A method for modifying a fiber powder for a powder filter

Abstract

The present disclosure provides a modification method of fiber powder for powder filter, belonging to the technical field of condensate water fine treatment. The modification method comprises: adding N,N-dimethylformamide and 1-hexanol into the first fiber powder, then adding urea-choline chloride, and subsequently adding NaOH solution for heating to perform cationization modification, and then cleaning to obtain the first modified fiber powder; mixing the first modified fiber powder with a cation resin to obtain a first fiber powder sample; adding a sodium dodecyl sulfonate aqueous solution into the second fiber powder for oscillation to perform anionization modification, and then cleaning to obtain the second modified fiber powder; mixing the second modified fiber powder with an anion resin to obtain a second fiber powder sample; and mixing the first fiber powder sample and the second fiber powder sample, stirring and then standing for treatment. The method can enhance the interaction between the fiber powder and the powder resin by changing the surface charge of the fiber powder, thereby greatly improving the sedimentation volume, and further improving the film laying performance of the powder resin and the fiber powder.

Description

Technical Field

[0001] This disclosure belongs to the field of condensate polishing technology, specifically relating to a method for modifying fiber powder for powder filters. Background Technology

[0002] In condensate polishing systems, powder-coated filters are an important type of condensate treatment equipment. Their working principle involves forming a uniform and dense layer of powdered resin and fiber powder (often called a "powder membrane") on the surface of the filter element. Through physical retention, adsorption, and ion exchange, this layer efficiently removes suspended solids, colloids, and ionic impurities from the condensate, thereby ensuring water vapor quality and guaranteeing the safe and stable operation of the generator set. The core filter media of this equipment include powdered anion exchange resin, powdered cation exchange resin, and fiber powder. The core filter media mainly consist of powdered resin and fiber powder. The fiber powder primarily functions to increase the membrane's elasticity and act as a bridging agent to prevent the membrane layer from breaking during operation. Its performance directly affects the membrane laying quality, operating cycle, and effluent quality of the powder-coated filter.

[0003] Currently, a crucial indicator for evaluating the performance of fiber powder is the static settling volume of the mixed flocs formed with it and the powdered resin. This indicator directly reflects the interaction force between the fiber powder and resin particles, as well as the flocculation and settling characteristics of the mixed system. According to T / CSEE 0453.2-2024 "Operation and Maintenance Guidelines for Condensate Polishing Systems in Power Plants Part 2: Powder Cover Filters," the settling volume of 40g of powdered resin and 15g of fiber powder should be no less than 400mL, which is a basic requirement to ensure membrane coating performance meets standards. However, the settling performance of domestically produced fiber powder is often poor, which may lead to poor membrane coating effect and membrane rupture during the operation of powder filters, thereby affecting water quality and threatening unit safety. Furthermore, the traditional mixing process of powdered resin and fiber powder usually involves mixing pre-prepared powdered anion and cation resins, and then physically mixing them with unmodified fiber powder before adding them to the membrane coating system. However, this approach ignores the critical influence of charge matching on the stability of the mixed system. Anionic and cationic resins and fiber powder may carry different charges on their surfaces. Mixing them at once may lead to charge neutralization or shielding effects, which may weaken the effective interaction between the fiber powder and the corresponding charged resin, making it difficult to form a mixed flocculant with stable structure and excellent settling performance.

[0004] Therefore, there is an urgent need to develop a new method that can effectively improve the performance of fiber powder and optimize its charge matching and mixing process with powder resin, so as to solve the problems of poor settling performance of existing domestic fiber powder and unsatisfactory effect of traditional mixing process, thereby improving the overall operating efficiency and reliability of powder-coated filters. Summary of the Invention

[0005] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a method for modifying fiber powder for powder filters.

[0006] This disclosure provides a method for modifying fiber powder for powder filters, comprising: adding N,N-dimethylformamide and 1-hexanol to a first fiber powder, then adding urea-choline chloride, followed by adding NaOH solution and heating to cationize the cellulose, and then washing to obtain the first modified fiber powder; The first modified fiber powder was mixed with cation exchange resin to obtain the first fiber powder sample; Sodium dodecyl sulfonate aqueous solution was added to the second fiber powder and shaken to anionize and modify the cellulose. After washing, the second modified fiber powder was obtained. The second modified fiber powder was mixed with anionic resin to obtain a second fiber powder sample; The first fiber powder sample and the second fiber powder sample were mixed, stirred, and then allowed to stand.

[0007] Optionally, in the urea-choline chloride mixture, the molar ratio of urea to choline chloride should be 1:(1-5).

[0008] Optionally, the concentration of the NaOH solution is 2-10%.

[0009] Optionally, the temperature for cationizing cellulose is 80-90℃ and the time is 8-16h. The cation-modified first fiber powder was cleaned with ultrapure water under ultrasonic conditions for 5-15 minutes, and the content ratio of the first fiber powder to the ultrapure water was 1g:(10-100)mL.

[0010] Optionally, the concentration of the aqueous solution of sodium dodecyl sulfonate is 5-15 mM.

[0011] Optionally, the mass-to-volume ratio of the second fiber powder to the sodium dodecyl sulfonate aqueous solution is 1 g:(10-100) mL.

[0012] Optionally, the temperature for anionization modification of cellulose is room temperature to 50°C, and the time is 20-40 minutes. The cation-modified second fiber powder was cleaned with ultrapure water under ultrasonic conditions for 5-15 minutes. The content ratio of the second fiber powder to the ultrapure water was 1g:(10-100)mL.

[0013] Optionally, the ratio of the cationic modified first fiber powder to the cationized resin is 3:8; The ratio of the anionized modified second fiber powder to the anionized resin is 3:8.

[0014] Optionally, the contents of the cationic modified first fiber powder and the anionic modified second fiber powder are equal; The content of the cation resin and the anion resin are equal.

[0015] Optionally, the stirring time after mixing the first fiber powder sample and the second fiber powder sample is 1 min to 10 min, and the standing time is 15 min to 30 min.

[0016] This disclosure discloses a method for modifying fiber powder for powder filters, comprising: adding N,N-dimethylformamide and 1-hexanol to a first fiber powder, then adding urea-choline chloride, followed by adding NaOH solution and heating to cationize the cellulose, and washing to obtain a first modified fiber powder; mixing the first modified fiber powder with a cation exchange resin to obtain a first fiber powder sample; adding sodium dodecyl sulfonate aqueous solution to a second fiber powder and shaking to anionize the cellulose, and washing to obtain a second modified fiber powder; mixing the second modified fiber powder with an anion exchange resin to obtain a second fiber powder sample; mixing the first fiber powder sample and the second fiber powder sample, stirring, and then allowing to stand. This method can enhance the interaction between the fiber powder and the powder resin by changing the surface charge of the fiber powder, thereby greatly increasing its settling volume and improving the film-forming performance of the powder resin and the fiber powder. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a method for modifying fiber powder for powder filters according to a specific embodiment of this disclosure. Figure 2 This is a schematic diagram showing the sedimentation results of the resin and fiber powder in Embodiment 1 of this disclosure; Figure 3 This is a schematic diagram showing the sedimentation results of the resin and fiber powder in Comparative Example 1 of this disclosure. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0019] As shown in Figure 1, this disclosure provides a method S100 for modifying fiber powder for powder filters, specifically including the following steps S110~S150: S110. Add N,N-dimethylformamide (DMF) and 1-hexanol to the first fiber powder to ensure uniform dispersion of the fiber powder, then add urea-choline chloride, followed by adding NaOH solution and heating to cationize and modify the cellulose. Filter, discard the filtrate, and then wash to obtain the first modified fiber powder.

[0020] In step S110, the molar ratio of urea to choline chloride in the urea-choline chloride system should be 1:(1-5). This component helps to promote the uniform dispersion of fiber powder in the urea-choline chloride system, ensures that the modification reaction proceeds uniformly on the fiber surface, and avoids agglomeration.

[0021] In step S110, the concentration of the NaOH solution is 2-10%, providing an alkaline environment, which is a necessary condition for the cationization reaction of cellulose. This concentration range ensures sufficient reaction kinetics and avoids excessive degradation of cellulose by strong alkali.

[0022] In step S110, the temperature for cationization modification of cellulose is 80-90℃, and the time is 8-16h.

[0023] In step S110, the cleaning substance should be ultrapure water, and the cleaning method should be to add the modified first fiber powder to ultrapure water, sonicate it, filter it to remove the ultrapure water, dry the fiber powder, sonicate it for 5-15 minutes, and the ratio of the first fiber powder to ultrapure water is 1g:(10-100)mL, thereby removing the added modified substance and reducing the leaching of the fiber powder.

[0024] This embodiment utilizes a eutectic solvent system to chemically react a portion of fiber powder under alkaline conditions, introducing positively charged groups onto its surface to give it cationic properties.

[0025] S120. The first modified fiber powder is mixed with the cation resin while stirring to obtain the first fiber powder sample.

[0026] In step S120, the content ratio of the first modified fiber powder to the cation resin is 3:8. For example, the first modified fiber powder is preferably 7.5g and the cation resin is preferably 20g.

[0027] S130. Add sodium dodecyl sulfonate (SLS) aqueous solution to the second fiber powder and shake to anionize and modify the cellulose. Filter, discard the filtrate, and wash to obtain the second modified fiber powder.

[0028] In step S130, the concentration of the sodium dodecyl sulfonate aqueous solution is 5-15 mM.

[0029] In step S130, the mass-to-volume ratio of the second fiber powder to the sodium dodecyl sulfonate aqueous solution is 1 g:(10-100) mL.

[0030] In step S130, the temperature for anionization modification of cellulose is room temperature - 50°C, and the time is 20-40 min. It should be noted that oscillation should be maintained during the modification process to avoid damaging the SLS structure.

[0031] In step S130, the cleaning substance should be ultrapure water, and the cleaning method should be to add the modified second fiber powder to ultrapure water, sonicate it, filter it to remove the ultrapure water, dry the fiber powder, sonicate it for 5-15 minutes, and the ratio of the second fiber powder to ultrapure water is 1g:(10-100)mL, thereby removing the added modified substance and reducing the leaching of the fiber powder.

[0032] In this embodiment, sodium dodecyl sulfonate is used to surface treat another part of the fiber powder. SLS introduces negatively charged sulfonate groups on the surface of the fiber powder through physical adsorption or weak interaction with the hydroxyl groups on the fiber surface, giving it anionic properties.

[0033] S140. Mix the second modified fiber powder with the anion resin while stirring to obtain a second fiber powder sample.

[0034] In step S140, the content ratio of the second modified fiber powder to the anion resin is 3:8. For example, the second modified fiber powder is preferably 7.5g and the anion resin is preferably 20g.

[0035] It should be understood that the second modified fiber powder has the same content as the first modified fiber powder, and the cation resin has the same content as the anion resin. That is to say, the fiber powder is divided into two parts, one part is used for cationic modification treatment, and the other part is used for anionic modification treatment. Then the two parts of modified fiber powder are mixed with the same mass of resin.

[0036] S150. Mix the first fiber powder sample and the second fiber powder sample, stir, and then let stand.

[0037] In step S150, the first fiber powder sample and the second fiber powder sample are the same, and the stirring time after mixing is 1 min-10 min, and the standing time is 15 min-30 min.

[0038] It should be understood that if all raw materials (anion / cationic resins, unmodified or mixed modified fiber powder) are mixed at once, substances with different charges will immediately undergo electrostatic neutralization, forming small and dense flocs with potentially small settling volumes. Furthermore, the effect of charge interaction is partially shielded, failing to fully utilize the bridging effect of the modified fiber powder. Therefore, this embodiment modifies the fiber powder to match its surface charge characteristics with those of the target resin, forming a premix during the premixing stage. This premix is ​​then further mixed to ensure sufficient contact between the anion / cationic resin-fiber powder complex, allowing the opposite charges to attract and bridge, ultimately forming the final flocs. Too short a mixing time results in uneven mixing, while too long a time may damage the already formed structure.

[0039] In the method disclosed herein, the fiber powder is treated with a eutectic solvent (DES) system, which can enhance the interaction between the fiber powder and the powdered resin, as well as the interaction between the fiber powders themselves, by changing the surface charge of the fiber powder. This greatly increases the settling volume of the flocs formed by the powdered resin and fiber powder, which helps to improve the film-forming performance of the powdered resin and fiber powder.

[0040] This disclosure provides a method for mixing powdered resin and fiber powder, as well as the mixing sequence of the resin and fiber powder, thereby promoting the interaction between cationic and anionic modified fiber powder and resin materials with the same charge, and avoiding the shielding of charge interaction caused by mixing the filter media all at once.

[0041] The modification method of fiber powder for powder filters will be further explained below with reference to specific embodiments: Example 1 1. Weigh out two portions of fiber powder raw material, each weighing 7.5g. Add the two portions of fiber powder to clean 250mL Erlenmeyer flasks and label them as No. 1 (first fiber powder) and No. 2 (second fiber powder). 2. Add N,N-dimethylformamide (DMF) and 1-hexanol to a conical flask to fully disperse the first fiber powder. Then add urea-choline chloride at a molar ratio of 1:2, followed by adding 6wt% NaOH solution and heating to cationize the cellulose at 50℃ for 30 min. Add the modified fiber powder to ultrapure water, sonicate, filter to remove the ultrapure water, dry the fiber powder, and sonicate for 10 min. The ratio of fiber powder to water is 1 g: 50 mL to obtain the first modified fiber powder. 3. Add 75 mL of 10 mM sodium dodecyl sulfate (SLS) aqueous solution to Erlenmeyer flask No. 2 and shake at room temperature for 30 min to anionize the second fiber powder. Add the modified second fiber powder to ultrapure water, sonicate, filter to remove the ultrapure water, dry the fiber powder, sonicate for 10 min, and the ratio of fiber powder to water is 1 g: 50 mL to obtain the second modified fiber powder. 3. Filter separately and discard the filtrate; 4. Mix 7.5g of the first modified fiber powder with 20g of cation resin under stirring; mix 7.5g of the second modified fiber powder with 20g of anion resin under stirring. 5. Mix the two samples from step 4, stir for 1 minute, and let stand for 15 minutes. The sedimentation volume is 560 mL, and the sedimentation volume and the turbidity of the supernatant are as follows: Figure 2 As shown, the height of the flocs (sludge layer) in the measuring cylinder is very high, corresponding to a value of 560mL, indicating that the flocs have a loose structure and large volume. The liquid above the flocs (supernatant) is relatively clear and transparent, which indicates that the flocs formed by the modified fiber powder and resin have a strong ability to capture and fix impurities, settle thoroughly, and have few suspended fine particles.

[0042] Comparative Example 1 15g of unmodified fiber powder was mixed with 20g of cation exchange resin and 20g of anion exchange resin under stirring. The sedimentation volume was 450mL, and the sedimentation volume and the turbidity of the supernatant were as follows: Figure 3 As shown, the height of the flocs in the graduated cylinder is relatively low, corresponding to a value of 450 mL, indicating that the floc structure is relatively dense and the volume is small. The supernatant shows a slight degree of turbidity, which indicates that the interaction between the unmodified fiber powder and the resin is weak, and the flocs formed have insufficient ability to capture fine particles, and some particles fail to settle.

[0043] In summary, based on the results of Example 1 and Comparative Example 1, the fiber powder modification method proposed in this disclosure can effectively increase the settling volume of the fiber powder, with an increase of up to 24%. According to T / CSEE 0453.2-2024 "Operation and Maintenance Guidelines for Condensate Polishing Systems in Power Plants Part 2: Powder Cover Filters", the settling volume of 40g of powdered resin and 15g of fiber powder should not be less than 400mL. Therefore, the settling volume of the fiber powder modified by this invention far exceeds the standard requirement, indicating that it has excellent membrane-laying performance.

[0044] This disclosure proposes a method for modifying fiber powder for powder filters, which has the following advantages over the prior art: First, this disclosure utilizes a eutectic solvent (DES) system to treat fiber powder, which can enhance the interaction between fiber powder and powdered resin, as well as the interaction between fiber powders, by changing the surface charge of the fiber powder, thereby greatly increasing the settling volume of the flocs formed by the powdered resin and fiber powder, which helps to improve the film-laying performance of the powdered resin and fiber powder. Secondly, this disclosure achieves active design and precise control of charge interaction in the fiber powder-resin system through a process of "first modifying separately, then premixing according to charge matching, and finally merging", avoiding the charge shielding effect of traditional one-time mixing.

[0045] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for modifying a fiber powder for a powder filter, characterized by, The modification method includes: N,N-dimethylformamide and 1-hexanol were added to the first fiber powder, followed by urea-choline chloride, and then NaOH solution was added and heated to carry out cationization modification. After washing, the first modified fiber powder was obtained. The first modified fiber powder was mixed with cation exchange resin to obtain the first fiber powder sample; Sodium dodecyl sulfonate aqueous solution was added to the second fiber powder and shaken to perform anionization modification. After washing, the second modified fiber powder was obtained. The second modified fiber powder was mixed with anionic resin to obtain a second fiber powder sample; The first fiber powder sample and the second fiber powder sample were mixed, stirred, and then allowed to stand.

2. The modification method according to claim 1, characterized in that, In the urea-choline chloride mixture, the molar ratio of urea to choline chloride should be 1:(1-5).

3. The modification method of claim 1, wherein, The concentration of the NaOH solution is 2-10%.

4. The modification method of claim 1, wherein, The cationization modification is performed at a temperature of 80-90℃ for 8-16 hours. The cation-modified first fiber powder was cleaned with ultrapure water under ultrasonic conditions for 5-15 minutes, and the content ratio of the first fiber powder to the ultrapure water was 1g:(10-100)mL.

5. The modification method of claim 1, wherein The concentration of the aqueous solution of sodium dodecyl sulfonate is 5-15 mM.

6. The modification method of claim 1, wherein The mass-to-volume ratio of the second fiber powder to the sodium dodecyl sulfonate aqueous solution is 1 g:(10-100) mL.

7. The modification method of claim 1, wherein The anionization modification temperature is room temperature - 50℃, and the time is 20-40 min; The cation-modified second fiber powder was cleaned with ultrapure water under ultrasonic conditions for 5-15 minutes. The content ratio of the second fiber powder to the ultrapure water was 1g:(10-100)mL.

8. The modification method according to claim 1, characterized in that, The content ratio of the first modified fiber powder to the cation exchange resin is 3:8; The content ratio of the second modified fiber powder to the anion resin is 3:

8.

9. The modification method according to claim 1, characterized in that, The contents of the first modified fiber powder and the second modified fiber powder are equal; The content of the cation resin and the anion resin are equal.

10. The modification method according to claim 1, characterized in that, The stirring time after mixing the first fiber powder sample and the second fiber powder sample is 1 min-10 min, and the standing time is 15 min-30 min.

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