CN117736108A - DMF waste liquid recovery treatment process - Google Patents

Abstract

The invention discloses a DMF waste liquid recovery treatment process which comprises the steps of (1) filtering, preheating, (2) primary decompression concentration and dehydration, (3) secondary decompression concentration and dehydration, (4) decompression rectification and (5) decompression deacidification: the DMF concentrated solution steam enters a deacidification tower, is cooled by a condenser, flows back from the deacidification tower and is beaten to the top of the deacidification tower by a flowmeter, wherein one part of the DMF concentrated solution steam flows back into the top of the deacidification tower, and the other part of DMF concentrated solution steam is taken as a DMF finished product; according to the invention, the two-stage reduced pressure concentration dehydration is adopted and is matched with the rectifying tower and the deacidification tower to carry out reduced pressure heat pump rectification, the operating pressure of the two-stage reduced pressure concentration kettle tower, the rectifying tower and the deacidification tower can be lower, the DMF decomposition rate is reduced, the heat source is recycled, the energy-saving effect is achieved, the heat recovery is realized, the rectification energy consumption is reduced, the energy-saving effect is achieved, compared with the traditional process, the energy-saving effect is obvious, the purity of DMF is further improved, and the DMF recovery quality is improved.

Description

A kind of DMF waste liquid recovery and treatment process

Technical field

The present invention relates to the field of equipment, specifically to a DMF waste liquid recovery and treatment process.

Background technique

As the international pace of the market accelerates, my country's synthetic leather output has maintained sustained and steady growth, and synthetic leather clothing fabrics have been widely used in society. As the market's requirements for the quality and variety of synthetic leather increase, the demand for personalization and functionality is increasing, and so is the demand. Dimethylformamide (DMF) is a widely used organic solvent. It is widely used in synthetic leather, synthetic fiber, pesticides, medicine and other industries. DMF is a transparent liquid that can mix with water and most organic solvents. Mutually soluble, it is a common solvent for chemical reactions. DMF is stable in nature, and the B/C value of DMF-containing wastewater is small and difficult to biodegrade. DMF's high toxicity will have an inhibitory effect on the biological treatment process in sewage. DMF wastewater has a high salt content and is difficult to treat. It is often used in the production of synthetic leather. A large amount of DMF-containing wastewater is generated during its use. Therefore, it is of great significance to treat this type of wastewater and recover DMF.

When recycling DMF waste liquid, the DMF waste liquid contains particulate impurities. These particulate impurities can easily cause clogging and scaling inside the recovery tower, affecting the recovery of DMF waste liquid. At the same time, when condensing the DMF gas produced by distillation, a small amount of Doping with other substances, how to avoid the cumbersomeness of the existing technology and provide a simple and efficient method for recycling DMF is a key technical issue that needs to be faced in the current process of recycling DMF waste liquid in synthetic leather production.

Contents of the invention

The purpose of the present invention is to propose a DMF waste liquid recovery and treatment process to solve the problems raised in the above background technology.

In order to achieve the above objects, the present invention is achieved by the following technical means:

A DMF waste liquid recovery and treatment process includes the following steps:

(1) Filtration and preheating: Use a feed pump to send the DMF waste liquid in the storage tank into the filter, filter out the impurities and then send it into the preheater, preheat it to 40°C, and collect the filtered impurities regularly and outsource the treatment; ;

(2) One-stage vacuum concentration and dehydration: The preheated DMF waste liquid is measured by a flow meter and sent to the first-stage vacuum concentration kettle tower, and the liquid level is determined by the liquid level regulator of the first-stage vacuum concentration kettle tower. position, the gas phase discharged from the top of the first-level vacuum concentration kettle is condensed by the top condenser and then enters the top water tank. The water in the top water tank flows into the first-level vacuum concentration kettle tower, and the concentrated liquid after the first-level concentration is sent to the water tank. Enter the secondary vacuum concentration reactor tower;

(3) Two-level vacuum concentration and dehydration: The concentrated liquid after the first-level concentration is sent to the second-level vacuum concentration kettle tower, and the DMF concentrated liquid after the second dehydration and concentration is sent to the evaporation separator of the rectification tower for separation, and the weight The lighter concentrated liquid vapor enters the distillation tower, and the heavier concentrated liquid components return to the evaporator for cyclic evaporation. The final residual liquid of the evaporator is sent to the residual liquid evaporator to continue evaporation, and the steam generated by the residual liquid evaporator is sent to the first stage. The bottom reboiler of the vacuum concentration tower is dehydrated, reboiled, and evaporated again. The residue at the bottom of the residual liquid tank needs to be manually opened and the ball valve at the bottom is regularly discharged and outsourced for processing;

(4) Vacuum distillation: The concentrated liquid vapor from the evaporator enters from the middle of the distillation tower. The reboiler at the bottom of the distillation tower ensures that the concentrated liquid is circulated and concentrated. After the gas phase at the top of the tower is condensed, part of it is recycled back to the distillation tower. Part of it is sent to the tank area, and the DMF concentrated liquid steam is extracted from the middle of the distillation tower at 150°C and sent to the deacidification tower for deacidification;

(5) Deacidification under reduced pressure: DMF concentrated liquid vapor enters the deacidification tower, and the DMF gas rises to the top of the deacidification tower. After being cooled by the condenser in the upper part of the deacidification tower, it is refluxed from the deacidification tower through a flow meter until it is deacidified. At the top of the tower, part of it flows back to the top of the deacidification tower, and the other part is extracted as DMF finished product.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention adopts two-stage vacuum concentration and dehydration and cooperates with a rectification tower and a deacidification tower to perform vacuum heat pump rectification. The two-stage vacuum concentration kettle tower, rectification tower and deacidification tower of the present invention can operate at a lower pressure and reduce The decomposition rate of DMF is reduced, and the heat source is recycled to achieve energy saving. The rising vapor phase at the top of the two-stage vacuum concentration kettle tower, distillation tower, and deacidification tower is compressed by a steam compressor and used as a heat source to realize heat recovery and reduce the energy consumption. The energy consumption of distillation can achieve the effect of energy saving. Compared with the traditional process, the energy saving effect is obvious, which further improves the purity of DMF and improves the quality of DMF recovery. The distillation tower adopts vapor phase feed to avoid clogging of debris in the waste liquid. The rectification tower and the deacidification tower make the operation of the system using the process of the present invention more stable.

Picture description:

Figure 1 is a schematic diagram of the DMF waste liquid recovery and treatment process flow diagram according to the embodiment of the present invention.

Detailed ways:

The embodiments of the technical solution of the present application will be described in detail below with reference to the accompanying drawings. The following examples and drawings are only used to illustrate the technical solution of the present application more clearly, and are therefore only used as examples and cannot be used to limit the scope of protection of the present application. The drawings only schematically show the parts related to the technical solution of the present application, and they do not represent the actual structure of the product.

Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the technical field belonging to this application; the terms used herein are for the purpose of describing specific embodiments only and are not intended to be used in Limitation of this application; the terms "including" and "having" and any variations thereof in the description and claims of this application and the above description of the drawings are intended to cover non-exclusive inclusion.

Reference herein to "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The appearances of this phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those skilled in the art understand, both explicitly and implicitly, that the embodiments described herein may be combined with other embodiments.

In this embodiment, a DMF waste liquid recovery and treatment process includes the following steps:

(1) Filtration and preheating: Use a feed pump to send the DMF waste liquid in the storage tank into the filter, filter out the impurities and then send it into the preheater, preheat it to 40°C, and collect the filtered impurities regularly and outsource the treatment;

(2) One-stage vacuum concentration and dehydration: The preheated DMF waste liquid is measured by a flow meter and sent to the first-stage vacuum concentration kettle tower, and the liquid level is determined by the liquid level regulator of the first-stage vacuum concentration kettle tower. position, the gas phase discharged from the top of the first-level vacuum concentration kettle is condensed by the top condenser and then enters the top water tank. The water in the top water tank flows into the first-level vacuum concentration kettle tower, and the concentrated liquid after the first-level concentration is sent to the water tank. Enter the secondary vacuum concentration reactor tower;

(3) Two-level vacuum concentration and dehydration: The concentrated liquid after the first-level concentration is sent to the second-level vacuum concentration kettle tower, and the DMF concentrated liquid after the second dehydration and concentration is sent to the evaporation separator of the rectification tower for separation, and the weight The lighter concentrated liquid vapor enters the distillation tower, and the heavier concentrated liquid components return to the evaporator for cyclic evaporation. The final residual liquid of the evaporator is sent to the residual liquid evaporator to continue evaporation, and the steam generated by the residual liquid evaporator is sent to the first stage. The bottom reboiler of the vacuum concentration tower is dehydrated, reboiled, and evaporated again. The residue at the bottom of the residual liquid tank needs to be manually opened and the ball valve at the bottom is regularly discharged and outsourced for processing;

(4) Vacuum distillation: The concentrated liquid vapor from the evaporator enters from the middle of the distillation tower. The reboiler at the bottom of the distillation tower ensures that the concentrated liquid is circulated and concentrated. After the gas phase at the top of the tower is condensed, part of it is recycled back to the distillation tower. Part of it is sent to the tank area, and the DMF concentrated liquid steam is extracted from the middle of the distillation tower at 150°C and sent to the deacidification tower for deacidification;

(5) Deacidification under reduced pressure: DMF concentrated liquid vapor enters the deacidification tower, and the DMF gas rises to the top of the deacidification tower. After being cooled by the condenser in the upper part of the deacidification tower, it is refluxed from the deacidification tower through a flow meter until it is deacidified. At the top of the tower, part of it flows back to the top of the deacidification tower, and the other part is extracted as DMF finished product.

It also includes tail gas treatment steps: the non-condensable gas generated by the first-stage vacuum concentration kettle tower, the second-stage vacuum concentration kettle tower, and the rectification tower is extracted by the vacuum pump to the steam-water separation tank, and is connected to the tail gas condenser through a pipeline. Re-cooling: the condensate returns to the gas-water separation tank, and is pumped to the water tank on the top of the tower by the vacuum circulating water pump; the gas phase is absorbed by the tail gas absorption tower through three cycles and four sprays, and the absorbed liquid is quantified by the circulation pump to the water tank on the top of the tower; tail gas absorption The trace amount of tail gas at the top of the tower is absorbed again by the two-stage activated carbon absorption device and then discharged;

It also includes steam waste heat utilization steps: the steam water from the residual liquid evaporation tank, feed heater, and distillation tower reboiler enters the hot water tank, the low-pressure steam flashes to the waste heat heater of the second tower, and the hot water is reheated with the waste heat of the first tower. heater, which is then cooled by a normal temperature water condenser and then replenished into the circulating pool;

It also includes a recovery and cooling step: the circulating water is pumped from the circulating water pump through the pipeline to the tower top condenser, DMF condenser, pure DMF cooler, tail gas condenser, returns to the cooling tower after heat exchange, and is split to the cooling tower through the cooling tower distributor. The tower packing layer is air-cooled by a cooling fan.

In step (1), the weight percentage of the DMF waste liquid is DMF 20%-30%. The preheater is preheated by material heat exchange. The heat source is DMF steam from the deacidification tower, which is distributed through the power plant. The saturated steam pressure is 1.0 -1.8MPa, temperature 220℃.

The preheated DMF waste liquid in step (2) was measured at 24m ³ /h by the flow meter. The temperature inside the first-stage vacuum concentration kettle was 40-50°C, and the pressure of the first-stage kettle was -0.088MPa. The heat source of the bottom reboiler of the vacuum concentration kettle tower is the top steam of the second-stage vacuum concentration kettle tower. The gas phase discharged from the top of the first-stage vacuum concentration kettle tower is mainly dimethylamine and water vapor. The steps described (2) The DMF content of the concentrated solution is 35%.

In the step (3), the heat source of the bottom reboiler of the secondary concentration tower is the top steam of the distillation tower. The temperature inside the secondary concentration tower is 60-90°C, and the pressure of the tower kettle is about -0.068MPa. Others The same as the primary concentration kettle, the DMF content of the DMF concentrate after secondary dehydration and concentration is 50%.

In the step (4), the pressure inside the condensation tower is -0.010MPa, the temperature in the tower kettle is 160°C, the temperature in the tower is 110~120°C, and the temperature at the top of the tower is 90~100°C.

Specifically, in the step (5), part of the DMF is refluxed from the middle of the deacidification tower through the packing to the bottom of the tower for 2.4 m ³ /h, and part of the DMF is extracted from the finished product 6 to 8 m ³ /h; The pressure in the acid tower is reduced to -0.08MPa. The deacidification tower does not have a heating system. Through pressure reduction, the DMF concentrate is vaporized. The temperature at the bottom of the tower is 100-108°C, and the temperature at the top is 95~110°C. The deacidification tower uses The purity of the finished DMF product is over 99.6%. The accompanying drawings of the description of the present invention disclose the recovery of 25% DMF waste liquid. After the recovery process, the purity of the final DMF product extracted from the deacidification tower is 99.8%.

The specific embodiments disclosed in the present invention fall within the scope of protection of the claims of the present invention and are the specific implementation scope of the characteristic parts of the present invention. The protection content of the specific embodiments is only an explanation of the scope of protection of the claims of the present invention. The scope is not limited to the protection content of the specific embodiments, and the protection content of the specific embodiments should not be understood as limiting the scope of protection of the claims of the present invention.

Certain exemplary embodiments of the present invention have been described above only by way of illustration. It goes without saying that those of ordinary skill in the art can modify the described embodiments in various different ways without departing from the scope of the present invention. Examples are modified. Therefore, the above description is illustrative in nature and should not be construed as limiting the scope of the claims of the present invention.

Unless otherwise defined, all academic and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

In the event of conflict, the definitions in this specification shall prevail.

Unless otherwise stated, all percentages, parts, ratios, etc. are by weight.

When a numerical value or range of values, a preferred range, or a series of lower preferred values and upper preferred values is given, it should be understood that it specifically discloses any lower range limit or preferred value and any larger range limit or preferred value. Any range formed by any pair of values, whether or not the ranges are separately disclosed. Unless otherwise stated, where this specification describes a numerical range, the stated range is intended to include the range endpoints and all integers and fractions within the range.

When the terms "about" or "around" are used to describe a value or an endpoint of a range, the disclosure is intended to include that specific value or endpoint in question.

The terms "a" and "an" are used to describe elements of the invention for convenience only and to give a general picture of the invention. Unless expressly stated otherwise, the description should be understood to include one or at least one species.

Claims (9)

1. A DMF waste liquid recovery treatment process is characterized in that: the method comprises the following steps:

(1) Filtering and preheating: sending DMF waste liquid of the storage tank into a filter by a feed pump, filtering out impurities, sending the filtered DMF waste liquid into a preheater, preheating to 40 ℃, periodically collecting the filtered impurities, and then, delegating external treatment;

(2) First-stage decompression concentration dehydration: the preheated DMF waste liquid is fed into a first-stage reduced pressure concentration kettle tower after being metered by a flowmeter, the liquid level is determined by a liquid level regulator self-contained in the first-stage reduced pressure concentration kettle tower, gas phase discharged from the top of the first-stage reduced pressure concentration kettle is condensed by a tower top condenser and then enters a tower top water tank, water in the tower top water tank flows into the first-stage reduced pressure concentration kettle tower, and concentrated solution after first-stage concentration is fed into a second-stage reduced pressure concentration kettle tower;

(3) Second-stage decompression concentration dehydration: sending the concentrated solution after primary concentration into a secondary decompression concentration kettle tower, sending the DMF concentrated solution after secondary dehydration concentration into a rectifying tower evaporation separator for separation, sending the concentrated solution steam with lighter weight into the rectifying tower, returning the heavier concentrated solution component to an evaporator for circular evaporation, sending the final residual liquid of the evaporator to a residual liquid evaporator for continuous evaporation, sending the steam generated by the residual liquid evaporator into a tower bottom reboiler of the primary decompression concentration tower for re-dehydration, reboiling and evaporation, and periodically discharging the residue at the bottom of the residual liquid tank by manually opening a bottom ball valve for external treatment;

(4) And (3) vacuum rectification: the concentrated solution steam from the evaporator enters from the middle part of the rectifying tower, a reboiler at the bottom of the rectifying tower ensures the concentrated solution to be concentrated circularly, a part of the condensed gas phase at the top of the rectifying tower is recycled to the rectifying tower, and the other part of the condensed gas phase is sent to a tank area, and DMF concentrated solution steam extracted from the middle part of the rectifying tower is sent to a deacidification tower for deacidification at 150 ℃;

(5) Decompression deacidification: and (3) enabling the DMF concentrated solution steam to enter a deacidification tower, enabling DMF gas to rise to the top of the deacidification tower, cooling the upper part of the deacidification tower through a condenser, enabling the DMF concentrated solution steam to flow back into the top of the deacidification tower through a flowmeter, and taking the other part of DMF concentrated solution steam as a DMF finished product.

2. The DMF waste liquid recovery treatment process according to claim 1, wherein: in the step (1), the weight percentage of DMF in the DMF waste liquid is 20% -30%, the preheating of the preheater adopts material heat exchange, the heat source is DMF steam of the deacidification tower, the saturated steam pressure is 1.0-1.8MPa, and the temperature is 220 ℃.

3. The DMF waste liquid recovery treatment process according to claim 1, wherein: the DMF waste liquid preheated in the step (2) is metered by a flowmeter for 24m ³ And (3) h, the temperature in the first-stage reduced pressure concentration kettle tower is 40-50 ℃, the pressure in the kettle is-0.088 MPa, the heat source of the reboiler at the bottom of the first-stage reduced pressure concentration kettle tower is the top steam of the second-stage reduced pressure concentration kettle tower, the gas phase discharged from the top of the first-stage reduced pressure concentration kettle tower is mainly dimethylamine and water vapor, and the DMF content of the concentrated solution in the step (2) is 35%.

4. The DMF waste liquid recovery treatment process according to claim 1, wherein: the heat source of the reboiler at the bottom of the secondary concentration tower in the step (3) is the top steam of the rectifying tower, the temperature in the secondary concentration kettle is 60-90 ℃, the pressure in the kettle is about-0.068 MPa, and the DMF content of the DMF concentrated solution after secondary dehydration concentration is 50% in other steps which are the same as those of the primary concentration kettle.

5. The DMF waste liquid recovery treatment process according to claim 1, wherein: the pressure in the rectifying tower in the step (4) is-0.010 MPa, the temperature of the tower bottom is 160 ℃, the temperature in the tower is 110-120 ℃, and the temperature of the tower top is 90-100 ℃.

6. The DMF waste liquid recovery treatment process according to claim 1, wherein: in the step (5), a part of DMF flows back to the bottom direction of the tower from the middle part of the deacidification tower through the filler for 2.4m ³ And/h, partially extracting the finished product of 6-8 m ³ /h; the pressure in the deacidification tower in the step (5) is reduced to-0.08 MPa, the deacidification tower is not provided with a heating system, the DMF concentrated solution is vaporized by reducing the pressure, the tower bottom temperature is 100-108 ℃, and the tower top temperature is 95-110 ℃.

7. The DMF waste liquid recovery treatment process according to claim 1, wherein: the method also comprises the following steps of: non-condensable gas generated by the first-stage reduced pressure concentration kettle tower, the second-stage reduced pressure concentration kettle tower and the rectifying tower is pumped to a steam-water separation tank by a vacuum pump, is connected to a tail gas condenser by a pipeline, and is cooled again by normal-temperature water: condensate returns to the gas-water separation tank and is pumped to the water tank at the top of the tower by a vacuum circulating water pump; the gas phase is absorbed by a tail gas absorption tower through three-circulation four-spray, and the absorption liquid is quantified to a tower top water tank by a circulating pump; the trace tail gas at the top of the tail gas absorption tower is absorbed again by the two-stage active carbon absorption device and then discharged.

8. The DMF waste liquid recovery treatment process according to claim 1, wherein: the method also comprises the following steps of utilizing the steam waste heat: the residual liquid evaporating pot, the feeding heater and the rectifying tower reboiler are connected with the steam water in the hot water pot, the low-pressure steam is flashed to the two-tower waste heat heater, the hot water is heated to the one-tower waste heat heater again, and the cooled water is fed into the circulating water pool after being cooled by the normal-temperature water condenser.

9. The DMF waste liquid recovery treatment process according to claim 1, wherein: the method also comprises the steps of recycling and cooling: circulating water is pumped to the tower top condenser, the DMF condenser, the pure DMF cooler, the tail gas condenser and the cooling tower through a pipeline by a circulating water pump, flows back to the cooling tower after heat exchange, is shunted to the cooling tower filler layer through a cooling tower distributor, and is cooled by a cooling fan.