CN221684935U - Continuous oxidation tail gas nitrogen production device of pseudocumene - Google Patents

Abstract

The utility model discloses a production device for preparing nitrogen by continuously oxidizing off-gas of pseudocumene in the field of preparation devices of liquid nitrogen or high-purity nitrogen, which comprises a deacidification unit, a dehydration drying unit, a nitrogen compression unit and a liquefaction rectification unit. The nitrogen-rich tail gas after continuous oxidation of the pseudocumene enters an absorption tower firstly, CO ₂ and acetic acid in the nitrogen-rich tail gas are removed through absorption, substances such as water and dimethylbenzene are removed through a molecular sieve absorption tower, then the gas is compressed through a nitrogen compressor, heat exchange is performed in a condenser II to form low-temperature nitrogen, then the low-temperature nitrogen is subjected to secondary heat exchange through a heat exchange component II to form liquid nitrogen or a vapor-liquid mixture, the liquid nitrogen or the vapor-liquid mixture enters a rectifying tower, the liquid nitrogen or the vapor-liquid mixture is rectified in the rectifying tower, and other impurity gases in the nitrogen are further removed through repeated evaporation and condensation liquefaction, and meanwhile liquid nitrogen and high-purity nitrogen products are obtained. The device effectively utilizes the tail gas generated in the production of trimellitic anhydride to recycle resources, and can obtain better economic benefit.

Description

A device for producing nitrogen from tail gas by continuous oxidation of trimethylol

Technical Field

The utility model relates to a device for preparing liquid nitrogen or high-purity nitrogen, in particular to a device for preparing nitrogen by utilizing tail gas after continuous oxidation of trimethylol.

Background Art

At present, the production of liquid nitrogen and high-purity nitrogen mainly adopts air separation units, which are industrial equipment used to separate the various gas components in the air to obtain oxygen, nitrogen, argon and other gases. At present, the most commonly used air separation method is cryogenic distillation, which uses the compression cycle deep freezing method to turn the air into liquid. According to the different boiling points of the various components in the air, oxygen, nitrogen, argon and other gases are gradually separated and produced from the liquid air through cryogenic distillation.

The principle of air distillation is: due to the difference in boiling points, the order of evaporation of oxygen, nitrogen and argon is: nitrogen>argon>oxygen, and the order of condensation is: oxygen>argon>nitrogen; if the saturated steam with a higher temperature is in contact with the saturated liquid with a lower temperature, the steam releases heat and partially condenses, while the liquid absorbs heat and partially evaporates; when the steam is partially condensed, the high-boiling point oxygen component in the steam condenses more into the liquid phase, and the low-boiling point nitrogen component in the liquid phase evaporates more into the gas phase, so that the concentration of the nitrogen component in the gas phase increases and the concentration of the oxygen component in the liquid phase increases; if such partial evaporation and partial condensation processes are performed multiple times, the concentration of the nitrogen component in the gas phase continues to increase, and at the same time, the concentration of the oxygen component in the liquid phase continues to increase, and finally the purpose of separating nitrogen and oxygen is achieved. The main equipment for achieving distillation is the distillation tower. Each plate in the tower provides a place for gas-liquid contact to partially evaporate and partially condense, and finally a high-purity nitrogen product is obtained at the top of the tower, and a high-purity oxygen product is obtained at the bottom of the tower.

CN103062990A discloses a liquid air separation device, which includes a distillation tower, which includes an upper tower, a lower tower and a main condenser evaporator. One way of the product nitrogen outlet of the upper tower is connected to a main heat exchanger and a product nitrogen output pipeline in sequence, and the other way is connected to a liquefaction heat exchanger, a circulating nitrogen compressor, a boosting end of a booster expander, a booster aftercooler, a liquefaction heat exchanger, a low-temperature air conditioner, and a liquefaction heat exchanger in sequence.

CN102788476A discloses an air separation process in which a cryogenic air separation device mainly produces high-purity nitrogen and also produces liquid oxygen. The process steps are as follows: the raw air is filtered and purified and then divided into three paths; the first path directly enters the cold box, the air passes through the main heat exchanger to exchange heat with the reflux gas, is cooled to the liquefaction temperature, enters the nitrogen tower to participate in distillation to obtain pure nitrogen and liquid nitrogen products; the second path is pressurized by a turbine expander and then cooled to the liquefaction temperature, and then enters the nitrogen tower to participate in distillation to obtain pure nitrogen and oxygen-enriched liquid air; part of the oxygen-enriched air that enters the oxygen tower to participate in distillation is separated again in the oxygen tower, and then passes through the cooler and the main heat exchanger for reheating before exiting the fractionation tower; the liquid oxygen product is obtained at the bottom of the oxygen tower; a small amount of air in the third path goes to the instrument air system as instrument air and sealing gas.

CN104296500A discloses a device and method for deep cold separation and purification of nitrogen and liquid nitrogen. The raw material of the method is air. The air is compressed by an air compression system, cooled by a precooling system, and removed from impurities by a purification system before entering a fractionation tower system. The gas entering the fractionation tower system is divided into two parts: one part enters the supercharging end and is supercharged, then enters the main heat exchanger after heat exchange in a cooler, is extracted from the middle and lower part of the main heat exchanger and enters the expansion end for adiabatic expansion, and the expanded air is reheated in the main heat exchanger and sent out of the cold box; one part of the air directly enters the main heat exchanger and is cooled to the liquefaction point before entering a single-stage distillation tower for distillation. The nitrogen product is extracted from the top of the single-stage distillation tower, reheated to room temperature by the main heat exchanger, and then enters the nitrogen collection unit through a valve. The liquid nitrogen product is extracted from the main cooling liquid nitrogen side, and is supercooled by a liquid nitrogen supercooler and a small portion of the liquid nitrogen returned, and then enters the liquid nitrogen collection unit through a valve.

In the prior art, trimellitic anhydride is produced by continuous oxidation of trimethylol in an oxygen-rich environment. Air is one of its raw materials. After the oxygen is consumed, medium-pressure nitrogen-rich tail gas is discharged. Currently, it is vented, and the characteristics of the tail gas with a nitrogen content of more than 92% and an oxygen concentration of less than 0.5% are not utilized to fully tap the economic value of the tail gas.

The shortcomings of the existing technology are: on the one hand, the cost of separating nitrogen from air is high and the energy consumption is large; on the other hand, the nitrogen with increased purity in the production of trimellitic anhydride is discharged in vain, resulting in a waste of resources.

Utility Model Content

The utility model aims to provide a nitrogen production device for the tail gas from the continuous oxidation of trimethylbenzene, which can utilize the tail gas produced by the continuous oxidation of trimethylbenzene to simultaneously prepare liquid nitrogen and high-purity nitrogen, so as to achieve the purpose of full utilization of resources.

The purpose of the utility model is achieved as follows: a device for producing nitrogen from tail gas of unsymmetrical trimethylbenzene by continuous oxidation, comprising a deacidification unit, a dehydration and drying unit, a nitrogen compression unit and a liquefaction and distillation unit; wherein,

Deacidification unit: including an absorption tower and a regeneration tower; a raw material inlet is provided in the middle and lower part of the absorption tower, the raw material inlet is connected to the tail gas outlet of the unsymmetrical trimethylbenzene continuous oxidation reaction device, and the top of the absorption tower is connected to the dehydration and drying unit after passing through the tower top liquid separator; the bottom outlet of the absorption tower is connected to the tube side inlet of the lean-rich liquid heat exchanger, and the tube side outlet of the lean-rich liquid heat exchanger is connected to the middle and upper inlet of the regeneration tower, the top of the regeneration tower is connected to the tower top reflux tank through condenser 1, the reflux port at the bottom of the tower top reflux tank is connected to the upper part of the regeneration tower through the reflux pipe, and the top of the tower top reflux tank is provided with an air outlet; the bottom outlet of the regeneration tower is connected to the shell side inlet of the lean-rich liquid heat exchanger, and the shell side outlet of the lean-rich liquid heat exchanger is connected to the upper part of the absorption tower after passing through the lean liquid cooler;

The dehydration and drying unit comprises a molecular sieve desorption tower, the bottom inlet of the molecular sieve desorption tower is connected to the top outlet of the tower top liquid separation tank;

Nitrogen compression unit: comprising a turbine and a nitrogen compressor, the turbine is drivingly connected to the nitrogen compressor, and the outlet of the nitrogen compressor is connected to the inlet of the second condenser;

The liquefaction distillation unit comprises a heat exchange gas header and a distillation tower. The heat exchange gas header is provided with a heat exchange component 1 and a heat exchange component 2. The inlet of the heat exchange component 1 is connected to the top outlet of the molecular sieve desorption tower, and the outlet of the heat exchange component 1 is connected to the inlet of the nitrogen compressor; the inlet of the heat exchange component 2 is connected to the outlet of the condenser 2, and the outlet of the heat exchange component 2 is connected to the nitrogen inlet of the distillation tower; the upper part of the distillation tower is provided with a nitrogen outlet, and the middle and lower parts are provided with a liquid nitrogen outlet.

When the utility model is working, the nitrogen-rich tail gas of trimellitic anhydride after continuous oxidation by introducing air first enters the absorption tower, where _CO2 and acetic acid are removed through absorption, and then water and xylene and other substances are removed through the molecular sieve adsorption tower. The gas is then compressed by the nitrogen compressor, and then heat exchanged in the condenser 2 to form low-temperature nitrogen. Then, it is heat exchanged again through the heat exchange component 2 to form liquid nitrogen or a vapor-liquid mixture that enters the distillation tower, where it is rectified, and other impurity gases in the nitrogen are further removed through repeated evaporation, condensation and liquefaction, and liquid nitrogen and high-purity nitrogen products are obtained at the same time. The device effectively utilizes the tail gas during the production of trimellitic anhydride, recycles resources, and can achieve better economic benefits. Compared with the prior art, the beneficial effects of the utility model are:

1. When the air is introduced into the continuous oxidation of trimethylol, it consumes oxygen itself, and it is also a process of purifying nitrogen. On this basis, further purifying the nitrogen can make the finished product purer. The purity of liquid nitrogen is ≥99.995%, and the purity of nitrogen is as high as 99.999%.

2. Lower energy consumption: The average energy consumption of a ton of liquid air separation products is about 600Kw/h in conventional electric air separation. Using the nitrogen-rich tail gas of this project to produce air separation products is more energy-saving than conventional all-electric air separation, with an average energy consumption of about 430Kw/h per ton of product, and a 30% power saving, with significant energy-saving effects. Resources are effectively utilized.

Further, the distillation tower includes a three-section tower body arranged vertically, which are an upper tower, a middle tower and a lower tower respectively. The diameter of the middle tower is larger than that of the upper tower and the lower tower. Several layers of packing layers are arranged in the upper tower, the nitrogen inlet is arranged in the middle of the packing layer, and the nitrogen outlet is arranged above the packing layer; at least two layers of condensation heat exchange layers are arranged in the middle tower, the condensation heat exchange layer includes a bottom plate, a partition and a cryogenic heat exchanger, the partition is arranged in a cylindrical shape on the upper side of the bottom plate, the cryogenic heat exchanger is arranged in a space enclosed by the partition, and a plurality of micropores penetrating the bottom plate are arranged on the bottom plate outside the partition; several layers of baffle components are arranged in the lower tower, the baffle components include a horizontally arranged upper baffle and a lower baffle, the upper baffle extends to above the lower baffle, a longitudinal baffle is arranged on the lower baffle, a liquid nitrogen pool for accommodating liquid nitrogen is formed between the longitudinal baffle, the lower baffle and the inner wall of the tower body, an overflow channel is formed between the longitudinal baffle and the upper baffle, and the liquid nitrogen outlet is connected to one of the liquid nitrogen pools in the middle of the lower tower. In this scheme, in the packing layer, the liquid nitrogen is in a vapor-liquid mixed state, which is continuously vaporized and condensed, so that part of the impurity gas condenses downward. During the condensation and downward process, the high-purity nitrogen goes upward and leaves from the nitrogen outlet for collection; part of the liquid nitrogen and a small amount of impurity gas are condensed downward, and the temperature at the bottom of the distillation tower is inconsistent with the temperature in the middle, so that high-purity liquid nitrogen can be separated, and the impurity gas volume is stored at the bottom of the distillation tower.

Furthermore, the discharge port provided at the bottom of the distillation tower is connected to the heat exchange gas header, and after heat exchange with heat exchange component 1 and heat exchange component 2, is connected to the molecular sieve regeneration gas inlet through a pipeline. A purge gas outlet is provided at the top of the distillation tower, and the purge gas outlet is connected to the molecular sieve regeneration gas inlet. This part of the gas can be used for the regeneration of the molecular sieve provided in the molecular sieve adsorption tower.

Furthermore, more than two molecular sieve desorption towers are arranged in parallel. Since the molecular sieve needs to be regenerated after reaching adsorption saturation, the molecular sieve desorption tower realizes the adsorption-regeneration alternating cycle by partially opening and partially keeping in reserve. Each molecular sieve desorption tower is set with an adsorption cycle, and when the adsorption cycle is reached, it is switched to the regenerated reserve adsorption tower immediately, thereby improving work efficiency.

Furthermore, the upper sections of the tower bodies corresponding to the absorption tower and the regeneration tower are provided with a plurality of fillers, the lower sections are hollow sections, the raw material inlet is connected to the hollow section of the absorption tower; and a reboiler is provided outside the hollow section of the regeneration tower.

Furthermore, the pipelines connecting the deacidification unit, the dehydration and drying unit, the nitrogen compression unit and the liquefaction and distillation unit are provided with pumps and valves. In order to realize automatic control, sensors for flow, temperature, pressure detection and the like may also be provided on the pipelines.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a flowchart of the utility model.

FIG. 2 is a schematic diagram of the local structure of a distillation tower.

In the figure, 1 absorption tower, 2 tower top liquid separation tank, 3 lean liquid cooler, 4 lean and rich liquid heat exchanger, 5 regeneration tower, 6 reboiler, 7 condenser 1, 8 tower top reflux tank, 9 molecular sieve desorption tower, 10 nitrogen compressor, 11 turbine, 12 condenser 2, 13 heat exchange gas header, 1301 heat exchange component 1, 1302 heat exchange component 2, 14 distillation tower, 1401 packing layer, 1402 cryogenic heat exchanger, 1403 partition, 1404 bottom plate, 1405 longitudinal baffle, 1406 upper baffle, 1407 lower baffle, 1408 nitrogen inlet, 1409 nitrogen outlet, 1410 liquid nitrogen outlet, 1411 purge gas outlet, 1412 discharge outlet; A deacidification unit, B dehydration and drying unit, C nitrogen compression unit, D liquefaction distillation unit.

DETAILED DESCRIPTION

As shown in Figure 1-2, this is a nitrogen production device for the continuous oxidation of trimethylol tail gas, including a deacidification unit A, a dehydration and drying unit B, a nitrogen compression unit C and a liquefaction and distillation unit D. The specific structure is as follows:

Deacidification unit A: includes an absorption tower 1 and a regeneration tower 5; a raw material inlet is provided in the middle and lower part of the absorption tower 1, and the raw material inlet is connected to the tail gas outlet of the unsymmetrical trimethylbenzene continuous oxidation reaction device, and the top of the absorption tower 1 is connected to the dehydration and drying unit B after passing through the tower top liquid separator 2; the bottom outlet of the absorption tower 1 is connected to the tube side inlet of the lean-rich liquid heat exchanger 4 (shell and tube heat exchanger), and the tube side outlet of the lean-rich liquid heat exchanger 4 is connected to the middle and upper inlet of the regeneration tower 5, and the top of the regeneration tower 5 is connected to the tower top reflux tank 8 through a condenser 7, and the reflux port at the bottom of the tower top reflux tank 8 is connected to the upper part of the regeneration tower 5 through a reflux pipe, and the top of the tower top reflux tank 8 is provided with an outlet; the bottom outlet of the regeneration tower 5 is connected to the shell side inlet of the lean-rich liquid heat exchanger 4, and the shell side outlet of the lean-rich liquid heat exchanger 4 is connected to the upper part of the absorption tower 1 after passing through the lean liquid cooler 3;

Dehydration and drying unit B: comprising a molecular sieve desorption tower 9, the bottom inlet of the molecular sieve desorption tower 9 is connected to the top outlet of the tower top liquid separation tank 2;

Nitrogen compression unit C: includes a turbine 11 and a nitrogen compressor 10, the turbine 11 is drivingly connected to the nitrogen compressor 10, and the outlet of the nitrogen compressor 10 is connected to the inlet of the second condenser 12;

Liquefaction distillation unit D: includes a heat exchange gas manifold 13 and a distillation tower 14. The heat exchange gas manifold 13 is provided with a heat exchange component 1 1301 and a heat exchange component 2 1302. The heat exchange component 1 1301 and the heat exchange component 2 1302 can be plate heat exchangers or coil heat exchangers. The inlet of the heat exchange component 1 1301 is connected to the top outlet of the molecular sieve desorption tower 9, and the outlet of the heat exchange component 1 1301 is connected to the inlet of the nitrogen compressor 10; the inlet of the heat exchange component 2 1302 is connected to the outlet of the condenser 2 12, and the outlet of the heat exchange component 2 1302 is connected to the nitrogen inlet 1408 of the distillation tower 14; the distillation tower 14 is provided with a nitrogen outlet 1409 at the top and a liquid nitrogen outlet 1410 at the middle and lower parts.

The distillation tower 14 includes a three-stage tower body arranged vertically, which are an upper tower, a middle tower and a lower tower. The diameter of the middle tower is larger than that of the upper tower and the lower tower. The upper tower is provided with several layers of packing layers 1401, the nitrogen inlet 1408 is arranged in the middle of the packing layer 1401, and the nitrogen outlet 1409 is arranged above the packing layer 1401; at least two layers of condensation heat exchange layers are arranged in the middle tower, and the condensation heat exchange layers include a bottom plate 1404, a partition 1403 and a cryogenic heat exchanger 1402, the partition 1403 is arranged in a cylindrical shape on the upper side of the bottom plate 1404, and the cryogenic heat exchanger 1402 is arranged in a space enclosed by the partition 1403 A plurality of micropores penetrating the bottom plate 1404 are provided on the bottom plate 1404 outside the partition 1403; a plurality of layers of baffle components are provided in the lower tower, and the baffle components include an upper baffle 1406 and a lower baffle 1407 arranged horizontally, the upper baffle 1406 extends to above the lower baffle 1407, a longitudinal baffle 1405 is provided on the lower baffle 1407, a liquid nitrogen pool for containing liquid nitrogen is formed between the longitudinal baffle 1405, the lower baffle 1407 and the inner wall of the tower body, an overflow channel is formed between the longitudinal baffle 1405 and the upper baffle 1406, and a liquid nitrogen outlet 1410 is connected to one of the liquid nitrogen pools in the middle of the lower tower. In this solution, in the packing layer 1401, the liquid nitrogen is in a vapor-liquid mixed state, which is continuously vaporized and condensed, so that part of the impurity gas condenses and moves downward. During the condensation and downward process, the high-purity nitrogen moves upward and leaves from the nitrogen outlet 1409 to be collected. Part of the liquid nitrogen and a small amount of impurity gas are condensed and move downward, and the temperature at the bottom and the middle of the distillation tower 14 are inconsistent, so that high-purity liquid nitrogen can be separated, and the impurity gas volume is stored at the bottom of the distillation tower 14.

The exhaust port 1412 provided at the bottom of the distillation tower 14 is connected to the heat exchange gas header 13, and after heat exchange with the heat exchange component 1 1301 and the heat exchange component 2 1302, it is connected to the molecular sieve regeneration gas inlet through a pipeline. A purge gas outlet 1411 is provided at the top of the distillation tower 14, and the purge gas outlet 1411 is connected to the molecular sieve regeneration gas inlet. The gas discharged from the purge gas outlet 1411 and the gas discharged from the exhaust port 1412 at the bottom of the distillation tower 14 are used for the regeneration of the molecular sieve set in the molecular sieve adsorption tower after heat exchange.

There are two molecular sieve desorption towers 9 connected in parallel, or more than two. Since the molecular sieve needs to be regenerated after reaching adsorption saturation, the molecular sieve desorption tower 9 realizes the adsorption-regeneration alternating cycle by partially opening and partially keeping in reserve. Each molecular sieve desorption tower 9 is set with an adsorption cycle, and when the adsorption cycle is reached, it is switched to the regenerated reserve adsorption tower immediately, which improves work efficiency.

The upper section of the tower body corresponding to the absorption tower 1 and the regeneration tower 5 is provided with a plurality of fillers, and the lower section is a cavity section. The raw material inlet is connected to the cavity section of the absorption tower 1; a reboiler 6 is provided outside the cavity section of the regeneration tower 5.

The pipelines connecting the deacidification unit A, the dehydration and drying unit B, the nitrogen compression unit C and the liquefaction and distillation unit D may be provided with multiple pumps and valves for gas and liquid transportation. In order to realize automatic control, sensors for flow, temperature, pressure detection and the like may also be provided on the pipelines.

During operation, the nitrogen-rich tail gas of partial trimethylol after continuous oxidation by introducing air first enters the absorption tower 1. The volume content of nitrogen in the tail gas is more than 92%, and the volume content of oxygen is less than 0.5%. At the same time, the tail gas contains a small amount of _CO2 , _H2O , acetic acid, xylene and other organic gases. _CO2 has a corrosive effect on equipment pipelines, and because of its high boiling point, it is easy to precipitate into solids during the cooling process, so it is removed first; the tail gas enters from the lower part of the absorption tower 1 and passes through the absorption tower 1 from bottom to top; the composite amine solution (lean liquid) in the absorption tower 1 enters from the upper part of the absorption tower 1 and passes through the absorption tower 1 from top to bottom. The counter-flowing composite amine solution and the raw gas are fully contacted in the absorption tower 1, and the _CO2 in the raw gas is absorbed and enters the liquid phase. The unabsorbed components are drawn out from the top of the absorption tower 1 and enter the top liquid separator 2, and the temperature is reduced to below 40°C and enter the dehydration and drying unit B.

The composite amine solution after absorbing _CO2 is called rich liquid. After coming out from the bottom of absorption tower 1, it exchanges heat with the solution (lean liquid) flowing out from the bottom of regeneration tower 5 in the lean-rich liquid heat exchanger 4, and then is heated to 90-98°C to go to regeneration tower 5, where it is stripped and regenerated until the rich liquid is regenerated into lean liquid. The lean liquid out of regeneration tower 5 is cooled to 45-65°C through the lean-rich liquid heat exchanger 4 and the lean liquid cooler 3, and then enters from the top of absorption tower 1 to complete the amine liquid cycle.

Acidic gas is discharged from the top outlet of the regeneration tower 5, and after being cooled, enters the top reflux tank 8, the acidic gas is discharged from the top, and the condensate is refluxed to the regeneration tower 5, and CO ₂ and acetic acid are removed.

In the dehydration and drying unit B, the impurities such as moisture, trace _CO2 and xylene in the gas are deeply removed by the molecular sieve desorption tower 9. The molecular sieve is the core working component of the molecular sieve desorption tower 9. After the molecular sieve reaches adsorption saturation, it needs to be regenerated. The regeneration gas is introduced through the molecular sieve regeneration gas inlet, and the molecular sieve is regenerated by the heater temperature change, pressure change or reverse adsorption. The molecular sieve desorption tower 9 works in a "one-on-one-standby" mode to achieve an adsorption-regeneration alternating cycle.

The dehydrated and dried nitrogen first passes through the heat exchange component 1301 to reduce its temperature, and then enters the nitrogen compressor 10 for compression. After compression, it is condensed to form low-temperature nitrogen or a vapor-liquid mixture and then enters the liquefaction distillation unit D.

In the liquefaction distillation unit D, nitrogen is repeatedly vaporized and condensed, and trace amounts of non-condensable gas gather at the top and can leave from the purge gas outlet 1411, and high-concentration nitrogen is discharged from the nitrogen outlet 1409. Liquid nitrogen flows down step by step, passes through the packing layer 1401, is further cooled by the cryogenic heat exchanger 1402 in the middle tower, and overflows downward over the partition 1403 to enter the lower tower, where it gradually overflows downward. In the process of overflowing downward, impurities in the liquid nitrogen gradually accumulate at the bottom of the tower because their boiling point is higher than that of nitrogen, and can then be used as molecular sieve regeneration gas, and high-purity liquid nitrogen can be discharged from the liquid nitrogen outlet 1410, the liquid nitrogen is stored in the liquid nitrogen storage tank, and the nitrogen is sent to the pipeline network, and the purge gas is used as molecular sieve regeneration gas.

Compared with the prior art, the beneficial effects of the present invention are:

1. When the air is introduced into the continuous oxidation of trimethylol, it consumes oxygen itself, and it is also a process of purifying nitrogen. On this basis, further purifying the nitrogen can make the finished product purer. The purity of liquid nitrogen is ≥99.995%, and the purity of nitrogen is as high as 99.999%.

2. Lower energy consumption: The average energy consumption of a ton of liquid air separation products is about 600Kw/h in conventional electric air separation. Using the nitrogen-rich tail gas of this project to produce air separation products is more energy-saving than conventional all-electric air separation, with an average energy consumption of about 430Kw/h per ton of product, and a 30% power saving, with significant energy-saving effects. Resources are effectively utilized.

The present utility model is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed in the present utility model, technicians in this field can make some substitutions and deformations to some technical features therein according to the disclosed technical content without creative labor, and these substitutions and deformations are all within the protection scope of the present utility model.

Claims (7)

1. A device for producing nitrogen from tail gas of unsymmetrical trimethylbenzene by continuous oxidation, characterized in that it comprises a deacidification unit, a dehydration and drying unit, a nitrogen compression unit and a liquefaction and distillation unit; wherein: Deacidification unit: including an absorption tower and a regeneration tower; a raw material inlet is provided in the middle and lower part of the absorption tower, the raw material inlet is connected to the tail gas outlet of the unsymmetrical trimethylbenzene continuous oxidation reaction device, and the top of the absorption tower is connected to the dehydration and drying unit after passing through the top liquid separator; the bottom outlet of the absorption tower is connected to the tube side inlet of the lean-rich liquid heat exchanger, the tube side outlet of the lean-rich liquid heat exchanger is connected to the middle and upper inlet of the regeneration tower, the top of the regeneration tower is connected to the top reflux tank through a condenser, the reflux port at the bottom of the top reflux tank is connected to the upper part of the regeneration tower through a reflux pipe, and an air outlet is provided at the top of the top reflux tank; the bottom outlet of the regeneration tower is connected to the shell side inlet of the lean-rich liquid heat exchanger, and the shell side outlet of the lean-rich liquid heat exchanger is connected to the upper part of the absorption tower after passing through a lean liquid cooler; The dehydration and drying unit comprises a molecular sieve desorption tower, the bottom inlet of the molecular sieve desorption tower is connected to the top outlet of the tower top liquid separation tank; Nitrogen compression unit: comprising a turbine and a nitrogen compressor, the turbine is drivingly connected to the nitrogen compressor, and the outlet of the nitrogen compressor is connected to the inlet of the second condenser; The liquefaction distillation unit comprises a heat exchange gas header and a distillation tower. The heat exchange gas header is provided with a heat exchange component 1 and a heat exchange component 2. The inlet of the heat exchange component 1 is connected to the top outlet of the molecular sieve desorption tower, and the outlet of the heat exchange component 1 is connected to the inlet of the nitrogen compressor; the inlet of the heat exchange component 2 is connected to the outlet of the condenser 2, and the outlet of the heat exchange component 2 is connected to the nitrogen inlet of the distillation tower; the upper part of the distillation tower is provided with a nitrogen outlet, and the middle and lower parts are provided with a liquid nitrogen outlet. 2. A nitrogen production device for continuous oxidation of tail gas from partial trimethylbenzene according to claim 1, characterized in that: the distillation tower comprises a three-stage tower body arranged vertically, namely an upper tower, a middle tower and a lower tower, the diameter of the middle tower is larger than the diameters of the upper tower and the lower tower, the upper tower is provided with a plurality of packing layers, the nitrogen inlet is arranged in the middle of the packing layer, and the nitrogen outlet is arranged above the packing layer; at least two condensation heat exchange layers are arranged in the middle tower, the condensation heat exchange layers include a bottom plate, a partition and a cryogenic heat exchanger, the partition is arranged in a cylindrical shape on the upper side of the bottom plate, the cryogenic heat exchanger is arranged in a space enclosed by the partition, and a plurality of micropores penetrating the bottom plate are arranged on the bottom plate outside the partition; a plurality of baffle components are arranged in the lower tower, the baffle components include an upper baffle and a lower baffle arranged horizontally, the upper baffle extends to above the lower baffle, a longitudinal baffle is arranged on the lower baffle, a liquid nitrogen pool for accommodating liquid nitrogen is formed between the longitudinal baffle, the lower baffle and the inner wall of the tower body, an overflow channel is formed between the longitudinal baffle and the upper baffle, and the liquid nitrogen outlet is connected to one of the liquid nitrogen pools in the middle of the lower tower. 3. A device for producing nitrogen from tail gas by continuous oxidation of unsymmetrical trimethylbenzene according to claim 1, characterized in that: the exhaust port arranged at the bottom of the distillation tower is connected to the heat exchange gas header, and after heat exchange with heat exchange component 1 and heat exchange component 2, is connected to the molecular sieve regeneration gas inlet through a pipeline. 4. A device for producing nitrogen from tail gas by continuous oxidation of partial trimethylbenzene according to any one of claims 1 to 3, characterized in that a purge gas outlet is provided at the top of the distillation tower, and the purge gas outlet is connected to a molecular sieve regeneration gas inlet. 5. A device for producing nitrogen from tail gas by continuous oxidation of unsymmetrical trimethylbenzene according to any one of claims 1 to 3, characterized in that: more than two molecular sieve desorption towers are arranged in parallel. 6. A device for producing nitrogen from unsymmetrical trimethylbenzene by continuous oxidation of tail gas according to any one of claims 1 to 3, characterized in that: a plurality of fillers are arranged in the upper section of the tower body corresponding to the absorption tower and the regeneration tower, the lower section is a cavity section, and the raw material inlet is connected to the cavity section of the absorption tower; a reboiler is arranged outside the cavity section of the regeneration tower. 7. A device for producing nitrogen from tail gas by continuous oxidation of unsymmetrical trimethylbenzene according to any one of claims 1 to 3, characterized in that pumps and valves are provided on the pipelines connecting the deacidification unit, the dehydration and drying unit, the nitrogen compression unit and the liquefaction and distillation unit.