An acrylonitrile absorption tower tail gas treatment device

Abstract

This invention discloses an acrylonitrile absorption tower tail gas treatment device, comprising an absorption tower connected to a drying chamber, a booster compressor connected to a blower branch, a tail gas heat exchanger connected to an electric heater, an inlet temperature measuring instrument connected to an inlet temperature measuring instrument connected to a catalytic reactor, an outlet temperature measuring instrument connected to an online flue gas oxygen content analyzer, a steam superheater connected to a waste heat boiler, and an SCR reactor. This device can dynamically optimize and control online to ensure that the removal rates of acrylonitrile and non-methane total hydrocarbons are both greater than 97%, meeting the standards of the Ministry of Environmental Protection and creating conditions for emission reduction.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas treatment technology, and specifically to an acrylonitrile absorption tower exhaust gas treatment device. Background Technology

[0002] Acrylonitrile is an important monomer for synthetic fibers, synthetic rubber, and synthetic resins, and therefore is produced in large quantities. The raw materials for acrylonitrile production are propylene, liquid ammonia, and air. These react in a reactor with a catalyst to produce acrylonitrile as the main product, releasing a large amount of heat. The gas exiting the reactor contains the target product, acrylonitrile, as well as water, nitrogen, oxygen, ammonia, propylene, propane, and acetonitrile. Therefore, an absorption tower is needed to absorb the tail gas. However, existing absorption towers have poor absorption capacity, making it difficult to meet emission standards. Summary of the Invention

[0003] The purpose of this invention is to provide an acrylonitrile absorption tower tail gas treatment device to solve the problems mentioned in the background art. To achieve the above objectives, the present invention provides the following technical solution: an acrylonitrile absorption tower tail gas treatment device, comprising an absorption tower, the absorption tower connected to a drying chamber, the drying chamber connected to a booster compressor, the booster compressor connected to a blower branch, the blower branch connected to a tail gas heat exchanger, the tail gas heat exchanger connected to an electric heater, the electric heater connected to an inlet gas temperature measuring instrument, the inlet gas temperature measuring instrument connected to a catalytic reactor, the catalytic reactor connected to an outlet gas temperature measuring instrument, the outlet gas temperature measuring instrument connected to an online flue gas oxygen content analyzer, the online flue gas oxygen content analyzer connected to a steam superheater, the steam superheater connected to a waste heat boiler, the waste heat boiler connected to an SCR reactor, the SCR reactor connected to an ammonia flow measuring instrument and a tail gas heat exchanger, the ammonia flow measuring instrument connected to a control valve, the control valve connected to an ammonia supply end, the ammonia flow measuring instrument and the control valve signal connected to an SCR ammonia flow and excess ammonia quantity β optimization control module, and the tail gas heat exchanger connected to an online flue gas ammonia content analyzer. The online flue gas ammonia content analyzer is connected to the chimney and the flue gas circulation fan. The signal from the online flue gas ammonia content analyzer is connected to the SCR ammonia flow and excess ammonia quantity β optimization control module. The flue gas circulation fan is connected to control valve I. Control valve I is connected to a gas flow meter. The gas flow meter is connected to the output end of the blower branch. The signal from control valve I and the gas flow meter is connected to the CO catalytic oxidation reactor inlet and outlet temperature optimization control module. The signal from the CO catalytic oxidation reactor inlet and outlet temperature optimization control module is connected to the inlet air temperature meter and the outlet air temperature meter. The online flue gas oxygen content analyzer is connected to the mixed air flow and flue gas emission excess air coefficient α optimization control module. The mixed air flow and flue gas emission excess air coefficient α optimization control module is connected to the blower branch and the feedforward optimization control module. The feedforward optimization control module is connected to the CO catalytic oxidation reactor inlet and outlet temperature optimization control module and the SCR ammonia flow and excess ammonia quantity β optimization control module.

[0004] Preferably, the blower branch includes a blower, the blower is connected to control valve II, control valve II is connected to an air flow meter, the air flow meter is connected to the output end of the booster, and the air flow meter and control valve II are signal-connected to the mixed air flow and flue gas emission air excess coefficient α optimization control function module.

[0005] Preferably, a control valve III is connected between the input and output ends of the waste heat boiler, and the control valve III is signal-connected to the CO catalytic oxidation reactor inlet and outlet temperature optimization control module.

[0006] Preferably, an online exhaust gas analyzer is installed on the pipe at the inlet end of the exhaust gas heat exchanger. The online exhaust gas analyzer is connected to the feedforward optimization control module. The online exhaust gas analyzer includes an exhaust gas flow meter, an online exhaust gas chromatograph, and an online exhaust gas infrared analyzer.

[0007] Preferably, the mixed air flow rate and flue gas emission excess air coefficient α optimization control function module is equipped with an excess coefficient α. The excess coefficient α refers to the oxygen content coefficient in the tail gas after the catalytic reactor reaction, and its expression is α=21 / (21-online flue gas oxygen content analyzer measurement value).

[0008] Preferably, the SCR ammonia flow rate and excess ammonia amount β optimization control module has an excess ammonia amount β, which refers to the ammonia content of flue gas emitted into the atmosphere of the chimney.

[0009] The technical effects and advantages of this invention are as follows: This device uses an online analyzer to perform dynamic model calculations on acrylonitrile, non-methane total hydrocarbons, nitrogen oxides, oxygen content, and ammonia content in the exhaust gas, and uses concentration (molecular weight) as a feedforward feedback quantity for series control; the dynamic online optimization control ensures that the resolution rate of acrylonitrile and non-methane total hydrocarbons is greater than 97%, meeting the standards of the Ministry of Environmental Protection of China, thus creating conditions for emission reduction; it also solves the problem of ammonia leakage in the flue gas, achieving a level of less than 2.5 ppm, which meets the national environmental protection standards. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of the present invention.

[0011] In the diagram: 1-Absorption tower, 2-Drying chamber, 3-Booster, 4-Blower, 5-Control valve II, 6-Air flow meter, 7-Optimization control module for mixed air flow and excess air coefficient α in flue gas emissions, 8-Tail gas heat exchanger, 9-Electric heater, 10-Inlet air temperature meter, 11-Catalytic reactor, 12-Outlet air temperature meter, 13-Online flue gas oxygen content analyzer, 14-Steam superheater, 15-Waste heat boiler, 16-SCR reactor, 17-Ammonia flow rate Measuring instrument, 18-Control valve III, 19-Control valve, 20-SCR ammonia flow and excess ammonia β optimization control module, 21-Online flue gas ammonia content analyzer, 22-Chimney, 23-Flue gas circulation fan, 24-Control valve I, 25-Gas flow meter, 26-CO catalytic oxidation reactor inlet and outlet temperature optimization control module, 27-Feedforward optimization control module, 28-Tail gas flow meter, 29-Tail gas online gas chromatograph, 30-Tail gas online infrared analyzer. Detailed Implementation

[0012] To make the technical means, creative features, objectives and effects of the present invention easier to understand, the present invention will be further described below with reference to specific illustrations. In the description of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation", "connection" and "connection" should be interpreted broadly. For example, they can be fixed connections, detachable connections, integral connections, mechanical connections, or electrical connections; they can be direct connections or indirect connections through an intermediate medium; and they can be internal connections between two components.

[0013] Example

[0014] like Figure 1The acrylonitrile absorption tower tail gas treatment device shown includes an absorption tower 1, a drying chamber 2 connected to the absorption tower 1, a booster compressor 3 connected to the drying chamber 2, a blower branch connected to the booster compressor 3, a blower branch including a blower 4, a control valve II 5 connected to a control valve II 5 connected to an air flow meter 6, and the air flow meter 6 connected to the output of the booster compressor 3. The air flow meter 6 and the control valve II 5 are signal-connected to a mixed air flow and flue gas exhaust air excess coefficient α optimization control function module 7. The output of the booster compressor 3 is connected to a tail gas heat exchanger 8, the tail gas heat exchanger 8 is connected to an electric heater 9, the electric heater 9 is connected to an inlet air temperature meter 10, and the inlet air temperature meter 10 is connected to a catalytic reactor 11. The catalytic reactor 1... 1. Connect the outlet gas temperature measuring instrument 12. The outlet gas temperature measuring instrument 12 is connected to the online flue gas oxygen content analyzer 13. The online flue gas oxygen content analyzer 13 is connected to the steam superheater 14. The steam superheater 14 is connected to the waste heat boiler 15. The waste heat boiler 15 is connected to the SCR reactor 16. The SCR reactor 16 is connected to the ammonia flow measuring instrument 17 and the tail gas heat exchanger 8. The ammonia flow measuring instrument 17 is connected to the control valve 19. The control valve 19 is connected to the ammonia supply end. The ammonia flow measuring instrument 17 and the control valve 19 are connected to the SCR ammonia flow and excess ammonia amount β optimization control module 20. The tail gas heat exchanger 18 is connected to the online flue gas ammonia content analyzer 21. The online flue gas ammonia content analyzer 21 is connected to the chimney 22 and the flue gas circulation fan 23. The online flue gas ammonia content analyzer 21 is connected to the SCR ammonia flow and excess ammonia amount β optimization control module 20. The flue gas circulation fan 23 is connected to control valve I 24. Control valve I 24 is connected to gas flow meter 25. Gas flow meter 25 is connected to the output end of the blower branch. Gas flow meter 25 and control valve I 24 are connected to the CO catalytic oxidation reactor inlet and outlet temperature optimization control module 26. CO catalytic oxidation reactor inlet and outlet temperature optimization control module 26 is connected to the inlet air temperature meter 10 and outlet air temperature meter 12. The online flue gas oxygen content analyzer 13 is connected to the mixed air flow and flue gas emission excess air coefficient α optimization control function module 7. Mixed air flow and flue gas emission... The excess air coefficient α optimization control module 7 is connected to the feedforward optimization control module 27. The feedforward optimization control module 27 is connected to the CO catalytic oxidation reactor inlet and outlet temperature optimization control module 26 and the SCR ammonia flow and excess ammonia amount β optimization control module 20. A control valve Ⅲ 28 is connected between the input and output ends of the waste heat boiler 15. The signal of the control valve Ⅲ 28 is connected to the CO catalytic oxidation reactor inlet and outlet temperature optimization control module 26. An online exhaust gas analyzer is installed on the pipe at the inlet end of the exhaust gas heat exchanger 18. The signal of the online exhaust gas analyzer is connected to the feedforward optimization control module 27. The online exhaust gas analyzer includes an exhaust gas flow meter 28, an online exhaust gas gas chromatograph 29, and an online exhaust gas infrared analyzer 30.

[0015] When the device treats acrylonitrile production tail gas, the tail gas entering the suction tower 1 absorbs moisture from the tail gas through the drying box 2. The dried tail gas then passes through a tail gas flow meter 28, an online tail gas chromatograph 29, and an online tail gas infrared analyzer 30. The tail gas flow meter 28 calculates the tail gas flow rate; the online tail gas chromatograph 29 detects the concentration of acrylonitrile and non-methane total hydrocarbons online and calculates the molecular weight and average molecular weight of each component; the online tail gas infrared analyzer 30 detects the concentration and molecular weight of nitrogen oxides in the tail gas online; the feedforward optimization control module 27 acquires the data detected by the tail gas flow meter 28, the online tail gas chromatograph 29, and the online tail gas infrared analyzer 30, and transmits them to the CO catalytic oxidation reactor inlet and outlet temperature optimization control module 26, the mixed air flow and flue gas emission excess air coefficient α optimization control module 7, and the SCR ammonia flow and excess ammonia amount β optimization control module 20, respectively.

[0016] The CO catalytic oxidation reactor inlet and outlet temperature optimization control module 26 calculates the setpoints SP for the reactor inlet and outlet temperatures of the catalytic reactor 11 based on the molecular weights of acrylonitrile and non-methane hydrocarbons using a mathematical model. SP varies with the molecular weights of acrylonitrile and non-methane hydrocarbons. While ensuring a reduction rate of acrylonitrile and non-methane hydrocarbons greater than 97%, the module analyzes the temperature ranges for the reactor inlet and outlet temperatures based on the molecular weights of acrylonitrile, non-methane hydrocarbons, and oxygen concentration, and sets upper and lower limits. Within the obtained temperature range, the catalytic reactor... The oxygen content inside the exhaust gas discharged from 11 needs to meet the internal setting of the mixed air flow and flue gas emission excess air coefficient α optimization control function module 7. Then, the acrylonitrile, non-methane total hydrocarbon molecular weight and oxygen concentration in the exhaust gas are adjusted by blower 4 and control valve II 5, flue gas circulation fan 23 and control valve I 24 to make the set value SP within the analyzed temperature range. Then, the exhaust gas is heated to the specified temperature by exhaust gas heat exchanger 8 and electric heater 9 and enters catalytic reactor 11 for reaction. Temperature feedback is obtained by inlet air temperature measuring instrument 10 and outlet air temperature measuring instrument 12.

[0017] After the exhaust gas reacts in the catalytic reactor 11, the oxygen content in the exhaust gas after the reaction is detected by an online flue gas oxygen content analyzer 13. The test results are fed back to the mixed air flow and flue gas emission excess air coefficient α optimization control module 7. The oxygen content should meet the excess coefficient α setting inside the mixed air flow and flue gas emission excess air coefficient α optimization control module 7 (α=21 / (21-online flue gas oxygen content analyzer measurement value), α is set between 1.05 and 1.1). If the amount of air in the exhaust gas in the catalytic reactor 11 is insufficient, the reaction will be incomplete, resulting in excessive exhaust gas emissions. If the amount of air is too large, the organic matter concentration will be too low, which will also lead to incomplete reaction.

[0018] The exhaust gas undergoes temperature regulation via a steam superheater 14 and a waste heat boiler 15 before entering the SCR reactor 16. Simultaneously, the SCR ammonia flow rate and excess ammonia amount β optimization control module 20 obtains the concentration (molecular weight) of nitrogen oxides in the exhaust gas detected online by the exhaust gas online infrared analyzer 30. The theoretical ammonia flow rate is calculated through a mathematical model and set as dynamic SP. The SCR ammonia flow rate and excess ammonia amount β optimization control module 20 also has an excess ammonia amount β, which is the data measured by the online flue gas ammonia content analyzer 21. Then, the SCR ammonia flow rate and excess ammonia amount β optimization control module 20 controls the inflow of ammonia through an ammonia flow meter 17 and a control valve 19. The inflow rate is dynamic SP + excess ammonia amount β, where the excess ammonia amount β is less than 2.5 ppm, thereby achieving a reduction rate of acrylonitrile and non-methane total hydrocarbons greater than 97%.

[0019] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An acrylonitrile absorption tower tail gas treatment device, comprising an absorption tower, characterized in that: The absorption tower is connected to a drying chamber, the drying chamber is connected to a booster compressor, the booster compressor is connected to a blower branch, the blower branch is connected to a tail gas heat exchanger, the tail gas heat exchanger is connected to an electric heater, the electric heater is connected to an inlet air temperature measuring instrument, the inlet air temperature measuring instrument is connected to a catalytic reactor, the catalytic reactor is connected to an outlet air temperature measuring instrument, the outlet air temperature measuring instrument is connected to an online flue gas oxygen content analyzer, the online flue gas oxygen content analyzer is connected to a steam superheater, the steam superheater is connected to a waste heat boiler, and the waste heat boiler is connected to an SCR (Self-Conducting Refrigerant Detector). The reactor, the SCR reactor, is connected to an ammonia flow meter and a tail gas heat exchanger. The ammonia flow meter is connected to a control valve, which is connected to the ammonia supply end. The ammonia flow meter and control valve signals are connected to the SCR ammonia flow and excess ammonia quantity β optimization control module. The tail gas heat exchanger is connected to an online flue gas ammonia content analyzer. The online flue gas ammonia content analyzer is connected to a chimney and a flue gas circulation fan. The online flue gas ammonia content analyzer signals are connected to the SCR ammonia flow and excess ammonia quantity β optimization control module. The flue gas circulation fan... The system is connected to control valve I, which is connected to a gas flow meter. The gas flow meter is connected to the output end of the blower branch. The control valve I and the gas flow meter are connected to the CO catalytic oxidation reactor inlet and outlet temperature optimization control module. The CO catalytic oxidation reactor inlet and outlet temperature optimization control module is connected to the inlet air temperature meter and the outlet air temperature meter. The online flue gas oxygen content analyzer is connected to the mixed air flow and flue gas emission excess air coefficient α optimization control function module. The mixed air flow and flue gas emission excess air coefficient α optimization control function module is connected to the blower branch and the feedforward optimization control module. The feedforward optimization control module is connected to the CO catalytic oxidation reactor inlet and outlet temperature optimization control module and the SCR ammonia flow and excess ammonia amount β optimization control module. An online exhaust gas analyzer is installed on the pipe at the inlet end of the exhaust gas heat exchanger. The online exhaust gas analyzer is connected to the feedforward optimization control module. The online exhaust gas analyzer includes an exhaust gas flow meter, an online exhaust gas gas chromatograph, and an online exhaust gas infrared analyzer.

2. The acrylonitrile absorption tower tail gas treatment device according to claim 1, characterized in that: The blower branch includes a blower, which is connected to control valve II. Control valve II is connected to an air flow meter, which is connected to the output of the booster. The air flow meter and control valve II are signal-connected to the mixed air flow and flue gas emission air excess coefficient α optimization control function module.

3. The acrylonitrile absorption tower tail gas treatment device according to claim 1, characterized in that: A control valve III is connected between the input and output ends of the waste heat boiler. The control valve III signal is connected to the inlet and outlet temperature optimization control module of the CO catalytic oxidation reactor.

4. The acrylonitrile absorption tower tail gas treatment device according to claim 1, characterized in that: The mixed air flow rate and flue gas emission excess air coefficient α optimization control function module has an excess coefficient α inside. The excess coefficient α refers to the oxygen content coefficient in the tail gas after the reaction of the catalytic reactor, and its expression is α=21 / (21-online flue gas oxygen content analyzer measurement value).

5. The acrylonitrile absorption tower tail gas treatment device according to claim 1, characterized in that: The SCR ammonia flow rate and excess ammonia amount β optimization control module has an excess ammonia amount β inside, which refers to the ammonia content of flue gas emitted into the atmosphere of the chimney.

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