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

Wishartness and Independence of Matrix Quadratic Forms for Kronecker Product Covariance Structures

Let X be distributed as matrix normal with mean M and covariance matrix W⊗V, where W and V are nonnegative definite (nnd) matrices. In this paper we present a simple version of the Cochran’s theorem for matrix quadratic forms in X. The theorem is used to characterize the class of nnd matrices W such that the matrix quadratic forms that occur in multivariate analysis of variance are independent and Wishart except for a scale factor. © 2003 Elsevier Inc. All rights reserved

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

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

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

Effect of scale-up, design and process parameters on the productivity of ancient iron making process and recovery of iron in the product

Indian iron was famous in ancient times and it was exported to many countriesthroughout the world Though isolated pockets of iron making existed practically all over the country, yet there was no attempt of systematization and wider propagation. Recently an attempt has been made to establish proto-type furnace and scale it up with modifications in its design.The effect of scale -up.design and process parameters on the productivity of ancient iron making process and recovery of iron in the product has been discussed

Calcium Silicide - Methods of production and their technological consideration

Three industrial methods of production of calcium silicide have been discussed with their merits and demerits along with technological considerations. Calcium silicide was produced at NML in 500 KVA submerged arc furnace using partial charging method. Based on the results and observations of the smelting trials carried out a model has been proposed to explain the mechanism of form-ation of calcium silicide. Inoculation trials with calcium silicide produced at NML compares favourably with those obtained from abroad

Historical perspective of iron in ancient India

Iron is an important metal which has influenced the march of civilization over atleast 5000 years and it has been in the service of man from the dawn of time. The ancient scriptures and legends have extensive references about the use of iron. The archaeological evidences show that iron was being made all over India and there was no written records of the process of manufacturing iron. The technology has been handed over from one person to another within a limited group. Unfortunately this art phased out with the development of new technology during 19-20 century. The paper discusses the various sources of existence of iron, its utilization and importance right from pre-Rig Vedic period upto the first half of 20 century

Iron making in ancient India - a critical assessment

It is a well known fact, that Indian craftsman produced quality iron products much earlier than the developed countries, making use of local reserves of iron ore. Iron produced in ancient India was mostly wrought iron. The metal was obtained in the form of a pasty mass and then shaped under hammer. Today, when India is producing several million tons of iron, primitive iron making is still exists in some parts of India. The primitive iron making furnaces declined in numbers gradually from about 500 in the beginning of 20'h century to about 150 by the middle of the century. Their present number is not known. Such furnaces are in operation deep into the forests and the tribal areas of India. The paper discusses briefly the history of iron making along with the critical assessment of the ancient processes. Some of the important measures absolutely. essential to upgrade the processes have also been discussed. Several pertinent modifications have been proposed in the design of these furnaces to make them more energy efficient and economically viable 'for tribal and rural populace