Patent Application
20130174555
The present invention relates to a power station unit or a power station, having at least two electric generators for generating electricity, wherein a gas turbine is provided for driving one of the at least two generators and a reciprocating piston engine is provided for driving the other of the at least two generators, wherein the reciprocating piston engine has at least one charge-air inlet for precompressed charge air and the gas turbine has at least one compression stage.
The present invention is preferably directed towards stations for generating electricity of 10 to 100 MW electrical output, wherein the load can be varied between 30% and 115% of the full load.
U.S. Pat. No. 3,498,053 (Johnston) describes a reciprocating piston engine/turbine combination in which exhaust gas is fed from the reciprocating engine to the turbine and the turbine drives a compressor which in turn supplies compressed air for supercharging and cooling the reciprocating engine. Here, the entire mass flow of the compressor/turbine assembly is guided via the reciprocating engine. The turbine does not have a combustion chamber of its own.
EP2096277A1 (MAGNETI MARELLI) describes a supercharged internal-combustion engine wherein turbine (13) and compressor (14) of the charging system are mechanically independent. Here too, the supercharging unit is not capable of delivering power via a combustion chamber of its own.
U.S. Pat. No. 3,444,686 (Ford Motors) describes an arrangement of engine and gas turbine in which the engine exhaust gases are mixed with the turbine exhaust gases in order to reduce pollutants. Use of compressed air from the compressor (16) in the internal combustion engine (12) is not provided.
In the power segment in question, gas turbine stations, combined cycle power plants (CCPPs) and gas or diesel engine stations are generally used.
These technologies each have different merits and disadvantages, with the result that the selection is limited accordingly depending on requirements or boundary conditions.
Thus the advantages of a pure gas turbine station are a high power density and the specific investment costs, which reduce as output increases, as well as the low costs of service and maintenance. The low efficiency compared with a CCPP is disadvantageous.
CCPPs in turn have very high efficiencies of up to approx. 60%, but can only be realized cost-effectively for stations above approx. 200 MW output. Moreover, their behavior under partial load is disadvantageous.
Gas engine stations are very cost-effective for power station outputs of up to approx. 100 MW. They have high full load and partial-load efficiencies and can react rapidly to changes in load requirements. If, in addition to electricity generation, the engine waste heat is also used, overall efficiencies (electric+thermal) of up to 90% can be achieved.
One of the disadvantages of gas engine stations are the relatively high costs of service and maintenance and the relatively large specific space requirements.
EP 1 990 518 A2 and U.S. Pat. No. 6,282,897 B1 disclose arrangements having at least two electric generators for generating electricity, wherein a gas turbine is provided for driving one of the at least two generators and a reciprocating piston engine is provided for driving the other of the at least two generators, wherein the reciprocating piston engine has at least one charge-air inlet for precompressed charge air and the gas turbine has at least one compression stage.
EP 1 990 518 A2 deals with a special drive system for aircraft since a particular problem with aircraft is that a stall in the turbine can occur at low speeds and high pitch angles (e.g. during the take-off phase).
U.S. Pat. No. 6,282,897 has the object of increasing the range of a vehicle with hybrid propulsion system.
It is clear that the teachings of these citations are not relevant with respect to a stationary power station unit according to the invention.
The object of the invention is to further develop a generic power station unit such that the most advantageous way of generating electricity is accomplished.
This object is achieved by a power station unit with the features of claim 1.
Further advantageous embodiments are defined in the dependent claims.
A possible mode of operation of the power station unit according to the invention could be as follows, wherein it is assumed below in a simple manner that a reciprocating piston engine is in the form of a gas engine:
The gas engine and the gas turbine each drive a generator, which generators feed the electricity generated into the consumer grid.
Starting from stopped mode of the station, the commissioning, start-up and ramping up are performed for example in the following way:
The fuel is supplied to the combustion chamber(s) depending on output requirements in such a way that optimum efficiency or maximum possible output is achieved.
For optimum adaptation of the compressor delivery to the gas turbine output or to the operating requirements, inlet guide vanes are advantageously used upstream of the compressors.
The air quantity for the gas engine is preferably adjusted and optimized by one or more throttle valve(s) (e.g. throttle flap(s)), wherein throttling should be avoided as far as possible in stationary full load operation.
To regulate the output of the turbine, the fuel supply to the turbine combustion chambers is varied.
The output of the unit should in principle be above approx. 75% of the full load in order to achieve optimum efficiency.
In the case of output requirements below 75%, modular power station complexes with a number of individual power station units as smaller output units prove very advantageous, wherein the reduced outputs can be achieved in the respective full load operation of part of the power station units while the remaining parts are switched off.
After the power station unit consisting of gas engine and gas turbine has been started and ramped up, said power station unit is operated in an output range between approx. 60 and approx. 115% of full load output, wherein the 115% correspond to the overload that can be achieved for a short time to cover consumption peaks.
To achieve maximum efficiency, it is advantageous if the gas turbine has a high-pressure combustion chamber (HP combustion chamber) and a low-pressure combustion chamber (LP combustion chamber), wherein the energy supplied to the turbine burners is preferably divided up in such a way that a high-pressure combustion chamber receives approx. ¾ and the low-pressure combustion chamber receives approx. ¼ of the quantity of gas supplied to the turbine station.
The energy supplied to the high-pressure combustion chamber is limited by the maximum permissible gas temperature for entry into the turbine, wherein the combustion air ratio and final compression temperature are the most important parameters influencing the gas temperature.
The unit is switched off in an opposite manner to the ramping-up procedure, wherein the energy supply to the burners is interrupted and the turbine generator is taken off the grid.
The output of the gas engine is throttled via the throttle valves for the air and gas. To reduce the load on the gas engine more rapidly, a pressure relief line with shut-off valve is provided that ensures rapid pressure release in the mixture-distribution line of the engine.
To reduce the NOx concentration in the engine exhaust gas, in an embodiment example the injection of a reducing agent into the engine exhaust gas is provided, wherein the reducing agent is mixed with the exhaust gas in a mixing section and after heating triggers a thermally supported reduction reaction with the NOx. The NOx can thus be reduced to a level such that the limits provided for gas turbines are not exceeded.
Further advantages resulting from the proposed integration of gas engine and gas turbine include the following:
The gas engine can support and shorten the start-up and ramping-up procedure of the gas turbine. For example, the engine exhaust gas heats the LP combustion chamber and LP turbine and preheats the HP combustion chamber via the recuperator.
In the case of short interruptions to the grid, the relatively high moment of inertia of the turbine rotor keeps the engine within the permissible frequency limits (grid codes).
In the low-pressure combustion chamber, the CO and HC emission of the gas engine is eliminated without catalytic aftertreatment.
With regard to the electrical output generated, the quantity of exhaust gas is less than in pure gas turbine stations or CCPPs.
This has advantages for the dimensioning of the exhaust gas station and with respect to minimization of the exhaust gas loss.
The output of the turbine station can be increased, for example, by increasing the energy supplied to the low-pressure combustion chamber. This is possible since the turbine inlet temperature here is still significantly below the temperature limit permitted for the material of the turbine blades. Although this measure somewhat reduces the efficiency of the turbine process, this disadvantage can be more than outweighed by the advantage of the increased efficiency, for example for covering consumer peaks, for more rapid increase in output or for compensating for reductions in output at very high external temperatures.
Referring to the numerical example mentioned above, an increase in the fuel energy supplied to the LP combustion chamber
Further advantages and details of the invention are apparent from the figures and the associated description of the figures. There are shown in:
The gas turbine 1 is designed per se according to the state of the art and has at least one compression stage 11 and an expansion stage 14, which are connected to each other here by a common shaft 17 for the transmission of a rotational movement. The invention can of course also be used if, instead of a single common shaft 17, coupled rotating components are provided.
Ambient air is supplied to the compression stage 11 via a line 110. Said compression stage 11 compresses the ambient air and conveys part of the compressed air to a turbine combustion chamber 16 via a line 111. The turbine combustion chamber 16 furthermore has a propellant supply 19. In a manner known per se, a further line 112 leads from the turbine combustion chamber 16 to the expansion stage 14, where the medium is relieved of pressure and power is delivered.
The reciprocating piston engine 2 is also provided with a gas line 22 via which propellant can be supplied to the engine. The reciprocating piston engine 2 furthermore has a charge-air inlet 21, which according to the invention is connected to an exit of the compression stage 11 via a charge-air line 41. In this way the charge air required to operate the reciprocating piston engine 2 is provided via the gas turbine 1. Exhaust gas can be discharged via an exhaust gas exit 23, not shown in
The power station unit of
The gas turbine 1 here has a first compression stage 11 and a second compression stage 12, as well as a first expansion stage 14 and a second expansion stage 15. The unit just discussed consisting of the compression stages 11, 12 and the expansion stages 14, 15 is arranged along a common shaft 17. A generator 3 for generating electricity and a gas compressor 13 for compressing the propellant supplied via the propellant supply 19′ are coupled to the shaft via gearbox 18. The propellant compressed by the gas compressor 13 is cooled via a cooler 412 before it is supplied on the one hand to the turbine combustion chamber 16 via a throttle flap 413 and the line 19 and on the other hand to the gas engine 2 via a further throttle flap 413 and the line 22. Propellant which is used to further treat exhaust gas from the reciprocating piston engine 2 (see description below) can also be supplied to a reaction chamber 410 via a further throttle flap 413 and the line 411. For aftertreatment of the exhaust gas, a reducing agent can additionally be added via the reducing agent supply 415.
The embodiment of
A number of throttle flaps 413, which can be used to throttle the respective media, can also be seen in
To reduce the load on the reciprocating piston engine 2 more rapidly, a pressure relief line with a shut-off valve 414 is additionally provided here via which rapid pressure release in the mixture distribution of the reciprocating piston engine 2 can be achieved.
In the present embodiment example, the reciprocating piston engine 2 has a mean effective pressure of 30 bar and an efficiency of 48%.
The first turbine stage 14 is designed as a high-pressure turbine. The second turbine stage 15 is designed as a low-pressure turbine.
A further advantageous embodiment of the invention is evident from
Some data for the embodiment of
The reciprocating piston engine 2 has a mean effective pressure of 35 bar here, which corresponds to an output of 17.5 MW with the piston displacement and rotational speed of the engine used. The efficiency is again approx. 48%.
In a specific embodiment example, precompressed air with a pressure of 20 bar is supplied to the turbine combustion chamber 16 at a temperature of 335° C. The quantity of gas supplied to the combustion chamber corresponds to an output of 90 MW. The inlet temperature in the high-pressure expansion stage (turbine 14) is approx. 1100° C. The medium leaves the first expansion stage 14 with a pressure of 7 bar and a temperature of 830° C. Exhaust gas leaves the second expansion stage (low-pressure turbine) 15 with a temperature of 450° C. The achievable net output is 33.1 MW with an efficiency of 39%.
The overall system thus has an output of 50.6 MW with an efficiency of 42%.
| Number | Date | Country | Kind |
|---|---|---|---|
| A 1480/2010 | Sep 2010 | AT | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/AT2011/000361 | Sep 2011 | US |
| Child | 13783864 | US |
