Adipic acid tail gas nitrogen oxide treatment process for recycling purified tail gas and waste heat

Abstract

The application relates to an adipic acid tail gas nitrogen oxide treatment process for recycling purified tail gas and waste heat, and belongs to the field of adipic acid tail gas treatment. Specifically, the process comprises the following steps: a gas-liquid separation tank is used for separating high-concentration nitrogen oxide tail gas and waste liquid; a fresh air compressor and a circulating air compressor are responsible for providing air for initial start of the tail gas treatment device and providing purified tail gas as circulating gas for smooth operation; a nitrous oxide decomposition reactor is provided with a reaction cavity for catalytic decomposition reaction, so as to remove nitrous oxide in the tail gas; a denitration reactor is used for removing nitric oxide and nitrogen dioxide in the tail gas; a plurality of preheaters are internally provided with heat exchange channels and are responsible for heat exchange between gases, so as to recycle waste heat; and the process further comprises a plurality of exhaust pipes and an electric heater. In the application, the purified tail gas is recycled as circulating gas, the introduction of low-temperature fresh air is reduced, heat energy and gas are recycled, the demand for fresh air is reduced, energy consumption is reduced, and the application is more friendly to the environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of adipic acid tail gas treatment, in particular to a process for effectively recovering and purifying tail gas and its waste heat and simultaneously removing nitrogen oxides (including nitrous oxide, nitric oxide and nitrogen dioxide) in adipic acid production tail gas. BACKGROUND

[0002] Adipic acid is an important organic dibasic acid, which plays an important role in chemical production, organic synthesis industry, medicine, lubricant manufacturing, etc. Its production ranks second among all dibasic carboxylic acids. Adipic acid production produces by-products of nitrogen oxides (nitrous oxide, nitric oxide and nitrogen dioxide). Nitrous oxide has a greenhouse effect about 300 times that of carbon dioxide, is an important greenhouse gas, and is an important indicator that needs to be controlled to achieve the goal of "carbon neutrality" and "carbon peak". Nitric oxide / nitrogen dioxide is a recognized air pollutant and one of the indicators for air quality evaluation, and is a major factor leading to environmental pollution such as acid rain, ozone hole, and photochemical smog.

[0003] The temperature required for efficient catalytic decomposition of nitrous oxide in the tail gas is relatively high (at least 450℃ or higher). In order to reduce energy consumption, existing adipic acid tail gas treatment processes pay great attention to the recovery of gas waste heat. However, even if multiple heat exchangers are installed in existing patents to recover waste heat multiple times to reduce energy consumption as much as possible, high-temperature tail gas (greater than 100℃) is still discharged into the atmosphere after the removal of nitrogen oxides. This not only wastes heat but also requires the introduction of compressed air for heating, greatly increasing energy consumption. SUMMARY

[0004] In view of this, we designed a process that can simultaneously remove nitrous oxide, nitric oxide and nitrogen dioxide, and recovered the high-temperature tail gas after purification through a unique design, to solve the problems of nitrogen oxide emission, waste heat waste and high energy consumption in adipic acid tail gas.

[0005] To achieve the above-mentioned goal of the adipic acid tail gas nitrogen oxide catalytic decomposition process technology scheme capable of recovering high-temperature tail gas is as follows:

[0006] The device comprises a gas-liquid separation tank, which functions to separate high-concentration nitrogen oxide tail gas and waste liquid. The gas-liquid separation tank is connected to a waste liquid delivery pump to discharge waste water. The first exhaust pipe is connected to an air compressor.

[0007] A fresh air compressor and a circulating air compressor are connected in parallel to the first exhaust pipe. The fresh air compressor is responsible for providing air for the initial start-up of the tail gas treatment device. After the tail gas treatment device is running smoothly, the circulating air compressor supplies the purified tail gas as a gas source to the device.

[0008] The first preheater, located after the gas-liquid separator and the air compressor, is responsible for heat exchange between the exhaust gas to be purified in the first exhaust pipe and the recirculated air in the ninth exhaust pipe. After heat exchange, the exhaust gas to be purified enters the next unit, while the cooled purified exhaust gas enters the recirculated air compressor through the ninth exhaust pipe.

[0009] The second preheater is responsible for heat exchange between the gases in the second and fifth exhaust pipes, heating the exhaust gas to be purified in the second exhaust pipe a second time, and cooling the exhaust gas in the fifth exhaust pipe after nitrous oxide has been removed.

[0010] An electric heater, placed before the nitrous oxide decomposer, is responsible for heating the exhaust gas to be purified in the third exhaust pipe for the third time.

[0011] The nitrous oxide decomposition reactor has its inlet connected to the fourth exhaust pipe and its outlet connected to the fifth exhaust pipe, and is responsible for removing nitrous oxide from the exhaust gas.

[0012] The denitrification reactor, with its inlet connected to the sixth exhaust pipe and its outlet connected to the seventh exhaust pipe, is responsible for removing nitric oxide and nitrogen dioxide from the exhaust gas. The purified exhaust gas will be used as the circulating gas for the entire process.

[0013] The third preheater is responsible for cooling the purified exhaust gas in the seventh exhaust pipe for use as circulating gas. It can heat the steam introduced into the adipic acid production unit, thereby reducing the energy consumption of the adipic acid production-exhaust gas treatment process.

[0014] Specifically, the second exhaust pipe has a diversion pipe and is equipped with a valve before the second preheater to control the amount of gas entering the second preheater. The gas that is finally diverted is mixed after the electric heater to facilitate the control of the gas temperature entering the nitrous oxide decomposition reactor.

[0015] Specifically, a gas flow inlet branch with a valve is provided at the position of the sixth exhaust pipe before the inlet of the denitrification reactor, so as to facilitate flexible adjustment of the gas volume and gas temperature entering the denitrification reactor according to the actual production situation.

[0016] Specifically, the tenth exhaust pipe has a branch leading to the external exhaust chimney and a valve to allow the purified exhaust gas to be released into the atmosphere.

[0017] The purification process for adipic acid production tail gas is as follows: After separation in a gas-liquid separator, the tail gas is mixed with fresh air / recirculated gas. The mixed gas then flows through the first preheater for initial heating. The heated tail gas is divided into two streams. One stream enters the second preheater for a second heat exchange, and after being heated by an electric heater, it mixes with the split gas to reach a suitable temperature before entering the nitrous oxide decomposer. After removing nitrous oxide in the nitrous oxide decomposer, the tail gas undergoes a third heat exchange in the second preheater. The cooled gas then flows into the denitrification reactor. In the denitrification reactor, nitric oxide and nitrogen dioxide are removed, resulting in purified tail gas. This purified tail gas then passes through the third preheater for a fourth heat recovery, and then through the first preheater for a fifth heat exchange. Afterward, it is used as recirculated air by a circulating air pump and mixed again with the gas-liquid separated tail gas. This cycle is repeated to complete the treatment of adipic acid production tail gas.

[0018] Specifically, the third preheater can heat the steam required for adipic acid production.

[0019] In summary, the outstanding effect of this invention is that by using recirculated gas as the dilution gas for the exhaust gas to be treated, the introduction of air is reduced. While further recovering heat energy, it also reduces the energy consumption caused by reheating the newly introduced fresh air, effectively solving the problems of waste heat and high energy consumption of equipment in the prior art. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the present invention.

[0021] The figure shows the process design provided by the present invention, which can recover and purify the tail gas and residual heat and simultaneously remove nitrogen oxides from the tail gas of adipic acid production. The pipelines and equipment involved are marked in the figure.

[0022] The equipment labeled in the diagram corresponds to the following: 11. Gas-liquid separator 12. Fresh air compressor 13. Circulating air compressor 14. First preheater 15. Second preheater 16. Electric heater 17. Nitrous oxide decomposition reactor 18. Denitrification reactor 19. Third preheater 20. Chimney 21. Waste liquid transfer pump.

[0023] 1, 2, 3...9, 10 correspond to the first, second, third...ninth and tenth exhaust pipes, respectively.

[0024] In particular, the second, sixth and tenth exhaust pipes should contain branches with valves.

[0025] Specifically, the fresh air branch should be equipped with a valve. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0027] The device includes: a gas-liquid separator 11, which functions to separate high-concentration nitrogen oxide tail gas and waste liquid; a gas-liquid separator drain tank connected to a waste liquid transfer pump for discharging wastewater; and a first exhaust pipe connected to a fresh air compressor and a circulating air compressor.

[0028] Fresh air compressor 12 and circulating air compressor 13 are connected in parallel to the first exhaust pipe. The fresh air compressor is responsible for providing air when the exhaust gas treatment device is started for the first time. After the exhaust gas treatment device is running smoothly, the circulating air compressor works alone to introduce the purified exhaust gas into the device as an air source.

[0029] The first preheater 14, located after the gas-liquid separator and the air compressor, is responsible for heat exchange between the exhaust gas to be purified in the first exhaust pipe and the purified recirculated gas in the ninth exhaust pipe. After heat exchange, the exhaust gas to be purified enters the next unit, and the cooled purified exhaust gas enters the recirculated air compressor through the ninth exhaust pipe.

[0030] The first preheater 14 is connected to the second preheater 15 through the second exhaust pipe; the second preheater is connected to the nitrous oxide decomposition reactor 17 through the fifth exhaust pipe; the second preheater is connected to the nitrous oxide decomposition reactor 18 through the sixth exhaust pipe; the nitrous oxide decomposition reactor 18 is connected to the third preheater 19 through the seventh exhaust pipe.

[0031] The second preheater 15 is responsible for heat exchange between the gases in the second and fifth exhaust pipes, heating the exhaust gas to be purified in the second exhaust pipe for the second time, and cooling the exhaust gas in the fifth exhaust pipe after nitrous oxide has been removed.

[0032] The electric heater 16, which is placed in front of the nitrous oxide decomposer, is responsible for heating the exhaust gas to be purified in the third exhaust pipe for the third time.

[0033] The nitrous oxide decomposition reactor 17 has its inlet connected to the fourth exhaust pipe and its outlet connected to the fifth exhaust pipe, and is responsible for removing nitrous oxide from the exhaust gas.

[0034] The denitrification reactor 18, with its inlet connected to the sixth exhaust pipe and its outlet connected to the seventh exhaust pipe, is responsible for removing nitric oxide and nitrogen dioxide from the exhaust gas. The purified exhaust gas will be used as the circulating gas for the entire process.

[0035] The third preheater 19 is responsible for cooling the purified exhaust gas in the seventh exhaust pipe for use as circulating gas. It can heat the steam introduced into the adipic acid production unit, thereby reducing the energy consumption of the adipic acid production-exhaust gas treatment process.

[0036] Specifically, the second exhaust pipe 2 has a diversion pipe and is equipped with a valve before the second preheater to control the amount of gas entering the second preheater. The gas that is finally diverted is mixed after the electric heater to facilitate the control of the gas temperature entering the nitrous oxide decomposition reactor.

[0037] The equipment included in this process is as follows: a gas-liquid separator, which is connected to a waste liquid transfer pump and a first exhaust pipe.

[0038] A fresh air compressor and a recirculating air compressor are connected in parallel to the first exhaust pipe.

[0039] The first preheater, located after the gas-liquid separator and air compressor, contains a heat exchange channel. The first preheater is responsible for exchanging heat between the exhaust gas to be purified in the first exhaust pipe and the purified recirculated gas in the ninth exhaust pipe.

[0040] The second preheater is located after the first preheater. It contains heat exchange channels. The second preheater is responsible for the heat exchange between the gases in the second and fifth exhaust pipes.

[0041] An electric heater, located after the second preheater and before the nitrous oxide decomposer, contains a resistor used for heating, and a third exhaust pipe surrounds its exterior.

[0042] The nitrous oxide decomposition reactor is located after the electric heater, with its inlet connected to the fourth exhaust port and its outlet connected to the fifth exhaust pipe.

[0043] Specifically, the nitrous oxide decomposition reactor is responsible for removing nitrous oxide from the exhaust gas.

[0044] Specifically, the second exhaust pipe should include a branch with a valve to control the amount and temperature of gas entering the nitrous oxide decomposition reactor.

[0045] The denitrification reactor is located after the nitrous oxide decomposition reactor. Its inlet is connected to the sixth exhaust pipe, and its outlet is connected to the seventh exhaust pipe.

[0046] Specifically, the denitrification reactor will be responsible for removing nitric oxide and nitrogen dioxide from the exhaust gas.

[0047] Specifically, the gas in the sixth exhaust pipe should have been cooled by the second preheater before entering the denitrification reactor.

[0048] Specifically, after passing through the denitrification reactor, the purified exhaust gas will enter the seventh exhaust pipe as the circulating gas for the entire process.

[0049] Specifically, there should be a branch line with a valve before the denitrification reactor to control the amount and temperature of gas entering the denitrification reactor.

[0050] The third preheater is located after the denitrification reactor and contains heat exchange channels.

[0051] Specifically, the first and third preheaters are responsible for cooling the purified exhaust gas in the seventh and eighth exhaust pipes for use as recirculation gas, and the third preheater can also heat the steam introduced into the adipic acid production unit, thereby reducing the total energy consumption of the adipic acid production-exhaust gas treatment process.

[0052] Specifically, the purified exhaust gas in the ninth exhaust pipe should be either discharged into the environment or continue to be used as recirculated gas, depending on the actual production situation.

[0053] The chimney is located in a branch of the tenth exhaust pipe, which has a valve to control the proportion of purified exhaust gas released into the atmosphere / as recirculated gas.

[0054] The adipic acid production tail gas purification process is as follows: After separation in a gas-liquid separator, the tail gas is mixed with fresh air / recirculated gas. The mixed gas then flows through the first preheater for initial heating. The heated tail gas is divided into two streams. One stream enters the second preheater and is heated by an electric heater. After mixing with the split gas to reach the target temperature, it enters the nitrous oxide decomposer. After removing nitrous oxide in the nitrous oxide decomposer, the tail gas undergoes a third heat exchange in the second preheater. The cooled gas then flows into the denitrification reactor. In the denitrification reactor, nitric oxide and nitrogen dioxide are removed, resulting in purified tail gas. This purified tail gas then passes through the third preheater for a fourth heat recovery, and then through the first preheater for a fifth heat exchange. Afterward, it is used as recirculated air by a circulating air pump and mixed again with the gas-liquid separated tail gas. This cycle is repeated to complete the treatment of the adipic acid production tail gas.

[0055] The principle behind the process flow described in this invention that reduces the energy consumption of adipic acid tail gas treatment is as follows: partial / complete recovery of the purified high-temperature tail gas reduces the use of low-temperature compressed air, thereby reducing energy consumption and effectively recovering waste heat; a single cycle can perform six heat exchange processes, which is higher than the actual number of heat exchange processes in existing technologies, effectively recovering the waste heat of the tail gas, and the recovered waste heat can also be used for adipic acid production, thereby reducing the total energy consumption of the adipic acid production-tail gas treatment process.

[0056] The principle behind the process flow described in this invention for treating nitrogen oxides in adipic acid tail gas is that the nitrous oxide decomposition reactor and the denitrification reactor are equipped with highly efficient catalysts for catalytic decomposition and reduction of nitrogen oxides, which can effectively remove nitrogen oxides from the tail gas at the catalyst operating temperature.

[0057] When implementing this invention, the initial startup of the adipic acid tail gas removal process requires up to 27,000 kg / h of fresh air, accounting for approximately 70% of the total tail gas. Ideally, heating this fresh air to 150°C requires approximately 111 kg of standard coal equivalent per hour (heating power approximately 771 kWh). After introducing recirculated air, the fresh air introduced into the system accounts for a maximum of 23% of the total tail gas volume. Therefore, the beneficial effect of this invention is at least a 47% saving of fresh air, approximately 74 kg of standard coal equivalent per hour, and a reduction in heating power of approximately 514 kWh. In addition, the first preheater alone saves approximately 28 kg of standard coal equivalent per hour, equivalent to approximately 194 kWh, and the third preheater, by heating adipic acid to produce steam, can further save 14 kg of standard coal equivalent per hour in adipic acid production, equivalent to approximately 97 kWh.

[0058] In addition, other patents (such as "A Catalytic Decomposition Device for Nitrogen Oxides in Adipic Acid Tail Gas", patent number: CN218608829U) also use three heat exchangers to recover waste heat from the tail gas, but directly discharge the purified tail gas, resulting in a waste of heat. After the air is reintroduced, it still needs to be heated, which increases energy consumption.

[0059] In summary, this process solves the problems of waste heat and high energy consumption in existing adipic acid tail gas treatment technologies.

[0060] In this invention, unless otherwise explicitly specified and limited, terms such as “parallel,” “connected,” “linked,” and “control” should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0061] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should be considered within the scope of protection of the present invention.

Claims

1. A process for treating nitrogen oxides in adipic acid tail gas by recovering and purifying tail gas and waste heat, characterized in that, include: The device includes: a gas-liquid separator, which functions to separate high-concentration nitrogen oxide tail gas and waste liquid; a gas-liquid separator drain tank connected to a waste liquid transfer pump for discharging wastewater; and a first exhaust pipe connected to a fresh air compressor and a circulating air compressor. The fresh air compressor and the recirculating air compressor are connected in parallel to the first exhaust pipe. The fresh air compressor is responsible for providing air when the exhaust gas treatment device is started for the first time. After the exhaust gas treatment device is running, the recirculating air compressor will introduce the purified exhaust gas as a dilution gas source into the device. The first preheater, located after the gas-liquid separator and the air compressor, is responsible for exchanging heat between the exhaust gas to be purified in the first exhaust pipe and the purified circulating gas in the ninth exhaust pipe. After heat exchange, the exhaust gas to be purified enters the next unit, and the cooled purified exhaust gas enters the circulating air compressor through the ninth exhaust pipe. The first preheater is connected to the second preheater via the second exhaust pipe; the second preheater is connected to the nitrous oxide decomposition reactor via the fifth exhaust pipe; the second preheater is connected to the nitrous oxide decomposition reactor via the sixth exhaust pipe; and the nitrous oxide decomposition reactor is connected to the third preheater via the seventh exhaust pipe. The second preheater is responsible for heat exchange between the gas in the second exhaust pipe and the fifth exhaust pipe, heating the exhaust gas to be purified in the second exhaust pipe for the second time, and cooling the exhaust gas in the fifth exhaust pipe after nitrous oxide has been removed. An electric heater, placed before the nitrous oxide decomposer, is responsible for heating the exhaust gas to be purified in the third exhaust pipe for the third time. The nitrous oxide decomposition reactor has its inlet connected to the fourth exhaust pipe and its outlet connected to the fifth exhaust pipe, and is responsible for removing nitrous oxide from the exhaust gas. The denitrification reactor, with its inlet connected to the sixth exhaust pipe and its outlet connected to the seventh exhaust pipe, is responsible for removing nitric oxide and nitrogen dioxide from the exhaust gas; the purified exhaust gas will be used as the circulating gas for the entire process. The third preheater is responsible for cooling the purified exhaust gas in the seventh exhaust pipe for use as circulating gas, and heating the steam introduced into the adipic acid production unit, thereby reducing the energy consumption of the adipic acid production-exhaust gas treatment process. The second exhaust pipe has a diversion pipe and is equipped with a valve before the second preheater to control the amount of gas entering the second preheater. The gas that is finally diverted is mixed after the electric heater to facilitate the control of the gas temperature entering the nitrous oxide decomposition reactor. A gas flow inlet branch with a valve is provided at the position of the sixth exhaust pipe before the inlet of the denitrification reactor to adjust the amount and temperature of gas entering the denitrification reactor. The tenth exhaust pipe has a branch leading to the external exhaust chimney and a valve to allow the purified exhaust gas to be released into the atmosphere. The adipic acid production tail gas purification process is as follows: After separation in a gas-liquid separator, the tail gas is mixed with fresh air / recirculated gas. The mixed gas then flows through the first preheater for initial heating. The heated tail gas is divided into two streams. One stream enters the second preheater for a second heat exchange, and after being heated by an electric heater, it mixes with the split gas and enters the nitrous oxide decomposer. After removing nitrous oxide in the nitrous oxide decomposer, the tail gas undergoes a third heat exchange in the second preheater. The cooled gas then flows into the denitrification reactor. After the tail gas flows into the denitrification reactor, nitric oxide and nitrogen dioxide are removed, resulting in purified tail gas. The purified tail gas then passes through the third preheater for a fourth heat recovery, and then through the first preheater for a fifth heat exchange. After passing through the circulating air pump as recirculated gas, it mixes again with the gas-liquid separated tail gas. This cycle is repeated to complete the treatment of the adipic acid production tail gas. The third preheater can provide the steam heating required for adipic acid production.

2. The process according to claim 1, characterized in that, The second exhaust pipe has a diversion pipe and is equipped with a valve before the second preheater to control the amount of gas entering the second preheater. The gas that is finally diverted is mixed after the electric heater to facilitate the control of the gas temperature entering the nitrous oxide decomposition reactor.

3. The process according to claim 1, characterized in that, The tenth exhaust pipe has a branch leading to the external exhaust chimney and a valve to allow some of the purified exhaust gas to be released into the atmosphere.

4. The process according to claim 1, characterized in that, A valve is installed after the fresh air compressor. When the nitrogen oxide purification treatment device is running, the valve is adjusted to control the amount of fresh air input to the fresh air compressor so that the purified exhaust gas can replace the fresh air and dilute the nitrogen oxide-containing exhaust gas.

5. The process according to claim 1, characterized in that, It is equipped with a circulating air compressor. When the nitrogen oxide purification treatment device is running, the purified exhaust gas will be continuously circulated in the device as circulating air compressor to dilute the nitrogen oxide-containing exhaust gas.

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