PLANT AND METHOD FOR THE REGENERATIVE THERMAL OXIDATION OF RAW GAS

Description

[0001] The invention relates to a system for the regenerative thermal oxidation of raw gas with a combustion chamber and with a plurality of regenerators, each of which has a regenerator chamber communicating with the combustion chamber and containing a heat exchanger, with a supply line for feeding raw gas into a raw gas line and with a clean gas line for discharging clean gas, wherein a regenerator chamber of a regenerator can be selectively connected to and disconnected from the raw gas line via an adjustable raw gas shut-off device, as well as selectively connected to and disconnected from the clean gas line via an adjustable clean gas shut-off device, independently of the regenerator chambers of the other regenerators.Furthermore, the invention relates to a method for operating a plant for treating raw gas by means of regenerative thermal oxidation, wherein the plant has a combustion chamber and a plurality of regenerators which communicate with the combustion chamber and which each have a regenerator chamber with a heat exchanger arranged therein, in which alternately at least one of the regenerators is purged with purge gas, raw gas is supplied to at least two regenerators, clean gas is drawn off from at least two regenerator chambers and at least one regenerator chamber is operated in a pyrolysis operation.

[0002] Such a plant and such a process are known from DE 10 2004 022 737 A1 and EP 1 593 909 B2.

[0003] Regenerative thermal oxidation (RTO) systems are used in various industries to remove combustible pollutants from raw gas by oxidizing it at high temperatures in a combustion chamber. The raw gas is fed into the combustion chamber through first regenerators, which contain a heat exchanger housed within a regenerator chamber. This heat exchanger preheats the raw gas before it enters the combustion chamber. The heat exchanger preferably includes a heat storage mass that was heated in a previous process step by the input of thermal energy. As the raw gas flows through it, the heat storage mass transfers heat to the raw gas, preheating it before it enters the combustion chamber.The raw gas, purified of pollutants in the combustion chamber and also referred to as hot gas or hot clean gas, is then discharged as clean gas through second regenerators with a heat exchanger located in a regenerator chamber. Heat is transferred to the heat exchanger, preferably to a heat storage mass within this exchanger. Once the heat exchanger in the first regenerator has cooled to a certain extent, the system switches over. The raw gas is then fed through the second regenerators into the combustion chamber and discharged from the first regenerators as clean gas. Depending on the composition of the raw gas, this continuous switching of the system allows the pollutants to be combusted in the combustion chamber without any external energy input or with only a minimal energy input.

[0004] WO 2012 / 046580 A1 describes a recirculating gas exhaust gas (RTO) system for cleaning raw gas containing organic substances, specifically volatile organic compounds (VOCs) generated during the use of adhesives, in printing and painting processes, in facilities where organic solvents are used for cleaning, and in chemical plants. This system includes a filter through which purge gas used to clean a regenerator can be returned to the raw gas being cleaned. Because the purified gas cools as it flows through the heat exchangers in the regenerator chamber, components from the raw gas that were not completely combusted in the combustion chamber, or that were formed there through conversion, can precipitate out.

[0005] In the RTO plants used in the graphite processing industry, blockages of tar substances form in the regenerator chambers over time, for example.

[0006] It is known to subject the regenerator chambers in such RTO plants to pyrolysis at regular intervals by burning them with a gas flame, by introducing hot purified gas from the combustion chamber, or by otherwise introducing hot air. This process removes the tar substances from the regenerator chambers, releasing them into the environment with or without further treatment. For this purpose, the regenerator chambers are burned with a gas flame, for example, in the combustion chamber of the RTO plant, which combusts the tar substances.

[0007] German patent DE 10 2006 058 969 A1 describes, for example, a plant for the regenerative thermal oxidation of raw gas, designed for the regenerative afterburning of sticky pollutant particles in exhaust gas, in particular coal and / or graphite particles in exhaust air. Here, raw gas from a raw gas pipeline is converted into clean gas, which can then be released into the environment via a clean gas pipeline. The plant includes afterburning units for regenerative thermal oxidation, each with a combustion chamber and regenerator chambers that communicate with the combustion chamber.For the regenerator chambers of each afterburner, the system can alternate between a raw gas cleaning operation, in which raw gas introduced into a regenerator chamber is cleaned; a purging operation, in which the regenerator chamber is purified with clean gas, which then passes as purge gas into another regenerator chamber; and a pyrolysis operation, in which dirt particles are oxidized in the regenerator chamber. The oxidation products generated in the pyrolysis operation of a regenerator chamber are combusted in the combustion chamber, with the combustion products passing through another regenerator chamber into the clean gas line and from there into the environment.

[0008] Nitrogen oxides in raw gas cannot be easily removed by combustion in a combustion chamber. To remove nitrogen oxides from raw gas, it is known to react it with ammonia in a reaction chamber at defined temperatures to produce water and nitrogen. However, due to temperature fluctuations and changes in the composition of the raw gas, ammonium salts can form. These salts precipitate in the regenerator chambers of RTO plants, forming solid and / or slimy deposits that impair plant operation. This is because they reduce the efficiency of the heat exchangers and increase the flow resistance for both the clean and raw gas. Since ammonium salts are generally water-soluble, they can be removed from the regenerator chambers of an RTO plant by washing. However, this process requires shutting down the RTO plant, as complex heating and cooling cycles must be performed.

[0009] The object of the invention is to enable the regenerative oxidation of raw gas in an environmentally friendly continuous operation of a plant.

[0010] This problem is solved by the apparatus specified in claim 1 and the method specified in claim 24. Advantageous embodiments and further developments of the invention are specified in the dependent claims.

[0011] An inventive system for the regenerative thermal oxidation of raw gas has a combustion chamber and a plurality of regenerators, each containing a regenerator chamber communicating with the combustion chamber and containing a heat exchanger. The system includes a supply line for feeding raw gas into a raw gas line and a clean gas line for discharging clean gas. Each regenerator chamber can be selectively connected to and disconnected from the raw gas line via an adjustable raw gas shut-off valve, and vice versa, independently of the regenerator chambers of the other regenerators. The system includes a separator for removing suspended particles from the raw gas fed into the raw gas line via the supply line.

[0012] In a method according to the invention for operating a plant for treating raw gas by means of regenerative thermal oxidation, wherein the plant comprises a combustion chamber and a plurality of regenerators that communicate with the combustion chamber and each of which has a regenerator chamber with a heat exchanger arranged therein, at least one of the regenerators is alternately purged with purge gas, raw gas is supplied to at least two of the regenerators, clean gas is drawn from the regenerator chamber of at least two of the regenerators, and the regenerator chamber of at least one of the regenerators is operated in a burn-off mode. During this process, the burn-off gas released during the burn-off operation of the regenerator chamber of the at least one regenerator is returned to the raw gas to be treated and filtered with the raw gas before being supplied to the regenerators.

[0013] The invention is based on the idea that solids deposited on the surfaces of the heat exchanger in a regenerator chamber can be removed by heating the regenerator chamber to a temperature at which these solids transition into the gaseous phase and flow out of the regenerator chamber. The invention utilizes the fact that, upon cooling outside the regenerator chamber, the material of the solids becomes solid or at least liquid again from the gaseous phase due to crystallization or interaction with other substances, so that it can be separated from a gas stream in a separator to prevent the material from being released into the environment.By directing the gas stream, now free of solids, back into the combustion chamber, it is possible to ensure that pollutants not separated in the separator are not immediately released into the environment, but can be burned in the combustion chamber.

[0014] In this way, it is not only possible to avoid shutting down an RTO plant for cleaning the regenerator chambers of regenerators, but it is also possible to ensure that the material accumulated in the regenerator chambers, such as ammonium salts or phosphorus-containing substances and their decomposition products in the form of dust, acids or ammonia, does not enter the environment.

[0015] The separation device can be designed in particular as a filter for filtering out solid particles from a gaseous fluid, e.g. as a bag filter, pocket filter, candle filter or as an electrostatic precipitator.

[0016] The system may have a combustion gas line connected to the supply line at a connection point, which serves to receive combustion gas containing solids from the regenerator chambers, wherein the combustion gas line has regenerator chamber connection points assigned to the different regenerator chambers and wherein the regenerator chamber of each of the regenerators can be selectively connected to or disconnected from its assigned regenerator chamber connection point of the combustion gas line independently of the regenerator chambers of the other regenerators via an adjustable gas flow control device.

[0017] It is advantageous if each gas flow control device allows the adjustment of different opening cross-sections for the passage of gaseous fluid. In particular, it is advantageous if a combustion gas control device is arranged in the exhaust gas line for adjusting the discharge of gaseous fluid from the regenerator chambers of the regenerators.

[0018] In a preferred embodiment of the system, the combustion gas line is also used to receive purge gas flowing through the regenerator chambers.

[0019] Preferably, the system includes a control device for controlling the raw gas shut-off devices and the clean gas shut-off devices as well as the gas flow control devices in a burn-out operation, in which over a defined time interval i. Raw gas is supplied to the regenerator chambers of a first, third, and sixth regenerator from the raw gas line; ii. Clean gas is introduced into the clean gas line from the regenerator chambers of a second and fourth regenerator; iii. Purge gas is introduced into the combustion gas line from a regenerator chamber of a fifth regenerator at a first opening cross-section of the gas flow control device associated with the regenerator chamber; and iv. Combustion gas is introduced into the combustion gas line from a regenerator chamber of a seventh regenerator at a second opening cross-section of the gas flow control device associated with the regenerator chamber that is reduced compared to the first opening cross-section.

[0020] Alternatively, the system can also be operated in such a way that i. Raw gas is supplied to the regenerator chambers of a first and third regenerator of the regenerators from the raw gas line; ii. Clean gas is introduced into the clean gas line from the regenerator chambers of a second, fourth, and sixth regenerator of the regenerators; iii. Purge gas is introduced into the combustion gas line from a regenerator chamber of a fifth regenerator at a first opening cross-section of the gas flow control device associated with the regenerator chamber; and iv. Combustion gas is introduced into the combustion gas line from a regenerator chamber of a seventh regenerator at a second opening cross-section of the gas flow control device associated with the regenerator chamber that is reduced compared to the first opening cross-section.

[0021] The control unit for controlling the raw gas shut-off devices and the clean gas shut-off devices as well as the gas flow control devices is designed, if possible, for normal operation, in which i. Raw gas is supplied to the regenerator chambers of a first, third and sixth regenerator from the raw gas line, ii. Clean gas is introduced into the clean gas line from the regenerator chambers of a second, fourth and sixth regenerator, and iii. Purge gas is introduced from a regenerator chamber of a seventh of the regenerators into the combustion gas line at a first opening cross-section of the gas flow control device associated with the regenerator chamber.

[0022] It should be noted that, for example, in six consecutive time intervals, the fifth regenerator can be different, while the seventh regenerator can be identical. It should also be noted that in seven consecutive time intervals, the seventh regenerator can be different.

[0023] The system may include a purge gas line for receiving purge gas flowing through the regenerator chambers, wherein the purge gas line has regenerator chamber connection points assigned to the different regenerator chambers, and wherein the regenerator chamber of each of the regenerators can be selectively connected to or disconnected from its assigned regenerator chamber connection point in the purge gas line independently of the regenerator chambers of the other regenerators via an adjustable purge gas control device.

[0024] In particular, the system may also include a control device for controlling the raw gas shut-off devices, the clean gas shut-off devices and the gas flow control devices, as well as the purge gas control devices in a burn-off operation, in which over a defined time interval i. Raw gas is supplied to the regenerator chambers of a first, third, and sixth regenerator from the raw gas line; ii. Clean gas is introduced into the clean gas line from the regenerator chambers of a second and fourth regenerator; iii. Purge gas is introduced into the purge gas line from a regenerator chamber of a fifth regenerator at a first opening cross-section of the purge gas control device associated with the regenerator chamber; and iv. Purge gas is introduced into the purge gas line from a regenerator chamber of a seventh regenerator at a second opening cross-section of the gas flow control device associated with the regenerator chamber that is reduced compared to the first opening cross-section.

[0025] Alternatively, the system can also be operated in such a way that i. Raw gas is supplied to the regenerator chambers of a first and third regenerator from the raw gas line; ii. Clean gas is introduced into the clean gas line from the regenerator chambers of a second, fourth, and sixth regenerator; iii. Purge gas is introduced into the purge gas line from a regenerator chamber of a fifth regenerator at a first opening cross-section of the purge gas control device associated with the regenerator chamber; and iv. Exhaust gas is introduced into the exhaust gas line from a regenerator chamber of a seventh regenerator at a second opening cross-section of the gas flow control device associated with the regenerator chamber that is reduced compared to the first opening cross-section.

[0026] The control unit can be used to control the raw gas shut-off devices, the clean gas shut-off devices, and the purge gas control devices in a maintenance operation, in which over a defined time interval i. raw gas is supplied to the regenerator chambers of a first, third and sixth regenerator from the raw gas line, ii. clean gas is introduced into the clean gas line from the regenerator chambers of a second and fourth regenerator, and iii. the regenerator chamber of a seventh of the regenerators is separated from the raw gas line and from the clean gas line as well as from the purge gas line.

[0027] The fifth regenerator can, for example, be different in six consecutive time intervals, while the seventh regenerator is identical in each interval. The seventh regenerator can also be different in seven consecutive time intervals.

[0028] It is advantageous if each purge gas control device in the system allows the adjustment of different opening cross-sections for the passage of purge gas.

[0029] It is also advantageous if a purge gas control device is arranged in the purge gas line for regulating the discharge of gaseous fluid from the regenerator chambers of the regenerators. A blower may be arranged in the purge gas line. In particular, a purge gas control device may be arranged in the purge gas line for regulating the discharge of gaseous fluid from the regenerator chambers of the regenerators. In particular, the purge gas line may be connected to the clean gas line, and the clean gas line may be connected to a chimney.

[0030] An adjustable shut-off device is preferably arranged in the raw gas line, serving to enable or disable the supply of raw gas to the regenerator chambers. The system may include a raw gas bypass line connected to a chimney, which communicates with the raw gas line at a connection point on the side of the shut-off device facing the filter assembly. In particular, a raw gas supply blower for supplying raw gas to the regenerator chambers of the regenerators through the raw gas line may be arranged on a side of the connection point for the raw gas bypass line facing away from the filter assembly, with a pressure side facing the regenerator chambers.

[0031] The purge gas line can be connected to the raw gas line between the raw gas supply blower and the shut-off device. Preferably, a raw gas conveying blower is arranged in the raw gas line on the side of the raw gas line connection point for the raw gas bypass line facing the filter device. This blower has a suction side facing the filter device. The system can, for example, contain at least seven regenerator chambers.

[0032] The plant described above is particularly suitable for the regenerative thermal oxidation of raw gas volume flows S with S ≥ 150,000 m³ / h in the presence of ammonia and inorganic acids. The plant can therefore be used especially for the regenerative thermal oxidation of raw gas containing nitrogen oxides and is particularly suitable for use in a cement plant.

[0033] The invention will now be explained in more detail with reference to the exemplary embodiments shown schematically in the figures.

[0034] They show: Fig. 1 A cement plant with an SNCR system and an RTO system for cleaning raw gas; Fig. 2 A view of the RTO system for cleaning raw gas; Fig. 3 Normal operation of the RTO system; Fig. 4 Burnout operation of the RTO system; Fig. 5 Maintenance operation of the RTO system; Fig. 6 A cement plant with an SNCR system and another RTO system for cleaning raw gas; Fig. 7 A view of the other RTO system for cleaning raw gas; and Fig. 8 Another RTO system for cleaning raw gas, specifically designed for use in a cement plant.

[0035] The one in Fig. 1The cement plant 10 shown has a raw material preparation stage 12, in which limestone and clay are combined, coarsely crushed, and stored as a premixed raw material. Aggregates from silos can be added to the stored, premixed raw material. Cement plant 10 includes a processing stage 14, in which the premixed raw material is finely ground in a mill under a hot gas atmosphere and distributed to feed silos. Cement plant 10 contains a calciner heat exchanger tower 16 with a SCNR system 24. The calciner heat exchanger tower 16 is connected to a rotary kiln 18, which is used to produce clinker. This clinker is processed in a final stage 22 of cement plant 10, which includes a clinker processing stage 20. In the calciner heat exchanger tower 16, the finely ground raw materials are fed in and heated in heat exchanger cyclones in counterflow to the exhaust gases of the rotary kiln.In this process, carbon dioxide is driven out of the limestone contained in the raw materials.

[0036] It should be noted that in a modified embodiment of the cement plant, the heat exchanger cyclones can be heated not only by the exhaust gases of the rotary kiln, but also by heat generated in a precalciner, where, for example, alternative fuels such as car tires or waste are burned. This precalciner can be supplied with so-called tertiary air for oxygen, i.e., preheated air from the clinker cooler.

[0037] In the rotary kiln 18, the material fed into it from the calciner heat exchanger tower 16 is processed into clinker at a temperature T of up to approximately 1,450 °C. For this purpose, the rotary kiln 18 contains a burner unit designed as a multi-fuel burner and a rotary tube. The cement plant 10 has a primary air supply unit and a secondary air supply unit for the rotary tube of the rotary kiln 18. In the cement plant 10, the hot clinker produced in the rotary tube is then transferred to the final stage 22, which contains a clinker cooler that cools the hot clinker by adding air. Part of the hot air generated during the cooling of the clinker is fed into the calciner heat exchanger tower 16, and the other part is released into the environment through a chimney after being cleaned in a dust filter.The dust collected in the dust filter is recycled and combined with the cooled clinker in the clinker silo. In the final stage, the clinker is mixed with various aggregates, such as gypsum, to create the cement. It is then finely ground in another mill and stored in cement silos. From there, the finished cement can be packaged and shipped.

[0038] In the cement plant 10, preheated and largely calcined material from the calciner heat exchanger tower 16 enters the rotary kiln 18. The exhaust gases from the rotary kiln and the calciner heat exchanger tower 16 are passed through an SCNR system 24, which has a heat exchanger tower into which ammonia is injected.

[0039] In the SNCR system 24, the injected ammonia reacts with harmful nitrogen monoxide (NO) and nitrogen dioxide (NO2) in the exhaust gases of the rotary kiln 18 at a reaction temperature, preferably between 850 °C and 1,100 °C, predominantly to form harmless molecular nitrogen (N2) and water.

[0040] In cement plant 10, the exhaust gases treated in the SCNR plant 24 from the rotary kiln 18 and the calciner heat exchanger tower 16 are fed as raw gas to an RTO plant 26 for the regenerative thermal oxidation of raw gas in a plant section 27. There, the exhaust gases fed to the SCNR plant 24 as raw gas can be freed from pollutants by means of regenerative thermal oxidation and released as clean gas into the environment through a chimney 28.

[0041] The Fig. 2Figure 26 is a schematic view of the RTO plant 26 in the cement plant 10. The RTO plant 26 contains a combustion chamber 29 in plant section 27 for the regenerative thermal oxidation of raw gas and has seven regenerators 30, 32, 34, 36, 38, 40, and 41, each of which has a regenerator chamber 42, 44, 46, 48, 50, 52, 54 communicating with the combustion chamber 29, and a heat exchanger 56 arranged therein, which consists of ceramic molded parts. The RTO plant 26 has a feed line 58 for supplying raw gas into a raw gas line 60 and contains a clean gas line 62 for discharging clean gas. In the RTO plant 26, the regenerator chambers 42, 44, 46, 48, 50, 52, 54 of the regenerators 30, 32, 34, 36, 38, 40 and 41 can each be independently connected to or disconnected from the raw gas line 60 by means of an adjustable raw gas shut-off device 64, 66, 68, 70, 72, 74, 75.Accordingly, the regenerator chambers 42, 44, 46, 48, 50, 52, 54 of the regenerators 30, 32, 34, 36, 38, 40 and 41 can each be independently connected to and disconnected from the clean gas line 62 by means of an adjustable clean gas shut-off device 76, 78, 80, 82, 84, 86, 88. The RTO system 26 includes a separator 90 for separating suspended particles from the raw gas supplied from the feed line 58 into the raw gas line 60. The separator 90 is a multi-stage filter for filtering out solid particles from a gaseous fluid.

[0042] In RTO plant 26, there is a combustion gas line 92. The combustion gas line 92 is connected at a connection point 94 to the supply line 58 for the delivery of raw gas into the raw gas line 60. The combustion gas line 92 serves to receive combustion gas containing solids from the regenerator chambers 42, 44, 46, 48, 50, 52, and 54. The combustion gas line 92 has regenerator chamber connection points 96, 98, 100, 102, 104, 106, and 108 assigned to the different regenerator chambers 42, 44, 46, 48, 50, 52, and 54. The regenerator chambers 42, 44, 46, 48, 50, 52, 54 of each of the regenerators 30, 32, 34, 36, 38, 40 and 41 can be connected to or disconnected from the regenerator chamber connection point 96, 98, 100, 102, 104, 106, 108 of the exhaust gas line 92 in the RTO system 26, independently of the regenerator chambers of the other regenerators, via an adjustable gas flow control device 110, 112, 114, 116, 118, 120, 122.Each gas flow control device 110, 112, 114, 116, 118, 120, 122 enables the adjustment of different opening cross-sections for the passage of gaseous fluid.

[0043] In the exhaust gas line 92, an exhaust gas control device 124 is arranged for adjusting the discharge of gaseous fluid from the regenerator chambers 42, 44, 46, 48, 50, 52, 54 of the regenerators 30, 32, 34, 36, 38, 40 and 41. In the RTO system 26, the exhaust gas line 92 also serves to receive purge gas flowing through the regenerator chambers 42, 44, 46, 48, 50, 52, 54.

[0044] It should be noted that in a modified embodiment of the RTO system 26, it may be provided that the combustion gas line 92 is connected at a connection point 94' to the supply line 58 for supplying raw gas into the raw gas line 60, which is located between a blower 134' and the separator device 90.

[0045] The clean gas line 62 in the RTO system 26 is connected to the chimney 28. An adjustable shut-off valve 126 is arranged in the raw gas line 60, which serves to enable or disable the supply of raw gas to the regenerator chambers 42, 44, 46, 48, 50, 52, 54 of each of the regenerators 30, 32, 34, 36, 38, 40 and 41. The RTO system 26 has a raw gas bypass line 128 connected to the chimney 28, which communicates with the raw gas line 60 via a raw gas line connection point 130 located on one side of the shut-off valve 126 facing the separator 90.In the raw gas line 60, on the side of the raw gas line connection point 130 facing away from the separator device 90, there is a raw gas supply blower 132 for supplying raw gas to the regenerator chambers 42, 44, 46, 48, 50, 52, 54 of the regenerators 30, 32, 34, 36, 38, 40 and 41 through the raw gas line 60, which has a pressure side facing the regenerator chambers 42, 44, 46, 48, 50, 52, 54. In the raw gas line 60, on one side of the raw gas line connection point 130 facing the separator device 90, a raw gas conveying blower 134 is arranged for conveying raw gas through the raw gas line 60 from the separator device 90, which has a suction side facing the filter device.

[0046] The RTO system 26 includes a control unit 136 for controlling the raw gas shut-off devices 64, 66, 68, 70, 72, 74 and 75 and the clean gas shut-off devices 76, 78, 80, 82, 84, 86, 88 as well as the gas flow control devices 110, 112, 114, 116, 118, 120, 122. The control unit 136 enables the RTO system 26 to be operated in a normal operating mode, in a maintenance operating mode and in a burn-out operating mode. For the supply of fresh air to the raw gas line 60, the RTO system 26 has a fresh air line 137 with a shut-off device 139, which is connected to the raw gas line 60 at a fresh air supply connection point 141, which is located between the raw gas supply blower 132 and the shut-off device 126.

[0047] The Fig. 3 The figure shows the combustion chamber 29 with the regenerators 30, 32, 34, 36, 38, 40 and 41 of the RTO plant 26 in successive different operating states I to VII of the normal operating mode, each lasting e.g. 1 minute.

[0048] Here, raw gas R is alternately supplied from raw gas line 60 to regenerator chambers 42, 44, 46, 48, 50, 52, 54 of a first, third, and sixth regenerator 30, 32, 34, 36, 38, 40, and 41, clean gas C from regenerator chambers 42, 44, 46, 48, 50, 52, 54 of a second, fourth, and sixth regenerator 30, 32, 34, 36, 38, 40, and 41 is introduced into clean gas line 62, and purge gas S is supplied from a regenerator chamber 42, 44, 46, 48, 50, 52, 54 of a seventh regenerator 30, 32, 34, 36, 38, 40, and 41. into the combustion gas line 92 at a first opening cross-section of the gas flow control device assigned to the regenerator chamber.

[0049] In the normal operating mode of the RTO system 26, the raw gas laden with pollutants flows through preheated regenerators 30, 32, 34, 36, 38, 40, or 41 in one of the regenerator chambers 42, 44, 46, 48, 50, 52, or 54 of the RTO system 26, which are filled with ceramic components acting as heat exchangers. The preheated raw gas then enters the combustion chamber 29 of the RTO system 26, where complete oxidation of the pollutants takes place. The heat of combustion released during this process reduces the required burner power proportionally to the pollutant concentration. This enables autothermal operation above a certain pollutant concentration, in which no additional energy is required to maintain the temperature in the combustion chamber 29 at the level necessary for oxidation.The purified, hot exhaust gas then flows as clean gas through second regenerators 30, 32, 34, 36, 38, 40, or 41 in the RTO system 26 and transfers its heat content to the heat exchanger in the corresponding regenerator chambers 42, 44, 46, 48, 50, 52, 54 before the clean gas is released to the atmosphere via a stack. This operating condition is maintained until the preheating temperature of the first preheated regenerators 30, 32, 34, 36, 38, 40, or 41 drops. The flow direction is then switched by means of the control device 136 after a defined time interval, so that the unpurified raw gas then flows through the last preheated second regenerators 30, 32, 34, 36, 38, 40 or 41 into the RTO system 26 and, after oxidation, reheats the next regenerator of the RTO system 26.

[0050] To prevent a certain amount of raw gas from immediately entering the clean gas line 62 when the flow direction is reversed, the RTO system 26 contains a seventh regenerator 30, 32, 34, 36, 38, 40 and 41 with a regenerator chamber 42, 44, 46, 48, 50, 52, 54. While raw gas enters the first three regenerator chambers and clean gas exits the second three regenerator chambers, a seventh regenerator chamber is purged with exhaust gas from the combustion chamber 29. This pushes the remaining raw gas via the exhaust gas line 92 through the separator 90 into the raw gas line 60. Then this regenerator chamber is connected to the clean gas line 62 and another seventh regenerator chamber is purged with exhaust gas from the combustion chamber 29, etc. This prevents or at least largely minimizes raw gas slippage from the RTO system 26.

[0051] During the treatment of the exhaust gases from the rotary kiln 18 and the calciner heat exchanger tower 16 in the cement plant 10 in the SCNR plant 24, ammonium salts in particular can form, which enter the RTO plant in the gaseous state and precipitate as liquid and / or solid substances, in particular as a slime in the heat exchangers 56 in the regenerator chambers 42, 44, 46, 48, 50, 52, 54. To ensure that the heat exchangers 56 in the regenerator chambers 42, 44, 46, 48, 50, 52, 54 can be alternately flowed through by clean and raw gas without excessive flow losses, the control device 136 enables the operation of the RTO system 26 in a burnout operating mode in which the regenerators 30, 32, 34, 36, 38, 40 or 41 are subjected to pyrolysis.

[0052] In the Fig. 4The combustion chamber 29 with the regenerators 30, 32, 34, 36, 38, 40 and 41 of the RTO system 26 can be seen in successive different operating states I to VI of the burnout operating mode, each lasting e.g. 1 minute. Here, raw gas R is alternately supplied from raw gas line 60 to regenerator chambers 42, 44, 46, 48, 50, 52, 54 of a first, third and sixth regenerator 30, 32, 34, 36, 38, 40 or 41, clean gas C from regenerator chambers 42, 44, 46, 48, 50, 52, 54 of a second and fourth regenerator 30, 32, 34, 36, 38, 40 or 41 is introduced into clean gas line 62, and purge gas S from a regenerator chamber 42, 44, 46, 48, 50, 52, 54 of a fifth regenerator is introduced into the combustion gas line 92 at a first opening cross-section of the regenerator chamber 42, 44, 46, 48, 50, 52, 54 associated gas flow control device 110, 112, 114, 116, 118, 120, 122 is introduced and is drawn from a regenerator chamber 42, 44, 46, 48, 50, 52,54 of a seventh of the regenerators 30, 32, 34, 36, 38, 40 and 41 into the combustion gas line 92 with a second opening cross-section of the gas flow control device assigned to the regenerator chamber 42, 44, 46, 48, 50, 52, 54, combustion gas A is introduced into the combustion gas line 92.

[0053] The seventh of the regenerator chambers 42, 44, 46, 48, 50, 52, 54 is heated during this operation, so that ammonium salts, especially those precipitated therein as slime, liquid or solid, pass into the gaseous phase and through the exhaust gas line 92 into the supply line 58 for the supply of raw gas into the raw gas line 60, in order to then be separated from the raw gas conveyed through it by means of the separator device 90.

[0054] In this plant operation, raw gas is routed through three regenerator chambers and purified gas through two regenerator chambers, which does result in a higher pressure drop at the plant than in normal operation. However, the total number of 7 regenerator chambers (42, 44, 46, 48, 50, 52, 54) ensures that the higher flow velocities for the purified gas through the RTO system 26, associated with the higher pressure drop, are only 50% greater than in normal plant operation.

[0055] It should be noted that the RTO plant 26 can also be operated in such a way that raw gas is passed through two regenerator chambers and clean gas through three regenerator chambers.

[0056] The Fig. 5 The figure shows the combustion chamber 29 with the regenerators 30, 32, 34, 36, 38, 40 or 41 of the RTO system 26 in successive different operating states I to VI of the maintenance operating mode, each lasting e.g. 1 minute.

[0057] Here, raw gas R is alternately supplied from raw gas line 60 to regenerator chambers 42, 44, 46, 48, 50, 52, 54 of a first, third, and sixth regenerator 30, 32, 34, 36, 38, 40, or 41, and clean gas C is introduced from regenerator chambers 42, 44, 46, 48, 50, 52, 54 of a second, fourth, and sixth regenerator 30, 32, 34, 36, 38, 40, or 41 into clean gas line 62. In contrast, the regenerator chamber of the seventh regenerator 41 is separated from raw gas line 60, exhaust gas line 92, and clean gas line 62, allowing maintenance work W to be carried out on this regenerator chamber.

[0058] The Fig. 6 Figure 10 shows a cement plant with an SNCR plant (Figure 24) and another RTO plant (Figure 26). Fig. 7 This is a view of the further RTO plant 26' in the cement plant 10'. As far as the assemblies and the Fig. 6 the one in Fig. 1 to Fig. 5The described assemblies and elements are identified by the same numbers as reference symbols.

[0059] In the RTO system 26', there is a purge gas line 138, which serves to receive purge gas flowing through the regenerator chambers 42, 44, 46, 48, 50, 52, and 54. The purge gas line 138 has regenerator chamber connection points 140, 142, 144, 146, 148, 150, and 152, each assigned to the different regenerator chambers 42, 44, 46, 48, 50, 52, and 54. The regenerator chamber 42, 44, 46, 48, 50, 52, 54 of each of the regenerators 30, 32, 34, 36, 38, 40 and 41 is here, independently of the regenerator chambers 42, 44, 46, 48, 50, 52, 54 of the other regenerators 30, 32, 34, 36, 38, 40 and 41, optionally connected to or disconnected from its associated regenerator chamber connection point 140, 142, 144, 146, 148, 150 and 152 of the purge gas line via an adjustable purge gas control device 154, 156, 158, 160, 162, 164, 166.

[0060] The cement plant 10' has a control device 136' for controlling the raw gas shut-off devices 64, 66, 68, 70, 72, 74, 75, the clean gas shut-off devices 76, 78, 80, 82, 84, 86, 88 and the gas flow control devices 110, 112, 114, 116, 118, 120, 122 as well as the purge gas control devices 154, 156, 158, 160, 162, 164, 166 in a normal operating mode, in a maintenance operating mode and in a burnout operating mode.

[0061] In normal operating mode, the regenerator chambers 42, 44, 46, 48, 50, 52, 54 of a first, third and sixth regenerator 30, 32, 34, 36, 38, 40 or 41, as above based on the Fig. 3explained, raw gas R is supplied alternately from raw gas line 60, clean gas C is introduced into clean gas line 62 from regenerator chambers 42, 44, 46, 48, 50, 52, 54 of a second, fourth and sixth regenerator 30, 32, 34, 36, 38, 40 or 41, and purge gas S is introduced into purge gas line 138 from a regenerator chamber 42, 44, 46, 48, 50, 52, 54 of a seventh of the regenerators 30, 32, 34, 36, 38, 40 or 41.

[0062] In contrast, in the burnout operating mode, the regenerator chambers 42, 44, 46, 48, 50, 52, 54 of a first, third and sixth regenerator 30, 32, 34, 36, 38, 40 or 41 are operated according to the above descriptions. Fig. 4Raw gas R is supplied alternately from raw gas line 60, clean gas C is introduced into clean gas line 62 from regenerator chambers 42, 44, 46, 48, 50, 52, 54 of a second and fourth regenerator 30, 32, 34, 36, 38, 40 or 41, purge gas S is introduced into purge gas line 138 from a regenerator chamber 42, 44, 46, 48, 50, 52, 54 of a fifth regenerator, and exhaust gas A is introduced into exhaust gas line 92 from a regenerator chamber 42, 44, 46, 48, 50, 52, 54 of a seventh regenerator 30, 32, 34, 36, 38, 40 or 41.

[0063] The seventh of the regenerator chambers 42, 44, 46, 48, 50, 52, 54 is heated during this operation, so that in particular ammonium salts precipitated therein as slime, liquid or solid pass into the gaseous phase and through the combustion gas line 92 into the supply line 58 for the supply of raw gas into the raw gas line 60, in order to then be separated from the raw gas conveyed by means of the separator device 90.

[0064] For operating the RTO system 26' in a maintenance operating mode, as described above based on the Fig. 5As explained, raw gas R is alternately supplied from raw gas line 60 to regenerator chambers 42, 44, 46, 48, 50, 52 of a first, third, and sixth regenerator 30, 32, 34, 36, 38, or 40, respectively, and clean gas C is introduced into clean gas line 62 from regenerator chambers 42, 44, 46, 48, 50, 52 of a second, fourth, and sixth regenerator 30, 32, 34, 36, 38, or 40. In contrast, the regenerator chamber of the seventh regenerator 41 is separated from raw gas line 60, combustion gas line 92, and clean gas line 62, allowing maintenance work W to be carried out on this regenerator chamber.

[0065] The Fig. 8 The diagram shows another RTO system 26" for cleaning raw gas, which, like the RTO system 26' described above, can be used in particular for cleaning raw gas in a cement plant. The components and the Fig. 8 the one in Fig. 7The described assemblies and elements are identified by the same numbers as reference symbols.

[0066] Unlike in the above based on the Fig. 7 In the described system 26', there is a purge gas line 138' connected to the clean gas line 62, which serves to receive purge gas flowing through the regenerator chambers 42, 44, 46, 48, 50, 52, 54. The purge gas line 138' can be separated from the clean gas line 62 by means of a shut-off device 168. In A blower unit 170 is arranged in the purge gas line, which makes it possible to draw in clean gas from the clean gas line 62 and introduce it as purge gas into the regenerator chambers 42, 44, 46, 48, 50, 52, 54.

[0067] In summary, the following preferred features of the invention are particularly noteworthy: A system for the regenerative thermal oxidation of raw gas has a combustion chamber 29 and comprises a plurality of regenerators 30, 32, 34, 36, 38, 40, 41, each of which has a regenerator chamber 42, 44, 46, 48, 50, 52, 54 communicating with the combustion chamber 29 and containing a heat exchanger 56.The system includes a supply line 58 for feeding raw gas into a raw gas line 60 and a clean gas line 62 for discharging clean gas, wherein a regenerator chamber 42, 44, 46, 48, 50, 52, 54 of a regenerator 30, 32, 34, 36, 38, 40, 41 is each independently of the regenerator chambers 42, 44, 46, 48, 50, 52, 54 of the other regenerators 30, 32, 34, 36, 38, 40, 41, is optionally connected to and separated from the raw gas line 60 via an adjustable raw gas shut-off device 64, 66, 68, 70, 72, 74, 75, as well as via an adjustable clean gas shut-off device 76, 78, 80, 82, 84, 86, 88 can be optionally connected to and disconnected from the clean gas line 62. The system includes a separator 90 for separating suspended particles from the raw gas supplied from the supply line 58 into the raw gas line 60. List of reference symbols

[0068] 10, 10'Cement plant 12Raw material preparation stage 14Processing stage 16Calciner heat exchanger tower 18Rotary kiln 20Clinker processing stage 22Final stage 24SCNR plant 26, 26', 26"RTO plant 27Plant section 28Chimney 29Combustion chamber 30, 32, 34, 36, 38, 40, 41Regenerator 42, 44, 46, 48, 50, 52, 54Regenerator chamber 56Heat exchanger 58Supply line 60Raw gas line 62Clean gas line 64, 66, 68, 70, 72, 74, 75Raw gas shut-off valve 76, 78, 80, 82, 84, 86, 88 Clean gas shut-off device 90 Separator device 92 Exhaust gas line 94, 94' Connection point 96, 98, 100, 102, 104, 106, 108 Regenerator chamber connection point 110, 112, 114, 116, 118, 120, 122 Gas flow control device 124 Exhaust gas control device 126 Shut-off device 128 Raw gas bypass line 130 Raw gas line connection point 132 Raw gas supply blower 134 Raw gas conveying blower 134' Blower 136, 136' Control device 137 Fresh air line 138, 138' Purge gas line 139 Shut-off device 141 Fresh air supply connection point 140, 142, 144, 146, 148, 150,152Regenerator chamber connection points 154, 156, 158, 160, 162, 164, 166Purchase gas control device 168Shut-off device 170Blower unit AExhaust gas CRClean gas RRRRaw gas SPurchase gas WMaintenance work,

Claims

1. System for regenerative thermal oxidation of crude gas, the system comprising a combustion chamber (29) and a plurality of regenerators (30, 32, 34, 36, 38, 40, 41), which each have a regenerator chamber (42, 44, 46, 48, 50, 52, 54) that communicates with the combustion chamber (29) and contains a heat exchanger (56), the system comprising a feed line (58) for feeding crude gas into a crude gas line (60), the feed line (58) communicating with the crude gas line (60) through a separation device (90), the separating device (90) separating suspended particles in crude gas fed into the crude gas line (60) from the feed line (58), the system comprising a clean gas line (62) for discharging clean gas, a regenerator chamber (42, 44, 46, 48, 50, 52, 54) of a regenerator (30, 32, 34, 36, 38, 40, 41), independently of the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of the rest of the regenerators (30, 32, 34, 36, 38, 40, 41), being able to be optionally connected to the crude gas line (60) and separated from the crude gas line (60) via an adjustable crude gas shut-off element (64, 66, 68, 70, 72, 74, 75), as well as optionally connected to the clean gas line (62) and separated from the clean gas line (62) via an adjustable clean gas shut-off element (76, 78, 80, 82, 84, 86, 88), and the system comprising a burnout gas line (92) which has regenerator chamber connection points (96, 98, 100, 102, 104, 106, 108) which are each associated with the different regenerator chambers (42, 44, 46, 48, 50, 52, 54), the regenerator chamber (42, 44, 46, 48, 50, 52, 54) of each of the regenerators (30, 32, 34, 36, 38, 40, 41), independently of the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of the rest of the regenerators (30, 32, 34, 36, 38, 40, 41), being able to be optionally connected to or separated from the associated regenerator chamber connection point (96, 98, 100, 102, 104, 106, 108) of the burnout gas line (92) via an adjustable gas flow control element (110, 112, 114, 116, 118, 120, 122), characterized in that the burnout gas line (92) receives burnout gas containing solids from the regenerator chambers (42, 44, 46, 48, 50, 52, 54) and is connected to the feed line (58) at a connection point (94, 94') arranged upstream of the separating device (90).

2. System according to claim 1, characterized in that the separating device (90) is preferably designed as a filter for filtering out solid particles from a gaseous fluid and / or in that each gas flow control element (110, 112, 114, 116, 118, 120, 122) makes it possible to adjust different opening cross-sections for the passage of gaseous fluid and / or in that a burnout gas control element (124) is arranged in the burnout gas line (92) for adjusting the discharge of gaseous fluid from the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of the regenerators (30, 32, 34, 36, 38, 40, 41).

3. System according to either claim 1 or claim 2, characterized in that the burnout gas line (92) also receives purge gas flowing through the regenerator chambers (42, 44, 46, 48, 50, 52, 54).

4. System according to claim 3, characterized by a control device (136, 136') for controlling the crude gas shut-off elements (64, 66, 68, 70, 72, 74, 75) and the clean gas shut-off elements (76, 78, 80, 82, 84, 86, 88) as well as the gas flow control elements (110, 112, 114, 116, 118, 120, 122) in a burnout operation, in which over a defined time interval i. crude gas is fed to the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of a first, third and sixth regenerator of the regenerators (30, 32, 34, 36, 38, 40, 41) from the crude gas line (60), ii. clean gas is introduced into the clean gas line (62) from the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of a second and fourth regenerator of the regenerators (30, 32, 34, 36, 38, 40, 41), iii. purge gas is introduced into the burnout gas line (92) from a regenerator chamber (42, 44, 46, 48, 50, 52, 54) of a fifth of the regenerators (30, 32, 34, 36, 38, 40, 41) at a first opening cross-section of the gas flow control element (110, 112, 114, 116, 118, 120, 122) associated with the regenerator chamber (42, 44, 46, 48, 50, 52, 54); and iv. burnout gas is introduced into the burnout gas line (92) from a regenerator chamber (42, 44, 46, 48, 50, 52, 54) of a seventh of the regenerators (30, 32, 34, 36, 38, 40, 41) into the burnout gas line (92) at a second opening cross-section of the gas flow control element (110, 112, 114, 116, 118, 120, 122), associated with the regenerator chamber (42, 44, 46, 48, 50, 52, 54), which second opening cross-section is reduced with respect to the first opening cross-section; or v. crude gas is fed to the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of a first and third regenerator of the regenerators (30, 32, 34, 36, 38, 40, 41) from the crude gas line (60), vi. clean gas is introduced into the clean gas line (62) from the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of a second, fourth, and sixth regenerator of the regenerators (30, 32, 34, 36, 38, 40, 41), vii. purge gas is introduced into the burnout gas line (92) from a regenerator chamber (42, 44, 46, 48, 50, 52, 54) of a fifth of the regenerators (30, 32, 34, 36, 38, 40, 41) at a first opening cross-section of the gas flow control element (110, 112, 114, 116, 118, 120, 122) associated with the regenerator chamber (42, 44, 46, 48, 50, 52, 54); and viii. burnout gas is introduced into the burnout gas line (92) from a regenerator chamber (42, 44, 46, 48, 50, 52, 54) of a seventh of the regenerators (30, 32, 34, 36, 38, 40, 41) into the burnout gas line (92) at a second opening cross-section of the gas flow control element (110, 112, 114, 116, 118, 120, 122), associated with the regenerator chamber (42, 44, 46, 48, 50, 52, 54), which second opening cross-section is reduced with respect to the first opening cross-section.

5. System according to claim 4, characterized in that the control device (136, 136') is designed for controlling the crude gas shut-off elements (64, 66, 68, 70, 72, 74, 75) and the clean gas shut-off elements (76, 78, 80, 82, 84, 86, 88) as well as the gas flow control elements (110, 112, 114, 116, 118, 120, 122) for normal operation, in which i. crude gas is fed to the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of a first, third and sixth regenerator of the regenerators (30, 32, 34, 36, 38, 40, 41) from the crude gas line (60), ii. clean gas is introduced into the clean gas line (62) from the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of a second and fourth and sixth regenerator of the regenerators (30, 32, 34, 36, 38, 40, 41), and iii. purge gas is introduced into the burnout gas line (92) from a regenerator chamber (42, 44, 46, 48, 50, 52, 54) of a seventh of the regenerators (30, 32, 34, 36, 38, 40, 41) at a first opening cross-section of the gas flow control element (110, 112, 114, 116, 118, 120, 122) associated with the regenerator chamber (42, 44, 46, 48, 50, 52, 54).

6. System according to either claim 4 or claim 5, characterized in that in six consecutive time intervals, the fifth of the regenerators (30, 32, 34, 36, 38, 40, 41) is different in each case and the seventh of the regenerators (30, 32, 34, 36, 38, 40, 41) is identical in each case.

7. System according to claim 6, characterized in that the seventh of the regenerators (30, 32, 34, 36, 38, 40, 41) is preferably different in each of seven successive time intervals.

8. System according to either claim 1 or claim 2, characterized by a purge gas line (138, 138') for receiving purge gas flowing through the regenerator chambers (42, 44, 46, 48, 50, 52, 54), the purge gas line (138, 138') having regenerator chamber connection points (96, 98, 100, 102, 104, 106, 108) which are each associated with the different regenerator chambers (42, 44, 46, 48, 50, 52, 54), and the regenerator chamber (42, 44, 46, 48, 50, 52, 54) of each of the regenerators (30, 32, 34, 36, 38, 40, 41), independently of the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of the rest of the regenerators (30, 32, 34, 36, 38, 40, 41), being able to be optionally connected to or separated from the associated regenerator chamber connection point (140, 142, 144, 146, 148, 150, 152) of the purge gas line (138, 138') via an adjustable purge gas control element (154, 156, 158, 160, 162, 164, 166).

9. System according to either claim 1 or claim 2, characterized by a purge gas line (138) which is connected to the crude gas line and which, during purging of the regenerator chambers, receives purge gas flowing through the regenerator chambers (42, 44, 46, 48, 50, 52, 54) into the crude gas line (60) in order to feed crude gas accumulated in the regenerator chamber back into the crude gas line, the purge gas line (138) having regenerator chamber connection points (96, 98, 100, 102, 104, 106, 108) which are each associated with the different regenerator chambers (42, 44, 46, 48, 50, 52, 54), and the regenerator chamber (42, 44, 46, 48, 50, 52, 54) of each of the regenerators (30, 32, 34, 36, 38, 40, 41), independently of the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of the rest of the regenerators (30, 32, 34, 36, 38, 40, 41), being able to be optionally connected to or separated from the associated regenerator chamber connection point (140, 142, 144, 146, 148, 150, 152) of the purge gas line (138, 138') via an adjustable purge gas control element (154, 156, 158, 160, 162, 164, 166).

10. System according to claim 9, characterized in that the purge gas control element (154, 156, 158, 160, 162, 164, 166) is arranged in the purge gas line (138).

11. System according to either claim 1 or claim 2, characterized by a purge gas line (138') connected to the clean gas line (62) for receiving purge gas flowing from the clean gas line (62) through the regenerator chambers (42, 44, 46, 48, 50, 52, 54) during purging of the regenerator chambers in order to purge crude gas accumulated in a regenerator chamber (42, 44, 46, 48, 50, 52, 54) into the combustion chamber, the purge gas line (138') having regenerator chamber connection points (96, 98, 100, 102, 104, 106, 108) which are each associated with the different regenerator chambers (42, 44, 46, 48, 50, 52, 54), and the regenerator chamber (42, 44, 46, 48, 50, 52, 54) of each of the regenerators (30, 32, 34, 36, 38, 40, 41), independently of the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of the rest of the regenerators (30, 32, 34, 36, 38, 40, 41), being able to be optionally connected to or separated from the associated regenerator chamber connection point (140, 142, 144, 146, 148, 150, 152) of the purge gas line (138, 138') via an adjustable purge gas control element (154, 156, 158, 160, 162, 164, 166).

12. System according to claim 11, characterized in that a fan is arranged in the purge gas line (138').

13. System according to any of claims 8 to 12, characterized by a control device (136, 136') for controlling the crude gas shut-off elements (64, 66, 68, 70, 72, 74, 75), the clean gas shut-off elements (76, 78, 80, 82, 84, 86, 88) and the gas flow control elements (110, 112, 114, 116, 118, 120, 122) as well as the purge gas control elements (154, 156, 158, 160, 162, 164, 166) in a burnout operation, in which over a defined time interval i. crude gas is fed to the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of a first, third and sixth regenerator of the regenerators (30, 32, 34, 36, 38, 40, 41) from the crude gas line (60), ii. clean gas is introduced into the clean gas line (62) from the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of a second and fourth regenerator of the regenerators (30, 32, 34, 36, 38, 40, 41), iii. purge gas is introduced into the purge gas line (138, 138') from a regenerator chamber (42, 44, 46, 48, 50, 52, 54) of a fifth of the regenerators (30, 32, 34, 36, 38, 40, 41) at a first opening cross-section of the purge gas control element (154, 156, 158, 160, 162, 164, 166) associated with the regenerator chamber (42, 44, 46, 48, 50, 52, 54); and iv. burnout gas is introduced into the burnout gas line (92) from a regenerator chamber (42, 44, 46, 48, 50, 52, 54) of a seventh of the regenerators (30, 32, 34, 36, 38, 40, 41) into the burnout gas line (92) at a second opening cross-section of the gas flow control element (110, 112, 114, 116, 118, 120, 122), associated with the regenerator chamber (42, 44, 46, 48, 50, 52, 54), which second opening cross-section is reduced with respect to the first opening cross-section; or i. crude gas is fed to the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of a first and third regenerator of the regenerators (30, 32, 34, 36, 38, 40, 41) from the crude gas line (60), ii. clean gas is introduced into the clean gas line (62) from the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of a second, fourth, and sixth regenerator of the regenerators (30, 32, 34, 36, 38, 40, 41), iii. purge gas is introduced into the purge gas line (138, 138') from a regenerator chamber (42, 44, 46, 48, 50, 52, 54) of a fifth of the regenerators (30, 32, 34, 36, 38, 40, 41) at a first opening cross-section of the purge gas control element (154, 156, 158, 160, 162, 164, 166) associated with the regenerator chamber (42, 44, 46, 48, 50, 52, 54); and iv. burnout gas is introduced into the burnout gas line (92) from a regenerator chamber (42, 44, 46, 48, 50, 52, 54) of a seventh of the regenerators (30, 32, 34, 36, 38, 40, 41) into the burnout gas line (92) at a second opening cross-section of the gas flow control element (110, 112, 114, 116, 118, 120, 122), associated with the regenerator chamber (42, 44, 46, 48, 50, 52, 54), which second opening cross-section is reduced with respect to the first opening cross-section.

14. System according to claim 13, characterized in that the control device (136, 136') controls the crude gas shut-off elements (64, 66, 68, 70, 72, 74, 75) and the clean gas shut-off elements (76, 78, 80, 82, 84, 86, 88) as well as the purge gas control elements (154, 156, 158, 160, 162, 164, 166) in a maintenance operation, in which over a defined time interval i. crude gas is fed to the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of a first, third and sixth regenerator of the regenerators (30, 32, 34, 36, 38, 40, 41) from the crude gas line (60), ii. clean gas is introduced into the clean gas line (62) from the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of a second and fourth regenerator of the regenerators (30, 32, 34, 36, 38, 40, 41), and iii. the regenerator chamber (42, 44, 46, 48, 50, 52, 54) of a seventh of the regenerators (30, 32, 34, 36, 38, 40, 41) is separated from the crude gas line (60) and from the clean gas line (62) as well as from the purge gas line (138, 138').

15. System according to either claim 13 or claim 14, characterized in that in six consecutive time intervals the fifth of the regenerators (30, 32, 34, 36, 38, 40, 41) is different and the seventh of the regenerators (30, 32, 34, 36, 38, 40, 41) is identical, preferably the seventh of the regenerators (30, 32, 34, 36, 38, 40, 41) being different in seven consecutive time intervals.

16. System according to any of claims 8 to 15, characterized in that each purge gas control element (154, 156, 158, 160, 162, 164, 166) makes it possible to adjust different opening cross-sections for the passage of purge gas.

17. System according to any of claims 1 to 16, characterized in that an adjustable shut-off element (126) is arranged in the crude gas line (60), which device releases or prevents the feed of crude gas into the regenerator chambers (42, 44, 46, 48, 50, 52, 54).

18. System according to claim 17, characterized by a crude gas bypass line (128) connected to a stack (28), which bypass line communicates with the crude gas line (60) at a crude gas line connection point (130) arranged on a side of the shut-off element (126) facing the filter device.

19. System according to claim 18, characterized in that, a crude gas feed fan (132) is arranged in the crude gas line (60) on a side of the crude gas line connection point (130), which faces away from the filter device, for the crude gas bypass line (128), which fan is for feeding crude gas into the regenerator chambers (42, 44, 46, 48, 50, 52, 54) of the regenerators (30, 32, 34, 36, 38, 40, 41) through the crude gas line (60), which has a pressure side facing the regenerator chambers (42, 44, 46, 48, 50, 52, 54), the purge gas line (138, 138') being preferably connected to the crude gas line (60) between the crude gas feed fan (132) and the shut-off element (126).

20. System according to either claim 18 or claim 19, characterized in that a crude gas feed fan (134) for conveying crude gas through the crude gas line (60) from the filter device is arranged in the crude gas line (60) on a side of the crude gas line connection point (130) for the crude gas bypass line (128), the side of connection point facing the filter device, which fan has a suction side facing the filter device.

21. System according to any of claims 1 to 20, characterized by at least seven regenerator chambers (42, 44, 46, 48, 50, 52, 54).

22. Use of a system according to any of claims 1 to 21 for regenerative thermal oxidation of crude gas with nitrogen oxides.

23. Cement plant (10, 10') having a system according to any of claims 1 to 21.

24. Method for operating a system for treating crude gas by means of regenerative thermal oxidation, the system having a combustion chamber (29) and a plurality of regenerators (30, 32, 34, 36, 38, 40, 41) communicating with the combustion chamber (29) and each having a regenerator chamber (42, 44, 46, 48, 50, 52, 54) with a heat exchanger (56) arranged therein, in which alternately at least one of the regenerators (30, 32, 34, 36, 38, 40, 41) is purged with purge gas, crude gas is fed into at least two of the regenerators (30, 32, 34, 36, 38, 40, 41), clean gas is discharged from the regenerator chamber (42, 44, 46, 48, 50, 52, 54) of at least two of the regenerators (30, 32, 34, 36, 38, 40, 41), and the regenerator chamber (42, 44, 46, 48, 50, 52, 54) of at least one of the regenerators (30, 32, 34, 36, 38, 40, 41) is operated in a burnout operation, characterized in that the burnout gas released during the burnout operation of the regenerator chamber (42, 44, 46, 48, 50, 52, 54) of the at least one regenerator (30, 32, 34, 36, 38, 40, 41) is fed back into the crude gas to be treated and is filtered with the crude gas before being fed into the regenerators (30, 32, 34, 36, 38, 40, 41).