Dmf waste liquid treatment system with vapor compressor

Abstract

The application discloses a DMF waste liquid treatment system with a vapor compressor, which comprises a rectification module, a liquid treatment module and a gas treatment module, tower top water generated by the rectification module is treated in the liquid treatment module, and a gas phase generated by the rectification module is treated in the gas treatment module, the liquid treatment module comprises a deamination unit, a stripping unit and a sewage treatment unit, the deamination unit comprises a deamination tower, the stripping unit is communicated with the top of the deamination tower, the sewage treatment unit is communicated with the bottom of the deamination tower, a gas phase generated by the stripping unit and the sewage treatment unit is introduced into the gas treatment module, the gas treatment module comprises a incinerator and a waste heat boiler, and the waste heat boiler is used for providing energy for the rectification module, the deamination unit and the stripping unit. The DMF waste liquid treatment system of the application realizes recycling of resources, further improves the energy utilization rate, and reduces the pollution to the environment.

Description

DMF waste liquid treatment system with steam compressor

[0001] This application is a divisional application of the invention patent application filed on December 2, 2024, with application number 2024117480264 and entitled "DMF waste liquid treatment system and treatment method". Technical Field

[0002] This invention belongs to the field of waste treatment technology, specifically relating to a DMF waste liquid treatment system with a steam compressor to achieve the reuse of DMF and related by-products. Background Technology

[0003] The production processes in industries such as artificial leather, automotive interiors, and textile finishing generate DMF wastewater, typically with a concentration of 15% to 30%. Directly discharging this wastewater into wastewater treatment plants results in excessively high concentrations and treatment costs. Therefore, it is necessary to separate and purify the DMF wastewater through distillation to obtain DMF with increased purity, enabling resource reuse and reducing costs and increasing efficiency for enterprises.

[0004] Currently, the mainstream process for DMF waste liquid treatment is four-tower double-effect or five-tower triple-effect, which has problems such as high energy consumption, excessive ammonia nitrogen in the wastewater pool after deamination of dimethylamine, and strong odor in the wastewater pool.

[0005] Patents such as CN201220566985.0, entitled "A DMF Distillation Recovery and Recycling System," and CN201510175184.X, entitled "A Six-Tower Four-Effect Distillation System and Recovery Method for DMAC or DMF Waste Liquid," both utilize steam heat sources and achieve multiple energy reuses through depressurization. However, their energy utilization rate is low, energy consumption is high, and byproducts in the process are not effectively recovered and utilized.

[0006] For example, the patent application number CN202310807616.9, entitled "A Process for Treating Waste Gas and Waste Liquid Residue in a DMF Recycling Device", does not show the DMF recycling and distillation process in detail, and the wastewater in the main by-products is not treated, nor is the waste gas generated during the wastewater treatment process reused.

[0007] The above background information is provided only to assist in understanding the inventive concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed before the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0008] In view of this, in order to overcome the shortcomings of the prior art, the purpose of this invention is to provide an improved DMF waste liquid treatment system that can realize the reuse of resources and energy, further improve energy utilization efficiency, and reduce energy consumption and costs.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A DMF wastewater treatment system includes a distillation module, a liquid treatment module, and a gas treatment module. The overhead water from the distillation module enters the liquid treatment module for treatment, and the gas phase from the distillation module enters the gas treatment module for treatment. The liquid treatment module includes a deamination unit, a stripping unit, and a wastewater treatment unit. The deamination unit includes a deamination tower, the stripping unit is connected to the top of the deamination tower, and the wastewater treatment unit is connected to the bottom of the deamination tower. The gas phase from the stripping unit and the wastewater treatment unit enters the gas treatment module. The wastewater from the stripping unit is mixed with the overhead water from the distillation module and then enters the deamination tower for further deamination treatment. The gas treatment module includes an incinerator and a waste heat boiler. The incinerator is used to incinerate the gas phase, and the waste heat boiler is used to collect the energy generated by incineration and provide energy to the distillation module, the deamination unit, and the stripping unit.

[0011] The distillation module includes a first dehydration unit, which includes a first dehydration tower, a steam compressor, and a first reboiler. The steam compressor is connected to the top of the first dehydration tower and the first reboiler. The steam compressor is used to compress the steam at the top of the first dehydration tower.

[0012] The distillation module includes a distillation unit and a purification unit. The distillation unit includes a distillation column, and the purification unit includes a purification column. The purification column receives a vapor-phase feed. A return pump is installed between the bottom of the purification column and the bottom of the distillation column. The return pump is used to transport the bottom material of the purification column back to the distillation column. The refluxed liquid in the purification column accumulates in the reboiler and is then pumped back to the reboiler of the distillation column for reheating using the return pump.

[0013] According to some preferred embodiments of the present invention, the first reboiler connects the bottom of the first dehydration tower and the middle position of the first dehydration tower, and the first reboiler is connected to the deamine removal tower. The first dehydration unit uses a steam compressor to recompress the steam at the top of the first dehydration tower, increasing the pressure and temperature, further enhancing its dehydration capacity, thereby reducing the amount of subsequent steam used and processing costs.

[0014] According to some preferred embodiments of the present invention, the distillation module includes a second dehydration unit, the second dehydration unit including a second dehydration tower, a first cooler and a second reboiler, the bottom of the first dehydration tower being connected to the second dehydration tower, the first cooler being disposed at the top of the second dehydration tower, the second reboiler being connected to the bottom of the second dehydration tower and the middle position of the second dehydration tower, and the second reboiler being connected to the deamine removal tower.

[0015] According to some preferred embodiments of the present invention, the distillation module includes a third dehydration unit, which includes a third dehydration tower, a third reboiler, and a fourth reboiler. The third and fourth reboilers are arranged side by side and connected between the bottom of the third dehydration tower and the middle position of the third dehydration tower. The fourth reboiler is connected to the deamine removal tower, and the second reboiler is connected to the top of the third dehydration tower. That is, the second dehydration tower is provided with energy through the top steam of the third dehydration tower and the second reboiler.

[0016] According to some preferred embodiments of the invention, the distillation unit includes a fifth reboiler connected to the bottom of the distillation column and the middle position of the distillation column, the waste heat boiler is used to provide heat to the fifth reboiler, and the fourth reboiler is connected to the top of the distillation column, that is, the energy is provided to the third dehydration column through the top steam of the distillation column and the fourth reboiler.

[0017] According to some preferred embodiments of the present invention, a heater is provided between the bottom of the third dehydration tower and the distillation tower, the heater is connected to a recovery boiler, the recovery boiler is connected to the middle position of the third dehydration tower and the bottom of the distillation tower, and the waste heat boiler is used to provide heat to the recovery boiler.

[0018] According to some preferred embodiments of the invention, the middle position of the refining column is connected to the middle position of the distillation column, and the third reboiler is connected to the top of the refining column, that is, energy is provided to the third dehydration column through the top water of the refining column and the third reboiler.

[0019] In this invention, the first dehydration tower of the distillation module is heated by a steam compressor, the heat source for the second dehydration tower is provided by the third dehydration tower, and the heat source for the third dehydration tower is provided by the distillation tower and the refining tower. This invention uses negative pressure gradient control to ensure that the temperature difference between the towers allows for steam reuse three times or more; combined with the fact that the first dehydration tower is heated by a steam compressor, the overall steam energy consumption of the equipment is more than half that of traditional equipment.

[0020] According to some preferred embodiments of the present invention, the deamination unit includes a second cooler disposed at the top of the deamination tower, a sixth reboiler disposed at the bottom of the deamination tower and at an intermediate position between the deamination tower and the tower, and the waste heat boiler is used to provide heat to the sixth reboiler.

[0021] According to some preferred embodiments of the present invention, the wastewater treatment unit includes a wastewater tank for biochemically treating the bottom material of the ammonia removal tower, and the wastewater tank is connected to the incinerator for conveying the gas phase generated during the biochemical treatment to the incinerator for incineration.

[0022] According to some preferred embodiments of the present invention, the stripping unit includes a stripping tower, a third cooler and a gas-liquid separator disposed at the top of the stripping tower, and a seventh reboiler disposed at the bottom and middle of the stripping tower. The waste heat boiler provides heat to the seventh reboiler, and the incinerator is connected to the gas-liquid separator. The bottom of the stripping tower is connected to the deamination tower. The wastewater after stripping (the stripped gas is mainly dimethylamine) has a relatively lower concentration and mixes with the overhead water from the dehydration tower and distillation tower before entering the deamination tower for further deamination and concentration.

[0023] The present invention also provides a method for treating DMF waste liquid using the DMF waste liquid treatment system described above, comprising the following steps:

[0024] The DMF waste liquid is transported to the distillation module for treatment. The gas phase generated during the treatment is transported to the incinerator for combustion. The heat generated by combustion heats the water into steam in the waste heat boiler. The heat is then transferred to the distillation module, the deaminating unit, and the stripping unit through the steam.

[0025] The overhead water generated during the distillation module process is sent to the deamination unit for deamination treatment, and the resulting liquid enters the wastewater treatment unit for biochemical treatment. The gas generated during the biochemical treatment process is sent to the incinerator, and the biochemically treated liquid is discharged in compliance with standards or used for DMF absorption and to form DMF waste liquid again.

[0026] The gas phase generated during the deamination process enters the stripping unit. After gas-liquid separation, the gas enters the incinerator, while the liquid is returned to the stripping unit.

[0027] Compared with the prior art, the advantages of the present invention are as follows: The DMF wastewater treatment system with a steam compressor of the present invention generates dimethylamine top water during the distillation process. Dimethylamine and water are separated by a stripping tower, and the wastewater enters a sewage tank. At the same time, dimethylamine gas, biogas from the sewage tank, and vacuum tail gas from the distillation enter an incinerator for combustion. The high-temperature flue gas generates a certain amount of steam through a waste heat boiler, which is returned to the front end to provide energy for related components, realizing the recycling of resources, further improving energy utilization efficiency, and reducing environmental pollution. Through the cooperation of the deammoniation unit, sewage treatment unit, and stripping unit, the extraction of dimethylamine is more complete, the energy density of combustion is higher, and the energy recovery is more complete. Moreover, the sewage treatment cost is lower, the effluent quality is better, and it can be directly reused or discharged. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 is a schematic diagram of the DMF waste liquid treatment system in an embodiment of the present invention;

[0030] Figure 2 is a schematic flowchart of the DMF waste liquid treatment method in an embodiment of the present invention;

[0031] In the attached drawings, the reference numerals are as follows: First dehydration tower - 1, Steam compressor - 2, First reboiler - 3, First transfer pump - 4, First discharge pump - 5, Second dehydration tower - 6, First cooler - 7, Second reboiler - 8, Second transfer pump - 9, Third transfer pump - 10, Second discharge pump - 11, Third dehydration tower - 12, Third reboiler - 13, Fourth transfer pump - 14, Fourth reboiler - 15, Fifth transfer pump - 16, Third discharge pump - 17, Heater -18, Distillation Column -19, Fifth Reboiler -20, Return Pump -21, Refining Column -22, Recovery Boiler -23, Deaminating Column -24, Fourth Discharge Pump -25, Sixth Reboiler -26, Sixth Transfer Pump -27, Stripping Column -28, Fifth Discharge Pump -29, Seventh Reboiler -30, Third Cooler -31, Gas-Liquid Separator -32, Reflux Pump -33, Incinerator -34, Waste Heat Boiler -35, Wastewater Tank -36, Second Cooler -37. Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0033] Example 1: DMF Waste Liquid Treatment System

[0034] As shown in Figures 1 and 2, the DMF waste liquid treatment system of this embodiment includes a distillation module, a liquid treatment module, and a gas treatment module. The overhead water produced by the distillation module enters the liquid treatment module for treatment, and the gas phase (vacuum tail gas) produced by the distillation module enters the gas treatment module for treatment. The arrows in the figures represent the direction of the substances.

[0035] The following details the composition and structure of each module:

[0036] (1) Distillation module

[0037] The distillation module in this embodiment sequentially includes a first dehydration unit, a second dehydration unit, a third dehydration unit, a distillation unit, and a purification unit, which respectively include a first dehydration tower 1, a second dehydration tower 6, a third dehydration tower 12, a distillation tower 19, and a purification tower 22. After treatment by the distillation unit, the DMF waste liquid is concentrated to over 99.5%. The purification unit further concentrates the DMF based on the distillation unit, and includes two functions: 1. Further removal of water, with water being discharged from the top of the tower as a light component. 2. Reduction of acid value, with formic acid complex salts accumulating at the bottom of the tower and being transported back to the distillation tower via a return pump, and then transported to the recovery boiler.

[0038] Specifically, the first dehydration unit includes a first dehydration tower 1, a steam compressor 2, and a first reboiler 3. The steam compressor 2 connects the top of the first dehydration tower 1 and the first reboiler 3. The first reboiler 3 connects the bottom of the first dehydration tower 1 and the middle position of the first dehydration tower 1. The first reboiler 3 is connected to the top of the first dehydration tower 1 and the deamine removal tower 24 via a first delivery pump 4. The bottom of the first dehydration tower 1 is connected to the first reboiler 3 and the second dehydration tower 6 via a first discharge pump 5. The first discharge pump 5 acts as a circulation pump for the first reboiler 3. During operation, the flow rate of the first discharge pump 5 is used to circulate the first reboiler 3. Only when the liquid level of the second dehydration tower 6 is lower than the set value, a small portion of the flow rate of the first discharge pump 5 (e.g., 3%-10%) is delivered to the second dehydration tower 6 as a supplement.

[0039] The second dehydration unit includes a second dehydration tower 6, a first cooler 7, and a second reboiler 8. The first cooler 7 is located at the top of the second dehydration tower 6 and is connected to the side of the top of the second dehydration tower 6 and the deamine removal tower 24 via a second transfer pump 9. The second reboiler 8 is connected to the bottom of the second dehydration tower 6 and the middle position of the second dehydration tower 6, and is also connected to the deamine removal tower 24. Energy is supplied to the second dehydration tower 6 through the top steam of the third dehydration tower 12 and the second reboiler 8. The second reboiler 8 is connected to the top of the third dehydration tower 12 and the deamine removal tower 24 via a third transfer pump 10. The bottom of the second dehydration tower 6 is connected to the third dehydration tower 12 via a second discharge pump 11.

[0040] The third dehydration unit includes a third dehydration tower 12, a third reboiler 13, and a fourth reboiler 15. The third and fourth reboilers 13 and 15 are arranged side-by-side and connected between the bottom and middle of the third dehydration tower 12. The third and fourth reboilers 13 and 15 are connected to the tops of the purification tower 22 and distillation tower 19, respectively. This means that the overhead steam from the purification tower 22, the overhead steam from the third and distillation towers 19, and the fourth reboiler 15 together provide energy to the third dehydration tower 12. The third reboiler 13 is connected to the tops of the distillation tower 19 and the purification tower 22 via a fourth transfer pump 14. The fourth reboiler 15 is connected to the tops of the deamine removal tower 24 and the distillation tower 19 via a fifth transfer pump 16. The proportion of material from the bottom of the third dehydration tower 12 entering the third reboiler 13 and the fourth reboiler 15 is allocated according to the corresponding steam flow rates at the top of the purification tower 22 and the distillation tower 19, in order to maximize energy utilization.

[0041] The distillation unit includes a distillation column 19 and a fifth reboiler 20. The fifth reboiler 20 connects the bottom of the distillation column 19 and the middle position of the distillation column 19. A heater 18 is provided between the bottom of the third dehydration column 12 and the distillation column 19. The heater 18 is connected to a recovery boiler 23. The recovery boiler 23 connects the middle position of the third dehydration column 12 and the bottom of the distillation column 19. The waste heat boiler 35 is used to provide heat to the fifth reboiler 20 and the recovery boiler 23.

[0042] Preferably, the third dehydration tower 12 is connected to the distillation tower 19 via the third discharge pump 17, and the heater 18 is installed on the pipeline where the third discharge pump 17 is located. The third reboiler 13 and the fourth reboiler 15 are also connected to the connecting pipeline.

[0043] The refining unit includes a refining column 22, which is connected to a distillation column 19. A return pump 21 is installed between the bottoms of the refining column 22 and the distillation column 19. The DMF product is discharged from the middle position of the refining column 22. The refining column 22 is fed by the vapor phase from the distillation column 19. The heat of the refining column 22 is provided by the distillation unit. The refining column 22 has no additional heat source, and there is no temperature difference between the refining unit and the distillation unit. Therefore, the refining unit cannot reheat the distillation unit. Thus, the third dehydration column 12 is equipped with a third reboiler 13 corresponding to the top of the refining column 22 and a fourth reboiler 15 corresponding to the top of the distillation column 19, so as to fully collect and utilize the heat from the refining column 22 and the distillation column 19.

[0044] In this embodiment, the first dehydration unit uses a steam compressor 2 to recompress the top steam of the first dehydration tower 1, increasing its pressure and temperature to further enhance its dehydration capacity and reduce subsequent steam usage and processing costs. The heat source for the second dehydration tower 6 is provided by the top steam of the third dehydration tower 12, which in turn is provided by the distillation tower 19 and the refining tower 22. This embodiment employs negative pressure gradient control to ensure that the temperature difference between the towers allows for steam reuse three times or more. Combined with the fact that the first dehydration tower 1 is heated by the steam compressor 2, the overall steam energy consumption of the equipment is more than half that of traditional equipment.

[0045] (2) Liquid handling module

[0046] The liquid treatment module includes a deamine unit, a stripping unit, and a wastewater treatment unit.

[0047] The deamination unit includes a deamination tower 24, a second cooler 37 located at the top of the deamination tower 24, and a sixth reboiler 26 located at the bottom of the deamination tower 24 and in the middle of the deamination tower 24. The stripping unit is connected to the top of the deamination tower 24, and the wastewater treatment unit is connected to the bottom of the deamination tower 24 through a fourth discharge pump 25. The gas phase generated by the stripping unit and the wastewater treatment unit enters the gas treatment module for processing.

[0048] The stripping unit includes a stripping tower 28, a third cooler 31 and a gas-liquid separator 32 located at the top of the stripping tower 28, and a seventh reboiler 30 located between the bottom and middle of the stripping tower 28. An incinerator 34 is connected to the gas-liquid separator 32. The bottom of the stripping tower 28 is connected to the top of the deamine removal tower 24 via a fifth discharge pump 29. A reflux pump 33 is installed between the gas-liquid separator 32 and the stripping tower 28 to return the separated liquid to the stripping tower 28.

[0049] The wastewater treatment unit includes a wastewater tank 36, which is used to biochemically treat the bottom material of the deamine tower 24. The wastewater tank 36 is connected to the incinerator 34 to transport the gas phase generated during the biochemical treatment to the incinerator 34 for incineration.

[0050] (3) Gas processing module

[0051] The gas processing module includes an incinerator 34 and a waste heat boiler 35. The waste heat boiler 35 is used to collect the energy generated by incineration and provide energy to the distillation module, the deamination unit, and the stripping unit. In this embodiment, the waste heat boiler 35 is used to heat the fifth reboiler 20, the sixth reboiler 26, the seventh reboiler 30, and the recovery boiler 23.

[0052] The following is a brief description of the working process of the DMF waste liquid treatment system in this embodiment:

[0053] DMF waste liquid with a concentration of 15-30% enters the first dehydration tower 1. Heat is supplied through the first reboiler 3, which evaporates the lower-boiling-point water in the bottom of the first dehydration tower 1, causing it to rise to the top. The vapor phase (top steam) enters the steam compressor 2, converting electrical energy into the internal energy of the steam (increasing temperature and pressure), raising the saturated steam temperature at the top of the tower by 10-25°C. The steam then re-enters the first reboiler 3 to provide heat to the liquid waste liquid in the bottom of the tower for evaporation. Simultaneously, the cooled top steam condenses into liquid water (top water). A portion of this water is returned to the first dehydration tower 1 via the first transfer pump 4, while the remainder enters the deamine removal tower 24. The flow rate returning to the first dehydration tower 1 or entering the deamine removal tower 24 is adjusted according to the concentration of the top water. Generally, the COD in the top water is required to be less than 1000 ppm. If the COD is higher than this value, the flow rate returning to the top of the first dehydration tower 1 is increased to reduce the concentration; if the COD is lower than this value, the flow rate returning to the top of the first dehydration tower 1 is decreased to save energy.

[0054] After concentration, the waste liquid at the bottom of the first dehydration tower 1 is increased to 40-45%, and then enters the second dehydration tower 6 through the first discharge pump 5. The second reboiler 8 heats and evaporates the waste liquid at the bottom of the second dehydration tower 6. The first cooler 7 is installed at the top of the second dehydration tower 6 to condense the vapor at the top of the tower into liquid phase, and part of it is returned to the second dehydration tower 6, while part of it enters the deamine removal tower 24.

[0055] The concentration of the bottom liquid in the second dehydration tower 6 after concentration is 50-55%, and it is transported to the third dehydration tower 12 by the second tower discharge pump. The third dehydration tower 12 is equipped with two reboilers, a third reboiler 13 and a fourth reboiler 15. The waste liquid at the bottom of the third dehydration tower 12 is heated and evaporated by the two reboilers. The steam at the top of the tower provides heat to the second reboiler 8 while being condensed into liquid (top water) itself. Part of the steam is returned to the third dehydration tower 12 by the third transfer pump 10, and part of it enters the deamine removal tower 24.

[0056] The concentration of the bottom liquid after concentration in the third dehydration tower 12 is 75-85%. It is then transported to the heater 18 by the third discharge pump 17. Steam is used to evaporate all the liquid into gas. Some solids and high-boiling-point impurities enter the recovery boiler 23 to further evaporate DMF and enter the third dehydration tower 12. The remaining distillation residue, impurities and high-boiling-point substances are disposed of by an external contractor.

[0057] The vapor phase heated by heater 18 enters distillation column 19. The vapor phase at the top of distillation column 19 enters the fourth reboiler 15 for condensation, and part of it is refluxed back to distillation column 19, while part enters the deamine removal column 24. DMF is enriched at the bottom of distillation column 19 with a concentration of 98% or higher, and then further removed by evaporation in the fifth reboiler 20.

[0058] High-purity DMF gas enters the refining column 22 from the middle side stream of distillation column 19. The light components rise from the top of refining column 22 to the third reboiler 13, where they condense from the gas phase into the liquid phase. Most of the liquid is refluxed, while a small portion of the liquid with high water content is refluxed back to the bottom of distillation column 19. The finished DMF product is discharged from the side stream of refining column 22 as a liquid phase, with a concentration that can reach 99.5% or higher.

[0059] The main components of the overhead water produced by the above-mentioned device are a mixture of water, DMF and dimethylamine. This liquid enters the deamination tower 24 and is heated by the sixth reboiler 26. Low-boiling substances and dimethylamine waste gas are condensed from the top of the tower into a high-concentration liquid by the second cooler 37, and then enter the dimethylamine stripping tower 28 for stripping.

[0060] The bottom of stripping tower 28 is heated to approximately 95°C in the seventh reboiler 30, allowing dimethylamine to fully vaporize and enter the third cooler 31 for cooling. The cooled liquid and non-condensable gases are separated by a gas-liquid separator 32. The liquid is then pumped back into stripping tower 28 via a reflux pump 33 for further evaporation, while the high-concentration dimethylamine gas is incinerated in the waste gas incinerator 34. The low-concentration bottom liquid after stripping is mixed with water from the distillation module via the fifth discharge pump 29 and enters the deamination tower 24 for further deamination. The deamination bottom liquid is then pumped into the wastewater tank 36 via the fourth discharge pump 25 for biochemical treatment. During this process, biogas and other gases are generated and sent to the incinerator 34. The heat from combustion of the waste gas heats the waste heat boiler 35 to generate high-temperature steam, which then provides heat to the distillation module. The gas treated by the incinerator 34 meets emission standards and is directly discharged.

[0061] Example 2: DMF Waste Liquid Treatment Method

[0062] As shown in Figures 1 and 2, based on the DMF waste liquid treatment system in Example 1, this embodiment provides a DMF waste liquid treatment method, including the following steps:

[0063] Step 1: Distillation Process

[0064] (1) First dehydration

[0065] DMF waste liquid enters the first dehydration tower 1 for the first dehydration. The steam at the top of the tower passes through the steam compressor 2 and enters the first reboiler 3. The material in the first dehydration tower 1 is heated by the first discharge pump 5. The heated material re-enters the first dehydration tower 1. The steam at the top of the tower is condensed by the first reboiler 3 to form top water. Part of the water is sent to the deamine removal tower 24 by the first transfer pump 4, and part of it is returned to the first dehydration tower 1.

[0066] The concentrated material at the bottom of the first dehydration tower 1 is transported to the second dehydration tower 6 by the first discharge pump 5 for a second dehydration.

[0067] (2) Second dehydration

[0068] The steam at the top of the second dehydration tower 6 is cooled by the first cooler 7. The resulting water at the top of the tower is partially transported to the deamine removal tower 24 by the second transfer pump 9, and partially returned to the second dehydration tower 6.

[0069] The overhead steam from the top of the third dehydration tower 12 enters the second reboiler 8, which heats the material from the bottom of the second dehydration tower 6 that enters the second reboiler 8 via the second discharge pump 11. The heated material then re-enters the second dehydration tower 6. The overhead steam is condensed in the second reboiler 8 to form overhead water, which is partially transported to the deamine removal tower 24 by the third transfer pump 10, and partially returned to the third dehydration tower 12.

[0070] The concentrated material at the bottom of the second dehydration tower 6 is transported to the third dehydration tower 12 by the second discharge pump 11 for a third dehydration.

[0071] (3) Third dehydration

[0072] The overhead steam from the top of the refining column 22 enters the third reboiler 13, heating the material from the bottom of the third dehydration column 12 that enters the third reboiler 13 via the third discharge pump 17. The overhead steam from the top of the distillation column 19 enters the fourth reboiler 15, heating the material from the bottom of the third dehydration column 12 that enters the fourth reboiler 15 via the third discharge pump 17. The heated material re-enters the third dehydration column 12. The overhead steam from the distillation column 19 is condensed in the fourth reboiler 15 to form overhead water, which is partially transported to the deamine removal column 24 by the fifth transfer pump 16, and partially returned to the distillation column 19. The overhead steam from the refining column 22 is condensed in the third reboiler 13, and partially transported to the distillation column 19 by the fourth transfer pump 14, and partially returned to the refining column 22.

[0073] The bottom material of the concentrated third dehydration tower 12 is transported to the heater 18 via the third discharge pump 17, heated to steam, and then sent to the distillation tower 19 for distillation. The heated solids and high-boiling-point impurities enter the recovery boiler 23 for further DMF evaporation, which then enters the third dehydration tower 12. The remaining distillation residue, impurities, and high-boiling-point waste in the recovery boiler 23 are disposed of externally. The energy of the recovery boiler 23 is provided by the high-temperature steam generated by heating water in the waste heat boiler 35.

[0074] (4) Distillation

[0075] The bottom material of distillation column 19 can also be reheated in recovery boiler 23. High-temperature steam generated by heating water in waste heat boiler 35 of gas processing module enters fifth reboiler 20 to heat the material entering from the bottom of distillation column 19; the heated material then re-enters distillation column 19. Moisture is removed by evaporation in fifth reboiler 20, resulting in DMF enrichment at the bottom of distillation column 19 at a concentration of 98% or higher.

[0076] (5) Refined

[0077] The material in distillation column 19 enters refining column 22 from the middle of the column body for refining, and then condenses and exits from the middle of refining column 22. The light components in refining column 22 rise from the top of refining column 22 to the third reboiler 13 and condense from the gas phase to the liquid phase. Most of the liquid is returned to refining column 22 through the fourth transfer pump 14, and a small portion of the liquid with high water content is returned to distillation column 19.

[0078] A return pump 21 is installed between the bottom of the refining column 22 and the bottom of the distillation column 19. The bottom material of the refining column 22 is re-entered into the distillation column 19 for distillation through the return pump 21.

[0079] During the distillation process, the exhaust gas from the top of the dehydration tower, distillation tower 19, and refining tower 22 is directly fed into the incinerator 34 for combustion.

[0080] Step 2: Liquid Processing

[0081] The overhead water (a mixture of water, DMF, and dimethylamine) generated during the distillation process is sent to the deamination unit for deamination treatment. Details are as follows:

[0082] (1) Deamination

[0083] The top vapor of the deaminating tower 24 is cooled into a high-concentration liquid by the second cooler 37 and then partially transported to the stripping tower 28 by the sixth transfer pump 27, while the other part is returned to the deaminating tower 24.

[0084] The high-temperature steam generated by heating water by the waste heat boiler 35 of the gas processing module enters the sixth reboiler 26 to heat the material entering the sixth reboiler 26 from the bottom of the deamine tower 24; the heated material re-enters the deamine tower 24.

[0085] (2) Steam stripping

[0086] The steam at the top of the stripping tower 28 enters the third cooler 31. The cooled liquid and non-condensable gas enter the gas-liquid separator 32. After gas-liquid separation in the gas-liquid separator 32, the high-concentration dimethylamine gas enters the incinerator 34 for incineration, and the liquid is returned to the stripping tower 28 for evaporation via the reflux pump 33.

[0087] The high-temperature steam generated by the waste heat boiler 35 of the gas processing module heats the water and enters the seventh reboiler 30 to heat the material that is conveyed to the seventh reboiler 30 from the bottom of the stripping tower 28. The heated material then re-enters the stripping tower 28.

[0088] The bottom material of stripping tower 28 is mixed with the top water of the distillation module via the fifth discharge pump 29 and then enters the deaminating tower 24 for further deamination.

[0089] (3) Biochemical treatment

[0090] The low-concentration bottom material from the stripping deaminizer tower 24 is transported to the wastewater treatment unit for biochemical treatment via the fourth discharge pump 25. The wastewater treatment unit includes a wastewater tank 36. The gas generated during the biochemical treatment process is transported to the incinerator 34. The biochemically treated liquid is discharged in compliance with standards or used for DMF absorption to form DMF waste liquid again, thus forming a recycling system.

[0091] Step 3: Gas Processing

[0092] The gas consists of three main parts: the vacuum tail gas at the top of the distillation module, the gas from the top steam of the stripping tower 28 after cooling and gas-liquid separation, and the gas generated during the biochemical treatment process. These three parts of the gas enter the incinerator 34 for incineration, and the gas after incineration meets the emission standards. The energy from the incineration process is used to heat water through the waste heat boiler 35 to generate high-temperature steam. This high-temperature steam is returned to the front end to heat relevant components. In this embodiment, it is used to heat the fifth reboiler 20, the sixth reboiler 26, the seventh reboiler 30, and the recovery boiler 23.

[0093] For ease of description and understanding, the above steps are numbered and described separately, but this does not imply any limitation. In practice, at least some of the above steps can be performed simultaneously or in any order.

[0094] The concentration of DMF waste liquid generated during the production process is generally 15% to 30%. Directly discharging it into the wastewater pond results in too high a concentration and excessive treatment costs. In this invention, the DMF aqueous solution enters the distillation module, where it is purified to obtain DMF with a purity of over 99.5%, which can be reused in production, achieving resource reusability and reducing costs and increasing efficiency for enterprises. During the distillation process, a small amount of DMF hydrolyzes, producing dimethylamine top water. This water is separated from the dimethylamine and water by a deamination tower and a stripping tower, and the wastewater enters the wastewater pond. The dimethylamine gas enters the incinerator and is burned together with the biogas from the wastewater pond and the vacuum tail gas from the distillation. The high-temperature flue gas passes through a waste heat boiler to generate a certain amount of steam, which is returned to the front end to heat the distillation module. Furthermore, the first dehydration tower in this invention uses steam recompression technology, which can save more than 50% in overall energy consumption. Through the DMF waste liquid treatment system of this invention, the separation and utilization efficiency of substances is effectively improved.

[0095] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A DMF waste liquid treatment system with a steam compressor, characterized in that, The system includes a distillation module, a liquid processing module, and a gas processing module. The overhead water produced by the distillation module enters the liquid processing module for processing, and the gas phase produced by the distillation module enters the gas processing module for processing. The distillation module sequentially includes a first dehydration unit, a second dehydration unit, a third dehydration unit, a distillation unit, and a purification unit, which respectively include a first dehydration tower, a second dehydration tower, a third dehydration tower, a distillation tower, and a purification tower. The first dehydration unit includes a first dehydration tower, a steam compressor, and a first reboiler. The steam compressor is connected to the top of the first dehydration tower and the first reboiler. The steam compressor is used to recompress the overhead steam of the first dehydration tower to increase the steam pressure and temperature. The heat source for the second dehydration tower is... The third dehydration tower is supplied with overhead steam, and its heat source is provided by a distillation tower and a purification tower. The liquid treatment module includes a deamination unit, a stripping unit, and a wastewater treatment unit. The deamination unit includes a deamination tower; the stripping unit is connected to the top of the deamination tower, and the wastewater treatment unit is connected to the bottom of the deamination tower. The gas phase generated by the stripping unit and the wastewater treatment unit enters the gas treatment module. The wastewater from the stripping unit is mixed with the overhead water generated by the distillation module and then enters the deamination tower for further deamination treatment. The gas treatment module includes an incinerator and a waste heat boiler. The incinerator is used to incinerate the gas phase, and the waste heat boiler is used to collect the energy generated by incineration and to treat the distillation module, the deamination unit, and the wastewater treatment unit. The stripping unit provides energy; the first reboiler connects the bottom of the first dehydration tower and the middle position of the first dehydration tower, and the first reboiler is connected to the top of the first dehydration tower and the deamine removal tower via a first transfer pump; the second dehydration unit includes a second dehydration tower, a first cooler, and a second reboiler, and the bottom of the first dehydration tower is connected to the first reboiler and the second dehydration tower via a first discharge pump; the first discharge pump is the circulation pump of the first reboiler; when the liquid level of the second dehydration tower is lower than a set value, 3%-10% of the flow rate in the first discharge pump is delivered to the second dehydration tower as a supplement; the third dehydration unit includes a third dehydration tower, a third reboiler, and a fourth reboiler, and the third and fourth reboilers are respectively connected to the top of the refining tower, the first reboiler, the second reboiler, and the third reboiler. The top of the distillation column is connected; the third and fourth reboilers are arranged side by side and connected between the bottom of the third dehydration column and the middle position of the third dehydration column; the fourth reboiler is connected to the deamine removal column; the second reboiler is connected to the top of the third dehydration column; the bottom of the second dehydration column is connected to the third dehydration column; the purification column is fed by the vapor phase of the distillation column, and the heat of the purification column is provided by the distillation unit; the purification column is connected to the distillation column; a return pump is provided between the bottom of the purification column and the bottom of the distillation column, and the return pump is used to transport the bottom material of the purification column to the distillation column; the first cooler is located at the top of the second dehydration column and is connected to the side of the top of the second dehydration column and the deamine removal column through a second transfer pump;The second reboiler is connected to the bottom of the second dehydration tower and the middle position of the second dehydration tower. The second reboiler is connected to the top of the third dehydration tower and the deamination tower via a third transfer pump. The third reboiler is connected to the top of the distillation tower and the purification tower via a fourth transfer pump. The fourth reboiler is connected to the top of the deamination tower and the distillation tower via a fifth transfer pump. The proportion of material from the bottom of the third dehydration tower entering the third and fourth reboilers is distributed according to the corresponding steam flow rates at the top of the purification and distillation towers.

2. The DMF waste liquid treatment system according to claim 1, characterized in that, The distillation unit includes a fifth reboiler, which connects the bottom of the distillation column to the middle position of the distillation column, and the waste heat boiler is used to provide heat to the fifth reboiler.

3. The DMF waste liquid treatment system according to claim 2, characterized in that, A heater is installed between the bottom of the third dehydration tower and the distillation tower. The heater is connected to a recovery boiler, which is connected to the middle of the third dehydration tower and the bottom of the distillation tower. The waste heat boiler is used to provide heat to the recovery boiler. The third dehydration tower is connected to the distillation tower through a third discharge pump. The heater is installed on the pipeline where the third discharge pump is located. The third reboiler and the fourth reboiler are also connected to the connecting pipeline.

4. The DMF waste liquid treatment system according to claim 1, characterized in that, The deamination unit includes a second cooler located at the top of the deamination tower and a sixth reboiler located at the bottom of the deamination tower and in the middle of the deamination tower. The waste heat boiler is used to provide heat to the sixth reboiler.

5. The DMF waste liquid treatment system according to claim 1, characterized in that, The wastewater treatment unit includes a wastewater tank. The wastewater treatment unit is connected to the bottom of the deaminating tower via a fourth discharge pump for biochemical treatment of the bottom material of the deaminating tower. The wastewater tank is connected to the incinerator for transporting the gas phase generated during the biochemical treatment process to the incinerator for incineration.

6. The DMF waste liquid treatment system according to claim 1, characterized in that, The stripping unit includes a stripping tower, a third cooler and a gas-liquid separator located at the top of the stripping tower, and a seventh reboiler located at the bottom and middle of the stripping tower. The waste heat boiler is used to provide heat to the seventh reboiler. The incinerator is connected to the gas-liquid separator. The bottom of the stripping tower is connected to the deamine removal tower.

7. The DMF waste liquid treatment system according to claim 6, characterized in that, A reflux pump is installed between the gas-liquid separator and the stripping tower to return the liquid after gas-liquid separation to the stripping tower.

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