Power plants – Motive fluid energized by externally applied heat – Noncommunicating heat transferring motive fluid system
Patent
1986-11-14
1987-10-27
Ostrager, Allen M.
Power plants
Motive fluid energized by externally applied heat
Noncommunicating heat transferring motive fluid system
F01K 2302
Patent
active
047020814
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a combined steam and gas turbine plant for the production of electrical energy, having a steam generator which is followed in a circuit by a steam turbine driving an electrical generator, from which the steam, after liquefaction in a condenser, is returned to the steam generator as feed water by means of a condensate pump through at least one preheating stage, and having a gas turbine driving a second electrical generator, which is driven by a turbine gas, preferably nitrogen or helium running in the closed circuit, and whose outlet for the heated turbine gases is connected by a conduit to heating surfaces in the steam generator and to the heat exchanger forming the preheating stage following the heating surfaces, which is inserted into the branch of the circuit that returns the condensate to the steam generator, the steam generator in combination with the gas turbine being so constructed that the evaporation of the feed water takes place at supercritical pressure, and the steam turbine is divided into at least two turbine parts and an intermediate superheating stage is inserted between each pair of successive turbine parts.
Whereas in plain steam engines today net efficiencies of up to about 40% are achieved, in the combined steam and gas turbine power plants constructed and planned to date, wherein a single gas turbine process is followed by a steam process with a single intermediate superheating of the steam, this efficiency is increased to about 45%.
In a known plant of the kind mentioned above (DE-OS No. 26 56 463), in which the thermal energy is obtained from the heat produced by the fission of nuclear fuels in a high-temperature reactor, the thermal energy is removed by a gaseous coolant, e.g. helium, which circulates in a closed circuit. This cooling circuit is simultaneously the closed gas turbine circuit, so that the reactor coolant is simultaneously the turbine gas.
It is the object of the invention, on the other hand, to create a combined steam and gas turbine plant, powered by firing with conventional fossil fuels, whose efficiency will be further optimized in comparison with the known, conventionally fired plants, while the production of combustion exhaust gases will be minimized.
Setting out from a plant of the kind mentioned in the beginning, this object is achieved according to the invention by constructing the gas turbine as a multi-part turbine with multiple expansion and intermediate heating of the turbine gases, by making the heating surfaces of a coal-fired boiler to be the heaters for the turbine gases as well as the intermediate superheaters in the steam circuit, and by providing the coal-fired boiler with two separate firing chambers in tandem having separate heating surfaces, associated one with the heaters and one with the intermediate heaters of the gas turbines.
The heating surfaces of the intermediate superheaters of the steam turbines are preferably connected to the output from the heating surfaces forming the intermediate heater of the gas turbine, and associated with the first firing chamber of the boiler.
To attain the desired reduction of the combustion exhaust gases and to improve efficiency, it is furthermore recommendable to connect to the output of the turbine gases from the turbine a heat exchanger through the other side of which at least a portion of the air being fed to the boiler as combustion air passes and is preheated.
The invention will be further explained in the description of an embodiment that follows, in conjunction with the drawing which is a circuit diagram of a combined steam and gas turbine plant powered by a coal-fired boiler having two firing chambers in tandem.
The combined steam and gas turbine plant shown in the drawing is divided into a steam power plant part represented on the right in the drawing, which has a three-phase electrical generator driven by a steam turbine 226, and a gas turbine plant part represented on the left in the drawing, which has a second three-phase electrical generator driven by a gas turbine 248.
REFERENCES:
patent: 4041709 (1977-08-01), Rajakovics
patent: 4428190 (1984-01-01), Bronicki
Ostrager Allen M.
TCH Thermo-Consulting-Heidelberg GmbH
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