Ulrich Hauser - ABB Kraftwerke AG. Department " Steam Generation Plants" GERMANY

The careful exploitation of resources and the protection of the environment require concepts f or power plants with a high efficiency and a high power output. These recommendations do not only exist for the conceptual design of new plants, but also have to be taken into consideration for already existing plants. The possibilities of upgrading and repowering especially for oil or gas fired plants will be discussed in this paper. Starting point for the engineering works is the combustion turbine (CT). The fluegas of CT possesses unused heat and oxygen. The use of the fluegas heat leads to a conventional combined cycle power plant, consisting of combustion turbine, waste heat recovery boiler (WHRB) and gas turbine. This solution increases the total power output by roughly 50 of the CT-power output and the efficiency by nearly 50 By using the oxygen of the fluegas for additional firing the power output could be increased, too. Therefore an additional burner must be installed in the channel between CT and WHRB. If the oxygen content is totally used for supplimentary firing with very low excess air a steam plant capacity of 5 to 6 times could be reached. In such a plant the CT replaces the FD-fan. The planning tasks for a substitution of a FD-fan by a CT in an existing plant will be discussed by showing the possible variants and limiting effects. By using a flow scheme for the design works the necessary alterations for the existing plant will be pointed out. With this combination an improvement of efficiency by 11 % is possible.