Retrofitting a heating steam extraction facility in a fossil-fired power plant

Abstract

A method for retrofitting an existing steam turbine with a steam extraction facility is provided. The stem turbine has a plurality of pressure stages and is integrated into a fossil-fired steam power plant. A steam extraction line is connected to one pressure stage or between two pressure stages of the steam turbine, and a heating steam turbine is connected into the steam extraction line.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is the US National Stage of International Application No. PCT / EP2011 / 071180 filed Nov. 28, 2011 and claims benefit thereof, the entire content of which is hereby incorporated herein by reference. The International Application claims priority to the German application No. 10 2010 062 623.6 DE filed Dec. 8, 2010, the entire contents of which is hereby incorporated herein by reference.BACKGROUND OF INVENTION[0002]There is a need to adapt existing fossil-fired power plants to changing requirements. Steam power stations or combined-cycle gas and steam power stations in particular are often subject to demands for adaptation, especially for a retroactive implementation of the capability to extract steam from the steam section of the power station. This additionally extracted steam can be required as process or heating steam for internal processes within the power station process or for supplying other processes outside of the ac...

AI Technical Summary

Benefits of technology

[0007]The object of the invention is therefore to disclose a method for retrofitting a steam extraction capability in order to tap steam from the steam process of a fossil-fired power plant, which capability can be realized in a simple and cost-effective manner, and which in addition is thermodynamically favorable, so that the efficiency losses due to the additional steam extraction are minimized.

Problems solved by technology

Extracting steam from the steam turbine process reduces the remaining steam volume which is still available for the steam turbine process and which now can make no further contribution to the generation of steam.

As a consequence the extraction of steam from the steam turbine process reduces the efficiency of a steam power plant.

However, this concept would lead to an increased initial investment since the turbine cannot be optimized simultaneously for operation without extraction and with extraction.

Retrofitting a steam turbine plant with steam extraction capability is often technically demanding and complex, as well as cost-intensive in terms of implementation.

If a steam extraction capability is realized only as a result of a retrofit, substantial losses in efficiency are likely into the bargain.

Converting an existing steam turbine plant to provide a retroactive steam extraction capability, in particular for tapping low-pressure steam, can be very complicated and labor-intensive, however.

Thus, for example, the dimensions of the power house may not be sufficiently large to accommodate the additional piping for extracting the steam, or the steam turbine or, as the case may be, the power station process is not suitably configured for steam extraction.

In steam turbines having a medium- and low-pressure stage housed in a single casing, on the other hand, it is often not feasible to carry out retrofits in order to extract the large volume of steam required, for which reason the turbine has to be replaced in this situation.

Extracting steam from other sources within the power station process is often likewise not cost-effective or possible in a suitable manner.

Thus, for example, extracting steam from a reheat line of the steam turbine leads to load imbalance in the boiler if no further expensive and complex measures are taken.

Extracting higher-value steam for the carbon dioxide separator must also be ruled out unless further measures are undertaken, since this leads to unacceptable energy losses.

A further problem that arises with the retrofitting of a steam extraction capability is that when the steam extraction is discontinued the steam that is now not required abruptly accumulates to excess.

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