India is striving to conserve coal and slash its carbon emissions. The country which depended on coal for 56% of its total capacity of 356 GW as of May 2019, wants to reduce coal’s share to 45% of a planned capacity expansion to 480 GW by the end of 2022. During that period, it will also work to increase its share of renewables from the current 22% to 37%.
Leading the expansion is one of India’s largest power companies, NTPC. Formerly known as National Thermal Power Corp., the 70% state-owned company in 2010 became a “maharatna” company—a special designation that means it has greater autonomy from the central government in decision-making. Furthermore, the designation allows NTPC to incur unlimited capital expenditures, enter into joint ventures or strategic alliances, and restructure or raise debt from capital markets. It also has allowed the company, which currently has a fleet of 53 GW, to diversify, and by 2032, NTPC aims to make non-fossil-fuel-based generation capacity 30% of its portfolio.
However, the company’s fleet of 21 coal-fired plants will still play an important future role, said Gopalakrishnan Venu, executive director of Engineering at NTPC, on June 4 at the 9th International Conference on Clean Coal Technologies in Houston, Texas. India has abundant coal reserves, and the surge of renewables will require adequate sources for stability, and as India’s large population grows, so will its economy.
“We believe it is possible to fulfill our internal economic priorities while being true to long-term climate gains,” he added, noting that India aims to fulfill responsibilities that are engrained in climate conventions. It will mean, “The coal plants that we’re building now are a far cry from former times,” he said.
Venu noted that since the 1950s, India has accumulated years of experience customizing early imported technologies to fit the unique conditions of Indian coal, which is mostly bituminous with relatively low moisture but a high ash content of between 30% and 50%. (Comparatively, coal traded on the international market rarely exceeds 15% ash content.) In the 1990s, India established a full domestic value chain, from design to construction and operation, for subcritical plants, and in recent years, it has expanded plant sizes while reaching supercritical temperatures. This June, meanwhile, NTPC will commission the country’s first ultrasupercritical (USC) plant—a 660-MW unit at the Khargone Power Plant in Madhya Pradesh.
And now, India has embarked on an ambitious program to develop an 800-MW coal-fired advanced USC (A-USC) power plant using indigenous technology, Venu noted. “In today’s world, when ‘coal’ has become a bad word, it is somewhat of a fine balance that we’re making in the first introduction of indigenous A-USC technology,” he said.
The two-and-a-half year program, which was launched in April 2017, is being carried about by NTPC, major equipment manufacturer Bharat Heavy Electrical Ltd. (BHEL)—a company in which the government owns a 63% stake—and state research entity the Indira Gandhi Centre for Atomic Research (IGCAR, which is also working on advancing an indigenously developed fast breeder reactor).
As Shri Anil Kumar, an official from BHEL, noted on Tuesday, the program entails setting up a plant with steam parameters of about 300 bar and 700C. Government documents suggest the project is shooting for a 46% efficiency.
So far, developers have completed design and review of the boiler and turbine, and established the welding and machining of the turbine rotor and casing with new materials (alloy 617 and 625). The A-USC boiler itself will use Inconel 740 and Sanicro25. “We ruled out austenitic stainless steels for thick components because of their poor physical properties of higher expansion coefficient and low thermal conductivity,” Kumar said. “The materials selected need to have both improvement in creep properties and corrosion resistance as temperatures increase.”
But cost is proving a challenge for the Indian A-USC. Nickel-based alloys are more expensive than conventional power generation grades of steels, Kumar noted, but using nickel-based alloys was “unavoidable,” owing to temperature stress.
Developers have been testing the technology at a 210-MW test loop at NTPC’s Dadri coal plant. “Based on the tasks accomplished, there is confidence that the project will demonstrate a desired level of confidence in both design and manufacturing by September 2019,” Kumar said.
If all goes well, NTPC will begin setting up an 800-MW A-USC demonstration plant as part of the project’s second phase at the company’s 2,090-MW Sipat site in Chhattisgarh State, Venu said. “We are planning to start the demonstration by April 2020,” he said. “We are preparing ourselves for not only one plant, but a 10 A-USC fleet.” The project has so far identified the need to import certain features, such as to aid load-cycling, but for now, India is not exploring carbon capture, owing to “limitations in sequestration.” However, the A-USC program will examine carbon capture at a later stage, Venu added. “The A-USC project thus fits into the larger perspective of thinking.”
Along with the A-USC program, India is exploring other technologies to ramp up flexibility and clean up coal, including integrated gasification combined cycle technology, biomass co-firing in existing coal-fired boilers, waste-to-energy plants, development of air-cooled condensers for power plants, and implementation of zero-liquid discharge schemes. NTPC is also heading up the “world’s largest” program to install SOxand NOxreduction technologies in new and existing plants worth a total 60 GW. NTPC is meanwhile pilot testing selective catalytic reduction and selective non-catalytic reduction technologies suited specifically to high-ash Indian coals, and it plans to roll out the technology at eight NTPC power plants.
—Sonal Patel is a POWER associate editor (@sonalcpatel, @POWERmagazine)