ESP Case Study
Iron Ore Pelletisation Applicaton in Steel Industry
Essar Steel Ltd., Vizag THE CUSTOMER PROFILE
ESSAR Steel Ltd. (a Group Company of ESSAR: one of India's largest corporate houses) is a versatile manufacturer, capable of producing highly customized products. The company caters to a wide variety of product segments including roofing, automobiles, oil & gas, shipbuilding, fabrication and white goods. The company has a high level of forward and backward integration, from raw material to finished products, at every stage of the manufacturing process. It has an Ore Benification plant at Bailadilla, Chattisgarh, a Pelletization plant at Vizag and a Steel & Cold Rolling complex at Hazira.
The indurating machine, where the green balls are heat hardened, is the core of the pellet plant. It is an endless conveyor, made of 164 pellet cars which are continuously moving on tracks. The indurating machine is divided into various zones according to the temperature. Burners are arranged opposite each other on the longitudinal sides of the pre-heating and firing zone. The arrangement and sizing of the burners ensure a uniform temperature of hot gas over the width of the pellet bed. Since the burners are divided into several control zones, an optimum temperature profile can be adjusted which permits optimum heat treatment of the pellets. The fuel used for the burners is either LSHS or Natural Gas and is atomized by means of air. Preheating of the fuel is achieved by oil pre-heaters. Five process fans connected to wind boxes, provided beneath the sliding track of the indurating machine, supply the gas to/ from the traveling grate machine. During this process, gas is handled and moved substantially causing generation of fine dust. Hence, the wind box exhaust and hood exhaust are then passed through an ESP , where the dust is collected before the gas is released into the atmosphere through the chimney.
THE PELLETIZATION PROCESS
Pelletization turns very fine-grained iron ore into balls of a certain diameter, also known as pellets, which are suitable for blast furnace and direct reduction.
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The Pelletizing plant can be broadly classified into: Ore Benification & Grinding Section Filtration Section Weighing & Mixing Section Balling (green pelletizing) & Screening Section Indurating Section Dedusting Section
ESP Case Study #4
ESP Case Study
ESSAR Steel Ltd., Vizag, has a Pelletization Unit in its integrated steel plant. Initially they had a Mechanical Dust Collector (MDC) in circuit, which was giving them an outlet emission of around 150 mg/ Nm3. As such, achieving emissions of less than 50 mg/ Nm3 was not possible with the existing MDC. On the other hand, there was tremendous pressure from the Pollution Control Board for reduction of emissions. So, in order to achieve required lower emission levels, an ESP was proposed to be installed at the wind box and hood exhaust of the Indurating Machine. The challenge in this case was three fold:
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Achieving tighter emission norms of 50 mg/ Nm3 Fitting of the ESP in the space available Achieving lower pressure drop and, in turn, lower power consumption Entrapment of fine dust particles
THE THERMAX ENVIRO SOLUTION
Since the flow volume was large, initially it was decided to have two ESP chambers. They were to have individual access staircases, for better control of flue gas velocity. However, with space as a constraint, it was decided to go in for a double chamber ESP , without compromising on technology parameters like SCA, migration velocity etc. Also, sizing of the ESP was done in line with our requirement of Aspect Ratio and Duct Routing, which helped in achieving the desired results.
"The ESP was commissioned and put into continuous operation with all exhaust points connected as per design. The performance was found to be excellent with ESP achieving emission of 50 mg/ Nm3 as per design parameters.”
Description Gas volume (Am / Hr) Maximum inlet dust loading(mg/ Nm ) Outlet emission (mg/ Nm )
3 3 3
Design 9,00,000 1 50
Actual 9,50,000 1.05 40 - 50
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