POWER October 2014 - 30

TOP PLANTS
kV transmission line to transmit 1,000 MW
from Mundra to Dehgam in Gujarat and the
989-km 500-kV high-voltage direct current
(HVDC) bipole line with the capacity to
transmit 2,500 MW from Mundra to Mohindergarh
in the northern state of Haryana. The
latter is the first HVDC system in the private
sector in India.
While Siemens India was contracted to
build the HVDC substations at Mundra and
Mohindergarh, the HVDC line was constructed
by Jyoti Structures Ltd., both works
taking three years till commissioning in July
2012. The Mundra-Dehgam line was constructed
in sections by Jyoti and Kalpataru
Power Transmission Ltd., taking two years
till commissioning in July 2009.
Coal Supply
The Mundra TPP is a significant milestone in
the path to realizing Adani Power's target of
generating 20,000 MW by 2020. By that year,
the Adani Group is also seeking to mine 200
million metric tons (mt) of coal and handle
200 million mt of cargo from its ports.
At full load, the plant consumes about
55,000 mt of coal per day, though its yearly
consumption is between 16 and 17 million
mt. It runs on blended subbituminous coal,
about 70% imported from the Adani coal
mine in Bunyu, in Indonesia's East Kalimantan
province, and the rest from the public sector
Mahanadi Coalfields in the eastern Indian
state of Odisha. The coal is freighted to the
Adani Group's Mundra port, India's largest,
which notched a throughput of 100 million
mt in 2013-14 and which is slated to become
the largest coal import terminal in the world.
From there, a high-speed conveyor belt conveys
the coal to the plant 9.5 km away at
6,000 mt per hour.
The Mundra TPP, named after the coastal
town near which it is located in the arid Kutch
district, operates in far-from-conducive conditions.
" We are constantly challenged by a
highly corrosive and saline ambient condition,
with average wind speeds between 20
and 40 kmph that affect the performance of
the cooling towers, " said Station Head Anand
Kumar Singh. " Besides, our plant has been
designed to operate with high, 33% moisture
coal. " High-moisture coal can choke coalhandling
chutes and coal feeders, reduce
mill output, and increase the heat rate, he explained.
To reduce the moisture content, the
coal is pulverized to coal fines that are then
admixed in a drying chamber with a dry gaseous
mixture.
Maximizing Seawater Usage
Mundra is India's largest TPP to function on
a seawater-based closed-cycle induced draft
circulating cooling water system. The sys30
tem
draws on seawater that is recycled up to
four times, conserving water and requiring a
smaller discharge pipeline into the sea than
an open-circuit cooling system.
Though seawater is used for the cooling
system, other auxiliary systems use seawater
purified by a reverse osmosis plant that can
produce 47 million liters of freshwater every
day.
Boilers require demineralized water that
is produced in demineralization plants. Each
660-MW boiler can convert more than 2,000
mt of water per hour into steam that is 250
times the atmospheric pressure and at a high
of 570C. Steam is sent to the turbine through
high-pressure pipes, after which it is collected
and indirectly cooled in a condenser with
seawater and recycled back to the boiler.
Jaain said plant equipment is protected
against high corrosiveness and salinity by
using the right type of coatings, sacrificial
anodes, and impressed current cathodic protections.
" There is a three-year rolling schedule
for structural painting, a changeover
schedule for equipment that handles seawater,
and anti-corrosive coatings for reinforced
cement concrete structures, " he added. At
times, windborne drifts from the cooling
towers cause salt deposition on the switchyard
insulators, which leads to tracking on
the high-kV insulators, resulting in unit trips.
To counter this, a special protective coating is
applied to the insulators at fixed intervals.
Environmental Controls
The FGD system, supplied by Alstom India,
requires only seawater as the adsorbent (no
alkaline chemicals) to reduce sulfur emissions
(Figure 1). Its simplified structure-comprising
an adsorption tower, seawater supply
pump, and aerator-renders operation and
maintenance (O&M) easy, said Associate General
Manager (O&M) Girish Raghuwanshi.
" No by-products are formed, and the adsorbents
can be released into the sea after adjusting
their pH, chemical oxygen demand, and
dissolved oxygen, " he explained. " Increase of
sulfate in the seawater returned to sea is within
natural seawater variations, and emissions too
are well within the norms prescribed by the
Gujarat Pollution Control Board, which are
50 mg/Nm3 for particulate matter, 100 ppm of
SO2, and 50 ppm for nitrogen oxides. "
The Mundra TPP is researching the expanded
usage of the fly ash it generates, as
a liming material and as a feedstock for vermicomposting
(converting organic waste into
fertilizer). Most of the fly ash is conveyed to
three 3,000-m3 silos. From there, trucks dispatch
it to makers of bricks, ceramics, cement
and roads; it also is packed in 1.4-mt bags for
shipment to the Middle East.
In the first experiment of its kind in India,
www.powermag.com
1. Seawater system. At the Mundra
plant, only seawater is needed by the flue gas
desulfurization system to reduce sulfur emissions
to required levels. The nine units share
four stacks, Units 1 and 2, 3 and 4, and 5 and
6 having three separate stacks with two flues
each, while Units 7, 8, and 9 have one stack
with three flues. Courtesy: Adani Power Ltd.
23 mt of vermicompost have been produced
to date and provided to surrounding villages,
said Adani Power COO Jayadeb Nanda. Its
production involves mixing equal portions
of fly ash and organic matter, in the form of
cow dung, and incubating this mixture with
anecic earthworms for 50 days. This spawns
phosphate-solubilizing bacteria that convert
the insoluble minerals from fly ash into more
soluble forms, enhancing the bioavailability
of the nutrients in the vermicomposted series.
Nanda says cattle dung is available in
abundance from villages near the project,
facilitating the management and disposal of
agricultural as well as industrial wastes.
Wider Impact
The Mundra TPP is visited by power professionals
and engineering students from India
and beyond for refresher courses and training
provided by its state-of-the-art Training
& Research Institute.
" With success comes responsibility, so we
take care to reinvest in protecting and developing
the communities within which we live
and operate, " said Gautam Adani, whose wife
Priti heads the Adani Foundation, the Group's
corporate social responsibility arm. " We invest
3% of our group profit in community
initiatives through the Adani Foundation. " In
Mundra, these include a 50-bed hospital, mobile
health care, rural dispensaries, two large
and several small play schools, provision
of drinking water, watershed management,
counseling and assistance in advanced farming
techniques, groundwater conservation,
and skill-building for traditional artisans. ■
-Sarosh Bana is executive editor of
Business India.
POWER | October 2014
http://www.powermag.com
POWER October 2014

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