Wednesday, June 29, 2011
6:06 PM | Posted by
Editor in chief |
Combustion turbine (CT) power plants burn fuel in a jet engine and use the exhaust gasses to spin a turbine generator. The air is compressed to a very high pressure. Fuel is then injected into the compressed air and ignited, producing high-pressure and high-temperature exhaust gasses. The exhaust is moved though turbine blades much the same way steam is moved through turbine blades in a steam power plant.
The exhaust gas movement through the combustion turbine results in the rotation of the generator rotor, thus
producing electricity. The exhaust from the CT remains at a very high temperature and pressure after leaving the turbine.Above figure shows a combustion turbine generator.
One of the advantages of combustion turbines is that they can actually be designed to be remotely controlled for unmanned sites. They offer fast startup times and fast installation times. In some cases, the purchase of the combustion turbine generator system can be “turnkey,” that is, the owner simply contracts for a complete installation and takes over when the plant is finished and ready to operate.
In most cases, the combustion turbine generator package is a completely self-contained unit. In fact, some of the smaller-capacity systems are actually built on trailers so that they can be moved quickly to sites requiring emergency generation.
Combustion turbines can be extremely responsive to power system
changes. They can go from no load to full load and vice versa in a matter of seconds or in a matter of minutes.
The disadvantages are limited fuel options (diesel fuel, jet fuel, or natural gas) and inefficient use of exhaust heat.
There are several environmental issues related to the use of combustion turbines. Without appropriate treatment, the exhaust emissions can be very high in undesirable gases. The high temperatures in the combustion chamber will increase the production of nitric oxide gases and their emissions.
Depending on the fuel used, there can be particulate emissions problems.
That is, particles or other materials tend to increase the opacity(smoke) of the gases. Sound levels around combustion turbine installations can be very high. Special sound reduction systems are available and used. (Note: combustion turbines are typically jet engines, very similar to those heard at airports.)
The heat rate or efficiency of a simple-cycle combustion turbine is not very good. The efficiencies are somewhere in the range of 20 to 40% maximum.
One effective way to overcome some of the cost is to incorporate a heat exchanger so the exhaust gases can be used to generate steam that will drive a secondary steam turbine. Many CTs are used as combined-cycle power plants.
Do you feel confused confused about this lesson? Leave your question now in a comment.
Labels:
Module(2)