DE102021114836A1 - Conversion of sulphur-containing compounds in exhaust gases by non-thermal plasma - Google Patents

Abstract

The invention relates to an exhaust gas cleaning system 12 and a method for treating an exhaust gas flow 6 from a plant 1, for example an animal carcass processing plant. In this case, non-thermal plasma, which generates ozone and OH radicals in a plasma gas stream 7, is used to remove sulphur-containing target components (methyl mercaptan (CH4S), dimethyl sulfide (C2H6S), dimethyl disulphide (C2H6S2) and dimethyl trisulfide (C2H6S3)) in the exhaust gas stream 6 in a primary and a secondary reaction. The primary reaction takes place through the mere combination of exhaust gas and plasma gas flow. The secondary reaction can be accelerated by using a catalyst. This significantly reduces the concentration of the target components. As an alternative to using a catalyst, the target components and/or ozone can be further converted by an adsorbent. The second gas stream 9 generated in this way is particularly preferably post-treated in a gas scrubber 4 and/or a biofilter 5 .

Description

The subject of the application is a process for cleaning an exhaust gas flow, in which the concentration of a sulfur-containing compound such as methyl mercaptan (CH ₄ S), dimethyl sulfide (C ₂ H ₆ S), dimethyl disulfide (C ₂ H ₆ S ₂ ) and dimethyl trisulfide (C ₂ H ₆ S ₃ ) is reduced by treatment with a non-thermal plasma and a corresponding waste gas treatment system. The sulfur-containing compounds mentioned are referred to below as target components.

Exhaust gas cleaning systems are used in many countries to reduce odor pollution, for example in the vicinity of companies. These can be, for example, animal rendering plants, slaughterhouses, animal feed manufacturers, sewage sludge drying plants or tobacco factories that emit gases that are perceived as unpleasant on the one hand and have very low odor thresholds on the other, so that very low concentrations in the breathing air are sufficient to perceive them. In order to reduce the odor pollution from such exhaust gases, systems can be used in which the exhaust gas is passed through various treatment devices before it is released into the ambient air.

To date, such waste gases have primarily been treated by biofilters. In a biofilter, chemical compounds are converted by microorganisms. Depending on the purpose of the filter, special bacteria or fungi are used as microorganisms. The chemical compounds from the exhaust gases that are fed to the biofilter are reacted with oxygen and recombined into non-harmful compounds such as water and carbon dioxide, the odor of which is not perceived as unpleasant or which are odorless. Various organic products such as fibres, wood chips, root wood, granules or mixtures can serve as carriers for the microorganisms. The service life of a biofilter can vary greatly depending on the substances fed in, as these sometimes damage the microorganisms used.

Since the target components are gases that are toxic to many microorganisms, a biofilter is only partially suitable for converting these compounds. Conversion can take place initially, but the microorganisms are severely damaged by the target components, so that their lifespan is shortened and the biofilter has a reduced service life overall. In this respect, the mere treatment of such exhaust gases using biofilters is not economical.

Another known measure for treating exhaust gases containing at least one of the target components is the use of a gas scrubber. In a gas scrubber, the gas to be treated is combined with a scrubbing liquid, which can be water or water mixed with setting-promoting substances. Depending on the design of the gas scrubber, the gas can be sprayed with the liquid or the liquid and gas streams are guided past one another through a nozzle-shaped geometry in such a way that the gas stream hits the largest possible surface of the liquid.

A prerequisite for a high conversion rate, i.e. effective odor reduction, is high water solubility. This is not the case with the target components, so that post-treatment using only a gas scrubber can only achieve limited success in terms of reducing odor pollution.

The object of the present invention is therefore to at least partially overcome the disadvantages known from the prior art.

This object is solved by the features of the independent claims. The dependent claims are directed to advantageous developments.

According to the method according to the invention for cleaning an exhaust gas stream which contains at least one of the following target components methyl mercaptan (CH ₄ S), dimethyl sulfide (C ₂ H ₆ S), dimethyl disulphide (C ₂ H ₆ S ₂ ) and dimethyl trisulfide (C ₂ H ₆ S ₃ ) includes, the exhaust gas flow is supplied with a plasma gas flow, in which at least hydroxyl radicals and ozone are generated by a non-thermal plasma before being fed to the exhaust gas flow and the exhaust gas flow and plasma gas flow then mix to form a first gas flow, wherein within the first gas flow at least one of the target components reacts in a primary reaction with the hydroxyl radicals and in a secondary reaction with the ozone to form a secondary gas stream in which the concentration of at least one of the target components is compared to the concentration of the corresponding target -Component in the exhaust gas flow is reduced.

The exhaust gas flow can in particular be a gas flow which is withdrawn from an operation, for example, by an exhaust air system or an air exchange system. On the one hand, the exhaust gas flow contains air and thus parts, in particular of oxygen, nitrogen, carbon dioxide, etc., and on the other hand, other molecules that originate from the processes in the respective companies, such as esp separate one or more target components. As a rule, the concentration of the target components in the exhaust gas flow is between 10 and 1000 mg/m ³ .

In the method according to the invention, a non-thermal plasma is provided for the conversion of the target components. In the context of this document, the term non-thermal plasma is understood to mean, in particular, a plasma in which there is a thermal imbalance. The non-thermal plasma is preferably generated by a dielectric barrier discharge in a plasma generator. Contact with outside air produces, among other things, highly reactive hydroxyl radicals and ozone (O ₃ ). In the context of this document, outside air is understood to mean, in particular, fresh air that can be sucked in from the outside environment and is not polluted by gases and particles occurring during the production process.

• Für Methylmercaptan (CH₄S), Dimethyldisulfid (C₂H₆S₂) und Dimethyltrisulfid (C₂H₆S₃) kann die primäre Reaktion wie folgt dargestellt werden: R-S-H + OH^- → R-S^- + H₂O

mit R=CH₃ für Methylmercaptan, R= C₂H₅S für Dimethyldisulfid und R= C₂H₅S₂ für Dimethyltrisulfid. Für Dimethylsulfid (C₂H₆S) kann die primäre Reaktion dargestellt werden als H₃C-S-CH₃ + OH^- → H₃C-S-CH₂ ^- + H₂O. The term hydroxyl radicals is understood to mean a group comprising an oxygen and a hydrogen atom. A hydroxyl radical has the chemical formula OH ^- and carries a negative charge. The hydroxyl radical is highly reactive and reacts in a primary reaction with at least one of the target components, in particular according to the following reaction equations, as soon as the plasma gas flow is fed to the exhaust gas flow via a feed line and the gases have mixed at a mixing point:

• For methyl mercaptan (CH ₄ S), dimethyl disulfide (C ₂ H ₆ S ₂ ), and dimethyl trisulfide (C ₂ H ₆ S ₃ ), the primary reaction can be represented as follows: RSH + OH ^- → RS ^- ₊ H2O

with R=CH ₃ for methyl mercaptan, R= C ₂ H ₅ S for dimethyl disulfide and R= C ₂ H ₅ S ₂ for dimethyl trisulfide. For dimethyl sulfide (C ₂ H ₆ S), the primary reaction can be represented as H ₃ CS-CH ₃ + OH ^- → H ₃ CS-CH ₂ ^- + H ₂ O

The lifetime of the hydroxyl radicals is only a few milliseconds (0.05 ms [milliseconds] to 2 ms) depending on the concentration of the target components, so the primary reaction occurs immediately after the mixing of the plasma gas stream and the exhaust stream and after completed in just a few milliseconds.

A second component of the plasma gas stream is ozone (O ₃ ). In a secondary reaction, at least one of the target components reacts with the ozone. In the process, ozone is oxidized to O and O ₂ . As a result of this oxidation, the target components are converted into products whose water solubility is greater than that of the target components.

For methyl mercaptan (CH ₄ S), dimethyl disulfide (C ₂ H ₆ S ₂ ), and dimethyl trisulfide (C ₂ H ₆ S ₃ ), the secondary reaction can be represented as follows: R'-S + O ₃ → R'-SO + O ₂ ... →SO ₂ , H ₂ O, CO ₂

With R'= CH ₄ for methyl mercaptan, R'=C ₂ H ₆ S for dimethyl disulphide and R'= C ₂ H ₆ S ₂ for dimethyl trisulphide. As shown, the compounds R'-S react with oxygen to form sulfur dioxide, water and carbon dioxide. With dimethyl sulfide (C2H6S), the following secondary reaction takes place: H3 CS- _{CH2 +} O3 → H3 CS- _{CH2 -O + O2} ...→ _SO2 , _H2 O, _CO2

Here, too, the reaction product of the secondary reaction is further converted into nitrogen dioxide, water and carbon dioxide.

For effective conversion of the target components, a plasma gas flow is preferably provided, which preferably corresponds to between 2% and 20%, particularly preferably between 5% and 15%, in particular about 10%, of the mass flow of the exhaust gas flow and has an energy density of at least 1 kW per 1,000 m ³ , based on the exhaust gas flow. In this way, for example, a reduction in the concentration of the target component methyl mercaptan (CH4S) by at least 90% can be achieved.

According to an advantageous embodiment, the reaction rate for the secondary reaction is increased by a catalyst. A catalyst is a substance that, without being converted or degraded itself, reduces the activation energy for a chemical reaction and thus speeds up the course of the reaction.

According to this embodiment, this secondary reaction is made possible by providing a catalyst on a catalyst support. In the secondary reaction, ozone is oxidized into an oxygen radical (O) and oxygen (O ₂ ) with the aid of the catalyst in the catalyst carrier. The oxygen radical is bound to the catalyst and reacts with a molecule of a target component when this is guided past the oxygen radical.

The catalyst support is advantageously formed by a support body with a large surface area. This can be, for example, a ceramic honeycomb body that has porous walls and/or walls that can be flown through. The catalyst support contains the catalyst, for example in or on the walls of the carrier body and/or in a coating on the surface of the carrier body. The coating can produce a porous structure on the surface of the carrier body, which has a positive effect on the surface area available for reactions. In particular, a corresponding ceramic washcoat can be applied as a coating.

According to an advantageous embodiment, manganese oxide is provided as a catalyst. Manganese oxide is particularly suitable for the catalytic conversion of ozone and is already used for this in other technical contexts. The use of manganese(IV) oxide (MnO ₂ ) is particularly preferred.

According to an advantageous embodiment, the first gas stream flows through an adsorbent in which at least one of the target components reacts with ozone, so that the concentration of at least one of the target components and/or ozone in the second gas stream is reduced. The secondary reaction can take place effectively due to the microporous structure and thus large surface area of the adsorbent. At least one of the following substances is preferably used as the adsorbent: activated carbon, impregnated activated carbon, a zeolite and a silicalite are used. A zeolite is understood to mean, in particular, a crystalline aluminosilicate. In particular, a polymorphic form of silicon dioxide is understood as silicalite. The activated carbon is preferably impregnated with metal salts, in particular copper oxide, zinc oxide and/or potassium iodide.

Activated charcoal or impregnated activated charcoal has surprisingly proven to be particularly advantageous; this is inexpensive and readily available while at the same time efficiently reacting the target components with ozone on the activated charcoal. According to a further advantageous embodiment, the second gas flow is subjected to after-treatment by at least one of the after-treatment units biofilter and gas scrubber. After the primary and secondary reaction, the exhaust gas flow already has a significantly reduced concentration of at least one of the target components. In addition, there is an increased water solubility of the reaction products compared to the water solubility of the target components, so that the degree of separation can be improved with further treatment of the exhaust gas flow by traditional systems. Subsequent treatment with a gas scrubber and/or a biofilter can therefore have a positive effect on the reduction in concentration of the target components that can be achieved overall. In order to promote the gas flow towards the biofilter, the installation of a ventilator immediately in front of the biofilter is suggested. The remaining target components can be converted through the biofilter. After the reaction with the radicals generated by the plasma, their concentration is so low that damage to the biofilter by the target components is at least greatly slowed down and ideally even prevented. In particular, the biofilter acts as a police filter if, for example, the plasma generator fails.

According to a further advantageous embodiment, the second gas flow is first passed through the gas scrubber and then through the biofilter. In contrast to a gas scrubber, biofilters require regular replacement of the active microorganisms. The microorganisms are exposed to less stress if the gas flow is first passed through a gas scrubber, so that an increased service life of the biofilter can be expected with such an arrangement.

According to a further advantageous embodiment, the non-thermal plasma is generated by a dielectric barrier discharge. This is brought about in a plasma generator by applying high voltage to two electrodes, but preventing the formation of an arc between the electrodes and a discharge associated therewith by providing at least one of the electrodes with a dielectric barrier. Instead, charged particles collect on the surface of the barrier, which, together with the applied voltage field, ensure the formation of a non-thermal plasma between the electrodes. For this process, an AC voltage with a very high frequency (in particular several kilohertz) is applied.

• - eine Abgasleitung zur Führung eines Gasstroms, die im Betrieb in einer Durchströmungsrichtung durchströmbar ist,
• - eine Zuleitung mit einem Plasma-Generator, der von einem Luftstrom zur Bildung eines Plasma-Gasstroms durchströmbar ist, wobei durch den Plasma-Generator durch ein nichtthermisches Plasma Hydroxyl-Radikale und Ozon in diesem Plasma-Gasstrom erzeugbar sind, wobei die Zuleitung an einer Mischstelle mit der Abgasleitung zur Mischung des Abgasstroms und des Plasma-Gasstroms zu einem ersten Gasstrom verbunden ist.

According to a further aspect of the present invention, an exhaust gas cleaning system for cleaning an exhaust gas flow which comprises at least one of the following target components methyl mercaptan, dimethyl sulfide, dimethyl disulphide and dimethyl trisulfide is proposed for carrying out the method according to the invention. This procedure includes:

• - an exhaust pipe for conducting a gas flow, which can be flowed through in one flow direction during operation,
• - A supply line with a plasma generator through which an air flow can flow to form a plasma gas flow, wherein hydroxyl radicals and ozone can be generated in this plasma gas flow by the plasma generator through a non-thermal plasma, the supply line being connected to a Mixing point with the exhaust pipe for mixing the exhaust gas current and the plasma gas flow is connected to form a first gas flow.

According to an advantageous embodiment, the exhaust gas cleaning system comprises a catalyst carrier with a catalyst, which increases the reaction speed for the secondary reaction, downstream of the mixing point in the direction of flow.

According to a further advantageous embodiment, manganese oxide, in particular manganese(IV) oxide (MnO ₂ ), is provided as the catalyst in the catalyst support.

According to a further advantageous embodiment, the exhaust gas purification system comprises an adsorbent carrier with an adsorbent downstream of the mixing point in the flow direction, which reduces the concentration of at least one of the target components and/or ozone in the second gas stream.

According to a further advantageous embodiment, an exhaust gas cleaning system is provided in which at least one of the post-treatment units, biofilter and gas scrubber, is configured downstream of the catalyst support in the direction of flow.

According to a further advantageous embodiment, an exhaust gas purification system is provided which includes a gas scrubber and a biofilter and the biofilter is arranged downstream of the gas scrubber in the direction of flow.

According to a further advantageous embodiment, an exhaust gas cleaning system is provided with a plasma generator in which the non-thermal plasma can be generated by a dielectric barrier discharge.

The details and advantages disclosed for the method for cleaning an exhaust gas stream can be applied and transferred to the exhaust gas cleaning system and vice versa.

As a precaution, it should be noted that the numerals used here (“first”, “second”, ...) primarily (only) serve to distinguish between several similar objects, sizes or processes, i.e. in particular no dependency and/or sequence of these objects, sizes or make processes mandatory for each other. Should a dependency and/or order be necessary, this is explicitly stated here or it is obvious to the person skilled in the art when studying the specifically described embodiment.

• 1: schematisch ein erstes Beispiel einer Abgasreinigungsanlage;
• 2: schematisch ein weiteres Beispiel einer Abgasreinigungsanlage; und
• 3: schematisch ein weiteres Beispiel einer Abgasreinigungsanlage.

The invention and the technical environment are explained in more detail below with reference to the figures. It should be pointed out that the invention should not be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and to combine them with other components and findings from the present description and/or figures. In particular, it should be pointed out that the figures and in particular the proportions shown are only schematic. The same reference symbols designate the same objects, so that explanations from other figures can be used as a supplement if necessary. Show it:

• 1 : schematically a first example of an exhaust gas purification system;
• 2 : schematically another example of an exhaust gas cleaning system; and
• 3 : Schematically another example of an exhaust gas purification system.

Unless reference is made explicitly to a specific figure, the following explanations apply to both figures. The arrows each indicate the flow direction of a gas stream.

the 1 and 2 show two exemplary embodiments of exhaust gas cleaning systems 12, which is used to reduce the concentration of certain sulfur compounds in an exhaust gas, in particular a plant 1. The operation 1 is preferably an animal carcass processing facility or a slaughterhouse. An exhaust gas flow 6 is discharged from the operation 1 via an exhaust gas line 11 in a flow direction R, the orientation of which is always directed away from the operation 1 . Due to the processes taking place in operation 1, this exhaust gas flow 6 regularly contains components which are strongly odour-polluting. In general, sulphur-containing compounds are classified as particularly problematic with regard to low odor thresholds, which are then to be regarded as odor-polluting. The emission control system 12 is particularly suitable for the treatment of exhaust streams containing at least one of the four compounds methyl mercaptan, dimethyl sulfide, dimethyl disulfide and dimethyl trisulfide. These are referred to as target components.

For this purpose, a plasma gas stream 7 is fed to the exhaust gas stream 6, in which at least hydroxyl radicals and ozone are generated by a non-thermal plasma before being fed to the exhaust gas stream 6, exhaust gas stream 6 and plasma gas stream 7 mix to form a first gas stream 8 and where within of the first gas stream 8 at least one of the target components in a pri mary reaction with the hydroxyl radicals, and reacts in a secondary reaction in a catalyst support 3 with the ozone, forming a second gas stream 9 in which the concentration of at least one of the target components is compared to the concentration of the corresponding target component in the Exhaust stream 6 is reduced.

The exhaust gas cleaning system 12 has a plasma generator 2 . This sucks in an air flow 13 from the environment. A non-thermal plasma is generated in the plasma generator 2 by a dielectric barrier discharge. In particular, ozone (O ₃ ) and hydroxyl radicals (OH−) are produced as part of a plasma gas flow 7 that leaves the plasma generator 2 .

The plasma gas stream 7 is fed through a feed line 15 at a mixing point 16 into the exhaust gas line 11, so that a first gas stream 8 is formed downstream of the mixing point 16, comprising the exhaust gas stream 6 and the plasma gas stream 7. The gases are preferred for effective mixing Injection lances or other mixing or swirling elements are provided in the exhaust pipe 11 . During and after the mixing of the exhaust gas stream 6 and the plasma gas stream 7, first chemical reactions occur between parts of the plasma gas stream 7 and the target components in the exhaust gas stream 6. In particular, a first primary chemical reaction takes place in which the plasma Gas stream 7 contained hydroxyl radicals (OH radicals) convert part of the target components in the exhaust gas stream 6, so that their concentration in the exhaust gas stream 6 and in the first gas stream 8 is significantly reduced.

The mass flow of the plasma gas flow 7 is preferably between 2% and 20%, particularly preferably between 5% and 15%, in particular about 10% of the mass flow of the exhaust gas flow 6. Efficient conversion of the target components can be achieved in this way. At the same time, the additional energy consumption due to the operation of the plasma generator 2 is manageable.

A secondary reaction occurs downstream, primarily due to the reaction of the ozone (O ₃ ) generated by the plasma generator 2 and fed to the first gas stream 8 . In the present example, this secondary reaction is made possible or facilitated by the provision of a catalyst on a catalyst support 3 . The first gas flow 8 flows into the catalyst support 3 and through it. The catalyst support 3 is porous and thus has a large surface area that is available for reactions. The catalyst carrier 3 is preferably formed by a carrier body, for example a honeycomb body, in particular a ceramic honeycomb body. The catalyst carrier 3 preferably comprises, in addition to a carrier body not shown in detail, a coating, in particular a washcoat, which is formed on the carrier body. The catalyst, ie the corresponding catalytically active compounds, are contained in the carrier body and/or in the coating. The coating preferably further increases the surface area available for the reaction of the target components.

With the help of the catalyst, ozone in the catalyst carrier 3 is oxidized to an oxygen radical (O) and oxygen (O ₂ ). The oxygen radical is bound to the catalyst. There it reacts with a molecule of one of the target components. The corresponding molecule is oxidized and the oxygen radical is separated from the catalyst. The reactants formed are entrained with the first gas stream 8 . Manganese oxide is preferably suitable as a catalyst, in particular MnO ₂ . Silicon oxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₃ ) are also suitable.

After leaving the catalyst support 3, the gas flows as a second gas flow 9 to a biofilter 5. The concentration of the target components contained in the second gas flow 9 is already clear in comparison to the concentration of the target components contained in the exhaust gas flow 6 and in the first gas flow 8 reduced. After-treatment takes place within the biofilter 5 . In particular, there is a biological conversion of the remaining parts of the target components. The degradation products from the secondary and primary reactions are converted in the biofilter 5 by the microorganisms. In a biofilter, chemical compounds are converted by microorganisms. Depending on the purpose of the filter, special bacteria or fungi can be used as microorganisms. The chemical compounds and oxygen fed to the biofilter are broken down and the elements are recombined into non-harmful compounds such as water and carbon dioxide. Various organic products such as fibres, wood chips, root wood, granules or mixtures can serve as carriers for the microorganisms. The service life of a biofilter can vary greatly depending on the substances fed into it.

The gas post-treated in the biofilter 5 flows on as a cleaned gas flow 10 and can be discharged into the ambient air. The concentration of the target components in the cleaned gas stream 10 is reduced to such an extent that they are no longer perceived as having an odor and in particular are below the odor threshold.

According to a second embodiment, which is 2 shown can be between the kata lysatorträger 3 and the biofilter 5, a gas scrubber 4 may be formed. Within the gas scrubber 4, certain components of the second gas stream 8 can be released into a liquid and thus removed from the gas stream. The degradation products from the primary and secondary reaction are more soluble in water than the target components and can be washed out at least partially in the gas scrubber 4 as a result. In particular, those components of the gas stream 9 that would damage the biofilter 5 and thus shorten its service life can be reduced in concentration by a gas scrubber 4 . The position of the gas scrubber 4, which is located upstream from the biofilter 5, is therefore advantageous. The third gas stream 14 treated by the gas scrubber 4 is, according to the exemplary embodiment in 2 fed to the biofilter 5 and can then be released to the environment as a cleaned gas flow 10 . Otherwise, reference is made to the description of the first exemplary embodiment above.

3 FIG. 12 schematically shows another example of an emission control system 12. This is similar to the first example 1 . Therefore, in order to avoid repetition, only the differences to the example should be mentioned here 1 are explained. Otherwise, reference is made to the previous descriptions of the figures. In the embodiment in FIG 3 the first gas stream 8 flows downstream from the mixing point 16 into an adsorbent carrier 17 instead of into a catalyst carrier 3. An adsorbent is formed in this carrier, through which further conversion of target components and/or ozone can take place. In this example, activated carbon is used as an adsorbent. Also in the second example 2 the catalyst support 3 can be replaced by an adsorbent support 17.

The invention relates to an exhaust gas cleaning system 12 and a method for treating an exhaust gas flow 6 from a plant 1, for example an animal carcass processing plant. In this case, non-thermal plasma, which generates ozone and OH radicals in a plasma gas flow 7, is used to remove sulfur-containing target components (methyl mercaptan (CH ₄ S), dimethyl sulfide (C ₂ H ₆ S), dimethyl disulfide (C ₂ H ₆ S ₂ ) and dimethyl trisulfide (C ₂ H ₆ S ₃ )) in the exhaust gas stream 6 in a primary and a secondary reaction. The primary reaction takes place through the mere combination of exhaust gas and plasma gas flow. The secondary reaction can be accelerated by using a catalyst. This significantly reduces the concentration of the target components. As an alternative to using a catalyst, a further conversion of the target components and/or ozone can take place using an adsorbent. The second gas stream 9 generated in this way is particularly preferably post-treated in a gas scrubber 4 and/or a biofilter 5 .

reference list

1

operation

2

plasma generator

3

catalyst support

4

scrubber

5

biofilter

6

exhaust flow

7

plasma gas flow

8th

first gas stream

9

second gas stream

10

cleaned gas stream

11

exhaust pipe

12

emission control system

13

airflow

14

third gas stream

15

supply line

16

mixing point

17

adsorbent carrier

R

flow direction

Claims (14)

A method for purifying an exhaust stream (6) comprising at least one of the following target components methyl mercaptan, dimethyl sulfide, dimethyl disulfide and dimethyl trisulfide, wherein a plasma gas stream (7) is fed to the exhaust gas stream (6), in which at least hydroxyl radicals and ozone are generated by a non-thermal plasma before being fed to the exhaust gas stream (6), exhaust gas stream (6) and plasma gas stream (7) are added mixing a first gas stream (8) and wherein within the first gas stream (8) at least one of the target components reacts in a primary reaction with the hydroxyl radicals and in a secondary reaction with the ozone, a second gas stream (9) being formed in which the concentration of at least one of the Target components compared to the concentration of the corresponding target component in the exhaust stream (6) is reduced. procedure after claim 1 , wherein the reaction rate for the secondary reaction is increased by a catalyst. procedure after claim 2 , wherein manganese oxide, in particular manganese(IV) oxide (MnO ₂ ), is provided as the catalyst. procedure after claim 1 , wherein the first gas flow (8) flows through an adsorbent in which a reaction of at least one of the target components with ozone takes place, so that the concentration of at least one of the target components and/or ozone in the second gas flow (9) is reduced . Procedure according to one of Claims 1 until 4 , wherein the second gas flow (9) is subjected to after-treatment by at least one of the post-treatment units biofilter (5) and gas scrubber (4). procedure after claim 5 , wherein the second gas stream (9) is passed through the gas scrubber (4) and then through the biofilter (5). Method according to one of the preceding claims, in which the non-thermal plasma is generated by a dielectric barrier discharge. Exhaust gas cleaning system (12) for cleaning an exhaust gas flow (6) which comprises at least one of the following target components methyl mercaptan, dimethyl sulfide, dimethyl disulphide and dimethyl trisulfide, for carrying out the method according to one of the preceding claims, comprising: - an exhaust pipe (11) for conducting a gas flow, through which a flow can flow in one flow direction during operation, - A supply line (15) with a plasma generator (2) through which an air stream (13) can flow to form a plasma gas stream (7) and through which hydroxyl radicals and ozone are generated in this plasma gas stream by a non-thermal plasma (7) can be produced, the supply line (15) being connected to the exhaust gas line (11) at a mixing point (16) for mixing the exhaust gas flow (6) and the plasma gas flow (7) to form a first gas flow (8). Exhaust gas cleaning system (12) after claim 8 , which in the direction of flow downstream of the mixing point (16) comprises a catalyst support (3) with a catalyst, through which the reaction rate for the secondary reaction is increased. Catalyst carrier (3) after claim 9 , wherein the catalyst support (3) comprises manganese oxide, in particular manganese(IV) oxide (MnO ₂ ), as the catalyst. Exhaust gas cleaning system (12) after claim 8 , which comprises an adsorbent carrier (17) with an adsorbent downstream of the mixing point (16) in the direction of flow through which the concentration of at least one of the target components and/or ozone in the second gas stream (9) is reduced. Emission control system (12) according to one of Claims 8 until 10 , in which at least one of the post-treatment units biofilter (5) and gas scrubber (4) is formed downstream of the catalyst support (3) in the direction of flow. Exhaust gas cleaning system (12) after claim 12 , which comprises a gas scrubber (4) and a biofilter (5) and the biofilter (5) is arranged downstream of the gas scrubber (4) in the direction of flow. Emission control system (12) according to one of Claims 8 until 13 , in which the non-thermal plasma can be generated by a dielectric barrier discharge.

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