Alkaline DMF waste liquid recovery method with high recovery rate
Through neutralization pretreatment, dehydration treatment and deacid treatment, the problems of high energy consumption and low yield in the recycling process of alkaline DMF waste liquid are solved, and efficient and energy-saving DMF waste liquid recycling and purification are achieved.
Patent Information
- Application Number
- CN202411970282.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-30
- Publication Date
- 2025-03-28
AI Technical Summary
The prior art has high energy consumption and low yields in the recycling process of alkaline DMF waste liquid, and traditional distillation technology may lead to DMF decomposition or by-product generation, reducing product quality.
The pH value is adjusted through inorganic acid neutralization reaction by using neutralization pretreatment, dehydration treatment and deacidification treatment, and then dehydration treatment is carried out in the three-effect distillation tower, and deacidification treatment is achieved by indirect steam heating, and pure DMF is finally collected.
It improves the recovery rate and purity of DMF waste liquid, reduces energy consumption and equipment corrosion risks, and achieves the purpose of energy conservation and carbon reduction.
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Abstract
Description
Technical Field
[0001] The present application relates to the technical field of DMF waste liquid recovery, and in particular to a method for recovering alkaline DMF waste liquid with a high recovery rate. Background Art
[0002] With the rapid development of the chemical industry, DMF, as a commonly used organic solvent, is a common problem in the chemical industry, especially in the production of pharmaceuticals and dyes. With the increasing awareness of environmental protection in society, the state continues to introduce more stringent regulations to limit the emission of harmful substances, making the reasonable disposal of DMF waste liquid more important.
[0003] The waste liquid of dimethylformamide (DMF) in the pharmaceutical industry contains alkaline substances such as piperidine, which makes the DMF product present a certain alkalinity. At the same time, in the DMF recovery production process, the dimethylamine released by the thermal decomposition of DMF also makes the DMF product present a certain alkalinity. Although traditional distillation technology can achieve the recovery of part of the solvent, due to the high boiling point of DMF itself (153°C), long-term heating under high temperature conditions may also cause DMF to decompose or produce by-products, thereby reducing product quality. Summary of the invention
[0004] In order to improve the defects of high energy consumption and low yield in the existing alkaline DMF waste liquid recovery process, the present application provides a high recovery rate alkaline DMF waste liquid recovery method.
[0005] A high-recovery alkaline DMF waste liquid recovery method comprises the following steps: Neutralization pretreatment: taking the alkaline DMF waste liquid to be treated and preliminarily filtering it, collecting the filtrate and adding inorganic acid, neutralizing the reaction and adjusting the system temperature to complete the neutralization pretreatment step; Dehydration treatment: placing the pre-treated liquid after neutralization pre-treatment in a dehydration tower for dehydration treatment; Deacidification treatment: The pretreatment liquid after dehydration treatment is placed in a deacidification tower, left to stand for deacidification and the recovered DMF is collected at the top of the tower.
[0006] Through the above technical scheme, the present application recovers and purifies DMF waste liquid through three main steps: neutralization pretreatment, dehydration treatment and deacidification treatment. The first neutralization pretreatment of the present application is to react the alkaline substances in the waste liquid with inorganic acids to adjust the pH value so that the harmful substances in the waste liquid are neutralized, and at the same time, large particle impurities are removed by preliminary filtration. Secondly, the dehydration treatment of the present application is to further reduce the water content in the waste liquid, which is usually achieved by methods such as distillation. Finally, the present application further processes the dehydrated liquid through deacidification treatment to remove residual acidic substances, and finally collects pure DMF. The overall scheme is simple to operate and reduces the energy consumption required for traditional distillation, improves the overall operating efficiency, and achieves the purpose of energy saving and carbon reduction.
[0007] Furthermore, the inorganic acid comprises 90-98% by mass of sulfuric acid.
[0008] Through the above technical solution, the present application refines the type and purity of the inorganic acid used in the neutralization pretreatment. Using 90-98% by mass sulfuric acid as a neutralizing agent can effectively react with the alkaline substances in the waste liquid, and its high purity ensures the high efficiency of the reaction and the purity of the recovered DMF.
[0009] Furthermore, the neutralization reaction temperature is 35-45°C.
[0010] Through the above technical scheme, the present application limits the temperature range of the neutralization reaction, and sets the neutralization reaction within the temperature range of 35-45°C. Since the boiling point of DMF is as high as 153°C at normal pressure, it is easy to cause high-temperature decomposition of DMF when the wastewater contains acid or alkali. By optimizing the reaction temperature, the thermal decomposition loss of DMF can be reduced, thereby further improving the recovery efficiency of DMF.
[0011] Furthermore, the dehydration treatment adopts a triple-effect distillation tower dehydration treatment, and the triple-effect distillation tower includes a first dehydration tower, a second dehydration tower and a third dehydration tower connected in series.
[0012] Furthermore, the operating pressures in the triple-effect distillation tower are: 8-12 kPa in the first dehydration tower, 20-25 kPa in the second dehydration tower, and 45-50 kPa in the third dehydration tower.
[0013] Through the above technical scheme, the present application adopts a triple-effect distillation tower dehydration treatment through multiple distillations and evaporations to effectively remove water from the liquid, thereby improving the purity and yield of DMF. At the same time, the present application optimizes the operating pressure in the triple-effect distillation tower. The first dehydration tower adopts a lower operating pressure (8-12kPa) to achieve preliminary dehydration and energy saving. The operating pressure of the second dehydration tower (20-25kPa) further improves the dehydration efficiency and ensures the stable operation of the equipment. The third dehydration tower adopts a higher operating pressure (45-50kPa) to achieve the final dehydration treatment and ensure that the moisture content in the waste liquid reaches an extremely low level. By reasonably setting the operating pressure of each tower, the entire dehydration process can be optimized, the purity and yield of DMF can be improved, and energy consumption and equipment corrosion risks can be reduced.
[0014] Furthermore, the third dehydration tower is indirectly heated by boiler steam, the steam at the top of the third dehydration tower heats the second dehydration tower through a reboiler, and the steam at the top of the second dehydration tower heats the first dehydration tower through a reboiler.
[0015] Through the above technical scheme, the present application uses boiler steam to indirectly heat each tower in the triple-effect distillation tower. This method improves the dehydration efficiency and the energy efficiency of the entire treatment process by realizing the recycling of steam in the tower. Specifically, the steam at the top of the third dehydration tower heats the second dehydration tower through a reboiler, causing the liquid in the second dehydration tower to boil and evaporate. The steam at the top of the second dehydration tower then heats the first dehydration tower through a reboiler, causing the liquid in the first dehydration tower to further boil and evaporate. In this way, through the recycling of steam, efficient heat transfer and improved dehydration efficiency are achieved. By reasonably setting the operating pressure and temperature of each tower, it can be ensured that no damage to the equipment or undesirable by-products will be caused during the steam heating process.
[0016] Furthermore, the reflux ratio of the first dehydration tower is 0.5-0.8.
[0017] Furthermore, a preheating treatment is provided in the steps and before the pretreatment, and the preheating temperature is 45-50°C.
[0018] In summary, the present application includes at least one of the following beneficial technical effects: 1. The present application recovers and purifies DMF waste liquid through three main steps: neutralization pretreatment, dehydration treatment, and deacidification treatment. The neutralization pretreatment of the present application is to react the alkaline substances in the waste liquid with inorganic acids to adjust the pH value so that the harmful substances in the waste liquid are neutralized, and large particle impurities are removed by preliminary filtration. Secondly, the dehydration treatment of the present application is to further reduce the water content in the waste liquid, usually by distillation and other methods. Finally, the deacidification treatment of the present application is to further process the dehydrated liquid to remove residual acidic substances, and finally collect pure DMF. The overall solution is simple to operate and reduces the energy consumption required for traditional distillation, improves the overall operating efficiency and achieves the purpose of energy saving and carbon reduction; 2. The present application limits the temperature range of the neutralization reaction, and sets the neutralization reaction within the temperature range of 35-45°C. Since the boiling point of DMF is as high as 153°C at normal pressure, it is easy to cause high-temperature decomposition of DMF when the wastewater contains acid or alkali. By optimizing the reaction temperature, the thermal decomposition loss of DMF can be reduced, thereby further improving the recovery efficiency of DMF; 3. The present application adopts a triple-effect distillation tower dehydration treatment through multiple distillations and evaporations to effectively remove water from the liquid, thereby improving the purity and yield of DMF. At the same time, the present application optimizes the operating pressure in the triple-effect distillation tower. The first dehydration tower adopts a lower operating pressure (8-12kPa) to achieve initial dehydration and energy saving. The operating pressure of the second dehydration tower (20-25kPa) further improves the dehydration efficiency and ensures the stable operation of the equipment. The third dehydration tower adopts a higher operating pressure (45-50kPa) to achieve the final dehydration treatment and ensure that the moisture content in the waste liquid reaches an extremely low level. By reasonably setting the operating pressure of each tower, the entire dehydration process can be optimized, the purity and yield of DMF can be improved, and energy consumption and equipment corrosion risks can be reduced; 4. The present application utilizes boiler steam to indirectly heat each tower in a triple-effect distillation tower. This method improves the dehydration efficiency and the energy efficiency of the entire treatment process by realizing the recycling of steam in the tower. Specifically, the steam at the top of the third dehydration tower heats the second dehydration tower through a reboiler, causing the liquid in the second dehydration tower to boil and evaporate. The steam at the top of the second dehydration tower then heats the first dehydration tower through a reboiler, causing the liquid in the first dehydration tower to further boil and evaporate. In this way, through the recycling of steam, efficient heat transfer and improved dehydration efficiency are achieved. By reasonably setting the operating pressure and temperature of each tower, it can be ensured that no damage to the equipment or undesirable by-products will be caused during the steam heating process. DETAILED DESCRIPTION
[0019] The present application is further described in detail below with reference to the embodiments.
[0020] In the examples of the present application, the raw materials and instruments used are as follows, but not limited thereto. Raw materials not otherwise specified are of analytical grade.
[0021] Example 1 A high-recovery alkaline DMF waste liquid recovery method comprises the following steps: Neutralization pretreatment: 1150 kg of alkaline DMF waste liquid to be treated (DMF content 99.55%, pH 12.01, alkalinity 1.2906%, water content 0.93%) was taken and preliminarily filtered, the filtrate was collected and added with 29.6 kg of 90% sulfuric acid by mass, and mixed by rapid stirring at 100 r / min for 120 min. During the reaction, the system temperature was maintained at 35 ° C to complete the neutralization pretreatment step; Dehydration treatment: the pre-treated liquid after the neutralization pre-treatment is placed in a three-effect distillation tower for dehydration treatment, and the operating pressure is adjusted to: 8 kPa for the first dehydration tower, 205 kPa for the second dehydration tower, and 45 kPa for the third dehydration tower; Deacidification treatment: The pretreatment liquid after dehydration treatment is placed in a deacidification tower, which is indirectly heated by steam. The condensate at the top of the deacidification tower is recovered to collect the treated DMF.
[0022] Example 2 A high-recovery alkaline DMF waste liquid recovery method comprises the following steps: Neutralization pretreatment: take 10010kg of alkaline DMF waste liquid to be treated (DMF content 99.55%, pH 12.01, alkalinity 1.2906%, water content 0.93%) and filter it preliminarily, collect the filtrate and add 270kg of 95% sulfuric acid by mass, stir rapidly at 100r / min for 120min, keep the system temperature at 40°C during the reaction, and complete the neutralization pretreatment step; Dehydration treatment: the pre-treated liquid after the neutralization pre-treatment is placed in a three-effect distillation tower for dehydration treatment, and the operating pressure is adjusted to: 10 kPa for the first dehydration tower, 22 kPa for the second dehydration tower, and 47 kPa for the third dehydration tower; Deacidification treatment: The pretreatment liquid after dehydration treatment is placed in a deacidification tower, which is indirectly heated by steam. The condensate at the top of the deacidification tower is recovered to collect the treated DMF.
[0023] Example 3 A high-recovery alkaline DMF waste liquid recovery method comprises the following steps: Neutralization pretreatment: 7200 kg of alkaline DMF waste liquid to be treated (DMF content 99.55%, pH 12.01, alkalinity 1.2906%, water content 0.93%) was taken and preliminarily filtered, the filtrate was collected and added with 200 kg of 98% sulfuric acid by mass, and mixed by rapid stirring at 100 r / min for 120 min. During the reaction, the system temperature was maintained at 45°C to complete the neutralization pretreatment step; Dehydration treatment: the pre-treated liquid after the neutralization pre-treatment is placed in a three-effect distillation tower for dehydration treatment, and the operating pressure is adjusted to: 12 kPa for the first dehydration tower, 25 kPa for the second dehydration tower, and 50 kPa for the third dehydration tower; Deacidification treatment: The pretreatment liquid after dehydration treatment is placed in a deacidification tower, which is indirectly heated by steam. The condensate at the top of the deacidification tower is recovered to collect the treated DMF.
[0024] Example 4 A high-recovery alkaline DMF waste liquid recovery method comprises the following steps: Neutralization pretreatment: 1150 kg of alkaline DMF waste liquid to be treated (DMF content 99.55%, pH 12.01, alkalinity 1.2906%, water content 0.93%) was taken and preliminarily filtered, the filtrate was collected and added with 32.1 kg of 95% sulfuric acid by mass, and mixed by rapid stirring at 100 r / min for 120 min. During the reaction, the system temperature was kept at 40°C to complete the neutralization pretreatment step; Dehydration treatment: the pre-treated liquid after the neutralization pre-treatment is placed in a three-effect distillation tower for dehydration treatment, and the operating pressure is adjusted to: 10 kPa for the first dehydration tower, 22 kPa for the second dehydration tower, and 47 kPa for the third dehydration tower; Deacidification treatment: The pretreatment liquid after dehydration treatment is placed in a deacidification tower, which is indirectly heated by steam. The condensate at the top of the deacidification tower is recovered to collect the treated DMF.
[0025] Example 5 A high-recovery alkaline DMF waste liquid recovery method comprises the following steps: Neutralization pretreatment: 5700 kg of alkaline DMF waste liquid to be treated (DMF content 99.55%, pH 12.01, alkalinity 1.2906%, water content 0.93%) was taken and preliminarily filtered, the filtrate was collected and added with 155 kg of 95% sulfuric acid by mass, and mixed by rapid stirring at 100 r / min for 120 min. During the reaction, the system temperature was kept at 40°C to complete the neutralization pretreatment step; Dehydration treatment: the pre-treated liquid after the neutralization pre-treatment is placed in a three-effect distillation tower for dehydration treatment, and the operating pressure is adjusted to: 10 kPa for the first dehydration tower, 22 kPa for the second dehydration tower, and 47 kPa for the third dehydration tower; Deacidification treatment: The pretreatment liquid after dehydration treatment is placed in a deacidification tower, which is indirectly heated by steam. The condensate at the top of the deacidification tower is recovered to collect the treated DMF.
[0026] Performance Testing The DMF treated by the method of Example 1-6 was tested, and the test results are shown in the following table: Table 1 Performance test table
[0027] From the above examples 1-5, combined with the test results in Table 1, it can be found that: The present application recycles and purifies DMF waste liquid through three main steps: neutralization pretreatment, dehydration treatment and deacidification treatment. The first neutralization pretreatment of the present application is to react the alkaline substances in the waste liquid with inorganic acids to adjust the pH value so that the harmful substances in the waste liquid are neutralized, and at the same time, large particle impurities are removed by preliminary filtration. Secondly, the dehydration treatment of the present application is to further reduce the water content in the waste liquid, which is usually achieved by methods such as distillation. Finally, the present application further processes the dehydrated liquid through deacidification treatment to remove residual acidic substances, and finally collects pure DMF. The overall solution is simple to operate and reduces the energy consumption required for traditional distillation, improves the overall operating efficiency and achieves the purpose of energy saving and carbon reduction.
[0028] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.
[0029] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.
[0030] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.
[0031] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.
Claims
1. A high recovery rate alkaline DMF waste liquid recovery method, characterized in that, The following steps are involved: Neutralization pretreatment: taking the alkaline DMF waste liquid to be treated and preliminarily filtering it, collecting the filtrate and adding inorganic acid, neutralizing the reaction and adjusting the system temperature to complete the neutralization pretreatment step; Dehydration treatment: placing the pre-treated liquid after neutralization pre-treatment in a dehydration tower for dehydration treatment; Deacidification treatment: The pretreatment liquid after dehydration treatment is placed in a deacidification tower, left to stand for deacidification and the recovered DMF is collected at the top of the tower.
2. A high recovery alkaline DMF waste liquid recovery method according to claim 1, characterized in that, The inorganic acid comprises 90-98% by mass of sulfuric acid.
3. A high recovery alkaline DMF waste liquid recovery method according to claim 1, characterized in that, The neutralization reaction temperature is 35-45°C.
4. A high recovery alkaline DMF waste liquid recovery method according to claim 1, characterized in that, The dehydration treatment adopts a three-effect distillation tower dehydration treatment, and the three-effect distillation tower comprises a first dehydration tower, a second dehydration tower and a third dehydration tower which are connected in series.
5. A high recovery alkaline DMF waste liquid recovery method according to claim 4, characterized in that, The operating pressures in the triple-effect distillation tower are: 8-12 kPa for the first dehydration tower, 20-25 kPa for the second dehydration tower, and 45-50 kPa for the third dehydration tower.
6. A high recovery alkaline DMF waste liquid recovery method according to claim 4, characterized in that, The third dehydration tower is indirectly heated by boiler steam. The steam at the top of the third dehydration tower heats the second dehydration tower through a reboiler, and the steam at the top of the second dehydration tower heats the first dehydration tower through a reboiler.
7. A high recovery alkaline DMF waste liquid recovery method according to claim 4, characterized in that, The reflux ratio of the first dehydration tower is 0.5-0.
8.
8. A high recovery alkaline DMF waste liquid recovery method according to claim 1, characterized in that, In the step and before the pretreatment, a preheating treatment is also provided, and the preheating temperature is 45-50°C.