Evotech Pvt. Ltd., Sister Concern of Evcon Technologies, Providers of Evcon Turbo TMT System
Philosophy of Survival
In view of the on-going increase of metallurgical coke prices all over the world, the most pressing issue of the present steel market scenario is reduction of coke rate, and hence, the cost of production of hot metal.

The strategy chosen for reducing the coke rate is multifaceted, flexible and reliable. It embraces the most important aspects of iron making from top to bottom, up- and down-stream the process and the main idea is to incorporate the most effective cost reducing ideas and technologies into the project.

In order to illustrate several selected means to achieve the lowest coke rate, we take 100% lump iron ore operation (65% Fe content) with imported 12% ash coke and 750oC hot blast temperature as the basis for the analysis, because almost all Indian MBF Operators don't have any means of burden agglomeration and use metallic blast pre-heaters instead of Hot Stoves. Moreover, MBF Operators do not have coke oven plants of their own and they have to buy it from other suppliers. The coke rate of an average Indian blast furnace producing a foundry grade hot metal with such a burden and hot blast temperature is ranging from 650kg/THM to 750kg/THM (700 kg/THM on an average). The average daily rate of production of such an average Indian blast furnace having the above parameters is 1.7 t/m3/day.

Assume, it is a 450m3 BF with daily production of 765 tons of hot metal so that we can, step by step, analyze the technologies and techniques available to reduce the coke rate down and enhance the productivity.

Top Charging Equipment
Blast Furnace Operators know well how burden distribution is important and what impact it has on the rate of coke. Since coke is the most costliest amongst the raw materials, its contribution to the final cost of production of hot metal is the most sensitive. Therefore, it is very much essential how the top charging unit is distributing the raw material inside the furnace, how effective is the distribution, how effective it is in terms of gas distribution and to what extent this factors can reduce the coke rate.

Roughly, top charging units can be divided into three types: too bell system, Bell-less Top Paul Vurt make with a single inclined variable angle chute and Rotary Charging Unit with a five vane rotor.

The two bell system is known for more than a century and its limitations related to burden distribution are also known to every blast furnace operator (although it should be mentioned that not all of them exploited the bell system to the possible extent).

Paul Vurt BLT came into being at the time when some revolutionary ideas were required in the ages-old BF technology and it was welcomed as a panacea for many blast furnace deceases. However, despite of certain advantages of burden distribution, it didn't help in coke rate reduction and there are numerous studies proving that.

The Rotary Charging Unit by "TOTEM", Russia (which is available both in bell- and bell-less options) has proven to be the most adequate and reliable means of top charging. It is both fuel saving and productivity enhancing since its unique multi-layer and soft fan-like charging successfully proved the above statement both in Russia and India. The RCU, once installed, ensures 5% coke reduction and 5% productivity increase, which is contractually guaranteed by "TOTEM". The Bell-less Top Rotary Charging Unit by "TOTEM" is undoubtedly the best solution for optimal burden distribution, maximal gas utilisation and coke rate reduction.

Hence, we apply this rule to calculate the savings obtained through RCU:
700kg/THM - 5% = 655kg/THM
765THM/day + 5% = 803THM/day

Savings on coke (on the basis of the present coke prices equal to Rs. 12500) amount to Rs. 625/THM or Rs. 459375/day. The profit margin gained through productivity enhancement is also to be added. The cost of the bell-less RCU is a trifle compared to the savings and profits gained through coke saving, productivity enhancement and a significant reduction of the downtime compared to other types of top equipment.

Hot Stoves
Hot blast temperature, as one of the most important factors of iron making and instruments of coke saving, is another matter of concern, which attracts the attention of BF operators. Despite of differences of opinions on how much coke can be saved by increasing the hot blast temperature, an average figure approximated from different calculation approaches amounts to 2 - 3% (depending on coke quality) of coke rate reduction for each 100 degrees of hot blast temperature increase, or 8% for 400oC.

Unique Russian Top-fired Shaft-less Hot Stoves, designed and made commercially available by "SC KALUGIN", guarantee 1200oC hot blast temperature minimum on a continuous, maintenance-free basis. Moreover, because of its specific design features, the shaft-less stove requires 30 - 40% less refractory items compared to conventional stoves with internal or external combustion chamber and it can easily be accommodated within the shell of existing stoves.

Therefore, assuming at least 400oC increase in hot blast temperature achieved with the help of KALUGIN Hot Stove, we save 8% of coke and ensure 6% (min.) increase in productivity:
655kg/THM - 8% = 602kg/THM
803THM/day + 6% = 851THM/day

The savings of coke through the hot stoves of KALUGIN design amount to:

53kg x Rs. 12.5 = Rs. 662.5 x 851THM/day = Rs.563906 x 360 days = 20 Crore plus benefit from 48 tones of increased hot metal production.
Raw Materials
Pre-treated raw materials are undoubtedly an effective means of fuel rate reduction in iron making. Because of colossal present demand for lump iron ore around the world and shrinkage of the available stocks, utilization of iron ore fines becomes a critical issue of survival. Colossal volumes of iron ore dust rich in Fe has been generated and accumulated in India for years and this is the right time to make use of it and to survive in the environment of over-exaggerated and speculative coke prices. Hence, in order to reduce the cost of production through reduction of coke consumption, usage of processed burden materials becomes vital.
Cold-bound pellets
Cold-bonding pelletization is selected by us as a method of utilizing the so-called waste. Why cold-bound? Because at the initial phase of the plant operation, a cheaper option for cost reduction is chosen. Other effective coke saving technologies as sinter making can be added at the next stage, when profits are generated from the commissioned BF unit.
  • project cost of cold-bound pellet plant is by a factor less than that of a conventional sinter plant of adequate capacity;
  • project cost of cold-bound palletizing is several times less than of fired pellet process;
  • metallurgical features of cold-bound pellets, as proven by numerous studies, both laboratory and industrial-scale, are better than the characteristics of conventional sinter and fired pellets in terms of reducibility, hot strength, particle size distribution, fuel consumption, as well as the cost of production.
According to Russian operational standards, replacement of 15% lump ore by pellets ensures 3% coke rate reduction and 3% production enhancement. So, 15% Pellets contained in burden saves 3% of coke, or
602kg/THM - 3% = 584kg/THM
30% - 584kg/THM - 3% = 566kg/THM
45% - 566kg/THM - 3% = 533kg/THM

Introduction of 45% of pellets and briquettes into the burden according to Russian SOP provides for 10% increase in productivity. Therefore:
851THM/day + 10% = 936THM/day
DRI Pellets
DRI Pellet production is envisaged in the configuration of the pelletizing project as per our original direct reduction process in the Vertical Shaft Furnace. Daily production shall be about 100 tonnes of DRI pellets for sale or internal use. Before Steel Melting Shop comes into existence, the DRI pellets can either be sold on the market or added into the blast furnace burden. Once Directly Reduced Pellets are added to the burden, the coke rate is automatically reduced to an extent of DRI pellet content in the burden and metallization level of pellets.

We recommend usage of such pellets in BF process, since it is a very efficient way of coke rate reduction and productivity enhancement. The content of reduced pellets will be 80 - 100kg per tonne of hot metal and this can cut the coke rate down by 5% and improve the hot metal output by 4%, resulting in the following improvement of the operational parameters:

536kg/THM - 5% = 506kg/THM 936THM/day + 4% = 973THM/day
High Pressure Sintering Plant
Conventional sinter making is based on negative pressure atmosphere below the grate created by induced draft fans. The process is quite complex and very delicate. That kind of sensitiveness is a result of many factors affecting the quality of the final product. One of the most important factors is the pressure drop below the grate. It is almost impossible to avoid leakages in such a design. Therefore, the pressure drop is less and, hence, sinter quality suffers.

In order to resolve the above deficiency, High Pressure Sintering process in a pot type revolving machine has been recently developed in Russia by Dr. Boranbayev, MD, "TOTEM". It allows to significantly improve such main parameters of sinter as cold and hot crushing strength, reducibility, mean size and particle size, fuel requirement etc. Moreover, it is several times more productive, compared to conventional sinter machines having 72m2 working surface area despite much less surface area of sinter pots. The layout is very compact and need several times less area compared to conventional sinter plant of equal capacity. It requires less power, maintenance is much easier and less frequent so, the availability of the machine is more in high pressure sintering unit.

The unit of a single revolving machine can ensure production of 40 tonnes of superior quality sinter per hour (or 1000 tonnes/day) to replace lump iron ore completely from the burden. By introducing sinter and replacing lump iron ore and raw limestone completely from the burden, 10% coke reduction and 10% productivity increase can be expected:

506kg/THM - 10% = 455kg/THM 973THM/day + 10% = 1070THM/day
Nut coke, formed coke and coke briquettes
Any of the above types of fuels can be used for partial replacement of coke to the burden to the tune of 50kg/THM without any deterioration in the furnace behaviour and this is widely practiced all over the world. Forming and cold briquetting of coke breeze (which is substantially cheaper than BF grade coke) is an established and beneficial method to further reduce the cost of production of hot metal.

Hence the coke rate becomes: 455kg/THM - 50kg = 405kg/THM
Injection of additional fuels
In view of unavailability of natural gas in India for metallurgical purposes, the following three options are proposed:
  • Coal Dust Injection is a proven technology around the world with 1:1 replacement ratio. The average rate of coal dust injection is about 100kg/THM, although much higher volumes are also achievable with higher rates of oxygen enrichment. So:
    405kg/THM - 100kg = 305kg/THM

  • Coal Tar Injection, as well as furnace oil injection is worth implementing, since the coke replacement ratio can be as high as 1.4 with proper homogenisation and emulsification at the rate of 70kg/THM without oxygen enrichment. Thereby we get a reduction:
    405kg/THM - 70 x 1.4 = 307kg/THM

  • The third alternative is injection of Producer Gas with 0.3 replacement ratio and up to 250m3/THM rate.
    405/THM - 250 x 0.3 = 330kg/THM
The cheapest of the above three options is gas injection, although having the least coke replacement ratio. However, the plus point is that a cheap local non-coking coal can be used for the purpose.

The total project cost of the above cost reduction technologies will be ten times less than the profits gained through them. We assume that cost of production with the above technologies will be about Rs. 6500/THM. The present pig iron price is roughly Rs. 12000/ton. Thus, the profit margin is about Rs. 5500/THM

Ultimately, if the above coke rate reducing and productivity enhancing means are implemented, one can bring the coke rate down by 370 to 395 kg/THM allowing to save Rs. 4750/THM (or Rs. 1829 700 000 per annum) and increase the furnace performance by 40%, or 305t/day, (the profit margin of an additional hot metal output will be 305THM x 360days x Rs. 5500 = Rs. 603 900 000 per annum).

The total benefit, i.e. savings obtained through coke rate reduction and productivity increase shall amount to Rs. 2434 Crore/per annum, reaching an exemplary international level of 2.37 productivity, low production cost and competitiveness.

We strongly believe both in the viability and necessity of such a project profile since all Indian smaller blast furnace operators having no coke batteries of their own, no palletizing or sintering plants, with ineffective bell charging system and extremely low blast temperatures will have to shut the business down in the nearest future because of metallurgical coke and lump ore shortage combined with highest-ever raw material prices. In combination with inefficient and out-of-date technologies and inability to compete with larger integrated steel plants, it will be next to impossible to survive under such conditions.
Metallurgical Coke
Provided a coke oven plant is added to the iron making unit, the above calculations of savings and profits can be doubled, since coke prices are roughly twice higher than the present imported coking coal prices. Although a coke oven plant adds significantly to the total project cost, the final hot metal production cost will compensate the additional expenditures required for coke oven plant installation. Assuming the above daily hot metal output with the given tentative coke rate, a 500t/day capacity Coke Oven Plant of non-recovery type would be required.
Captive Power Plant
Since purchased power also contributes greatly to the cost of production and power cuts occur quite frequently practically in all states, 20MW Captive Power Plant using generated process gases becomes a necessity of the day to further cut the cost of production down and be independent from the state power grid to ensure an uninterrupted technological process with cheaper source of own power. Moreover, it is logical and extremely profitable to fully utilize own power sources and process gases from MBF and Coke ovens will help make the iron making plant techno-economics more efficient.

From this point, the last and the most decisive step forward is to make the plant completely integrated by adding a steel making unit comprising of 100 ton Electric Arc Furnace, 2-strand Billet Caster and a Wire Rod Mill to be taken up in Phase III. It is obvious that semi-products like pig iron or steel billet provide for less profit than a finished product. Hence, the strategy should be aimed at further integration of the Works to become more competitive on the market. In addition to this, it is more logical to make steel and roll own billets, rather than sell it on the market and this is the philosophy most producers follow nowadays.

So, it is assumed that the total project can be taken up in three successive phases.

Project Cost Rs. in Crores
Phase I : MBF 75
Pelletizing Plant (including DRI) 25
Phase II: HP Sintering Plant 35
NR Coke Oven Plant 15
Captive Power Plant (20MW) 20
Phase III: Steel Melting Shop 50
Billet Caster 10
Rolling Mill 25
Total Project Cost 320
1200 TPD Steel Plant Project Annual Production
1 X 450m3 MBF 360000 tons of hot metal
1 X 800 TPD Pelletizing Plant 290000 tons of pellets (0.60% Fe)
1X 100 TPD DRI Plant 36500 tons or reduced pellets 92% met.
1 X 1100 TPD High Pressure Sintering Plant 400000 tons of sinter (0.57% Fe)
1 X 500 TPD Non-recovery type Coke Oven Plant 182000 tons of coke (12% Ash)
1 X 100T EAF (100t X 12 heats/day) 430000 tons of steel (80% hot metal, 10% scrap, 10% sponge iron)
1 X 2-strand Billet Caster 415000 tons of billets
1 X 4-strand Wire Rod Mill 400000 tons of TMT bar & rod
2 X 20MW Captive Power Plant 350 GW