Equipment and method for reducing contents of nitrogen and oxygen in RTO furnace outlet waste gas

Abstract

The invention relates to the technical field of chemical production waste gas RTO treatment, in particular to a device and method for reducing the content of nitrogen and oxygen in RTO furnace outlet waste gas, and the device comprises a waste gas pipe network, a waste gas mixing device, an RTO furnace, a tail gas mixer, a quench tower and a lower-stage tail gas recovery device which are connected in sequence. The combustion engine is connected with a natural gas pipe network and a combustion-supporting gas pipe network, the RTO furnace comprises three heat storage chambers, the bottom of each heat storage chamber is connected with an inlet pipeline, an extraction pipeline and an outlet pipeline, the extraction pipelines are jointly connected with an extraction fan, and the extraction fan is connected with an exhaust fan. An outlet of the extraction fan is connected with the inlet pipeline, the inlet pipeline is connected with an outlet of the mixing device, and the outlet pipeline is connected with an inlet of the tail gas mixer.The device has the following beneficial effects that introduction of air into equipment is reduced, and the content of nitrogen and oxygen in tail gas is reduced.

Description

Technical Field

[0001] This invention relates to the field of RTO (Regenerative Thermal Oxidizer) treatment technology for chemical production waste gas, and particularly to a device and method for reducing the nitrogen and oxygen content in the exhaust gas from an RTO furnace. Background Technology

[0002] RTO (Regenerative Thermal Oxidizer) furnaces are highly efficient devices for treating organic waste gases. They are mainly used to remove organic components from waste gases. By recycling heat through a heat storage medium, they can significantly reduce energy consumption while achieving a high purification rate.

[0003] Conventional RTO furnaces require air replenishment at multiple stages during operation. For example, during the exhaust gas intake stage, exhaust gas needs to be mixed with air to form a mixed exhaust gas, ensuring that the oxygen content in the mixed exhaust gas meets the standards. The burner of the RTO furnace typically uses air for purging. The bottom valve of the RTO furnace generally uses air as the valve sealing gas. After the exhaust gas is purified, a large amount of nitrogen and oxygen from the air are present in the exhaust gas, especially the nitrogen content, which is very high.

[0004] Currently, RTO furnace exhaust gas is typically emitted directly from the chimney, with little concern regarding its nitrogen and oxygen content. A chemical plant, introducing a carbon dioxide production unit, aims to recover and utilize the RTO furnace exhaust gas to achieve energy conservation, emission reduction, and lower production costs. Therefore, controlling the nitrogen and oxygen content is necessary. Consequently, current conventional RTO furnaces are not conducive to the further recovery and utilization of exhaust gas, and existing technologies lack methods for controlling the nitrogen and oxygen content in the exhaust gas. Summary of the Invention

[0005] The purpose of this invention is to provide a device for reducing the nitrogen and oxygen content in the exhaust gas from an RTO furnace, which can effectively reduce the nitrogen and oxygen content in the exhaust gas from the RTO furnace, especially the nitrogen content.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a device for reducing the nitrogen and oxygen content in the exhaust gas from an RTO furnace, comprising, in sequence, an exhaust gas pipeline network, an exhaust gas mixing device, an RTO furnace, a tail gas mixer, a quench tower, and a downstream tail gas recovery device; the RTO furnace is equipped with a burner connected to a natural gas pipeline network and a combustion-supporting pipeline network; and further comprising:

[0007] The oxygen pipeline network, together with the waste gas pipeline network, is connected to the waste gas mixing device;

[0008] The burner purging pipeline has one end connected to the outlet of the quench tower and the other end connected to the burner, and is used to purge the burner.

[0009] The RTO furnace includes three regenerator chambers. The bottom of each regenerator chamber is connected to an inlet pipeline, an extraction pipeline, and an outlet pipeline. The extraction pipeline is connected to an extraction fan. The outlet of the extraction fan is connected to the inlet pipeline. The inlet pipeline is connected to the outlet of the mixing device. The outlet pipeline is connected to the inlet of the tail gas mixer. Valves are installed on the inlet pipeline, the extraction pipeline, the outlet pipeline, and the outlet pipeline of the mixed gas-liquid separator.

[0010] Preferably, the waste gas mixing device is equipped with an online oxygen concentration detector, and a quick-cut valve is installed on the outlet pipeline of the oxygen pipeline network. The online oxygen concentration detector interlocks with and controls the quick-cut valve.

[0011] Preferably, the waste gas mixing device includes a waste gas mixer and a mixed gas-liquid separator connected in sequence, and the bottom of the waste gas mixer and the mixed gas-liquid separator are connected to a wastewater discharge pump and a wastewater pipeline.

[0012] Preferably, the gas phase outlet of the gas-liquid separator is connected to a flame arrester.

[0013] Preferably, the burner includes burner one and burner two, with one on and one on standby.

[0014] Another object of the present invention is to provide a method for reducing the nitrogen and oxygen content in the exhaust gas from an RTO furnace, comprising the following steps:

[0015] Step 1: Mix the waste gas to be treated with pure oxygen to form a mixed waste gas;

[0016] Step 2: Separate the mixed waste gas into liquid and gas phases. The separated liquid phase is discharged into the wastewater network, while the gas phase is transported to the RTO furnace.

[0017] Step 3: The RTO furnace purifies the mixed waste gas and uses the existing waste gas as the valve sealing gas for the RTO furnace;

[0018] Step four: After cooling the purified exhaust gas, part of it is sent to the next stage of treatment, and the other part is used as purging gas for the backup burner.

[0019] Preferably, in step one, the intake of pure oxygen is adjusted in real time to maintain the oxygen content in the mixed exhaust gas at a preset value.

[0020] Preferably, the three regenerator chambers of the RTO furnace are regenerator chamber A, regenerator chamber B, and regenerator chamber C, and step three is carried out in the following three working stages:

[0021] In the first stage, heat storage chamber A is used to heat and introduce the waste gas to be purified, heat storage chamber B is used to cool and discharge the purified waste gas, and the waste gas that is not discharged in heat storage chamber C is transported to the bottom of heat storage chamber A as valve sealing gas.

[0022] In Phase Two, the process switches to heating the exhaust gas to be purified in heat storage chamber B, cooling the exhaust gas in heat storage chamber C, and discharging the purified exhaust gas. The exhaust gas that is not completely discharged in heat storage chamber A is transported to the bottom of heat storage chamber B and used as valve sealing gas.

[0023] In Phase 3, the process switches to heating the exhaust gas to be purified in heat storage chamber C, cooling and discharging the purified exhaust gas in heat storage chamber A, and transporting any remaining exhaust gas in heat storage chamber B to the bottom of heat storage chamber C for use as valve sealing gas.

[0024] In summary, the present invention has the following beneficial effects:

[0025] In the waste gas treatment process, pure oxygen is used instead of traditional air as the reaction gas source, reducing the nitrogen content. The treated waste gas is used as valve sealing gas instead of air, further reducing nitrogen and oxygen content. This sealing gas is then drawn to the RTO furnace inlet for reprocessing. Cooled tail gas is used as backup burner purging gas, replacing traditional air, reducing air introduction and further lowering nitrogen and oxygen content. Actual production verification shows that this process can reduce the oxygen content in the treated gas from 8% to 3%, and the nitrogen content from the initial 10% to a significant reduction to 2.5%. From an economic perspective, the subsequent extraction of food-grade carbon dioxide from the carbon dioxide waste gas can be increased from 230 t / d to 260 t / d. Based on current market conditions, applying this technology can increase the revenue of the carbon dioxide plant by 1.95 million yuan per year. Furthermore, this technology significantly reduces carbon dioxide emissions during operation, offering both environmental and social benefits and demonstrating significant application value. Attached Figure Description

[0026] Figure 1 This is a schematic diagram showing the connection relationships of the various devices in this equipment.

[0027] In the diagram, 1. Natural gas pipeline; 2. Combustion air; 3. RTO furnace; 31. Burner 1; 32. Burner 2; 4. Oxygen pipeline; 5. Exhaust gas pipeline; 6. Exhaust gas mixer; 7. Mixed gas-liquid separator; 8. Flame arrester; 9. Wastewater discharge pump; 10. Extraction fan; 12. Tail gas mixer; 13. Quenching tower; 14. Burner purge gas pipeline; 15. Dilute air pipeline; 16. Wastewater pipeline; 17. Exhaust gas pipeline; 18. Mixed exhaust gas pipeline; 19. Quick-cut valve; 20. Conveying fan; 21. Lower-stage tail gas recovery device; 22. Inlet pipeline; 23. Extraction pipeline; 24. Outlet pipeline. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings.

[0029] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

[0030] like Figure 1 As shown, burner 31 and burner 32 are installed on the top of the RTO furnace 3, one in operation and one on standby. Burner 31 and burner 32 are connected to a burner purge gas line 14, which is used to draw purified gas to purge the burners, replacing the traditional method of using ordinary air for purging. Since air contains nitrogen and oxygen, while the purified exhaust gas has low oxygen and nitrogen content, the nitrogen and oxygen content in the exhaust gas emitted by the RTO furnace 3 is reduced. Burner 31 and burner 32 are also connected to a natural gas pipeline 1 and a combustion air pipeline 2.

[0031] The exhaust gas pipeline 5 in the equipment is connected to the exhaust gas mixer 6 via exhaust gas pipeline 17. An online oxygen concentration detector and a temperature detector are installed at the outlet of the exhaust gas mixer 6 to monitor the oxygen content and exhaust gas temperature at the outlet. An oxygen pipeline 4 is connected to the exhaust gas pipeline 17. The connection between the oxygen pipeline 4 and the exhaust gas pipeline 17 uses an annular mixer with diffuser holes. A quick-cut valve 19 is installed on the pipeline between the oxygen pipeline 4 and the exhaust gas pipeline 17. This quick-cut valve 19 is electrically connected to the aforementioned online oxygen concentration detector, which interlocks with the quick-cut valve 19. In this technical solution, the oxygen pipeline 4 provides pure oxygen, replacing the dilution air in traditional solutions, thus reducing the nitrogen content in the exhaust gas. It should be noted that in this solution, the interlocking control between the online oxygen concentration detector and the quick-cut valve 19 maintains the oxygen concentration in the mixed exhaust gas at a level consistent with that in traditional methods, while the nitrogen concentration in the mixed exhaust gas is significantly lower than in traditional methods. The exhaust gas mixer 6 is connected to the gas-liquid separator 7 via the gas-liquid separator pipeline 18. The bottoms of the exhaust gas mixer 6 and the gas-liquid separator 7 are connected to the wastewater discharge pump 9 via the waste liquid pipeline, and are connected to the wastewater pipeline network 16.

[0032] The gas-liquid separator 7 is connected to the RTO furnace 3 via a flame arrester 8. The RTO furnace 3 is a three-chamber combustion furnace. Each regenerator chamber has an inlet pipeline 22, an extraction pipeline 23, and an outlet pipeline 24 connected to its bottom. Each pipeline is equipped with a valve for controlling its opening and closing. The gas-liquid separator 7 is connected to the inlet pipeline 22 of each regenerator chamber, allowing the input of waste gas to be treated into a specific regenerator chamber during different operating stages of the RTO furnace 3. The three extraction pipelines 22 are connected to an extraction fan 10, the outlet of which is connected to each inlet pipeline 22. The outlet pipeline 24 is connected to the tail gas mixer 12. The tail gas from the RTO furnace 3 enters the extraction pipeline 23 and the outlet pipeline 24, with part of it being used as sealing gas by the extraction fan 10, and the rest being delivered to the tail gas mixer 12.

[0033] The exhaust gas mixer 12 is connected to the cooling tower 13. The cooling tower 13 is connected to the first burner 31 and the second burner 32 via the conveying fan 20. Part of the exhaust gas from the outlet of the conveying fan 20 is transported along the burner purging gas pipeline 14 for purging the burner. The exhaust gas is used to replace the air used in the traditional technical solution. The outlet of the conveying fan 20 is also connected to the lower-level exhaust gas recovery device 21. Other exhaust gas is transported to the lower-level exhaust gas recovery device 21 for treatment.

[0034] In actual operation, waste gas enters waste gas pipeline 17 from waste gas pipeline network 5, and oxygen enters waste gas pipeline 17 from oxygen pipeline network 4. Waste gas pipeline 17 connects to waste gas mixer 6 to form a mixed gas, which then enters mixed gas gas-liquid separator 7. After the liquid phase is separated, the gas phase passes through flame arrester 8 and enters RTO furnace 3, while the liquid phase in waste gas mixer 6 and mixed gas gas-liquid separator 7 is discharged to wastewater pipeline network 16.

[0035] In this specific embodiment, such as Figure 1 As shown, the RTO furnace 3 includes regenerator A, regenerator B, and regenerator C.

[0036] In the first working stage, heat storage chamber A is used to heat and introduce the waste gas to be purified, heat storage chamber B is used to cool and discharge the purified waste gas, and the waste gas that is not completely discharged in heat storage chamber C is transported to the bottom of heat storage chamber A as valve sealing gas. Specifically, the waste gas to be purified is introduced and heated from the inlet pipe 22 at the bottom of heat storage chamber A; the purified waste gas is discharged to the tail gas mixer 12 from the outlet pipe 24 at the bottom of heat storage chamber B, and the purified waste gas is cooled at the same time during this process; heat storage chamber C was used to heat and introduce the waste gas to be treated in the previous stage, and after switching to this working stage, there will still be purified waste gas remaining inside it. Under the action of the extraction fan 10, this waste gas to be purified enters the inlet pipe 22 at the bottom of heat storage chamber A through the extraction pipe 23 at its bottom, and is used as valve sealing gas to seal the valve at the bottom of heat storage chamber A.

[0037] In the second working stage, the process switches to heating and introducing the waste gas to be purified in heat storage chamber B, while heat storage chamber C cools and discharges the purified waste gas. The remaining waste gas in heat storage chamber A is transported to the bottom of heat storage chamber B and used as valve sealing gas. Specifically, the waste gas to be purified is introduced and heated through the inlet pipe 22 at the bottom of heat storage chamber B; the purified waste gas is discharged to the tail gas mixer 12 through the outlet pipe 24 at the bottom of heat storage chamber C, a process that simultaneously cools the purified waste gas. Heat storage chamber A, used in the previous stage to heat and introduce the waste gas to be treated, still retains purified waste gas after switching to this working stage. Under the action of the extraction fan 10, this purified waste gas enters the inlet pipe 22 at the bottom of heat storage chamber B through the extraction pipe 23 at its bottom, serving as valve sealing gas to seal the valve at the bottom of heat storage chamber B.

[0038] In the third working stage, the process switches to heating and introducing the waste gas to be purified in heat storage chamber C, while heat storage chamber A cools and discharges the purified waste gas. The remaining waste gas in heat storage chamber B is transported to the bottom of heat storage chamber C as valve sealing gas. Specifically, the waste gas to be purified is introduced and heated through the inlet pipe 22 at the bottom of heat storage chamber C; the purified waste gas is discharged to the tail gas mixer 12 through the outlet pipe 24 at the bottom of heat storage chamber A, a process that simultaneously cools the purified waste gas. Heat storage chamber B, used in the previous stage to heat and introduce the waste gas to be treated, still retains purified waste gas after switching to this working stage. Under the action of the extraction fan 10, this purified waste gas enters the inlet pipe 22 at the bottom of heat storage chamber C through the extraction pipe 23 at its bottom, serving as valve sealing gas to seal the valve at the bottom of heat storage chamber C.

[0039] The above three stages are repeated cyclically.

[0040] It should be clarified that valves are installed on all the above-mentioned pipelines. The direction of the exhaust gas in each pipeline is determined by the opening and closing of the valves. The opening and closing status of each valve can be determined by the direction of the exhaust gas in the pipeline, so it will not be described in detail here.

[0041] The exhaust gas to be purified enters the RTO furnace 3, is purified, and then enters the tail gas mixer 12. It then enters the quench tower 13 for cooling, and is subsequently conveyed by the conveying fan 20. Part of the tail gas is sent by the conveying fan 20 to the downstream tail gas recovery device 21, while the other part is conveyed by the conveying fan 20 to burner 31 and burner 32, where one of the burners in standby mode is purged. The purged exhaust gas then enters the RTO furnace 3, is purified again, and is discharged from the outlet pipeline 24.

[0042] Example:

[0043] Taking the reaction of this device as an example, the composition of the waste gas pipeline 5 is CO2:H2O:organic matter in a mass ratio of 90%:6%:4%, totaling 40t / h. Waste gas containing carbon dioxide enters the waste gas mixer 6 from the waste gas pipeline 5, and pure oxygen enters from the oxygen pipeline 4. In the waste gas mixer 6, the waste gas undergoes preliminary gas-liquid phase separation, transforming into a mixed waste gas. An online oxygen concentration detector and a temperature detector at the outlet of the waste gas mixer 6 monitor the temperature and oxygen content of the mixed waste gas. The oxygen content is controlled by a quick-cut valve 19 interlocked with the online oxygen concentration detector. Then, the mixed waste gas enters the gas-liquid separator 7 for further gas-liquid separation. The separated waste liquid is sent to the waste liquid pipeline 16, and the mixed waste gas is sent to the RTO furnace 3 for purification via a flame arrester 8. The mixed waste gas is preheated in RTO furnace 3, then purified in the furnace chamber. A portion of the waste gas from RTO furnace 3 outlet is sent to purge the furnace chamber. The purified waste gas enters tail gas mixer 12, then cooling tower 13, and is subsequently conveyed by conveying fan 20. Part of the tail gas is sent to downstream devices, while the remaining tail gas enters burner 1 31 and burner 2 32 via burner purge gas pipeline 14 as burner purge gas. Actual measurements show that after stable operation, the oxygen volume content in the carbon dioxide waste gas emitted by RTO furnace 3 is less than 3.5%, and the nitrogen volume content is less than 3%.

Claims

1. An apparatus for reducing the nitrogen and oxygen content in the exhaust gas from an RTO furnace, comprising, in sequence, an exhaust gas pipeline network (5), an exhaust gas mixing device, an RTO furnace (3), a tail gas mixer (12), a quench tower (13), and a downstream tail gas recovery device (21), wherein the RTO furnace (3) is equipped with a burner, and the burner is connected to a natural gas pipeline network (1) and a combustion-supporting pipeline network, characterized in that, Also comprising: an oxygen pipe network (4) connected to the exhaust gas mixing device together with the exhaust gas pipe network (5); a combustion engine purging pipeline, one end of which is connected to the outlet of the quench tower (13), and the other end of which is connected to the combustion engine, for purging the combustion engine; The RTO furnace (3) comprises three regenerative chambers, and the bottom of each regenerative chamber is respectively connected with an inlet pipeline (22), an exhaust pipeline (23), and an outlet pipeline (24). The exhaust pipelines (23) are commonly connected with an exhaust fan (10), the outlet of which is connected with the inlet pipeline (22), the inlet pipeline (22) is connected with the outlet of the mixing device, the outlet pipeline (24) is connected with the inlet of the exhaust gas mixer (12), and valves are arranged on the inlet pipeline (22), the exhaust pipeline (23), the outlet pipeline (24), and the outlet pipeline (24) of the mixed gas gas-liquid separation tank (7).

2. The apparatus for reducing the content of nitrogen and oxygen in the exhaust gas at the outlet of the RTO furnace according to claim 1, characterized in that, An online oxygen concentration detector is arranged in the exhaust gas mixing device, and a quick cut valve (19) is arranged on the outlet pipeline (24) of the oxygen pipe network (4), and the online oxygen concentration detector is used to interlock control the quick cut valve (19).

3. The apparatus of claim 1, wherein the apparatus further comprises a nitrogen and oxygen content reduction device. The exhaust gas mixing device comprises an exhaust gas mixer (6) and a mixed gas gas-liquid separation tank (7) connected in sequence, and the bottoms of the exhaust gas mixer (6) and the mixed gas gas-liquid separation tank (7) are commonly connected with a wastewater discharge pump (9) and a wastewater pipe network (16).

4. The apparatus for reducing the content of nitrogen and oxygen in the exhaust gas at the outlet of the RTO furnace according to claim 3, characterized in that, The gas phase outlet of the mixed gas gas-liquid separation tank (7) is connected with a flame arrester (8).

5. The apparatus of claim 1, wherein the apparatus further comprises a nitrogen and oxygen content reduction device. The combustion engine comprises a combustion engine one (31) and a combustion engine two (32), and one of them is in operation and the other is in standby.

6. A method of reducing the nitrogen and oxygen content of the exhaust gas at the outlet of an RTO furnace, characterized in that, The method comprises the following steps: Step one, mixing the exhaust gas to be treated with pure oxygen to form mixed exhaust gas; Step two, carrying out gas-liquid separation on the mixed exhaust gas, discharging the separated liquid phase to the wastewater pipe network (16), and conveying the gas phase to the RTO furnace (3); Step three, purifying the mixed exhaust gas by the RTO furnace (3), and using the existing exhaust gas as the valve sealing gas of the RTO furnace (3); Step four, after cooling and temperature reduction of the purified exhaust gas, part of it is conveyed to the next stage of treatment, and the other part is used as the purging gas of the standby combustion engine.

7. The method of claim 6, wherein the method further comprises, In step one, the inlet amount of pure oxygen is controlled in real time, so that the oxygen content in the mixed exhaust gas is kept at a preset value.

8. The method of claim 6, wherein the method further comprises, The three regenerative chambers of the RTO furnace (3) are regenerative chamber A, regenerative chamber B, and regenerative chamber C, and step three is carried out in the following three working stages: Stage one, regenerative chamber A is used for heating and introducing the exhaust gas to be purified, regenerative chamber B is used for cooling and discharging the purified exhaust gas, and the exhaust gas not discharged in regenerative chamber C is conveyed to the bottom of regenerative chamber A as valve sealing gas; Stage two, switching to heating and introducing the exhaust gas to be purified by regenerative chamber B, cooling and discharging the purified exhaust gas by regenerative chamber C, and conveying the exhaust gas not discharged in regenerative chamber A to the bottom of regenerative chamber B as valve sealing gas; Stage three, switching to heating and introducing the exhaust gas to be purified by regenerative chamber C, cooling and discharging the purified exhaust gas by regenerative chamber A, and conveying the exhaust gas not discharged in regenerative chamber B to the bottom of regenerative chamber C as valve sealing gas.

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