Evaporation and concentration device for polyamide 6 extraction water

Abstract

The utility model relates to the technical field of nylon production, and particularly provides a polyamide 6 extraction water evaporation and concentration device, which is characterized in that the tube pass of a first-effect heat exchanger, the tube pass of a second-effect heat exchanger and the tube pass of a third-effect heat exchanger are respectively provided with a circulation loop, after circulating heat exchange and concentration, the steam enters a tube pass of a second-effect heat exchanger, enters a third-effect heat exchanger after further circulating heat exchange and concentration, and enters a fourth-effect heat exchanger and a third separator after circulating heat exchange, steam generated by a tube pass of a first-effect heat exchanger enters a first separator to be separated, and a gas phase enters a shell pass of the second-effect heat exchanger; steam generated by tube passes of the second-effect heat exchanger and the third-effect heat exchanger enters a second separator to be separated, a separated gas phase and a gas phase separated by a third separator are connected to a spray washing tower and a compressor together, and compressed steam provides steam for a shell pass of the first-effect heat exchanger and a shell pass of the third-effect heat exchanger. The device is reasonable in structural arrangement, heat energy can be fully utilized, and energy is saved.

Description

Technical Field

[0001] This utility model belongs to the field of nylon production technology and relates to a polyamide 6 extraction water evaporation and concentration device. Background Technology

[0002] Polyamide 6, an aliphatic polyamide, is widely used in various fields such as fibers, engineering plastics, and films due to its lightweight, high strength, wear resistance, and stability in weak acids, weak alkalis, and certain organic solvents.

[0003] In the process of preparing polyamide-6 using caprolactam as a monomer, the condensation reaction of caprolactam forms various polymer molecules, including highly condensed polymers, low-condensation dimers, and oligomers. Although these low-molecular-weight compounds are in chemical equilibrium, they typically account for 8% to 13% of the total material. To improve product quality, water extraction is usually required to remove these oligomers and unreacted ε-caprolactam.

[0004] CN208465213U discloses a polyamide 6 extraction water evaporation system, which achieves precise control of a triple-effect evaporator by setting multiple control valves in the evaporation system. However, this is a traditional triple-effect evaporation system with relatively high steam consumption. Summary of the Invention

[0005] This invention provides a polyamide 6 extraction water evaporation and concentration device, which, through the adjustment of the equipment structure, allows for co-current feeding and recovers and compresses the secondary steam from the final evaporation for reuse, thereby saving energy.

[0006] The technical solution of this utility model is to provide a polyamide 6 extraction water evaporation and concentration device, including a first-effect heat exchanger, a first separator, a second-effect heat exchanger, a third-effect heat exchanger, a second separator, a fourth-effect heat exchanger, and a third separator. The tubes of the first-effect, second-effect, and third-effect heat exchangers are each equipped with a circulation loop. The extraction water to be concentrated enters from the tubes of the first-effect heat exchanger, undergoes circulation heat exchange and concentration, then enters the tubes of the second-effect heat exchanger, undergoes further circulation heat exchange and concentration, then enters the third-effect heat exchanger, and finally undergoes another circulation heat exchange before entering the fourth-effect heat exchanger. The heat exchanger and the third separator are as follows: the steam generated in the tube side of the first-effect heat exchanger enters the first separator for separation, and the gas phase enters the shell side of the second-effect heat exchanger; the steam generated in the tube side of the second-effect and third-effect heat exchangers enters the second separator for separation, and the separated gas phase, together with the gas phase separated in the third separator, is connected to the spray scrubbing tower and the compressor. The compressed steam provides steam for the shell side of the first-effect and third-effect heat exchangers, and the steam in the fourth-effect heat exchanger is external steam; the liquid phase outlet of the third separator is also connected to the concentrate storage tank by a pipeline.

[0007] Furthermore, the first-effect heat exchanger, the second-effect heat exchanger, and the third-effect heat exchanger are all falling film heat exchangers.

[0008] Furthermore, the steam condensate from the shell side of the first-effect heat exchanger, the second-effect heat exchanger, and the third-effect heat exchanger is connected to a condensate storage tank, and the outlet of the condensate storage tank is connected to a preheating heat exchanger for preheating the extraction water before it enters the tube side of the first-effect heat exchanger.

[0009] Furthermore, the extraction water to be concentrated enters from the top of the tube side of the first-effect heat exchanger, and the bottom outlet is connected to the second-effect heat exchanger via a pipe, entering from the bottom of its tube side.

[0010] Furthermore, the compressors are multiple sets.

[0011] Furthermore, the lower part of the spray scrubbing tower is a spray pipe, and the upper part is a packing layer. The gas phase is led out into the compressor after passing through the packing layer.

[0012] Furthermore, a concentrate transfer tank and a filter are also provided between the four-effect heat exchanger and the concentrate storage tank.

[0013] This utility model has the following beneficial effects:

[0014] The device provided by this utility model utilizes the steam generated at the last effect of a multi-effect evaporator. After washing to remove impurities, the steam is compressed, resulting in a significant increase in the temperature, pressure, and enthalpy of the secondary steam. This allows the secondary steam to re-enter the first-effect heat exchanger for heating and evaporating the extracted water, releasing its latent heat. The secondary steam generated by the boiling and vaporization of the extracted water then sequentially enters the next-effect heat exchanger as a heat source. The final secondary steam is compressed, and the cycle repeats continuously. This eliminates the need for a secondary steam cooling water system, saving a significant amount of cooling water. It also fully recovers and utilizes the heat energy of the secondary steam, saving live steam and achieving energy conservation.

[0015] After the four-effect heat exchange and separation of this invention, the concentration of the obtained concentrate is about 80%. After filtration and collection, it can be further concentrated in subsequent processes to reduce the content of cyclic dimers in the concentrate and prepare a concentrate of about 90%. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of this utility model. Detailed Implementation

[0017] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0018] like Figure 1As shown, this utility model provides a polyamide 6 extraction water evaporation and concentration device, including a first-effect heat exchanger 1, a first separator 2, a second-effect heat exchanger 3, a third-effect heat exchanger 4, a second separator 5, a fourth-effect heat exchanger 6, and a third separator 7. The tubes of the first-effect, second-effect, and third-effect heat exchangers are each equipped with a circulation loop. The extraction water to be concentrated enters from the tubes of the first-effect heat exchanger, is concentrated through circulation heat exchange, then enters the tubes of the second-effect heat exchanger, is further concentrated through circulation heat exchange, and then enters the third-effect heat exchanger, and finally enters the fourth-effect heat exchanger after another circulation heat exchange. The heat exchanger and the third separator are as follows: the steam generated in the tube side of the first-effect heat exchanger enters the first separator for separation, and the gas phase enters the shell side of the second-effect heat exchanger; the steam generated in the tube side of the second-effect heat exchanger and the third-effect heat exchanger enters the second separator for separation, and the separated gas phase and the gas phase separated in the third separator are connected to the spray scrubbing tower 8 and the compressor 9. The compressed steam provides steam for the shell side of the first-effect heat exchanger and the shell side of the third-effect heat exchanger, and the steam in the fourth-effect heat exchanger is external steam; the liquid phase outlet of the third separator is also connected to the concentrate storage tank 10 by a pipeline.

[0019] This invention utilizes a mechanical compression final-effect secondary steam recirculation method in an evaporation and concentration device to compress low-temperature, low-pressure steam into high-temperature, high-pressure steam, which is then used to evaporate and concentrate the extracted water. The reconcentration system leverages the boiling point difference of the concentrate to evaporate water from the concentrate through heating, thereby increasing the concentration of the concentrate.

[0020] In some embodiments, the first-effect heat exchanger, the second-effect heat exchanger, and the third-effect heat exchanger are all falling film heat exchangers. The material concentration after concentration in the first-effect heat exchanger is about 15%, the material concentration after concentration in the second-effect heat exchanger is about 30%, the material concentration after concentration in the third-effect heat exchanger is about 65%, and the material concentration after concentration in the fourth-effect heat exchanger can reach more than 70%.

[0021] In some embodiments, the steam condensate from the shell side of the first-effect, second-effect, and third-effect heat exchangers is connected to a condensate storage tank. The temperature in the condensate storage tank remains relatively high, allowing for further utilization of its heat. Preferably, the outlet of the condensate storage tank is connected to a preheating heat exchanger for preheating the extraction water before it enters the tube side of the first-effect heat exchanger. The temperature of the extraction water from the tank area is approximately 85-92°C and its concentration is approximately 10 wt%. After pressurization, filtration, and multi-stage preheating, it can reach approximately 110°C.

[0022] In some embodiments, the extraction water to be concentrated enters from the top of the tube side of the first-effect heat exchanger, and the bottom outlet is connected to the second-effect heat exchanger via a pipeline, entering from the bottom of its tube side. The tube-side circulation loops of the first-effect, second-effect, and third-effect heat exchangers exit from the bottom outlet of the heat exchanger, pass through pipelines and circulation pumps, and are then transported to the top pipeline inlet. After the circulating material is mixed with the newly fed material, it further exchanges heat with steam in the heat exchanger, causing the liquid to evaporate and vaporize, generating secondary steam.

[0023] In some embodiments, there are multiple compressors. High-power compressors and low-power compressors can be configured, and their operation can be adjusted as needed.

[0024] In some embodiments, the lower part of the spray scrubbing tower is a spray pipe, and the upper part is a packing layer. The gas phase passes through the packing layer and is then led out into the compressor. Through spray scrubbing, impurities and some oligomers are removed.

[0025] In some embodiments, a concentrate transfer tank 11 and a filter 12 are provided between the quadruple-effect heat exchanger and the concentrate storage tank. Solid impurities and oligomers are removed by filtration.

[0026] When using the device of this invention for extract water concentration, the extract water is pressurized by a feed pump, preheated to 110°C through multiple stages of filtration, and enters the first-effect heat exchanger. The concentrated liquid circulating with the first-effect circulation pump enters the tube side of the first-effect heat exchanger, where it is heated and vaporized by compressed steam (117°C, 21.0 t / h) from the compressor in the shell side. The secondary steam from the first effect (approximately 21 t / h, 112°C) is discharged from the top after washing in the first separator and enters the shell side of the second-effect heat exchanger. The extract water concentrate (concentration 15%, 41.5 t / h, 100°C) at the bottom of the first separator reacts with the first-effect heat exchanger... The concentrated liquid at the bottom of the heat exchanger is mixed and then separately transported to the first-effect heat exchanger for continued circulation or to the lower part of the second-effect heat exchanger to enter the tube side. The concentrated liquid at the bottom of the second-effect heat exchanger is pumped into the top of the heat exchanger by the second-effect circulation pump and heated and vaporized by the secondary steam from the first-effect heat exchanger. The secondary steam from the second effect (about 21 t / h, 100°C) enters the second separator and, together with the secondary steam from the third-effect heat exchanger (about 10.833 t / h, 100°C) and the secondary steam from the fourth-effect heat exchanger (about 0.687 t / h, 120°C), is sprayed and washed by the scrubbing tower before entering the compressor inlet for circulation and compression. The caprolactam extract water concentrate (concentration 30%, 20.5t / h, 102℃) at the bottom of the second-effect heat exchanger is respectively pumped to the top circulation of the second-effect heat exchanger, the top of the third-effect heat exchanger, and circulated into the tube side of the heat exchanger by the third-effect circulation pump. It is heated by compressed steam (117℃, 11.57t / h) from the steam compressor in the shell side. The secondary steam from the third-effect heat exchanger enters the second separator. The bottom extract water concentrate (concentration 65%, 9.617t / h, 110℃) is pumped to the inlet of the fourth-effect circulation pump by the falling film circulation pump. It is heated to 120℃ by the 159℃ live steam in the shell side of the fourth-effect heat exchanger. In the third separator, the vapor and liquid are separated. The secondary steam from the fourth-effect heat exchanger enters the gas scrubbing tower. The concentrate from the fourth-effect heat exchanger (concentration 70%, 8.93t / h, 120℃) is pumped to the concentrate storage tank for later use. Steam condensate (114℃, 53.57t / h) from the shell side of the first-effect falling film heat exchanger, second-effect falling film heat exchanger, and third-effect falling film heat exchanger is recovered to the condensate tank, pressurized and preheated to the extraction water of the MVR system, and finally sent to the condensate storage tank in the tank area for recycling.

[0027] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including combining the various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed by the present invention and all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be determined by the appended claims.

Claims

1. A polyamide 6 extraction water evaporation and concentration device, characterized in that: The system includes a first-effect heat exchanger, a first separator, a second-effect heat exchanger, a third-effect heat exchanger, a second separator, a fourth-effect heat exchanger, and a third separator. The tube sides of the first, second, and third-effect heat exchangers are each equipped with a circulation loop. The extract water to be concentrated enters from the tube side of the first-effect heat exchanger, circulates for heat exchange and concentration, then enters the tube side of the second-effect heat exchanger. After further circulation for heat exchange and concentration, it enters the third-effect heat exchanger, and after another circulation for heat exchange, it enters the fourth-effect heat exchanger and the third separator. The steam generated in the tube side of the first-effect heat exchanger enters the first separator for separation, and the gas phase enters the shell side of the second-effect heat exchanger. The steam generated in the tube sides of the second and third-effect heat exchangers enters the second separator for separation. The separated gas phases, along with the gas phase separated in the third separator, are connected to a spray scrubbing tower and a compressor. The compressed steam provides steam for the shell sides of the first and third-effect heat exchangers, while the steam in the fourth-effect heat exchanger is external steam. The liquid phase outlet of the third separator is also connected to a concentrated liquid storage tank via a pipeline.

2. The apparatus according to claim 1, characterized in that: The single-effect heat exchanger, the double-effect heat exchanger, and the triple-effect heat exchanger are all falling film heat exchangers.

3. The apparatus according to claim 1, characterized in that: The steam condensate from the shell side of the first-effect heat exchanger, the second-effect heat exchanger, and the third-effect heat exchanger is connected to a condensate storage tank. The outlet of the condensate storage tank is connected to a preheating heat exchanger to preheat the extraction water before it enters the tube side of the first-effect heat exchanger.

4. The apparatus according to claim 1, characterized in that: The extraction water to be concentrated enters from the top of the tube side of the first-effect heat exchanger, and the bottom outlet is connected to the second-effect heat exchanger via a pipe, entering from the bottom of its tube side.

5. The apparatus according to any one of claims 1 to 4, characterized in that: The compressors mentioned are multiple sets.

6. The apparatus according to any one of claims 1 to 4, characterized in that: The lower part of the spray scrubbing tower is a spray pipe, and the upper part is a packing layer. The gas phase is led out into the compressor after passing through the packing layer.

7. The apparatus according to claim 1, characterized in that: A concentrated liquid transfer tank and a filter are also provided between the four-effect heat exchanger and the concentrated liquid storage tank.

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