Download energy efficiency improvement measuresfor the steel industry

Implementation of Green Manufacturing in reducing Carbon
Contents in Steel Industry to improve Air Quality and Business
Results
Shahzad Ahmad1, Alia Irfan2
1Associate Professor, Department of Mechanical Engg., A.F.S.E.T, Faridabad, Haryana,
India ([email protected])
2Assistant Professor, Department of Mechanical Engg., A.F.S.E.T, Faridabad, Haryana,
India ([email protected])
Abstract
In recent decade, there has been increased pressure on manufacturing companies to think
beyond the economic benefits of their process and products and consider the environmental
and social affects. Toxic wastes and acid precipitation created by steel industry are causing
crisis for thousands of communities around the world. Even more ominous, global crises
such as ozone depletion, greenhouse warming, deforestation and the loss of biodiversity
are in one way or another rooted in corporate products and production systems. Since the
country’s growth is necessary, its environmental concerns can be moderate in the
manufacturing sector by using energy and resources efficiently, and minimize generation
of waste. It is estimated that even if every factory, power plant, car and aeroplane is shut
down, the average global temperature would still increase by 0.6˚C in this century. ‘Green
Manufacturing’ or sustainable industrial activity is now the need of the hour and no more
an empty slogan. It is pointed out that adequate environment protection in a “green” steel
plant does not merely mean a tolerate disposal of pollutants emitted from its operation
units, but rather the effective implementation of a strategy whereby the formation of any
polluting agents in any part of this plant is include proper choice and control of raw
materials, and an untiring endeavour effort to optimize the complete manufacturing
process of the whole steel plant. Therefore, there is a need for an integrated approach like
Green Manufacturing technology towards energy and environment management of the
industry so that better energy efficiency and environmental friendliness can be achieved.
Keyword: Green manufacturing, CO2 emission, recycling, Sustainable development &
Steel industries.
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1. INDRODUCTION
A recent global survey by BCG reveals
that as many as 92% of the companies
surveyed are engaged in green initiatives.
Manufacturing companies that adopt
green practices benefit not only through
long term cost savings, but equally
importantly, from brand enhancement
with customers, better regulatory traction,
greater ability to attract talent and higher
investor interest. However, these benefits
require a long term commitment and
making trade-offs against short term
objectives, as the economics of green
manufacturing is still evolving and not
well understood as yet.
The motivation for adopting green has
varied across sectors. Some take it up
owing to regulatory compulsions (e.g.
power), while others see it as an
opportunity to build a stronger brand with
consumers
(e.g.
retail).
Steel
manufacturers have adopted green
initiatives to stabilize rising energy costs,
while automobile companies have seen it
as an opportunity to launch electric and
hybrid cars to meet increasingly stringent
emission regulations. The impact of green
initiatives also varies by the industry
sector. For example, green initiatives in
the power sector have the maximum
impact on reducing CO2 emissions
followed by transportation and then the
industrial sector.
Once we have achieved the focus to think
green in all aspects of our industry, we are
open to the possibilities that were only
waiting for us to seize them. This focus,
along with the pragmatic application of
existing technology, will guarantee that
the steel industry is recognized as a
sustainable leader by other industries and
the public.
If green manufacturing can be put into
practice successfully, the contradiction
between environmental pollution and
sustainable
development
will
be
effectively solved. So it is feasible and
necessary for steel industry in India to
adopt the green manufacturing mode.
2. WHAT ‘GREEN’ MEANS AND
WHY IT IS IMPORTANT?
The term “green” manufacturing can be
looked at in two ways: the manufacturing
of “green” products, particularly those
used in renewable energy system and
clean technology equipment of all kinds,
and the “greening” of manufacturingreducing pollution and waste by
minimizing natural resource use,
recycling and reusing what was
considered waste, and reducing emissions.
Green manufacturing addresses a number
of manufacturing matters, including 4R’s
(Reduce,
Reuse,
Recycle
and
Remanufacturing), conservation, waste
management,
water
supply,
environmental protection, regulatory
compliance, pollution control, and a
variety of related issue. [5]
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A number of companies have started
adopting green initiatives as an integral
part of their operations. These initiatives
are driven by five factors:
Rising energy and input costs.
Growing consumer pull for Green
products.
Increasing regulatory pressures as policy
makers introduce new and stricter
environmental and waste management
laws.
Technological advances which open up
new attractive business opportunities.
The need to enhance competitive
differentiation, particularly for first
movers or those who are able to break the
compromise between short-term higher
costs and numerous benefits (example:
brand premium, new customer segments).
Green has moved from being perceived as
a ‘necessary evil’ to being seen as ‘good
business’. Companies that undertake
green initiatives stand to be advantaged on
brand enhancement,
traction and
regulatory compliance, greater ability to
attract and retain talent, enhanced
customer retention and potential cost
savings. However, these benefits require a
long term commitment and making
tradeoffs against short term objectives, as
the economics of Green manufacturing are
not well understood yet.
3. STEEL-MAKING
ROUTE
PROCESS
Currently the dominating processes in the
global steel production are the integrated
steelworks (primary route) and the minimills (secondary route). Integrated
steelworks are plants where pig iron is
made by reducing iron ore in blast
furnaces. The pig iron is processed in oxyplants to get the crude steel, which is later
cast, rolled and finished.
In mini-mills, scrap and ores are melted
and converted into crude steel directly in
electric arc furnaces. Other production
routes do not have a significant weight in
global production because they are
obsolete, or because they are so new that
their share in production is still very small.
The first happens to the open-hearth
furnace, currently used only in the former
Soviet Union, China and India. Direct
reduction is used mainly in zones with
lack of scrap located in developing
countries, and most of smelting reduction
projects are not considered economically
viable. [6]
3.1 Integrated steelworks
In integrated steelworks the blast furnace
is the main operational unit where the
primary reduction of oxide ores is
transformed into liquid iron, so called pig
iron. Modern high-performance blast
furnaces
require
physical
and
metallurgical preparation. There are two
types of iron ore preparation plants: sinter
and pellet plants. Pellets are nearly always
made of one well-defined iron ore or
concentrate at the mine and are
transformed in this form. Sinter is
generally produced at the iron works from
pre-designed mixtures of fine ores,
residues and additives. The main reducing
agents in a blast furnace are coke and
powdered coal forming carbon monoxide
and hydrogen, which reduce the iron
oxides. Coke and coal also partly act as
fuels. Coke is produced from coal by
means of dry distillation in a coke oven
and has better physical and chemical
characteristics than coal. In many cases,
additional reducing agents or fuels are
supplied by injection of oil natural gas
and, in a few cases, plastics. A hot blast
provides the necessary oxygen to form the
carbon monoxide, which is the basic
reducing agent for the iron oxides.
The individual production units are
connected both in terms of products and
residues flows (mill scale, filter dusts,
sludge from scrubbing BF gas or BOF gas
etc.), water (common treatment of various
wastewater streams, cascade usage of
cooling water, etc.) and energy (COG10,
BF gas, BOF gas, steam from BF top
pressure turbines or basic oxygen
furnaces, etc.). These interdependencies
have been created to minimize emissions
as well as to optimize productivity and
reduce costs. [6]
Energy interdependency is the most
complex of these interdependencies. The
dominant energy inputs are coal and, if
bought from an external supply, coke.
Also electricity, natural gas, oil and (in a
few cases) plastics represent the energy
inputs. Coke oven gas, blast furnace gas
and basic oxygen furnace gas are used for
many purposes (heating coke oven
batteries, provision of hot blast, ignition of
the sinter feed, heating of furnaces for hot
rolling etc.). Steam from top pressure
turbines of the blast furnaces or from basic
oxygen furnaces is also used for various
processes. COG and BF gas are recovered
and used at all integrated steelworks.
However, this is not the case for BOF gas
or for steam recovery using BF top
pressure turbines. Steam recovery
depends on top pressure of the blast
furnace, on the operation condition of the
BOF and on the usability of BOF gas.
3.2 Mini-mills
The direct smelting of iron-containing
materials, such as scrap, is usually
performed in electric arc furnaces, known
as mini-mills, which play an important
and increasing role in modern steelworks
concepts. The major feedstock for the
EAF is ferrous scrap, which may comprise
of scrap from inside the steelworks, from
steel product manufacturers (e.g. vehicle
builders) and capital or post-consumer
scrap (e.g. end of life products). Direct
reduced iron (DRI) is also increasingly
being used as a feedstock due both to its
low gangue content and variable scrap
prices. The main operations performed in
an electric arc furnace plant are raw
material handling and storage, furnace
charging, scrap melting, steel and slag
tapping and continuous casting.
3.3 Alternative techniques: smelting
reduction and direct reduction
Blast furnaces require coke, and coke
plants are expensive and have many
environmental problems associated with
their operation. Thus, it would be
beneficial from an economic and
environmental point of view to produce
iron ore without the use of coke.
Nowadays, nearly all blast furnaces can
reduce
their
coke
consumption
significantly by means of reductant
injection at tuyeres (blast pipes).
However, coke can never be fully replaced
in a blast furnace because of its burden
supporting function. The minimum blast
furnace coke rate is approximately 200
kg/t pig iron.
There is an increasing production of steel
from scrap in electric arc furnaces (EAF).
Production of steel from scrap consumes
considerably less energy compared to the
production of steel from iron ores. The
problems with the quality of scrap-based
steel introduce restraints and the use of
direct reduced iron (DRI) as feedstock
enlarges the possibilities of the EAF steelmaking
route.
Summarizing,
the
following aspects put pressure on the blast
furnace production route of steel:
• Environmental aspects of sinter plants,
• Environmental and economical aspects
of the coke oven plant,
• Relative inflexibility and scale of the pig
iron production,
• Increasing competition by the scrap
based and DRI-EAF steel-making route.
On the other hand, the advantages of the
BF route as regards recycling capability
and economical investment should also be
recognized. This has triggered the
improved environmental and economical
operation of the blast furnace route and the
development of alternative routes for iron
making. [6]
4. ENERGY EFFICIENCY
IMPROVEMENT
MEASURESFOR THE STEEL
INDUSTRY
The Iron and Steel industry is an energy
intensive industry. However, industrywide technology advances, such as new
process adoption and widespread adoption
of advanced process controls, have
reduced energy intensity by 30 percent
since 1990.
This section describes the energy
efficiency measures that may be feasible
for GHG control in the Iron and Steel
industry. All measures reduce fuel
consumption and, therefore, produce
direct and indirect reductions in fuelassociated GHG emissions. [9]
a. Sinter Plant Heat Recovery
Heat recovered from the sinter plant can
be used to preheat the combustion air for
the burners and to produce high-pressure
steam, which can then be used in steam
turbines to generate power. Various
systems exist for new plants (e.g., Lurgi
emission optimized sintering process),
and existing plants can be retrofitted.
Based on a retrofitted facility in The
Netherlands, fuel savings were estimated
to be 0.47 MMBtu/ton (0.55 GJ/tonne) of
sinter, and increased electricity generation
was estimated to be 1.4 kilowatt hour per
ton (kWh/ton) (0.0056 GJ/tonne) of sinter.
The payback time was estimated as 2.8
years. Emissions of nitrogen oxide (NOx),
sulfur oxide (SOx), and PM are expected
to be reduced.
b. Coke Dry Quenching
Dry quenching of the coke, in place of wet
quenching, can be used to recover sensible
heat that would otherwise be lost from the
coke while reducing dust. The steam
recovery rate with this equipment is about
0.5 MMBtu/ton (0.55 GJ/tonne) coke. The
coke dry quenching (CDQ) process offers
distinct advantages of sensible heat
recovery, conservation of water and zero
air and water pollution. In addition,
Nippon Steel's performance record shows
that the use of coke manufactured by dry
quenching reduces the amount of coke
consumption in the blast furnace by 0.24
MMBtu/ton (0.28 GJ/tonne)4 molten iron.
c. Recovery of Blast Furnace Gas
Approximately 1.5 percent of the gas used
in the blast furnace may be lost during
charging, which could be recovered. A
recovery system has been installed on a
furnace in The Netherlands at a cost of
$0.43/ton ($0.47/tonne) of hot metal.
Energy savings have been estimated to be
approximately 17 kWh/ton (0.066
GJ/tonne) of hot metal. The payback time
is estimated as 2.3 years.
d. Oil Injection
Heavy fuel oil or waste oil can also be
injected instead of coke. The coke
replacement rate is 1 ton of oil (0.9 tonnes)
to replace 1.2 tons (1.1 tonnes) of coke.
Like natural gas, oil contains hydrogen,
leading to decreased CO2 emissions. If oil
injection is used along with oxygen burner
technology, the amount of oil injected can
be increased by 100 percent as compared
to regular burners. This increase would
correspond to a one-to-one weight ratio
between the oil injected and the hot metal
produced.
e. Pulverized Coal Injection
Almost all Integrated Iron and Steel plants
have implemented pulverized coal
injection at varying injection rates.
Pulverized coal and natural gas injection
replaces the use of coke, thereby reducing
coke production and saving the large
amount of energy consumed in coke
making, reducing emissions from coke
ovens, and reducing maintenance costs.
The energy savings in the blast furnace
due to coal injection have been calculated
at 3.23 MMBtu/ton (3.76 GJ/tonne) coal
injected. Fuel savings were estimated to
be 0.66 MMBtu/ton (0.77 GJ/tonne) of hot
metal, with capital costs of $9.92/ton
($10.94/tonne) of hot metal.
f. Recuperator Hot-Blast Stove
The hot-blast stove flue gases can be used
to preheat the combustion air of the blast
furnace. Various systems have been
implemented, with fuel savings ranging
from 20 to 21 kWh/ton (0.080 to 0.085
GJ/tonne) of hot metal at a cost of
approximately $19 to 21/MMBtu ($18 to
$20/GJ)
saved
(equivalent
to
approximately $2.0/ton [$2.2/tonne] of
hot metal). Preheating can lead to an
energy saving of approximately 0.3
MMBtu/ton pig iron (0.35 GJ/tonne). An
efficient hot-blast stove can run without
the need for natural gas. [7]
5. ENVIRONMENTAL RELEVANCE
In integrated steelworks, sinter plants
produce the highest levels of emissions for
most atmospheric pollutants, followed by
coke-oven plants. Blast furnaces, basic
oxygen steel making, coke ovens as well
as electric arc furnaces have considerable
relative percentages of dust emission.
g. Flameless Burner
This technology carries out combustion
under diluted oxygen conditions using
internal flue gas recirculation and the
flame becomes invisible. Flameless oxyfuel gives high thermal efficiency, higher
levels of heat flux, and reduced fuel
consumption compared to conventional
oxy-fuel. These benefits are combined
with low NOx emissions and better
thermal uniformity. Since 2003, more than
30 furnaces within the U.S. steel industry
have been equipped with flameless oxyfuel combustion. ArcelorMittal recently
received the Association for Iron & Steel
Technology (AIST) 2009 Energy
Achievement Award for its work to
implement a flameless oxy-fuel operation
on its rotary-hearth steel-reheat furnace.
ArcelorMittal realized a 60 percent
reduction in the furnace’s total fuel
consumption compared to the original airfuel operation. The technology also
reduced the furnace’s annual NOx
emissions output by 92 percent and annual
CO2 emissions by up to 60 percent below
the prior air-fuel operating levels.
CO2 direct emissions basically depend on
the consumption of fossil fuels, the energy
mix, and the production level. The
reference simulation gives in 2030 a
decrease of 29%, from 1990, in the world
total amount of energy used by the sector,
produced by the shift to cleaner (and
cheaper) technologies and fuels. Coal and
coke dominate the energy input in 1990.
By 2030, coal consumption drops 58%
and coke 54%. Energy efficiency
improvements are reached at the expense
of
solid
fuels.
Technological
improvements in the secondary routes
avoid a higher increase in the consumption
of electricity.
In BOF process, secondary emissions
takes place during charging, oxygen
lancing and tapping. [4]

h. Scrap Preheating
Scrap preheating is used extensively in
Japan, and the use of hot furnace gases for
scrap preheating is now being applied in
the U.S. Scrap preheating can save 4 to 50
kWh/ton (0.016 to 0.20 GJ/tonne) and
reduce tap-to-tap times by 8 to 10 minutes.
Preheating scrap reduces the power
consumption of the EAF by using the
waste heat of the EAF as the energy source
for the preheat operation.
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Metallurgical wastewater is generated
during off gas cleaning. For fugitive dust
control, a total housing or enclosure
system (dog house) installed for converter
vessel capture the fugitive dust which is
cleaned in a bag filter or ESP.
The off-gas from BOF (also called LD
gas) is rich in energy which can be used
for reheating and power generation
purpose.
Nearly 2-4% of the energy required in the
steel plant is supplied by LD gas.
Metallurgical
wastewater
generated
during off cleaning from BOF and BF
which are mixed together and treated.
Metals are recovered in sludge and water
is recycled in the process.
Most of the Indian plant have adopted
combination of off-gas collection and
combination system. Yet the fugitive
emissions are still high because of nonfunctional emission control system. High
amount of CO2 in can combusted in the
furnace freeboard or in the 4rth hole
evacuation system conveying the offgases to the bag house for cleaning.
Steel scrap has become the steel
industry's single largest source of raw
material because it is economically
advantageous to recycle old steel into
new steel. In light of this, steelmaking
furnaces have been designed to consume
steel scrap. [4]
a. Environment
protection
(Air
pollution and water pollution)
Recycling reduces the need for extracting
(mining, quarrying and logging), refining
and processing raw materials all of which
create substantial air and water pollution.
As recycling saves energy it also reduces
greenhouse gas emissions, which helps to
tackle climate change. Currently, UK
recycling is estimated to save more than
18 million tons of carbon dioxide a yearthe equivalent to taking 5 million cars off
the road (steel recycling institute). [1]
b. Reduced landfill
When we recycle, steel scrap materials
are reprocessed into new products, and
as a result of this, the amounts of scraps
sent to landfill sites are substantially
reduced.
c. Energy saving
Using steel scrap in the manufacturing of
new steel uses considerably lesser energy
than that required for producing new steel
from virgin raw materials (iron ore, coal,
limestone). Not only that, there is also
extra energy savings because more
energy is required to extract, refine,
transport and process raw materials ready
for industry use compared with providing
steel scrap which are ready materials to
be charged into the Electric Arc Furnace
for easy and faster steel production
d. Conservation of Resources
Steel scrap reduces the consumption of
valuable minerals like iron ore, coal,
limestone and water. For every metric
ton of recycled steel scrap, 1.5tons of iron
ore, 0.5ton of coal, 0.054ton (120 pound)
of limestone and 40%of water normally
used in the production from virgin
material is conserved.
6. CONCLUSION
Efforts to achieve deep GHG emission
reductions
will
have
significant
consequences for materials use. About
36% of all CO2 emissions can be
attributed to industry, mainly to materials
production processes. In addition, certain
process improvements are dependent on a
better understanding of materials
transformation processes. About 18-26%
improvement can be achieved based on
existing technologies, but this is not
sufficient to compensate for the projected
growth in demand. Further improvements
can be achieved only through better
materials and new emerging production
processes.
Materials recycling reduces the energy
needs and direct CO2 emissions
substantially, by a factor of 2 to 4. Total
scrap recovery in steel production
increased from about 325Mt to 450Mt
from 1970 to 2003. This increase is the net
result of a decreasing amount of home
scrap (an indication of fabrication yield
improvements) and an increasing amount
of so-called obsolete scrap (i.e., postconsumer waste, in contrast to processing
waste or pre-consumer waste). Even
though the recycling rate is high, an
expanding economy has meant that the
total crude steel production is roughly
twice the amount of scrap collected and
used. Net additions to the stock of
materials in the economy constitute a
major materials sink. Materials losses
from the life cycle of steel are small, so
increased recycling is an improvement
option of secondary importance. The CO2
breakthrough program of the International
Iron and Steel Institute aims for the
development of CO2-free steel production
processes. The European activities under
this heading are named ULCOS (UltraLow CO2 Steel). In the second stage of
this project, industry has selected three
process routes for further development:
(1) blast furnaces in combination with
CO2 capture and storage; (2) natural-gasbased reduction processes (with CO2
capture and storage); and (3) electrolysis
production processes, similar to aluminum
smelting.
It is pointed out that adequate
environment protection in a “green” steel
plant does not just mean a accept disposal
of pollutants emitted from its operation
units,
but
rather
the
effective
implementation of a strategy whereby the
formation of any polluting agents in any
part of this plant is include proper choice
and control of raw materials, and a
constant endeavor effort to optimize the
complete manufacturing process of the
whole steel plant. Through the findings
of this work, recycling of steel s crap is
suggested as an alternative to boost the
local content of steel production, reduce
energy consumption, carbon dioxide emis
-sion (as the world production and
manufacturing system is going green). The
implementation of green manufacturing
focused on investigating the energy
saving and CO2 emission from producing
steel and effective utilization of recycling
of steel scrap as a way of sustainable
development in steel industry.
REFERENCES
1. Mr. Shahzad Ahmad, “Sustainable
Development In Steel Industries After the
Implementation
of
Green
Manufacturing”, Volume 2, Issue 4; 871875.
2. Prof. Shailee G. Acharya, “A Review on
Evaluating Green Manufacturing for
Sustainable Development in Foundry
Industries”, Volume 4, Issue 1, January
2014; 232-237.
3. Mr. Md. Salman Alvi1, Mr. Shahzad
Ahmed,
“Approaching
Green
Manufacturing In Iron and Steel
Industry”, Volume 2, No. 3, July 2013,
108-112.
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