Patent Application
20210131662
Embodiments are related to a recuperative gas burner for industrial applications and to a method for operating such a gas burner.
EP 0 685 683 B1 discloses a recuperative gas burner for industrial applications. The recuperative gas burner disclosed in EP 0 685 683 B1 includes a combustion chamber and a burner tip providing an outlet opening of the combustion chamber. The recuperative gas burner further includes a gas supply having a first gas supply duct and a second gas supply duct.
Combustion gas can be provided to the combustion chamber through the first gas supply duct. Combustion gas can be also provided to the burner tip through the second gas supply duct. The recuperative gas burner also includes an air supply through which combustion air can be provided to the combustion chamber. The recuperative gas burner further includes an exhaust gas flow channel through which exhaust gas can be provided to an exhaust gas outlet. The exhaust gas flow channel and the air supply are configured such that the exhaust gas flowing through the exhaust gas flow channel heats the combustion air.
One of the challenges with recuperative gas burners such as the aforementioned recuperative gas burner is reducing NOx emissions, while increasing the efficiency of the recuperative gas burner.
Thus, there is a need for a high efficiency recuperative gas burner with reduced NOx emissions.
The following summary is provided to facilitate an understanding of some of the features of the disclosed embodiments and is not intended to be a full description. A full appreciation of the various aspects of the embodiments disclosed herein can be gained by taking the specification, claims, drawings, and abstract as a whole.
It is, therefore, one aspect of the disclosed embodiments to provide for a recuperative gas burner for industrial applications and a method of operating such a recuperative gas burner.
The aforementioned aspects and other objectives can now be achieved as described herein. In an embodiment, a recuperative gas burner can include an air supply having an inner air supply chamber with a first inlet for combustion air and an outer air supply chamber with a second, separate inlet for combustion air. The inner air supply chamber of the air supply can be configured to provide combustion air to the combustion chamber. The outer air supply chamber of the air supply can be configured to provide combustion air to the burner tip.
The outer air supply chamber of the air supply can be positioned between the exhaust gas flow channel and the inner air supply chamber of the air supply. The exhaust gas flowing through the exhaust gas channel heats the combustion air which flows through the outer air supply chamber but not or only marginally the combustion air which flows through the inner air supply chamber. Such a recuperative gas burner can be operated with a high efficiency and with reduced NOx emissions in different operation modes.
The outer air supply chamber of the air supply is preferably positioned circumferentially or concentrically around the inner air supply chamber of the air supply. The exhaust gas flow channel is preferably positioned circumferentially or concentrically around the outer air supply chamber of the air supply. The outer supply chamber and the inner air supply chamber are concentrically arranged. Further on, the exhaust gas flow channel is concentrically arranged relative to the air supply chambers. The inner air supply chamber has no contact with the exhaust gas flow channel. The outer air supply chamber, which can be positioned between the exhaust gas flow channel and the inner air supply chamber, has contact with the exhaust gas flow channel. Such a recuperative gas burner can be operated with a high efficiency and with reduced NOx emissions.
The outer air supply chamber has at least one outlet opening positioned circumferentially or concentrically around the outlet opening of the combustion chamber in the region of the burner tip. This at least one outlet opening may be dimensioned to provide a defined portion of between 70% and 90% of the combustion air required at full or maximum burner load above a temperature threshold, preferably above self-ignition temperature of the combustion gas. This allows to further increase efficiency and to further reduce NOx emissions.
The gas supply has a first pipe and a second pipe. The first pipe is positioned circumferentially or concentrically around the second pipe such that an inner gas flow channel provided by the second pipe provides the second gas supply duct. An outer gas flow channel provided between the second pipe and the first pipe provides the first gas supply duct. The inner air supply chamber of the air supply is positioned circumferentially or concentrically around the first pipe of the gas supply. The inner gas flow channel provided by the second pipe has at least one outlet opening at the burner tip positioned within the outlet opening of the combustion chamber. The outer gas flow channel provided between the second pipe and the first pipe has at least one outlet opening for the first gas supply in the combustion chamber. The inner air supply chamber of the air supply has at least one outlet opening in the combustion chamber positioned around the at least one outlet opening of the first gas supply duct. The at least one outlet opening of the first gas supply duct and the at least one outlet opening of the inner air supply chamber both provide an inlet of the combustion chamber. Such a recuperative gas burner can be operated with a high efficiency and with reduced NOx emissions.
In an embodiment, a method for operating the recuperative gas burner can involve operating in a first operation mode when a process temperature within a process chamber to be heated by the gas burner is below a temperature threshold, preferably below self-ignition temperature of the combustion gas. The recuperative gas burner can be operated in a second operation mode when the process temperature within the process chamber is above the temperature threshold, preferably above self-ignition temperature of the combustion gas. In both operation modes recuperative gas burner can be operated with a high efficiency and with reduced NOx emissions.
The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the present invention and, together with the detailed description of the invention, serve to explain the principles of the present invention.
The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate one or more embodiments and are not intended to limit the scope thereof.
Subject matter will now be described more fully hereinafter with reference to the accompanying drawings, which form a part hereof, and which show, by way of illustration, specific example embodiments. Subject matter may, however, be embodied in a variety of different forms and, therefore, covered or claimed subject matter is intended to be construed as not being limited to any example embodiments set forth herein; example embodiments are provided merely to be illustrative. Likewise, a reasonably broad scope for claimed or covered subject matter is intended. Among other issues, subject matter may be embodied as methods, devices, components, or systems. Accordingly, embodiments may, for example, take the form of hardware, software, firmware, or a combination thereof. The following detailed description is, therefore, not intended to be interpreted in a limiting sense.
Throughout the specification and claims, terms may have nuanced meanings suggested or implied in context beyond an explicitly stated meaning. Likewise, phrases such as “in one embodiment” or “in an example embodiment” and variations thereof as utilized herein may not necessarily refer to the same embodiment and the phrase “in another embodiment” or “in another example embodiment” and variations thereof as utilized herein may or may not necessarily refer to a different embodiment. It is intended, for example, that claimed subject matter include combinations of example embodiments in whole or in part.
In general, terminology may be understood, at least in part, from usage in context. For example, terms such as “and,” “or,” or “and/or” as used herein may include a variety of meanings that may depend, at least in part, upon the context in which such terms are used. Generally, “or” if used to associate a list, such as A, B, or C, is intended to mean A, B, and C, here used in the inclusive sense, as well as A, B, or C, here used in the exclusive sense. In addition, the term “one or more” as used herein, depending at least in part upon context, may be used to describe any feature, structure, or characteristic in a singular sense or may be used to describe combinations of features, structures, or characteristics in a plural sense. Similarly, terms such as “a,” “an,” or “the”, again, may be understood to convey a singular usage or to convey a plural usage, depending at least in part upon context. In addition, the term “based on” may be understood as not necessarily intended to convey an exclusive set of factors and may, instead, allow for existence of additional factors not necessarily expressly described, again, depending at least in part on context.
The gas supply 14 has a first pipe 15 and a second pipe 16. The first pipe 15 is positioned circumferentially or concentrically around the second pipe 16. An inner gas flow channel can be provided by the second pipe 16, which can provide the second gas supply duct 14b. An outer flow channel can be provided between the second pipe 16 and the first pipe 15 provides the first gas supply duct 14a.
The first gas supply duct 14a and the second gas supply duct 14b each have an own, separate gas inlet, namely the gas supply duct 14a a first gas inlet 17 and the second gas supply duct 14b a second gas inlet 18.
The inner gas flow channel provided by the second pipe 16 and thereby the second gas supply duct 14b has at least one outlet opening 19, preferably one outlet opening 19, at the burner tip 12 positioned within the outlet opening 13 of the combustion chamber 11. The gas flowing through the second gas supply duct 14b is not provided into the combustion chamber 11 but downstream of the combustion chamber 11. Seen in axial flow direction FD of the gas, the outlet opening 13 of combustion chamber 11 and the outlet opening 19 of the second gas supply duct 14b are at the same axial position of the burner tip 12. Alternatively, there may be a slight axial offset between the same.
The outer gas flow channel provided between the second pipe 16 and the first pipe 15 and thereby the first gas supply duct 14a has at least one outlet opening 20, preferably a plurality of openings 20, providing the gas into the combustion chamber 11. Seen in axial flow direction FD of the gas, the outlet openings 20 of the first gas supply duct 14a are positioned upstream of the outlet opening 19 of the second gas supply duct 14b.
The recuperative gas burner 10 further comprises further an air supply 21 and an exhaust gas flow channel 22. The air supply 21 has an inner air supply chamber 21a with a first air inlet 23 for combustion air. The air supply 21 has further an outer air supply chamber 21b with a second, separate air inlet 24 for combustion air.
The inner air supply chamber 21a can be configured to provide combustion air into the combustion chamber 11. The inner air supply chamber 21a of the air supply 21 has at least one outlet opening 25, preferably a plurality of outlet openings 25 positioned circumferentially or concentrically around the outlet openings 20 of the first gas supply duct 14a. Seen in axial flow direction FD of the gas, the outlet openings 25 of the inner air supply chamber 21a providing the combustion air into the combustion chamber 11 are positioned slightly axially offset, namely upstream, of the outlet openings 20 of the first gas supply duct 14a providing the gas into the combustion chamber 11. However, the outlet openings 25 and the outlet openings 20 may be at the same axial position.
The outer air supply chamber 21b can be configured to provide combustion air to the burner tip 12. The outer air supply chamber 21b of the air supply 21 has at least one outlet opening 26, preferably a plurality of outlet openings 26, positioned circumferentially or concentrically around the outlet opening 13 of the combustion chamber 11.
Seen in axial flow direction FD of the gas, the outlet openings 26 of the outer air supply chamber 21b providing the combustion air to the burner tip 12 are positioned slightly axially offset, namely upstream, of the outlet opening 13 of the combustion chamber 11. However, the outlet openings 26 and the outlet opening 13 may be at the same axial position.
The outer air supply chamber 21b is positioned between the exhaust gas flow channel 22 and the inner air supply chamber 21a. The outer air supply chamber 21b of the air supply 21 is positioned circumferentially or concentrically around the inner air supply chamber 21a of the air supply 21.
The exhaust gas flow channel 22 can be positioned circumferentially or concentrically around the outer air supply chamber 21b of the air supply 21. The inner air supply chamber 21a has no contact with the exhaust gas flow channel 22. The outer air supply chamber 21b, which can be positioned between the exhaust gas flow channel 22 and the inner air supply chamber 21a, has contact with the exhaust gas flow channel 22.
The exhaust gas flowing through the exhaust gas channel 22 heats the combustion air which flows through the outer air supply chamber 21b but not or only marginally the combustion air which flows through the inner air supply chamber 21a. Such a recuperative gas burner can be operated with a high efficiency and with reduced NOx emissions at different operation modes.
The exhaust gas flowing through the exhaust gas channel 22 emerges from the exhaust gas channel 22 through an exhaust gas opening 27 of the same.
The outlet openings 26 of the outer air supply chamber 21 may be dimensioned to provide a defined portion of between 70% and 90% of the combustion air required at full or maximum burner load above a temperature threshold, preferably above self-ignition temperature of the combustion gas. This is of advantage in specific operation mode of the gas burner that will be described below in greater detail.
The above described recuperative gas burner 10 can be operated in a first operation mode and a second operation mode. The recuperative gas burner 10 can be operated in the first operation mode when a process temperature within a process chamber (not shown) to be heated by the recuperative gas burner 10 is below a temperature threshold, preferably below a self-ignition temperature of the combustion gas.
The recuperative gas burner 10 can be operated in the second operation mode when the process temperature within the process chamber to be heated by the recuperative gas burner 10 is above the temperature threshold, preferably above the self-ignition temperature of the combustion gas.
When the recuperative gas burner 10 is operated in the first operation mode (see
In the first operation mode, a first portion A1 of the combustion air A is provided to the combustion chamber 11 through the inner air supply chamber 21a and a second portion A2 of the combustion air A is provided to the burner tip 12 through the outer air supply chamber 21b. The first portion A1 of the combustion air A enters into the combustion chamber 11 through the outlet openings 25 of the inner air supply chamber 21a. The second portion A2 of the combustion air A emerges out of the outer air supply chamber 21b through the outlet openings 26 of the outer air supply chamber 21b in the region of the burner tip 12.
In the first operation mode, which can also be called flame mode or visible flame mode, a primary combustion of the gas take place within the combustion chamber 11 using the first portion A1 of the combustion air A and a secondary combustion of the gas take place downstream the combustion chamber 11 using the second portion A2 of the combustion air A.
A flame ignition rod (not shown) is positioned with the combustion chamber 11 to ignite the gas/air mixture within the combustion chamber 11.
The first portion A1 of the combustion air flowing through the inner air supply chamber 21a stays relatively cool. This relatively cool combustion air A1 is mixed with the gas G within the combustion chamber 11. The flame ignition rod ignites the mixture. The second portion A2 of the combustion air flowing through the outer air supply chamber 21b is becomes heated by the exhaust gas E. The second portion A2 of the combustion air is relatively hot and is mixed with gas G not being burned within the combustion chamber 11 and with products of combustion like CO.
For process temperatures below the temperature threshold, preferably below the self-ignition temperature of the combustion gas, the first operation mode allows to reduce NOx emissions while providing a high efficiency.
When the recuperative gas burner 10 is operated in the second operation mode (e.g., see
In the second operation mode, the gas inlet 18 of the second gas supply duct 14b is opened and the gas inlet 17 of the first gas supply duct 14a is closed. Gas G can only be provided to the burner tip 12 though the outlet opening 19 of the second gas supply duct 14b.
In the second operation mode, either a major portion A3 of the combustion air A or the entire combustion air A is provided to the burner tip 12 through the outer air supply chamber 21b. In
In the second operation mode, either a minor portion A4 of the combustion air A or no combustion air is provided to the combustion chamber 11 through the inner air supply chamber 21a. In
In the second operation mode, which can also be called flameless mode or invisible flame mode, the entire combustion of the gas takes place downstream the combustion chamber 11. The combustion air flowing through the outer air supply chamber 21b becomes heated by the exhaust gas E.
When operating the gas burner 10 in the second operation mode at partial burner load between 80% und 100%, the major portion A3 of the combustion stays constant and the minor portion A4 is adapted, e.g. at 80% burner load only the outer air flow channel 21b provides combustion air.
At burner loads below 80%, the amount of the major portion A3 flowing through the outer air flow channel 21b is decreased by reducing the air pressure 30 which results in a reduced velocity of the air flowing through the openings 26. Between 80% und 100% burner load the velocity of the air flowing through the openings 26 remains constant. This is of advantage to keep NOx emissions low.
For process temperatures above the temperature threshold, preferably above the self-ignition temperature of the combustion gas, the second operation mode allows to reduce NOx emissions while providing a high efficiency.
As mentioned above, the recuperative gas burner 10 is operated in the first operation mode when a process temperature within a process chamber to be heated by the recuperative gas burner 10 is below the temperature threshold, preferably below the self-ignition temperature of the combustion gas, and the recuperative gas burner 10 is operated in the second operation mode when the process temperature within the process chamber to be heated by the recuperative gas burner 10 is above the temperature threshold, preferably above the self-ignition temperature of the combustion gas.
When the recuperative gas burner 10 is operated in the first operation mode and the temperature within the process chamber to be heated by the recuperative gas burner 10 becomes greater than the temperature threshold, preferably greater than the self-ignition temperature of the combustion gas, the recuperative gas burner 10 is automatically switched from the first operation mode to the second operation mode. In this case the gas inlet 17 which is opened in the first operation mode becomes closed and the gas inlet 18 which is closed in the first operation mode becomes opened. Further on, in this case the first air inlet 23 may become closed (see
When the recuperative gas burner 10 is operated in the second operation mode and the temperature within the process chamber to be heated by the recuperative gas burner 10 becomes smaller than the temperature threshold, preferably smaller than the self-ignition temperature of the combustion gas, the recuperative gas burner 10 is automatically switched from the second operation mode to the first operation mode. In this case the gas inlet 18 which is opened in the second operation mode becomes closed and gas inlet 17 which is closed in the second operation mode becomes opened. Further on, in this case the first air inlet 23 may become opened or the amount of air provided through the inner air chamber 21a may become increased. The flame ignition rod (not shown) being positioned with the combustion chamber 11 may than be activated.
There may be a hysteresis for switching the recuperative gas burner 10 between the above two operation modes. The disclosed embodiments can also include a recuperative gas burner 10 with two concentrically air supply chambers 21a, 21b, the inner air supply chamber 21a without contact to the exhaust gas channel 22 and the outer air supply chamber 21b with contact to the to the exhaust gas channel 22.
The recuperative gas burner 10 can be operated in two operation modes, in a first mode preferably below the self-ignition temperature in first mode and in a second mode preferably above the self-ignition temperature in the second mode.
In the first mode, lowest NOx-emissions can be realized by air staging close to stability limits. In the first mode most preferably about 40-60% of the combustion air—the first air portion A1 of the combustion air—passes the inner air supply chamber 21a and stays cool resulting in a large reduction of NOx. The remaining air—the second air portion A2 of the combustion air—can be heated while passing the outer air supply chamber 21b. In balancing the ratio of cold air provided by the inner air supply chamber 21a to the combustion chamber 11 and heated air provided by the outer air supply chamber 21b to the burner tip 12, NOx emissions can be minimized in first mode.
Above the self-ignition temperature, the recuperative gas burner 10 can be switched to the second mode. In the second mode gas can flow through the second gas supply duct 14b to the burner tip 12, simultaneously the air flowing through the outer air supply chamber 21b will be increased. The combustion air provided through the inner air chamber 21a may be reduced to 0% and the combustion air provided through the outer air chamber 21b may be increased to 100%. Due to the high speed of the combustion air, the same may be mixed with and diluted by exhaust gas downstream of the burner tip 12 and react further downstream in combustion with minimum NOx in the second mode.
The recuperative gas burner according to the present disclosure allows to almost freely select the ratio between the major portion A3 and the minor air portion in the second operation mode and to almost freely select the ratio between first portion A1 and the second air portion A2 in the first operation mode to meet customer needs of NOx emissions, air pressure and efficiency.
Thus, based on the foregoing, it can be appreciated that a recuperative gas burner for industrial applications can be implemented. The gas burner comprises a combustion chamber 11 and can include a burner tip 12 providing an outlet opening 13 of the combustion chamber 11. The gas burner can include a gas supply 14 for combustion gas having a first gas supply duct 14a and a second gas supply duct 14b. The combustion gas can be provided to the combustion chamber 11 through the first gas supply duct 14a, and wherein combustion gas can be provided to the burner tip 12 through the second gas supply duct 14b.
The gas burner can include an air supply 21 for combustion air and an exhaust gas flow channel 22 for exhaust gas, wherein the exhaust gas flow channel 22 and the air supply 21 can be configured such that combustion air can be heated by the exhaust gas. The air supply 21 also includes an inner air supply chamber 21a with a first inlet 23 for combustion air. The inner air supply chamber 21a can be configured to provide combustion air to the combustion chamber 11. The air supply 21 can include an outer air supply chamber 21b with a second, separate inlet 24 for combustion air. The outer air supply chamber 21b can be configured to provide combustion air to the burner tip 12, and the outer air supply chamber 21b can be positioned between the exhaust gas flow channel 22 and the inner air supply chamber 21a.
It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. It will also be appreciated that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
