The present invention relates to an arrangement for improving the efficiency of a power plant operated by burning fossil fuel etc., wherein the combustion air is preheated by recovering a portion of the heat contained within the flue gas and wherein a portion of the heat energy contained within the flue gas and/or in the preheated combustion air is transferred to the process medium by bypassing the heat exchanger for heating the combustion air.
It is conventional in power plants operated by burning fossil fuel to preheat the combustion air to be introduced into the steam generator by recovering a portion of the heat energy contained within the flue gas of the steam generator. This recovering is carried out with recuperative or regenerative heat exchangers, for example, in the form of tube or plate heat exchangers or rotatably driven air preheaters. By partially using the heat energy contained within the flue gases for preheating the combustion air the efficiency of the power plant is increased.
In addition to this preheating step of the combustion air, it is known to transfer a portion of the heat energy contained within the flue gas onto the process medium by bypassing the combustion air preheating system for example, for heating the feed water or for generating steam which then can be used for external purposes or can be reintroduced into the power plant process.
It is therefore an object of the present invention to improve on the known arrangement for improving efficiency of a power plant that uses fossil fuel such that an additional increase of the efficiency can be attained.