Technology for recycling N-formylmorpholine waste liquid

Abstract

The invention belongs to the technical field of energy conservation and environmental protection, and relates to an N-formylmorpholine waste liquid resource recycling process, which comprises the following steps: adding an N-formylmorpholine waste liquid into a batch rectification tower, adding an inhibitor for rectification, and after non-target components are extracted from the tower top, remaining in a tower kettle as a batch-rectified crude product N-formylmorpholine; a crude product N-formylmorpholine subjected to batch rectification is conveyed into a continuous rectification tower, light components are extracted from the tower top, rectification residues are discharged from a tower kettle, and a regenerated product N-formylmorpholine is discharged from a side line on a tower plate at the bottom of the continuous rectification tower. The method has the beneficial effects that compared with a traditional incineration process for treating the N-formylmorpholine waste liquid, resource utilization of the waste liquid is achieved, and the utilization rate of materials is increased; and meanwhile, the risk of environmental pollution is reduced, and the emission of CO2 is also reduced. In order to inhibit the side reaction in the rectification process of the N-formylmorpholine, an organic solvent is also added into the rectification tower as an inhibitor of the side reaction.

Description

Technical Field

[0001] The invention belongs to the technical field of energy conservation and environmental protection, and specifically relates to a process for resource recycling of N-formylmorpholine waste liquid. Background Art

[0002] N-formylmorpholine (NFM) is an important organic solvent and fine chemical raw material. Generally, N-formylmorpholine is colorless and transparent, and has the chemical properties of amide. In alkaline aqueous solution, the aqueous solution of N-formylmorpholine is easily hydrolyzed into morpholine and formic acid, and its aqueous solution is weakly alkaline.

[0003] N-formylmorpholine not only has excellent selectivity, thermal stability and chemical stability, but also is non-toxic and non-corrosive, so it is widely used in many fields. In the petrochemical industry, since N-formylmorpholine is miscible with aliphatic hydrocarbons, aromatic hydrocarbons and water, and has good solubility and extraction properties, it is widely used in the desulfurization of natural gas and natural gas condensate, gasoline, synthesis gas, flue gas, as well as in synthetic fiber, organic synthesis and other processes. In addition, since N-formylmorpholine can reduce the volatility of aromatic hydrocarbons and improve the separation coefficient between aromatic hydrocarbons and non-aromatic hydrocarbons, it is also widely used in the extraction process of aromatic hydrocarbons (such as benzene, toluene, xylene, etc.).

[0004] Based on the excellent physical and chemical properties of N-formylmorpholine, it is widely used in the petrochemical industry, which inevitably produces a large amount of waste solvents containing N-formylmorpholine. The final disposal method of this waste liquid is incineration, which has three major defects: safety hazards, environmental pollution and waste of resources.

[0005] N-formylmorpholine waste liquid contains low-boiling-point components and is flammable and explosive, so there is a great risk of fire and explosion during the incineration process. For example, when the low-boiling-point substance methyl ethyl ketone in the waste liquid evaporates to a certain concentration, it may cause flashover and explosion when it encounters static electricity, sparks or high-temperature objects.

[0006] During the incineration process of waste liquid, if the ventilation and exhaust system does not meet the requirements, it may lead to the accumulation of flammable and explosive gases, which may easily cause accidents. In addition, excessive storage or improper storage of waste liquid may also easily cause environmental pollution. Summary of the invention

[0007] In order to solve the defect in the prior art that N-formylmorpholine waste liquid cannot be recycled and utilized as a resource, the present invention provides a process for recycling and utilizing N-formylmorpholine waste liquid as a resource.

[0008] The technical scheme adopted by the present invention is as follows: a process for resource recycling of N-formylmorpholine waste liquid, wherein the N-formylmorpholine waste liquid is added to an intermittent distillation tower, and an inhibitor is added for distillation, and after non-target components are extracted from the tower top, crude N-formylmorpholine obtained by intermittent distillation is retained in the tower bottom;

[0009] The crude N-formylmorpholine from intermittent distillation is transported to a continuous distillation tower, the light component is taken out from the top of the tower, the distillation residue is taken out from the bottom of the tower, and the regenerated product N-formylmorpholine is discharged from the side line on the tower plate at the bottom of the continuous distillation tower.

[0010] Furthermore, the inhibitor comprises a mixture of polydimethylsiloxane and polyether silicone oil.

[0011] Specifically, the dosage of the inhibitor additive accounts for 3-5% of the mass fraction of the N-formylmorpholine waste liquid.

[0012] Furthermore, the intermittent distillation tower has 12 theoretical plates, and the top pressure is controlled at 95-100 kPa.

[0013] Preferably, the top temperature of the intermittent distillation tower is first controlled to be below 50°C, the reflux ratio is 0.5-1, and non-condensable gases and light hydrocarbon components are collected by a micro-negative pressure system; the top temperature is then controlled to be 70-74°C, the reflux ratio is 0.5-1, and crude methyl ethyl ketone is produced; the top temperature is then controlled to be 75±1°C, the reflux ratio is 3, and finished methyl ethyl ketone is produced; as the distillation proceeds, the bottom and top temperatures continue to rise, the bottom temperature is controlled to be below 170°C, and when the top temperature exceeds 77°C, the reflux ratio is reduced to 2, and all the produced components are treated as impurities until no droplets are produced at the top of the tower, and the intermittent distillation tower is stopped.

[0014] Furthermore, the continuous distillation tower has 30 theoretical plates.

[0015] Preferably, the bottom pressure of the continuous distillation tower is controlled at 20-23 kPa, and the reflux ratio is controlled at 2-3.

[0016] Furthermore, the regenerated product N-formylmorpholine is discharged from the side line on 25 to 29 tower plates.

[0017] Preferably, the heat exchange medium in the reboiler of the continuous distillation tower after heat exchange is transported to the reboiler of the intermittent distillation tower as a heat source.

[0018] Preferably, the heat exchange medium in the top condenser of the intermittent distillation tower is transported to the raw material tank as a heat source.

[0019] Beneficial effects: Compared with the traditional incineration process for disposing N-formylmorpholine waste liquid, the present invention realizes the resource utilization of waste liquid and improves the utilization rate of materials; at the same time, it reduces the risk of environmental pollution and reduces the emission of CO2. In order to inhibit the side reaction in the distillation process of N-formylmorpholine, the present invention also adds an organic solvent into the distillation tower as an inhibitor of the side reaction. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with specific implementation methods. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative changes belong to the protection scope of the present invention.

[0021] This process consists of an intermittent distillation system and a continuous distillation system. The two systems are combined to produce and recycle N-formylmorpholine waste liquid. The waste liquid is pumped from the raw material storage tank to the intermittent tower by the feed pump.

[0022] The intermittent distillation tower has 12 theoretical plates, operates at a slight negative pressure, and the top pressure is controlled at 95-100kPa. Since the raw materials contain volatile light hydrocarbon components, corresponding safety measures are also required. In intermittent distillation operations, the top temperature of the tower needs to be controlled at all times. The first to come out are non-condensable gases and light hydrocarbons. The top temperature of the tower is controlled below 50°C, and the reflux ratio is 0.5-1. After being collected by the slight negative pressure system, they are sent to the tail gas disposal device, or to the incineration system for incineration to release heat. The generated steam can be used in the distillation process.

[0023] Next, the tower top temperature is controlled within the range of 70-74°C, the reflux ratio is 0.5-1, and the crude product of methyl ethyl ketone is obtained, which can be refined to obtain a high-purity methyl ethyl ketone product after collection. Next, the tower top temperature is controlled at about 75°C, with a fluctuation of no more than 1°C, and the reflux ratio is 3, and a finished product of methyl ethyl ketone with a concentration of 99.5% can be obtained.

[0024] As the distillation proceeds, the tower bottom and tower top temperatures continue to rise, and the tower bottom temperature is controlled below 170°C. When the tower top temperature exceeds 77°C, the reflux ratio drops to 2, and all the extracted components are treated as impurities and can be sent to the incineration system to release heat. The generated steam can be used in the distillation process. During the intermittent distillation process, the heat exchange medium in the tower top condenser of the intermittent distillation tower is transported to the raw material tank as a heat source to improve the utilization rate of the heat source.

[0025] In order to inhibit the occurrence of side reactions, an inhibitor is installed in the kettle of the intermittent tower. The inhibitor is a mixture of polydimethylsiloxane and polyether silicone oil in a mass ratio of 1:1, and its content is 3-5% (mass fraction) of the total feed amount. The inhibitor of the present invention can dilute the concentration of the side reaction raw materials, greatly reduce the reaction speed of the side reaction, and hinder the side reaction process. The inhibitor is recycled in the kettle and sent to the continuous distillation tower for purification together with the crude N-formylmorpholine.

[0026] The above operation is carried out until no droplets are generated at the top of the tower, and the operation can be stopped. At this time, the tower bottom of the intermittent tower contains high-purity crude N-formylmorpholine waste liquid, which is sent to the continuous distillation tower through a high-temperature oil pump. The continuous distillation tower has 30 theoretical plates, negative pressure operation, the tower bottom pressure is controlled at 20-23kPa, and the reflux ratio is controlled at 2-3. The light component is extracted from the top of the tower and sent to the raw material tank for recycling. The tower bottom produces a distillation residue containing an inhibitor, which can be recycled and distilled or transported to the incineration system for incineration to generate heat, and the generated steam can be supplied to the distillation process. The regenerated product N-formylmorpholine is discharged from the side line on the tower plate at the bottom of the distillation tower. The discharge plate is determined according to the actual material and ranges from 25 to 29. In the continuous distillation process, the heat exchange medium after heat exchange in the reboiler of the continuous distillation tower is transported to the reboiler of the above-mentioned intermittent distillation tower as a heat source to improve the utilization rate of heat and achieve heat coupling.

[0027] After the purification of N-formylmorpholine is completed, the inhibitor can be sent to the intermittent tower for repeated use until the amount of impurities is too much and affects the efficiency of the intermittent tower. The inhibitor and the impurities can be sent to the incinerator for disposal, and the generated steam can be used for the distillation process.

[0028] If the water content of N-formylmorpholine waste liquid is high, the dehydration process can be used to reduce the water content of N-formylmorpholine waste liquid to below 6.5% to 8% to reduce the load of the intermittent distillation tower and improve the distillation efficiency. When the water content of N-formylmorpholine waste liquid in the raw material is below 2%, the process of extracting the crude product of methyl ethyl ketone can be omitted, that is, after the non-condensable gas and light hydrocarbons are extracted, the tower top temperature is directly controlled at about 75°C to extract the finished methyl ethyl ketone.

[0029] Compared with the traditional incineration process for disposing N-formylmorpholine waste liquid, the present invention realizes the resource utilization of waste liquid and improves the utilization rate of materials; at the same time, it reduces the risk of environmental pollution and reduces the emission of CO2.

[0030] The components in the waste liquid that cannot be recycled are disposed of by incineration to recover heat, and the generated steam can be used in the distillation process, thereby improving the energy utilization rate of the waste liquid.

[0031] By changing the pressure difference between continuous distillation and intermittent distillation, the cascade utilization of steam heat is achieved. Compared with ordinary distillation, the present invention has lower energy consumption and is more environmentally friendly. In order to save energy, there are already a large number of cases of processes that realize energy recovery and reuse by means of multi-effect distillation, but the cases are all concentrated on thermal coupling between continuous distillations, and there is no thermal coupling between intermittent distillation and continuous distillation. The main reason is that intermittent distillation is a non-steady-state operation, and the demand for heat will change over time, so there are no relevant industrial cases. The present invention strictly sets the operating conditions according to the characteristics of the material, and realizes the thermal coupling between intermittent and continuous distillation.

[0032] If the general distillation method is used, more impurities are easily generated. N-formylmorpholine in the waste liquid will react to generate morpholine and formic acid under certain conditions, and both of them can react with methyl ethyl ketone to generate sec-butylmorpholine. Inappropriate production technology can cause the yield of the product to decline seriously, greatly reducing economic benefits. The advantage of the present invention is that by strictly controlling the operating temperature and pressure of the distillation, the theoretical plate number of each tower, the decomposition of N-formylmorpholine is avoided, so that N-formylmorpholine and methyl ethyl ketone in the waste liquid have a higher recovery rate.

[0033] In addition to strictly controlling the distillation process, the present invention further adds an organic solvent as an inhibitor of the side reaction in the distillation tower in order to further suppress the side reaction of N-formylmorpholine, and the main component of the inhibitor is polydimethylsiloxane and a polyether silicone oil mixture. In general, in order to avoid the generation of impurities, the operation of adding other solvents is less common in the distillation operation, and the inhibitors added in the prior art are all to promote the extraction effect of the extractive distillation, and are used in a specific distillation system. The inhibitor added by the present invention can suppress the side reaction of the raw material, and the composition is different from the prior art.

[0034] Example 1

[0035] Sample 1: N-formylmorpholine waste liquid from a petrochemical enterprise in Heze, Shandong

[0036] The waste liquid contains a variety of impurity components, as shown in the following table. Some components have low content and are combined into others.

[0037] Serial number Element Content (mass percentage) 1 Moisture 5.20％ 2 Methyl Ethyl Ketone 45.72％ 3 Morpholine 7.37％ 4 N-Formylmorpholine 30.46％ 5 sec-Butylmorpholine 1.48％ 6 other 9.97％

[0038] According to the above process, the material is distilled and regenerated.

[0039] The distillation process is as follows:

[0040] The intermittent distillation tower is equipped with 12 theoretical plates, and the top pressure is controlled at 95kPa. The top temperature is controlled below 50°C, and the reflux ratio is 0.5. The non-condensable gas and light hydrocarbons are firstly discharged, which are collected by the micro-negative pressure system and sent to the tail gas disposal device.

[0041] Next, the tower top temperature is controlled within the range of 70°C, the reflux ratio is 1, and the azeotropic product of water and methyl ethyl ketone, i.e. the crude product of methyl ethyl ketone, is produced. After collection, high-purity methyl ethyl ketone products can be obtained through other refining processes. Next, the tower top temperature is controlled at about 75°C, with a fluctuation of no more than 1°C, and the reflux ratio is 3, and the finished methyl ethyl ketone with a concentration of 99.5% can be produced.

[0042] As the distillation proceeds, the tower bottom and tower top temperatures continue to rise, and the tower bottom temperature is controlled below 170°C. When the tower top temperature exceeds 77°C, the reflux ratio drops to 2, and all the extracted components are treated as impurities and can be sent to the incineration system to release heat. The generated steam can be used in the distillation process. During the intermittent distillation process, the heat exchange medium in the tower top condenser of the intermittent distillation tower is transported to the raw material tank as a heat source to improve the utilization rate of the heat source.

[0043] The above operation is carried out until no droplets are generated at the tower top, and the intermittent distillation is stopped. At this time, the tower kettle of the intermittent tower contains high-purity crude N-formylmorpholine waste liquid, which is pumped to the continuous distillation tower by a high-temperature oil pump.

[0044] The continuous distillation tower is provided with 30 theoretical plates, and is operated under negative pressure. The pressure of the tower bottom is controlled at 20 kPa, and the reflux ratio is controlled at 2. The light component is extracted from the top of the tower. Since the light component contains a small amount of N-formylmorpholine, it can be sent to the raw material tank for recycling, or it can be treated as an impurity. The distillation residue is discharged from the bottom of the tower. The content of N-formylmorpholine in the residue is very small. The residue can be transported to the incineration system for incineration to generate heat, and the generated steam can be used for the distillation process. The regenerated N-formylmorpholine is discharged from the side line of the tower plate at the bottom of the distillation tower, and the side line is discharged on 25 tower plates. In the continuous distillation process, the heat exchange medium after heat exchange in the reboiler of the continuous distillation tower is transported to the reboiler of the above-mentioned intermittent distillation tower as a heat source to achieve heat coupling.

[0045] After the purification of N-formylmorpholine is completed, the inhibitor contained in the residue can also be sent to the intermittent tower for repeated use, until the amount of impurities is too much and affects the efficiency of the intermittent tower. The inhibitor and impurities can be sent to the incinerator for disposal, and the generated steam can be used for the distillation process.

[0046] The recovery results are shown in the following table

[0047] Serial number Element Feed amount (g) Recycling amount (g) purity 1 Moisture 52 - 2 Methyl Ethyl Ketone 457.2 296 99.75％ 3 Morpholine 73.7 - 4 N-Formylmorpholine 304.6 218 99.6％ 5 sec-Butylmorpholine 14.8 - 6 other 99.7 -

[0048] Example 2

[0049] Sample 2: N-formylmorpholine waste liquid from a petrochemical enterprise in Binzhou, Shandong

[0050] The waste liquid contains a variety of impurities, as shown in the following table. Compared with sample 1, the water content is higher.

[0051]

[0052]

[0053] According to the above process, the material is distilled and regenerated.

[0054] Different from Example 1, Sample 2 has a higher water content and is first dehydrated by an adsorbent and then distilled. Before distillation, the water content has been reduced to 1.7%.

[0055] The distillation process is as follows:

[0056] The intermittent distillation tower is equipped with 12 theoretical plates, and the top pressure is controlled at 100 kPa. The top temperature is controlled below 50°C, and the reflux ratio is 1. The non-condensable gas and light hydrocarbons are firstly discharged, which are collected by the micro-negative pressure system and sent to the tail gas disposal device.

[0057] Next, the tower top temperature is controlled at about 75°C, with a fluctuation of no more than 1°C, and a reflux ratio of 3, so that finished methyl ethyl ketone with a concentration of 99.5% can be produced.

[0058] As the distillation proceeds, the tower bottom and tower top temperatures continue to rise, and the tower bottom temperature is controlled below 170°C. When the tower top temperature exceeds 77°C, the reflux ratio drops to 2, and all the extracted components are treated as impurities and can be sent to the incineration system to release heat. The generated steam can be used in the distillation process. During the intermittent distillation process, the heat exchange medium in the tower top condenser of the intermittent distillation tower is transported to the raw material tank as a heat source to improve the utilization rate of the heat source.

[0059] The above operation is carried out until no droplets are generated at the tower top, and the intermittent distillation is stopped. At this time, the tower kettle of the intermittent tower contains high-purity crude N-formylmorpholine waste liquid, which is pumped to the continuous distillation tower by a high-temperature oil pump.

[0060] 30 theoretical plates are set in the continuous distillation tower, and the tower is operated under negative pressure. The pressure of the tower bottom is controlled at 23kPa, and the reflux ratio is controlled at 3. The light component is extracted from the top of the tower. Since the light component contains a small amount of N-formylmorpholine, it can be sent to the raw material tank for recycling, or it can be treated as an impurity. The distillation residue is discharged from the bottom of the tower. The content of N-formylmorpholine in the residue is very small. The residue can be transported to the incineration system for incineration to generate heat, and the generated steam can be used for the distillation process. The regenerated N-formylmorpholine is discharged from the side line on the tower plate at the bottom of the distillation tower, and the side line is discharged on 29 tower plates. In the continuous distillation process, the heat exchange medium after heat exchange in the reboiler of the continuous distillation tower is transported to the reboiler of the above-mentioned intermittent distillation tower as a heat source to achieve heat coupling.

[0061] After the purification of N-formylmorpholine is completed, the inhibitor residue can be sent to the intermittent tower for repeated use, until the impurities are too much and affect the efficiency of the intermittent tower. The inhibitor and impurities can be sent to the incinerator for disposal, and the generated steam can be used for the distillation process.

[0062] The recovery results are shown in the following table

[0063] Serial number Element Feed amount (g) Recycling amount (g) purity 1 Moisture 129.7 - - 2 Methyl Ethyl Ketone 608.5 505 99.81％ 3 Morpholine 125.5 - - 4 N-Formylmorpholine 458.4 334 99.54％ 5 sec-Butylmorpholine 41.7 - - 6 other 138 - -

[0064] Example 3

[0065] Sample 3: N-formylmorpholine waste liquid from a petrochemical enterprise in Zibo, Shandong

[0066] The impurities contained in the waste liquid are more complex, as shown in the following table.

[0067]

[0068]

[0069] Different from the above two materials, this material contains more impurities and has a lower single yield. This process can be repeated 2-3 times to improve the yield.

[0070] The distillation process is as follows:

[0071] The intermittent distillation tower is equipped with 12 theoretical plates, and the top pressure is controlled at 90 kPa. The top temperature is controlled below 50 ° C, and the reflux ratio is 0.5. The non-condensable gas and light hydrocarbons are firstly discharged, which are collected by the micro-negative pressure system and sent to the tail gas disposal device.

[0072] Next, the tower top temperature is controlled within the range of 72°C, the reflux ratio is 0.5, and the azeotropic product of water and methyl ethyl ketone, i.e. the crude product of methyl ethyl ketone, is produced. After collection, high-purity methyl ethyl ketone products can be obtained through other refining processes such as dehydration. Next, the tower top temperature is controlled at around 75°C, with a fluctuation of no more than 1°C, and the reflux ratio is 3, and finished methyl ethyl ketone with a concentration of 99.5% can be produced.

[0073] As the distillation proceeds, the tower bottom and tower top temperatures continue to rise, and the tower bottom temperature is controlled below 170°C. When the tower top temperature exceeds 77°C, the reflux ratio drops to 2, and all the extracted components are treated as impurities and can be sent to the incineration system to release heat. The generated steam can be used in the distillation process. During the intermittent distillation process, the heat exchange medium in the tower top condenser of the intermittent distillation tower is transported to the raw material tank as a heat source to improve the utilization rate of the heat source.

[0074] The above operation is carried out until no droplets are generated at the tower top, and the intermittent distillation is stopped. At this time, the tower kettle of the intermittent tower contains high-purity crude N-formylmorpholine waste liquid, which is pumped to the continuous distillation tower by a high-temperature oil pump.

[0075] The continuous distillation tower is provided with 30 theoretical plates, and is operated under negative pressure. The pressure of the tower bottom is controlled at 23 kPa, and the reflux ratio is controlled at 3. The light component is extracted from the top of the tower. Since the light component contains a certain amount of N-formylmorpholine, it can be sent to the raw material tank for recycling. The distillation residue is discharged from the bottom of the tower. The content of N-formylmorpholine in the residue is very small. The residue can be transported to the incineration system for incineration to generate heat, and the generated steam can be used for the distillation process. The regenerated product N-formylmorpholine is discharged from the side line of the tower plate at the bottom of the distillation tower, and the side line is discharged on the 25th tower plate. In the continuous distillation process, the heat exchange medium after heat exchange in the reboiler of the continuous distillation tower is transported to the reboiler of the above-mentioned intermittent distillation tower as a heat source to achieve heat coupling.

[0076] After the purification of N-formylmorpholine is completed, the inhibitor can be sent to the intermittent tower for repeated use until the amount of impurities is too much and affects the efficiency of the intermittent tower. The inhibitor and the impurities can be sent to the incinerator for disposal, and the generated steam can be used for the distillation process.

[0077] The recovery results are shown in the following table

[0078] Serial number Element Feed amount (g) Recycling amount (g) purity 1 Moisture 63.6 - - 2 Methyl Ethyl Ketone 317 280 99.3％ 3 Morpholine 35.9 - - 4 N-Formylmorpholine 293.1 195 99.5％ 5 sec-Butylmorpholine 87.8 - - 6 other 191 - -

[0079] In addition, the components taken out as impurities when the top temperature of the intermittent distillation tower exceeds 77°C can be collected, which contain N-formylmorpholine and are not incinerated. After a certain amount is collected, it can be used as a raw material and the above distillation process can be repeated to increase the yield of the target product N-formylmorpholine.

[0080] Although the disclosure is disclosed as above, the protection scope of the disclosure is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the protection scope of this application.

Claims

1. A process for recycling and reusing N-formylmorpholine waste liquid, characterized in that: The N-formylmorpholine waste liquid is added to a batch distillation tower, and an inhibitor is added for distillation, and after the non-target components are extracted from the top of the tower, the crude N-formylmorpholine retained in the bottom of the tower is the batch distillation; The crude N-formylmorpholine from intermittent distillation is transported to a continuous distillation tower, the light component is taken out from the top of the tower, the distillation residue is taken out from the bottom of the tower, and the regenerated product N-formylmorpholine is discharged from the side line on the tower plate at the bottom of the continuous distillation tower.

2. The process for recycling and regenerating N-formylmorpholine waste liquid according to claim 1, characterized in that: The inhibitor comprises a mixture of polydimethylsiloxane and polyether silicone oil.

3. The process for recycling and regenerating N-formylmorpholine waste liquid according to claim 1 or 2, characterized in that: The dosage of the inhibitor additive accounts for 3-5% of the mass fraction of the N-formylmorpholine waste liquid.

4. The process for recycling and regenerating N-formylmorpholine waste liquid according to claim 1, characterized in that: The intermittent distillation tower has 12 theoretical plates, and the top pressure is controlled at 95-100 kPa.

5. The process for recycling and regenerating N-formylmorpholine waste liquid according to claim 1 or 4, characterized in that: First, the top temperature of the intermittent distillation tower is controlled below 50°C, the reflux ratio is 0.5-1, and the non-condensable gas and light hydrocarbon components are collected through a micro-negative pressure system; then the top temperature is controlled to 70-74°C, the reflux ratio is 0.5-1, and the crude methyl ethyl ketone is produced; then the top temperature is controlled to 75±1°C, the reflux ratio is 3, and the finished methyl ethyl ketone is produced; as the distillation proceeds, the bottom and top temperatures continue to rise, and the bottom temperature is controlled below 170°C. When the top temperature exceeds 77°C, the reflux ratio is reduced to 2, and all the produced components are treated as impurities until no droplets are produced at the top of the tower, and the intermittent distillation tower is stopped.

6. The process for recycling and reusing N-formylmorpholine waste liquid according to claim 1, characterized in that: The continuous distillation tower has 30 theoretical plates.

7. The process for recycling and regenerating N-formylmorpholine waste liquid according to claim 1 or 6, characterized in that: The bottom pressure of the continuous distillation tower is controlled at 20-23 kPa, and the reflux ratio is controlled at 2-3.

8. The process for recycling and regenerating N-formylmorpholine waste liquid according to claim 1 or 6, characterized in that: The regenerated product N-formylmorpholine is discharged from the side line on the 25th to 29th tower plates.

9. The process for recycling and reusing N-formylmorpholine waste liquid according to claim 1, characterized in that: The heat exchange medium in the reboiler of the continuous distillation tower after heat exchange is transported to the reboiler of the intermittent distillation tower as a heat source.

10. The process for recycling and reusing N-formylmorpholine waste liquid according to claim 1 or 9, characterized in that: The heat exchange medium in the top condenser of the intermittent distillation tower is transported to the raw material tank as a heat source.

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