Cement, Energy and Environment

l I the output of electrical energy for a given amount of energy input, the higher the efficiency. If the energy input to the cycle is kept constant, the output can be increased by selecting elevated pressures and temperatures for the water-steam cycle. Increased thermal efficiency observed when the temperature and pressure of the steam is increased. By raising the temperature from 580'C to 760'C and the pressure out of the high pressure feed-water pump from 33 Mpa to 42MPa, the thermal efficiency improves by about 4 per cent (Uitra– supercritical steam condition). Because of its abundance and affordability, coal continues to be a major energy source for power producers worldwide. However, as carbon consciousness becomes more prominent, technologies for gaining efficiency and reducing emissions from coal-fired plants become more important. That is one reason why supercritical and ultra-supercritical boiler technologies are re-emerging as new materials and designs help drive higher efficiency levels and ease of operation. Today's supercritical units can achieve thermal efficiency of more than 45 per cent, compared to a typical sub-critical plant's 30 - 38 percent. Ultra supercrltical power plants In the quest for higher efficiency the trend is to go for still higher operating pressures. The next generation of power plants will operate with steam pressures in the range of 300 bar. These are the ultra super critical power plants. Ultra supercritical units operate at temperatures of 615 to 630 deg c. Majority of new supercritical units are being built in Asia, especially China, which is building power plants at a rapid pace. These new plants will provide infrastructure to support booming economies and bring electricity to areas previously unconnected to the grid. In support of China's growing power requirements, 90 GW of new capacity is planned over the next two years. Two noteworthy fast-track projects in China are Huaneng Power's 4,000 MW Huaneng Yuhuan plant, and China Huadian's Zouxian units 7 and 8, which are among the first ultra-supercritical units in China to have a 1,000 MW output rating. The India scene Supercritical boilers are more efficient and consume less fuel than sub-critical ones and in India are built in capacities of 660 MW and 800 MW. The Indian government has launched supercritical power programme on the lines of the US, Japan, Germany, Korea and Russia. According to power ministry officials the super critical technology will result in saving of about 4 per cent of fuel and correspondingly less emission. Most of the 1,00,000 MW of pbmn~ ~p~ addition fn tbe comrtry during the 12 01 five year plan (2012-2017) will be through supercritical technology As a signatory to the Kyoto Protocol, India has decided that the methodology for the award of the proposed 7 units of 660 MW and 6 units of 800 MW would pave the way for progressive indigenization of supercritical technology. The government is striving to meet the capacity addition target of 78, 700 MW in the 11 th plan. Several companies have already expressed interest to augment or set up manufacturing facilities in the country for supercritical units. These include BHEL, Boiler and Turbine Generator(TG) and Ansaldo Calide (Boiler), L&T - MHI (Boiler and TG), Toshiba- JSW (TG) and Alstom-Bharat Forge (TG). L & T already had a tie-up with Mitsubishi Heavy Industries of Japan for manufacturing supercritical steam turbines and generators in India. Currently supercritical technologies are under installation at Sipat and Barh thermal power stations of NTPC. The Ultra Mega Power Projects (UMPP) are also being envisaged to be set up with supercritical parameters. Tata Power's Mundra project imported turbines from Toshiba and boilers from Doosan, Korea. NTPC and the state utilities, in addition, have proposed to set up a number of 600/800 MW power stations based on supercritical technology. The list of projects include NTPC's Darlipalli in Orissa (4x800 MW), NTPC's Tanda expansion in Uttar Pradesh (2x660 MW), NTPC's Pench in Madhya Pradesh (2X660 MW), NTPC– Uttar Pradesh Joint venture's Mejja in UP (2x660 MW), NTPC– Bihar JV's New Nabingar in Bihar (2x660MW), Mahagenco's in Koradi in Maharashtra (3x660 MW), Mahagenco's Dhopawe in Maharashtra (2x800 MW), BHEL-UP JV's Obra in UP(2x800 MW) and BHEL-Tamil Nadu Electricity Board JV's Udangudi in Tamil Nadu (2x800 MW). Thus, most of the 100,000 MW of planned capacity addition in the 12th five year plan (2012- 2017) will be through supercritical technology. Because of the efficiency and environmental benefits they bring, supercritical technologies should continue to figure prominently in new base load plants being built in Asia and around the world. Courtesy: the energy business, July 2010, P44-45. 27