A low-concentration caprolactam aqueous solution recovery device

Abstract

This invention relates to the field of caprolactam recovery technology, specifically to a low-concentration caprolactam aqueous solution recovery device. The device comprises a wastewater storage tank followed by a pre-filter, a fine filter, a first-stage security filter, a first- and second-stage security filters, an RO reverse osmosis system, a second-stage security filter, a second- and second-stage security filters, an NF nanofiltration system, and a recovered water storage tank. This invention centralizes the treatment of dispersed low-concentration water, combining nanofiltration (NF) and reverse osmosis (RO) through multi-stage filtration. This selectively retains caprolactam (CPL) at the molecular level, achieving a concentration of 7%–10%, reducing resource waste, improving overall recovery efficiency, and reducing COD from 25,000–35,000 mg / L to 2–5 mg / L after wastewater treatment, thus reducing wastewater treatment costs.

Description

Technical Field

[0001] This utility model relates to the field of caprolactam recovery technology, specifically to a device for recovering low-concentration caprolactam aqueous solution. Background Technology

[0002] Caprolactam (CPL), as the core raw material for the synthesis of nylon 6 chips, directly determines the spinnability, strength, and finished product quality of nylon 6 fibers due to its quality and stability. In recent years, with the rapid development of my country's textile, automotive lightweighting, and electronics industries, the demand for nylon 6 has continued to rise, driving the rapid expansion of CPL production capacity. From the downstream demand side, the annual production capacity of nylon 6 chips in China has reached 9.38 million tons. During its production process, the polymerization pelleting water system and purification system will generate low-concentration aqueous solutions with a CPL content of 2% to 6%. Based on the industry average, the annual total amount of such wastewater is approximately 1.126 million to 1.219 million tons, of which it contains 23,000 to 73,000 tons of CPL resources per year. The need for resource recovery is urgent. Improper treatment of such wastewater will not only waste resources but may also lead to environmental risks or become a key bottleneck restricting the sustainable development of enterprises.

[0003] Currently, the mainstream treatment methods for low-concentration CPL aqueous solutions in the industry fall into two categories: one is direct discharge into the wastewater system, which not only causes a large loss of CPL, but its residue also increases the COD load of wastewater treatment plants; the other is evaporation and concentration to recover CPL. Although CPL is recovered, evaporating low-concentration water results in a large amount of steam waste. Both methods face the dual dilemma of "poor economic efficiency" and "high environmental risks," and there is an urgent need for innovative technologies to achieve efficient resource recovery and cost reduction and carbon reduction.

[0004] Therefore, there is a need for an economical, environmentally friendly, and energy-efficient caprolactam recovery device. Utility Model Content

[0005] The purpose of this invention is to provide a device for recovering low-concentration caprolactam aqueous solution.

[0006] This utility model provides the following technical solution:

[0007] This utility model proposes a low-concentration caprolactam aqueous solution recovery device, including a wastewater storage tank, a pre-filter, a fine filter, a first-stage security filter, a first-stage security filter, a second-stage security filter, an RO reverse osmosis device, a second-stage security filter, a second-stage security filter, an NF nanofiltration device, and a recovered water storage tank.

[0008] The outlet of the wastewater storage tank is connected to the inlet of the pre-filter, the outlet of the pre-filter is connected to the inlet of the fine filter, the outlet of the fine filter is connected to the inlet of the first primary security filter, the outlet of the first primary security filter is connected to the inlet of the first secondary security filter, the outlet of the first secondary security filter is connected to the inlet of the RO reverse osmosis unit, the outlet of the RO reverse osmosis unit is connected to the inlet of the second primary security filter, the outlet of the second primary security filter is connected to the inlet of the second secondary security filter, the outlet of the second secondary security filter is connected to the inlet of the NF nanofiltration unit, and the outlet of the NF nanofiltration unit is connected to the inlet of the recycled water storage tank.

[0009] Furthermore, the pre-filter has a precision of 9-11 μm and a filter cloth area of ​​29-30 m². 3 The precision filter has an accuracy of 5-6 μm and a filter cloth area of ​​49-50 m². 3 .

[0010] Furthermore, both the first-stage security filter and the second-stage security filter have a filter accuracy of 3-4 μm and a filter cloth area of ​​10-11 m². 3 .

[0011] Furthermore, both the first and second secondary security filters have a filter accuracy of 1-2 μm and a filter cloth area of ​​10-11 m². 3 .

[0012] Compared with existing technologies, this invention centralizes the treatment of dispersed low-concentration water by combining nanofiltration (NF) and reverse osmosis (RO). Through multi-stage filtration, CPL is selectively retained at the molecular level, achieving a concentration of 7% to 10%, reducing resource waste, improving overall recovery efficiency, and reducing COD from 25,000 to 35,000 mg / L to 2 to 5 mg / L after wastewater treatment, thus reducing wastewater treatment costs. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the connection relationship of this utility model.

[0014] In the diagram, 1-wastewater storage tank, 2-pre-filter, 3-fine filter, 4-first-stage security filter, 5-first-second-stage security filter, 6-RO reverse osmosis equipment, 7-second-stage security filter, 8-second-second-stage security filter, 9-NF nanofiltration equipment, 10-recycled water storage tank. Detailed Implementation

[0015] The following is in conjunction with the appendix Figure 1 The present invention will be further described below.

[0016] In one embodiment of this utility model, a low-concentration caprolactam aqueous solution recovery device includes a wastewater storage tank 1, a pre-filter 2, a fine filter 3, a first-stage security filter 4, a first-stage security filter 5, an RO reverse osmosis device 6, a second-stage security filter 7, a second-stage security filter 8, an NF nanofiltration device 9, and a recovered water storage tank 10.

[0017] The outlet of the wastewater storage tank 1 is connected to the inlet of the pre-filter 2, the outlet of the pre-filter 2 is connected to the inlet of the fine filter 3, the outlet of the fine filter 3 is connected to the inlet of the first primary security filter 4, the outlet of the first primary security filter 4 is connected to the inlet of the first secondary security filter 5, the outlet of the first secondary security filter 5 is connected to the inlet of the RO reverse osmosis device 6, the outlet of the RO reverse osmosis device 6 is connected to the inlet of the second primary security filter 7, the outlet of the second primary security filter 7 is connected to the inlet of the second secondary security filter 8, the outlet of the second secondary security filter 8 is connected to the inlet of the NF nanofiltration device 9, and the outlet of the NF nanofiltration device 9 is connected to the inlet of the recycled water storage tank 10.

[0018] In practical applications, the wastewater in wastewater storage tank 1 passes through pre-filter 2, fine filter 3, first-stage security filter 4, first-stage and second-stage security filter 5, RO reverse osmosis equipment 6, second-stage security filter 7, second-stage and second-stage security filter 8, and NF nanofiltration equipment 9 in sequence. The CPL concentration can reach 7%-10%, and the COD of the treated wastewater can be reduced from 25,000-35,000 mg / L to 2-5 mg / L.

[0019] In one embodiment of this utility model, after filtration by the first secondary security filter 5, the pressure is stabilized to 2.0-2.5 MPa by an external delivery pump and delivered to the RO reverse osmosis equipment 6; after filtration by the second secondary security filter 8, the pressure is stabilized to 2.0-2.5 MPa by an external delivery pump and delivered to the NF nanofiltration equipment 9; this allows the RO membrane and NF membrane to operate steadily under appropriate pressure, avoiding damage caused by high-pressure impact and extending their service life.

[0020] In one embodiment of this utility model, the RO reverse osmosis equipment adopts model HP-CPL-8-95, and the NF nanofiltration equipment adopts model HP-CPL-8-90.

[0021] In one embodiment of this utility model, the pre-filter 2 has a precision of 9-11 μm and a filter cloth area of ​​29-30 m². 3 The precision of the fine filter 3 is 5-6 μm, and the filter cloth area is 49-50 m². 3 The pre-filter removes large impurities to prevent the fine filter element from clogging.

[0022] In one embodiment of this utility model, the first-stage security filter 4 and the second-stage security filter 7 both have a precision of 3-4 μm and a filter cloth area of ​​10-11 m². 3 .

[0023] In one embodiment of this utility model, the first secondary security filter 5 and the second secondary security filter 8 both have a precision of 1-2 μm and a filter cloth area of ​​10-11 m². 3 .

[0024] Before performing RO reverse osmosis or NF nanofiltration, the membranes are first passed through a primary security filter and a secondary security filter to prevent clogging, scratches, or contamination of the RO and NF membranes, thereby extending their lifespan and reducing maintenance and operating costs.

[0025] In practical applications, wastewater in the wastewater storage tank passes through a pre-filter, a fine filter, a first-stage security filter, a first-stage security filter, a second-stage security filter, an RO reverse osmosis device, a second-stage security filter, a second-stage security filter, and an NF nanofiltration device in sequence. The concentration of CPL in the collected recovery liquid can reach 7%-10%, and the COD of the treated wastewater can be reduced from 25,000-35,000 mg / L to 2-5 mg / L.

[0026] The embodiments of this utility model are given for the purpose of illustration and description. Although embodiments of this utility model have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this utility model. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this utility model.

Claims

1. A device for recovering low-concentration caprolactam aqueous solution, characterized in that: This includes wastewater storage tanks, pre-filters, fine filters, primary and secondary security filters, RO reverse osmosis equipment, secondary and tertiary security filters, NF nanofiltration equipment, and recycled water storage tanks. The outlet of the wastewater storage tank is connected to the inlet of the pre-filter, the outlet of the pre-filter is connected to the inlet of the fine filter, the outlet of the fine filter is connected to the inlet of the first primary security filter, the outlet of the first primary security filter is connected to the inlet of the first secondary security filter, the outlet of the first secondary security filter is connected to the inlet of the RO reverse osmosis unit, the outlet of the RO reverse osmosis unit is connected to the inlet of the second primary security filter, the outlet of the second primary security filter is connected to the inlet of the second secondary security filter, the outlet of the second secondary security filter is connected to the inlet of the NF nanofiltration unit, and the outlet of the NF nanofiltration unit is connected to the inlet of the recycled water storage tank.

2. The low-concentration caprolactam aqueous solution recovery device according to claim 1, characterized in that: The pre-filter has a precision of 9-11 μm and a filter cloth area of ​​29-30 m². 3 The precision filter has an accuracy of 5-6 μm and a filter cloth area of ​​49-50 m². 3 .

3. The low-concentration caprolactam aqueous solution recovery device according to claim 1, characterized in that: Both the first-stage and second-stage security filters have a filter accuracy of 3-4 μm and a filter cloth area of ​​10-11 m². 3 .

4. The low-concentration caprolactam aqueous solution recovery device according to claim 1, characterized in that: Both the first and second secondary security filters have a precision of 1-2 μm and a filter cloth area of ​​10-11 m². 3 .

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