(70) Therefore, the risk of sulphuric acid dew point attack ... - DTI Home

More documents

Recommendations

Info

Figure 32: Effect of gas turbine cooling methods on efficiency (Courtsey of Innogy plc) [6] . (83)
The world’s first operational steam cooled gas turbine, built by MHI, was commissioned in Japan in 1998 and installed in Unit 4 at the Higashi Niigata Power Station. In the United States, it was not until early 2001 that Siemens- Westinghouse achieved commercial operation with a 360 MWe power plant located in Massachusetts followed immediately by a second 249 MWe plant in Florida. The gas turbine installed in the American plants is considered “partially” steam cooled, with just the first stage vanes being incorporated within a closed loop. Whilst specific teething problems were found during start up conditions of the W105G gas turbine, a cycle efficiency of ~58% (LHV) was achieved with this technology. More recently General Electric installed their first H-class unit at the Baglan Energy Park in South Wales. This unit, which features steam-cooled rotor and stator vanes, is currently under commissioning tests with engineers aiming to break the 60% (LHV) cycle efficiency barrier. 4.3.2 Fuel Heating In the late 90’s methods of heating fuel prior to combustion in the gas turbine were being introduced to the combined cycle in order to enhance efficiency. Preheating of the fuel results in a reduction in the amount of fuel needed to achieve a given firing temperature in the gas turbine. However, whilst the efficiency of the cycle improves, the plant power output is found to reduce slightly. This originates from the fact that when a gas turbine is fed warmer fuel, it requires less mass flow of that fuel to obtain the previous cold-fuel firing temperatures, thus the exhaust mass flow and water vapour content of the combustion products is lower. Less power is therefore obtained from the combustion gas expansion through the turbine. Furthermore the HRSG generates a little less steam from the decline in gas turbine exhaust mass flow and hence a drop in steam turbine power also occurs. However, the overall improvement in the cycle efficiency results from the fact that the energy diverted from producing steam power is of relatively low grade, and is better employed as a heating medium for the fuel. The fuel heating source may be either steam or water. For the case of steam this can originate from the steam turbine bleed or directly from one of the HRSG pressure level circuits. For the case of water heating, the hot water is drawn from the HRSG economisers. There is a threshold at which the benefits associated with the increase in efficiency are found to be at the expense of the level of electrical power produced [62] . For example fuel heating to around 200°C from an intermediate pressure economiser exit water source on a typical three pressure reheat combined cycle, results in a net heat rate gain of about 0.6% with a corresponding net power loss of about 0.3%. If the temperature of the fuel was raised to around 300°C by a high pressure economiser exit water source, the loss of power becomes more evident at 0.75% whereas the noted increase in the heat rate gain is less apparent as it only rises to 0.8%. (84)
Page 1 and 2: Therefore, the risk of sulphuric ac
Page 3 and 4: components in terms of thermal fati
Page 5 and 6: 3.8.2 Operating Costs Fixed operati
Page 7 and 8: and bio-gas from anaerobic digestio
Page 9 and 10: 4 NEW AND DEVELOPING TECHNOLOGIES 4
Page 11 and 12: many existing combined cycle gas tu
Page 13: 4.3 Improvements to Cycle and Other
Page 17 and 18: application for which OTSGs may be
Page 19 and 20: 4.3.6 Supercritical Technology Curr
Page 21 and 22: Initially, the coal is pulverised i
Page 23 and 24: Figure 33: Diagram of a typical IGC
Page 25 and 26: Plant Country Start Fuel Process MW
Page 27 and 28: • The use of HRSGs within IGCC pl
Page 29 and 30: Company Alstom Aprovis Erie Innovat
Page 31 and 32: considered the top ranking is alter
Page 33 and 34: Figure 34: Average percentage of bu
Page 35 and 36: European (CEE) countries. The marke
Page 37 and 38: 6.4.1.2 Fluctuations in the Price o
Page 39 and 40: consents policy had the effect of c
Page 41 and 42: equipment, increasing the opportuni
Page 43 and 44: 6.5.1 Possible Non-Technical Barrie
Page 45 and 46: Detailed studies of CCTs within the
Page 47 and 48: knowledge, expertise and experience
Page 49 and 50: Up until the mid 1990’s and opera
Page 51 and 52: Company Ultimate Parent Company BIB

(70) Therefore, the risk of sulphuric acid dew point attack ... - DTI Home

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?