Owner/operator: Hindalco Industries Ltd., a company of Adityabirla Group
Hirakud Power uses environmentally friendly circulating fluidized bed (CFB) combustion technology to produce electricity for one of the world’s oldest aluminum-smelting operations. This "captive power plant" has engineered a number of technical fixes to its original boiler designs to improve plant reliability and reduce outages and boiler repair costs. It also has made strategic investments in upgraded machinery to reduce auxiliary power consumption. In addition to an excellent environmental track record, as evidenced by being Asia’s first ISO 14001 (BS 7750) – certified power plant, Hirakud Power has solidified its position as an industry leader in CFB boiler operating experience and efficient power production.
The Indian Aluminum Co. (INDAL) slowly began to blossom in the post-independence era by seizing the opportunity to build an electricity-hungry aluminum smelter in the state of Orissa, the easternmost Indian province, which is blessed with abundant and inexpensive hydroelectric power generation. INDAL’s first smelter, christened in 1959, was capable of producing up to 10,000 tons/year (tpy).
Steady growth by INDAL began to stress the state-owned hydroelectric supplies in the early 1980s. Power interruptions became more frequent and, consequently, resulted in lost aluminum production. The price of electricity was also rising fast. The answer was clear: The only reliable electricity supply is one that a company owns and operates. Plans were developed by INDAL to construct a new captive power plant (that is, a plant built for and owned by an industrial firm).
In 1994, INDAL established its first coal-fired power generation system, rated at 67.5 MW, to provide an uninterruptible power supply to its adjoining aluminum smelting operation (Figure 1). Fortuitously, one of Asia’s largest coal deposits is located nearby, making the fuel choice simple. In 1999, Aditya Birla Group took over INDAL from the Aluminum Company of Canada and merged it with its flagship unit, Hindalco, a year later.
1. Reliable electricity needed for growth. Hirakud Power is a “captive power plant” that supplies all the electricity needed by Hindalco’s aluminum-smelting operation next door. The plant was built and expanded when government-run hydroelectric plants could not supply enough reliable and reasonably priced electricity to support the growing aluminum-smelting plant. The coal mine that supplies the plant’s fuel is located nearby. Courtesy: Hirakud Power
Aluminum production continued to rise, as did Hindalco’s need for reliable electricity. Aluminum production increased from 30,000 tpy to 143,000 tpy by 2009 with the commissioning of new smelting units, which also argued for the installation of additional power generation units. Generation rose from 67.5 MW to 367.5 MW in 100-MW increments in 2005, 2006, and 2008 (Figure 2).
2. Modern boiler technology. Hirakud Power operates four captive power units, shown in the foreground, consisting of 11 circulating fluidized bed combustion boilers and four steam turbines, with a total capacity of 367.5 MW. Courtesy: Hirakud Power
Coal is supplied by Hindalco’s own captive mine at Talabira and is fed to the boilers after suitable sizing by the plant crushers. The four units receive raw water from the Hirakud reservoir through gravity. The plant uses a dense phase pneumatic dry ash disposal system.
Of note, Hirakud Power is the first captive power plant in Asia to achieve ISO 14001-1996 certification (then BS 7750) for its high-quality environmental management system, certified by Bureau Veritas Certification (formerly BVQI), the world’s leading certification body. Hindalco’s environmental policy requires the company to be "committed to continuously improve our energy performance in all our activities, products, and services so as to make it environmentally sustainable for future generations."
Different Boiler Designs
Hirakud Power is recognized as a progressive electricity producer and is very active in ensuring that any waste products from the coal-fired units are recycled whenever possible or are properly disposed of. This attitude of taking pride in the small environmental footprint of its plants began with the installation of the first circulating fluidized bed (CFB) boilers in India in 1994. The Unit 1 boiler system is configured as a 2 x 145 tons per hour (tph) hot cyclone CFB, with the two boilers designed by Ahlstrom Pyropower and supplied by M/S Isgec John Thompson with a single steam turbine generator. Units 2 through 4 each consist of a 3 x 155 tph cold cyclone CFB boiler supplied by M/S Krupps India Pvt. Ltd. and a single 100-MW steam turbine generator. The four units together give Hirakud Power one of the world’s largest fleets of coal-fired CFB boilers at a single plant.
There are significant differences between the two CFB cyclone designs. The hot cyclone design has a much higher fluidizing velocity (6 to 7 m/s) and has full recirculation of fuel and bed material (more than 63 microns), causing increased erosion of refractory and steam generator tubes and significantly more insulation on the hot recirculation piping.
In the hot cyclone the combustion temperature is controlled by the rate of recycling fine material. Hot fine material is separated from the flue gas by the hot cyclone and is partially cooled in a loop seal, where a low-velocity fluidized bed is maintained and cooled using a Roots blower. The cooler fine material is then recycled to the dense bed. The cold cyclone design has a much lower fluidizing velocity, thereby saving on forced draft fan power, and a very steady bed temperature due to the controlled recirculated cold ash. The cold cyclone design also enables much quicker boiler start-up.
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