DE102014019766A1 - infrared Heaters - Google Patents

Abstract

The invention relates to an infrared radiator (1) with a burner (2) and at least one radiation element (3), wherein a mixture of gas (4) and air (5) is burned by means of the burner (2). It is known that a mixing ratio of gas (4) and air (5) necessary for complete combustion of the mixture varies depending on the nature of the gas (4), in particular its calorific value. The invention now proposes that a current mixing ratio and / or the type of gas (4) is detected and / or measured by means of a sensor (6), wherein a comparison result of the current mixing ratio and the necessary mixing ratio is created, and wherein the Burner (2) gas (4) and / or air (5) is supplied in response to the comparison result until the current mixing ratio is substantially equal to the necessary mixing ratio.

Description

The invention relates to an infrared radiator having at least one burner and at least one radiation element, wherein a mixture of gas and air is burned within the burner.

Complete combustion occurs when organic matter burns and, ideally, only CO ₂ and H ₂ are produced. On the other hand, incomplete combustion, ie incomplete combustion, also produces other products such as carbon black and / or CO.

Infrared radiators in the context of this application are, for example, dark radiators or even light radiators.

Dark radiators have one or more radiation tubes as radiation elements, to which at least one burner is assigned. The combustion of a mixture of gas and air within the burner creates a flame which can be distributed by means of a blower over the entire length of the radiant tube. The radiant tube is thereby heated evenly up to 650 ° C and generates heat radiation, which, if necessary, with the help of reflectors, is radiated to a region to be heated. The resulting during combustion exhaust gases are removed by means of the blower from the radiant tube and optionally supplied via exhaust pipes of the outside air. Alternatively, the exhaust gases can be at least partially recirculated and thus supplied to the combustion.

Light radiators regularly have one or more burner plates with jet surfaces of perforated ceramic or high temperature resistant steel, and one or more mixing chambers in which gas and air are mixed. As with the dark radiators, it is also possible to provide reflectors for deflecting the emitted beams to the recreation room or to a surface to be heated. The exhaust gases of light radiators can be dissipated indirectly via the room air. Alternatively, the exhaust system is also possible via exhaust pipes.

In order to achieve a complete combustion of the mixture of gas and air, it is necessary that gas and air have a certain stoichiometric ratio to one another. If the optimum stoichiometric ratio for a complete combustion is not achieved, incomplete combustion of the gas occurs, causing pollutants. This not only affects the environment but also reduces the heat output of the infrared heater. Thus, it is necessary to always keep the mixing ratio of gas and air at a value required for complete combustion, which in practice occurs by means of adjusting the supply of gas and / or air to the burner.

So far, infrared radiators, i. Both dark radiator and light radiator, with always the same type of gas, namely, for example, natural gas operated. In this case, the gas always has a constant quality, i. Composition, on. Essential here is the so-called "calorific value", which indicates the thermal energy contained in the gas per unit of measurement. In the case of a gas change in the public gas supply or a partial admixture of other types of gas, e.g. Biogas, it comes with constant volumes of the supplied gas to a reduction of the radiant power or to a thermal overload, since the calorific value of the gas changes and thus the necessary mixing ratio of gas and air for complete combustion.

It is therefore the object of the present invention to provide an infrared radiator, in which a complete combustion of the mixture of gas and air is ensured even if the type of gas changes during operation of the infrared radiator.

To solve the above object, an infrared radiator with the features of claim 1 is proposed. In the case of the infrared radiator, a mixture of gas and air is burned by means of the burner, a mixing ratio of gas and air which is necessary for complete combustion of the mixture varying depending on the type of gas, in particular its calorific value, a current mixing ratio and / or or the type of gas is detected and / or measured by a sensor, wherein a comparison result of the current mixing ratio and the necessary mixing ratio is created, and wherein the burner gas and / or air is supplied depending on the comparison result until the current mixing ratio in Essentially equal to the necessary mixing ratio.

The term "necessary mixing ratio" in the sense of the invention is understood to mean a mixing ratio which, in the ideal case, corresponds to a complete combustion of gas and air. In this respect, this describes a state of combustion in which the smallest possible amount of combustible gases such as CO, CH ₄ or H ₂ remains in the exhaust gas. The ideal case would be a combustion state in which the components of the gas and the air react exclusively to CO ₂ and H ₂ O.

The invention adjusts the quantity of gas and / or air quantity supplied to the combustion process to temporally fluctuating gas qualities. The invention is based on the recognition that for a complete combustion of the mixture always a certain mixing ratio of gas and air is required, which mixing ratio depends on the type of gas, since for example natural gas has a different calorific value than biogas. According to the invention, the type of gas and / or the current mixing ratio of gas and air is either detected manually or measured by means of a sensor.

In the simplest case, the user of the infrared radiator can be informed by the utility that the nature of the gas is changing. In order to ensure optimal combustion of the gas-air mixture, the user of the infrared radiator manually detects the type of gas. This happens, for example, by indicating the current gas at a control device assigned to the infrared radiator. As a result, it causes gas and air to be mixed with each other in a mixing ratio suitable for the respective gas. Thus, even with changes in the type of gas optimum combustion can be ensured.

Alternatively, the type of gas and / or the current mixing ratio can be measured by means of a sensor. In this case, a change in the current mixture ratio and / or the type of the current gas is automatically detected. If it is detected or measured that the type of gas has changed and / or the necessary mixing ratio for the complete combustion is not given because the gas used, for example, a biogas content is mixed, the necessary mixing ratio can be restored by the gas burner and / or air is supplied in an amount which is suitable to ensure the substantially complete combustion of the mixture. Overall, this results in a manually or automatically adjustable method, which always ensures optimal and low-emission operation of the infrared radiator with constant heating power.

The invention provides that the type of gas and / or the current mixing ratio is determined by means of a measurement of the composition of the exhaust gas produced during combustion, in particular a measurement of the type and / or quantity of the constituents. The combustible components of the gas are carbon and hydrogen, besides there are sometimes small amounts of sulfur, which are undesirable. Ingredients that do not participate in the combustion (so-called Inerte) are eg nitrogen or carbon dioxide. If the components of the gas and the air react to CO ₂ and H ₂ O, there is complete combustion. However, if flammable gases such as CO, H ₂ and CH ₄ or soot occur after combustion, incineration is incomplete. Depending on the nature of the constituents present after combustion, it can thus be concluded whether the combustion took place completely or incompletely. If not only the type of components is determined, but at the same time their quantity, it can also be concluded in which mixing ratio of the gas and the air to each other. Depending on the presence of certain Inerte can be closed at the same time on the nature of the gas.

In incomplete combustion, flammable gases such as CO, CH ₄ or H ₂ occur in the exhaust gas. The cause can be, for example, a lack of air. The incomplete combustion can also be recognized by the fact that no free oxygen can be detected in the exhaust gas. On the other hand, an optimum mixture ratio of gas and air for complete combustion of the mixture is characterized by the fact that the excess air in the combustion is as low as possible. If there are still portions of air after combustion, it is a non-optimal mixing ratio, which can be prevented by increasing the gas content.

The invention further provides that the type of gas and / or the current mixing ratio is determined by means of a measurement of the temperature of the exhaust gas produced during the combustion. The presence of a mixture ratio necessary for a complete combustion of the mixture can be determined on the basis of the temperature of the exhaust gas produced during the combustion. In a complete combustion of the gas-air mixture, the exhaust gas would reach a theoretical combustion temperature. So if now the temperature of the exhaust gas is measured, it can be determined whether a complete combustion is present or not. Depending on the measured temperature value can then be restored by means of an addition of gas or air, the optimum mixing ratio.

Alternatively or additionally, the type of gas and / or the current mixing ratio can also be measured by means of a measurement of the ions formed during combustion. The high temperatures and the chemical reactions occurring during the combustion cause a partial ionization of the combustion products. The resulting by applying a voltage lonisationsstrom can be measured and provides information on the presence of a complete or incomplete combustion of the mixture. In this case, the optimum mixing ratio can be kept constant by the actual supply of gas and / or air is readjusted.

The invention further provides that the gas and the air are mixed prior to introduction into the burner. So far, the gas was usually supplied separately to the burner and atmospherically mixed with air. When the gas is changed, such atmospheric mixing of the gas with air may no longer be possible. Therefore, the gas is now deliberately premixed before introduction into the burner with the air and fed the finished homogeneous mixture to the burner. This is advantageously done within a mixing section. The gas and the air of the mixing section are fed separately, wherein advantageously the air is conveyed by means of a blower in the mixing section and the gas flow is regulated by means of a valve. Gas and air mix while striving towards a common outlet opening located at the opposite end of the mixing section. This allows a uniform mixture of gas and air can be achieved. The fact that the air is introduced by means of a blower in the mixing section, it is ensured that gas and air are present with the desired mixing ratio.

In the case of the dark radiators known in the prior art, only a partial premix of the gas-air mixture has hitherto been carried out. In this case, about 40% of the mixture was mixed in the burner itself, while the remaining 60% were mixed over the length of the radiation element to achieve the longest possible flame. Now this Teilvormischung omitted, whereby the mixing ratio is constant at best over the entire length of the radiation element and the proportion of nitrogen oxides formed during combustion decreases.

Overall, the mixture of gas and air prior to introduction into the burner results in a better measurability of the composition and temperature of the exhaust gases produced during combustion and of the ionization current produced during combustion. Now there is an identical composition of the combustion products at all positions within the radiation element, so that the measured values need only be measured at an arbitrary position and are also meaningful for the remaining positions. This results in a particularly simple arrangement of the sensors and evaluation of the measurement result.

In the context of the invention, it is provided that the amount of the mixture to be combusted is automatically adjusted as a function of environmental parameters, in particular of a current heat requirement. Thus, the heat emitted by the radiating element can be effectively controlled by decreasing or increasing the volume of the gas-air mixture.

The infrared radiator has a burner for combustion of a gas and air mixture and at least one radiation element, and has means for detecting and / or measuring the actual mixing ratio of gas and air and / or the type of gas and by a control device which is formed is to compare the current mixing ratio with a necessary for a complete combustion mixing ratio and gas and / or air supplied to the burner until the current mixing ratio is equal to the necessary mixing ratio.

The device for detecting and / or measuring the current mixture ratio may advantageously comprise one or more sensors, in particular a sensor for measuring the composition of the exhaust gas produced during combustion, a sensor for measuring the temperature of the exhaust gas produced during combustion and / or a sensor for measuring the ions produced during combustion.

In addition, the infrared radiator can have isolated reflectors to increase the proportion of radiation in the heat transfer of the radiator. This results in a higher overall efficiency of the infrared radiator.

There are each infrared radiators are provided, in which the fan acts to promote the air oppressive, that is the input side mounted on the burner, or infrared radiator, in which the blower to promote the air and the exhaust gases sucking, that is mounted at the end of the radiating element.

Advantageously, the thermal power and / or radiant power of the infrared radiator is automatically adjusted in several stages or infinitely modulating to the current heating demand. Advantageously, the infrared radiator can be equipped with a controllable fan and / or a control valve whose delivery volume is automatically adapted to the current amount of gas.

The air used for the mixture can be obtained from the room to be heated itself or by a corresponding rigid or flexible line from the outside. The exhaust gas of the infrared radiator can be removed indirectly from the room to be heated, ie together with the room air, or directly, ie with a suitable exhaust pipe from the room. In the exhaust pipe In this case, a heat exchanger, for example an exhaust gas air heat exchanger or an exhaust gas water heat exchanger can advantageously be installed, which uses the residual heat, for example for heating the room or the building. The invention further provides that a number of radiators have a common exhaust pipe to lead the exhaust gases from the room to the outside, wherein in the exhaust pipe, a heat exchanger can be installed, which uses the residual heat of the radiating element for heating the room or the building ,

Advantageously, the waste gas volume flow of the radiating element is used to preheat the air used for the mixture. As a result, the efficiency of the infrared radiator can be additionally increased.

Additionally or alternatively, it can also be provided that part of the exhaust gas volume flow is conducted back to the burner, in order to increase the efficiency of the infrared radiator and to reduce the pollutants, in particular NOx, formed during the combustion. Advantageously, the amount of the recirculated exhaust gas volume flow is automatically varied in dependence on the amount of gas supplied differently depending on the current heat demand. Advantageously, the recirculated exhaust gas volume flow increases with decreasing gas quantity.

The control device for automatically adjusting the amount of gas and / or air can, depending on the gas quality, have a pneumatically operated gas-air supply system or an electronically operated gas-air supply system. Likewise, the automatic adjustment of the amount of air and the use of a motor or thermally operated shutter, such as an iris diaphragm in the air inlet of the burner, possible.

Furthermore, the infrared radiator can be equipped with one or more temperature monitors or temperature limiters to monitor and limit the temperatures of relevant components, such as the burner or radiation element, with changing gas qualities.

In the context of the invention can also be provided that the infrared radiator has a plurality of parallel in the flow direction mounted side by side radiation elements, the vorstrahl arranged in the flow direction radiating segments are provided with an inner insulation. As a result, an optionally increased near the burner temperature of the radiation element does not lead to a considerable inhomogeneity of the radiated power over the longitudinal extent of the radiation element.

• 1 einen Dunkelstrahler;
• 2 einen Hellstrahler.

In the following the invention will be explained in more detail by means of exemplary embodiments. Show it:

• 1 a dark radiator;
• 2 a light radiator.

An inventive dark radiator according to 1 has a burner 2 with a mixing chamber 8th and a radiating element 3 on, being at the mixing chamber 8th on the input side a blower 7 and a gas valve 10 are arranged, which are suitable, the flame formed during the combustion as evenly as possible over the entire length of the radiation element 3 to extend. At the burner 2 opposite side of the radiating element 3 is an exhaust pipe 9 arranged, which is formed during combustion exhaust gases from the radiation element 3 derives. The burner 2 is with the help of the blower 7 air 5 and with the aid of the gas valve 10 gas 4 fed, with blower 7 and valve 10 can be controlled by means of a control device and thus more or less gas 4 or air 5 in the burner 2 introduce.

In the area of the burner 2 are one or more sensors 6 arranged, which can detect certain components of the exhaust gas composition. These can be sensors, for example 6 for O ₂ , CO ₂ , H ₂ O, CO, H ₂ , CH ₄ and / or carbon black. In addition, in the area of the burner 2 likewise a temperature sensor and / or an ionization current sensor can be arranged.

The invention works so that the guided over the supply lines gas 4 or the air 5 inside the mixing chamber 8th be mixed together and then inside the burner 2 to be burned. The gas sensors 6 detect the components of the gas-air mixture arising or remaining during combustion. If, for example, flammable gases such as CO, H ₂ , CH ₄ or soot are detected after combustion, incomplete combustion can be inferred. In this case, it is necessary to regulate the supplied air flow so that a larger amount into the mixing chamber 8th is admitted. This allows the current mixing ratio between gas 4 and air 5 be adjusted so that this corresponds to the necessary for a complete combustion of the mixture mixture ratio.

In addition, the temperature of the exhaust gas produced during combustion can be measured by means of a temperature sensor. If the measured temperature corresponds to the given theoretical temperature for complete combustion, it can be concluded that the mixing ratio of gas 4 and air 5 optimal.

In addition, a sensor for measuring an ionisationsstromes measure the resulting during combustion lonisationsstrom. This ionization current is compared with a predetermined setpoint which is associated with an optimal mixing ratio. Depending on the difference between the measured ionisationsstrom and the setpoint, the supplied amount of air is changed.

The control device thus regulates depending on the measurement results of the individual sensors 6 the mixing ratio between gas 4 and air 5 , This allows the complete (low-emission) combustion of the mixture even with different compositions or qualities of the gas 4 be ensured. Likewise, the highest possible efficiency of the infrared radiator results.

As previously shown by means of a dark radiator, the invention can also be transferred to light radiators. this shows 2 ,

An inventive light radiator has a radiating element 3 (Burner plate) with burners arranged therein 2 on. gas 4 and air 5 be first a mixer 11 fed. This mixing device 11 is designed in the form of a mixing section, wherein gas 4 and air 5 to flow to the common output of the mixing device 11 and mix it. The air 5 is using a blower 7 in the mixing device 11 blown while the gas 4 by means of a gas valve 10 is supplied. The mixture enters the mixing chamber 8th where it is by means of the burner 2 is burned. The resulting exhaust gases are detected by sensors 6 measured with respect to their composition, temperature and / or their ionization current. The further evaluation and regulation takes place in accordance with the method described with reference to the dark radiator.

LIST OF REFERENCE NUMBERS

1

infrared Heaters

2

burner

3

radiating element

4

gas

5

air

6

sensor

7

fan

8th

mixing chamber

9

exhaust pipe

10

gas valve

11

mixing device

Claims (11)

Infrared radiator (1) with at least one burner (2) for combustion of a mixture comprising gas (4) and air (5), at least one radiation element (3) and a fan arranged at the end of the radiation element (3) for sucking the air and the air Exhaust gases, characterized in that the thermal performance and / or radiation power of the infrared radiator (1) is automatically adjustable in several stages or continuously modulating the current heating demand with the controllable fan and / or a control valve. Infrared emitter (1) after Claim 1 , characterized in that the delivery volume of the controllable blower and / or the control valve is automatically adapted to the current amount of gas. Infrared emitter (1) after Claim 1 characterized in that means are provided for detecting and / or measuring the actual mixing ratio of gas (4) and air (5) and / or the nature of the gas (4) and a control device having a current mixing ratio with one for one compare complete combustion necessary mixing ratio and the burner (2) gas (4) and / or air (5) supplied until the current mixing ratio is equal to the necessary mixing ratio. Infrared emitter (1) after Claim 3 , characterized in that the means for detecting and / or measuring comprises one or more sensors (6). Infrared emitter after Claim 4 , characterized in that the sensor (6) is designed to measure the composition of the exhaust gas produced during combustion. Infrared emitter after Claim 4 or 5 , characterized in that the sensor (6) is designed for measuring the temperature of the exhaust gas formed during combustion. Infrared emitter after one of the Claims 4 to 6 , characterized in that the sensor (6) is designed for measuring the ions formed during combustion. Infrared emitter after one of the Claims 1 to 7 , characterized in that isolated Reflectors are provided which increase the radiation component in the heat transfer. Infrared emitter after one of the Claims 1 to 8th , characterized in that the end of the radiation element is connected to an exhaust pipe, which has a heat exchanger, in particular an exhaust gas-air heat exchanger or an exhaust gas-water heat exchanger. Infrared emitter after one of the Claims 1 to 9 , characterized in that a part of the exhaust gas volume flow at the end of the radiation element to the burner is traceable, wherein the return is variable in particular automatically depending on the different depending on the current heat demand gas quantity. Infrared emitter after one of the Claims 1 to 10 , characterized in that the infrared radiator is designed as a dark radiator with a jet pipe.

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