DHARANIDHAR PATRA Study of Reduction Behaviour Of Iron Ore Lumps A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF BACHELOR OF TECHNOLOGY In Metallurgical and Materials Engineering By BINAYAK MOHAPATRA(10504004) DHARANIDHAR PATRA(10504021) DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING NATIONAL INSTITUTE OF TECHNOLOGY, ROURKELA MAY 2009 National Institute of Technology Rourkela CERTIFICATE This is to certify that the thesis entitled, “STUDY OF REDUCTION KINETICS OF HEMATITE IRON ORE BY COAL” submitted by Mr. Dharanidhar Patra in partial fulfillment of the requirements for the award of Bachelor inTechnology Degree in Metallurgical and Materials Engineering with specialization in “Metallurgical and Materials Engineering” at the National Institute of Technology, Rourkela (Deemed University) is an authentic work carried out by him under my supervision and guidance. To the best of my knowledge, the matter embodied in the thesis has not been submitted to any other University / Institute for the award of any Degree or Diploma. Prof. M. Kumar Dept. of Metallurgical & Materials Engg. National Institute of technology Rourkela – 769008 ABSTRACT Studies on chemical and physical properties, and reduction behaviour (in coal) of hematite iron ores, procured from ten different mines of Orissa, were undertaken to provide information to the iron and steel industries (sponge iron plants in particular). Majority of the iron ores were found to have high iron and low alumina and silica contents. All these iron ores were free from the deleterious elements (S, P, As, Pb, alkalies, etc.). The results indicated lower values of shatter and abrasion indices, and higher values of tumbler index in all the iron ore lumps except Serazuddin (previous) and Khanda Bandha OMC Ltd.. For all the fired iron ore pellets, the degree of reduction in coal was more intense in the first 30 minutes after which it became small. Slow heating led to higher degree of reduction in fired pellets than rapid heating. All the iron ores exhibited more than 90% reduction in their fired pellets in 2 hrs. time interval at a temperature of 9000C. Iron ore lumps showed lower degree of reduction than the corresponding fired pellets. CONTENTS (i) ACKNOWLEDGEMENT i (ii) PREFACE ii CHAPTER-1 1.1 INTRODUCTION 1-2 1.2 Sponge iron production scenario in India 2-3 1.3 iron ore and coal reserves in India 3 -5 1.4 DIFFERENT ROUTES OF SPONGE IRON PRODUCTION 5-7 1.5 SELECTION OF RAW MATERIALS FOR DRI PRODUCTION 7-14 1.6 MECHANISM OF DR PROCESS 14-17 1.7 LITERATURE REVIEW 17 1.8 Iron and steel production scenario in india 18 1.9 Aims and objectives 19 CHAPTER-2 20 EXPERIMENTAL details 2.1 PROCEDURE FOR REDUCTION STUDIES 20-21 Graphical analysis 21-27 CHAPTER-3 28 RESULT AND DISCUSSION 28 3.1Comparison of reduction characteristics of pellets (fired) and lumps 29 3.2 Effect of time on degree of reduction 29 3.3 Effect of heating mode on degree of reduction 29 CHAPTER – 4 CONCLUSION 30 REFFERENCES CHAPTER 1 1.1 INTRODUCTION DRI or Sponge Iron is a porous solid-state product of direct reduction process, which is produced either in lump or pellet form. DRI is a good substitute for steel scrap for producing steel in EAF, BOF etc, which resulted a rapid growth of the sponge Iron Industry. In view of increasing demand of sponge Iron in the manufacturing of different verities of steel, a good deal of emphasis is being given to promote the study of direct reduction process. The growth of DRI industry took place in it’s nascent form the later half of the 20th century, until then steel scrap constituted the major part of our import, next to petroleum product. Then Indian government imposed some curtailment measure and search for the alternatives began, and direct reduced iron was resulted as an alternative to the steel scrap, which is produced by the direct reduction of iron ore in the form of lump or pellet. In direct reduction (DRI) process ,there a good flexibility of using different kind of reductants like lower grade non coking coal, char coal, natural gas etc. The fast depletion of high grade cooking coal, reserves restricts the use of coke in conventional blast furnace-oxygen steel making route , in India. Being enriched with good quality Iron ore along with vast reserves of non coking Coal, which likely last for another 200 years or so India is in an adventitious for coal based Sponge Iron plants. The total gross reserves of coking and non coking coal in India are approximately 11,602 and 71,400 million tons respectively. From this prospective, the rotary kiln (coal based) DR process have developed well and vigorously in the country instead of natural gas based Shaft furnace or Retort furnace. In order to accept the potential of the fact, it is rather imperative to understand the basic mechanism involved in DR process using non coking coal as reductant. The reduction of iron ore by carbon is one of the most important reactions in iron making in blast furnace, rotary kiln and electric smelting furnace. Extensive studies has been carried out on the reduction behavior of iron ore mixed with carbon/char/graphite/coke etc , which reveals that the reduction reaction take place via gaseous intermediate like Carbon monoxide and Carbon dioxide. As such it is evident that, the actual direct reduction doesn’t need any gaseous medium to be carried out. But of late it has been rather well accepted that, the reduction of Iron oxide by carbon in blast furnace and direct reduction process of sponge Iron production is mostly the result of indirect reduction. Currently a lot of emphasis is being given to direct reduction process because use of pre-reduced pellets or sponge iron as feed for blast furnace, induction furnaces and basic oxygen furnaces, despite some associated drawbacks, offers much scope for improving both productivity and economy in coke consumption. 1.2 iron production scenario in India Sponge Trend of growth of production in India Installed capacity & production sponge iron in India up to 2009-10 : SIMA Projection (Million Tonnes) 1.3 iron and coal reserves in India ore Grade wise coal reserves in india Gradation of Indian non-coaking ccoal 1.4 DIFFERENT ROUTES OF SPONGE IRON PRODUCTION The process of DRI or sponge Iron making can be classified into different categories, which are as follows. 1.4.1 Rotary Kiln Processes Rotary Kiln Processes are very useful for Sponge Iron Production using non-coking coal as reductant. The Iron Ore in the form of lump or pellet is charged from one end with non-coking coal and heated from the other end, thus keeping counter current movement of raw materials and gases. The reduced ore comes out as product from opposite end .The Rotary movement of the Kiln requires good strength of raw materials during reduction. Generation of fines from poor raw material promote ring formation leading to poor performance and decreased productivity. 1.4.2 Retort Process In Retort process the reactor vessel is a retort where the charge is fed from top end remains stationary till discharged after reduction, thus it works in batches .a mixture of hot gases containing about 89% of reducing gases (75% H2 +14%CO) moves through ore bed held in three retort. The three retort works in cycle covering three stages, each approximately 3hrs duration. The first stage consist of heating and preliminary reduction of pellet charged. Once preliminary reduction is completed the reactor is switched onto second stage of redution by means of automatic valve manupulation during which bulk of reduction takes place. When most of the reduction is overed ,the reactor is changed to cooling mode and during all stages pellets remains statonary.the total process needs along time of about 23/24 hrs. 1.4.3 Rotary hearth process In this process iron oxide fines, coal fines and binder are mxed together and palletized .The green pellets are placed on a rotating hearth. As the hearth rotates around the circular furnace, the pellets are heated to 1250oC-1350oC and the iron