Patent ID: 12252994

DETAILED DESCRIPTION OF THE INVENTION

FIG.1shows a compressor1(compressor) which draws in ambient air and compresses it. The air thus processed is fed via a line31(combustion air supply) to a heat exchanger designed as a recuperator2. In this recuperator2, the compressed air is heated, the heat energy coming from the exhaust gas from the combustion. After leaving the recuperator2, the air is fed to a combustion chamber3where it is mixed with fuel and burned. From there, the resulting hot exhaust gas is fed via a line33(fuel gas discharge, at the same time fuel gas supply to the turbine) to the expansion turbine4(gas turbine). In the expansion turbine4, the exhaust gas is expanded, whereby it releases a portion of its energy. The exhaust gas streams via the exhaust manifold43(exhaust gas removal) into the recuperator2. There, the exhaust gas releases heat energy to the compressed fresh air and then enters the heat exchanger5, which is designed as a superheater or ORC evaporator.

In heat exchanger5, a large part of the remaining exhaust gas energy is transferred to a working medium (so-called ORC medium). Subsequently, the exhaust gas expands into the environment53.

The ORC medium is conveyed from the storage tank9by means of a fluid feed pump10to the heat exchanger5(superheater), where it is heated and finally evaporates and then enters the expansion turbine6via the pipeline61(working medium feed). After flowing through the expansion turbine6, the ORC medium is fed via another pipeline63(working medium discharge) into the condenser7, where it condenses and is then returned in liquid form to the storage tank9via the condensate feed pump8and the return line91.

FIG.2shows a variation of the setup shown inFIG.1in such a way that compressor1, expansion turbine6and gas turbine4are arranged coupled on a shaft11and these are connected to a generator12by means of a vibration decoupling device13to a generator12. The vibration decoupling device13may be a separate module (e.g. a magnetic coupling) or optionally, e.g. a flexible part of the overall shaft (vibration damper). In this way critical bending vibrations of the shaft are damped.

The function of the variation shown inFIG.2is identical to the configuration shown inFIG.1. In addition to the arrangement of the expansion turbine (6) and the generator12on the shaft11, the special distinguishing feature is the hybrid heat exchanger21(combined heat exchanger—exhaust gas/fresh air ORC evaporator), through which the exhaust gas flows after leaving the gas turbine4through the pipe43in the direction of the exhaust gas outlet53. In this heat exchanger21, the fresh air from compressor1is first heated via line31and then enters combustion chamber3. In a step parallel to this, the ORC medium is superheated in the same heat exchanger21in a downstream process so that it flows into the expansion turbine6via the pipe61.

Under normal operating conditions, all material flows are to be conveyed continuously and with constant quantities at the design point through the systems in order to achieve high electrical efficiency.

The fields of application of the present invention result from the good scalability and the option to use a wide variety of fuels efficiently. As a decentralized system or in the form of interconnected systems (coupling of several systems), the turbine arrangement according to the invention can cover a wide range of applications. As a so-called stand-alone solution, the turbine arrangement according to the invention can supply smaller settlements completely or supplementarily with electricity, and as a combination of several turbine arrangements according to the invention, a virtual power plant can be set up with power output very precisely matched to the energy demand. For this purpose, a network of any number of turbine arrangements according to the invention can be interconnected and thus efficiently replace larger power plants. The use of biogas from agriculture, urban waste water management, natural or industrial processes or mine gases, also the use of so-called weak gases, ammonia, alcohols or synthetic fuels enables sustainable energy generation

Further advantages arise here indirectly from the reduction of the nitrogen concentration in agricultural waste and the associated reduction of the nitrate content in soils and groundwater through the utilization of ammonia from agricultural waste products. Hydrogen, synthesis gases or natural gas from fossil sources can be converted to electricity with the turbine arrangement according to the invention and thus efficiently compensate for fluctuations in the energy supply from regenerative sources in a decentralized manner. This reduces investment costs in large power grids.

Use of the turbine arrangement according to the invention in mobile applications is applicable and desirable, especially in vehicles with a high peak load requirement and a low total load (waste disposal vehicles), but also in agricultural systems or in local public transport appears to be a sensible application. Vehicles designed for long-distance operation are a possible application.

Functionally, the use of a sub-atmospherically operating turbine according to the Brayton cycle is a possible variation. In this case, the turbine is modified according to the operating principle shown inFIG.2in such a way that the compressor1generates a vacuum which draws in fresh gas through the combustion chamber3. The fresh gas is thereby drawn “backwards” through the combustion chamber3and gas turbine4and only then enters the inlet of the compressor1through the heat exchanger5,21.

According to the invention, the turbine arrangement combines the power production of a gas turbine4with a steam turbine on a shaft11in such a way that the heat energy in the exhaust gas available after the exhaust gases passes the gas turbine4is made available to a recuperator2for preheating combustion air and to a heat exchanger5,21for evaporating a vaporizable working medium. The heat energy is divided between both process media in such a way that optimum efficiency is achieved for the overall system. Energy from combustion is fed back into the gas turbine process to increase the efficiency of this sub process. The working medium to be evaporated is to be heated with the remaining energy to such an extent that it is expanded in an expansion turbine (6) (also pulse turbine or reaction turbine) with a high pressure ratio.

Ideally, the process medium is a so-called ORC (Organic Rankine Cycle)—medium, i.e. an aliphatic alcohol such as ethanol or methanol; acetone or various refrigerants (R134a etc.) are also suitable. The use of water as an evaporable working medium may be considered. The Organic Rankine Process describes the classic steam turbine process using a (mostly) organic medium that usually evaporates at temperatures lower than water. In this way, energy from low-calorific sources can still be utilized with corresponding efficiency.

The system components of an embodiment according to the invention are coupled with each other in a modular manner and can be adapted or exchanged at any time for maintenance work or adaptation to changed environmental conditions. The modular design of the system is specific and thus part of the invention In an advantageous embodiment of this arrangement, the combustion air is already compressed to such an extent that recuperation is not necessary or is only necessary to a small extent, so that the combustion energy can be largely made available to the downstream steam process to further increase the overall efficiency of the system. It is relevant here that high compression can be achieved by multiple compression or by a high-compression radial stage, but then massive overlaps with conventional gas turbines are to be considered.

Ideally, compressor1and gas turbine4are designed as radial runners and are single-stage. A multistage arrangement of these components is a possible adaption for higher power outputs. The expansion turbine6for the steam or ORC process, which is also single-stage, is mounted centrally between the two systems or optionally between generator12and gas turbine4.

The bearing arrangement of a system according to the invention should preferably be designed by means of air bearings; further bearing options are magnetic bearings or plain bearings.

Various systems can be used as combustion chambers3in order to burn the fuels with low emissions according to their quality and composition. The relevant technologies include the so-called FLOX burners (“Flameless Oxidation”) and pore burners, which are mainly designed using metal oxide ceramic materials.

According to the invention, the gas turbine4and generator12are to be cooled by means of water; cooling by means of ethanol or a water-ethanol mixture is to be aimed at. Part of the cooling capacity is provided by the air volume exiting the air bearings in the direction of the shaft11and gas turbine4. If possible, the turbine shaft11should be hollow in order to achieve a high torsional rigidity of the gas turbine4; in addition, the hollow shaft can transport cooling media.

Furthermore, the extraction of bleed air after the compressor1or from an additional compressor for process control is possible. This additional compressor can be arranged on the turbine shaft.

Due to the combination of two circuits, the energy flows, mass flows and the disturbance variables must be controlled in such a way that the two circuits work synchronously and their performances add up. For this, the technical demands on materials, control, regulation and operationally safe design of the components under all conditions are enormous.

The ORC turbine requires very tight tolerances to avoid leakage of the working fluid and thus loss of power. Leakage at the expansion turbine6leads to significant malfunctions and failure of the turbine arrangement according to the turbine arrangement is likely.

In a particular embodiment of the present invention, as described above, the compressor1is designed to generate a negative pressure. Here, combustion and residual heat utilization are enabled according to the principle of the inverted Brayton cycle process.

This inverted Brayton cycle process is a modification of the Brayton (or Joule)—process in that here the compressor1draws combustion air “backwards” through the gas turbine4and an intermediate heat exchanger5,21. Thus, in the direction of flow of the working medium, the turbine is located upstream of the heat exchanger5,21and the compressor1. This arrangement can be derived from the turbine arrangement described in accordance with the invention by simple modification. Similarly, the efficiency in this process conversion can be increased by a mechanically directly coupled ORC process in accordance with the invention.

The turbine arrangement according to the invention has a sophisticated system of bearings and media guides that achieve efficient thermal decoupling of the gas turbine4and the expansion turbine6from one another. Suitable cooling media and cooling media routing in combination with a selection of materials that meet the thermal and mechanical requirements of the system ensure that the individual components support each other to a large extent during operation and that both overheating of one process and inefficient cooling of the other are ruled out.

The subsystems are designed with respect to each other to run in their optimum efficiency range or to work together to produce the optimum efficiency of the system.

According to the invention, the gas turbine4and the expansion turbine6are synchronized. In other words, it is essential that gas turbine4and expansion turbine6complement each other in their outputs, which is essentially done by designing at full load point such that the energy delivered in ORC heat exchanger21and the resulting mass flow, pressure and temperature of the working fluid extract just enough energy from the exhaust gas of the gas turbine process that this results in equal speeds in both turbines4,6.

LIST OF REFERENCE SIGNS

1compressor2recuperator21heat exchanger3combustion chamber31combustion air supply33combustion gas exhaust4gas turbine43exhaust gas discharge5heat exchanger (ORC evaporator—superheater)6expansion turbine (impulse turbine)61working medium feed (steam feed)63working medium discharge (steam return)7working medium condenser (capacitor)8condensate feed pump9working medium reservoir10working medium feed pump11common shaft12generator13coupling element