The present work is an attempt to conserve energy in coal based sponge iron industry incorporating
certain design modifications without disturbing the process technology. A typical sponge iron plant has
been investigated to find out the potential areas where energy is being wasted. To recover heat from
these areas two design modifications, Case-1 and Case-2, are proposed. Case-1 accounts for preheating
of air using waste gas exiting from ESP. However, for Case-2 initially water is heated using hot sponge
iron exiting rotary kiln and further hot water is used to preheat air. To compute coal demand of modified
designs a model is developed based on heat of reactions, feed preheating, sensible and radiation losses,
etc. Preheating of air up to 170 ◦C for Case-1 reduces coal consumption by 8.7%. Consequently, waste gas
generation reduces by 16.7%. Thus, for Case-1 profit is Rs 9.6 million/year. However, for Case-2 preheating
of air to 80 ◦C before entering the kiln reduces coal and water consumption by 7.2% and 96.3%. Consequently,
cooling tower capacity is reduced by 37.2%. Due to 27.8% less profit for Case-1 in comparison to
Case-2 Case-1 offers higher payback period than that of Case-2. Thus, Case-2 is selected as best proposed
design.
It is seen that the growth of sponge iron industry in last few
years is unremarkable and today India is the largest producer of
sponge iron as it covers 16% of global output. According to Sponge
Iron Manufacturers Association [1], India has produced around 23
million tonnes of sponge iron in the financial year of 2009–2010.
Sponge iron is used as feedstock and a recognized alternative to
steel scraps in iron and steel making processes. Due to certain problems
inherent in blast furnace and induction furnace process such
as the scarcity of steel scraps in international markets, depleting
reserves of high quality metallurgical grade coking coal, environmental
constraints on coke and sinter plants, and requirement of
auxiliary plants with increased capital and operational intensity
direct reduction technology has emerged as a potential process for
iron and steel making.
The present work is an attempt to conserve energy in coal based sponge iron industry incorporatingcertain design modifications without disturbing the process technology. A typical sponge iron plant hasbeen investigated to find out the potential areas where energy is being wasted. To recover heat fromthese areas two design modifications, Case-1 and Case-2, are proposed. Case-1 accounts for preheatingof air using waste gas exiting from ESP. However, for Case-2 initially water is heated using hot spongeiron exiting rotary kiln and further hot water is used to preheat air. To compute coal demand of modifieddesigns a model is developed based on heat of reactions, feed preheating, sensible and radiation losses,etc. Preheating of air up to 170 ◦C for Case-1 reduces coal consumption by 8.7%. Consequently, waste gasgeneration reduces by 16.7%. Thus, for Case-1 profit is Rs 9.6 million/year. However, for Case-2 preheatingof air to 80 ◦C before entering the kiln reduces coal and water consumption by 7.2% and 96.3%. Consequently,cooling tower capacity is reduced by 37.2%. Due to 27.8% less profit for Case-1 in comparison toCase-2 Case-1 offers higher payback period than that of Case-2. Thus, Case-2 is selected as best proposeddesign.It is seen that the growth of sponge iron industry in last fewyears is unremarkable and today India is the largest producer ofsponge iron as it covers 16% of global output. According to SpongeIron Manufacturers Association [1], India has produced around 23million tonnes of sponge iron in the financial year of 2009–2010.Sponge iron is used as feedstock and a recognized alternative tosteel scraps in iron and steel making processes. Due to certain problemsinherent in blast furnace and induction furnace process suchas the scarcity of steel scraps in international markets, depletingreserves of high quality metallurgical grade coking coal, environmentalconstraints on coke and sinter plants, and requirement ofauxiliary plants with increased capital and operational intensitydirect reduction technology has emerged as a potential process foriron and steel making.
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