Method and burner for thermally removing harmful substances from process gases

Abstract

The invention relates to a method for thermally removing harmful substances from a process gas, wherein combustion gas and oxygen are introduced into a combustion chamber (19) of a burner (1) and ignited there in order to generate a flame for burning the harmful substances, wherein a dilution gas is introduced in order to reduce the combustion value of the mixed gas compared to the combustion gas, and in order to adjust the mixed gas consisting of dilution gas and combustion gas, the gas flow rate of the dilution gas is adjusted as a function of the composition of the process gas. The invention also relates to a burner (1) for generating a flame (2) in a combustion chamber (19) for burning harmful substances in a process gas, and to an exhaust gas treatment device having at least one burner (1) arranged in the combustion chamber (19).

Description

Technical Field

[0001] The invention relates to a method for thermally removing harmful substances from a process gas. The invention also relates to a burner for generating a flame in a combustion chamber for burning harmful substances in a process gas and an exhaust gas treatment device having at least one burner arranged on the combustion chamber. Background Art

[0002] In many industrial process plants for processing semiconductor materials or for the production of photovoltaic cells, gases are used for layer deposition and etching. The reactive and environmentally hazardous process gases and the reaction products produced in the process are usually disposed of by local waste treatment plants adjacent to the process plants. Such toxic gases also accumulate in large quantities, for example, during the production of semiconductor circuits and cannot be introduced into the environment untreated due to their toxicity.

[0003] In addition to the process gases of the chemical vapor deposition (CVD) process or the dry etching process, waste gases containing harmful substances from other processes can also be treated by the present invention. The toxic or environmentally harmful gases are, for example, SiH4, SiH2Cl2, SiF4, NH3, PH3, BCl3, SF6 or NF3.

[0004] In the case of an increasing need for substrates modified in this way, a correspondingly increasing proportion of process gases is also produced which have to be treated in order to ensure environmental and health compatibility.

[0005] For this purpose, the usual method is to clean by burning and then wash with a washing liquid. It is known that the burner is arranged in the cover of the combustion reactor and conveys the harmful gases through a plurality of pipes which lead to the vicinity of the flame.

[0006] The reaction products of the heat treatment exist in gaseous form or in solid form. After washing away the gas and solid particles soluble in water, the remaining gaseous reaction products, such as water vapor or CO2, can be introduced into the environment without further post-treatment.

[0007] It is understood that a number of combustion methods and reaction chambers have been developed and are used in practice for heat conversion. Thus, EP 0 346 893 B1 discloses an assembly for cleaning exhaust gases, which assembly consists of a reaction chamber, in which a burner is arranged at the bottom, which burner is operated with combustion gases, such as hydrogen and oxygen, on the one hand, and to which the exhaust gases to be cleaned are fed on the other hand. The reaction products produced during the combustion contain not only solid components, but also water-soluble reaction products.

[0008] A thermal treatment device for exhaust gases containing pollutants is known from KR 10 1 275 475 B and CN 102 644 928 B. The substances are converted into other compounds. The thermal treatment device has a combustion chamber, one or more burners, one or more exhaust gas inlets and an exhaust gas outlet.

[0009] DE 10 342 692 A1 discloses a device with a combustion chamber, on which at least one burner is located on a cover arranged at the top, so that the flame is directed from top to bottom into the combustion chamber. In addition, there is a supply device for washing liquid, by which a closed film can be formed on the entire inner circumference of the combustion chamber.

[0010] DE 10 2004 047440 A1 discloses a reactor chamber having an outer wall and an inner wall, wherein the inner wall tapers downwards in a funnel-like manner at a predetermined angle, and a device for thermally treating toxic gases is arranged on the reactor chamber closed upwards. The inner wall of the reactor chamber has a uniformly downwardly flowing water film on the inner side.

[0011] JP 2017 089985 A discloses an exhaust gas treatment device for thermally cleaning exhaust gases, which has a combustion chamber for burning the exhaust gases. The ignition device has an air-fuel premixing chamber and an ignition plug for generating an ignition flame.

[0012] US 2017 065 934 A1 and US 9956525 B2 disclose a device for cleaning exhaust gas of an integrated semiconductor, which has a cover with a burner mounted thereon for generating a flame and a plurality of exhaust gas inlet pipes. A water curtain prevents byproducts from accumulating on the device.

[0013] Since high temperatures are required for the removal of stable fluorides used in the process, such as carbon tetrafluoride (CF4), hexafluoroethane (C2F6) or sulfur hexafluoride (SF6), combustion with natural gas or methane as combustion gas and oxygen as oxidant is usually used for this purpose. Fluorides cannot be removed with sufficient efficiency in combustion with a flame using natural gas as combustion gas and air as oxidant. Therefore, combustion with oxygen as oxidant is used for this purpose.

[0014] High temperatures are achieved by combustion with oxygen, but thermal nitrogen oxides (NOx) are always produced in this process. The required combustion temperature and the optimum stoichiometry of the flame may also depend on the specific process gas.

[0015] WO 2020 / 104804 A1 discloses a method based on the combustion of natural gas with air, wherein the combustion gas is mixed with the harmful gas and oxygen is added in the vicinity of the harmful gas. In addition, argon or carbon dioxide, which is proposed there, is used as a diluent gas.

[0016] Alternative technologies according to KR 101 174 284 B, KR 101 405 166 B1, KR 2012 0021 651 A, WO 2012 140425 A1, JP 2013 193 069 (A), KR 2015 0139 665 A and KR 101 600522 B are based on plasma, such as arc plasma or microwave plasma. For example, the catalytic method known from JP 2007 090 276 A cannot be implemented in this application area due to a large number of impurities.

[0017] Since a plurality of different process gases are used in semiconductor production and the gas composition is also variable during the process, it may happen that the combustion temperature actually required for the exhaust gas removal is lower than the combustion temperature in the burner and thus thermal nitrogen oxides are produced unnecessarily. Since nitrogen oxides have harmful effects on the environment and health, their emission should be as small as possible and they are usually limited by regulations. Summary of the invention

[0018] Starting from the aforementioned disadvantages, the object of the present invention is to provide a method and a burner which allow different gas mixtures to be cleaned under optimal conditions, in particular in which the generation of thermal nitrogen oxides is suppressed as much as possible, but the conversion of the gas to be cleaned is nevertheless ensured.

[0019] This object is achieved by a method for the thermal removal of pollutants from a process gas.

[0020] The object is also achieved by a burner for generating a flame in a combustion chamber for burning pollutants in a process gas and by an exhaust gas treatment device having at least one burner arranged on the combustion chamber.

[0021] The invention relates to a method for thermally removing pollutants from a process gas, wherein combustion gas and oxygen are introduced into a combustion chamber of a burner and ignited there in order to generate a flame for burning the pollutants.

[0022] A dilution gas, such as an inert gas, particularly nitrogen, is introduced to reduce the combustion value of the mixed gas compared to the combustion gas, and the gas flow rate of the dilution gas is adjusted according to the composition of the process gas to adjust the mixed gas composed of the dilution gas and the combustion gas.

[0023] In particular, the gas flow of the diluent gas can be adjusted according to the composition of the process gas of the input gas flow from different previous processes, such as a CVD process or a dry etching process. The information about the input gas flow can be, for example, which process chamber of the previous process is active or which process the corresponding process chamber implements.

[0024] In the case of scavenging unreactive nitrogen-containing fluorinated compounds (PFCs), i.e., essentially all PFCs except NF3, nitrogen oxide (NOx) emissions originate primarily from thermal NOx generation. In the case of burners used here where combustion gas and oxygen are mixed in the burner output region, temperature peaks are usually primarily in the only small mixing region of the process flame. NOx generation is significantly less in burners with natural gas and air due to the lower peak temperatures.

[0025] For this reason, according to the invention, a dilution gas is added to reduce or lower the combustion value of the mixed gas compared to the combustion value of the pure combustion gas, so that the peak temperature in the hottest combustion region is reduced by diluting the combustion gas.

[0026] The method comprises burning the process waste gas to be treated by means of a flame generated by a burner, wherein the flow rate of a dilution gas, for example nitrogen, which is admixed into the combustion gas is adjusted as a function of the composition of the process waste gas to be treated.

[0027] Due to the method according to the invention, the NOx generation is significantly reduced while the removal efficiency is nevertheless ensured.

[0028] The method also allows the dynamic adjustment of different gas components to be purged by regulating the gas flow in the burner. This is achieved by influencing the combustion gas composition, in particular by regulating the admixture of a diluent gas such as nitrogen or another inert gas into the combustion gas.

[0029] By mixing nitrogen into the combustion gas, the combustion reaction is slowed down and a lower maximum temperature is thus achieved in the hottest region of the burner flame. Since the generation of thermal NOx is determined by the maximum temperature, less NOx is generated.

[0030] It has been determined experimentally that during the removal of CF 4 the decomposition of CF 4 is however also determined by the maximum temperature reached in the process waste gas.

[0031] The removal of other substances to be processed is significantly less influenced by the maximum temperature in the flame. However, by admixing the dilution gas, not only the temperature is reduced, but also the flame extension is increased. This allows a stronger mixing of the process gas with the flame and leads to an increased reaction of the pollutants. Thus, when removing other stable fluorides, such as sulfur hexafluoride (SF6) and hexafluoroethane (C2F6), the flame temperature can be reduced, for example, without loss of removal efficiency, but with a significant reduction in the generation of hot NO.

[0032] However, too strong a dilution of the combustion gas or of oxygen also impedes the destruction of the fluorides. Therefore, in the combustion with natural gas as the combustion gas, sulfur hexafluoride (SF6) cannot be eliminated if only air is used as the oxidant. The use of natural gas with a flame diluted with oxygen or air enriched with oxygen has not been shown to be advantageous in the same way as the use of natural gas or methane diluted with nitrogen.

[0033] According to a first advantageous design of the invention, the dilution gas is mixed into the combustion gas before being introduced into the combustion chamber. In particular, it can be provided that the dilution gas is mixed into the combustion gas before a flame is generated to burn harmful substances and / or before the combustion gas is mixed with oxygen.

[0034] The method can be used in particular for catalytic burners. It is advantageous here that the combustion gas or diluted combustion gas is introduced into the combustion chamber or premixing chamber separately from oxygen and the two gas streams are brought together only immediately before the reaction. This achieves that the diluted combustion gas meets the oxygen that has not yet been diluted in the reaction area. Therefore, no fuel-rich reaction area is formed at the interface between the diluted combustion gas and the undiluted oxygen. On the contrary, a combustion gas-rich area is formed at the interface between the diluted oxygen and the undiluted combustion gas. However, in the combustion gas-rich area, so-called "prompt NOx (quick nitrogen oxides)" are generated. That is to say, by diluting the combustion gas, not only the peak temperature is reduced and the thermal NOx generation is thereby reduced, but also the prompt NOx generation is reduced.

[0035] In burners with separate supplies for combustion gas and oxygen, the relative speed and volume of the two gas flows and thus also the mixing properties are influenced by the dilution gas. When using methane as combustion gas, the stoichiometric ratio to oxygen is 1:2. By mixing the dilution gas into the combustion gas, the volumes of the two gas flows become similar. The output velocities become equal to one another and thus less turbulence is generated in the mixing region and combustion proceeds more slowly.

[0036] The diluent gas can advantageously be an inert gas, for example nitrogen.

[0037] According to another advantageous embodiment of the invention, the amount of oxygen and / or combustion gas flowing into the combustion chamber and / or the amount of dilution gas mixed into the combustion gas are individually regulated. In this way, different gas components to be purged can be dynamically adjusted.

[0038] According to an advantageous further development of the invention, it is provided that information about the composition of the process gas, i.e. a signal, is transmitted to a control device for the gas flow rates of the combustion gas, oxygen and / or dilution gas, and that the combustion gas composition is dynamically adjusted by the control device for the gas flow rates as a function of the information. The information about the composition of the process gas can be derived in particular from the operating state of a process preceding the method for thermally removing harmful substances from the process gas, for example a CVD process or a dry etching process.

[0039] It is conceivable that information about the composition of the process gas can be obtained by means of a unit connected between the preceding machining process and the combustion process, which information can be used for the gas flow control device. In other words, specific sensitive information about the preceding process can be processed and filtered in the intermediate unit and summarized into overall information about the process gas.

[0040] For example, in the case of process waste gas CF 4 , the flow of dilution gas, for example nitrogen, into the combustion gas can be significantly reduced.

[0041] In the case where the process waste gas does not contain CF4, a dilution gas inflow, such as a nitrogen flow rate, calculated by a regulating device or a control device of the equipment can be added.

[0042] The calculation of the dilution gas inflow can be carried out with the aid of predefined empirically determined parameters and information obtained from the signal.

[0043] The combustion gas flow through the burner can also be adjusted based on information or signals from the preceding process. The signal can have information about the current flow of inert gas, in particular N2, contained in the process exhaust gas.

[0044] The flow rate of oxygen through the burner can be adjusted to a predetermined ratio with the combustion gas. The ratio of the oxygen flow rate to the combustion gas flow rate can be selected based on a signal having information about the composition of the process exhaust gas.

[0045] According to an advantageous further development of the invention, the inflow of dilution gas is reduced, in particular to below a predetermined or predeterminable value, when the process gas contains carbon tetrafluoride (CF 4 ).

[0046] This value can be selected such that, when the process gas contains carbon tetrafluoride (CF4), the inflow of dilution gas is a maximum of 1% of the volume flow of the combustion gas.

[0047] In the case of process gases that do not contain climate-damaging pollutants, in particular fluorocarbons such as carbon tetrafluoride (CF4), hexafluoroethane (C2F6) and / or sulfur hexafluoride (SF6), the dilution gas can also be fed to the combustion gas in a controlled manner at a value exceeding 1% of the volume flow of the combustion gas. The flow rate of the dilution gas can also be more than 100% of the volume flow of the combustion gas.

[0048] According to a further advantageous embodiment of the invention, an additional oxidizing agent, for example air or oxygen, is introduced into the combustion chamber in a controlled manner depending on the chemical composition of the process gas.

[0049] Even if the burner allows a variation of the combustion gas / oxygen ratio, for certain processes it may be necessary to additionally feed an oxidizing agent, such as air or oxygen, or a reducing agent, such as combustion gas, into the reactor spatially separate from the burner.

[0050] In order to treat waste gas mixtures from preceding processes which contain large amounts of combustible gases, an additional flow of an oxidant, such as air or oxygen, can be added to the combustion reactor.

[0051] This oxidant is not conducted through the burner, but nevertheless also influences the nitrogen oxide production. In order to minimize the nitrogen oxide production, it is therefore advantageous to also use information or signals from the preceding process which indicate the need for additional oxidant in the reactor, so that only the required amount of additional oxidant is always supplied in the variable exhaust gas mixture.

[0052] Similarly, when treating exhaust gas mixtures containing large amounts of oxidizing gases, such as oxygen, fluorine or also N 2 O, the reducing agent can be supplied spatially separated from the burner. The reducing agent can be, for example, combustion gas or also hydrogen.

[0053] The independent concept of the present invention relates to a burner for generating a flame in a combustion chamber to burn harmful substances in a process gas, the burner having: a supply line for combustion gas and a supply line for oxygen, each for flowing into the combustion chamber, and an ignition device for igniting the mixed gas in the combustion chamber.

[0054] According to the invention, a further supply line is provided for mixing a dilution gas, preferably an inert gas, such as nitrogen, into the combustion gas, wherein the further supply line for the dilution gas opens into the supply line for the combustion gas.

[0055] The ignition device can be used for generating sparks or hot surfaces in the burner. However, additional ignition burners on the combustion chamber are also conceivable.

[0056] According to a first advantageous embodiment of the burner according to the invention, for dynamic adjustment of the gas composition, the gas flow of the dilution gas in the further supply line can be adjusted by means of a control device assigned to the further supply line as a function of the composition of the process gas to be treated.

[0057] According to a further embodiment of the burner, the supply lines each have a regulating device and / or a shut-off device for regulating and / or shutting off the respective gas flow.

[0058] According to another independent concept of the present invention, a waste gas treatment equipment is set up, which has: at least one burner arranged on the combustion chamber for generating a flame to burn harmful substances in the process gas; at least one supply device for the process gas; and at least one discharge device for the heat-treated waste gas.

[0059] At least one supply line can be provided for a reaction gas, in particular an oxidizing agent and / or a reducing agent.

[0060] According to an advantageous variant, the liquid supply device can be arranged in particular on a side wall of the combustion chamber, which liquid supply device, by conveying liquid, achieves on the one hand protection against corrosion or deposits on the side wall and on the other hand cooling of the wall.

[0061] In order to protect the harmful gas inlet from liquid splashing, a small flange can be arranged on the side wall before the liquid supply. The cover of the reactor can be double-walled for improved thermal insulation. The increased surface temperature on the inside of the cover reduces the probability of solid adhesion. A purge gas, for example nitrogen, can be fed through the double-walled cover and blown into the end of the harmful gas supply through the porous sintered body to remove particles.

[0062] Advantageously, a regulating device can be provided for regulating and / or controlling the flow rate through the supply line for the combustion gas and / or for the oxygen and / or for the dilution gas.

[0063] In particular, a control device can be provided in the exhaust gas treatment system, which is connected to a regulating device for regulating and / or controlling the flow through the supply lines for combustion gas and / or for oxygen and / or for dilution gas. The control device can have a communication connection, via which information about the operating state of a process device connected upstream can be received.

[0064] Further purposes, advantages, features and application possibilities of the present invention are apparent from the following description of the exemplary embodiments with the aid of the accompanying drawings. All described and / or illustrated features also constitute the subject matter of the present invention, either by themselves or in any meaningful combination, regardless of their combination in the claims or in the references thereto. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] This is partially schematically shown here:

[0066] Figure 1 A burner is shown with a supply for oxygen, combustion gas and dilution gas, a combustion chamber, a supply for process gas and a supply line for reaction gas,

[0067] Figure 2 Shown according to Figure 1 The exhaust gas treatment equipment of the burner, and

[0068] Figure 3 A process system is shown which has three process chambers, each with a vacuum pump, a signal transmission unit and an exhaust gas treatment system with a gas sensor.

[0069] Identical or identically acting components are provided with the same reference numerals in the following views of the drawings according to one embodiment in order to improve readability. DETAILED DESCRIPTION

[0070] exist Figure 1 1 shows a burner 1 for generating a flame 2 in a combustion chamber 19 for burning harmful substances in a process gas. The burner 1 has a supply line 3 for combustion gas and a supply line 4 for oxygen, each for flowing into the combustion chamber 19 or into a premixing chamber 6 of the combustion chamber 19.

[0071] Depend on Figure 1 An ignition device 7 is also known for igniting the gas mixture present in the combustion chamber 19 or in the premixing chamber 6 .

[0072] according to Figure 1 , combustion gas and oxygen are introduced into the premixing chamber 6 of the burner 1 in each substantially cylindrical tube 16, 17. The cylindrical tubes 16, 17 are designed as an outer tube 16 and an inner tube 17 which are concentric with each other, wherein the outer tube 16 and the inner tube 17 are arranged radially spaced apart from each other. Depending on the application, the combustion gas can be introduced into the outer tube 16 or the inner tube 17 and the oxidant can be introduced into the outer tube 16 or the inner tube 17 accordingly.

[0073] A further supply line 5 is provided for mixing a dilution gas, preferably an inert gas, such as nitrogen, into the combustion gas. Figure 1As can be seen further, a further supply line 5 for dilution gas opens into the supply line 3 for combustion gas.

[0074] In the method for thermally removing pollutants from a process gas according to the invention, combustion gas and oxygen are introduced into a combustion chamber 19 of a burner 1 and ignited there in order to generate a flame for burning the pollutants. A dilution gas is introduced in order to reduce the combustion value of the mixed gas compared to the combustion gas, and the gas flow rate of the dilution gas is adjusted according to the composition of the process gas in order to adjust the mixed gas composed of the dilution gas and the combustion gas.

[0075] For this purpose, the supply lines 3 , 4 , 5 each have a regulating device 8 , 9 , 10 and / or a shutoff device 13 , 14 , 15 for regulating and / or shutting off the corresponding gas flow. The regulating devices 8 , 9 , 10 can be controlled by a control device 23 .

[0076] For dynamic adjustment of the gas composition, the gas flow of the dilution gas in the further supply line 5 can be adjusted in the manner described by means of the control device 10 assigned to the further supply line 5 as a function of the composition of the process gas to be processed.

[0077] A dilution gas can be mixed into the combustion gas before introduction into the combustion chamber 19 .

[0078] The dilution gas may be mixed into the combustion gas before a flame is generated to burn the harmful substances and / or before the combustion gas is mixed with oxygen.

[0079] The method can be used in particular for catalytic burners, in which combustion gas or diluted combustion gas is introduced separately from oxygen into the combustion chamber 19 or into the premixing chamber 6 and the two gas flows can be brought together only immediately prior to the reaction.

[0080] The diluent gas may be an inert gas. Nitrogen is usually used as an inert gas. However, any other gas or gas mixture that does not form a reactive mixture with the combustion gas may also be used.

[0081] In particular, the gas quantity of oxygen and / or combustion gas flowing into the combustion chamber 19 and / or the gas quantity of dilution gas admixed with the combustion gas can be adjusted individually.

[0082] It is conceivable to introduce an additional oxidizing agent, for example air or oxygen, into the combustion chamber 19 in a controlled manner depending on the chemical composition of the process gas.

[0083] Information about the composition of the process gas can be transmitted to the gas flow regulating devices 8, 9, 10 for the combustion gas, oxygen and / or dilution gas via the control device 23. The combustion gas composition is dynamically adjusted by the gas flow regulating devices based on the information.

[0084] Information about the composition of the process gas can be derived from the operating state of a process preceding the method for thermally removing pollutants from the process gas. As explained, information from the preceding process plant is transmitted to the control device (23) via a communication connection (30) for this purpose. In the control device (23), favorable values ​​for combustion gas, oxygen and dilution gas are derived therefrom and set via regulating devices (8, 9, 10).

[0085] According to this embodiment, when the process gas contains carbon tetrafluoride (CF4), the inflow of dilution gas is reduced, in particular to below a predetermined or predeterminable value. In this case, the inflow of dilution gas can be a maximum of 1% of the volume flow of the combustion gas.

[0086] This conditioning of the process waste gas is explained in more detail further below.

[0087] according to Figure 1 The burner is used in the exhaust gas treatment device (A) 18 in this embodiment.

[0088] Depend on Figure 2 Such an exhaust gas treatment system (A) 18 is known which has at least one burner 1 arranged on a combustion chamber 19 for generating a flame 2 for burning pollutants in a process gas.

[0089] The exhaust gas treatment system (A) 18 has at least one supply device 20 for process gas and at least one discharge device 21 for thermally treated exhaust gas.

[0090] Furthermore, in the present exemplary embodiment, a supply line 11 for a reaction gas, in particular an oxidizing agent and / or a reducing agent, is provided on the exhaust gas treatment device 18 . The inflow of the reaction gas can be regulated by means of a regulating device 12 .

[0091] Furthermore, in the present embodiment, the liquid supply device 22 is disposed on the side wall of the combustion chamber 19 .

[0092] According to Figure 2 The view of also shows the control device 23 and the regulating devices 8, 9, 10, which are used to regulate and / or control the flow through the supply lines 3, 4, 5 for combustion gas and / or for oxygen and / or for dilution gas. The blocking devices 13, 14, 15 can also be seen there.

[0093] In the process for processing silicon wafers, the gases CF4 (carbon tetrafluoride), SF6 (sulfur hexafluoride) and NF3 (nitrogen trifluoride) are also used in the process equipment (T) 26, which can be supplied to the process via a process gas supply device 27. The gases can be used simultaneously or also successively.

[0094] according to Figure 3 , the process equipment (T) 26 has, for example, three process chambers (C1, C2 and C3), each of which is indicated by reference numeral 28. The process exhaust gas is sucked out of the process chambers (C1, C2 and C3) 28 by vacuum pumps (P1, P2 and P3) indicated by reference numeral 29 and conveyed to the exhaust gas treatment equipment (A) 18. For technical reasons, a nitrogen flow is continuously added to the vacuum pumps (P1, P2 and P3) 29, in which the gas to be purged is then present in a diluted state.

[0095] Signals SP1, SP2 and SP3 are transmitted from the process device (T) 26 to the exhaust gas treatment device (A) 18 via the signal transmission unit (SI) 24, which signals indicate through which vacuum pump (P1, P2, P3) 29 the gas to be cleaned flows. The exhaust gas treatment device (A) 18 has a valve 31, through which the process exhaust gas can be directed to the combustion chamber 19 or to the exhaust line without being treated, depending on the signals SP1, SP2, SP3.

[0096] When the flow rate of nitrogen from the vacuum pump (P1, P2, P3) 29 is fixedly set and known, the current total flow rate FRN2 of nitrogen flowing into the burner 1 can be derived from the signals SP1, SP2, SP3. It is also possible that the vacuum pump (P1, P2, P3) 29 is also connected to the signal transmission unit (SI) 24 and the current flow rate FRN2 of nitrogen from the pump (P1, P2, P3) 29 is transmitted as a value to the signal transmission unit. The signal transmission unit (SI) 24 can then calculate the sum of all nitrogen flows and transmit the sum as the value FRN2 to the exhaust gas treatment device (A) 18 via the communication connection device 30.

[0097] When the signal SP1 , SP2 , SP3 indicates that there is no process waste gas to be disposed of, the burner 1 can also be set to a predefined state with minimum consumption or be completely shut down.

[0098] The process device (T) 26 is informed by further signals FCF4 - 1 , FCF4 - 2 and FCF4 - 3 whether CF 4 is contained in the process exhaust gas from the process chamber ( C1 , C2 , C3 ) 28 .

[0099] The process device (T) 26 is informed by further signals FSF6 - 1 , FSF6 - 2 and FSF6 - 3 whether SF 6 is contained in the process exhaust gas from the process chamber ( C1 , C2 , C3 ) 28 .

[0100] The required combustion gas flow FBG is obtained in the control device 23 by means of the flow FRN2 of nitrogen into the combustion chamber 19 and the signals FCF4-1, FCF4-2, FCF4-3 and FSF6-1, FSF6-2, FSF6-3. This can be achieved, for example, by calculation according to the following formula:

[0101] FBG=a*FRN2+b.

[0102] Here, a and b are predetermined empirically derived parameters.

[0103] The values ​​of parameter a and parameter b also depend on whether the process waste gas contains CF4 or SF6 or both.

[0104] When signals FCF4-1, FCF4-2, FCF4-3 indicate the presence of CF4, value A1 is selected for a. When no signal indicates the presence of CF4, but one of signals FSF6-1, FSF6-2, FSF6-3 indicates the presence of SF6, value A2 is selected for a.

[0105] When there is no signal indicating the presence of CF4 or SF6, then factor A3 is selected. Here, factors A1>A2>A3. Similar logic can be used for parameter b.

[0106] The method achieves that when CF4 is contained in the process off-gas, more combustion gas is used than when SF6 or only NF3 is contained.

[0107] The flow rate of oxygen FBO passing through the burner 1 is calculated in proportion to the combustion gas flow rate FBG according to the following formula:

[0108] FBO=c*FBG+d,

[0109] Parameters c and d may be fixedly predetermined or, similar to a and b, may be selected from a predetermined table based on the signals of CF4 and SF6.

[0110] In applications where the process gas contains oxidized or reduced pollutants, the stoichiometry of the burner can be influenced in dependence on the type and flow rate of the pollutant by selecting the parameters c and d. For this purpose, further signals can be defined and transmitted which indicate the presence of the substance and / or also the flow rate of the substance.

[0111] According to the invention, an adjustable flow rate FBN of nitrogen is additionally admixed to the combustion gas upstream of the burner 1. This flow rate is calculated, for example, according to the following formula:

[0112] FBN=e*FBG+f,

[0113] When one of the signals FCF4-1, FCF4-2, FCF4-3 indicates the presence of CF4, the parameters e=0 and f=0 are selected, so that FBN=0. Otherwise, fixed predetermined values ​​can be used for e and f, or the values ​​can be selected from an empirically derived relationship based on the signals FSF6-1, FSF6-2, FSF6-3 and the value FRN2.

[0114] The empirically determined relationship is selected such that the harmful process gases contained in the process exhaust gas are destroyed just at the required efficiency, for example >95%, while the formation of nitrogen oxides is minimal.

[0115] When the burner 1 is completely shut down, it is advantageous to set a predetermined value of the nitrogen flow FBN>0 in order to thereby ensure a purging of the burner which prevents the ingress of dust or moisture.

[0116] Furthermore, for technical reasons it can be advantageous not to regulate the nitrogen flow FBN into the combustion gas exactly to 0, but rather to produce a minimum flow of nitrogen FBN for purging the line, wherein the minimum flow is selected so small, for example <0.5% of the combustion gas flow, that it does not significantly influence the properties of the flame.

[0117] The following method is also possible, in which, by means of a signal from the process device (T) 26 or from the signal transmission unit (SI) 24, not only the presence of a certain process gas or the presence of another gas added after the process device (T) 26 is displayed, but also their flow rate. This information allows a more accurate regulation of the burner 1 and the reaction gas and also improves other functions of the device, such as the regulation of the subsequent alkaline exhaust gas scrubbing. Thus, for example, the flow of combustible process gas or harmful substances can be transmitted in order to calculate the required amount of additional oxidant and regulate the flow of the oxidant through the supply line 11 for the reaction gas. The accurate regulation of the reaction gas according to the current process gas flow in the process device allows the generation of nitrogen oxides and carbon monoxide to be reduced to a minimum. By regulating the gas flow to the minimum flow required for the removal of harmful substances, the energy consumption can also be reduced to a minimum.

[0118] By means of a gas sensor (GS) 25 in the cleaned gas after the exhaust gas treatment device (A) 18, for example, the concentration of carbon monoxide or nitrogen oxides can be monitored to ensure that the regulation of the gas flow through the burner 1 and the regulation of the reaction gas achieve the desired effect of complete combustion and low nitrogen oxide emissions. The gas sensor (GS) 25 can also be used to continuously detect particularly harmful substances in the cleaned gas to ensure that the exhaust gas treatment device (A) 18 is sufficiently cleaned of these harmful substances in all operating states.

[0119] Reference numerals list

[0120] 1 Burner

[0121] 2 Flame

[0122] 3 Supply line for combustion gas

[0123] 4 Supply line for oxygen

[0124] 5 Additional supply line for dilution gas

[0125] 6 Premixing room

[0126] 7 Ignition Device

[0127] 8 Regulating device for combustion gases

[0128] 9 Regulator for oxygen

[0129] 10Regulator for inert gas

[0130] 11 Supply pipeline for reaction gas

[0131] 12Regulator for reaction gas

[0132] 13 Shut-off device for combustion gas

[0133] 14. Oxygen blocking device

[0134] 15Shut-off device for inert gas

[0135] 16 Outer tube

[0136] 17 Inner tube

[0137] 18 Waste gas treatment equipment (A)

[0138] 19 Combustion Chamber

[0139] 20 Supplying process gases

[0140] 21 Exhaust gas from the device

[0141] 22 Liquid supply device

[0142] 23 Control Device

[0143] 24Signal Transmission Unit (SI)

[0144] 25 Gas Sensor (GS)

[0145] 26 Process equipment (T)

[0146] 27Process gas supply device

[0147] 28 process rooms (C1, C2, C3)

[0148] 29 Vacuum pump (P1, P2, P3)

[0149] 30 Communication connection device

[0150] 31 Valve

[0151] FRN2 Nitrogen flow

[0152] FBG combustion gas flow

[0153] FBO oxygen flow

[0154] FBN Additional nitrogen flow

[0155] SP1 Signal from process equipment

[0156] SP2 Signals from process equipment

[0157] SP3 Signals from process equipment

[0158] FCF4-1 Signal from process equipment T

[0159] FCF4-2 Signal from process equipment T

[0160] FCF4-3 Signal from process equipment T

[0161] FSF6-1 Signal from process equipment T

[0162] FSF6-2 Signal from process equipment T

[0163] FSF6-3 Signal from process equipment T

[0164] a, b, c parameters

[0165] d, e, f parameters

[0166] A1, A2 values

[0167] A3 value.

Claims

1. A method for thermally removing harmful substances from a process gas, wherein: In order to generate a flame for burning harmful substances, combustion gas and oxygen are introduced into a combustion chamber (19) of a burner (1) and ignited there, wherein, in order to reduce the combustion value of the mixed gas compared to the combustion gas, a dilution gas in the form of an inert gas is mixed into the combustion gas before introduction into the combustion chamber (19), and in order to adjust the mixed gas consisting of the dilution gas and the combustion gas, the gas flow rate of the dilution gas is adjusted depending on the composition of the process gas.

2. The method according to claim 1, characterized in that The dilution gas is mixed into the combustion gas before a flame is generated to burn harmful substances and / or before the combustion gas is mixed with the oxygen.

3. The method according to any one of claims 1 to 2, characterized in that The amount of oxygen and / or the combustion gas flowing into the combustion chamber (19) and / or the amount of dilution gas mixed into the combustion gas are individually adjusted.

4. The method according to claim 1 or 2, characterized in that: Information about the composition of the process gas is transmitted to a regulating device for the gas flow rates of combustion gas, oxygen and / or dilution gas, and the combustion gas composition is dynamically adjusted by the regulating device for the gas flow rates according to the information.

5. The method according to claim 4, characterized in that The information about the composition of the process gas is derived from the operating conditions of a process preceding the method for thermally removing pollutants from the process gas.

6. The method according to claim 1 or 2, characterized in that: When the process gas contains carbon tetrafluoride (CF4), the inflow amount of the dilution gas is reduced.

7. The method according to claim 6, characterized in that When the process gas contains carbon tetrafluoride (CF4), the inflow amount of the dilution gas is at most 1% of the volume flow rate of the combustion gas.

8. The method according to claim 1 or 2, characterized in that: An additional oxidant is introduced into the combustion chamber (19) in a controlled manner depending on the chemical composition of the process gas.

9. The method according to claim 6, characterized in that When the process gas contains carbon tetrafluoride (CF 4 ), the inflow amount of the dilution gas is reduced to a value below a predetermined or predeterminable value.

10. The method according to claim 8, characterized in that The additional oxidant is air or oxygen.

11. The method according to claim 1 or 2, characterized in that: The process gas is supplied to the combustion chamber (9) via a supply line (20) and the reaction gas is supplied via a separate supply line (11).

12. A burner (1) for generating a flame (2) in a combustion chamber (19) to burn harmful substances in a process gas, the burner comprising: a supply line (3) for combustion gas and a supply line (4) for oxygen, each for flowing into the combustion chamber (19); and an ignition device (7) for igniting the mixed gas in the combustion chamber (19), characterized in that: A further supply line (5) is provided for mixing a dilution gas in the form of an inert gas into the combustion gas, wherein the further supply line (5) for the dilution gas opens into the supply line (3) for the combustion gas, wherein the supply line (3) opens into an inner tube (17) of a premixing chamber (6) upstream of the combustion chamber (19), and the supply line (4) for oxygen opens into an outer tube (16) of the premixing chamber.

13. The burner (1) according to claim 12, characterized in that In order to dynamically adjust the gas composition, the gas flow of the dilution gas in the further supply line (5) can be adjusted by means of a control device (10) assigned to the further supply line (5) depending on the composition of the process gas to be processed.

14. The burner (1) according to claim 12 or 13, characterized in that The supply lines (3, 4, 5) each have a regulating device (8, 9, 10) and / or a shutoff device (13, 14, 15) for regulating and / or shutting off the corresponding gas flow.

15. The burner (1) according to claim 12 or 13, characterized in that The combustion chamber (9) has a supply line (20) for the process gas and a separate supply line (11) for the reaction gas.

16. A waste gas treatment device (18), comprising: at least one burner (1) arranged on a combustion chamber (19) for generating a flame (2) to burn harmful substances in a process gas, according to any one of the preceding claims 12 to 15; at least one supply device (20) for the process gas; and at least one discharge device (21) for the heat-treated waste gas.

17. The exhaust gas treatment device (18) according to claim 16, characterized in that At least one supply line (11) is provided for the reaction gas.

18. The exhaust gas treatment device (18) according to claim 16 or 17, characterized in that: A liquid supply device (22) is provided.

19. The exhaust gas treatment device (18) according to claim 16 or 17, characterized in that: Regulating devices (8, 9, 10) are provided for regulating and / or controlling the flow through the supply lines (3, 4, 5) for the combustion gas and / or for the oxygen and / or for the dilution gas.

20. The exhaust gas treatment device (18) according to claim 16, characterized in that At least one supply line (11) is provided for an oxidizing agent and / or a reducing agent.

21. The exhaust gas treatment device (18) according to claim 18, characterized in that: The liquid supply device (22) is arranged on a side wall of the combustion chamber (19).

22. The exhaust gas treatment device (18) according to claim 19, characterized in that The regulating device is connected to a control device (23) for controlling the regulating device (8, 9, 10).

23. Use of a burner (1) according to any one of claims 12 to 15 in a method for thermally removing pollutants from a process gas.

Images