WO2018060376A1

WO2018060376A1 - Method and device for generating electric energy

Info

Publication number: WO2018060376A1
Application number: PCT/EP2017/074707
Authority: WO
Inventors: Jürgen PETERSEIM
Original assignee: Erk Eckrohrkessel Gmbh
Priority date: 2016-09-30
Filing date: 2017-09-28
Publication date: 2018-04-05
Also published as: DE102016118594A1

Abstract

The invention relates to a method and a device for generating electric energy, using the thermal energy of an exothermic process. Disclosed is a method for generating electric energy, using the thermal energy of an exothermic process. Waste heat (20) is generated in an exothermic process. At least part of the waste heat (20) is used to heat a high-temperature medium (32), in particular a salt melt and part of the waste heat (20) is stored in the high-temperature medium (32). A second medium (40) is evaporated using the waste heat (20) such that steam (41), more particularly saturated steam, is produced. Heat from the high-temperature medium (32) is fed to the steam (41), producing superheated steam (42). This is conducted via a turbine (52) in order to generate electric energy.

Description

Method and device for generating electrical energy

The invention relates to a method and a device for generating electrical energy using thermal energy of a heat-emitting process.

In many processes, waste heat is generated, whose energetic use is desirable. For example, many industrial processes provide large amounts of hot flue gases. In particular, in intermittent processes, for example in electric arc furnaces for steel production, an energetic use of thermal energy is often not available or not very efficient. Known solutions are often based on

Saturated steam storage to store energy. In the form of saturated steam, the thermal energy can be cached; then z. In

Saturated steam turbines convert into electrical energy. In this way, the power generation can be done even with an interruption of the waste heat.

Saturated steam storage systems are well established and easy to implement, but power generation has only a comparatively low efficiency.

The US 2010 0319 348 A1 teaches that heat from exhaust gases is used to a

To heat the heat transfer medium and to store the heat with it. The heat stored in the heat carrier can be supplied to a further fluid, which is passed through a turbine for generating electrical energy.

The invention is based on the object, a method and a device for

Generation of electrical energy to provide, with which the thermal energy in particular intermittently operated waste heat sources on efficient and

resource-conserving way can be used.

The object is achieved by the method for generating electrical energy according to claim 1 and by the device for generating electrical energy according to

Claim 6. Advantageous embodiments of the method are specified in claims 2-5; advantageous embodiments of the device are specified in the claims 7-10.

A first aspect of the invention is a method for generating electrical energy using thermal energy of a heat-emitting process. In this case, waste heat is generated in a heat-emitting process and at least part of the waste heat is used for heating a high-temperature medium, in particular a molten salt. As a result, part of the waste heat is stored in the high-temperature medium. A second medium is evaporated using the waste heat, so that steam, in particular saturated steam, is present. Heat from the high temperature medium is supplied to the steam, so that superheated steam is present, which is passed through a turbine to generate electrical energy.

In other words, waste heat from a process, which may be an industrial process, for example, generates steam from a liquid second medium and heats a high temperature medium in a heat exchanger. The second medium may be water, which is evaporated to saturated steam in an evaporator. The evaporator can be arranged in a waste gas containing flue gas stream. The second medium is thus evaporated, in particular under direct use of the waste heat from the heat-emitting process. The heating of the high-temperature medium can take place simultaneously with the evaporation. It will be a part of the waste heat for heating the

High temperature medium and another part used for evaporation of the second medium.

Alternatively, the evaporation of the second medium before overheating the steam can also be done by means of the high temperature medium. In this case, the waste heat is used indirectly for evaporation.

Heat from the high temperature medium is used to further heat the steam and generate superheated steam. This is done in a heat exchanger, which is referred to as the first steam superheater.

The heat-emitting process can be any process, in particular an industrial high-temperature process, which generates waste heat, for example an electric arc furnace in steelmaking. In addition, the method according to the invention can also be used in steam power plants, for example for the combustion of fuels such as coal. In this case, the waste heat is not a by-product of the process but a desired product. Waste heat refers to the heat of any process that is released to the environment.

A high temperature medium is a medium capable of being heated, in particular in liquid or solid form, to temperatures above 300 ° C, typically between 390 ° C and 850 ° C, and used for the temporary storage of thermal energy. In particular, molten salts can be used. Alternatively, for example, thermal oils, liquid metals or particulate substances are possible.

Advantage of the method according to the invention is that the generation of electrical energy from superheated steam can be done with a higher efficiency than from saturated steam and the method is thus more efficient than conventional methods for generating electrical energy. In one embodiment of the method, the steam generated by evaporation of the second medium, in particular the saturated steam, is stored.

In this embodiment, the steam is cached in a steam storage. It can be arranged a plurality of steam storage. In particular, it is stored in operation of the waste heat source saturated steam to, if necessary, for example, at a

Interruption of the waste heat supply, removed and overheated by the stored heat from the high temperature medium. Such an interruption is also referred to as the offline phase of the waste heat source.

This embodiment of the invention has the advantage that, although a direct storage of superheated steam is not possible, superheated steam can be used to generate energy even with interruptions of the waste heat. The used storage of saturated steam is an established and efficient process. Even with intermittent waste heat supply permanently high efficiency is possible in this way.

In a further embodiment of the method for generating electrical energy, a portion of the waste heat is used offset in time to generate superheated steam. This is passed to generate electrical energy via a turbine.

Thus, part of the waste heat is used in phases and in temporal offset to overheat the steam by means of the high-temperature medium to produce directly, ie without the use of high-temperature medium, superheated steam.

In the flue gas flow can be arranged to a heat exchanger, which also as

Superheater is called to overheat the steam using the waste heat. This superheater can be arranged in front of the evaporator, so that a higher temperature is available for overheating than for the evaporation.

If the steam generated by evaporation of the second medium, ie the saturated steam, is stored in a steam storage, this too can be overheated directly by means of the heat exchanger by the heat contained in the flue gas.

It can therefore take place when operating the waste heat-providing process, the superheating of the steam with a higher efficiency. This results in the advantage of flexible and efficient power generation, since depending on the availability of the waste heat source alternately superheated steam that was generated directly from the use of waste heat, and / or superheated steam generated by heat from the high temperature medium in the first steam superheater, to generate electricity can be used.

Alternatively, through the direct use of the waste heat only saturated steam can be generated and the steam overheating constantly heated by the parallel

High temperature medium, regardless of the availability of the waste heat source. In one embodiment, the heated high-temperature medium is temporarily stored in particular in a memory.

The storage ensures that heated high-temperature medium is also available at times when no waste heat from the process is provided. In particular, it is filled with the heated high-temperature medium in online phases of the waste heat source, that is, if there is waste heat. Several memories can be arranged. Thus, the stored vapor in offline phases can still be overheated by the existing heat of the stored high temperature medium.

It can be arranged a second memory for temporarily storing the cold high-temperature medium. Thus, a circulation of the high-temperature medium is possible, in which the flow of the high-temperature medium, for example by means of at least one pump, can be controlled. During the interruption of the waste heat supply existing hot high-temperature medium from the first memory can be used to overheat the steam and stored in the cold state in the second memory. Also in the area of the second memory several memories can be arranged.

The advantage of this embodiment is that even with intermittent waste heat with possibly longer interruptions of the waste heat supply continuously by means of superheated steam, so with high efficiency, electrical energy can be provided. Even with batch operation of the waste heat emitting process, a continuous operation of the energy generating plant can be carried out. This is

Gentle on materials as cooling and warm-up times and thus stresses and strains in the material are prevented or reduced. In the water-steam cycle or Rankine cycle thus an increase in the efficiency of power generation to 25% -40% is possible.

Furthermore, saturated steam and heated high-temperature medium can be generated during operation of the waste heat source by means of waste heat, which are each stored proportionally in the respective storage or used to overheat the saturated steam by means of the heated high-temperature medium. If the waste heat source is not available, stored saturated steam as described can be overheated with stored high temperature medium.

The advantage of this embodiment is that only a steam superheater is needed to produce the superheated steam. The steam superheater is used in online and offline phases of the waste heat source. Again, this can be permanent with a high

Efficiency electrical energy can be provided.

In a further embodiment, the second medium is preheated prior to evaporation. This means in particular the preheating by another part of the waste heat in a separate process stage, such as in an economizer. This is typically arranged in the flue gas stream behind the evaporator for evaporating the second medium and adapted to at least partially transfer the remaining residual heat of the flue gas to the second medium.

However, it is not excluded that the second medium is preheated in other ways, for example by using electrical energy.

The advantage of this embodiment is that the efficiency of energy production is further increased and a larger proportion of the waste heat can be used.

A second aspect of the invention is a device for generating electrical energy using thermal energy of a heat-emitting process. This includes a heat exchanger for transmitting waste heat of the heat-emitting process to a high-temperature medium for heating the high-temperature medium and an evaporator for evaporating a second medium by means of waste heat of the heat-emitting plant for the purpose of generating steam. Furthermore, the device comprises a first steam superheater for superheating the steam by means of the heated

High temperature medium and a driven with the superheated steam turbine.

The heat-emitting process, whose heat is used in the power generation by the device according to the invention, as described can be any process, but in particular an industrial process, such. B. a blast furnace process or a power plant process. As a high temperature medium, as described, for. Legs

Molten salt are used.

The evaporator is in particular a heat exchanger for transmitting heat of a flue gas to the second medium. The first steam superheater is a heat exchanger configured to transfer heat from the high temperature medium to the generated steam.

With the device according to the invention, in particular the method according to the invention for generating electrical energy can be carried out. The heat exchanger for transferring waste heat to a high-temperature medium and the evaporator are typically arranged in the flue gas stream of the heat-emitting process. In particular, the heat exchanger is arranged in front of the evaporator, so that a higher temperature for heating the high-temperature medium is available than for the evaporation of the second medium.

In particular, the second medium is water which circulates in a water-steam cycle. This cycle can be next to the evaporator and the second steam superheater the turbine, a condenser, a pump and a control device, for example with an electronic control unit, as well as suitable sensors, fittings, instruments, displays, input and output devices and devices for power supply.

The advantage of the device according to the invention is that it is an efficient and

resource-saving energy generation.

In one embodiment of the device for generating electrical energy, a second steam superheater is arranged in the flue gas stream of the waste heat generating process.

The second steam superheater is designed in particular to waste heat from the

Transfer flue gas to the steam and thus overheat the steam. As a result, superheated steam can be provided in a simple and efficient manner when operating the waste heat source. As described, such a phased intermittent operation can take place: In online phases of the waste heat source, the steam in the second

Steam superheater overheated by the hot flue gas. In offline phases or in case of interruptions, this is done in the first steam superheater by means of the

High temperature medium stored thermal energy. This is particularly advantageous in connection with an arrangement of a steam accumulator for storing the generated steam, ie the saturated steam. In this can be cached during operation of the waste heat source of saturated steam in order to make it at a

Interruption of the operation of the waste heat source to be removed for overheating. In particular, the device according to the invention comprises such a steam accumulator.

In a further embodiment, the device for generating electrical energy comprises a circuit for arranging the high-temperature medium, the circuit comprising the heat exchanger for transmitting waste heat to the high-temperature medium, a first memory for storing the heated high-temperature medium, the first steam superheater, and a second memory for storage of

High temperature medium includes.

The second reservoir is in particular adapted to receive the high-temperature medium after it has been converted by heat transfer to the vapor in the first

Steam superheater has a lower temperature. In particular, the circuit further comprises at least one pump for circulating the high-temperature medium. It can also be a control device, for example with an electronic

Control unit, as well as suitable sensors, fittings, instruments, displays, input and output devices and / or facilities for power supply have.

The memory for the high-temperature medium and the steam storage are designed in particular such that during the duration of the expected interruptions of Abwärmezufuhr, even at successive interruptions, stored saturated steam can be overheated by means of the stored high-temperature medium and the efficient generation of electrical energy by means of superheated steam is not interrupted.

The first memory and the second memory may be arranged in a common unit, such as in a layer memory. In this case, a partial volume of the structural unit is used as storage for the heated high-temperature medium and another partial volume for the high-temperature medium at a lower temperature. The partial volumes are in particular spatially separated.

The circuit according to the invention for the arrangement of the high-temperature medium enables an efficient and easily controllable generation of electrical energy. The

High temperature medium can be permanently circulated without loss. Even with longer interruptions of the waste heat can be stored by the hot

High-temperature medium superheated steam can be generated.

It may be a heating surface, in particular a heating surface of a boiler system, designed to transfer waste heat to the high-temperature medium.

In this embodiment, a heating surface of a boiler plant for the transmission of

Waste heat designed on the high-temperature medium. A heating surface can be realized for example by a fin wall or membrane wall. This is a wall composed of pipes, for example risers, which is designed to transfer heat to a medium for the purpose of evaporating the medium and typically delimits a combustion chamber or flame chamber of a boiler installation. For a compact and low-loss design of the heat exchanger is possible.

In one embodiment of the device for generating electrical energy, this comprises an economizer for preheating the second medium using waste heat of the heat-emitting process.

This is, as described, designed to preheat the second medium before evaporation and is in particular in the flue gas stream behind the evaporator for

Evaporation of the second medium arranged. For an even better utilization of the waste heat and thus a further increased efficiency is possible.

The invention will be explained below with reference to the embodiment shown in the accompanying drawings.

Show it

Fig. 1: a flow diagram of a known from the prior art device for generating electrical energy, and 2 shows a flow chart of a device according to the invention for generating electrical energy.

1 shows a known from the prior art device for generating electrical energy 10. In a flue gas stream 22 of a waste heat 20-generating process are an economizer 50, ie a heat exchanger for the transmission of

Waste heat 20 on a medium 40, namely water, and an evaporator 46 for

Vaporization of preheated water arranged. The evaporator 46 has a

Steam drum 44, in which the generated steam 41, for example, collects under a pressure of 28 bar. Following, along the flow direction 24 of the

Viewed flue gas, there are a device for gas cleaning 54 and a chimney 56. The generated steam 41, which is in particular saturated steam is passed to generate electrical energy via a turbine 52 which is coupled to a generator 58. In this case, the steam has, for example, a temperature of 230 ° C. In the water-steam cycle, there is furthermore a condenser 59 and a pump 60.

A steam accumulator 43 is disposed behind the evaporator 46 and allows the

Caching saturated steam. In this way, further electrical energy can be generated with the illustrated device 10 even with an interruption of the waste heat supply by steam 41 is passed from the steam reservoir 43 via the turbine. The efficiency of the generation of electrical energy is due to the use of

Saturated steam with 15-20% comparatively low.

FIG. 2 shows a flow chart of a device according to the invention for generating electrical energy 10 using thermal energy of a heat-emitting process. This device has a much higher efficiency of about 25-40%, since superheated steam 42 having a temperature of z. B. 450 ° C is used to generate electricity.

In the steam drum 44 of the evaporator 46, there is a pressure of z. B. 60 bar. Between the evaporator 46 and the waste heat 20 generating process is located in the exhaust stream, a second steam superheater 48. In this, the saturated steam 41 can be overheated using the waste heat 20. The superheated steam 42 thus produced is passed through a turbine 52 as described in FIG.

At the point located in the flue gas stream 22 with the highest temperature, between the second steam superheater 48 and the waste heat 20 generating process, there is a heat exchanger 34 for transmitting waste heat 20 of the heat-emitting process to a high-temperature medium 32, here a molten salt. This is in a first memory 37 in a hot state, for example at a temperature> 500 ° C, cached to continue to overheat steam 41 in case of interruption of the waste heat supply can. This happens in the first steam superheater 36, the one

Heat exchanger for transferring heat of the high-temperature medium 32 to the saturated steam 41 is. For this purpose, the saturated steam 41 can be removed from the steam reservoir 43.

The cooled high-temperature medium 32 is in a second memory 38th

for example, stored at a temperature> 240 ° C, before it is heated again in the heat exchanger. The circuit 30 of the high temperature medium 32 is controlled by two pumps 62, 64.

In the circuit of the second medium 40, here the water-steam cycle, are located downstream of the turbine 52, a capacitor 59 and a pump 60. The first

Steam superheater 36 represents the link between the water-steam cycle and the circuit 30 of the high-temperature medium.

In one embodiment, the second steam superheater 48 is absent and the overheating is carried out regularly in the first steam superheater 36 and by the heated high temperature medium 32. In this embodiment, a bypass of the steam accumulator 43 can be arranged to directly feed the first in online phases of the waste heat source Steam superheater 36 with the steam 41, in particular the saturated steam, allows. A bypass of the first memory 37 through the high-temperature medium 32 is conceivable in this case. Furthermore, in the on-line phases of the waste heat source, the first storage 37 and the steam storage 43 can be charged simultaneously.

LIST OF REFERENCE NUMBERS

Device for generating electrical energy 10

Waste heat 20

Flue gas flow 22

Flow of the flue gas 24

Circulation 30

High temperature medium 32

Heat exchanger 34 first steam superheater 36 first memory 37 second memory 38 second medium 40th

Steam 41 superheated steam 42

Steam storage 43

Steam drum 44

Evaporator 46 second steam superheater 48

Economizer 50

Turbine 52

Gas cleaning 54

Fireplace 56

Generator 58

Capacitor 59

Pump for the water cycle 60

First pump 62

Second pump 64

Claims

claims

1 . Method for generating electrical energy using thermal energy of a heat-emitting process, in which

- Waste heat (20) is generated in a heat-emitting process,

- At least a portion of the waste heat (20) for heating a

High temperature medium (32), in particular a molten salt, is used and consequently a part of the waste heat (20) in the high-temperature medium (32) is stored,

a second medium (40) is evaporated using the waste heat (20), so that steam (41), in particular saturated steam, is present,

Heat is supplied from the high-temperature medium (32) to the steam (41), so that superheated steam (42) is present,

- The superheated steam (42) for generating electrical energy via a turbine (52) is passed.

2. A method for generating electrical energy according to claim 1, wherein the vapor generated by evaporation of the second medium (40) (41), in particular the saturated steam, is stored.

3. A method for generating electrical energy according to at least one of claims 1 and 2, wherein temporally offset part of the waste heat (20) is used to produce superheated steam (42) and the superheated steam (42) for generating electrical energy over a Turbine (52) is passed.

4. A method for generating electrical energy according to at least one of claims 1 to 3, wherein the heated high-temperature medium (32) is temporarily stored.

5. A method for generating electrical energy according to at least one of claims 1 to 4, wherein the second medium (40) is preheated prior to evaporation.

6. means for generating electrical energy (10) using thermal energy of a heat-emitting process, comprising a heat exchanger (34) for transmitting waste heat (20) of the heat-emitting process to a high-temperature medium (32) for heating the high-temperature medium (32),

- an evaporator (46) for evaporating a second medium (40) by means of waste heat (20) of the heat-emitting process for the purpose of generating steam,

- A first steam superheater (36) for superheating the steam (41) by means of the heated high-temperature medium (32), and

- A turbine with the superheated steam (42) drivable turbine (52).

7. A device for generating electrical energy (10) according to claim 6, wherein a second steam superheater (48) for overheating of steam (41) in the flue gas stream (22) of the heat-emitting process is arranged.

8. Device for generating electrical energy (10) according to at least one of claims 6 and 7, comprising a circuit (30) for arranging the

High-temperature medium (32), the circulation

- The heat exchanger (34) for the transmission of waste heat (20) on the

High temperature medium (32),

- A first memory (37) for storing the heated

High temperature medium (32),

- the first steam superheater (36), as well

- A second memory (38) for storing the high-temperature medium (32)

includes.

9. Device for generating electrical energy (10) according to at least one of claims 6 to 8, wherein a heating surface, in particular a boiler system, for transmitting waste heat (20) to the high-temperature medium (32) is configured.

10. A device for generating electrical energy (10) according to at least one of claims 6 to 9, comprising an economiser (50) for preheating the second medium (40) using waste heat (20) of the heat-emitting process.