Studies on Improving the Efficiency of DRI Technology and Solid Waste Management

In the present scenario India is the largest producer of sponge iron (DRI) in the world. DRI

is the best feed/substitute of scrap in steel production, so in the coming years the demand of

DRI will grow very fast. The future of DRI in India is quite promising. Steel revolution in

India is started with the resurgence of innumerable small and medium scale steel industries

and DRI industries especially in Orissa, Jharkhand, Chhattisgarh & Maharashtra region

(Coal Based DRI) and Karnataka & Goa (Gas Based DRI).

These low budgeted iron and steel sector always aimed at economical viability of

technology and cost reduction. This work is done keeping in view the survival of small and

medium scale (50-150 TPD) DRI plants.

Lot of fines and solid waste are generated during mining, ore preparation sources and also

in intermediate processing. If these fines and waste can be utilized indigenously it will be a

great contribution towards Indian economic growth.

Pelletization technology on small and medium scale is still under development for hematite/

magnetite ore in Indian situation. Iron ore pelletization has been identified as an

economically viable and alternative substitute for feed ore in steel making process

especially for DRI.

Due to shortage of good quality iron ore lumps/fines alternative technology on the basis of

low grade iron ore feed, beneficiation is a good agreement (Indian Iron Ore with less than

58% iron is discarded as waste as per IBM standards). Iron ore is being beneficiated all

over the world to meet the quality requirement of iron and steel industry. However each

source of iron ore has its own peculiar mineralogical characteristics and requires specific

beneficiation and metallurgical treatment to get the best product out of it. The choice of the

beneficiation treatment depends on the nature of the gangue present and its association with

the ore structure as a result in Indian scenario economical technological solutions are on

demand for utilizing low grade ores. In the present situation integrated low grade iron ore

beneficiation with pelletization is an independent important area economically viable in

DRI technology.

Another important and very critical issue in Indian DRI technology is environmental

pollution control problems especially neglected by small and medium scale DRI plants.

Coal gasification using medium quality coal is a solution of existing DRI plants and also for

new upcoming plants.

A techno economical feasibility study is being planned for making the above issues

commercially possible. It is proposed that initially certain laboratory studies would be

required to find out actual benefits.

Present work

Originally when DRI plants are commissioned with exploring suitable process technology

based on quality iron ore lumps/fines. In short period of time, availability of quality ore

fines too has become questionable, now it is accepted that the plant should be proposed and

designed on the basis of low grade iron ore feed and beneficiate the same.

During the detailed study it was observed that iron ore, coal, flux fines/micro-fines are

generated in huge quantity during the different metallurgical/mining operations. The

recycling of waste materials via the pelletization process can achieve a saving in the cost of

raw materials and reduction in pollution.

The present work is carried out initially with material characterization in the laboratory and

by fabrication of a disc pelletizer, for production of different varieties of pellets. The work

presented in this study is planned and carried out in order to establish a link between the

present practices by DRI producers and possible improvement in them.

The initial information of DRI technology and related issues are discussed in Chapter 1.

While the detailed literature investigation on the topic is elaborated in Chapter 2, which

reveals that there is a bright scope on this topic and hence to tackle related problems with a

systematic approaches. The exact formulation of the proposed work as mentioned above to

achieve the improvement in the DRI practices and its plan of action is derived.

Based on the initial result of material characterization, beneficiation pelletization on

different areas, experimental work was planned and details of this is discussed in Chapter 3.

Experimental work is carried out in three stages:-

1. Material characterization of solid waste/fines and utilizing them in pellet making.

Mechanical and metallurgical properties were studied and compared with lump ore.

2. Achieving pelletization process optimization by combining this with ore beneficiation

and techno economical feasibility of this in DRI technology studied.

3. In combination with the fabrication of a laboratory setup the detailed coal gasification

study in and around industries is conducted to tackle the environmental issues in DRI

technology.

In Chapter 4 in depth analysis of results of experimental work and discussions are presented

in the broad areas of:-

Optimization of solid waste/fines, recycling by beneficiation and pelletization and its

applicability.

Detailed analysis of optimized ore beneficiation technique combined with

pelletization in DRI process.

Techno economical viability and feasibility of coal gasification unit combined with

DRI to reduce the environmental issues in existing plants and also in upcoming DRI

plants.

Prior to optimization of beneficiation and pelletization process initial materials

characterization was carried out on various iron ores and solid waste generated during

different mining and metallurgical operations in steel industries. From this investigation

problem of input material was analyzed and optimized condition/parameters were studied on

different pellet sample. Study of various parameters of standardized flow sheet of ore

beneficiation as well as the mechanical properties and metallurgical properties like swelling

behavior and reduction studies on pellets and lump ore were carried out.

The detailed analysis of the above work was resulted in optimizing the conditions of

beneficiation and pelletization of fines of ores, coal, solid waste and then correlated and

compared it with lump ores. From this data then the graphs and flow sheets were developed

which provides a ready reckoned for technologist in DRI making.

A techno economical feasibility analysis is conducted for integrated ore beneficiation with

pelletization in DRI plant. Based on analyzed generated data it is observed that ore

beneficiation plant in combination with pelletization is a viable solution in the present

situation where low grade iron ores are abundantly available. For small and medium scale

DRI plants it is advised to come together and form a cluster together (i.e. for 1500 TPD DRI

plant capacity) and install ore beneficiation combined with pellet plant that can be used

economically in DRI for future economics.

The important outcome of present lab simulation and onsite work which highlights the

viability of coal gasification unit in DRI to minimize the environmental related issues in the

coal based DRI plants of this region.

The detailed analysis of DRI technological performance in steel making has resulted in some

very useful outcome, which provides proper economical solutions for small and medium

scale DRI industries of this region.