Iron melting furnace

1. Abstract :
Poorly designed cupolus lead to high
consumption of coke, thus increasing input costs of
melting. Most Indian foundries are conventiona cupolas
cupolas having a row of tuyeres. Further, several
designs versions of cupola, which split or divide the blast
air to the furnace are also in use. Dividing the blast air
has benefits in terms of energy savings. However, to
realize the full benefits of energy efficiency, optimal
designs of the divided blast system is crucial.
In order to popularize the correct design of DBC
among Indian foundries, TERI setup a demonstration
Dividend Blast Cupola (DBC), at a foundry unit in
Howrah, in the year 1998. the Indian Foundry
Association nominated the demonstration unit. The
design of the DBC was provided by BCIRA foundry
experts. The DBC is equipped with skip-bucket charger
and a high-efficiency pollution control system. The coke
consumption in the DBC was reduced by 35% in
comparison to the sub-optimal designed DBC being
operated by the foundry unit earlier. Subsequently, TERI
has been providing design of DBC and commissioning
assistance to several foundry units in different foundry
clusters in India.
This paper presents results of DBC designed by
TERI operating in a foundry unit in Rajkot. The foundry
not only got better charge coke economy but also was
able to use the better temperature and the consistent
chemistry obtained in the furnace to directly pour better
with lower rejections. q
Background :
TERI (The Energy & Resources Institute) has
been working with small-scale foundry units since 194,
with the support of SDC (the Swiss Agency for
Development and Co-operation, with the objective of
enhancing their energy efficiency and environmental
performance. This was to be done by working at the unit
level and providing the foundry units with technological
inputs so as to lead to energy efficiency, cost-reduction,
lower green-house (GHG) emissions and reduction in
local pollution.
A macro-analysis of 41 small-scale industries
carried out by TERI during 1992-94, had revealed that the
casting and forging units account for approximately 44% of
the energy usage. Since the major energy usage in any
gray iron foundry is the melting furnace, mainly the cupola,
this became the prime target of intervention.
TERI has been working together with industry
institutions mainly the Indian Foundry Association (IFA) and
the Institute of India Foundrymen (IIF) since the beginning
of the project. In 1998, a demonstration plant was designed
and commissioned at a foundry unit nominated by IFA at
Howrah to show-case an optimally designed divided blast
cupola (DBC). The situation prevailing at Howrah during
also demanded that the project should set up a pollution
control system (PCS) for the benefit of the industry. TERI
worked in partnership with ABB to design a venturi scrubber
based pollution control system, which would meet with
certainly, even the most stringent pollution control norms of
150 mg/Nm3 for suspended particulate matter (SPM)
prevailing for cupolas melting more than 3 tonnes per hour.
The demonstration plant resulted in a charge coke saving of
35% in comparison of the sub-optimal designed DBC being
operated in the foundry. The PCS delivered SPM levels
much below the emission norm of 150 mg/Nm3. q
Features of the DBC Technology :
Divided blast cupola (DBC) is a well-proven
technology for improving the energy performance at a
modest investment. As is evident from its name, a DBC
supplied blast air to the cupola furnace at two levels
metal tapping temperature.
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Benefits of an optimal designed Divided Blast Cupola (DBC)
Results from an actual replication for Indian foundries
Abhishek Nath, Prosanto Pal
The Energy and Resources Institute (TERI), New Delhi

2. l Higher metal tapping temperature
l Lower charge coke consumption
l Better carbon pick-up
TERI customizes the design of the DBC to suit
the specific requirements of the individual foundry unit.
Some salient features of TERI's design are the following :
l Optimum ratio of the air delivered to the top and
bottom tuyeres
l Minimum pressure drop and turbulance of the
combustion air
l Separate wind-belts for top and bottom tuyeres
l Correct tuyere area, tuyere number and distance
between the two rows of tuyeres
l Optimum well capacity
l Higher stack height
l Mechanical charging system
l Better material specifications
Replication Plants :
TERI has provided designs for setting up a
number of DBCs all over India. The locations where the
DBCs have been set up a spread all over the country.
Apart from the demonstration project in Howrah, there is
another replication project at Hoogly, there is others at
Nagpur in Maharashtra, at Coimbatore in Tamil Nadu, at
Vijaya Wada in Andhra Pradesh, at Mangalore in
Karnataka at Rajkot in Gujarat.
The following sections describe in detail the
achievement of the project at Shinning Engineers &
Founders plant in Rajkot. q
Replication Project Shining Engineers &
Founders, Rajkot :
Shinning Engineers & Founders is a gray iron
casting unit at Rajkot in Gujarat. The unit makes electric
motor bodies. Before going in for TERI designed DBC
the unit was having a 'Rajkot' design cupola for melting
iron. The 'Rajkot' design cupola has two rows
(sometimes even three) for discharging air into the
furnace. The cupola has a common wind chamber.
The charge coke usage in the cupola was 9.1%
which corresponds to a metal to coke ratio was 11:1. The
temperature was obtained in the range 1377 14770C.
The silicon loss was about 30%. The melting rate for the
27 inch ID cupola was 3.26 tph.
The charge coke usage in the cupola was 7.8%,
which corresponds to a metal to coke ratio was 13:1.
This Higher Metal : Coke ratio is represented
graphically in Figure : 1
The temperature was obtained in the range
1435 14620C. The consistency of the temperature has
a role in bringing down the rate of rejection due to
high/low pouring temperature. The consistent range of
temperature obtained is shown in figure 2.
The silicon
l o s s a l s o
reduced from
close to 30% to
a b o u t 7 %
r e s u l t i n g in
s i g n i f i c a n t
saving of ferro-silicon.
The melting rate for the 24 inch ID cupola was
3.25 tph. This implies an increase in the melting rate (if
taken per unit area) by about 25%. q
The melting rate for the 24 inch ID cupola was
3.25 tph. This implies an increase in the melting rate (if
taken per unit area) by about 25%.
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3. Benefits of the DBC Technology :
The enhancement of performance of the melting
operations in the foundry translates into monetary
savings. On the basis of the performance of the original
cupola of the conventional (Rajkot) design and the
performance of the TERI designed cupola the saving
from the technology adoption were worked out. They are
presented in Table 1. In addition to the coke savings,
other savings such as reduction in ferro-alloy usage and
lower rejection rates are also worked out.
The saving thus are approximately of the order
of Rs. 800 per tonne. In a typical foundry unit, say, one
which produces 250 tonnes of metal in a month the
monthly savings, would amount to Rs. 2 lakhs. The
capital cost of DBC, inclusive of civil works, platforms,
bucket charging system etc., is about Rs. 8,00,000. The
capital investment, on a new DBC, usually pays back
within a year, depending on the amount of metal melted
in the foundry unit.
Conclusion :
Encouraged by the success of the DBC,
Shinning has converted their other cupolas to divided
blast operation as well. Other units is the cluster now are
also implementing the technology. Two new DBCs have
been commissioned at Rajkot in January 2006. Now
there is interest not only among the larger players in the
sector but also among the smaller players who melt
comparatively smaller quantities.
The results obtained in Shinning and elsewhere
in India also show that there is a huge potential for
energy saving and GHG reduction in conventional
cupolas being operated by other foundry units operating
in the small-scale sector in India. TERI is willing to extend
technical support to any other foundry unit who may be
interested to upgrade their cupola plant and make it more
energy efficient.
Acknowledgement :
The technical assistance provided by TERI to the
foundry unit was supported by SDC (the Swiss Agency
for Development and Co-operation), New Delhi, as a part
of a foundry sector activities in a larger initiative called the
'Components Network for Small and Micro Learning
Enterprises' or the CoSMiLe.
The activities aim to provide small-scale foundry,
the opportunity to benefit from affordable, environment
friendly technologies that make it possible to save energy
and reduce pollution. Apart from disseminating cleaner
technologies such as the Divided Blast Cupola and
Pollution Control Systems among foundry units, the
project is also promoting techno-social integration and
knowledge management among the small-scale foundry
units in India. qqq
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