A high operational flexibility nitrogen oxide pressurized absorption device and method

Abstract

The application discloses a high-operation-flexibility nitrogen oxide pressurized absorption device and method, wherein the absorption device takes the first layer tray of an absorption tower as an inlet absorption water quantity regulator, a self-control regulating system is additionally arranged on a water inlet pipeline of an absorption water tank, a self-control regulating valve is arranged on an inlet of a liquid ring compressor from the tower kettle, a dilute nitric acid tank and the liquid ring compressor set are integrated into a large circulation system, a process mode of increasing pipeline flow by the large circulation is adopted, and the device defects of regulating valve internal leakage are solved, so that the problems of difficult operation under different nitrogen oxide absorption loads and easy operation failure leading to non-standard emission are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of nitrogen oxide absorption technology, specifically to a highly operationally flexible nitrogen oxide pressurized absorption device and method. Background Technology

[0002] Nitrogen oxides (NOx) gases are commonly treated using a 0.65 MPa pressurized absorption technology. This technology employs a single bubble cap tower and a liquid ring compressor unit at 0.65 MPa pressure; water is used as the absorbent to absorb NOxes, yielding a high concentration of 45%-50% nitric acid. The NOx content in the exhaust gas can be below 240 mg / m³. 3 .

[0003] To reduce equipment investment, some factories need to use the same set of nitrogen oxide absorption devices to alternately handle component concentrations up to 350,000 mg / m³. 3 The above high-concentration nitrogen oxide waste gas absorption and concentration below 65000 mg / m³ 3 The goal is to absorb low-concentration nitrogen oxide waste gas and obtain a relatively high concentration of dilute nitric acid with a concentration of 45-50%.

[0004] Problems exist:

[0005] (1) Meets the requirement of 350,000 mg / m³ 3 The above-mentioned high-concentration nitrogen oxide absorption devices, when conventionally designed, require large-sized pumps and control valves, while those with concentrations below 65000 mg / m³... 3 The absorption of low-concentration nitrogen oxide waste gas requires pumps and control valves of relatively small size; conventionally designed absorption devices cannot meet the usage requirements at the same time.

[0006] (2) It is easy to cause misoperation, resulting in environmental accidents caused by nitrogen oxide absorption tail gas failing to meet emission standards.

[0007] The existing technology involves either designing and manufacturing a 0.65MPa pressurized absorption unit for treating high-concentration nitrogen oxides (NOx), or designing and manufacturing another 0.65MPa pressurized absorption unit for the same purpose. Our company currently has one 0.65MPa NOx absorption unit, including a NOx absorption tower, a liquid ring compressor, an absorption tank and pump, and several automatic control valves. This unit is designed for NOx concentrations of 350,000 mg / m³. 3 The design uses water as the absorbent to obtain dilute nitric acid with a concentration of 40-55%, and the exhaust gas concentration is ≤240mg / m³. 3 .

[0008] The applicant attempted to use this device to alternately absorb nitrogen oxides at a concentration of 65,000 mg / m³ from other products, similarly obtaining dilute nitric acid with a concentration of 40–55%, and a tail gas emission concentration ≤240 mg / m³.3 The problems are as follows:

[0009] (1) When the concentration of nitrogen oxide components is low, the amount of water required for the absorption reaction is about 10-20% of the design amount, and the liquid flow rate is low;

[0010] (2) Under automatic control conditions, the regulating valves used are usually large in size. When the flow rate is low, the solution is prone to internal leakage, which makes it difficult to control the liquid level of the absorption tower, absorption water tank and liquid ring compressor unit, and easily leads to liquid shortage failure of the operating equipment.

[0011] (3) Employee misoperation can lead to excessively high concentration of dilute nitric acid in the compressor unit, resulting in substandard exhaust gas from the absorption tower, and in severe cases, yellow smoke, which seriously pollutes the environment.

[0012] Therefore, it is necessary to propose a high-operational-flexibility nitrogen oxide pressurized absorption device to solve the problem of difficulty in operation under different nitrogen oxide absorption loads and the easy occurrence of operational errors leading to non-compliance with emission standards. Summary of the Invention

[0013] This invention proposes a high-operability-flexibility nitrogen oxide pressurized absorption device to solve the problem of difficult operation and easy operation errors leading to non-compliance with emission standards when the automatic control valve is large under different nitrogen oxide absorption loads.

[0014] A high-operability-flexible nitrogen oxide pressurized absorption device, characterized in that it comprises a dilute nitric acid tank, a liquid ring compressor, a gas-liquid separator, an absorption tower, and a water supply unit connected in sequence; wherein:

[0015] The liquid ring compressor has a nitrogen oxide pipe 1 at its input end, and a dilute nitric acid tank has a dilute nitric acid pipe 4 connected to the nitrogen oxide pipe 1. The dilute nitric acid pipe 4 is equipped with a valve 1.

[0016] The gas phase output end of the gas-liquid separator is connected to the inlet of the absorption tower via nitrogen oxide pipe 2, and the liquid phase output end is connected to dilute nitric acid pipe 1; the dilute nitric acid tank is connected to dilute nitric acid pipe 5 via dilute nitric acid pipe 1.

[0017] The top of the absorption tower is equipped with a tail gas pipe, and the bottom of the tower is equipped with a dilute nitric acid pipe connected to a nitrogen oxide pipe.

[0018] The water supply unit is used to supply water to the absorption tower and ensure the liquid level threshold of at least one tray.

[0019] The first dilute nitric acid tube is equipped with a hydrometer; the second dilute nitric acid tube is equipped with a second valve, which is interlocked with the hydrometer.

[0020] Furthermore, the absorption tower is equipped with a level gauge; the input end of the valve is also equipped with a valve that is interlocked with the level gauge.

[0021] Furthermore, the gas-liquid separator is equipped with a level gauge 2, and the dilute nitric acid tube 1 is equipped with a valve 4 interlocked with the level gauge 2.

[0022] Furthermore, the dilute nitric acid tank is equipped with a level gauge three; the dilute nitric acid pipe one is equipped with a valve six, the dilute nitric acid pipe five is connected to the front end of the valve six, and the valve six is ​​interlocked with the level gauge three.

[0023] Furthermore, the absorber is also equipped with an air inlet pipe.

[0024] Furthermore, the water supply unit includes a water tank; the hand trough is provided with an outlet pipe connected to one side of the absorption tower, and the absorption tower is provided with a water circulation pipe connected to the water collection hand trough on the opposite side; at the connection with the absorption tower, the water circulation pipe spans at least one tray in the direction of the tower bottom relative to the outlet pipe.

[0025] Preferably, the water circulation pipe is equipped with valve seven, the absorption tower is equipped with level gauge one, and valve seven is interlocked with level gauge one.

[0026] Furthermore, a flow meter is installed on the dilute nitric acid tube four.

[0027] The present invention also proposes a method for absorbing nitrogen oxides using the absorption device described above, comprising the following steps:

[0028] Nitrogen oxide exhaust gas within the concentration threshold is mixed with air and enters nitrogen oxide pipe one. The liquid ring compressor uses dilute nitric acid as the working fluid for compression, and the compression product enters the gas-liquid separator to separate the liquid phase and gas phase.

[0029] The separated gas phase enters the absorption tower for absorption and is discharged from the tail gas pipe. The dilute nitric acid produced by absorption enters the nitrogen oxide pipe one through the dilute nitric acid pipe two.

[0030] The separated liquid phase enters dilute nitric acid tube one; valve two adjusts the flow rate according to the density threshold set by the densitometer.

[0031] When the concentration of nitrogen oxide exhaust gas exceeds the threshold, increase the water supply flow rate of the water supply unit to the absorption tower, and adjust valve two to increase the flow rate of dilute nitric acid pipe two.

[0032] When the concentration of nitrogen oxide exhaust gas is below the threshold, reduce the water supply flow from the water supply unit to the absorption tower, and activate the dilute nitric acid tank to replenish dilute nitric acid to the nitrogen oxide pipeline.

[0033] In the above absorption method, the density threshold of the densitometer corresponds to a dilute nitric acid concentration of 40–55 wt%; the concentration of the exhaust gas discharged from the tailpipe is less than 100 mg / m³. 3 The concentration of exhaust gas emitted from the exhaust pipe is less than 100 mg / m³. 3 .

[0034] Compared with the prior art, the beneficial effects of the present invention include, but are not limited to:

[0035] 1. The nitrogen oxide absorption device proposed in this invention effectively solves the problem of difficult operation caused by the large size of the automatic control valve during periods of unstable nitrogen oxide component concentration by setting up a density meter interlock to control the flow rate of dilute nitric acid working solution and by automatically compensating with dilute nitric acid. This does not affect the nitrogen oxide absorption operation and eliminates misoperation.

[0036] 2. The nitrogen oxide absorption method proposed in this invention avoids the defect of excessively high concentrations causing desorption equilibrium in the liquid ring compressor, which affects the intake gas, by setting the output dilute nitric acid concentration range to 40-55 wt%, thus preventing yellow smoke from the top of the tower. Furthermore, this absorption method can stabilize the exhaust gas emission concentration below 100 mg / m³. 3 . Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the high-operability-elasticity nitrogen oxide pressurized absorption device of the present invention.

[0038] 1. Liquid ring compressor; 2. Gas-liquid separator; 3. Absorption tower; 4. Dilute nitric acid tank; 5. Dilute nitric acid transfer pump; 6. Water tank; 7. Booster pump; 11. Oxide nitrogen pipe 1; 21. Oxide nitrogen pipe 2; 22. Dilute nitric acid pipe 1; 31. Water circulation pipe; 32. Tail gas pipe; 33. Dilute nitric acid pipe 2; 34. Air inlet pipe; 41. Dilute nitric acid pipe 3; 42. Dilute nitric acid pipe 4; 43. Dilute nitric acid pipe 5; 61. Water inlet pipe; 62. Water outlet pipe; D1. Valve 1; D2, Valve 2; D3, Valve 3; D4, Valve 4; D5, Valve 5; D6, Valve 6; D7, Valve 7; D8, Valve 8; D9, Valve 9; D10, Valve 10; D11, Valve 11; D12, Valve 12; M1, Density meter; L1, Level gauge 1; L2, Level gauge 2; L3, Level gauge 3; L4, Level gauge 4; F1, Flow meter 1; F2, Flow meter 2; P1, Pressure transmitter; and other related connecting pipelines and valves. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] It should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. The terms "one," "two," "three," etc., are only for the convenience of distinguishing similar or identical elements, and do not imply a specific order or numbering. The above terms should not be construed as limiting the present invention.

[0041] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "connected," "linked," "connected," and "set up" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Those skilled in the art will understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] Based on the principle of water absorbing nitrogen oxides, those skilled in the art recognize the following facts based on current technology:

[0043] (1)2NO+O2=2NO2 3NO2+H2O=2HNO3+NO

[0044] Based on the reaction equations, under the same gas flow rate, the higher the concentration of nitrogen oxides, the greater the required water flow rate and the greater the flow rate of dilute nitric acid produced, and vice versa.

[0045] (2) Under automatic control conditions, the pressure before the valve is generally 0.65MPa and the pressure after the valve is generally normal pressure. Due to the large pressure difference before and after the valve, under the condition of internal leakage of the valve sealing surface, the internal leakage of larger valves is larger.

[0046] (3) When the concentration of nitrogen oxide components is low, the amount of water required for the absorption reaction is about 10-20% of the design amount, and the liquid flow rate is low;

[0047] (4) When the concentration of dilute nitric acid in the compressor unit is too high, the tail gas of the absorption tower will not meet the standards, and in severe cases, yellow smoke will be emitted, which will seriously pollute the environment.

[0048] like Figure 1 As shown, in one embodiment, a highly operationally flexible nitrogen oxide pressurized absorption device is proposed, comprising a dilute nitric acid tank 4, a dilute nitric acid transfer pump 5, a liquid ring compressor 1, a gas-liquid separator 2, an absorption tower 3, a water tank 6, and a pressurized pump 7; wherein:

[0049] The dilute nitric acid tank 4 is equipped with a level gauge 3L3. A dilute nitric acid pipe 341 is connected to the upper part of the tank, and a valve 12D12 is installed on the pipe 341 for replenishing the tank with low-concentration dilute nitric acid. A dilute nitric acid pipe 42 is located at the lower part of the tank, and a dilute nitric acid transfer pump 5 is installed on the pipe 42. A dilute nitric acid pipe 43 is also located at the upper part of the tank, and a valve 11D11 is installed on the pipe 43.

[0050] The output end of the dilute nitric acid pump 5 is equipped with a flow meter F1 and a valve D1 in sequence; the input end of the liquid ring compressor 1 is equipped with a nitrogen oxide tube 11, and the dilute nitric acid tube 42 is connected to the nitrogen oxide tube 11.

[0051] The output end of the liquid ring compressor 1 is connected to the gas-liquid separator 2. The gas phase output end of the gas-liquid separator 2 is connected to the inlet (feed) of the absorption tower 3 via a nitrogen oxide pipe 21. The liquid phase output end is connected to a dilute nitric acid pipe 22. Along the liquid flow direction, dilute nitric acid pipe 22 is sequentially equipped with a density meter M1, valve D4, and valve D6. The gas-liquid separator 2 is also equipped with a level gauge L2. Valve D4 is interlocked with level gauge L2 to control the liquid level. Dilute nitric acid pipe 43 connects valve D4 and valve D6. Valve D6 is used to control the entry of dilute nitric acid into the external dilute nitric acid tank area.

[0052] The top of the absorption tower 3 is equipped with a tail gas pipe 32, which is fitted with a pressure transmitter P1 and a valve D8, interlocked to control the pressure at the top of the tower. A water circulation pipe 31 connects to the upper part of the water tank 6 at the top of the absorption tower 3, and a valve D7 is installed on the water circulation pipe 31. A level gauge L1 is installed at the bottom of the absorption tower 3, and valve D7 is interlocked with level gauge L1. At the bottom of the absorption tower 3, a dilute nitric acid pipe 33 is connected to a nitrogen oxide pipe 11 on the left. From left to right, the dilute nitric acid pipe 33 has valves D2 and D3; valve D2 is interlocked with density meter M1, and valve D3 is interlocked with level gauge L1. In addition, an air inlet pipe 34 is located opposite the air (material) inlet of the absorption tower 3, and a valve D5 is installed on the air inlet pipe 34 for adding and controlling compressed air.

[0053] The water tank 6 has an inlet pipe 61 at the top and an outlet pipe 62 at the bottom, connecting to the upper part of the absorption tower 3. A booster pump 7 is installed on the outlet pipe 62, and a flow meter F2 is installed at the output end. The outlet pipe 62 spans at least one tray from top to bottom between the absorption tower 3 and the water circulation pipe 31, ensuring that at least one tray in the absorption tower 3 is filled with water. The water tank 6 is also equipped with a level gauge L4. Valves D9 and D10 are installed on the inlet pipe 61, interlocked with level gauge L4 to facilitate control of the liquid level in the water tank 6.

[0054] In the above embodiment, nitrogen oxide exhaust gas within the concentration threshold is mixed with air and enters nitrogen oxide pipe 11. Liquid ring compressor 1 uses dilute nitric acid as the working fluid for compression, and the compression product enters gas-liquid separator 2 to separate liquid and gas phases. The separated gas phase enters absorption tower 3 for absorption and is discharged from the tail gas pipe. The dilute nitric acid generated by absorption enters nitrogen oxide pipe 11 through dilute nitric acid pipe 33. The separated liquid phase enters dilute nitric acid pipe 22. Valve D2 adjusts the flow rate according to the density threshold set by densitometer M1. The final output dilute nitric acid concentration is controlled by controlling the density. When the nitrogen oxide exhaust gas concentration is too low, dilute nitric acid tank 4 and dilute nitric acid transfer pump 5 are activated to replenish dilute nitric acid to liquid ring compressor 1, and the flow rate of valve D2 is adjusted to decrease to stabilize the value of densitometer M1.

[0055] In the above embodiments, the absorption tower 3 is a bubble cap tower. Preferably, the outlet pipe 62 enters the first tray of the absorption tower 3 (from the top of the tower to the bottom of the tower) as the inlet for the absorption water; the water circulation pipe 31 connects to the bottom of the first tray. A liquid level self-control regulation system is set through the water inlet pipeline of the water tank 6, and a density meter interlock regulating valve 2D2 and a liquid level interlock regulating valve 3D3 are set at the inlet of the liquid ring compressor 1. The dilute nitric acid tank 4 and the liquid ring compressor 1 are integrated into a large circulation system, which can increase the flow rate of the compressor system's self-control regulating valve and solve the defect of internal leakage caused by the large size of the self-control valve being unsuitable for small flow regulation.

[0056] In the above embodiments, the density meter M1 is set according to the density range corresponding to the final output dilute nitric acid concentration of the absorption device. For example, when the designed output dilute nitric acid concentration is 40-55 wt%, its density setting range is 1.25-1.34 g / cm³. 3 .

[0057] In the above embodiment, the dilute nitric acid in the dilute nitric acid tank 4, dilute nitric acid transfer pump 5, liquid ring compressor 1, and liquid ring separator 2 establishes a circulation, so that valve D4 can stably control the liquid level of gas-liquid separator 2 to about 50%, ensuring that density meter M1 continuously monitors the real-time density of dilute nitric acid in the liquid ring compressor 1 system, avoiding excessive density that would cause the liquid ring compressor to lose its suction capacity and cause the nitrogen oxide absorption tower to emit yellow smoke, resulting in an environmental accident.

[0058] In the above embodiment, when the level gauge L4 reaches the specified high level value, valve D10 automatically closes; when the level gauge L4 reaches the specified low level value, valve D10 automatically opens; valve D9 is set to a level height of 50%, and its opening is automatically adjusted according to the set level parameters; this ensures that the water tank 6 maintains a normal level, which satisfies the normal water supply of the absorption water booster pump 7, and also prevents overflow.

[0059] In the above embodiments, significant changes in the liquid level of the first tray (top layer) inside the absorption tower 3 do not affect the absorption operation.

[0060] In the above embodiments, a self-regulating valve can be used in the same pipeline to achieve the function of regulating large flow rates of liquid, and an on / off valve can be used to achieve the function of regulating small flow rates of liquid, thereby improving the accuracy of flow regulation.

[0061] In the above embodiment, according to the value set by the density meter M1, the opening of valve D2 is automatically adjusted. When the liquid level L1 in the bottom of the absorption tower 3 is lower than the specified low level value, valve 3 is automatically closed to ensure that there is a sufficient liquid level in the bottom of the absorption tower 3 and to avoid flooding of the nitrogen oxide absorption tower due to excessively low liquid level.

[0062] In another embodiment, a highly operationally flexible pressurized absorption method for nitrogen oxides is proposed. Taking the pressurization device described in the above embodiment as an example, the designed absorption concentration (nitrogen oxide concentration under optimal operating conditions) is 350,000 mg / m³. 3 For example, the operation is as follows:

[0063] a) Open valves D9 and D10 to add absorption water to water tank 6 and set the liquid level parameters;

[0064] b) Open valve 8D8 on the exhaust gas pipeline and appropriately open valve 5D5 on the air inlet pipe 34 to add a small amount of air into the absorption tower 3.

[0065] c) Start the booster pump 7 and adjust the flow rate of the booster pump 7 to the maximum according to the reading of the flow meter F2; the absorption water enters the absorption tower 3 and enters the tower bottom from top to bottom. Valve D7 is associated with level gauge L1. When level gauge L1 reaches the specified value, valve D7 automatically opens and the absorption water flows back to the water tank 6 through the water circulation pipe 31.

[0066] d) Open valves D2 and D3 to inject dilute nitric acid into the liquid ring compressor 1 and separator 2 to the specified value; set valve D8 on the tail gas pipe 32 to automatic and set the value of the associated pressure transmitter P1 to 0.55-0.58 MPa; the air pressure value at the input end of valve D5 is greater than 0.75 MPa to ensure that air can easily enter the tower; start the liquid ring compressor 1, and the nitrogen oxide exhaust gas and air are mixed and enter the nitrogen oxide pipe 11 and compressed by the liquid ring compressor 1 before entering the gas-liquid separator 2. The separated gas phase enters the absorption tower 3 with the nitrogen oxide pipe 21, and after being absorbed by water in the tower, it returns to the nitrogen oxide pipe 11 from the dilute nitric acid pipe 23; the liquid phase separated by the gas-liquid separator 2 enters the dilute nitric acid pipe 22.

[0067] f) Close valve 6D6 and open valve 11D11; set valve 4D4 to automatic, set the liquid level counter value of separator 2 to 50%, open all valves on dilute nitric acid pipe 42, start dilute nitric acid transfer pump 5, and adjust the opening of valve 1D1 according to the value of flow meter 1F1. Valve 4D4 automatically adjusts according to the value of liquid level gauge 2L2 (set to 50%), circulating the separated dilute nitric acid back to dilute nitric acid tank 4 for later use;

[0068] g) Valve D2 is associated with density meter M1; valve D3 is associated with level gauge L1. Valve D3 is closed when the liquid level is low. The density meter M1 setting range corresponds to the density of dilute nitric acid with a concentration of 40-55 wt%. When density meter M1 reaches the set range and level gauge L3 meets the standby liquid level, valve D6 is opened, valve D11 is closed, dilute nitric acid transfer pump 5 is stopped, and valve D1 is closed. The valves set for interlocking are in automatic mode. The dilute nitric acid separated by gas-liquid separator 2 is directly transported to the outside, while simultaneously ensuring that the exhaust gas emission concentration is ≤100 mg / m³. 3。

[0069] h) During production, monitor the changes in the density meter M1 value. Based on upstream production conditions, if the nitrogen oxide component concentration in nitrogen oxide tube-11 is consistently greater than 350,000 mg / m³, [further monitoring is needed]. 3 When the density meter M1 reading increases, valve D2 automatically increases the flow rate. Due to the increased output flow, the liquid level in absorber 3 changes, causing valve 7 to automatically decrease, increasing the amount of absorbent water entering. In interlocked automatic mode, the increased dilute nitric acid flow allows for the absorption of more nitrogen oxides, thus quickly balancing the density meter M1 to the set value, while simultaneously meeting the requirement of a tail gas emission concentration ≤100mg / m³. 3 ;

[0070] i) Based on upstream production conditions, if the concentration of nitrogen oxide components in nitrogen oxide pipe 11 drops to below 200,000 mg / m³ 3 At this time, the concentration of dilute nitric acid decreases after absorption, causing the density meter M1 value to drop. Operate and start the dilute nitric acid transfer pump 5, open valve D1, monitor the value of density meter M1, adjust valve D2 to automatic mode, adjust the value of flow meter F1 to control the dilute nitric acid compensation flow, so that the value of density meter M1 rises to the set range; set level gauge L3 to 50%, open valve D12 to replenish dilute nitric acid from the outside. When the value of density meter M1 stabilizes, open valve D6 to deliver dilute nitric acid to an external tank area.

[0071] j) When the concentration of nitrogen oxide components decreases further, such as at 65000 mg / m³ 3When the temperature is around 100°C, the amount of water required for nitrogen oxide absorption is significantly reduced. At this time, adjust the absorption water regulating valves 9 (D9) and 2 (D2) to manual mode and adjust the opening to the minimum. Valves 3 (D3), 10 (D10), and 7 (D7) are opened intermittently, and the output concentration range is maintained mainly by the dilute nitric acid compensated by the dilute nitric acid tank 4.

[0072] In the above absorption method, the value of pressure transmitter P1 is 0.55 to 0.58 MPa, which is to ensure that the pressure value of the tower bottom reaches about 0.62 to 0.65 MPa; in addition, it is necessary to ensure that the compressed air pressure value before valve D5 is higher than 0.75 MPa so that air can enter the nitrogen oxide absorption tower normally.

[0073] In the above absorption method, step b) opens the tail gas discharge valve D8 of the absorption tower and introduces an appropriate amount of air from valve D5 to create an upward airflow in the absorption tower tray, thereby eliminating the siphon effect caused by the downward flow of liquid during tray filling and ensuring normal tray filling.

[0074] In the above absorption method, step c) the pressurizing pump 7 adds water to the absorption tower 3, and the water overflows from the first tray to the bottom of the tower layer by layer, so that each tray is filled with working liquid; when the liquid level in the bottom of the tower reaches the specified value, the water in the first tray flows back to the water tank 6 through the return pipeline, and the absorption tower 3 is filled. It is no longer necessary to shut down or adjust the pressurizing pump 7.

[0075] In the above absorption method, the forced circulation process of external dilute nitric acid in step i) causes the concentration of dilute nitric acid at the outlet of liquid ring compressor 1 to increase, and the concentration of dilute nitric acid in dilute nitric acid tank 4 is preferably in the range of 40-55 wt%, ensuring that the value of density meter M1 recovers quickly.

[0076] The above nitrogen oxide absorption method operates stably, is highly automated, and is easy to operate, significantly reducing the workload. The absorption operation is unaffected during start-up and shutdown when the nitrogen oxide component concentration is unstable, eliminating the risk of misoperation. Even in the event of internal leakage, the large-scale regulating valve meets the automatic control requirements for low-concentration nitrogen oxide waste gas; it allows the absorption of low-concentration nitrogen oxide waste gas to obtain a higher concentration (40-55%) of dilute nitric acid, while simultaneously meeting the requirement that the tail gas emission concentration be ≤100 mg / m³. 3 The method employs a single nitrogen oxide absorption unit to alternately treat waste gases under extreme conditions of high and low nitrogen oxide concentrations. The start-up and shutdown processes, particularly during periods of unstable nitrogen oxide concentrations, do not affect the nitrogen oxide absorption operation, eliminating the environmental risks of misoperation and yellow smoke emission during periods of instability. It has been successfully applied to a 0.65MPa nitrogen oxide absorption bubble cap tower and is operating successfully, saving an average of over 1 million yuan annually.

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-operational-flexibility nitrogen oxide pressurized absorption device, characterized in that, It includes a dilute nitric acid tank (4), a liquid ring compressor (1), a gas-liquid separator (2), an absorption tower (3), and a water supply unit connected in sequence; wherein: The input end of the liquid ring compressor (1) is provided with a nitrogen oxide pipe (11), and the dilute nitric acid tank (4) is provided with a dilute nitric acid pipe (42) connected to the nitrogen oxide pipe (11). The dilute nitric acid pipe (42) is provided with a valve (D1). The gas phase output end of the gas-liquid separator (2) is connected to the gas inlet of the absorption tower (3) via a nitrogen oxide pipe 2 (21), and the liquid phase output end is connected to a dilute nitric acid pipe 1 (22); the dilute nitric acid tank (4) is connected to a dilute nitric acid pipe 5 (43) via a dilute nitric acid pipe 1 (22); The top of the absorption tower (3) is equipped with a tail gas pipe (32), and the bottom of the tower is equipped with a dilute nitric acid pipe (33) connected to a nitrogen oxide pipe (11); The water supply unit is used to supply water to the absorption tower (3) and ensure the liquid level threshold of at least one tray; The first dilute nitric acid tube (22) is equipped with a hydrometer (M1); the second dilute nitric acid tube (33) is equipped with a valve (D2), and the valve (D2) is interlocked with the hydrometer (M1); When the concentration of nitrogen oxide exhaust gas is greater than the threshold, increase the water supply flow of the water supply unit to the absorption tower (3) and adjust valve two (D2) to increase the flow of dilute nitric acid pipe two (33); When the concentration of nitrogen oxide exhaust gas is lower than the threshold, the water supply flow rate of the water supply unit to the absorption tower (3) is reduced, and the dilute nitric acid tank (4) is activated to replenish dilute nitric acid to nitrogen oxide pipe (11).

2. The absorption device according to claim 1, characterized in that, The absorption tower (3) is equipped with a level gauge (L1); the input end of the valve (D2) is also equipped with a valve (D3) that is interlocked with the level gauge (L1).

3. The absorption device according to claim 1, characterized in that, The gas-liquid separator (2) is equipped with a level gauge (L2), and the dilute nitric acid tube (22) is equipped with a valve (D4) that is interlocked with the level gauge (L2).

4. The absorption device according to claim 1, characterized in that, The dilute nitric acid tank (4) is equipped with a level gauge (L3); the dilute nitric acid pipe (22) is equipped with a valve (D6); the dilute nitric acid pipe (43) is connected to the front end of the valve (D6); the valve (D6) is interlocked with the level gauge (L3).

5. The absorption device according to claim 1, characterized in that, The absorber (3) is also equipped with an air inlet pipe (34).

6. The absorption device according to claim 1, characterized in that, The water supply unit includes a water tank (6); the water tank (6) is provided with an outlet pipe (62) connected to one side of the absorption tower (3), and the absorption tower (3) is provided with a water circulation pipe (31) connected to the water tank (6) on the other side; at the connection with the absorption tower (3), the water circulation pipe (31) spans at least one tray in the direction of the tower bottom relative to the outlet pipe (62).

7. The absorption device according to claim 6, characterized in that, The water circulation pipe (31) is equipped with valve seven (D7), and the absorption tower (3) is equipped with level gauge one (L1). Valve seven (D7) and level gauge one (L1) are interlocked.

8. The absorption device according to claim 1, characterized in that, The dilute nitric acid tube four (42) is equipped with a flow meter one (F1).

9. A method for absorbing nitrogen oxides using the absorption device of claim 1, characterized in that the steps include... include: After the nitrogen oxide exhaust gas within the concentration threshold is mixed with air, it enters the nitrogen oxide tube (11). The liquid ring compressor (1) compresses the gas with dilute nitric acid as the working fluid. The compression product enters the gas-liquid separator (2) to separate the liquid phase and the gas phase. The separated gas phase enters the absorption tower (3) for absorption and is discharged from the tail gas pipe (32). The dilute nitric acid produced by absorption enters the nitrogen oxide pipe (11) through the dilute nitric acid pipe (2) (33). The separated liquid phase enters dilute nitric acid tube one (22); valve two (D2) adjusts the flow rate according to the density threshold set by the densitometer (M1); When the concentration of nitrogen oxide exhaust gas is greater than the threshold, increase the water supply flow of the water supply unit to the absorption tower (3) and adjust valve two (D2) to increase the flow of dilute nitric acid pipe two (33); When the concentration of nitrogen oxide exhaust gas is lower than the threshold, the water supply flow rate of the water supply unit to the absorption tower (3) is reduced, and the dilute nitric acid tank (4) is activated to replenish dilute nitric acid to nitrogen oxide pipe (11).

10. The method according to claim 9, characterized in that, The density threshold of the hydrometer (M1) corresponds to a dilute nitric acid concentration of 40~55wt%; the concentration of the exhaust gas discharged from the tailpipe (32) is less than 100mg / m³. 3 .

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