Production of Ferro-Silicon and Calcium Alloys

Initially the process of production of ferro-silicon was developed empirically [1]. Ferro-silicon is made by reducing quartzite with metallurgical coke/gas coke/ Low Temperature Carbonized coke/charcoal. Quartz, quatzite and chelcedony are the cheapest minerals rich in silicon are used for the manufacture of ferro silicon [2]. In India mainly charcoal is used [3]. The techno-economics of the process of ferrosilicon production improves considerably with the increase of the capacity of the furnace [4]. The feasibility of using plasma smelting of low cost taconite tailings to produce ferrosilicon at a high yield has been demonstrated [5]. Large amounts of ferro-silicon are used for the reduction of various oxides in ferro-alloy prod-uction and high percentage ferro-silicon in the form of powder is used as a slag deoxidiser. The scale of opera-tion of ferrosilicon production has increased' steadily, and furnace construction and the auxiliary systems for transport, weighing and control have been modernised but the basic process is essentially unchanged. This paper provides an overview of the raw material requirements, thermochemical consideration, charge calculation, opera-ting conditions, recent developments and, finally, the results of pilot scale trial and industrial plant

Development of a Thermo-Chemical Model for the Production of Calcium-Silicon Alloys

Calcium silicon alloys are used in iron and steel industry as powerful deoxidation and desulphurisers. A thermo-chemical modl has been evolved to predict the grade to the alloy, slag and gas composition and heat losses from the furnace

Pollution Control in Ferro-Alloys Production

Of late, there is increased awareness of pollution hazards within the metallurgical industry. The Government of India through various central and state pollution control agencies has taken steps to effectively protect ecology from pollution.The primary manufacturing processes for most of the bulk Ferro-alloys are carried out in submerged arc furnaces. The submerged arc furnaces, used in the manufacturing of ferro-alloys, are now included in "Red Category" as equipments giving rise to high degree of pollution for which immediate action has to be taken for effective control. Much of the atmospheric pollution from ferro-alloys production is smoke, fume and dust. The smoke mostly consists of soot, fly ash and other solid and liquid particles to be about 0.075 or 3 milli-onth of an inch. Coke smoke contains a high proportion of carbon. Fumes are synonymous with dirt and are mostly composed of solid particles: Fumes are generally less than 1 micron in diameter and commonly consist of metals and metallic oxide and chlorides. For expansion of existing plants and for new plants, installation of pollution control equipments has been made compulsory. This papers provides and overview of the state of pollution in ferro-alloys production and focusses in the main methods of pollution control, with special reference to Indian conditions

An Invariance Property of Common Statistical Tests

Let A be a symmetric matrix and B be a nonnegative definite (nnd) matrix. We obtain a characterization of the class of nnd solutions Σ for the matrix equation AΣA = B. We then use the characterization to obtain all possible covariance structures under which the distributions of many common test statistics remain invariant, that is, the distributions remain the same except for a scale factor. Applications include a complete characterization of covariance structures such that the chisquaredness and independence of quadratic forms in ANOVA problems is preserved. The basic matrix theoretic theorem itself is useful in other characterizing problems in linear algebra. © 1997 Elsevier Science Inc

On the Potentiality of Production of Low S & P Hot Metal by VRDR-SAF Process

Blast furnace technology is still the large scale indus-trial producer for hot metal and is expected to remain in the main stream for number of years. Coking coal reserves are depleting hence, there is a necessity for developing alternative processes using abundantly available non-coking coal. The new iron making processes avoid the depe-ndency of high quality metallurgical coal hence the deve-lopment has resulted in large number of processes. The important amongst them are COREX, Direct Iron Ore Smelting Process (DIOS), Hi Smelt Process etC, NML has developed a process using noncoking coal as reductant to produce sponge iron in a vertical retort direct reduction furnace developed at NML And the sponge iron so produced is hot charged to sub-merged arc furnace for production of liquid iron containing low sulphur and phosphorus. It has been demonstrated that the liquid iron can be produced with low sulphur (less than 0.02 % and phosphorus less than 0.06% ) and can be successfully and economically produced by utili-sing this process. The paper describes the details of the same

The glass transition and crystallization kinetic studies on BaNaB9O15 glasses

Transparent glasses of BaNaB9O15 (BNBO) were fabricated via the conventional melt-quenching technique. The amorphous and the glassy nature of the as-quenched samples were respectively, confirmed by X-ray powder diffraction (XRD) and differential scanning calorimetry (DSC). The glass transition and crystallization parameters were evaluated under non-isothermal conditions using DSC. The correlation between the heating rate dependent glass transition and the crystallization temperatures was discussed and deduced the Kauzmann temperature for BNBO glass-plates and powdered samples. The values of the Kauzmann temperature for the plates and powdered samples were 776 K and 768 K, respectively. Approximation-free method was used to evaluate the crystallization kinetic parameters for the BNBO glass samples. The effect of the sample thickness on the crystallization kinetics of BNBO glasses was also investigated.Comment: 23 pages, 12 figure

On Approximate Envy-Freeness for Indivisible Chores and Mixed Resources

We study the fair allocation of undesirable indivisible items, or chores. While the case of desirable indivisible items (or goods) is extensively studied, with many results known for different notions of fairness, less is known about the fair division of chores. We study envy-free allocation of chores and make three contributions. First, we show that determining the existence of an envy-free allocation is NP-complete even in the simple case when agents have binary additive valuations. Second, we provide a polynomial-time algorithm for computing an allocation that satisfies envy-freeness up to one chore (EF1), correcting a claim in the existing literature. A modification of our algorithm can be used to compute an EF1 allocation for doubly monotone instances (where each agent can partition the set of items into objective goods and objective chores). Our third result applies to a mixed resources model consisting of indivisible items and a divisible, undesirable heterogeneous resource (i.e., a bad cake). We show that there always exists an allocation that satisfies envy-freeness for mixed resources (EFM) in this setting, complementing a recent result of Bei et al. [Bei et al., 2021] for indivisible goods and divisible cake

Melting behaviour of sponge iron in induction furnace

Sponge iron with its consistency of composition, lower content of tramp elements and particularly low phosphorus and of sulphur has drawn the attention of medium/large scale foundries for producing quality steel castings. It is one of the alternative charge materials to scrap in induction furnaces. National Metallurgical Laboratory has made an attempt to melt sponge iron in induction furnaces and optimize its melting behavour. It is possible to use continuous charging arrangements for melting of 100% sponge iron in induction furnace

Potentialities of Alternative Charge Materials for the Electric Arc Furnace

Traditionally, scrap has been the raw material feed to the electric arc furnace, but increasingly DRI, pre-reduced pellets, HBI, pig iron, hot metal and iron carbide are being focussed as potential alternative charge materials for the electric arc furnace. The partial substitution of scrap by these charge materials improves the quality of steel, decreases energy consumption and increases productivity

Lung cancer with multiple lung abscesses: an unusual presentation

Lung abscess is caused due to localized suppuration in the lung usually caused by microbial infection of the lung. Here we are describing an interesting case of multiple lung abscess associated with non-small cell lung cancer. The diagnosis was suspected on CT scan thorax and was confirmed by fibreoptic bronchoscopy and endobronchial biopsy. Hence, lung cancer should be suspected in any case of lung abscess when it is showing no signs of resolution even after aggressive conservative management with broad spectrum antibiotics