March 201639

PART-II

- N. M. Rao, Consultant (I&S)

Steelmaking Process Route - Options for India

The Way Forward

It has been agreed by 196 nations in Paris on 12-12-2015 that the average increase in global temperature shall be limited to well below 2°C from the levels prevailing in pre industrial years. It was also agreed that efforts shall be made to limit the increase to 1.5°C in order to significantly reduce risks and impacts of climate change. However, it was accepted that in developing countries like India, emissions have not yet peaked. It was therefore agreed that in developing countries, the emissions should peak as early as possible and then there should be rapid reduction.

Therefore, India has to not only take actions for reduction in intensity of emissions, but also chose such processes (for creating additional capacity) which generate very low greenhouse gas emissions. EAF steel making with 100% scrap is the best option for this.

Even though steel is 100% recyclable, it has a long life also. Internal generation of scrap has come down due to technological improvements in steel making. Hence, available scrap will not be able to sustain the option of 100% scrap usage. May be, an industry average scrap usage of around 30% can be maintained in India in the short to medium term.

The BOF process of steel making is highly efficient and productive but depends on the availability of liquid iron. The process gives best results with 90% liquid iron and 10% scrap. Presently, blast furnace is the main supplier of liquid iron. In India, blast furnace accounts for over 93% of liquid iron production, the balance being the contribution of Corex process. While, blast furnace is also efficient and productive, it emits considerable greenhouse gases. Hence, steel industry has to seriously look for alternate iron making processes so that proportion of blast furnace

March 201640

iron in steel making can be substantially reduced. Simultaneously, efforts should be made to further improve the performance of blast furnaces in respect of coke rate and productivity. Integrated steel plants are operating 47 blast furnaces of which 23 are of less than 2000 m³, 14 of 2000-3000 m³, 5 of 3000-4000 m³ and five have more than 4000 m³ volume. Another five furnaces of +4000 m³ volume are likely be commissioned in 2016/2017. On an average, the productivity of Indian furnaces is about 1.8-2.0 t/d/m³ (global- >2.5 t/d/m³) and depending on PCI usage, coke rate is 450-500 Kg/thm (global-~300 Kg/thm) In order to keep the greenhouse gas emissions within the acceptable levels, following steps may have to be taken in respect of blast furnaces.

l During capital repairs, reconstruct the small furnaces so that they have a volume of minimum 2000 m³

l Maintain minimum PCI rate of 150 Kg/thm in all furnaces and make efforts to increase this to 200 Kg/thm

l Suitably upgrade other operating parameters like blast temperature, top pressure, oxygen enr i chment o f b las t , u se o f agglomerated burden etc . to achieve productivity of 2.5 t/m³/day and coke rate of about 350 Kg/thm

l Adopt in all plants, waste recovery from sinter coolers & blast furnace stoves, top recovery turbines, heat recovery from molten slag etc.

In the long run, we may have to accept that

steel has to be made without blast furnace. The ULCOS-BF process, under research by a group of 10 European countries, involves capture & storage of CO2, gas recycling at two levels in the furnace, use of oxygen instead of hot blast (to make it nitrogen free) etc. For this to succeed, solutions have to be found for issues of space, capital, investment risk, safety & transportat ion r isk, lack of f inancial investments etc.

(source : www.researchgate.net).

Other source of liquid iron is alternate processes of Corex and Finex, which have now been commercially proven viable. In India, Corex process has been adopted by JSW at their Torangallu plant and by Essar steel in the Hazira plant. Total estimated capacity is 4 MTPA. Uttam Galva Metallic is considering setting up 1.5 MTPA Finex plant in their works at Wardha. Indian companies should adopt these processes at least partially in the brown field expansion as well as in green field plants. They use non-coking coal (Corex uses coke to the extent of about 20% of total fuel) and use oxygen instead of hot blast and hence greenhouse gas emissions are lower compared to the blast furnace process. As of now, in both the processes, 1.5 MTPA production units are available. Another iron making process, which has found commercial acceptance, is ITmk3. The size of the production unit is 0.5 MTPA and the product is in solid form and is called iron nuggets which have high Fe content. This will be suitable for medium size plants based on EAF with a capacity between 0.5 MTPA and 1.0 MTPA. They may consider this process

instead of MBF.

In view of the problems associated with the availability of liquid iron, India should have a relook at expanding steelmaking capacity through the BOF process. Even though electric steel making contributes 60% of total crude steel production in India, share of EAF in this is only 40% and balance 60% is contributed by induction furnaces. Future steel making should essentially be through EAF process. As mentioned earlier, there have been many technological developments in the EAF process and today, the process is highly efficient and productive. Indian industry should make efforts to reach the international performance levels in respect of tap to tap time (50 minutes) and power consumption (~300 Kwh/tls).

Metallic input for EAF should preferably be sponge iron (DRI/HBI) and scrap. Recently, charging of blast furnace iron has been resorted to by EAF plants in India with a view to reduce power consumption. With the adoption of higher size EAFs and introduction practices like scrap pre-heating, hot DRI charging, oxy-fuel burners, bottom stirring by inert gas, eccentric bottom tapping, foamy slag practice etc., EAFs can achieve low power consumption even without the use of liquid iron. However, if Corex or Finex plants are available, liquid iron from these units could be used. These units emit lower emissions compared to the blast furnace.

Gas based DRI is preferable compared to coal based DRI due to higher metallisation and higher carbon content. In India, utilisation of gas based DRI plants has come down below 30% due to non-availability of natural gas. With the Turkmenistan-Afghanistan-Pakistan-India (TAPI) gas pipe line expected to be commissioned by December, 2019, India will get 38 mmscmd of natural gas from Iran. This should ease the situation for the sponge iron sector. Further, synthesis gas from coal gasification and off gases from Corex and Finex processes can be also used to produce DRI and the quality of the product is comparable to that based on natural gas. In future, gas based DRI will again have a bigger role. These plants use iron ore pellets as feed.

Some companies like JSPL Raigarh, Bhushan steel, BPSL, Monnet Ispat, BMM Ispat, Usha Martin, Sunflag, Jai Balaji, Jayaswal NECO, Adhunik etc. have set up coal based DRI plants. These plants along with merchant producers like Tata Metallic use + 200 TPD kilns, adopted waste heat recovery and incorporated other technical features to make quality product, particularly in terms of

Technology

March 201641

PARTICULARS 2025 GOAL

Table-4

S.N.

1.

2.

A

B

C

3.

A

B

C.

4.

A

B

C

D

E

F

5.

A

B

6.

7.

Crude Steel Capacity

Crude Steel Production

300

270

Crude Steel Production through BOF (37%)

Crude Steel Production through EAF (50%)

100

135

Crude Steel Production through Induction Furnace (13%)

Metallics for BOF Steel Making (90% Yield)

Blast Furnace Hot Metal in the Above (80%)

Hot Metal from Corex/Finex in the Above (11%)

Scrap in the Above (9%)

Metallics for EAF Steel Making (88% Yield)

NG Based DRI in the Above (10%)

SYN Gas/Corex Off Gas Based DRI in ihe Above (10%)

Coal Based DRI in the Above (15%)

Blast Furnace Hot Metal in the Above (16%)

Hot Metal from Corex/finex in the Above (10%)

Scrap in the Above (39%)

Metallics for Induction Furnace Steel Making (86% Yield)

Coal Based DRI in the Above (50%)

Scrap in the Above (50%)

Total Metallics Required

Metallics Ratio (%): BF Hot Metal (113 MT)Corex/Finex Hot Metal (28 MT)

NG based DRI (15 MT)Syn gas/Corex Off Gas Based DRI (15 MT)

Coal Based DRI (43 MT)Scrap (91 MT)

35

111

88

13

10

153

15

15

23

25

15

60

41

20

21

305

37.09.24.94.9

14.129.9

degree of metallisation. Performance of 1000TPD unit developed by

Outotec for an Indonesian plant should be studied in detail by Indian companies and if found satisfactory, 500 TPD and 1000 TPD units should be the future norm. This will improve productivity & quality and these are known to be environmentally friendly. Indian coals are high in ash. They should be either beneficiated or better quality coal imported.

About 33% of crude steel in India is made through Induction furnaces. They have an estimated total capacity of about 35 MT. They control about 70% of long product market and mainly cater to the local demand. They have all India presence and have the advantage of low capital cost, low refractory cost and they can be

run by people with low technical skill. However, they are essentially melting furnaces and refining operation cannot be undertaken. They may find it difficult to compete with EAF and BOF plants on quality aspects. Also, they get low yield and EAFs have overtaken them in respect of specific power consumption. Therefore, it will be prudent not add to the capacity of induction furnace steel making. Existing players have to modernise to the extent possible. Small coal based DRI plants (<200 TPD), now feeding induction furnace units, have to think their survival strategy in the changing scenario.

A s p e r C e n t r e f o r S c i e n c e a n d environment, they cause considerable pollution. MBFs have to also modernise to reduce carbon dioxide emissions.

Conclusion

Based on the discussion in the previous section, suggested process wise production of crude steel and requirement of Iron (BF/DRI) & scrap for the year 2025 is shown in table-4. Capacity of crude steel is as per the projections made in the draft national steel policy, 2012. Capacity utilisation has been assumed at 90%. In working out this, capacities already available in various processes have been taken into account. All figures are in million tonnes.

To ensure 30% scrap usage on the overall basis, Government has to formulate a national metal recycling policy so that recovery, processing and recycling of scrap are done in an organised manner. Proportion of EAF process is proposed at 50% in 2025 against 23% in 2014-15. Proportion of both BOF and IF will accordingly come down. Higher usage of DRI has been considered compared to 2014-15. By 2050, induction furnaces should be phased out completely and 75% crude steel production should be through EAF process and balance 25% through BOF.

Overall scrap usage should be aimed at 50% minimum. Between 2016 and 2050, there will be many technological developments in all processes and hopefully, India will be able to substantially reduce the greenhouse gas emissions as per the commitment made in 2015.