Production of steel is the biggest metallurgical industry in the world. Steel in different forms is meeting the fast-growing needs of human beings in various sectors. The major raw materials required for iron and steel production are iron ore, coal, limestone, water and energy.
Most of the steel produced at present in the world is through Blast Furnace (BF) – Basic Oxygen Furnace (BOF). Iron ore, coke produced from coking coal and limestone are used as raw materials to produce pig iron in BF. The pig iron thus produced is further refined to produce steel, mainly in BOF.
It has been reported that more than 800 BF are operating to produce nearly 65% of iron in the world and the rest are produced by other methods. The reason is that BF is considered to be versatile in terms of operation, energy efficiency and quality of iron produced. However, the BF – BOF route for making steel involves high investment cost, long lead time and difficulties in producing suitable raw materials like coke from coking coal, high grade iron ore and limestone. Further, with increase in production of iron and steel, coking coal reserve is getting depleted very fast. BF can only accept the coke obtained from coking coal because of its special properties.
Global steel production has reached 1808.6 million tons (MT) for the year 2018. Out of this, China produced 928.3 MT and India produced only 106.5 MT during the same year. The World Steel Association (WSA) shows that India is languishing at the bottom rung of the consumption ladder with a per capita consumption of only 70.9 Kg, whereas the global figure is 224.5 Kg
To meet the increasing demand of steel with fast industrialisation, India has to produce much more steel by utilising the available resources. The most important bottleneck in this regard is non-availability of coking coal in the country to produce iron in BF. The reserves of coking coal in the country are not adequate for iron making in BF. It is reported that the total coal reserve of India is 315.148 billion tons. Out of this, primary coking coal is 5.313 billion tons, medium and semi-coking coal is 29.219 billion tons, non-coking coal is 279.028 billion tons and tertiary coal is 1.5888 billion tons. Out of the total reserves of coal in the country, coking coal is only 20% and the rest is low-grade non-coking coal. Therefore, India has to import a large quantity of coking coal to produce iron in BF by spending a huge amount of foreign exchange.
In view of this, it is necessary to produce iron, which is the main raw material for steel, by an alternate route, that is Direct Reduction Iron (DRI). DRI is also popularly known as sponge iron because here, unlike in BF, iron is produced without melting it in a porous form. In this case, unlike in BF, iron is formed in solid state from the iron ore lumps or pellets (formed out of iron ore fines) using hot reducing gases or non-coking coal. Both the processes are commercially available. In the gas-based process, the reducing gas is produced by chemically reforming a mixture of natural gas (containing mostly methane) and flue gas from the reducing furnace to produce a mixture of hydrogen and carbon monoxide.
Typical examples of gas-based processes include MIDREX and HYL. This method is preferred in countries where natural gas is abundant and cheap. In the coal-based DR process, reducing gas is produced from non-coking coal in the reduction zone of the furnace, typically a rotary kiln.
(Sponge Iron Plants)
Typical examples of coal-based process include SL/RN and ACCAR processes. Such coal-based sponge iron making from iron ore is popular both in India and China. However, in the world, almost 80% of sponge iron is being produced by the gas-based DR process. Both the gas and coal based DRI technology are gaining importance due to comparatively less investment cost, flexibility in using raw materials like cheap iron ore fines, non-coking coal and natural gas. Generally, the scale of operation of gas based DRI is 0.82 – 1.2 MT per annum but coal based one is comparatively smaller (0.3 to 0.15 MT per annum).
According to a survey of the Indian sponge iron industry prepared by Joint Plant Committee of Ministry of Steel, Govt. of India during 2005 – 2006, there are three gas-based sponge iron units – Essar Steel, Vikram Ispat and Ispat Industries. All are in the western region mainly due to proximity to natural gas sources. At that time, their report showed that the total number of coal-based sponge iron units are 147 and the concentration of the units is maximum in Chhattisgarh (38) followed by Odisha (33) and West Bengal (30). The total capacity is reported to be about 11MT of sponge iron; in Chhattisgarh 4.5 MT, followed by 2.2 MT in Odisha and 1.6 MT in West Bengal.
In India, most of the sponge iron producers do not have captive mines of any of the raw materials like hematite, non-coking coal and limestone, which are used for sponge iron production. Therefore, they fully depend upon other agencies to get their raw materials. Now, the major constraints being faced by these industries are high price and non-availability of quality raw material. The right grade hematite of proper size has become scarce and very costly. Most of the high-grade non-coking coal has been earmarked for thermal power plants and only inferior grades like ‘F’ and ‘G’ are available, that too, in a limited quantity. Most of the units are producing sponge iron much below their capacity mostly due to want of proper raw materials.
In India, due to the availability of a large amount of high-grade hematite and non-coking coal, the sponge iron industry has tremendous scope for further development. But various problems being faced by the industries at present have made this industry sick. In the years to come, we need large amounts of steel. It is essential to promote both non-coking coal and gas-based sponge iron industries. These industries besides supplying enough sponge iron for steel production, can provide a lot of employment to skilled and semi-skilled people in the country. In view of this, it is highly desirable to promote these industries by implementing the following programmes:
(a) In view of the non-availability of high-grade lumpy iron ore and because of its high cost, it is appropriate to utilise the cheap and abundantly available low-grade iron ore fines after suitable beneficiation and then agglomerating those as pellets. In this way, the cost of the major raw material, the iron ore will be cheaper than the lumpy iron ore and also with better reducibility. This practice is being followed in many DRI units in the world as well as recently in India by some units. Sponge iron units, which are in small and medium sectors as per their need can develop the facilities for beneficiating low- grade ores and pelletising those in a co-operative manner to make the units techno-economically viable.
(b) Similarly, the very low-grade coal (F / G grade) can be upgraded to suit the requirement of the rotary kiln DRI units through washing and beneficiation. Again, coal washing units can be set up in a cooperative manner by the concerned companies to meet their requirements. The technology is well known and already, there are a number of washeries of non-coking coal in India to utilise the very low grade materials.
(c) All sponge iron units should have captive power plants to meet their energy requirements. As a lot of heat is lost in DRI units, Waste Heat Recovery Boiler (WHRB) captive power plants, with electrostatic precipitator should be installed. In such captive power plants, the waste coal fines and char fines of the concerned unit can also be utilised. This would be the best method of waste management.
(d) The water requirement of each of the DRI units can be met by harvesting rain water both on surface as well as recharging the aquifer, inside the plant premises or nearby areas. This would enable the sponge iron units to be independent of outside water sources. Further, they should recycle the used water to minimise the environmental pollution and maximise the conservation of water.
(e) By adopting various pollution control measures, which are already available in the country for DRI units, the plant area can be kept pollution free. For example, it is possible to bring down the dust emission from about 12 tones to only 58 Kg per day of a 100 tons per day (TPD) kiln by adopting various air pollution control measures.
In this way, by promoting the establishment of a large number of small and medium scale DRI units, it would be possible to extract good amount of sponge iron from low-grade iron ore and non-coking coal as well as natural gas to boost the production of steel. At the same time, the sponge iron units can employ a good number of skilled and semi-skilled persons. In this regard, both the Central and concerned state governments have a significant role to play. They should take necessary steps to create a congenial atmosphere for promoting the establishment of a large number of sponge iron plants to boost the production of steel in an environment-friendly atmosphere.
(The writer is former Director General, Council of Scientific & Industrial Research, India;
former, Planning Board Member, Government of Odisha; Founder Chairman, Institute of Advance Technology & Environmental Studies (IATES) and Founder President, Natural Resources Development Foundation (NRDF)