Power plants – Motive fluid energized by externally applied heat – Process of power production or system operation
Reexamination Certificate
2000-05-30
2001-05-22
Nguyen, Hoang (Department: 3748)
Power plants
Motive fluid energized by externally applied heat
Process of power production or system operation
C060S679000
Reexamination Certificate
active
06233939
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method of operating a steam power station. Steam generated in an evaporator is condensed in a condenser after flowing through at least one turbine. The resulting condensate is preheated and supplied to the evaporator as feedwater.
In such conventional steam power stations it is suggested that the condensate used as feedwater be preheated up close to the boiling temperature by means of partial steam mass flows from the turbine steam content. As a result, the thermodynamic efficiency of the entire process increases. However, due to the steam extraction, the following steam-turbine stages can draw less power from the steam fluid.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a novel method of operating a steam power plant, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which, despite a thermodynamic increase in the efficiency of the entire process, prevents a reduction in the power output at the following steam-turbine stages.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method of operating a steam power station, which comprises:
generating steam in an evaporator;
conducting the steam through at least one turbine;
subsequently condensing the steam in a condenser to obtain condensate;
operating a fuel cell and generating waste heat; and
preheating the condensate obtained in the condensing step with the waste heat from the fuel cells and supplying the preheated condensate to the evaporator as feedwater.
In other words, the feedwater is used directly for cooling the fuel-cell process, in the course of which the temperature of the condensate increases. Due to the preheating of the feedwater from the waste heat of the fuel cells and the associated increase in the steam quantity participating in the expansion, an increase in the efficiency of the steam process is achieved.
In accordance with another feature of the invention, the condensate obtained in the condensing step is preheated with the waste heat from the fuel cells and a heat content of a partial steam quantity tapped from the steam-turbine process, before it is supplied back to the evaporator as feedwater. This is thus a combination of external heat supply via the fuel cells and a partial steam quantity from the steam-turbine process. The preheating can therefore be adapted in a flexible manner to the criteria of the entire process.
With the above and other objects in view there is also provided, in accordance with the invention, a steam power station in which the above-noted method is applied. The power station comprises an evaporator for generating steam, at least one turbine connected to receive the steam generated in the evaporator, a condenser connected to receive the steam after having traversed the at least one turbine and for producing a condensate, a line connection between the condenser and the evaporator for feeding back the condensate to the evaporator, an apparatus for preheating the condensate connected to the condenser, and at least one fuel cell generating waste heat for heating the condensate.
In other words, the steam power station for carrying out the method includes a fuel-cell arrangement integrated in the preheating apparatus. The extensive use of the conventional power-station components permits simple implementation of the concept according to the invention even in existing plants.
In accordance with an additional feature of the invention, there is provided a bypass line in which the at least one fuel cell is connected, the bypass line circumventing the apparatus, a throttle valve connected in a feed leading to the at least one fuel-cell and a throttle valve connected in a return leading away from the at least one fuel-cell, a condensate pump connected to the condeser, a line connected between the condensate pump and the apparatus, a further throttle valve in connected in the line between the condensate pump and the apparatus, a feed branching off from between the condensate pump and the further throttle valve, and a connecting line with a throttle valve running between the at least one turbine and the apparatus.
In accordance with another feature of the invention, the at least one fuel cell is one of a plurality of fuel cells disposed in a fuel cell block or fuel cell arrangement.
Here, variable flow ratios can be set as a function of the thermodynamic conditions. It is possible to heat the condensate simultaneously by the tapped steam of a turbine stage and by the fuel-cell waste heat. Likewise, heating of the condensate can be carried out solely with the fuel-cell arrangement or solely with the tapped turbine steam quantity.
In accordance with a further feature of the invention, the preheated condensate is passed into the system at different positions between the apparatus and the evaporator. The positions are determined in dependence on the waste-heat capacity of the fuel cells.
In accordance with again a further feature of the invention, the condensate heated by the waste heat of the fuel cell(s) can be supplied to a heat sink.
In accordance with a concomitant feature of the invention, an inverter is connected downstream of the fuel-cell block.
To increase the flexibility, a pure steam process, a combined fuel-cell/steam process or a pure fuel-cell operation is optionally possible.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method of operating a steam power station, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.
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Behnke Klaus
Ngo-Beelmann Ung-Lap
Witt Michael
ABB Patent GmbH
Greenberg Laurence A.
Lerner Herbert L.
Nguyen Hoang
Stemer Werner H.
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