EP2659099B1 - Power generation device - Google Patents

Description

The invention relates to a device for generating electrical or mechanical energy with a combustion device for a solid, gaseous or liquid medium, in particular biomass, which generates during combustion flue gas containing heat, and with an RC system, which is a circuit for a Having working means, which is guided for the absorption of heat by acting as a working medium evaporator heat exchanger.

Such a device for power generation is both in the German utility model application DE 20 2011 001 111.9 with the utility model DE 20 2011 001 111 U1 as well as in the German utility model application DE 20 2010 017 143.1 with the utility model DE 20 2010 017 143 U1 to which reference is hereby made and the disclosures of which are fully incorporated into the description of this invention. Furthermore, the document also shows EP 1 221 573 a combustion device with ORC system.

A combustion device according to the invention is a system in which by the supply of air, a solid, liquid or gaseous medium is oxidized as fuel and thereby exhaust gases in the form of gaseous combustion products. Due to the chemical energy stored in the fuel, heat is released in the oxidation of the fuel. The resulting during combustion gaseous combustion products are referred to herein as flue gas. The temperature of this flue gas can be up to 1000 ° C or even higher.

An RC system (RC = Rankine Cycle) is understood to mean a system in which a thermodynamic cycle using a circulating working medium, for. As water or water vapor, heat is converted into mechanical or electrical energy.

An ORC system (ORC = Organic Rankine Cycle) is an RC system that uses a thermodynamic cycle of heat to generate mechanical or electrical energy. In an ORC system, there is a working fluid circuit that is similar to a steam cycle. As a working medium of the working fluid circuit here, however, does not contain water vapor, but usually organic media, eg. As butane, toluene, silicone oil or ammonia, which have a low evaporation temperature in relation to water. The working fluid in an ORC system is usually pressurized by a pump. The pressurized working fluid is then heated in an evaporator. The working fluid is evaporated and optionally overheated. The vaporized or superheated working fluid then passes to a steam turbine. Here, the working fluid is expanded to generate mechanical energy to a lower pressure and then condensed. In the cycle, the working fluid is then returned to the evaporator, where it is reheated and re-evaporated or overheated. It should be noted that in an ORC system as a working medium and media can be used, the evaporation temperature is higher than that of water. ORC systems can be advantageously used for generating electrical or mechanical energy from heat, especially when the available temperature gradient between a heat source and a heat sink is too low to operate a heat engine, such as a turbine, with water vapor.

ORC plants are not only operated with heat from incinerators. The heat required for operating an ORC plant can also be obtained geothermally or come from solar power plants. In addition, ORC systems can also be operated with the waste heat of internal combustion engines (eg reciprocating engines).

In devices for generating energy, which contain a combustion device and in which there is an ORC system, the heat generated in the combustion device is conventionally transferred from the combustion device to the ORC system using intermediate heat carriers.

Here sometimes there is the problem that the temperature of the flue gases used is so high that the work equipment used in ORC systems can be damaged due to excessive thermal load when it comes with the flue gases in a common heat exchanger.

Intermediate heat carriers in the form of thermal oil for heat transfer are widely used in industrial plants. In closed circuits with heat exchangers for heat transfer they are used for both heating and cooling. The viscosity, the solidification and boiling points as well as the flammability of the relevant thermal oil are generally adapted here to a temperature range in which the heat is to be transferred.

In order to operate an RC system with the heat from a combustion device, it is known to heat thermal oil used as an intermediate heat transfer medium to about 300 ° C. However, to ensure that the chemical structure of the thermal oil is not destroyed at this temperature, it must be continuously pumped through heat exchangers in a piping system. However, this causes a significant energy consumption and reduces the efficiency of the system.

The object of the invention is to provide a device for generating electrical or mechanical energy with an RC system that receives heat from a combustion device and that can be reliably operated with high efficiency.

This object is achieved by a device of the type mentioned, in which the heat exchanger is connected to the combustion device via a flue gas line to transmit the heat of the flue gas generated during combustion to the working fluid of the RC system.

This makes it possible, in particular, to reduce the energy required for the circulation of thermal oil and possibly to dispense with a separate intermediate circuit.

By supplying the heat exchanger with flue gas that is at least partially mixed with flue gas that has already been cooled by the heat exchanger, excessive thermal loading of the heat exchanger and working fluid in the RC system can be avoided.

It is advantageous if the temperature level of the guided through the heat exchanger flue gas is lowered and if a part of the thus cooled flue gas can be returned via a further flue gas line in front of the heat exchanger in the flue gas line. As a result, the flue gas generated during combustion can be mixed with already cooled flue gas and set a lower temperature level in the heat exchanger. The temperature level in the heat exchanger is preferably adjusted by changing the amount of recirculated exhaust gas. According to the invention can be selected as the temperature of the cooled exhaust gas, a temperature of 150 ° C to 300 ° C.

In order to generate electrical or mechanical energy, flue gas is generated by burning a solid, gaseous or liquid medium, in particular by burning biomass, which contains heat. The heat of the flue gas is fed to a heat exchanger acting as working medium evaporator in an RC system. According to the invention, the generated flue gas is passed through the heat exchanger for this purpose.

The guided through the heat exchanger flue gas can be sucked with a flue gas blower and fed through the other flue gas line in the flue gas line. It is particularly advantageous if a circulation blower is arranged in the further flue gas line, which sucks the flue gas passed through the heat exchanger and conveys it into the further flue gas line.

The RC system includes a working as a working fluid condenser heat exchanger, which is connected to a cooling water circuit to dissipate via the cooling water circuit, the heat of condensation of the working fluid. The cooling water circuit is also guided by a further heat exchanger which extracts heat from the flue gas passed through the heat exchanger. Thus, the temperature of cooled flue gas, which is returned by the further Rausgasleitung in the flue gas duct, can be cooled even further.

In particular, the RC system may include a feed pump that moves the working fluid from the heat exchanger operating as a working fluid condenser to the heat exchanger. With the feed pump, the working fluid can be conveyed through a recuperator arranged in the circuit for the working fluid upstream of the heat exchanger.

An idea of the invention is in particular to adjust the temperature of the flue gas stream upstream of acting as evaporator for working heat exchanger by changing the mass flow of the cooled flue gas by throttling by a flue gas flap in the further flue gas line, which at least partially returns the flue gas to the heat exchanger. An idea of the invention is also the temperature of the flue gas stream before the working medium heat exchanger by changing the speed of a fan arranged in the further flue gas line over which the flue gas is at least partially returned to the heat exchanger.

In the apparatus for generating electrical or mechanical energy, a bypass line is provided, can be fed via the guided through the heat exchanger flue gas in the further flue gas line or via which it is possible to lead flue gas from the further flue gas duct to the other heat exchanger. The device may include a arranged in the flue gas line flue gas flap, with which the flow of flue gas can be prevented from the heat exchanger to the other heat exchanger or in the bypass line. Also in the flue gas line between the combustion device and the heat exchanger, a flue gas flap may be provided. In order to control the flow of flue gas in the flue gas duct with it, it is convenient to provide a conduit with a flap for supplying fresh air into the heat exchanger. In this way it can be ensured that the heat exchanger and fresh air can be cooled. The device is advantageously formed with a chimney for releasing cooled flue gas.

The RC system in the device according to the invention can be designed both as a small or large home plant, as a large industrial plant or as a power plant for municipalities. A home installation is understood to mean a system with which the energy supply including the air conditioning of office buildings, garages, and hospitals can be guaranteed. As an industrial plant, a plant is referred to the industrial manufacturing equipment, especially manufacturing equipment of the automotive industry, z. B. Lackieranlagen supplied with electrical energy for which not only electricity but also heat at different temperature levels must be provided. The device according to the invention has a simple apparatus design. The corresponding investment costs are therefore low. A device according to the invention can Therefore, work with low operating costs. A device according to the invention is particularly suitable for operation in low power ranges for energy and heat.

Advantageous embodiments of the invention are illustrated in the drawings and will be described below.

Fig. 1

eine erste Vorrichtung zum Erzeugen von Energie mit einer ORC-Anlage;

Fig. 2

eine zweite Vorrichtung zum Erzeugen von Energie mit einer ORC-Anlage und einem Zirkulationsgebläse; und

Fig. 3

eine dritte Vorrichtung zum Erzeugen von Energie mit einer ORC-Anlage und einem Wärmetauscher für das Aufheizen des Arbeitsmittels der ORC-Anlage mit bereits abgekühltem Rauchgas.

Show it:

Fig. 1

a first device for generating energy with an ORC system;

Fig. 2

a second device for generating energy with an ORC system and a circulation fan; and

Fig. 3

a third device for generating energy with an ORC system and a heat exchanger for heating the working fluid of the ORC system with already cooled flue gas.

The in the Fig. 1 shown apparatus 10 for generating electrical or mechanical energy has a combustion device 1 for organic substances, in particular biomass, z. As wood, wood chips or other dried plant remains such as straw or grasses. The wood used in the device can be derived directly from its growth location, ie a forest or a plantation. In principle, it can also come from a waste wood or recycling wood recycling. Other verwenbare organic substances may in particular be liquid. It may be z. For example, oils and distilled substances obtained from plants. Other useful organic substances may also be gaseous and z. B. have the form of combustible gases resulting from the decomposition of plants, food waste and garbage, in particular of household waste or manure in animal husbandry.

When burning biomass, the combustion device 1 generates flue gas containing heat. In the device 10, there is an ORC system 2. The ORC system 2 has a circuit 5 for a fluid working medium, which is guided for the absorption of heat by acting as a working medium evaporator heat exchanger 21. Butane, toluene or silicone oil are preferably used as the working medium.

The heat exchanger 21 is connected to the combustion device 1 via a flue gas line 33, 34 in order to transfer the heat of the flue gas generated during combustion to the working medium of the ORC system 2.

The ORC system 2 includes a turbine 27 coupled thereto generator 25. The ORC system 2 has a recuperator 23 and a working fluid condenser 24. In the OCR system 2 there is a acting as a working fluid pump feed pump 22. With the feed pump 22 is the fluid working fluid in the liquid state of aggregation brought to operating pressure. The liquid working medium flows through the heat exchanger 21. Here, the heat is transferred from the flue gas of the combustion device 1 to the working fluid. The working fluid evaporates. At the output of the heat exchanger 21 saturated steam or dry steam is then provided. By the energy input in the heat exchanger 21 thereby increase the specific volume and the temperature of the vapor. In the turbine 27, the pressurized vaporous working fluid is released almost isentropically to a lower pressure. Due to the expansion in the turbine 27, the specific volume of the working fluid thereby increases. The increase in volume of the working fluid caused by the pressure drop across the turbine 27 results in a volume change work that is converted into mechanical energy in the turbine 27 by means of the blades. To the turbine 27, a generator 25 is connected. With the generator 25, electrical energy is fed into a power grid 28.

In the recuperator 23, heat is withdrawn from the vaporous working medium stream leaving the turbine 27. For this purpose, with the feed pump 22 pressurized liquid working fluid is passed through the recuperator. In the recuperator 23 then decreases the temperature of the vaporous working fluid from the turbine 27 to the condensation temperature. Following the recuperator 23, the working fluid in the circuit 5 is moved by a downstream, acting as a working fluid condenser heat exchanger 24.

The acting as working fluid condenser heat exchanger 24 is connected to a cooling water circuit 4. The cooling water circuit 4 includes a feed pump 42. In the cooling water circuit 4, there is a heat exchanger 41, through which the flue gas is guided from the line 34. About the cooling water circuit 4, the heat released in the condensation in the heat exchanger 24 heat is fed into a not-shown heat network.

In the acting as a working fluid condenser heat exchanger 24, the working fluid is condensed. It goes completely into the liquid state of aggregation. With the working as a pump pump feed pump 22, the condensed working fluid is then brought back to operating pressure. In the circuit 5, it is then returned to the heat exchanger 21 acting as an evaporator. The cycle for the working fluid in the ORC system 2 is thus closed.

The heat output of the combustion device 1 is varied by changing the fuel and air supply. The combustion device 1 can be controlled or regulated according to the power required by the generator 25 supplied power network or the heat demand of the fed with the cooling water circuit 4 heat network.

In the device 10, a further flue gas line 35 is formed. The further flue gas line 35 is connected with respect to the combustion device 1 before acting as a working medium evaporator 21 heat exchanger of the ORC system and behind the heat exchanger 41 to the flue gas line 34. Via the further flue gas line 35, it is possible to at least partially recirculate the flue gas guided through the heat exchanger 21 into the flue-gas line 34. This serves to mix the flue gas generated during combustion in the combustion device 1 with flue gas, which has already been passed through the heat exchanger 21. This flue gas is therefore cooled relative to the temperature level of the exiting the combustion device exhaust gas. By returning cooled flue gas, the temperature of the flue gas can be lowered, which is moved in the flue gas line 34 to the heat exchanger 21. In a modified embodiment, as an alternative or in addition to cooled flue gas ambient air is introduced at a temperature of less than 50 ° C before the heat exchanger 21 in the flue gas duct 34.

In the device 10 there is a line 9 with a controllable flap 63 through which fresh air can be supplied into the flue-gas line 34 between the heat exchanger 21 acting as working-medium evaporator and the heat exchanger 41. On the outlet side of the heat exchanger 41 is located in the flue gas duct 34, a flue gas fan 32. By means of the flue gas blower 32, the flue gas is conveyed in the flue gas duct 34 to a chimney 31. Through the chimney 31, the flue gas generated in the device 10 is possibly discharged to further emission control systems and then into the environment.

Typical temperatures of the flue gas provided by the combustor 1 in the flue gas duct 33 are in a range of 900 ° C to 1000 ° C. After admixture of cooled flue gas, which in front of the chimney 31 have a temperature of about 160 ° C to 180 ° C. can, an inlet temperature for the flue gas 34 can be achieved in acting as a working medium evaporator heat exchanger 21, which according to the invention can be 300 ° C to 600 ° C, which is in particular in a range of 550 ° C. This ensures that the working fluid in the ORC system 2 can be brought to a favorable working temperature and the heat exchanger acting as an evaporator 21 as well as the working fluid is not thermally stressed excessively.

In the device 10, the guided through the heat exchanger 21 flue gas is sucked with a flue gas fan 32 and conveyed by a direction corresponding to the arrows 51 flow direction to the chimney 31. As a result, a pressure drop occurs at the heat exchanger 21. The pressure of the flue gas at the outlet side of the flue gas blower 32 is greater than at the inlet side of the heat exchanger 21. This circumstance causes flue gas to flow via the further flue gas line 35 with a flow direction corresponding to the arrows 53, which has already been cooled in the heat exchangers 21, 41 , This flue gas is fed through the further flue gas line 35 in the flue gas duct 34 before the heat exchanger 21 again.

In the device 10 there is a bypass line 7, which connects the flue gas line 34 with the Raugasleitung 35. Via the bypass line 7, flue gas guided through the heat exchanger can be fed into the further flue gas line 35 or guided via the flue gas from the further flue-gas line 35 to the further heat exchanger 41. In the bypass line 7, an adjustable flue gas flap 62 is arranged. By opening and closing the flue gas flap 63, the bypass line 7 can be released and locked.

Behind the heat exchanger 21 and after the connection point for the line, the flue gas line 34 includes a flue damper 61. With the flue damper 61, the flow of flue gas from the combustion device 1 set by the flue gas line 34 from the heat exchanger 21 to the other heat exchanger 41 or in the bypass line 7 and possibly also be prevented. In the further flue gas line 34 is located between the combustion device 1 and the heat exchanger 21, a further flue gas flap 64. With the flue gas flap 64, the flue gas flow through the flue gas line 35 can be adjusted.

In the devices 10, it is possible to control the temperature of the flue gas stream 34 before entering the heat exchanger 21 by adjusting the mass flow of the cold flue gas in the further flue gas duct 35 by varying the open position, ie. H. is reduced or increased by throttling the flue gas flap 64. For the temperature of the flue gas stream in the flue gas duct 34, a process-optimal value can thus be set before the heat exchanger 21.

In order to interrupt the flue gas flow 34 through the ORC heat exchanger 21 in the event of a malfunction or during commissioning or shutdown of the system, the flue gas flap 61 is closed in the devices 10, 20 and 30, respectively. By the bypass line 7 is released by opening the flue gas flap 62, the flue gas fan 32 then causes the arrows 52 corresponding Rausgasströmung to the chimney 31. If additionally also the flap 63 is opened in the line 9 for the supply of fresh air, while the acting as working medium evaporator heat exchanger 21 are cooled in a respect to the normal operation flowing cold flue gas or with ambient air. It should be noted that the flaps 61, 62, 63, 64 in a valve can also be functionally combined.

The in the Fig. 2 The device 20 shown corresponds in its construction to the structure of the device 10 Fig. 1 , Corresponding elements of the figures are therefore provided here with identical reference numerals. The corresponding description can be referenced accordingly. In the device 20 is arranged in the further flue gas line 35 a recirculation fan acting circulation blower 36. By means of the circulation blower 36, flue gas guided through the heat exchanger 21 is drawn in and conveyed into the further flue gas line 35.

In the device 20, it is possible to adjust or regulate a temperature of the flue gas stream 34 before acting as a working medium evaporator heat exchanger 21 of the ORC system 2 by the mass flow of the cold flue gas in the further flue gas duct 35 by varying the speed of the circulation blower 36 and is changed by adjusting the arranged in the flue gas line 34 in front of the heat exchanger 31 flue gas flap 61 '. This also makes it possible to achieve a process-optimal inlet temperature for the flue gas in the flue gas line 34 when entering the heat exchanger 21.

The in the Fig. 3 shown device 30 corresponds in its structure to the structure of the device 10 from Fig. 1 , Corresponding elements of the figures are therefore provided here with identical reference numerals. The corresponding description can be referenced accordingly. In the device 30, the ORC system 2 is formed with a further heat exchanger 26 through which a part of the working means is guided in order to heat this also with already cooled by the heat exchanger 21 flue gas.

It should be noted that in the case of the Fig. 1 to Fig. 3 an increase in the efficiency for converting the heat of flue gas generated by the combustion device 1 into electrical or mechanical energy can be achieved by optionally further heat exchangers are arranged in the circuit for the working fluid are located after the feed pump 22 of the ORC system 2, and extract the heat from the flue gas in the flue gas duct 34.

The heat exchanger 41 of the water circuit 4 of the devices 10, 20 and 30 is always traversed by flue gas both during operation and in the event of a fault. In a modified embodiment, however, it may be provided to bypass the heat exchanger 41 in case of failure via a bypass and then direct the hot flue gases directly into downstream emission control systems and subsequently through the chimney 21.

In summary, the following preferred features in particular should be noted: The invention relates to the conversion of thermal energy into electrical or mechanical energy with all features of the independent claims. For this purpose, flue gas is generated with a combustion device 1 for a solid, gaseous or liquid medium, in particular biomass, which contains heat. This heat is supplied by a working as a working medium evaporator heat exchanger 21 of an RC system 2, which contains a circuit 5 for a working fluid. According to the invention, the heat of the flue gas generated during the combustion is transferred to the working fluid of the RC system 2, by passing the flue gas through the heat exchanger 21.

LIST OF REFERENCE NUMBERS

1

incinerator

2

ORC system

4

Cooling water circuit

5

circulation

7

bypass line

9

management

10, 20, 30

Device for generating energy

21, 24, 26

heat exchangers

22

feed pump

23

recuperator

27

turbine

25

generator

28

power grid

31

fireplace

32

Flue gas fan

33, 34, 35

Flue gas line

34

Flue gas stream

36

circulating fan

41

heat exchangers

42

feed pump

51, 52, 53

arrow

61, 61 ', 62, 63, 64

flap

Claims (13)

1. Apparatus (10, 20, 30) for the generation of electrical or mechanical power,
   having a combustion device (1) for a solid, gaseous or liquid medium, in particular biomass which, during combustion, generates flue gas which contains heat,
   having an RC system (2) which has a circuit (5) for a working medium which, in order to absorb heat, is guided through a first heat exchanger (21) which acts as a working-medium evaporator, and
   is connected to the combustion device (1) via a flue gas line (33, 34), in order to transfer the heat of the flue gas which is generated during the combustion to the working medium of the RC system (2), and which RC system (2) has a second heat exchanger (24) which acts as a working medium condenser and is connected to a cooling water circuit (4), in order to dissipate the condensation heat of the working medium via the cooling water circuit (4), and
   having a further flue gas line (35), via which at least part of the flue gas which is guided through the first heat exchanger (21) and is therefore cooled can be recirculated into the flue gas line (34), in order to mix the flue gas which is generated during the combustion with cooled flue gas,
   characterized in that
   the cooling water circuit (4) is guided through a further heat exchanger (41) which is arranged in the flue gas line (34) and removes heat from the flue gas which is guided through the further heat exchanger (41),
   a bypass line (7) being provided, via which flue gas which is guided through the first heat exchanger (21) can be fed into the further flue gas line (35), or via which flue gas can be guided out of the further flue gas line (35) to the further heat exchanger (41).
2. Apparatus according to Claim 1, characterized in that the flue gas which is guided through the first heat exchanger (21) is sucked in by way of a flue gas fan (32) and can be fed into the flue gas line (34) through the further flue gas line (35).
3. Apparatus according to Claim 1 or 2, characterized in that a circulation fan (36) is arranged in the further flue gas line (35), which circulation fan (36) sucks in flue gas, which is guided through the first heat exchanger (21), and conveys it into the further flue gas line (35).
4. Apparatus according to one of Claims 1 to 3, characterized in that the RC system comprises a feed pump (22) which moves the working medium from the heat exchanger (24) which acts as a working medium condenser to the first heat exchanger (21).
5. Apparatus according to Claim 4, characterized in that the feed pump (22) moves the working medium through a recuperator (23) which is arranged in the circuit for the working medium upstream of the first heat exchanger (21).
6. Apparatus according to one of Claims 1 to 5, characterized by a flue gas valve (61), by way of which the flow of flue gas from the heat exchanger (21) to the further heat exchanger (41) or into the bypass line (7) can be suppressed.
7. Apparatus according to one of Claims 1 to 6, characterized in that a flue gas valve (61) is arranged in the flue gas line (34) between the combustion device (1) and the first heat exchanger (21).
8. Apparatus according to one of Claims 1 to 7, characterized by a line (9) with a valve (63) for feeding fresh air into the heat exchanger (21).
9. Apparatus according to one of Claims 1 to 8, characterized by a chimney (31) for releasing cooled flue gas.
10. Apparatus according to one of Claims 1 to 9, characterized in that the RC system is an ORC system.
11. Method for the generation of electrical or mechanical power by way of an apparatus according to one of Claims 1 to 9, characterized in that flue gas which contains heat is generated by way of combustion of a solid, gaseous or liquid medium, in particular of biomass.
12. Method according to Claim 11, characterized in that, during commissioning or running down or a disruption of the RC system (2), the flue gas is guided from the combustion device (1) through the further flue gas line (35) past the first heat exchanger (21) through the bypass line (7).
13. Method according to Claim 11, characterized in that flue gas is fed to the first heat exchanger (21), which flue gas is mixed at least partially with flue gas which has already been cooled by way of the heat exchanger (21).

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