WASTE HEAT USE

Abstract

It is proposed, in an industrial process to use the waste heat from electric converters and electric machines for the heating in a further process step. For this purpose, liquid cooling is used for the elements producing the waste heat. By this, electric or fossil-stored energy is saved, this leading in turn to a direct or indirect reduction in emitted greenhouse gasses.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Application of International Application No. PCT/EP2009/055371 filed May 5, 2009, which designates the United States of America, and claims priority to DE Application No. 10 2008 025 692.7 filed May 29, 2008. The contents of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention concerns waste heat use.

BACKGROUND

One technological subject which is currently of importance is the possible climate change due to greenhouse gases produced by human activity. The most prominent greenhouse gas is carbon dioxide, which in the atmosphere has a blocking effect on the thermal radiation emitted by the Earth. The debate about climate change is leading on the one hand to a politically motivated increase in the price of fossil raw materials and electricity. On the other hand the statutory rules are becoming more stringent, above all for the emission of CO₂. An important requirement for all technological fields therefore consists in the search for energy-saving solutions.

One example of such a field is an industrial plant for the electrolysis of sodium chloride, i.e. common salt. So-called chloralkali electrolysis produces the basic chemicals chlorine, hydrogen and sodium hydroxide. The chemical reaction involved is endothermic, and the required energy is supplied by means of DC electric current. Consequently, it is often desirable to achieve higher concentrations of the products. To this end, in a further step, evaporation is carried out for example by heating with the use of a kiln.

SUMMARY

According to various embodiments, a method and an arrangement can be provided with which energy saving can be made for industrial processes, for example but not exclusively the one described above. Directly or indirectly, a reduction in the emitted greenhouse gases is thereby intended to be achieved.

According to an embodiment, an arrangement may have an electrical converter, which generates waste heat, a process device and a heating device for the process device, configured in such a way that the waste heat is delivered to the heating device.

According to a further embodiment, liquid cooling can be provided for the electrical converter, which liquid cooling is furthermore configured to discharge the waste heat to the heating device. According to a further embodiment, the electrical converter can be a drive and/or a motor and the process device is an emulsion bath. According to a further embodiment, the electrical converter can be a rectifier and the process device is an evaporation installation. According to a further embodiment, the electrical converter can be a rectifier and/or inverter and the process device is a desalination installation for seawater. According to a further embodiment, the electrical converter can be a rectifier and the process device is an electrolytic coating installation. According to a further embodiment, the process device can be adapted to the electrical converter so that the waste heat is entirely sufficient for the heating in the process device.

According to another embodiment, in a method for heating in a process device, waste heat is generated in an electrical converter and the waste heat is delivered to the process device for heating.

According to a further embodiment of the method, the electrical converter can be liquid-cooled and the cooling liquid is used to transport the waste heat to the process device.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred, but in no way restrictive exemplary embodiments will now be explained in more detail with the aid of the drawing. For clarity, the drawing is not made true to scale, and said features are represented only in a schematized fashion. Parts which correspond to one another in the figures are provided with the same references. In detail, the figures show:

FIG. 1 a conventional device for electrolysis and concentration of the electrolysis products by evaporation,

FIG. 2 the device configured according to various embodiments,

FIG. 3 components of a cold rolling installation,

FIG. 4 components of a high-voltage DC transmission system with seawater desalination,

FIG. 5 components of an electrolytic coating installation.

DETAILED DESCRIPTION

The arrangement according to various embodiments comprises an electrical converter, which generates waste heat. It furthermore comprises a process device and a heating device for the process device. It is configured in such a way that the waste heat is delivered to the heating device.

In the method according to various embodiments for heating in a process device, waste heat is generated in an electrical converter and the waste heat is delivered to the process device for heating.

The electrical converter may for example be an electrical machine, for example a motor, but also a drive, rectifier or inverter. The process device may, for example, be configured to carry out a chemical reaction or a physical process. Examples of this are thermal seawater desalination or an evaporation installation.

According to further various embodiments, a plurality of individual electrical converters, even of different types, can be employed and/or the process device can support a plurality of different individual steps, all or only some of which require heating.

The effect achieved by various embodiments is that waste heat generated in any case is advantageously used for heating the process device, so that energy is saved overall. In this way, either fossil fuel is saved, which directly reduces the greenhouse gas emissions or electricity is saved, which indirectly likewise leads to CO₂ reduction.

In a configuration and refinement, liquid cooling is provided for the electrical converter.

It can be advantageously furthermore configured to discharge the waste heat to the heating device. The liquid cooling ensures on the one hand efficient cooling. It may also be quieter than fan cooling. Furthermore, by means of the cooling liquid, the waste heat can be conveyed to the process device in a very controlled way and used there for the heating. An alternative or additional possibility consists in using heat pipes for the heat transport.

A specific example of an arrangement consists in the electrical converter being a drive and/or a motor, and the process device being an emulsion bath in a cold rolling installation. In another example, the electrical converter is a rectifier and the process device is an evaporation installation in an electrolysis installation. According to another example, the electrical converter is a rectifier and/or inverter and the process device is a desalination installation for seawater.

According to an embodiment, the process device is adapted to the electrical converter so that the waste heat is entirely sufficient for the heating in the process device. In other words, the supplied heat fully replaces any other form of heating which would otherwise need to be provided for the process device. This can be done particularly straightforwardly when the process device is decoupled from the purpose of the electrical converter, i.e. arbitrarily dimensionable. Yet even in industrial installations in which the purpose of the electrical converter, for example as the electrical supply of a first process step, is dependent on the process device, corresponding dimensioning is advantageous. As an alternative, the waste heat may function as an extra heat source in addition to another form of heating, for example the burning of fossil fuels or electrical heating.

The chloralkali electrolysis already mentioned in the introduction will be used as a first example. By means of this, the basic chemicals chlorine, hydrogen and sodium hydroxide are produced from common salt. The chemical reaction involved is endothermic, i.e. it requires supplied energy 6 in order to sustain it, and the required energy is supplied by means of DC electrical current. Such an installation is represented in a highly schematized and simplified fashion in FIGS. 1 and 2. FIG. 1 shows the procedure according to the prior art, while a configuration of the installation according to various embodiments is represented in FIG. 2. In both cases, an electrolysis bath 1 is fed via a rectifier 4 from an AC electricity supply 3. Located in close proximity thereto is the device 2 for concentrating the products by evaporation, so that high concentrations of the products can be achieved.

According to the prior art, the rectifier is air-cooled, to which end fans are sometimes required. The waste heat 5 of the rectifier enters the air without being used. At the same time, the evaporation device 2 requires supplied heat energy 6.

According to the exemplary embodiment according to FIG. 2, the rectifier 4 is now liquid-cooled, the liquid cooling not being represented in the figures. In this way, on the one hand, very efficient and sometimes also quiet cooling can be achieved. On the other hand, the waste heat 5 dissipated by the rectifier 4 can be transported very well. Instead of being discharged without being used, the waste heat 5 is now fed to the evaporation installation 2. There, the waste heat 5 can reinforce the heating or under certain circumstances even replace it. Besides the delivery of the waste heat 5, other supplied heating power 6 is also represented in FIG. 2.

An energy saving is thus achieved by using the waste heat 5 of the rectifier 4 for heating the evaporation installation 2. In addition, power is also saved since cooler fans for air cooling are likewise obviated. Since energy from fossil fuels is saved in this case, the emission of greenhouse gases is directly reduced.

Components of another exemplary embodiment are represented schematically in FIG. 3. This case involves a cold rolling installation. It comprises motors 8 for a driving mechanism, which generate waste heat 7. The motors 8 are supplied with electricity via drives 10. The drives 10 also produce waste heat 11. In local proximity, there are emulsion baths 9 which need to be heated to between 60 and 80° C. In the prior art the motors 8 and drives 10 are usually air-cooled, which consumes even more energy for the fans. At the same time, the emulsion baths 9 are heated. In the prior art, for example, electrical heating or gas heating is used for this

According to various embodiments, the drives 10 for the motors are liquid-cooled in this exemplary embodiment. The waste heat 7, 11 thus discharged is used in order to heat the emulsion baths 9. The waste heat 7, 11 is delivered to both emulsion baths. Temperature regulation 12 controls the delivery of the waste heat 7, 11 and the otherwise required heating power 6. An estimate of the powers incurred in an installation according to FIG. 3 will be given below. An installed motor power of 20 MW is assumed. The efficiency of the IGCT drives 10 is 98%, i.e. a power loss of 2% of 20 MW=400 kW is produced therein. The efficiency of the motors 8 can be estimated at 97.5%, so as to give a power loss of 500 kW. In total, waste heat 7, 11 of about 900 kW is thus produced.

In this example, the heating of the emulsion baths 9 requires a power of 1800 kW. Since the waste heat 7, 11 from the drives 10 and motors 8 is about half of the heating power, up to 50% of the required heating power can be saved. With 6000 operating hours in a year, this amounts to 5400 MWh. This corresponds approximately to the energy required yearly by 1000 family households.

A third exemplary embodiment will be explained with the aid of FIG. 3. Here, the waste heat 5 in question is produced in an installation 13 for high-voltage DC transmission, specifically in the rectifiers and inverters 4 used. FIG. 3 shows only one side of the installation 13, in this case with only one rectifier 4. Conventionally, such installations 13 have a symmetrical structure so that the rectifier 4 on each side is configured in such a way that it can operate bidirectionally, i.e. it can be operated both as a rectifier 4 and as an inverter. The same cooling systems as in the first two exemplary embodiments are customarily used for this in the prior art, that is to say fan cooling. In this exemplary embodiment, however, the waste heat 5 is discharged by means of liquid cooling and used in order to operate an installation for thermal seawater desalination. This is particularly advantageous since high-voltage DC transmission is typically used for the transmission of electrical power over stretches of water, i.e. in sea cables 23 so that seawater desalination can be carried out in local proximity. Since the fan cooling is also obviated in this case and the waste heat 5 is used for an energy-intensive process, the emission of greenhouse gases is again reduced.

The first two exemplary embodiments relate to industrial installations which usually exist together in the described form and in which the energy outlay of the respective process steps can be established through the interaction of process steps. In contrast to this, seawater desalination is independent of the high-voltage DC transmission. An installation for seawater desalination 14 in conjunction with the high-voltage DC transmission system 13 can therefore be dimensioned so that the waste heat 5 of the high-voltage DC transmission system 13 is entirely sufficient for the heating required for the desalination. The design of the desalination installation is thereby even simplified, since elaborate heating can be entirely obviated.

A fourth exemplary embodiment is outlined in FIG. 5. It is an electrolytic coating installation 22, for example for zinc-plating of components. In the installation 22, components pass through at least seven process steps, namely hot degreasing 15, electrical degreasing 16, pickling and descaling 17, 18, an electrolytic coating step 19, a passivation step 20 and drying 21. The first three steps 15, 16, 17 and the drying 21 require supplied heat energy 6. On the other hand, direct current is supplied in the electrical degreasing 16 and the actual electrolytic coating 19, which is drawn via a rectifier 4 from an AC electricity supply 3. The rectifier or rectifiers 4 generate waste heat 5 in the usual way. It is distributed in this exemplary embodiment between the process steps 15, 16, 17, 21 which require heating, so as to again save on energy for the heating.

Unlike in the procedure represented in FIG. 5, it is also possible to deliver waste heat 5 merely to some of the process steps 15, 16, 17, 21 in which heating is required. In this way, when there is sufficient waste heat 5, in addition to the energy saving, the structure of the insulation 22 may possibly be simplified by the possibility of entirely obviating the other type of heating in this or these process steps 15, 16, 17, 21. By way of example, it will be assumed here that the rectifier or rectifiers 4 have an efficiency of 85%. An electrical power of 150 kW is used for the electrical degreasing 16, 22.5 kW of which are incurred as waste heat 5. An electrical power of 900 kW is used for the electrolytic coating 19, 135 kW of which are incurred as waste heat 5. In this example, overall, more than 150 kW of heating power are thus available and can be distributed in a suitable way between the corresponding process steps 15, 16, 17, 21.

Claims

1. An arrangement having

an electrical converter, which generates waste heat,

a process device and

a heating device for the process device,

configured in such a way that the waste heat is delivered to the heating device.

2. The arrangement according to claim 1, wherein liquid cooling is provided for the electrical converter, which liquid cooling is furthermore configured to discharge the waste heat to the heating device.

3. The arrangement according to claim 1, wherein the electrical converter is at least one of a drive and/or a motor and the process device is an emulsion bath.

4. The arrangement according to claim 1, wherein the electrical converter is a rectifier and the process device is an evaporation installation.

5. The arrangement according to claim 1, wherein the electrical converter is at least one of a rectifier and inverter and the process device is a desalination installation for seawater.

6. The arrangement according to claim 1, wherein the electrical converter is a rectifier and the process device is an electrolytic coating installation.

7. The arrangement according to claim 1, wherein the process device is adapted to the electrical converter so that the waste heat is entirely sufficient for the heating in the process device.

8. A method for heating in a process device, wherein waste heat is generated in an electrical converter and the waste heat is delivered to the process device for heating.

9. The method according to claim 8, wherein the electrical converter is liquid-cooled and the cooling liquid is used to transport the waste heat to the process device.

10. The method according to claim 8, wherein the electrical converter is at least one of a drive and a motor and the process device is an emulsion bath.

11. The method according to claim 8, wherein the electrical converter is a rectifier and the process device is an evaporation installation.

12. The method according to claim 8, wherein the electrical converter is at least one of a rectifier and inverter and the process device is a desalination installation for seawater.

13. The method according to claim 8, wherein the electrical converter is a rectifier and the process device is an electrolytic coating installation.

14. The method according to claim 8, comprising adapting the process device to the electrical converter so that the waste heat is entirely sufficient for the heating in the process device.

15. An system comprising

an electrical converter generating waste heat,

a process device, and

a heating device for the process device,

wherein the electrical converter is coupled with the process device such that the waste heat is delivered to the heating device.

16. The system according to claim 15, wherein liquid cooling is provided for the electrical, converter, which liquid cooling is furthermore configured to discharge the waste heat to the heating device.

17. The system according to claim 15, wherein the electrical converter is at least one of a drive and a motor and the process device is an emulsion bath.

18. The system according to claim 15, wherein the electrical converter is a rectifier and the process device is an evaporation installation.

19. The system according to claim 15, wherein the electrical converter is at least one of a rectifier and inverter and the process device is a desalination installation for seawater.