Process and Burner for the Thermal Disposal of Pollutants in Process Gases

Abstract

The invention relates to a method for the thermal disposal of pollutants in industrial gases, wherein, in order to generate a flame for burning the pollutants, a fuel gas and oxygen are fed into a combustion chamber (19) of a burner (1), where they are then ignited, wherein a diluent gas is fed in in order to reduce the calorific value of the gas mixture relative to the fuel gas, while the throughput of the diluent gas is regulated as a function of the composition of the industrial gas in order to adapt the gas mixture consisting of diluent gas and fuel gas. The invention also relates to a burner (1) for generating a flame (2) in a combustion chamber (19) for burning pollutants in an industrial gas, and to a waste-gas treatment device having at least one burner (1) arranged in a combustion chamber (19).

Claims

1. A method for the thermal disposal of pollutants in an industrial gas, comprising: feeding the industrial gas into a combustion chamber (19) of a burner (1); feeding a fuel gas and oxygen into the combustion chamber (19) of the burner (1); feeding a diluent gas into the combustion chamber (19) in order to reduce the calorific value of the gas mixture consisting of diluent gas and fuel gas relative to the calorific value of the fuel gas; regulating throughput of the diluent gas as a function of the composition of the industrial gas in order to adapt the gas mixture consisting of diluent gas and fuel gas; and igniting the fuel gas and oxygen in order to generate a flame for burning the pollutants.

2. The method according to claim 1, wherein the diluent gas is admixed with the fuel gas before introduction into the combustion chamber (19).

3. The method according to claim 2, wherein the admixture of the diluent gas with the fuel gas takes place before a flame is generated for burning the pollutants and before the fuel gas is mixed with the oxygen.

4. The method according to claim 1, wherein the diluent gas is an inert gas.

5. The method according to claim 1, wherein volumes of the fuel gas, the oxygen and the diluent gas or volumes of the oxygen and an admixture of diluent gas and fuel gas flowing into the combustion chamber (19) are separately regulated.

6. The method according to claim 1 wherein volume(s) introduced into the combustion chamber of one or more of the fuel gas, the oxygen and/or the diluent gas, is/are dynamically regulated based on throughput and composition of the industrial gas introduced into the combustion chamber.

7. The method according to claim 6, wherein composition of the industrial gas is ascertained from operating states of a process that generated the industrial gas.

8. The method according to claim 1, wherein, if the industrial gas contains tetrafluoromethane (CF.sub.4), the feed of the diluent gas is reduced, substantially discontinued or entirely discontinued.

9. The method according to claim 8, wherein, if the industrial gas contains tetrafluoromethane (CF.sub.4), diluent gas is fed at an amount of 1% or less of the volumetric flow of the fuel gas.

10. The method according to claim 1, further comprising feeding an additional oxidant such as air or oxygen a regulated manner into the combustion chamber (19) as a function of the chemical composition of the industrial gas.

11. A burner (1) for generating a flame (2) in a combustion chamber (19) for burning pollutants in an industrial gas, comprising: a feed line (3) for a fuel gas to be fed into the combustion chamber (19); a feed line (4) for oxygen to be fed into the combustion chamber (19); an ignition apparatus (7) for igniting the gas mixture present in the combustion chamber (19); and another feed line (5) for admixing a diluent gas into the fuel gas, wherein the additional feed line (5) for the diluent gas opens up in the feed line (3) for the fuel gas.

12. The burner (1) according to claim 11, further comprising a regulation means (10) associated with the additional feed line (5), said regulation means (10) configured to regulate gas throughput of the diluent gas in the additional feed line (5) to attain a dynamic adaptation of the gas composition as a function of the composition of the industrial gas that is to be processed in the burner.

13. The burner (1) according to claim 11, wherein the feed lines (3, 4, 5) each have a regulation means (8, 9, 10) and/or a blocking means (13, 14, 15) for regulating and/or blocking gas throughput.

14. A waste-gas treatment device (18), comprising: at least one burner (1) arranged in a combustion chamber (19), for generating a flame (2) to burn pollutants in an industrial gas according to claim 11; at least one feeding means (20) for feeding the industrial gas into the combustion chamber; and at least one discharge means (21) for discharging thermally treated waste gases from the combustion chamber.

15. The waste-gas treatment device (18) according to claim 14, further comprising at least one feed line (11) for a reaction gas selected from the group consisting of: an oxidant, a reducing agent, and a mixture of oxidant(s) and reducing agent(s).

16. The waste-gas treatment device (18) according to claim 14, further comprising liquid feed lines (22) on the side wall of the combustion chamber (19).

17. The waste-gas treatment device (18) according to claim 14, further comprising regulation means (8, 9, 10) to regulate and/or control the throughput through the feed lines (3, 4, 5) for the fuel gas and/or for the oxygen and/or for the diluent gas, wherein said regulation means are connected to a control unit (23) that serves to control the regulation means (8, 9, 10).

18. A method for burning off pollutants entrained in an industrial gas, comprising: feeding the industrial gas into a combustion chamber of a burner; mixing a diluent gas with a fuel gas to form a gas mixture, wherein said diluent gas reduces calorific value of the gas mixture relative to the calorific value of the fuel gas alone, and wherein throughput of the diluent gas as a function of the composition of the industrial gas is regulated in order to adapt the gas mixture to a predetermined calorific value to burn off the pollutants in the industrial gas; feeding the gas mixture into the combustion chamber; igniting the fuel gas in order to generate a flame for burning the pollutants.

Description

DESCRIPTION OF THE DRAWINGS

[0065] The In this context, the following is shown, at times schematically:

[0066] FIG. 1 a burner comprising feeds for oxygen, fuel gas and diluent gas, having a combustion chamber with a feeding means for industrial gas and with a feed line for reaction gas,

[0067] FIG. 2 a waste-gas treatment device having a burner according to FIG. 1, and

[0068] FIG. 3 a process installation with three processing chambers, each having a vacuum pump, a signal transmission unit and a waste-gas treatment device with a gas sensor.

[0069] For the sake of clarity, identical components or those having the same effect are provided with the same reference numerals in the figures of the drawings shown below, making reference to an embodiment.

DETAILED DESCRIPTION

[0070] FIG. 1 shows a burner 1 for generating a flame 2 in a combustion chamber 19 for burning pollutants in an industrial gas. The burner 1 has a feed line 3 for a fuel gas and a feed line 4 for oxygen, each to be fed into the combustion chamber 19 or into a premixing chamber 6 of the combustion chamber 19.

[0071] FIG. 1 also shows an ignition apparatus 7 for igniting the gas mixture present in the combustion chamber 19 or in the premixing chamber 6.

[0072] According to FIG. 1, the fuel gas and the oxygen are each fed into the premixing chamber 6 of the burner 1 in an essentially cylindrical pipe 16, 17. The cylindrical pipes 16, 17 are configured as an outer pipe 16 and an inner pipe 17 that are concentrical to each other, wherein the outer pipe 16 and the inner pipe 17 are arranged at a radial distance from each other. Depending on the application, the fuel gas can be conveyed in the outer pipe 16 or in the inner pipe 17, with the oxidant then being correspondingly conveyed in the outer pipe 16 or in the inner pipe 17.

[0073] Another feed line 5 is provided for admixing a diluent gas, preferably an inert gas, for instance, nitrogen, into the fuel gas. As can also be seen in FIG. 1, the additional feed line 5 for the diluent gas opens up in the feed line 3 for the fuel gas,

[0074] Within the scope of the method according to the invention for the thermal disposal of pollutants in industrial gases, in order to generate a flame for burning the pollutants, a fuel gas and oxygen are introduced into a combustion chamber 19 of a burner 1, where they are then ignited. In order to reduce the calorific value of the gas mixture relative to the fuel gas, the diluent gas is fed in and the throughput of the diluent gas is regulated as a function of the composition of the industrial gas in order to adapt the gas mixture consisting of diluent gas and fuel gas.

[0075] For this purpose, the feed lines 3, 4, 5 each have a regulation means 8, 9, 10 and/or a blocking means 13, 14, 15 for regulating and/or blocking the appertaining gas throughput. These regulation means 8, 9, 10 can be actuated by a control unit 23.

[0076] In this manner, for purposes of a dynamic adaptation of the gas composition, the regulation means 10 associated with the additional feed line 5 is used to regulate the throughput of the diluent gas in the additional feed line 5 as a function of the composition of the industrial gas that is to be treated.

[0077] The diluent gas can be admixed to the fuel gas before being introduced into the combustion chamber 19.

[0078] The admixture of the diluent gas to the fuel gas can take place before the generation of a flame for burning the pollutants and/or before mixing the fuel gas with oxygen.

[0079] The method can especially be employed for diffusion burners wherein the fuel gas or the diluted fuel gas is fed into the combustion chamber 19 or into the pre-mixing chamber 6 separately from the oxygen, and both gas streams are only combined immediately prior to the reaction.

[0080] The diluent gas can be an inert gas. As a rule, nitrogen is available as inert gas. However, any other gas that does not form a reactive mixture with the fuel gas can also be used.

[0081] In particular, the volumes of oxygen and/or of fuel gas flowing into the combustion chamber 19 and/or the volumes of the diluent gas admixed to the fuel gas can be regulated separately.

[0082] It is conceivable for an additional oxidant such as, for instance, air or oxygen, to be introduced into the combustion chamber 19 in a regulated manner as a function of the chemical composition of the industrial gas.

[0083] The information about the composition of the industrial gas can be relayed via the control unit 23 to the regulation means 8, 9, 10 for the gas throughput for the fuel gas, for the oxygen and/or for the diluent gas. As a function of this information, the fuel gas composition is dynamically adapted by regulating the gas throughput.

[0084] This information about the composition of the industrial gas can be ascertained from operating states of a process that has preceded the method for thermally disposing of pollutants in industrial gases. As already mentioned, for this purpose, information from upstream process installations is transmitted via the communication connection (30) to the control unit (23). The thus-resultant advantageous values for the fuel gas, for the oxygen and for the diluent gas are ascertained in the control unit (23) and set via the regulation means (8, 9, 10).

[0085] According to the present embodiment, if the industrial gas contains tetrafluoromethane (CF.sub.4), the inflow of diluent gas is reduced, especially all the way to below a value that is or can be prescribed. In this case, the inflow of the diluent gas amounts to a maximum of 1 % of the volumetric flow of the fuel gas.

[0086] This regulation as a function of the industrial waste gas is explained in detail below.

[0087] In the present embodiment, the burner according to FIG. 1 is used in a waste-gas treatment device (A) 18.

[0088] FIG. 2 depicts such a waste-gas treatment device (A) 18, having at least one burner 1 arranged in a combustion chamber 19, in order to generate a flame 2 for burning pollutants in an industrial gas.

[0089] The waste-gas treatment device (A) 18 has at least one feeding means 20 for the industrial gas and having at least one discharge means 21 for the thermally treated waste gases.

[0090] Moreover, the present embodiment provides for a feed line 11 for a reaction gas, especially an oxidant and/or a reducing agent, on the waste-gas treatment device 18. The inflow of reaction gas can be regulated by means of a regulation means 12.

[0091] Moreover, the present embodiment provides for liquid feed lines 22, especially on the side wall of the combustion chamber 19.

[0092] The depiction according to FIG. 2 also shows the control unit 23 and the regulation means 8, 9, 10 for regulating and/or controlling the throughput through the feed lines 3, 4, 5 for the fuel gas and/or for the oxygen and/or for the diluent gas. The blocking means 13, 14, 15 can also be seen there.

[0093] When it comes to a process for treating silicon wafers, the gases CF.sub.4 (tetrafluoromethane), SF.sub.6 (sulfur hexafluoride) and NF.sub.3 (nitrogen trifluoride) among others, are employed in a process installation (T) 26, wherein said gases can be fed to the process via an industrial gas supply source 27. These gases can be used at the same time or else one after the other.

[0094] According to FIG. 3, the process installation (T) 26 has, for example, three processing chambers (C1, C2 and C3), each of which is designated by the reference numeral 28. The industrial waste gases are exhausted out of the processing chambers (C1, C2 and C3) 28 by means of vacuum pumps (P1, P2 and P3), designated by the reference numeral 29, and transported to the waste-gas treatment device (A) 18. For technical reasons, a permanent stream of nitrogen is fed into the vacuum pumps (P1, P2 and P3) 29, wherein the gases that are to be disposed of are present in diluted form in such a stream.

[0095] Signals SP1, SP2 and SP3 that indicate through which vacuum pump (P1, P2, P3) 29 the gas to be disposed of is flowing are transmitted by the process installation (T) 26 to the waste-gas treatment device (A) 18 via a signal transmission unit (SI) 24. The waste-gas treatment device (A) 18 has valves 31 via which, as a function of the signals SP1, SP2, SP3, the industrial waste gases can be deflected either into the combustion chamber 19 or else in untreated form into an exhaust-air line.

[0096] If the stream of nitrogen coming out of the vacuum pumps (P1, P2, P3) 29 has been non-adjustably set and is known, it is possible to ascertain on the basis of the signals SP1, SP2, SP3 the flow of nitrogen FRN.sub.2 that is momentarily flowing in total into the burner 1. It is likewise possible for the vacuum pumps (P1, P2, P3) 29 to be connected to the signal transmission unit (S1) 24 and to transmit to them, in the form of a value, the momentary stream of nitrogen FRN.sub.2 coming out of the pumps (P1, P2, P3) 29. The signal transmission unit (S1) 24 can then calculate the sum of all of the nitrogen streams and transmit them as a value FRN.sub.2 to the waste-gas treatment device (A) 18 via the communication connection 30.

[0097] If none of the signals SP1, SP2, SP3 indicates industrial waste gas to be disposed of, the burner 1 can be set at a prescribed state entailing minimum consumption or else it can be switched off altogether.

[0098] By means of additional signals FCF4-1, FCF4-2 and FCF4-3 from the process installation (T) 26, it is communicated whether CF.sub.4 is present in the industrial waste gas coming out of the processing chambers (C1, C2, C3) 28.

[0099] By means of additional signals FSF6-1, FSF6-2 and FSF6-3 from the process installation (T) 26, it is communicated whether SF.sub.6 is present in the industrial waste gas coming out of the processing chambers (C1, C2, C3) 28.

[0100] The control unit 23 determines the requisite fuel gas stream FBG on the basis of the ascertained stream of nitrogen FRN.sub.2 into the combustion chamber 19 and on the basis of the signals FCF4-1, FCF4-2, FCF4-3 and FSF6-1, FSF6-2 and FSF6-3. This can be done, for instance, through a calculation according to the formula

[00001]$\text{FBG}\text{=}\text{a}\times {\text{FRN}}_2+\text{b,}$

[0101] wherein a and b stand for prescribed parameters that have been ascertained empirically.

[0102] The values of the parameter a and also of the parameter b depend on whether the industrial waste gas contains CF.sub.4 or SF.sub.6 or else neither of them.

[0103] A value A1 is selected for a if one of the signals FCF4-1, FCF4-2, FCF4-3 indicates the presence of CF.sub.4. A value A2 is selected for a if none of the signals indicates the presence of CF.sub.4 but one of the signals FSF6-1, FSF6-2, FSF6-3 indicates the presence of SF.sub.6.

[0104] A factor A3 is selected if none of the signals indicates the presence of CF.sub.4 or SF.sub.6. In this context, the factor is A1 > A2 > A3. A similar logic can be employed for the parameter b.

[0105] If the industrial waste gas contains CF.sub.4, this method causes more fuel gas to be used than if it contains SF.sub.6 or only NF.sub.3.

[0106] The stream of oxygen FBO through the burner 1 is calculated proportionally to the fuel gas stream FBG according to the formula

[00002]$\text{FBO}\text{=}\text{c}\times \text{FBG}\text{+}\text{d,}$

[0107] wherein c and d stand for parameters that have been non-adjustably prescribed, or else, similarly to a and b, they can be selected from prescribed tables as a function of the signals for CF.sub.4 and SF.sub.6.

[0108] In applications where oxidizing or reducing pollutants are contained in the industrial gas, the stoichiometry of the burner can be influenced by selecting the parameters c and d as a function of the type and stream of the pollutants. For this purpose, additional signals can be defined and transmitted which indicate the presence of these substances and/or of their streams as well.

[0109] According to the invention, a regulatable stream of nitrogen FBN is admixed into the fuel gas upstream from the burner 1. This stream is calculated, for example, according to the formula

[00003]$\text{FBN}\text{=}\text{e}\times \text{FBG}\text{+}\text{f,}$

[0110] wherein the parameters e and f are both selected to be 0 so that FBN = 0 if one of the signals FCF4-1, FCF4-2, FCF4-3 indicates the presence of CF.sub.4. Otherwise, fixed prescribed values can be used for e and f, or else values are selected that are dependent on the signals FSF6-1, FSF6-2, FSF6-3 and on the value FRN.sub.2 stemming from empirically ascertained relationships.

[0111] These empirically ascertained relationships are selected in such a way that the harmful industrial gases contained in the industrial waste gas can still just about be destroyed with the requisite efficiency, for instance, to a level > 95%, while at the same time, however, the formation of nitrogen oxide is minimal.

[0112] At those times when the burner 1 is completely switched off, it is advantageous to set a prescribed value for the nitrogen stream FBN to be > 0 in order to ensure flushing of the burner, thus preventing the intrusion of dust or moisture.

[0113] For technical reasons, it might be also advantageous to not regulate the stream of nitrogen FBN into the fuel gas to exactly 0, but rather to retain a minimum flow of nitrogen FBN in order to flush the line, wherein the minimum flow is selected so low, for example, < 0.5% of the fuel gas stream, that the properties of the flame are not impacted upon to any considerable degree.

[0114] Likewise feasible are methods with which signals stemming from the process installation (T) 26 or from the signal transmission unit (SI) 24 not only indicate the presence of certain industrial gases or of other gases added downstream from the process installation (T) 26, but also their streams. Such information allows a more precise adaptation of the burner 1 and of the reaction gases, and also other functions of the installation such as, for example, the regulation of a subsequent alkaline waste-gas scrubbing can be improved. Thus, for instance, the streams of combustible industrial gases or pollutants can be transmitted so that on this basis, the demand for additional oxidant can be calculated and its flow through the feed line 11 for the reaction gas can be regulated. The precise adaptation of the reaction gases to the momentary industrial gas streams in the processing installation makes it possible to minimize the formation of nitrogen oxides and carbon monoxide. The regulation of the gas streams to the minimally required flows for disposing of the pollutants also makes it possible to minimize energy consumption.

[0115] Gas sensors (GS) 25 for the purified gas downstream from the waste-gas treatment device (A) 18 can serve to monitor, for instance, the concentration of carbon monoxide or nitrogen oxides in order to ensure that the regulation of the gas throughput through the burner 1 and the regulation of the reaction gases attain the desired effect of a complete combustion as well as low nitrogen oxide emissions. Gas sensors (GS) 25 can also be deployed for continuously detecting highly harmful substances in the purified gas in order to ensure that the waste-gas treatment device (A) 18 disposes of these pollutants to a sufficient degree in all operating states.

LIST OF REFERENCE NUMERALS

[0116] 1 burner [0117] 2 flame [0118] 3 feed line for the fuel gas [0119] 4 feed line for the oxygen [0120] 5 additional feed line for the diluent gas [0121] 6 premixing chamber [0122] 7 ignition apparatus [0123] 8 regulation means for the fuel gas [0124] 9 regulation means for the oxygen [0125] 10 regulation means for the inert gas [0126] 11 feed line for the for the reaction gas [0127] 12 regulation means for the reaction gas [0128] 13 blocking means for the fuel gas [0129] 14 blocking means for the oxygen [0130] 15 blocking means for the inert gas [0131] 16 outer pipe [0132] 17 inner pipe [0133] 18 waste-gas treatment device (A) [0134] 19 combustion chamber [0135] 20 feeding means for the industrial gas [0136] 21 discharge means for the waste gases [0137] 22 liquid feed lines [0138] 23 control unit [0139] 24 signal transmission unit (SI) [0140] 25 gas sensor (GS) [0141] 26 process installation (T) [0142] 27 industrial gas supply source [0143] 28 processing chamber (C1, C2, C3) [0144] 29 vacuum pump (P1, P2, P3) [0145] 30 communication connection [0146] 31 valve [0147] FRN.sub.2 nitrogen stream [0148] FBG fuel gas stream [0149] FBO oxygen stream [0150] FBN additional nitrogen stream [0151] SP1 signals stemming from the process installation [0152] SP2 signals stemming from the process installation [0153] SP3 signals stemming from the process installation [0154] FCF.sub.4-1 signals stemming from the process installation T [0155] FCF.sub.4-2 signals stemming from the process installation T [0156] FCF.sub.4-3 signals stemming from the process installation T [0157] FSF6-1 signals stemming from the process installation T [0158] FSF6-2 signals stemming from the process installation T [0159] FSF6-3 signals stemming from the process installation T [0160] a, b, c parameters [0161] d, e, f, parameters [0162] A1, A2 values [0163] A3 value