Method for treating NMMO solvent recovered in lyocell fiber production process

Abstract

The invention belongs to the field of fiber production, and particularly relates to a method for treating an NMMO (N-methylmorpholine-N-oxide) solvent recovered in a lyocell fiber production process. The method comprises the following steps: a) a recovered NMMO solvent is sequentially subjected to filtration and impurity removal, decoloring by an anion exchanger and metal ion removal by a cation exchanger, and a purified solvent is obtained; b) performing chromaticity detection on the purified solvent, and if a detected chromaticity value is greater than a chromaticity set value, returning the purified solvent to the step a) for circular treatment; and if the detected chromaticity value is less than or equal to the chromaticity set value, evaporating and concentrating the purified solvent. According to the method provided by the invention, the subsequent treatment path of the solvent is optimized according to the chromaticity of the NMMO solvent after cation exchange, and the high-chromaticity solvent after cation exchange is prevented from entering the next evaporation and concentration process.

Description

Technical Field

[0001] This invention belongs to the field of fiber production, and in particular relates to a method for treating NMMO solvent recovered during the production of lyocell fibers. Background Technology

[0002] Lyocell fiber is a solvent-based cellulose fiber, and the solvent used in its production, N-methylmorpholine oxide (NMMO), is a non-toxic and harmless organic solvent. The main lyocell fiber production workshop comprises three sections: dopant spinning, spinning, and solvent recovery. The dilute solvent recovered from the entire production system is collected in the purification section, where it is purified and impurities removed before entering the evaporation section. Therefore, solvent purification is crucial, and further optimization of the purification process is necessary. Summary of the Invention

[0003] In view of this, the object of the present invention is to provide a method for treating NMMO solvent recovered during the production of lyocell fibers, which can effectively reduce the color of the recovered NMMO solvent after treatment.

[0004] This invention provides a method for treating NMMO solvent recovered during the production of lyocell fibers, comprising the following steps:

[0005] a) The recovered NMMO solvent is sequentially filtered to remove impurities, decolorized by an anion exchanger, and removed by a cation exchanger to remove metal ions, resulting in a purified solvent.

[0006] b) Perform colorimetric detection on the purified solvent. If the detected colorimetric value is greater than the set colorimetric value, return the purified solvent to step a) for recycling. If the detected colorimetric value is less than or equal to the set colorimetric value, evaporate and concentrate the purified solvent.

[0007] Preferably, the chromaticity setting value is 250 to 350.

[0008] Preferably, the filter used for filtration and impurity removal is filled with a multi-media filter layer comprising quartz sand and pumice.

[0009] Preferably, the flow rate of the NMMO solvent used for filtration and impurity removal is 80–90 m / s. 3 / h.

[0010] Preferably, the anion exchanger has a dual-chamber structure.

[0011] Preferably, the anion exchange resin filled in the anion exchanger is a styrene-stilbene copolymer with tertiary amine groups.

[0012] Preferably, the flow rate of the NMMO solvent through the anion exchanger is 40–50 m³ / s. 3 / h.

[0013] Preferably, the cation exchanger has a single-chamber structure.

[0014] Preferably, the cation exchange resin filled in the cation exchanger is an acrylic cation exchange resin.

[0015] Preferably, the flow rate of the NMMO solvent through the cation exchanger is 70–80 m³ / s. 3 / h.

[0016] Compared with existing technologies, this invention provides a method for treating NMMO solvent recovered during the production of lyocell fibers, comprising the following steps: a) the recovered NMMO solvent is sequentially filtered for impurities, decolorized using an anion exchanger, and deionized using a cation exchanger to remove metal ions, resulting in purified solvent; b) the purified solvent is subjected to colorimetric detection. If the detected colorimetric value is greater than a set colorimetric value, the purified solvent is returned to step a) for recycling; if the detected colorimetric value is less than or equal to the set colorimetric value, the purified solvent is evaporated and concentrated. The method provided by this invention optimizes the subsequent processing path of the solvent based on the colorimetric properties of the NMMO solvent after cation exchange, preventing high-color-ratio cation-exchange solvent from entering the next evaporation and concentration process. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the solvent processing flow provided in an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 are within the scope of protection of the present invention.

[0020] This invention provides a method for treating NMMO solvent recovered during the production of lyocell fibers, comprising the following steps:

[0021] a) The recovered NMMO solvent is sequentially filtered to remove impurities, decolorized by an anion exchanger, and removed by a cation exchanger to remove metal ions, resulting in a purified solvent.

[0022] b) Perform colorimetric detection on the purified solvent. If the detected colorimetric value is greater than the set colorimetric value, return the purified solvent to step a) for recycling. If the detected colorimetric value is less than or equal to the set colorimetric value, evaporate and concentrate the purified solvent.

[0023] In the method provided by the present invention, the original color of the NMMO solvent is preferably 600 to 700.

[0024] In the method provided by this invention, the filter layer filled in the filter used for filtration and impurity removal is preferably a multi-media filter layer comprising quartz sand and pumice; the flow rate of the NMMO solvent for filtration and impurity removal is preferably 80-90 m / s. 3 / h, specifically 80m 3 / h、81m 3 / h、82m 3 / h、83m 3 / h、84m 3 / h、85m 3 / h、86m 3 / h、87m 3 / h、88m 3 / h、89m 3 / h or 90m 3 / h; the residence time of the NMMO solvent in the filter is preferably 5 to 15 min, specifically 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min or 15 min.

[0025] In the method provided by this invention, the anion exchanger is preferably a two-chamber structure; the anion exchange resin packed in the anion exchanger is preferably a styrene-stilbene copolymer with tertiary amine groups (-N(CH3)2). This resin material has weak basicity and can more effectively exchange chromophores with weak reducing properties, resulting in better decolorization of the solvent. In this invention, the flow rate of the NMMO solvent through the anion exchanger is preferably 40-50 m / s. 3 / h, specifically 40m 3 / h、41m 3 / h、42m 3 / h、43m 3 / h、44m 3 / h, 45m 3 / h、46m 3 / h、47m 3 / h、48m 3 / h、49m 3 / h or 50m 3 / h; the residence time of the NMMO solvent in the anion exchanger is preferably 30-50 min, specifically 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min, 40 min, 41 min, 42 min, 43 min, 44 min, 45 min, 46 min, 47 min, 48 min, 49 min, or 50 min.

[0026] In the method provided by this invention, the cation exchanger is preferably a single-chamber structure; the cation exchange resin filled in the cation exchanger is preferably an acrylic cation exchange resin, which contains a large number of strong acid groups, such as sulfonic acid groups (-SO3H), which readily dissociate into H+ in solution. + After the resin dissociates, it can adsorb and bind metal cations in the solvent, thereby removing metal ions from the solvent. In this invention, the flow rate of the NMMO solvent through the cation exchanger is 70–80 m / s. 3 / h, specifically 70m 3 / h、71m 3 / h、72m 3 / h、73m 3 / h、74m 3 / h、75m 3 / h、76m 3 / h、77m 3 / h、78m 3 / h、79m 3 / h or 80m 3 / h; the residence time of the NMMO solvent in the cation exchanger is preferably 10 to 20 min, specifically 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min.

[0027] In the method provided by the present invention, the chromaticity setting value is preferably 250 to 350, specifically 250, 260, 270, 280, 290, 300, 310, 320, 330, 340 or 350.

[0028] In the method provided by the present invention, if the detected chromaticity value is greater than the chromaticity set value, the purified solvent is preferably first entered into the concentration tank and then returned to step a) for recycling.

[0029] In the method provided by the present invention, if the detected color value is less than or equal to the color set value, the purified solvent preferably enters the evaporation storage tank first, and then undergoes evaporation and concentration.

[0030] The method provided by this invention optimizes the subsequent processing path of the solvent based on the color of the NMMO solvent after cation exchange, thereby preventing high-color post-cation exchange solvent from entering the next evaporation and concentration process.

[0031] For clarity, the following examples will be used to provide a detailed description.

[0032] Example 1

[0033] This embodiment provides a method for treating NMMO solvent recovered during the production of lyocell fibers, such as... Figure 1 As shown, it specifically includes:

[0034] The recovered NMMO solvent is sent to the dilute solvent tank in the tank area, and then to the filter for impurity removal. The filtered solvent is then sent to the anion exchanger (anion bed) for decolorization, and the decolorized solvent is then sent to the cation exchanger (cation bed) to remove metal ions. When the solvent comes into contact with the resin of the cation exchanger, a reaction occurs, causing the color to increase. A portion of the high-color solvent is discharged into the concentration tank and then sent back to the dilute solvent tank in the tank area for recycling. Once the effluent from the cation exchanger meets the requirements, it is sent to the evaporation storage tank, where the solvent is finally evaporated and concentrated.

[0035] In this embodiment, the original color of the NMMO solvent is 600–700; the filter layer packed in the filter is a multi-media filter layer including quartz sand and pumice; and the solvent flow rate through the filter is 80 m / s. 3 The solvent residence time in the filter is 11 min / h; the anion exchanger is a two-chamber structure, filled with styrene-stilbene copolymer containing tertiary amine groups, and the solvent flow rate through the anion exchanger is 50 m / h. 3 The solvent residence time in the anion exchanger is 35 min / h; the cation exchanger is a single-chamber structure, filled with acrylic cation exchange resin, and the solvent flow rate through the cation exchanger is 70 m / h. 3 / h, the residence time of the solvent in the cation exchanger is 16min; the color of the effluent from the cation exchanger that meets the requirements is set to 300;

[0036] In this embodiment, the solvent residence time is increased by increasing the flow rate of the solvent through the anion exchanger; after the cation exchanger has discharged liquid into the concentration tank for a total of 10 hours, the color of the liquid output from the cation exchanger decreases to 300. At this time, the circuit is switched to send the liquid output from the cation exchanger into the evaporation storage tank.

[0037] Example 2

[0038] This embodiment provides a method for treating NMMO solvent recovered during the production of lyocell fibers, such as... Figure 1As shown, it specifically includes:

[0039] The recovered NMMO solvent is sent to the dilute solvent tank in the tank area, and then to the filter for impurity removal. The filtered solvent is then sent to the anion exchanger (anion bed) for decolorization, and the decolorized solvent is then sent to the cation exchanger (cation bed) to remove metal ions. When the solvent comes into contact with the resin of the cation exchanger, a reaction occurs, causing the color to increase. A portion of the high-color solvent is discharged into the concentration tank and then sent back to the dilute solvent tank in the tank area for recycling. Once the effluent from the cation exchanger meets the requirements, it is sent to the evaporation storage tank, where the solvent is finally evaporated and concentrated.

[0040] In this embodiment, the original color of the NMMO solvent is 600–700; the filter layer packed in the filter is a multi-media filter layer including quartz sand and pumice; and the solvent flow rate through the filter is 84 m / s. 3 The solvent residence time in the filter is 10 min / h; the anion exchanger is a two-chamber structure, filled with styrene-stilbene copolymer containing tertiary amine groups, and the solvent flow rate through the anion exchanger is 44 m / h. 3 The solvent residence time in the anion exchanger is 41 min / h; the cation exchanger is a single-chamber structure, filled with acrylic cation exchange resin, and the solvent flow rate through the cation exchanger is 72 m / h. 3 / h, the residence time of the solvent in the cation exchanger is 16min; the color of the effluent from the cation exchanger that meets the requirements is set to 300;

[0041] In this embodiment, the solvent residence time is increased by increasing the flow rate of the solvent through the anion exchanger; after the cation exchanger has discharged liquid into the concentration tank for a total of 10 hours, the color of the liquid output from the cation exchanger decreases to 300. At this time, the circuit is switched to send the liquid output from the cation exchanger into the evaporation storage tank.

[0042] Example 3

[0043] This embodiment provides a method for treating NMMO solvent recovered during the production of lyocell fibers, such as... Figure 1 As shown, it specifically includes:

[0044] The recovered NMMO solvent is sent to the dilute solvent tank in the tank area, and then to the filter for impurity removal. The filtered solvent is then sent to the anion exchanger (anion bed) for decolorization, and the decolorized solvent is then sent to the cation exchanger (cation bed) to remove metal ions. When the solvent comes into contact with the resin of the cation exchanger, a reaction occurs, causing the color to increase. A portion of the high-color solvent is discharged into the concentration tank and then sent back to the dilute solvent tank in the tank area for recycling. Once the effluent from the cation exchanger meets the requirements, it is sent to the evaporation storage tank, where the solvent is finally evaporated and concentrated.

[0045] In this embodiment, the original color of the NMMO solvent is 600–700; the filter layer packed in the filter is a multi-media filter layer including quartz sand and pumice; and the solvent flow rate through the filter is 90 m / s. 3 The solvent residence time in the filter is 9 min / h; the anion exchanger is a two-chamber structure, filled with styrene-stilbene copolymer containing tertiary amine groups, and the solvent flow rate through the anion exchanger is 40 m / h. 3 The solvent residence time in the anion exchanger is 46 min / h; the cation exchanger is a single-chamber structure, filled with acrylic cation exchange resin, and the solvent flow rate through the cation exchanger is 80 m / h. 3 / h, the residence time of the solvent in the cation exchanger is 14min; the color of the effluent from the cation exchanger that meets the requirements is set to 300;

[0046] In this embodiment, the solvent residence time is increased by increasing the flow rate of the solvent through the anion exchanger; after the cation exchanger has discharged liquid into the concentration tank for a total of 6 hours, the color of the liquid output from the cation exchanger decreases to 300. At this time, the circuit is switched to send the liquid output from the cation exchanger into the evaporation storage tank.

[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for treating NMMO solvent recovered during the production of lyocell fibers, characterized in that, Includes the following steps: a) The recovered NMMO solvent is sequentially filtered to remove impurities, decolorized by an anion exchanger, and removed by a cation exchanger to remove metal ions, resulting in purified solvent. b) Perform colorimetric detection on the purified solvent. If the detected colorimetric value is greater than the set colorimetric value, return the purified solvent to step a) for recycling. If the detected colorimetric value is less than or equal to the set colorimetric value, evaporate and concentrate the purified solvent.

2. The method according to claim 1, characterized in that, The chromaticity setting value is 250 to 350.

3. The method according to claim 1, characterized in that, The filter used for filtration and impurity removal is filled with a multi-media filter layer consisting of quartz sand and pumice.

4. The method according to claim 1, characterized in that, The flow rate for filtration and impurity removal of the NMMO solvent is 80–90 m / s. 3 / h.

5. The method according to claim 1, characterized in that, The anion exchanger has a dual-chamber structure.

6. The method according to claim 1, characterized in that, The anion exchange resin filled in the anion exchanger is a styrene-stilbene copolymer with tertiary amine groups.

7. The method according to claim 1, characterized in that, The NMMO solvent flows through the anion exchanger at a rate of 40–50 m / s. 3 / h.

8. The method according to claim 1, characterized in that, The cation exchanger has a single-chamber structure.

9. The method according to claim 1, characterized in that, The cation exchanger is filled with an acrylic cation exchange resin.

10. The method according to claim 1, characterized in that, The NMMO solvent flows through the cation exchanger at a rate of 70–80 m / s. 3 / h.

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