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View Points | October 2013

BHEL is adopting advanced steam cycles

With increased emphasis on clean energy norm implementation, BHEL, the country's largest supplier of heavy equipment, has stepped up the mission to add advanced technologies to meet the rising demand in the country. AV Krishnan, Executive Director of Trichi unit, shares his views on advanced technologies in boilers and turbines.

There is an increasing demand for advanced technologies. How is BHEL dealing with the rising demand for key boiler technologies in the market?
Till 2008, we were offering steam generators for power generation in the subcritical segment with unit ratings ranging from 110 MW to 600 MW with turbine throttle pressure of 150 kg/cm2 for 210/250 MW and 170 kg/cm2 for 500/600 MW units. After supplying more than 950 boilers, BHEL is adopting advanced steam cycles with turbine throttle pressure of 247 kg/cm2 for 660 MW and 800 MW units to improve the environmental and economic performance of India's power generation.

In addition to this, circulating fluidised bed combustion technology (CFBC), which is hard to burn in the conventional type of boilers as furnace temperatures are higher than ash fusion temperatures. Interestingly, CFBC technology is highly handy for burning low-grade fuels such as lignite, petcoke, which is mostly rejected by washeries and host of other fuels. The CFBC technology has demonstrated an unparalleled ability to achieve low nitrogen oxide and sulphur dioxide by adding lime powder directly to the combustor. The CFBC technology has been credited with environment-friendly operations and high flexibility for fuel variants. In 1999, BHEL commissioned two units of 125 MW CFBC boilers for Gujarat Industrial Power Corporation Limited at Surat in Gujarat, which was then the largest CFBC plant in whole of the south-east Asia.

BHEL proved its mettle by commissioning 250 MW CFBC power plant for Neyveli Lignite Corporation at Neyveli in Tamil Nadu and it is successfully operational. This has placed India among a select few nations who have such large scale CFB units along with Germany, US, China, France and Poland.

Super critical technology is the most demanded technology in the world. How is BHEL taking this ahead?
Supercritical boiler technology is the most popular boiler technology, which is currently being deployed in power plant. BHEL is offering the best to the customers, after mastering the sub-critical conventional drum-type boilers, which is being backed off by a global player Alstom. Once-through, supercritical technology for higher unit ratings of 660 MW to 1000 MW offers various benefits including increased efficiency, lower fuel consumption, lower emission levels of CO2, NOX and SOX, lower operating costs and greater operational flexibility. BHEL has already contracted 18 supercritical sets totalling to the tune of about 13,000 MW.

These include 2x660 MW for NTPC's Barh project in Bihar, 2x800 MW for Andhra Pradesh Power Development Company Ltd's Krishnapatnam project, 3x660 MW for PPGCL's Bara project in Uttar Pradesh, 2x800 MW for RPCL at Yermaras in Karnataka, 1x800 MW RPCL project in Edlapur in Karnataka, 1x700 MW for KPCL's project at Bellary in Karnataka, 3x660 MW for Bajaj Hindustan Limited Power Project at Lalithpur in Uttar Pradesh BHL, 2x660 MW for DB Power Singrauli project in Madhya Pradesh and 2x660 MW NTPC's Mouda Stage II in Maharashtra.

What kind of measures you have been taking to enhance boiler efficiency?
For improving the power plant cycle efficiency, BHEL designs boilers for high pressure, high super heater and reheater temperature and higher feed water temperature. BHEL is also taking continuous efforts to improve the efficiency of the boilers through various measures.

What initiatives have been carried out for modifications of boiler design to meet the criteria of blending of coal in the country?
Considering the coal shortage in the country and also as per CEA directives, BHEL boilers are designed to consider a 80:20 (80 per cent Indian and 20 per cent imported) blend of coals. The furnace, superheater, wind box and firing system design, mill sizing, etc. are suitably designed by BHEL to handle blended coals. BHEL boilers are designed for 100 per cent Indian coals and are currently capable of handling blended coals also.

What role is BHEL playing in emerging boiler technologies like advanced ultra supercritical and integrated gasification combined cycle (IGCC)?
In order to secure energy security through efficient firing of coal, BHEL has joined hands with Indira Gandhi Centre for Atomic Research and NTPC to design, develop and build advanced ultra super-critical boilers under the national mission on clean coal technologies, which is ninth under the national action plan for climate change. The mission will foster work on advanced ultra supercritical technology, IGCC and carbon capture and sequestration, among others.

Here, BHEL will design, manufacture and commission advanced ultra super-critical boilers. Plants operating with advanced ultra supercritical boilers can achieve a higher efficiency than that of plants with supercritical boilers. The power plant design will be made to withstand 300 Kg/cm2 and 700 degree centigrade. This will be developed by 2017.

Explain BHEL's role in IGCC technology?
BHEL is one of the few companies worldwide, involved in the development of IGCC technology, which would usher in clean technology. It is different from conventional boiler technology. In boiler, coal is burnt in a combustion chamber under stoichiometric conditions to produce steam which operates a steam turbine for power generation, whereas in IGCC, the coal is gasified under sub-stoichiometric conditions to produce synthetic gas, which operates the gas turbine in a combined cycle plant to generate power.

Towards this, a 6.2 MW IGCC research facility has been set-up at the unit and further field trials at large scale carried are being carried out. The trials done at the research facility reflect typical situation that may come in a larger commercial plants of higher capacities. BHEL has established the relevant technology for gasification of high ash Indian coals and the development is totally in-house.

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