Combined cycle (gas & steam)
power station
1-Introduction:
.A Combined Cycle Power Plant as shown fig (1), produces high power outputs at high efficiencies (up to 55%) and with low emissions. In a Conventional power plant we are getting 33% electricity only and remaining 67% as waste by using combined cycle power plant we are getting 68% electricity.
.A basic combined cycle power plant combines a gas turbine and a steam unit all in one, although there are other possible configurations. As combustion turbines became more advanced in the 1950s, they began to operate at ever high temperatures, which created a significant amount of exhaust heat.55In a combined cycle power plant, this waste heat is captured and used to boil water for a steam turbine generator, thereby creating additional generation capacity. Combined cycle plants have thermal efficiencies in the range of 50 – 60 percent. Historically, they have been used as intermediate power plants, generally supporting higher daytime loads.
2- Parts and equipment's:
.Combined cycle power plant normally means combination of two type of turbine like a Gas turbine and a steam turbine. The turbine is combined with one cycle. The energy of two turbines are flowing through one turbine. Sometime the CCPP is called Co-Generation plants.
Initially the Co-generation system is consist of six major components
· A furnace (Used to converting chemical energy into heat energy).
· Engine or turbine (Work as prime mover).
· Generator( Used to convert chemical energy into electricity)
· Heat exchanger.
· Electrical switchboard.
· Hydraulic interconnections.
3- Working Principle:
.1st the fuel is burned into the furnace and produce 700-1200°C that helps to create steam by steam generator. Then the steam through the steam generator which create mechanical energy. That’s mechanical energy is converted to electrical energy.
.2nd the fuel burned in the gas turbine which converted into mechanical energy and thermal energy. In the gas turbine to produce electricity only need 400-600° c thermal energy, By the way another 400-500° c thermal energy are reduced in the temperature. Therefore heat exchanger is installed to recover the 400-500° c in the exhaust gases of the gas turbine. Then the exhaust gases (400-500° c) are flow through the Heat Recovery Steam Generator (HRSG). Then the output steam of Heat Recovery Steam Generator (HRSG) flow through the steam turbine.
4- Advantages:
The combined cycle plant takes advantages are:
1- The efficiencies of running both cycles simultaneously to produce power very cost effectively during those peak periods thereby saving the utility from having to purchase power to meet spikes in demand.
2- Their ability to respond quickly to fluctuations in customer demand for electricity.
3- Very low toxic emissions.
4- Run on a wide Varity fuels.
5- High operating speeds.
5- Disadvantage:
1- The gas turbine can only use Natural gas or high grade oils like diesel fuel. Because of this the combined cycle can be operated only in locations where these fuels are available and cost effective.
2-higer cost.
3-longer start-up.
4-less responsive to power demands.
5-shirll whining noise.
6-Conclusion:
.Combined cycle power plants meet the growing energy demand, and hence special attention must be paid to the optimization of the whole system. Developments for gasification of coal and use in the gas turbine are in advanced stages.
Once this is proven, Coal as the main fuel can also combined cycle power plants meet the growing energy demand, be used in the combined cycle power plant. The advances in cogeneration-the process of simultaneously producing useful heat and electricity from the same fuel source-which increases the efficiency of fuel burning from 30% to 90%, thereby reducing damage to the environment while increasing economic output through more efficient use of resources.
7- Choice of site:
1-water availability: located near rivers or canal.
2-land cost: needed to be cheap less construction cost.
3-near to load centers: less transportation cost.
4-distance from populated area: as it causes pollution.
8- Recommendation:
- We must search about another fuel because the diesel and natural gas is high cost.
-This type is the most type of station generation because high efficiency.
Refrences: -9
-http://www.siemens.com/about/sustainability/en/environmental-portfolio/products-solutions/fossil-power-generation/combined-
cycle-power-plants.htm
-diesel power generation plant, for engineering.
-http://www.slideshare.net/cleopettra/group5-44030866?qid=8dde03be-f315-4081-8879-33eccdd015e2&v=&b=&from_search=2
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