of various metals and alloys possessing maximum corrosion resistance for extraction of metals under certain specified conditions

Mass Handling of Materials

Material handling is defined as the operation of lifting and shifting . The object of all material handling is the reduction of handling cost, time, storage space, and effort. Mechanised handling permits synchronisation of operations, avoidance of bottlenecks keeping the job on the move and reduction of manual labour which may be devoted to more useful purpose requiring skill and inte-lligence.Mounting labour costs throughout the world have also directed attention to the expanding importance of mechanised handling in every field of industry

Green processes in process metallurgy

Environmental pollution ultimately governs the economic or industrial growth rate of the world. Ideal green processes, both conceptual and feasible are discussed and the advantages and limitations are brought out. Typical examples of novel techniques developed to combat pollution are presented. An integrated approach coupling energy saving with pollution control measures appears to be the best strategy

Clean Technology : Limit and Limitation

The limiting of pollutant emissions from COREX and Romelt processes, non-recovery coke ovens and coke less cupola have been calculated using equilibrium analysis. The results show that main pollutants present after full utilization of the exit gases from all the processes are sulfur dioxide and nitric oxide. The former is dependent on the volatile sulfur present in the fuel and later depends on temperature of combustion and amount of air used for combustion. Lowering of combustion temperature and closer control of combustion can reduce NO load signi-cantly

Process Engineering for Pollution Control and Waste Minimisation in Non -Ferrous Metallurgical Industries

The importance of industrial ecology in the materials cycle has been stressed.The different approaches to process design have been outlined and typical applications to non-ferrous metallurgy have been highlighted. The challenges and opportunities for pollution control and waste minimisation in the non-ferrous metallurgical industries with reference to gaseous emissions, liquid effluents and solid wastes have been examined

Parallel transport on non-Abelian flux tubes

I propose a way of unambiguously parallel transporting fields on non-Abelian flux tubes, or strings, by means of two gauge fields. One gauge field transports along the tube, while the other transports normal to the tube. Ambiguity is removed by imposing an integrability condition on the pair of fields. The construction leads to a gauge theory of mathematical objects known as Lie 2-groups, which are known to result also from the parallel transport of the flux tubes themselves. The integrability condition is also shown to be equivalent to the assumption that parallel transport along nearby string configurations are equal up to arbitrary gauge transformations. Attempts to implement this condition in a field theory leads to effective actions for two-form fields.Comment: significant portions of text rewritten, references adde