DE102022123350A1 - Heating system with a burner and a recuperator - Google Patents

Abstract

The invention relates to a heating system with a burner having a combustion chamber (10) and a recuperator (21) arranged in its exhaust duct (11), via which fresh air supplied to the combustion chamber (10) can be preheated. A thermoelectric generator (22) is integrated into the recuperator (21).

Description

The invention relates to a heating system with a burner having a combustion chamber and a recuperator arranged in its exhaust duct, via which fresh air supplied to the combustion chamber can be preheated.

Such a heating system is in the EP 2 910 855 B1 stated. The burner, which extends into a furnace space, is equipped with a heat recovery arrangement for preheating the burner air using exhaust gas heat, which has a recuperator and an additional heat exchanger surrounding it in a ring, which flow through in series. The splitting of the heat recovery arrangement into the recuperator suitable for high temperatures and the additional heat exchanger suitable for less high temperatures is designed for high efficiency. A more comprehensive principle of energy generation includes, in addition to the generation of heat, the simultaneous generation of electricity, for which this known heating system is not designed.

The principle of simultaneous production of heat and electricity is described by combined heat and power (CHP). When used decentrally, combined heat and power offers numerous advantages over separate generation of heat and electricity. The electricity generated is significantly more environmentally friendly and cost-effective than grid electricity. Conventional CHP systems include piston engines, turbines or fuel cells.

Thermoelectric generators (TEG) are suitable to make combined heat and power economical even for lower outputs. That's how it is Siddiqui and Maurya (2017) Use of Heat Recuperator for Generation of Power through Thermoelectric Generator, International Journal of Innovative Research in Science, Engineering and Technology, pp. 6527 - 6538, 6527 proposed to use a recuperator to conduct heat to a thermoelectric generator using a thermosiphon.

In Huang and Xu (2017) A regenerative concept for thermoelectric power generation, Applied Energy 185, pp. 119 - 125, 120 is designed to use a recuperator to cool the high-temperature heat from a combustion process and at the same time warm up the supplied combustion air. Thermoelectric generators are used in both material flows to generate electricity. This takes advantage of the fact that both material flows are at a lower temperature level and thus low-temperature modules can be used, which are arranged outside the recuperator.

In Qu et al. (2019) Optimization of thermoelectric generator integrated recuperator, Energy Procedia 158, pp. 2058 - 2063, 2059 is the theoretical integration of a thermoelectric generator into a recuperator of a micro gas turbine. Independent use of a burner with a recuperator and thermoelectric generator is not covered.

In Nader (2019) ThermoElectric Generator Optimization for Hybrid Electric Vehicles, Applied Thermal Engineering, p. 11, various concepts of a burner with a thermoelectric generator for vehicles are considered. Various arrangements with a recuperator are also mentioned.

Conventional systems for the simultaneous generation of heat and electricity are usually complex in design and often too cost-intensive, especially for applications with low output. CHP systems with thermoelectric generators can sometimes be used for applications with low output, but have a relatively low efficiency because, among other things, a lot of exergy is lost when the heat is transferred to the cooling medium.

The present invention is based on the object of providing a heating system of the type mentioned, with which increased efficiency in the generation of heat and electricity is achieved.

This task is achieved in a heating system with the features of claim 1. It is envisaged that a thermoelectric generator is integrated into the recuperator.

This design of the heating system results in a compact structure with low complexity and therefore low investment costs, which means that the systems can also be used economically in applications with lower power requirements. In the heating system, the fresh air or supply air supplied to the burner is mixed with fuel gas, ignited and then releases the heat into the newly supplied fresh air via the recuperating heat exchanger or recuperator with an integrated thermoelectric generator. This means that part of the exergy is recovered and can be fed back into the process. The electrical efficiency of the thermoelectric generator is therefore significantly increased as a result of its integration in the recuperator. The heat transferred from the hot combustion gas to the fresh air can be used multiple times, so that a significant increase in efficiency is achieved compared to systems known from the literature in which the recuperator is also is used in the thermoelectric generator, but is not integrated into the recuperator, which means that a smaller part of the heat can be reused and the thermoelectric generator does not have a high temperature difference available, which has a negative effect on the efficiency.

Various design variants of the heating system with an advantageous structure consist in that the recuperator is designed to preheat the fresh air by means of the hot exhaust gas in a cross-current, counter-current or co-current arrangement.

A design of the heating system that is advantageous for the structure and function is that the recuperator is arranged in a recuperating heat exchanger with an outer housing wall, in which a supply air duct and an exhaust gas duct are formed, which are enclosed by the outer housing wall, the recuperator with the integrated thermoelectric generator is arranged between the supply air duct and the exhaust duct.

Efficient operation is also achieved by having at least one subsequent heat exchanger downstream of the recuperator in the exhaust gas duct.

An advantageous embodiment is that the subsequent heat exchanger is designed to flow through a fluid that can be heated using the heat of the exhaust gas, in particular heating water.

A further advantageous embodiment for the structure and efficient operation is that the subsequent heat exchanger is a further recuperator and/or has a further thermoelectric generator integrated therein.

If it is provided that a bypass branch of a bypass branch is arranged in the exhaust duct, in particular between the combustion chamber and the recuperator, for selectively bridging at least the recuperator, different operating modes can advantageously be used, on the one hand to generate increased electrical power with higher power requirements and on the other hand , with the bypass open (bypass operation) an increased thermal output with increased heat requirements.

For this purpose, an advantageous embodiment of the heating system is that the bypass operation, which can be set by opening the bypass branch under control of an actuator, can be selected when there is an increased thermal power requirement in the exhaust duct section following the recuperator, for example when there is an increased need for heating water.

Further advantages of the invention result from the use of a heating system according to one of the preceding claims for warming up heating water and providing electrical power in a private building.

The invention also provides advantages for the application of a heating system in an industrial plant for providing heat in a thermal process and for generating electricity.

When using the heating system, natural gas, heating oil, wood or hydrogen can advantageously be used as fuel for the burner.

• 1 eine schematische Ansicht eines Heizsystems mit einem Brenner und einer in dessen Abgaskanal angeordneten Wärmeübertrageranordnung mit einem rekuperierenden Wärmeübertrager bzw. Rekuperator und darin integriertem thermoelektrischen Generator sowie einem nachgeordneten weiteren Wärmeübertrager und
• 2 eine schematische Ansicht eines weiteren Ausführungsbeispiels für ein Heizsystem mit Brenner und einer in dessen Abgaskanal angeordneten Wärmeübertrageranordnung mit einem rekuperierenden Wärmeübertrager mit darin integriertem thermoelektrischen Generator und einem nachgeordneten weiteren Wärmeübertrager, wobei der rekuperierende Wärmeübertrager mittels einer Bypassanordnung überbrückbar ist, und
• 3 einen an einem Brennraum strömungstechnisch angeschlossenen rekuperierenden Wärmeübertrager mit integriertem thermoelektrischen Generator in schematischer Ansicht.

The invention is explained in more detail below using exemplary embodiments with reference to the drawings. Show it:

• 1 a schematic view of a heating system with a burner and a heat exchanger arrangement arranged in its exhaust duct with a recuperating heat exchanger or recuperator and a thermoelectric generator integrated therein as well as a further downstream heat exchanger and
• 2 a schematic view of a further exemplary embodiment of a heating system with a burner and a heat exchanger arrangement arranged in its exhaust duct with a recuperating heat exchanger with a thermoelectric generator integrated therein and a further downstream heat exchanger, the recuperating heat exchanger being bridgeable by means of a bypass arrangement, and
• 3 A schematic view of a recuperating heat exchanger with an integrated thermoelectric generator that is fluidically connected to a combustion chamber.

1 shows a thermoelectric heating system 1 with a combustion chamber 10 of a burner (not shown) and a heat exchanger arrangement arranged in an exhaust gas duct 11 with a recuperating heat exchanger 20, which has a recuperator 21 and a thermoelectric generator 22 integrated therein, as well as a further or .subsequent heat exchanger 30.

The combustion chamber 10 is supplied with fresh air via a warm air supply 24, which is supplied via the heat exchanger 20, in particular the recuperator 21 arranged therein, by means of the heat of the exhaust gas 110 flowing out of the combustion chamber 10 is warmed up. The heat exchanger 20 or the recuperator 21 is provided with a fresh air supply connection 23 for supplying fresh air.

The subsequent heat exchanger 30 is optionally provided and is used to use residual heat present in the exhaust gas, for example. B. to warm up heating water supplied via a return line 31 to a heating system in a private building or process water to be heated in an industrial plant. The heated heating water or process water can then be supplied for further use via a flow 32. The subsequent heat exchanger 30 can also be provided with a recuperator or designed as such and also contain a thermoelectric generator integrated therein. It is possible to arrange further such heat exchangers in the exhaust duct or the exhaust gas line formed in this way.

The fresh air supplied to the burner, for example a gas burner, as supply air 240 is mixed with fuel gas and ignited, after which it absorbs heat from the exhaust gas via the recuperator 21 with the thermoelectric generator 22 integrated therein and returns it to the burner or the combustion chamber 10 as heated fresh air is supplied. In the exemplary embodiment shown, heat not transferred in the recuperator 21 is transferred from the subsequent heat exchanger 30 to the heat transfer medium flowing through it, i.e. in particular heating water.

All heat exchangers 20, 30 or recuperators 21 can be designed in a cross-current, counter-current or co-current arrangement. The optionally used subsequent heat exchanger 30 contributes to increasing the overall efficiency. In order to minimize losses, the heating water from the return 31 can also be directed into channels in the housing of the system and absorb any heat flows that would otherwise escape into the environment. Such a design is favored by the compact structure of the system with the recuperator 21 and the thermoelectric generator 22 integrated therein, whereby the recuperator 21 with the thermoelectric generator 22 can be designed as a modular unit.

The unit consisting of the recuperator 21 with the thermoelectric generator 22 integrated therein or the integrated thermoelectric modules can therefore be used advantageously, in particular for applications with lower power (e.g. below 200 kW), with the heating system designed with it providing advantageous combined heat and power -Coupling for the simultaneous generation of heat and electricity.

2 shows an embodiment variant of the system, in which the version according to 1 In addition, a bypass arrangement 4 with a bypass branch 40 and a bypass branch 41 is present, in particular to selectively bridge the recuperating heat exchanger 20 or the recuperator 21. The bypass branch contains, as a controllable actuator, e.g. B. a bypass flap or a corresponding actuator. This training with the bypass arrangement 4 offers the advantage that, for. B. two operating modes can be used. In a first operating mode, normal operation, a higher electrical power is generated, which means that if there is a higher electrical power requirement or electricity requirement, this can be generated as needed. When the bypass is open in a second operating mode, the bypass operation, less electricity is generated and more thermal power can be delivered, in the present case via the subsequent heat exchanger 30 z. B. to water to be heated, such as heating water. This offers advantages, especially if there is a higher heat requirement and this needs to be covered. Such a case is e.g. This occurs, for example, if in private buildings the thermal output of the heat generator is, as is often the case, designed for a few very cold days and otherwise operation is in the medium output range. The design mentioned can therefore also bring advantages in the dimensioning of the heating system.

3 shows schematically a recuperating heat exchanger 20 which is fluidically connected to the combustion chamber 10 and has a thermoelectric generator 22 integrated therein. The fresh air heated via the recuperating heat exchanger 20, in particular the recuperator 21, is supplied to the combustion chamber as supply air 240 mixed with fuel gas and the heat of the Exhaust gas 110 flowing from the combustion chamber 10 is transferred by means of the recuperator 21 to the fresh air passed through the recuperating heat exchanger 20. The integrated thermoelectric generator 22 supplies electrical power.

At the in 3 The exemplary embodiment shown is a section of the exhaust duct 11 and a z. B. concentrically surrounding section of a fresh air duct or supply air duct 241 from a housing wall 200 of the recuperating heat exchanger 20, the recuperator 21 with the integrated thermoelectric generator 22 z. B. is arranged concentrically between the relevant section of the exhaust air duct 11 and the supply air duct 241.

The heating system described above in various variants with the recuperator 21 and the thermoelectric genes integrated therein Rator 22 can be used in various applications. In private buildings, heat and electricity can be generated on site and the system designed in this way is much more economical and ecological than generating heat on site and purchasing electricity from the power grid. The presented technology can be used with different fuels, e.g. B. natural gas, climate-neutral wood pellets or hydrogen.

Another possible application is in the industrial sector. In thermal processes, heat can be provided in a corresponding manner and at the same time cheaper and environmentally friendly electricity can be generated.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2910855 B1 [0002]

Non-patent literature cited

• Siddiqui and Maurya (2017) Use of Heat Recuperator for Generation of Power through Thermoelectric Generator, International Journal of Innovative Research in Science, Engineering and Technology, pp. 6527 - 6538, 6527 [0004]
• Huang and Xu (2017) A regenerative concept for thermoelectric power generation, Applied Energy 185, pp. 119 - 125, 120 [0005]
• Qu et al. (2019) Optimization of thermoelectric generator integrated recuperator, Energy Procedia 158, pp. 2058 - 2063, 2059 [0006]

Claims (11)

Heating system with a burner having a combustion chamber (10) and a recuperator (21) arranged in its exhaust duct (11), via which fresh air supplied to the combustion chamber (10) can be preheated, characterized in that a thermoelectric generator (21) is inserted into the recuperator (21). 22) is integrated. heating system Claim 1 , characterized in that the recuperator (21) is designed for preheating the fresh air by means of the hot exhaust gas in a cross-current, counter-current or co-current arrangement. heating system Claim 1 or 2 , characterized in that the recuperator (21) is arranged in a recuperating heat exchanger (20) with an outer housing wall (200), in which at least one section of a supply air duct (241) and at least one section of an exhaust gas duct (11) are arranged, which are enclosed by the outer housing wall (200), wherein the recuperator (21) with the integrated thermoelectric generator is arranged between the at least one section of the supply air duct (241) and the at least one section of the exhaust duct (11). Heating system according to one of the preceding claims, characterized in that at least one subsequent heat exchanger (30) is arranged downstream of the recuperator (21) in the exhaust gas duct (11). heating system Claim 4 , characterized in that the subsequent heat exchanger (30) is designed to flow through a fluid that can be heated using the heat of the exhaust gas, in particular heating water. heating system Claim 4 or 5 , characterized in that the subsequent heat exchanger (30) is a further recuperator and/or has a further thermoelectric generator integrated therein. Heating system according to one of the preceding claims, characterized in that in the exhaust duct (11), in particular between the combustion chamber (10) and the recuperator (21), there is a bypass branch (40) of a bypass branch (41) for selectively bridging at least the recuperator ( 21) is arranged. heating system Claim 7 , characterized in that the bypass operation, which can be set by opening the bypass branch (40) under control of an actuator, can be selected when there is an increased thermal power requirement in the exhaust duct section following the recuperator (21), for example when there is an increased need for heating water. Application of a heating system according to one of the preceding claims for warming up heating water and providing electrical power in a private building. Application of a heating system according to one of the Claims 1 until 8th in an industrial plant to provide heat in a thermal process and to generate electricity. Application of a heating system Claim 9 or 10 , where natural gas, heating oil, wood or hydrogen are used as fuel for the burner.

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