Technological conjunction of Iron & Steel Making At Essar Steel India Ltd. Hazira, Gujarat

Transcription

1 Technological conjunction of Iron & Steel Making At Essar Steel India Ltd. Hazira, Gujarat Authors: Hitesh Sheth & Neeru Singh ABSTRACT Hazira steel plant of Essar Steel India Ltd (EStIL) has been playing a major role in making Gujarat a global industrial hub by supplying its products both for exports and in domestic markets. It is specially known as high quality steel maker in all the segments that it serves, be it White & Yellow Goods, Capital Goods, Shipbuilding, Pipeline for Sweet & Sour Gas, Electrical Steel, Dual Phase Steel and prestigious Automobile Sector. It has taken a long stride in serving the Defence Sector as well. Essar s captive port-based Hazira plant is a unique facility in the world encompassing all fundamental technologies of Iron and Steel Making at single location. Foremost, three iron making technologies Midrex HBI/DRI Modules, Corex and Blast Furnace. These technologies give the plant tremendous flexibility in the way raw material and energy inputs are chosen or proportioned. Secondly, the DC- EAF and CONARC routes are followed as prevalent steel-making technologies, which tend to utilize varied percentage of DRI + scrap + Hot metal. Today gas based DRI EAF route has become unviable due to scarcity and high price of gas, so more of Hot-metal (BF+ Corex) CONARC route is utilized. The company is in fact envisaging replacement of DRI units by a new Blast Furnace and EAFs by LD converters. Lastly, as an extension to Iron & Steel manufacturing, Essar makes pipes and extra wide plates as well as hot rolled, cold rolled, galvanized and colour coated steel through Conventional or Compact Strip Caster and this is an accolade to the entire manufacturing chain. INTRODUCTION In India, Crude steel production grew at the rate of 8.2% per annum from million tonnes (MT) in to 81.4 MT in Steel demand has grown by 3.3% to 76.2 MT in 2014 due to an improved outlook for the construction and manufacturing sectors. Steel demand is projected to grow by 4.5% in The target of 300 MT by 2025 is realizable, but by no easy means. A realistic action plan needs to be prepared and executed with focused efforts. In India availability of plenty of iron ore reserves, comparatively low wages, a growing market, HR resources and a strategic location for exports act as supporting factors for green-field and brown-field projects in Steel sector. Pros and cons walking side by side the obstacles include ore & coal availability, fluctuating NG prices, land availability and full capacity utilization because of varying parameters. This demands a flexible selection of technological process. Key drivers for the steel industries are Demand and the Cost of Bulk Raw Material. India's inherent advantage is going to make it a natural choice / place / economy to become a 300 MT player by The argument is supported well owing to following facts: Being globally 5 th highest in iron ore reserves. Having lowest labor cost in the world Technological conjunction of iron & steel making technologies at Essar Steel India Ltd 1

2 The Steel industry having a good mix of public & private firms with considerable experience. Rising steel consumption in the sectors of : Construction : 50% population still resides in kachha / semipucca houses. Steel to cement ratio for construction; wherein India is 0.3, way below USA 1.19 & Japan Infrastructure : Lowest in per-capita power consumption (672 kwh/cap v/s 3388 kwh/cap in China). Railway length per-capita is very low (53 km v/s 74 km in China, 716 km in USA). Steel Intensive Industries : Capital goods form ~20% of India's import bill; Import dependence >50% for machine tools, earth-moving equipment & metallurgical machinery. Other industries like auto, spares, ship-building etc. can be further developed. Export : Steel-oriented exports constitute ~17% of India's exports, against >50% for China Potential to develop export orientation in industries like auto, ship-building, consumer products, mechanical appliances etc. MENA, Rest of Africa & ASEAN currently import ~70% of finished steel requirement - Demand projected to rise ~1.7x by 2025 to ~220MT. Opportunity to serve these countries competitively due to low cost curve, geographic proximity. Green shoots are already visible for the growth. In fact, the wide gap in demand and supply has encouraged a number of steel companies to build new capacities. The current capacity of the steel industry as a whole is 81.6 million tons per annum. Expected 200 million tons by 2020 will be achieved through green-field projects and trend is going to continue. With current global scenario the prices of the commodities are dynamic in nature. The viability of steel plant is highly dependent on the cost of following key critical raw materials: 1. Iron ore; 2. Coal / Coke; 3. Natural Gas; 4. Electrical Power. This needs promotion of flexibility in the process route wherein, cheaper raw material utilization without affecting the productivity becomes the key towards making steel business sustainable. Essar s captive port-based Hazira plant is a unique facility in the world encompassing all fundamental technologies of Iron and Steel Making at single location. The Steel Complex at Hazira (depicted in Fig.-1) is an integrated unit having proven types of Iron Making & Steel Making - State of the Art- technologies and offers flexibilities in the selection of appropriate process route based on cost of Power, Coal and Natural Gas price. These technologies give the plant tremendous flexibility in the way raw material and energy inputs are chosen or proportioned. Technological conjunction of iron & steel making technologies at Essar Steel India Ltd 2

3 Fig.-1 Also, all the stated plants have developed in-built flexibilities and process stabilization by using varieties of input materials Iron Bearing Material Ore / Pellets / Lump Ore with Fe content ranging from 62.5 to 66 %, Wide ranging types of coal for Corex, Innovative sources of Coke for BF and Operating Midrex at varying levels as per NG availability. Steel Making with Hot Metal, Pig Iron, DRI (Cold, Hot and Briquettes), Scrap (internal / external), Pot Skull (BF / Corex / Steel Plant returns), Oxides, fines etc. Casting need base through conventional, vertical or strip caster. TECHNOLOGICAL UNITS & PROCESS Individual Plants with their unique features on technology, process and best performance: A. Iron making 1. Direct Reduced Iron production through Midrex Process: Mod 1-6 (7 Million MTPA) Direct Reduced Iron (DRI), also known as Sponge Iron, offers an alternative steel production route to BF-BOF and Scrap-EAF routes. In DRI, iron ore is reduced in its solid state unlike BF process where a liquid metal is formed during reduction. Technological conjunction of iron & steel making technologies at Essar Steel India Ltd 3

4 The technology used for DRI production is MIDREX, refer Fig.2 that utilizes natural gas as fuel and consists of shaft furnace type reactor. The products are in hot DRI, Cold DRI and Hot Briquetted Iron form. Hot DRI is immediately transferred to the EAF melt shop, the heat from the direct reduction process lowers the cost of melting DRI in the EAF, significantly cutting the energy costs and electrode consumption. Fig.-2 Each of the modules were modified with in-house design engineering to achieve the rated capacity from 57 tph to 100 tph. Some of the modifications are as mentioned below: 1) Installation of additional reformer bays to enhance the reforming capacity. 2) Changing all the compressor and fan motors with increased rated power along with gear box and fan modifications. 3) Injection of Oxygen in the process gas to increase the reaction temperature in furnaces. 4) Improving the CCS of pellets along with lime spraying to withstand higher reaction temperature. 5) VPSA systems to introduce Corex gas into Midrex modules for full utilization of Corex gas from Corex modules. 2. Blast Furnace is the most proven iron making route and approximately 70% of the global steel production involves the use of BFs. The blast furnaces chemically reduce and physically convert iron oxides into liquid iron called "hot metal". The blast furnace (refer Fig.-3) is a huge, steel stack lined with refractory bricks, where iron ore, coke and limestone are charged from the top, and preheated air (1150 C) is blown from the bottom called tuyères. The raw materials require 6 to 8 hours to descend to the bottom of the furnace where it becomes the final product of liquid iron and slag as the byproduct is also generated. These liquid products are drained from the furnace at regular intervals. The hot air that is blown into the bottom of the furnace ascends to the top in 6 to 8 seconds undergoing various chemical reactions. Once a blast furnace is started it continuously runs for more than ten to fifteen years besides small shut-down to perform planned maintenance. Sizes of BFs installed cover a very wide spectrum, ranging from less than 100 m 3 to more than 5000 m 3. Larger BFs have less heat losses and enable a cost effective installation of heat recovery equipment. At EStIL, currently we have 2200m 3 (effective volume) furnace. Technological conjunction of iron & steel making technologies at Essar Steel India Ltd 4

5 Best achieved performances: Fig.-3 Day production : 6066 tpd Monthly production : tons Day productivity : 3.17 thm/m 3 /day Month Productivity : 2.88 t/m 3 /day Month O2 enrichment : 4.52% TRT power generation for the (May 2013) month : 6.93 MWh 18.5 MWh power generation utilizing with surplus capacity of BF boiler 3. COREX is one of the commercially and technologically established alternate route of Iron making. COREX name is derived from Coal + Reduction & suffix X. COREX (refer Fig.-4) is a two-stage process, reduction and smelting. Oxides of iron in the form of Lump ore and pellets along with fluxes are fed into the upper reactor which is named as Reduction Shaft. The DRI and calcined fluxes produced in the Reduction Shaft are discharged through DRI screws placed at the bottom of the shaft and are charged to the lower reactor called Melter Gasifier for smelting. Raw untreated non-coking coal is fed directly into the Melter Gasifier. Pure oxygen, blown through the tuyères, burns the fixed carbon of the coal and generates heat and gases. The hot gases ascend through the char bed. The sensible heat transferred to the char bed is utilized for melting iron and slag and other metallurgical reactions. The hot metal and slag formed in the process are collected in the hearth and tapped periodically. The hot gases generated in the Melter Gasifier exits at temperature of 1030 C contains dust particle, which are separated in hot gas cyclones. The dust collected in cyclones is recycled back through dust burners. The dust is burnt by injecting oxygen through dust burners, which ensures the heat requirements in Melter Gasifier free board zone for coal devolatilization. Technological conjunction of iron & steel making technologies at Essar Steel India Ltd 5

6 Advantages of COREX technology over other Iron making processes are: It is a two-stage process, Reduction and Smelting. It is a clean iron making technology, which is flexible in terms of operation. Faster quality correction feasible. Various fines such as iron bearing fines, limestone & dolomite fines can be directly used in to the furnace. About 10% of the total iron bearing material can be replaced with direct use of Iron bearing fines. The gas coming out, as by-product is a clean gas having very high calorific value i.e. ~ Kcal/Nm 3. Monthly Best Performance: Fig.-4 Production of Tons. Lowest Specific Oxygen consumption rate of 503 Nm 3 /thm. Operated at Lowest Coke Rate of 102 Kg/thm. Achieved Lowest fuel Rate of 900Kg/thm. Usage of Thermal steam coal such as South African coal usage initiated within a week of COREX commissioning. The usage of South African Coal in Coal mix is maximized up to 85% as a plant trial. B. Steel Making - Electrical Arc Furnace: Electric Arc Furnaces (EAFs) are a central part of the production route that is an alternative to the dominant BF-BOF route. EAFs are used to produce carbon steels and alloy steels primarily by recycling ferrous scrap. In an EAF, scrap and/or manufactured iron units such as DRI, pig iron, iron carbide are melted and converted into high quality steel by using high-power Technological conjunction of iron & steel making technologies at Essar Steel India Ltd 6

7 electric arcs formed between cathode and anode. Scrap is by far the most important resource, accounting for about 80% of all electric arc furnace metal feedstock. The iron units are charged together with limestone into the furnace (Refer Fig.-5). The main task of most modern EAFs is to convert the solid raw materials to liquid crude steel as fast as possible and then refine further in subsequent secondary steelmaking processes. Fig.5 At EStIL, Hazira the Steel Melting Shops comprises of: A. DC Electric Arc Furnaces - 4 x 150 t DC EAFs Advantages of DC Electric Arc Furnace: 1. Can work even with weak / unstable grid support (lower short circuit capacity of grid) 2. Reduced voltage fluctuation lessens the problem of flicker thereby greatly reducing the need for costly VAR (reactive power) compensation. 3. Reduced electrode consumption due to lower electrode oxidation losses and steady operation 4. Lower noise level 5. Lower refractory cost for side walls (but more for bottom) 6. Reduced arc deflection 7. Infinitely Variable power input Up-gradations made: Hot DRI Feeding through Roof and HDRI Vessel 100 T Capacity + Trailor; Furnace Transformer modified to suit current from 130 kamps to 150 kamps; State of the Art Oxygen & Carbon Injection System Technology, Major Up-gradation to improve Refractory Technological conjunction of iron & steel making technologies at Essar Steel India Ltd 7

8 Life and Safety by Lower Shell Redesign with Chill Block, Upper Shell Copper Cast Panel, etc. Furnace 1 3: Fume Extraction System Primary System: Combustion Chamber to Chimney. B. Conarc Furnace: Twin Shell Conarc 200 T X 2 nos. It is a combination of CONvertor and electric ARC furnace. The process consists of Blowing & Arcing. In Blowing Hot metal is poured into the furnace and Oxygen is injected from the top lance. During blowing the temperature of steel increases due to exothermic reactions which is controlled by addition of DRI (Scrap may also be used) as a coolant. During Arcing three electrodes are brought down in the shell and current is passed through electrodes to produce arc. DRI is fed w.r.t. input power supply to maintain the bath temp. Advantages of CONARC process: It has the flexibility to use the charge-mix in many combination Once the required chemistry, temperature & Bath weight is achieved the metal is tapped. SMPs achievement: 1. Flexibility of iron bearing material usage with varied quality and proportion HBI / Hot DRI / Cold DRI, Hot Metal / Pig Iron, Scrap Internal, Skull from Blast Furnace / Corex / Furnace / Ladle Return, Oxides. Operating profiles developed to manage dynamics iron bearing material on heat to heat basis. 2. Heats made with 100 % Scrap or DRI or with 90 % of Hot Metal. 3. Zero Power Heat Making Furnaces used as Convertor. 4. Redesign and master steel refining process for managing S, P, N2 arising due to varied quality of Hot Metal. 5. As high quality steel maker, serving and meeting the need of all valued segments; be it White & Yellow Goods, Capital Goods, Shipbuilding, Pipeline for Sweet & Sour Gas, Electrical Steel, Dual Phase Steel and prestigious Automobile Sector. It has taken a long stride in serving the Defence Sector as well. Lastly, as an extension to Iron & Steel manufacturing, Essar makes pipes and extra wide plates as well as hot rolled, cold rolled, galvanized and colour coated steel through Conventional or Compact Strip Caster and this is an accolade to the entire manufacturing chain. All stated plants are backed-up by robust in-house developed Process Monitoring and Controlling Automation System, Central Command Centre, Planning Software s like IMPS, Factory Link, i2 etc., SAP, RCM and many more, facilitating to manage dynamics from varieties of input to quality outputs at an optimum cost. Esteemed organisational objectives are achieved through highly talented, enthusiastic, open minded and valuable team members, who are always striving for achieving greater heights. Technological conjunction of iron & steel making technologies at Essar Steel India Ltd 8

9 Truly, Hazira facility of Essar steel is a world class facility and a jewel in the crown for Indian steel industry. The challenge for the steel companies is to capitalize on this opportunity and create value for their stakeholders. For steel companies the way forward is to: Adopt technologies that use non coking coal as against coking coal for steel making. Secure raw material availability globally. Partner with professional and technical institutions to develop the necessary skill sets and competencies. Consolidate and enhance capacities to achieve economies of scale. Adopt cleaner and greener technologies. Just to inform audience that steel is already the most recycled material in the world. Steel companies need to do more to lower their greenhouse gas emissions by setting up iron ore beneficiation and palletisation facilities. Need to create a strong infrastructure in terms of railways, roads and ports. To produce one tonne of steel, will require a movement of 5 tonne of raw material and finished steel products. Innovation to improve sustainability a) Use of high strength & ultra-high strength steels in auto, construction & machinery b) Alternative alloying & coating technologies. CONCLUSION We are foreseeing a long and promising road ahead for the steel sector. Steel is the foundation of our future it is the pillar that supports industry, infrastructure and country s economic growth. Technological conjunction of iron & steel making technologies at Essar Steel India Ltd 9