Combustion-heated thermal processing system, recuperation device, and method for a recuperative heat exchange in a device for generating radiant heat by means of combustion

Abstract

The invention relates to a combustion-heated thermal processing system, in particular an industrial furnace (1), comprising at least one substantially closed combustion chamber (2); at least one burner (4) which is designed to burn a fuel and oxidizing agent within the at least one combustion chamber (2), thereby forming exhaust gas and generating radiant heat; at least one fuel supply; at least one oxidizing agent supply; at least one exhaust gas path; and at least one recuperation device (10) for transferring at last part of the heat content of the exhaust gas to at least one part of the fuel and / or to at least one part of the oxidizing agent. The thermal processing system is characterized in that the at least one recuperation device (10) has means for dividing the exhaust gas into partial flows, which are guided via separate recuperation paths, and in that a first recuperation path and at least one second recuperation path are provided for a heat exchange between the exhaust gas and the fuel and / or the oxidizing agent, the recuperation paths being fluidically separated from each other. The invention further relates to a method for a recuperative heat exchange between a fuel and / or an oxidizing agent during the combustion process in a device for generating radiant heat by means of combustion.

Description

[0001] Combustion-heated thermal processing plant, recuperation device and method for recuperative heat exchange in a device for generating radiant heat by means of combustion

[0002] The invention relates to a combustion-heated thermal processing plant, in particular an industrial furnace, comprising at least one substantially closed combustion chamber and at least one burner designed to combust a fuel and an oxidizing agent within the at least one combustion chamber, forming exhaust gas and generating radiant heat, at least one fuel supply and at least one oxidizing agent supply, at least one exhaust gas path and at least one recuperation device for transferring at least a part of the heat content of the exhaust gas to at least a part of the fuel and / or to at least a part of the oxidizing agent.

[0003] The invention further relates to a method for recuperative heat exchange between a fuel and / or an oxidizing agent during combustion in a device for generating radiant heat, in particular using a combustion-heated thermal processing plant of the type mentioned above.

[0004] The invention further relates to a recuperation device for use with a thermal processing plant, in particular for use with an industrial furnace designed for the combustion of a mixture of a fuel and an oxidizing agent.

[0005] The invention relates in particular to an industrial furnace for the production and / or processing of glass, ceramics, building materials, ferrous, steel, and / or non-ferrous metal materials. Preheating the oxidizing agent of a fuel is an industrially established and prior art measure for increasing the efficiency of combustion-heated thermal processing plants. Common technical solutions include central recuperators, regenerators, decentralized recuperators, decentralized regenerators, and regenerator burners. These solutions utilize various types of heat exchangers to extract heat from the combustion exhaust gas and transfer it to the oxidizing agent or oxidizer of the combustion process, typically combustion air. Combustion with pure oxygen or oxygen-enriched air as the oxidizer is an established prior art measure for increasing energy efficiency.of the efficiency of a fuel-heated system.

[0006] During combustion with air, the nitrogen contained in the air is heated along with the combustion gases and leaves the industrial furnace without participating in the process. This heated nitrogen is referred to as the nitrogen load. Combustion with pure oxygen avoids the heating of the nitrogen load.

[0007] The combination of the measures described above is only possible to a limited extent. Using oxygen as an oxidizer reduces the mass flow rate of the medium to be preheated in the heat exchanger and thus the efficiency of the heat exchanger. One possible approach is to also preheat the fuel in a heat exchanger. This is often not economical when combustion is performed with combustion air, as the fuel mass flow rate is approximately 10% of the combustion air mass flow rate, for example, when burning natural gas. In contrast, the ratio of the mass flow rates when burning natural gas with pure oxygen is approximately 2:1, so fuel preheating makes a greater contribution to the energy efficiency of the process in this case.

[0008] A generic process is known from EP 3645942 B1.

[0009] EP 3645942 B1 describes a recuperator for preheating oxygen and fuel. This recuperator has a chamber filled with non-reactive gas, which separates the flow channels for oxygen, fuel, and exhaust gas. In the event of leaks, a combustible mixture of oxygen and fuel cannot form. However, the efficiency of the heat exchanger is reduced by the additional chamber.

[0010] The invention is based on the objective of providing a combustion-heated thermal processing plant and a method of the type mentioned above, which is both safe and effective. In particular, the method according to the invention should enable optimal adjustment of the recuperation device to the fuel mass flow and / or the load of the combustion device. The invention is based on the objective of providing a recuperation device that is designed for use with a combustion-heated thermal processing plant and that enables safe and effective operation of the thermal processing plant.

[0011] The problem is solved by providing a system with the features of claim 1 and furthermore by providing a method for recuperative heat exchange with the features of claim 10.

[0012] According to the invention, a recuperation device with the features of claim 9 is further provided. Advantageous embodiments of the invention are set forth in the dependent claims.

[0013] A first aspect of the invention relates to a combustion-heated thermal processing plant, in particular a furnace, comprising at least one substantially closed combustion chamber and at least one burner designed to combust a fuel and an oxidizing agent within the at least one combustion chamber, forming exhaust gas and generating radiant heat, at least one fuel supply and at least one oxidizing agent supply, at least one exhaust gas path and at least one recuperation device for transferring at least part of the heat content of the exhaust gas to at least part of the fuel and / or to at least part of the oxidizing agent.The thermal processing plant according to the invention is characterized in particular by the fact that the at least one recuperation device has means for dividing the exhaust gas into partial flows which are guided via separate recuperation paths, and that a first recuperation path and at least a second recuperation path are provided for heat exchange between the exhaust gas and the fuel and / or the oxidizing agent, which are fluidically separated from each other.

[0014] A thermal processing plant according to the invention is preferably an industrial furnace heated with a fossil fuel, for example, natural gas. The thermal processing plant preferably comprises at least one, and more preferably a plurality, burners that combust an ignitable mixture of a fuel with an oxidizer, for example, in the form of oxygen or an oxygen-enriched gas, in a combustion chamber bounded by combustion chamber walls, releasing radiant heat. The industrial furnace can be used, for example, for the production and / or processing of glass, ceramics, building materials, ferrous, steel, and / or non-ferrous metal materials. It is particularly preferably designed, for example, as a continuous furnace, especially as a roller hearth furnace or walking beam furnace for the heat treatment of semi-finished metal products.

[0015] An exhaust gas path according to the present invention comprises one or more exhaust gas channels leading to an exhaust chimney or exhaust flue. A recuperation path according to the present invention can, for example, be a channel system in which fuel and / or an oxidizer, as well as exhaust gas, for example in the form of flue gas, are fluidically separated and brought into contact with heat exchanger surfaces. Preheating the oxidizer in the form of oxygen for combustion results in a lower heat exchanger efficiency due to a lower mass flow rate compared to air preheating. Preheating both fuel and oxygen can lead to ignitable mixtures in the event of leaks. The method according to the invention comprises the use of an oxidizer enriched with at least oxygen and the preheating of the oxidizer and the fuel.The method according to the invention has the advantage that, in particular, the division of the exhaust gas into partial flows, which are routed via separate recuperation paths, allows for the simultaneous and reliable preheating of both a highly reactive oxidizing agent, such as technically pure oxygen, and a fuel. The reactants are fluidically separated from one another and routed via different recuperation paths.

[0016] Preferably, the thermal processing plant according to the invention comprises at least one first and at least one second heat exchanger, which are fluidically separated and through which fuel or oxidizing agent and a partial flow of the exhaust gas are each passed.

[0017] Advantageously, at least one fuel supply is routed via the at least one first heat exchanger and at least one oxidizing agent supply via the at least one second heat exchanger.

[0018] Preferably, the division of the exhaust gas partial flows is controllable. A particularly advantageous embodiment of the thermal processing plant according to the invention is characterized in that at least one controllable valve is provided in at least one recuperation path of the recuperation device for dividing the exhaust gas into partial flows. This allows the mass flow ratio of the exhaust gas mass flow to be advantageously adjusted according to the mass flow ratio of fuel and oxidant. Accordingly, the control system can be configured to carry out the division of the exhaust gas partial flows according to the mass flow ratio of fuel to oxidant.

[0019] It is particularly preferred that an oxygen-enriched gas, preferably with an oxygen content of 30% by volume or greater, more preferably 60% by volume or greater, and more preferably technically pure oxygen, is used as the oxidizing agent. This is particularly advantageous because combustion with combustion air as the oxidizing agent has a lower combustion efficiency due to the nitrogen content than combustion with oxygen or oxygen-enriched air.

[0020] Preferably, the oxygen-enriched gas is oxygen-enriched air, a mixture of technically pure oxygen and recirculated exhaust gas, or a mixture of technically pure oxygen and carbon dioxide. Technically pure oxygen, as used in the present invention, is oxygen that meets the requirements of DIN EN ISO 14175.

[0021] A protectable aspect of the invention relates to a recuperation device for a thermal processing plant, in particular for an industrial furnace, comprising at least one substantially closed combustion chamber and at least one burner configured to combust a fuel and an oxidizer within the at least one combustion chamber, forming exhaust gas and generating radiant heat, at least one fuel supply, at least one oxidizer supply, and at least one exhaust gas path. The recuperation device according to the invention is characterized by means for dividing the exhaust gas into partial flows, which are routed via separate recuperation paths. A first recuperation path and at least a second recuperation path are provided for heat exchange between the exhaust gas and the fuel and / or the oxidizer, and these paths are fluidically separated from one another.

[0022] The recuperation device according to the invention preferably comprises further advantageous features, which are described above in connection with the claimed thermal processing plant. Those skilled in the art will understand that the recuperation device according to the invention can be implemented as a unit structurally separate from the thermal processing plant or the industrial furnace.

[0023] The problem underlying the invention is further solved by providing a method for recuperative heat exchange between a fuel and / or an oxidizing agent during combustion in a device for generating radiant heat, in particular using a combustion-heated thermal processing plant of the type described above, comprising the transfer of at least a part of the heat content of the exhaust gas from the combustion to at least a part of the fuel and / or to at least a part of the oxidizing agent, wherein the method comprises a division of the exhaust gas into partial streams and a guiding of the partial streams via fluidically separated recuperation paths, wherein in a first recuperation path a heat exchange is carried out between a partial stream of the exhaust gas and the fuel and in at least a second recuperation path a heat exchange is carried out between a partial stream of the exhaust gas and the oxidizing agent.

[0024] The distribution of the exhaust gas partial flows is particularly preferred, as it is controlled according to the mass flows of the fuel and oxidizer. For example, a first exhaust gas partial flow can comprise 66 percent by volume and a second exhaust gas partial flow 33 percent by volume, each based on the total exhaust gas volume. The first exhaust gas partial flow can be used, for example, for oxygen preheating, whereas, for example, in the case of natural gas combustion, the second exhaust gas partial flow can be used for fuel preheating.

[0025] Preferably, the regulation includes a division of the exhaust gas partial flows according to the mass flow ratio of fuel to oxidizing agent.

[0026] If an oxygen-enriched gas is used as the oxidizing agent, it preferably has an oxygen content of greater than or equal to 30 percent by volume, and more preferably greater than or equal to 60 percent by volume.

[0027] Preferably, the method according to the invention includes the use of technically pure oxygen.

[0028] Preferably, the oxygen-enriched gas comprises oxygen-enriched air or a mixture of technically pure oxygen and recirculated exhaust gas or a mixture of technically pure oxygen and carbon dioxide.

[0029] The invention is explained below with reference to an embodiment schematically illustrated in the accompanying drawings.

[0030] They show:

[0031] Figure 1 shows a schematic representation of an industrial furnace as a thermal processing plant in accordance with the present invention, including a recuperation device and

[0032] Figure 2 shows an enlarged view of a part of the thermal processing plant, illustrating the distribution of the mass flows of exhaust gas, fuel, and oxidizer. The industrial furnace 1 shown in Figures 1 and 2 comprises a combustion chamber 2 with boundary walls 3, into which burners 4 are inserted on both sides of the combustion chamber 2. The burners 4 are each designed to combust a fuel and an oxidizer with an open flame within the combustion chamber 2. The invention is to be understood as allowing combustion to also take place within so-called jet tubes, which can create an atmosphere separation from the atmosphere prevailing in the combustion chamber 2. The design of the industrial furnace 1 is not critical to the invention.

[0033] In the illustrated embodiment, natural gas is used as the fuel. Technically pure oxygen is used as the oxidizer, supplied to the burners 4 in a fuel-to-oxidizer ratio of 2:1. For this purpose, the burners 4 are each connected to a fuel supply line 5 and an oxidizer supply line 6. The fuel and the oxidizer are preheated in a recuperation unit 10 by means of a first heat exchanger 11 and a second heat exchanger 12. The exhaust gas produced during combustion, in this case flue gas, is fed to the recuperation unit 10 via an exhaust gas duct 7.

[0034] Within the recuperation unit 10, the heat contained in the exhaust gas is extracted via separate recuperation paths into the heat exchanger 11, 12 and supplied to the fuel and the oxidizer. The recuperation unit 10 comprises first and second recuperation channels 13, 14, each forming fluidically separate recuperation paths to which the partial flows of the exhaust gas are divided.

[0035] To adjust and control the distribution of the exhaust gas mass flows, control valves 15, 16 are provided in each recuperation channel 13, 14, which can, for example, be designed as adjustable flap valves. The flow resistance in the recuperation channels 13, 14 can be adjusted via the control valves 15, 16, thus distributing the exhaust gas mass flows among the recuperation paths.

[0036] Downstream of the recuperation unit 10, the exhaust gas partial flows are recombined in an exhaust gas duct 17. Reference numeral list

[0037] 1 industrial furnace

[0038] 2 Combustion chamber

[0039] 3 boundary walls

[0040] 4 burners

[0041] 5 Fuel supply line

[0042] 6 Oxidizing agent supply line 7 Exhaust gas duct

[0043] 10 Recuperation unit 11 First heat exchanger

[0044] 12 second heat exchanger 13 first recuperation channel 14 second recuperation channel 15 first control valve

[0045] 16 second control valve

[0046] 17 Exhaust system

Claims

Patent claims 1. Combustion-heated thermal processing plant, in particular an industrial furnace (1), comprising at least one substantially closed combustion chamber (2) and at least one burner (4) configured to combust a fuel and an oxidizing agent within the at least one combustion chamber (2) to form exhaust gas and generate radiant heat, at least one fuel supply and at least one oxidizing agent supply, at least one exhaust gas path and at least one recuperation device (10) for transferring at least a part of the heat content of the exhaust gas to at least a part of the fuel and / or to at least a part of the oxidizing agent, characterized in that the at least one recuperation device (10) has means for dividing the exhaust gas into partial flows which are guided via separate recuperation paths,that a first recuperation path and at least a second recuperation path are provided for heat exchange between the exhaust gas and the fuel and / or the oxidizing agent, which are fluidically separated from each other.

2. Thermal processing plant according to claim 1, comprising at least one first and at least one second heat exchanger (11, 12) which are fluidically separated and through which fuel or oxidizing agent and a partial flow of the exhaust gas are each passed.

3. Thermal processing plant according to one of claims 1 or 2, characterized in that the at least one fuel supply is routed via the at least one first heat exchanger (11) and that the at least one oxidizing agent supply is routed via the at least one second heat exchanger (12).

4. Thermal processing plant according to one of claims 1 to 3, characterized in that the division of the exhaust gas partial flows is controllable.

5. Thermal processing plant according to one of claims 1 to 4, characterized in that at least one controllable valve (15,16) is provided in at least one recuperation path of the recuperation device (10) for dividing the exhaust gas into partial flows.

6. Thermal processing plant according to claim 5, characterized in that the control system is designed to carry out the division of the exhaust gas partial flows according to the mass flow ratio of fuel to oxidizing agent.

7. Thermal processing plant according to one of claims 1 to 6, characterized in that an oxygen-enriched gas, preferably with an oxygen content of greater than or equal to 30% by volume, further preferably greater than or equal to 60% by volume, preferably technically pure oxygen, is provided as the oxidizing agent.

8. Thermal processing plant according to one of claims 1 to 7, characterized in that the oxygen-enriched gas comprises oxygen-enriched air or a mixture of technically pure oxygen and recirculated exhaust gas or a mixture of technically pure oxygen and carbon dioxide.

9. Recuperation device for a thermal processing plant, in particular for an industrial furnace (1) comprising at least one substantially closed combustion chamber (2) and at least one burner (4) designed to combust a fuel and an oxidizing agent within the at least one combustion chamber (2) with the formation of exhaust gas and Generation of radiant heat to be burned, at least one fuel supply and at least one oxidizer supply and at least one exhaust gas path characterized by means for dividing the exhaust gas into partial flows which are guided via separate recuperation paths, in that a first recuperation path and at least a second recuperation path are provided for a heat exchange between the exhaust gas and the fuel and / or the oxidizer, which are fluidically separated from each other.

10. A method for recuperative heat exchange between a fuel and / or an oxidizing agent during combustion in a device for generating radiant heat, in particular using a combustion-heated thermal processing plant according to one of claims 1 to 9, comprising the transfer of at least a part of the heat content of the exhaust gas from the combustion to at least a part of the fuel and / or to at least a part of the oxidizing agent, wherein the method comprises a division of the exhaust gas into partial streams and a guiding of the partial streams via fluidically separated recuperation paths, wherein in a first recuperation path a heat exchange is carried out between a partial stream of the exhaust gas and the fuel and in at least a second recuperation path a heat exchange is carried out between a partial stream of the exhaust gas and the oxidizing agent.

11. Method according to claim 10, characterized in that the division of the exhaust gas partial flows is controlled depending on the mass flows of fuel and oxidizing agent.

12. Method according to claim 11, characterized in that the control comprises a division of the exhaust gas partial flows according to the mass flow ratio of fuel to oxidizing agent.

13. Method according to one of claims 10 to 12, characterized in that an oxygen-enriched gas is used as the oxidizing agent, preferably with an oxygen content of greater than or equal to 30 percent by volume, further preferably greater than or equal to 60 percent by volume, preferably technically pure oxygen.

14. Method according to one of claims 10 to 13, characterized in that the oxygen-enriched gas comprises oxygen-enriched air or a mixture of technically pure oxygen and recirculated exhaust gas or a mixture of technically pure oxygen and carbon dioxide.

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