Efficient nitrogen oxide recycling device in adipic acid production

Abstract

The utility model discloses an efficient nitrogen oxide recycling device in adipic acid production. The efficient nitrogen oxide recycling device comprises a reaction kettle, oxygen enrichment equipment, a nitrogen oxide condenser, a compressor, an absorption tower, a chimney and an oxidized acid storage tank, oxygen-enriched air generated by the oxygen-enriched equipment and nitric oxide gas generated by the reaction kettle are mixed and then are connected to the nitric oxide condenser through a pipeline, so that the temperature of the gas is reduced, the specific volume is reduced, and part of nitric acid steam and condensable gas are condensed into nitric acid liquid to serve as compressor liquid ring liquid; one part of gas at the outlet of the compressor is circulated back to the inlet of the compressor to adjust the pressure of the reactor, the rest of gas enters the nitrogen oxide absorption tower, the absorption liquid comes from low-concentration nitric acid steam condensate in the previous process, and the nitrogen oxide gas and the absorption liquid reversely flow in the absorption tower; the high-concentration nitric acid is sent to an oxidizing acid storage tank for cyclic utilization, and a small amount of nitric oxide gas which is discharged from the top of the absorption tower and meets the national emission standard is discharged into the atmosphere through a chimney.

Description

Technical Field

[0001] The utility model relates to the technical field of adipic acid production, in particular to a device for efficiently recovering and utilizing nitrogen oxides in adipic acid production. Background Art

[0002] Among the adipic acid production processes, the most widely used and mature production process is the nitric acid oxidation of cyclohexanol. In order to ensure the complete reaction of cyclohexanol, 50%-70% nitric acid is used to react with it. Under high temperature environment, high concentration nitric acid is easy to volatilize, and the oxidation reaction generates a large amount of nitrogen oxide gas.

[0003] In the production of adipic acid, the existing nitrogen oxide gas recovery generally adopts the liquid absorption method, that is, the nitrogen oxide gas produced by the reaction is mixed with air, enters the compressor for pressurization, and then enters the absorption tower. In the absorption tower, the nitrogen oxide, oxygen, and water undergo a chemical reaction to generate nitric acid and then are recycled for reuse. The remaining nitrogen oxide gas is discharged into the atmosphere through the chimney. According to the absorption principle, it can be known that the nitrogen oxide conversion rate is closely related to the oxygen concentration in the tower, the gas flow rate, the residence time, the temperature, etc. In actual production, the oxygen required for the nitrogen oxide reaction comes from the atmosphere. The oxygen content in the atmosphere is low. Due to the limitation of the compressor capacity, when the nitrogen oxide concentration is high, it cannot provide enough air, which easily causes insufficient oxygen content in the tower and a fast flow rate, resulting in a low nitrogen oxide conversion rate and a high nitrogen oxide emission concentration, which increases production costs and is not conducive to the long-term development of the enterprise. Therefore, it is necessary to further improve the existing nitrogen oxide gas recovery technology. Utility Model Content

[0004] The utility model aims to provide a highly efficient recovery and utilization device for nitrogen oxides in adipic acid production, so that the nitrogen oxides absorption tower can achieve highly efficient conversion of nitrogen oxides through oxygen enrichment technology, reduce environmental pollution and lower production costs.

[0005] Based on the above purpose, the technical solution adopted by the utility model is as follows:

[0006] A highly efficient recovery and utilization device for nitrogen oxides in adipic acid production comprises a reactor, an oxygen-enriching device, a nitrogen oxide condenser, a compressor, an absorption tower, an oxidizing acid storage tank and a chimney, wherein the oxygen-enriching device is provided with an oxygen-enriched gas outlet and a nitrogen-enriched gas outlet, wherein the oxygen-enriched gas outlet is connected to an inlet of a nitrogen oxide condenser through a pipeline, wherein the nitrogen-enriched gas outlet is connected to a compressed air network through a pipeline, wherein the outlet of the reactor is connected to an oxygen-enriched gas outlet pipeline through a pipeline so that the nitrogen oxide gas generated by the reactor is mixed with the oxygen-enriched gas and then enters the nitrogen oxide condenser, wherein the outlet of the nitrogen oxide condenser is connected to an oxygen-enriched gas outlet pipeline through a pipeline The pipeline is connected to the compressor inlet, and the compressor outlet is provided with two pipelines, one pipeline is connected to the compressor inlet, and the other pipeline is connected to the absorption tower to keep the reactor pressure at negative pressure. The gas phase outlet at the top of the absorption tower is connected to the chimney through a pipeline, and the liquid phase outlet at the bottom of the absorption tower is provided with two pipelines, one pipeline is connected to the top of the absorption tower through a bottom pump, and the other pipeline is connected to the oxidizing acid storage tank, so that part of the liquid at the bottom of the absorption tower is sent to the top of the tower through the bottom pump to serve as absorption liquid, and part of it is sent to the oxidizing acid storage tank, and the outlet of the oxidizing acid storage tank is connected to the inlet of the reactor through a pipeline.

[0007] Furthermore, a first gas flow regulating valve is provided on the pipeline between the oxygen enrichment device and the nitrogen oxide condenser, and the first gas flow regulating valve is used to adjust the amount of oxygen-enriched gas entering the system.

[0008] Furthermore, a cooling water inlet and a cooling water return outlet are provided on the nitrogen oxide condenser. The cooling water of the nitrogen oxide condenser adopts a low-in and high-out method, thereby lowering the gas temperature and reducing the specific volume, and part of the nitric acid vapor and condensable gas are condensed into nitric acid liquid.

[0009] Furthermore, a second gas flow regulating valve is provided on the connecting pipe between the compressor outlet and the compressor inlet, which controls the pressure of the reactor to a negative pressure state by adjusting the circulating gas volume, thereby ensuring that the pressure of the reactor is stable and the reaction is controllable.

[0010] Furthermore, a delivery pump is provided on the pipeline between the absorption tower and the oxidizing acid storage tank, and on the pipeline between the oxidizing acid storage tank and the reactor.

[0011] Furthermore, the enrichment equipment is an oxygen-enriched membrane oxygen generator.

[0012] The oxygen enrichment equipment converts air containing 21% oxygen and 78% nitrogen into 40% oxygen-enriched air. The oxygen partial pressure in the absorption tower is increased, which greatly reduces the nitrogen partial pressure. The 40% oxygen-enriched gas is mixed with the nitrogen oxide gas produced by the reactor through a pipeline and enters the nitrogen oxide condenser. The nitrogen-enriched gas enters the compressed air network through a pipeline to supplement the gas volume of the compressed air network.

[0013] Furthermore, the absorption liquid in the absorption tower comes from the low-concentration nitric acid vapor condensate from the previous process; a chemical reaction takes place in the absorption tower: 2NO+O2→2NO2, 2NO2←→N2O4, N2O4+H2O→HNO3+HNO2, HNO2→NO+NO2+H2O, and the absorption liquid circulates in the tower to absorb the nitric acid vapor produced by the reaction.

[0014] Furthermore, a liquid level regulating valve is provided on the pipeline between the absorption tower and the oxidizing acid storage tank. A portion of the liquid at the bottom of the absorption tower is pumped to the top of the tower as absorption liquid through the bottom pump, and a portion is sent to the oxidizing acid storage tank through the liquid level regulating valve.

[0015] Furthermore, the qualified low-concentration nitrogen oxide gas at the top of the absorption tower is sent to the chimney through a pipeline for discharge.

[0016] Furthermore, a concentration detector and a third gas flow regulating valve are provided on the pipeline between the top of the absorption tower and the chimney. The concentration detector is used to detect the nitrogen oxide concentration and oxygen content of the exhaust gas, and the third gas flow regulating valve is used to control the outlet pressure of the absorption tower.

[0017] Advantages of the utility model:

[0018] 1. The utility model increases the oxygen content in the absorption tower by adding oxygen enrichment equipment, and the conversion efficiency of nitrogen oxide gas to nitric acid gas is increased by about 85%. The oxygen concentration in the tail gas of the absorption tower reaches more than 8vol%, and the nitrogen oxide concentration is reduced to 90mg / m 3 Below, fully meet the national emission standards (<150mg / m 3 ).

[0019] 2. In the utility model, the load of the adipic acid production device is stable, the amount of nitrogen oxide gas generated in the reactor is stable, and the original system supplements the air oxygen concentration of 21%. After the oxygen concentration is increased to 40% by the oxygen enrichment equipment, the total amount of air entering the system is reduced by about 40%-50% while the oxygen amount in the system remains unchanged, the compressor load is reduced, the gas flow rate in the absorption tower is reduced from 35m / s to about 15m / s, the gas retention time is extended, and the nitrogen oxide recovery rate is increased by about 85%.

[0020] 3. In the utility model, the concentration of nitric acid solution recovered at the bottom of the absorption tower is increased from 30% to about 55%, and nitrogen oxides are fully converted and recycled, which greatly reduces the unit consumption of nitric acid in the adipic acid device, saves costs, and improves product competitiveness.

[0021] 4. When oxygen-enriched equipment produces oxygen-enriched air, it is accompanied by the production of nitrogen-enriched gas. This part of nitrogen-enriched gas is added to the compressed air network, which reduces the load of the air compressor, reduces the consumption of electricity, and saves production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the utility model;

[0023] In the figure, 1. oxygen enrichment equipment, 2. reactor, 3. nitrogen oxide condenser, 4. compressor, 5. absorption tower, 6. oxidizing acid storage tank, 7. chimney, 8. first gas flow regulating valve, 9. second gas flow regulating valve, 10. concentration detector, 11. third gas flow regulating valve, 12. absorption tower liquid level regulating valve. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0025] The oxygen enrichment equipment in the utility model is purchased directly according to the market demand. The application specifically adopts an oxygen-enriched membrane oxygen generator, a highly efficient recovery and utilization device of adipic acid nitrogen oxides in adipic acid production, such as Figure 1 As shown, it includes a reactor 2, an oxygen-enriching device 1, a nitrogen oxide condenser 3, a compressor 4, an absorption tower 5, an oxidizing acid storage tank 6 and a chimney 7. The oxygen-enriching device 1 is provided with an oxygen-enriched gas outlet and a nitrogen-enriched gas outlet. The oxygen-enriched gas outlet is connected to the inlet of the nitrogen oxide condenser 3 through a pipeline, and the nitrogen-enriched gas outlet is connected to the compressed air network through a pipeline. The outlet of the reactor 2 is connected to the oxygen-enriched gas outlet pipeline through a pipeline so that the nitrogen oxide gas generated by the reactor 2 is mixed with the oxygen-enriched gas and then enters the nitrogen oxide condenser 3. The outlet of the nitrogen oxide condenser 3 is connected to the inlet of the compressor 4 through a pipeline. The compressor 4 outlet is provided with two pipelines, one pipeline is connected to the compressor 4 inlet, and the other pipeline is connected to the absorption tower 5 so as to keep the pressure of the reactor 2 at a negative pressure. The gas phase outlet at the top of the absorption tower 5 is connected to the chimney 7 through a pipeline. The absorption tower 5 bottom liquid phase outlet is provided with two pipelines, one pipeline is connected to the top of the absorption tower 5 through a bottom pump (not shown in the figure), and the other pipeline is connected to the oxidizing acid storage tank 6, so that part of the liquid at the bottom of the absorption tower is sent to the top of the tower through the bottom pump to serve as absorption liquid, and part of it is sent to the oxidizing acid storage tank 6. The outlet of the oxidizing acid storage tank 6 is connected to the reactor 2 through a pipeline.

[0026] Among them, a first gas flow regulating valve 8 is provided on the pipeline between the oxygen enrichment device 1 and the nitrogen oxide condenser 3. A second gas flow regulating valve 9 is provided on the connecting pipeline between the compressor 4 outlet and the compressor 4 inlet. A concentration detector 10 and a third gas flow regulating valve 11 are provided on the pipeline between the absorption tower 5 and the chimney 7. An absorption tower liquid level regulating valve 12 is provided on the pipeline between the absorption tower 5 and the oxidizing acid storage tank 6.

[0027] Among them, a delivery pump is provided on the pipeline between the absorption tower 5 and the oxidizing acid storage tank 6, and on the pipeline between the oxidizing acid storage tank 6 and the reactor 2. A cooling water inlet and a cooling water return outlet are provided on the nitrogen oxide condenser 3, and the cooling water of the nitrogen oxide condenser 3 adopts a low-in and high-out method.

[0028] The operation process of the utility model is as follows:

[0029] Excessive nitric acid with a concentration of 50%-70% and cyclohexanol react in the reactor 2. The nitrogen oxide gas generated in the reactor 2 is mixed with the oxygen-enriched air with a concentration of 40% generated by the oxygen-enriching device 1 and enters the nitrogen oxide condenser 3 through a pipeline. The oxygen-enriched air generated by the oxygen-enriching device 1 controls the amount of gas entering the system through the first gas flow regulating valve 8, and the nitrogen-enriched gas generated by the oxygen-enriching device 1 is sent to the compressed air network through a pipeline. After the mixed gas passes through the nitrogen oxide condenser 3, the gas temperature decreases and the specific volume decreases, so that part of the nitric acid vapor and condensable gas condenses into nitric acid liquid. This part of the condensate enters the compressor 4 as a liquid ring liquid, and the remaining nitrogen oxide mixed gas enters the inlet of the compressor 4 and is pressurized to about 0.2MPa by the compressor 4. After that, a part of the nitrogen oxide gas returns to the inlet of the compressor 4 through the second gas flow regulating valve 9 to adjust the pressure in the reactor 2 to about -100~-250mm water column, ensuring that the pressure in the reactor 2 is stable and controllable. Most of the nitrogen oxide gas enters the absorption tower 5, and the following chemical reactions occur under a certain pressure (about 0.2MPa), sufficient oxygen content and oxygen concentration, and a suitable gas flow rate (about 15m / s) in the absorption tower 5: 2NO+O2→2NO2, 2NO2←→N2O4, N2O4+H2O→HNO3+HNO2, HNO2→NO+NO2+H2O, generating a large amount of nitric acid vapor. The low-concentration nitric acid condensate from the previous process is pumped to the top of the absorption tower 5 through the bottom of the tower, and contacts with the nitric acid gas from top to bottom in the absorption tower 5 in reverse, and is fully absorbed. Finally, most of the nitrogen oxide gas is absorbed by the reaction in the absorption tower 5. The remaining small amount of nitrogen oxide gas at the top of the tower is transported to the chimney 7 through a pipeline for discharge. The gas outlet from the top of the absorption tower 5 is regulated by the third gas flow regulating valve 11 to control the gas outlet pressure of the absorption tower 5 to be around 0.19 MPa, which is conducive to the reaction of nitrogen oxide gas in the absorption tower 5. The concentration detector 10 detects that the oxygen content in the gas from the top of the absorption tower 5 is above 8 vol%, and the nitrogen oxide concentration is 90 mg / m 3 About 150mg / m 3 ). After sampling and analysis of the solution at the bottom of the absorption tower 5, the nitric acid content reached about 55%, which fully met the reaction requirements. The high-concentration nitric acid solution at the bottom of the absorption tower 5 was sent to the oxidizing acid storage tank 6 by the bottom pump under the control of the absorption tower liquid level regulating valve 12, and the oxidizing acid storage tank 6 was sent to the reactor 2 for recycling by the delivery pump.

[0030] It should be noted that the terms "first", "second", etc. in the specification and claims of this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so as to describe the embodiments of the present application described herein.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions for the specific implementation of the present invention rather than to limit it. Ordinary technicians in the relevant technical field should understand that any equivalent substitution or obvious modification of the implementation mode of the present invention without changing its performance or use, without violating the purpose of the present invention, should be included in the scope of protection requested by the present invention.

Claims

1. A highly efficient recovery and utilization device for nitrogen oxides in adipic acid production, characterized in that: The invention comprises a reactor, an oxygen-enriching device, a nitrogen oxide condenser, a compressor, an absorption tower, an oxidizing acid storage tank and a chimney. The oxygen-enriching device is provided with an oxygen-enriched gas outlet and a nitrogen-enriched gas outlet. The oxygen-enriched gas outlet is connected to the inlet of the nitrogen oxide condenser through a pipeline. The nitrogen-enriched gas outlet is connected to the compressed air network through a pipeline. The outlet of the reactor is connected to the oxygen-enriched gas outlet pipeline through a pipeline so that the nitrogen oxide gas generated by the reactor is mixed with the oxygen-enriched gas and enters the nitrogen oxide condenser. The outlet of the nitrogen oxide condenser is connected to the inlet of the compressor through a pipeline. The outlet of the compressor is provided with two pipelines, one of which is connected to the inlet of the compressor, and the other is connected to the absorption tower so as to keep the pressure of the reactor at a negative pressure. The gas phase outlet at the top of the absorption tower is connected to the chimney through a pipeline. The liquid phase outlet at the bottom of the absorption tower is provided with two pipelines, one of which is connected to the top of the absorption tower through a bottom pump, and the other is connected to the oxidizing acid storage tank, so that part of the liquid at the bottom of the absorption tower is sent to the top of the tower as absorption liquid through the bottom pump, and part is sent to the oxidizing acid storage tank. The outlet of the oxidizing acid storage tank is connected to the inlet of the reactor through a pipeline.

2. The device for efficiently recovering and utilizing nitrogen oxides in adipic acid production according to claim 1, characterized in that: A first gas flow regulating valve is provided on the pipeline between the oxygen enrichment device and the nitrogen oxide condenser.

3. The device for efficiently recovering and utilizing nitrogen oxides in adipic acid production according to claim 1, characterized in that: A cooling water inlet and a cooling water return outlet are provided on the nitrogen oxide condenser, and the cooling water of the nitrogen oxide condenser adopts a low-inlet and high-outlet mode.

4. The device for efficiently recovering and utilizing nitrogen oxides in adipic acid production according to claim 1, characterized in that: A second gas flow regulating valve is provided on the connecting pipeline between the compressor outlet and the compressor inlet.

5. The device for efficiently recovering and utilizing nitrogen oxides in adipic acid production according to claim 1, characterized in that: Delivery pumps are provided on the pipeline between the absorption tower and the oxidizing acid storage tank, and on the pipeline between the oxidizing acid storage tank and the reactor.

6. The device for efficiently recovering and utilizing nitrogen oxides in adipic acid production according to claim 1, characterized in that: A concentration detector and a third gas flow regulating valve are provided on the pipeline between the absorption tower and the chimney.

7. The device for efficiently recovering and utilizing nitrogen oxides in adipic acid production according to claim 1, characterized in that: An absorption tower liquid level regulating valve is provided on the pipeline between the absorption tower and the oxidizing acid storage tank.

8. The device for efficiently recovering and utilizing nitrogen oxides in adipic acid production according to claim 1, characterized in that: The oxygen-enriched equipment is an oxygen-enriched membrane oxygen generator.

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