DE102012009519A1 - Apparatus for reducing formation of pollutants caused by combustion of flame in combustion chamber of heater, has heat conducting medium, which has component or composite material having specific ratio of thermal conductivity - Google Patents

Abstract

The apparatus has a heat conducting medium (2) in an area of flame formation, where the heat conducting medium is designed to uniformly distribute the temperature in a combustion chamber (4). The heat conducting medium has a component or composite material having a specific ratio of thermal conductivity to heat capacity. The heat conducting medium is formed by a heat pipe or a thermal superconductor, and is designed in the form of a wire, a tube, a foam or a composite.

Description

The invention relates to a device for reducing the combustion-related formation of pollutants such as nitrogen oxides or incompletely burned carbon compounds. During combustion, especially within heating appliances, thermally induced nitrogen oxides are produced due to the high flame temperatures. Also, contact burning gas mixtures with cold surfaces incomplete combustion products may arise, for. B. carbon monoxide. Nitrogen oxides as well as carbon monoxide are harmful gases. Since the combustion gases are fed into the environment, the proportion of nitrogen oxides and also the proportion of incompletely burned carbon compounds must be minimized.

State of the art for the prevention of nitrogen oxides in combustion processes is z. B. a reduction of the air ratio to a necessary for complete combustion of oxygen content, whereby a reduction of the maximum achievable flame temperature is achieved. On the other hand, the prior art for avoiding carbon monoxide in combustion processes is an increase in the air ratio, which achieves an oxygen surplus which promotes complete combustion in the mixture.

From the patent DE 37 10 244 C2 It is known to conduct a coolant line in the combustion area, which lowers the flame temperature and leads to a reduction of nitrogen oxides. The heat absorbed is dissipated and used. However, this solution has the disadvantage that it can not be used to reduce incompletely burnt carbon compounds.

Also known is the incorporation of porous structures or the use of chemically inert granules in the fluidized bed, which approximates the flame temperature to an average value, lowers peak temperatures and raises minimum temperatures. Such solutions are known as catalytic burners, pore burners, matrix burners or fluidized bed burners. By means of the above-mentioned internals, it is typical to effect a homogenization of the temperature with the lowest possible peak temperatures and, at the same time, as complete a combustion as possible. However, no useful heat can be dissipated. Such solutions are complex and expensive, require additional space or worsen the efficiency of combustion.

It is therefore an object of the invention to provide a device for preventing the formation of both thermal nitrogen oxides and unburned carbon compounds, which does not have the disadvantages mentioned above.

According to the invention, this object is achieved in that a heat-conducting agent is used to equalize the temperature, ie for cooling the areas in Berennraum with too high a temperature and for heating the areas in the combustion chamber with too low a temperature, the heat conducting means at the same time a high thermal conductivity and has a low heat capacity. As a result, it is advantageously ensured that temperature differences are compensated quickly, since during temperature changes otherwise a high amount of heat is first required for the temperature change of the heat-conducting agent. This is true for both water-filled chambers or tubes as well as for metallic or ceramic materials commonly used in combustion chambers. The quotient of thermal conductivity and heat capacity is called thermal diffusivity. Thus, according to the invention, the highest possible thermal conductivity is desired of at least 500 × 10 ^-6 m ² / s, preferably of more than 1000 × 10 ^-6 m ² / s.

Preferably, a heat conducting tube or a thermal superconductor is used as the heat conducting means. Due to the fact that a heat pipe is hollow, a very low heat capacity and thus a high thermal conductivity is achieved, which is more than a factor of 1000 above that of solid metal bodies.

According to the invention, the heat-conducting agent is in the form of a wire, a tube of a foam or a composite.

In a further development of the invention, the heat-conducting agent is connected to a heat sink. As a result, part of the heat can be dissipated and used as useful heat.

In a particularly preferred embodiment, the heat flow that is transmitted to the heat sink, controllable. Thus, in particular, the temperature of the heat-conducting agent can be adjusted by only so much heat is dissipated to the heat sink that the particular advantageous for the pollutant emission temperature is not exceeded or fallen below. This is particularly important against the background of a variable burner performance, as a low combustion chamber temperature is avoided at low burner output.

The invention will now be described with reference to 1 explained in detail. 1 schematically represents a heater 1 with a device according to the invention. The heater 1 contains a combustion chamber 4 and a supply for air and fuel 3 and an exhaust system 5 , A heat exchanger, not shown here, which is generally known from the prior art, leads to the heat produced by the combustion Useful heat to a consumer. According to the invention, one or more heat-conducting agents 2 provided, which have a high thermal conductivity, resulting from a high thermal conductivity and a low heat capacity. It is according to the invention a wire, a tube, an open-cell foam, a gas-permeable composite o. Ä. Mounted from material with high thermal conductivity. This combination of properties of high thermal conductivity and small heat capacity is particularly important in non-stationary operation, to ensure high efficiency of the device. For if the device has a high heat capacity in relation to the amount of heat converted during its operation, considerable cycle losses result due to the heat absorption of the device itself in connection with thermal load changes. The required property combination can technically z. B. in the manner of a heat pipe ("heat pipe") or z. Example, by using a thermally superconducting material or composite material ("Carbon Nanotubes" or a composite produced therefrom) are shown. This installation causes the desired homogenization of the combustion temperature. This lowers the peak temperature and reduces the formation of thermal oxides of nitrogen while ensuring the minimum temperature throughout the combustion chamber required to avoid incompletely burned carbon compounds.

In addition, with a heat exchanger 8th for decoupling the heat of combustion at one in a heat carrier line 6 guided heat carrier can be used, which transfers the heat to a heat sink 9 dissipates. There, the heat can be supplied to a consumer together with the useful heat. This is the heat-conducting agent 2 with a heat exchanger 8th connected, which transfers heat to a guided in a heat transfer line heat transfer, whereby the heat of a heat sink 9 is supplied. Advantageously, flow rate of the pump 7 controllable, so that the dissipated heat flow is controllable. Thus, with a power modulation of the burner, a temperature which is consistently favorable for perfect combustion can be set on the hot gas side of the heat-conducting medium by controlled heat absorption.

Because at the same time a removal of heat from the flame takes place, not only a homogenization of the temperature, a greater efficiency and a greater power density can be achieved because the downstream heat exchanger, not shown here for decoupling the heat from the heating gas may be smaller.

LIST OF REFERENCE NUMBERS

1

heater

2

thermally conductive agent

3

Air and fuel supply

4

combustion chamber

5

exhaust system

6

Heat transfer line

7

pump

8th

Heat exchanger

9

heat sink

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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

• DE 3710244 C2 [0003]

Claims (5)

Device for reducing the combustion-related formation of pollutants of a flame in a combustion chamber ( 4 ) of a heater ( 1 ), wherein the device has a heat-conducting means provided in the region of the flame formation ( 2 ), characterized in that the heat-conducting agent ( 2 ) is designed so that it equalizes the temperature distribution in the combustion chamber and that the heat-conducting agent of a component or composite material with a quotient of thermal conductivity to heat capacity of about 500 × 10 ^-6 m ² / s, preferably over 1000 × 10 ^-6 m ² / s exists. Device according to claim 1, characterized in that the heat-conducting agent ( 2 ) is formed by a heat pipe or a thermal superconductor. Device according to claim 1 or 2, characterized in that the heat-conducting agent ( 2 ) is in the form of a wire, a tube, a foam or a composite. Device according to one of the preceding claims, characterized in that the heat-conducting agent ( 2 ) with a heat sink ( 6 . 7 . 8th . 9 ) connected is. Device according to claim 4, characterized in that the heat-conducting agent ( 2 ) on the heat sink ( 6 . 7 . 8th . 9 ) transferable heat flow is controllable, so that the temperature of the heat-conducting agent ( 2 ) in the combustion chamber ( 4 ) is adjustable.

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